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Luangtip, Wasutep. "X-ray studies of ultraluminous X-ray sources." Thesis, Durham University, 2015. http://etheses.dur.ac.uk/11266/.
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Ultraluminous X-ray sources (ULXs) are extra-galactic, non-nuclear point sources, with X-ray luminosities brighter than 10^39 erg s^-1, in excess of the Eddington limit for 10 M_sun black holes. Recent results indicate that the majority of ULXs are stellar remnant black holes accreting material at or above the Eddington rate, rather than sub-Eddington accretion onto intermediate mass black holes. However, precisely how these ULXs accrete material at a super-Eddington rate remains an open question. This thesis focuses on the nature of these system as well as their environments, and attempts to explain physically how the sources operate in this super-critical accretion regime. This work begins with a study of the X-ray spectra of ULXs in very nearby galaxies (D < 5 Mpc). A range of physical models is used to explain the ULX spectra and to interpret the results physically. The outcomes consistently suggest that ULXs are stellar remnant black holes accreting material at or above the Eddington rate. It is demonstrated that the hard spectral component is consistent with emission from the inner radius of an advection-dominated slim accretion disc; the mass of black holes powering ULXs can be constrained from this hard emission, falling in the regime of stellar-mass black hole (~3 - 30 M_sun). Assuming that the soft spectral component represents soft thermal emission from an optically-thick outflowing wind, the size of the wind is constrained to be between ~10^4 – 10^6 R_g. We further explore the nature of ULXs by studying the X-ray spectral evolution of the individual source Holmberg IX X-1 with observed source luminosity. We find that the spectra tend to evolve from relatively flat or two-component spectra in the medium energy band, at lower luminosities, to a spectrum that is distinctly curved and disc-like at the highest luminosities. This spectral variability is consistent with the prediction of super-Eddington accretion models, in which the outflowing wind is expected to be launched from within the photospheric radius; the increase in accretion rate causes the more powerful wind to scatter a higher fraction of hard photons into the line of sight, while those that survive the passage through the wind will be Compton down-scattered to lower energies; these increase and soften the hard spectral component, resulting in a disc-like spectrum peaking at lower energy than the hard component seen at lower luminosity. Furthermore, we find observational evidence that the ULX might precess around its rotational axis, implied by a degree of degeneracy between different spectra observed at the same luminosity. Finally, we study the population of ULXs present in a sample of 17 nearby luminous infrared galaxies (LIRGs). It is found that the LIRGs possess significantly fewer ULXs per unit star formation rate than nearby normal galaxies, by a factor of about 10. We argue that part of the deficit could be due to the high metallicity environment of the host galaxies suppressing the formation of ULXs, and the lag between star formation starting and the appearance of ULXs; however, the majority of the deficit of ULXs is likely to be due to the high amount of gas and dust in the LIRGs obscuring a large fraction of ULXs.
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Koliopanos, Filippos. "X-ray diagnostics of ultra-compact X-ray binaries." Diss., Ludwig-Maximilians-Universität München, 2015. http://nbn-resolving.de/urn:nbn:de:bvb:19-183488.
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Non-solar composition of the donor star in ultra-compact X-ray binaries (UCXBs) may have a pronounced effect on the fluorescent lines appearing in their spectra due to reprocessing of primary radiation by the accretion disc and the white dwarf surface. We show that the most dramatic and easily observable consequence of the anomalous C/O abundance is the significant, by more than an order of magnitude, attenuation of the Kα line of iron. It is caused by screening of the presence of iron by oxygen - in the C/O-dominated material the main interaction process for an E ~ 7 keV photon is absorption by oxygen rather than by iron, contrary to the solar composition case. Ionization of oxygen at high mass accretion rates adds a luminosity dependence to this behaviour - the iron line is significantly suppressed only at low luminosity, log (LX) < 37-37.5, and should recover its nominal strength at higher luminosity. The increase of the equivalent width of the Kα lines of carbon and oxygen, on the other hand, saturates at rather moderate values. Screening by He is less important, due to its low ionization threshold and because in the accretion disc it is mostly ionized. Consequently, in the case of the He-rich donor, the iron line strength remains close to its nominal value, determined by the iron abundance in the accretion disc. This opens the possibility of constraining the nature of donor stars in UCXBs by means of X-ray spectroscopy with moderate energy resolution.We search for the Fe Kα line in spectra of ultra-compact X-ray binaries (UCXBs). For this purpose we have analysed XMM-Newton observations of five confirmed UCXBs. We find that the object 2S 0918-549 - whose optical spectrum bears tentative signatures of a C/O accretion disc - is devoid of any emission features in the 6-7 keV range, with an upper limit of less than 10 eV for the equivalent width (EW) of the Fe line. 4U 1916-05 - whose optical spectrum is consistent with reflection from a He-rich accretion disc - exhibits a bright broad iron emission line. This behaviour is in agreement with the theoretical predictions presented in Koliopanos et al. Namely, we expect strong suppression of the Fe Kα emission line in spectra originating in moderately bright (log LX less than ≈37.5) UCXBs with C/O- or O/Ne/Mg-rich donors. On the other hand the EW of the Fe line in spectra from UCXBs with He-rich donors is expected to retain its nominal value of ~100 eV. Our analysis also reveals a strong Fe Kα line in the spectrum of 4U 0614+091. This detection points towards a He-rich donor and seems to be at odds with the source's classification as C/O rich. Nevertheless, a He-rich donor would explain the bursting activity reported for this system. Lastly, based on our theoretical predictions, we attribute the lack of a strong iron emission line - in the two remaining UCXB sources in our sample (XTE J1807-294 and 4U 0513-40) - as an indication of a C/O or O/Ne/Mg white dwarf donor. From the upper limits of the Fe Kα line EW in 4U 0513-40, 2S 0918-549 and XTE J1807-294 we obtain a lower limit on the oxygen-to-iron ratio, O/Fe > 10[O/Fe]sol
We detect variability of the Fe Kalpha emission line in the spectrum of X-ray pulsar 4U 1626-67, correlated with changes in its luminosity and in the shape of its pulse profile. Analysis of archival Chandra and RXTE observations revealed the presence of an intrinsically narrow Fe Kalpha emission line in the spectrum obtained during the source's current high luminosity period. However, the line was not present during an XMM- Newton observation seven years earlier, when the source was ~three times fainter. The small intrinsic width of the line, sigma ~ 36 eV, as measured by the high energy grating of Chandra, suggests reflection off the outer accretion disk, at R ~ 1800Rs,assuming a Keplerian disk. This value is consistent with the truncation radius of the disk by the magnetic field of the neutron star, ~ 3 x 10^12 Gauss, known from cyclotron line measurements. Timing analysis of the XMM-Newton and RXTE data revealed a major change in the pulse profile of the source from a distinct double peaked shape during the high luminosity state when the line was present, to a much more complex multi-peak structure during the low luminosity state. We argue that the appearance of the line and the change in the shape of the pulse profile are correlated and are the result of a major change in the emission diagram of the accretion column, from a pencil-beam pattern at low luminosity, to a fan-beam pattern at high luminosity.
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Juett, Adrienne Marie 1976. "X-ray spectroscopy of low-mass X-ray binaries." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28371.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2004.Includes bibliographical references (p. 125-144).
I present high-resolution X-ray grating spectroscopy of neutron stars in low-mass X-ray binaries (LMXBs) using instruments onboard the Chandra X-ray Observatory and the X-ray Multi-Mirror Mission (XMM-Newton). The first part of this thesis concentrates on results from the subset of LMXBs with orbital periods less than an hour, known as ultracompact binaries. Previous low-resolution X-ray spectra of four systems (4U 0614+091, 2S 0918-549, 4U 1543-624, and 4U 1850-087) all contain a broad residual near 0.7 keV which had been attributed to unresolved line emission. I show that this residual is due to an incorrect model of the intervening photoelectric absorption and can be accounted for by allowing a non-standard Ne/O abundance ratio in the intervening material. I propose that there is neon-rich material local to each binary and that the mass donor is a low-mass, neon-rich degenerate dwarf in an ultracompact binary. Follow-up spectroscopy of 2S 0918-549 and 4U 1543-624 with the High Energy Transmission Grating Spectrometer (HETGS) onboard Chandra and the Reflection Grating Spectrometer onboard XMM confirms the excess neutral neon absorption. Interestingly, the Ne/O ratio of 4U 1543-624 varies by a factor of three between the Chandra and XMMobservations, supporting the suggestion that some of the absorption originates local to the binaries. I also present X-ray spectroscopy of another ultracompact binary, the accretion-powered millisecond pulsar XTE J0929-314. No emission or absorption features are found in the high-resolution spectrum of this source, and the neutral absorption edge depths are consistent with the estimated interstellar absorption. The second part of this thesis uses LMXBs as probes of the interstellar medium (ISM).
(cont.) High-resolution X-ray studies of ISM absorption features can provide measurements of the relative abundances and ionization fractions of all the elements from carbon through iron. X- ray studies also probe the ISM on larger scales than is possible in the optical and ultraviolet wavebands. I present high-resolution spectroscopy of the oxygen K-shell ISM absorption edge in seven X-ray binaries using Chandra. The best-fit model consists of two absorption edges and five Gaussian absorption lines and can be explained by the recent theoretical calculations of K-shell absorption by neutral and ionized atomic oxygen. Significant oxygen features from dust or molecular components, suggested in previous studies, are not required by the Chandra spectra. These measurements also probe large-scale properties of the ISM, placing a limit on the velocity dispersion of the neutral lines of less than 200 km s-1 and constraining the interstellar ratio of O II/O I to approximately 0.1 and the ratio of O III/O I to less than 0.1.
by Adrienne Marie Juett.
Ph.D.
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Jonker, Peter Gustaaf. "Probing low-mass X-ray binaries with X-ray timing." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2001. http://dare.uva.nl/document/92302.
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Homan, Jeroen. "X-ray timing studies of low-mass x-ray binaries." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2001. http://dare.uva.nl/document/92942.
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Gavriil, Fotis Panagiotis. "Magnetar-like x-ray bursts from anomalous x-ray pulsars." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100371.
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The leading model for understanding the energetics of anomalous X-ray pulsars (AXPs) is that they are "magnetars"---young, isolated neutron stars powered by the decay of their enormous magnetic fields. The identification of AXPs as magnetars is motivated by the similarity of AXPs to another enigmatic class of sources, the Soft Gamma Repeaters (SGRs). We report on long-term monitoring of AXPs using the Rossi X-ray Timing Explorer (RXTE). We monitor AXPs with RXTE to study their rotational stability, to search for variations in their pulsed flux and pulsed morphology. During our regular monitoring observations we discovered multiple bursts from two AXPs: this was the first time such behavior has been observed from these sources. Prior to our monitoring campaign, the detection of bursts solely from SGRs was the principle difference between AXPs and SGRs. The first detection of AXP bursts came in Fall 2001 when we discovered two SCR-like X-ray bursts from the direction of AXP 1E 1048.1--5937. Due to RXTE's large (1° x 1°) field-of-view we could not unambiguously identify the AXP as the burster. Recently, we detected a third burst from the direction of this source as well as a simultaneous increase in the pulsar's pulsed emission---this clearly identified the AXP as the burster. The most outstanding demonstration of AXP bursting behavior came on 2002 June 18 when AXP 1E 2259+586 underwent a major outburst involving 80 bursts and several changes in the persistent and pulsed emission, including a huge pulsed flux enhancement, a pulse morphology change and a rotational glitch. We also find variations in the persistent emission of AXPs in the absence of an obvious outburst. For example, we discovered two pulsed flux flares from AXP 1E 1048.1--5937. Both flares lasted several months and had well resolved few-week-long rises. The long rise tunes of the flares is a phenomenon not previously reported for this class of object, but has a clear explanation within the context of the magnetar model. All these results imply a close relationship between AXPs and SGRs, which we now believe are both magnetars, and have posed significant challenges to competing models.
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Gladstone, Jeanette Claire. "Optical & X-ray studies of ultraluminous X-ray sources." Thesis, Durham University, 2009. http://etheses.dur.ac.uk/12/.
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Ultraluminous X-ray Sources (ULXs) are point like X-ray sources situated external to the nucleus of their host galaxy, with inferred X-ray luminosities in excess of 10^{39} erg s^{−1} . Although first observed ∼ 30 years ago, these sources are yet to be fully understood. Some have suggested that these fascinating objects may contain intermediate mass black holes, whilst others have proposed they are stellar mass black holes residing in a new extreme accretion state. This thesis works towards the conclusion of this debate, by developing our understanding of these systems and their environments. This work begins with a photometric survey of the optical counterparts of ULXs. The main aim of this survey is to find plausible candidates to gain radial velocity measurements and therefore mass functions of these systems. However, the collation of this sample also provides the opportunity to classify the stellar objects held within these systems. From this work, we find seven good candidates for optical spectroscopic follow-up. Our results also show that many of our sample are consistent with OB type stars, while some contain later type bright giants/supergiants. Possibly our best chance to gain precise measurements of M_{BH}, and settling the debate over the nature of these systems, is by using radial velocity curves of their optical counterparts to calculate a mass function of ULXs. We are currently undertaking a programme to pursue mass function measurements for these systems. To date, we have received the pilot spectra of three optical counterparts. We discuss the progress of this programme to date and perform analysis on both the absorption/emission features and the continuum of these spectra. Initial analysis reveals the presence of the He ii 4686 A line in two of our pilot spectra. This line may be associated with the accretion disc of these systems, and could therefore be used in our pursuit of the mass function. We also find the presence of both low and high ionization lines, with some evidence for shock ionisation, and electron temperature of 7,000 – 10,000 K. This Balmer decrement also indicates that the extinction can be highly variable across ULX field. This combination may suggest a ‘patchy’ environment with separate shock and photoionisation emission regions. While the continuum emission of one of our sample can be explained by either the spectra of an OB star or of a standard accretion disc, the steep slopes of two of our sample indicates non-stellar origins that could represent the optical spectrum of a super-Eddington accretion disc. Finally, this work highlights the need for further observations of these sources in order to unlock their nature. We present results of X-ray spectral variability studies of the ULX population contained within NGC 4485 & 4490. We collate Chandra and XMM-Newton observations of the interacting galaxy pair, to analyse the emission from the six ULXs previously identified, and one additional source observed in the a recent exposure. This provides us with an opportunity to study variability on both short and longer time scales. The spectral variability is generally characterised by a hardening of the source spectra as their luminosities increase. The sources show a variety of long-term light curves; however, short-term (intra-observational) temporal variability is conspicuous by its absence. This survey also reveals the detection of a possible change in accretion state that could be used to gain crude mass estimates of the compact objects. Finally, we explore further the variability of these systems with the aid of two new proprietary observations. Finally, analysis of some of the best quality X-ray spectral data publicly available on these sources has provided the opportunity to explore the nature of these systems. We apply phenomenological models to characterise the spectra of these objects and more physically motivated models in order to explore the physical processes underlying these characteristics. Results show that the spectra of these sources are fundamentally different to that of Galactic X-ray binaries, whilst the application of physical models indicates a more extreme version of the highest known luminosity state, the very high state. We therefore speculate that in observing ULXs we are observing stellar mass black holes residing in a new ‘ultraluminous’ state.
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Plowes, Jonathan Andrew. "Ray optics of X-ray lasers." Thesis, University of York, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296391.
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Ribbing, Carolina. "Microfabrication of miniature x-ray source and x-ray refractive lens." Doctoral thesis, Uppsala University, Department of Materials Science, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3099.
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In several x-ray related areas there is a need for high-precision elements for x-ray generation and focusing. An elegant way of realizing x-ray related elements with high precision and low surface roughness is by the use of microfabrication; a combination of semiconductor processing techniques and miniaturization. Photolithographic patterning of silicon followed by deposition, etching, bonding and replication is used for batchwise fabrication of small well-defined structures. This thesis describes microfabrication of a miniature x-ray source and a refractive x-ray lens. A miniature x-ray source with diamond electrodes has been tested for x-ray fluorescence. Another version of the source has been vacuum encapsulated and run at atmospheric pressure. One-dimensionally focusing saw-tooth refractive x-ray lenses in silicon, epoxy, and diamond have been fabricated and tested in a synchrotron set-up. Sub-micron focal lines and gains of up to 40 were achieved. The conclusion of the thesis is that the use of microfabrication for construction of x-ray related components can not only improve the performance of existing components, but also open up for entirely new application areas.
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Beklen, Elif. "X-ray And Optical Observations Of High Mass X-ray Binaries." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612636/index.pdf.
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In this thesis, X-ray and optical observations of accretion powered pulsars are presented.
By using archival RXTE observations we work on the X-ray spectral and pulse timing
analysis of 4U 1538-52, 4U 1907+09, SMC X-1 to have more detailed information about their orbital and spin parameters.
For 4U 1538-52 and SMC X-1, we determined new orbital epochs.
By using long term pulse history of 4U 1907+09, we were able to work spin-down trend of the system and also calculate the change in the spin-down rate.
Using Fermi/GBM observations we can monitor bright accreting pulsar systems. We are producing long term
histories of pulse frequency and
flux of 20 continuosly monitoring systems.
Adding Swift/BAT observations to GBM observations, for 4U 1626-67, we did reveal the characteristics belong to spin-down trend before and
spin-up behaviour after torque reversal seen in 2008 February.
Two newly discovered IGRJ06074+2205 and IGRJ01583+6713 sources are identified as X-ray binary systems and we found
parameters of them like distance, magnitudes, by using both optical photometric and spectroscopic observations.
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Hooft, Frank van der. "X-ray and optical studies of black-hole X-ray transients." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 1998. http://dare.uva.nl/document/92913.
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Halverson, Clinton. "Characterization of geomaterials with X-ray computed tomography (X-ray CT)." [Ames, Iowa : Iowa State University], 2008.
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Krauss, Miriam Ilana. "X-ray spectroscopy of neutron star low-mass X-ray binaries." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/45408.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2007.Includes bibliographical references (p. 133-150).
In this thesis, I present work spanning a variety of topics relating to neutron star lowmass X-ray binaries (LMXBs) and utilize spectral information from X-ray observations to further our understanding of these sources. First, I give an overview of important X- ray astrophysics relevant to the work I present in subsequent chapters, as well as information about the X-ray observatories from which I obtained my data. In the next three chapters, I consider spectra-both high- and low-resolution--of accretion-powered millisecond X-ray pulsars, a unique and relatively new class of objects. In addition to analysis of the pulsar XTE J1814-338, I compare a broader sample of pulsars with a sample of atoll sources in order to better understand why the latter class do not contain persistently pulsating neutron stars. In particular, I test the hypothesis that pulsations in the atoll sources are suppressed by a high-optical- depth scattering region. Using X-ray color-color diagrams to define a selection criterion based on spectral state, I analyze Rossi X-ray Timing Explorer (RXTE) spectra from all the sources, and use a Comptonization model to obtain measurements of their optical depths. I then discuss efforts to spatially resolve X-ray jets from the accretion-powered millisecond pulsar SAX J1808.4-3658 and the Z source XTE J1701-462. Each was observed by the Chandra X-ray Observatory to produce a high-spatial-resolution image. This work was motivated in part by my analysis of XTE J1814-338, which found an apparent excess of infrared flux which could be attributed to jet emission. Next, I discuss the measured temperatures of thermonuclear X-ray bursts. The detection of line features in these bursts, and hence from the surfaces of neutron stars, has been an important goal for high-resolution X-ray spectroscopy. A measurement of the wavelengths of identified line features would yield a measurement of the neutron star's gravitational redshift, which would help constrain current models for the neutron star equation of state.
(cont.) Although such a measurement has been made for one source, other searches have not been able to repeat this measurement. I consider the effects of burst temperature on the formation of discrete spectral features, using a large sample of bursts observed by the RXTE PCA. Finally, I present analysis of high-resolution Chandra HETG spectra of a sample of Galactic LMXBs. High-resolution spectra are able to resolve line features, such as the prominent Ne and O emission lines in the ultracompact X-ray binary 4U 1626-67. They also allow for more precise measurements of photoelectric absorption edges, which can otherwise hinder the determination of continuum spectral components, particularly in the lower-energy spectral regions.
by Miriam Ilana Krauss.
Ph.D.
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Lindqvist, Malcolm. "Polycapillary X-Ray Optics for Liquid-Metal-Jet X-Ray Tubes." Thesis, Uppsala universitet, Materialfysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-324483.
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Investigating and mapping fundamental processes in nature is a driving force for breakthroughs in research and technology. Doing so, requires knowledge of the smallest scales of the world. One way of performing measurements on these scales is through intense x-ray sources, which have improved greatly over the last decades. By combing these sources with state of the art optics, even higher flux densities can be reached, allowing for faster measurements and ground-breaking discoveries. This study aims to explore the performance of polycapillary optics, when aligned to one of the most intense x-ray micro sources in the world, the liquid-metal-jet D2+. Knife edge scans were performed together with a photon-counting medipix x-ray camera to quantify focus properties such as, flux, flux density, transmission, gain and beam width. Measurements were conducted with a 20 μm source spot that was compared to a simulated 200 μm source spot, both at 260 W electron beam power. The data from vertical and horizontal scans were combined to reconstruct the 2D functionality of the polycapillary optic. The flux density were almost four times higher with the 20 μm spot compared to the simulated 200 μm spot. This result correlated with the condition for total external reflection and the local divergence. The conclusion is that the small source spot of the liquid-metal-jet source improves the efficiency of the polycapillary optic. The efficiency could still be improved, if the deviation in the pointing accuracy could be minimized. Furthermore, the combination of liquid-metal-jet x-ray source and the polycapillary optic, achieved extremely high flux densities. This was specially compared to an x-ray source used for confocal micro XRF, where the flux was almost nine times higher with the liquid-metal-jet x-ray source. This allows for faster measurements within confocal micro XRF and other techniques demanding very high flux densities, but with low demands on beam divergence and spectral purity.
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Boon, Christopher Mark. "Periastron accretion in high mass X-ray binaries : comparing supergiant fast X-ray transients and Be/X-ray binaries." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/418001/.
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High Mass X-ray Binaries (HXMBs) are some of the brightest objects in the X-ray sky and test our understanding of accretion physics in extreme stellar environments. In this thesis, characterisation of the accretion processes around periastron in two Supergiant Fast X-ray Transients (SFXTs) and one Be/X-ray Binary (BeXRB) is presented. A combined XMM-Newton and INTEGRAL study of the SFXT SAX J1818.6-1703 reveals the source to be in an active state, presenting a low luminosity phase that can be explained by the onset of a subsonic propeller or transition to the radiative regime of quasi-spherical accretion (QSA). The strongest flaring activity coincides with significant spectral hardening and the associated luminosities of this phase suggest a potential transition to the Compton regime of QSA. Spectral analysis also reveals strong intrinsic absorption, an order of magnitude higher than previously observed and among the highest measured in an SFXT. Observations of the SFXT IGR J18450-0435 with XMM-Newton also show low luminosity phases that can be explained by the onset of the radiative regime of QSA. Fast flaring behaviour is attributed to transition to the Compton regime and evidence of the accretion of magnetised stellar wind is presented. Spectral analysis again reveals enhanced local absorption up to five times greater than previous reported. A multi-wavelength study of the BeXRB IGR J01217-7257 allows the discovery of X-ray periodicities of 82.5±0.7 days and 2.1562±0.0001 seconds attributed to the neutron star orbital and spin periods respectively. Detected X-ray outbursts are put into an orbital context and found to be consistent with Type-I outbursts. Analysis of long-baseline optical data reveals short periodicities (∼ 1 day) that are attributed to non-radial pulsations (NRPs) of the companion and an association between the NRPs, decretion disc growth and the onset of Type-I outbursts is suggested.
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Wojdowski, Patrick Stephen 1971. "An X-ray spectroscopic study of the SMC X-1/Sk X-ray binary system." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/85257.
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MOSTACCI, DOMIZIANO VALERIO. "X-RAY EMISSION FROM LASER-HEATED SPHERICAL PLASMAS." Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/188093.
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A model has been developed for calculating x-ray line emission from spherical plasmas. The main features of this method are: (1) Plasma parameters are obtained from a one-dimensional Lagrangian hydrodynamics and heat flow code. (2) Multi-frequency groups: the line structure can be reproduced with the desired accuracy by adjusting the number of frequency groups. (3) Self consistent, time dependent excited level populations and radiation fluxes: the code starts with coronal populations, calculates the ensuing radiation flux and then recalculates the populations and so on, iterating until convergence is reached. (4) Goemetrical groups of rays groups by spherical impact parameters. (5) Line broadening due to ionic thermal agitation and Doppler shift due to the net plasma flow velocity. Inclusion of the flow velocity shift would be different without the multi-frequency group treatment. The method has been applied to an aluminum target, and the results are in good agreement with previous experimental work. The total energy, summed over all lines, as well as the line intensity ratios (which are a sensitive measure of agreement with experiment) were predicted with good accuracy. The pictures that would be seen by a pinhole camera are also calculated by the code.
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Krumpe, Mirko. "X-ray and optical properties of X-ray luminous active galactic nuclei." Phd thesis, Universität Potsdam, 2007. http://opus.kobv.de/ubp/volltexte/2008/1699/.
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Giacconi et al. (1962) discovered a diffuse cosmic X-ray background with rocket experiments when they searched for lunar X-ray emission. Later satellite missions found a spectral peak in the cosmic X-ray background at
~30 keV. Imaging X-ray satellites such as ROSAT (1990-1999) were able to resolve up to 80% of the background below 2 keV into single point sources, mainly active galaxies. The cosmic X-ray background is the integration
of all accreting super-massive (several million solar masses) black holes in the centre of active galaxies over cosmic time. Synthesis models need further populations of X-ray absorbed active galaxy nuclei (AGN) in order to explain the cosmic X-ray background peak at ~30 keV. Current X-ray missions such as XMM-Newton and Chandra offer the possibility of studying these additional populations.
This Ph.D. thesis studies the populations that dominate the X-ray sky. For this purpose the 120 ksec XMM-Newton Marano field survey, named for an earlier optical quasar survey in the southern hemisphere, is analysed. Based on the optical follow-up observations the X-ray sources are spectroscopically classified. Optical and X-ray properties of the different X-ray source populations are studied and differences are derived. The amount of absorption
in the X-ray spectra of type II AGN, which are considered as a main contributor to the X-ray background at ~30 keV, is determined. In order to extend the sample size of the rare type II AGN, this study also includes objects from another survey, the XMM-Newton Serendipitous Medium Sample. In addition, the dependence of the absorption in type II AGN with redshift and X-ray luminosity is analysed. We detected 328 X-ray sources in the Marano field. 140 sources were spectroscopically classified. We found 89 type I AGN, 36 type II AGN, 6 galaxies, and 9 stars. AGN, galaxies, and stars are clearly distinguishable by their optical and X-ray properties. Type I and II AGN do not separate clearly. They have a significant overlap in all studied
properties. In a few cases the X-ray properties are in contradiction to the observed optical properties for type I and type II AGN. For example we find type II AGN that show evidence for optical absorption but are not absorbed in X-rays. Based on the additional use of near infra-red imaging (K-band), we were able to identify several of the rare type II AGN.
The X-ray spectra of type II AGN from the XMM-Newton Marano field survey and
the XMM-Newton Serendipitous Medium Sample were analysed. Since most of the sources have only ~40 X-ray counts in the XMM-Newton PN-detector, I carefully studied the fit results of simulated X-ray spectra as a function of fit statistic and binning method. The objects revealed only moderate absorption. In particular, I do not find any Compton-thick sources (absorbed by column densities of NH > 1.5 x 10^24 cm^−2). This gives evidence that type II AGN are not the main contributor of the X-ray background around 30 keV. Although bias effects may occur, type II AGN show no noticeable trend of the amount of
absorption with redshift or X-ray luminosity.Giacconi et al. (1962) entdeckten mit Hilfe von Raketenexperimenten auf der Suche nach Röntgenstrahlung vom Mond eine scheinbar diffuse extragalaktische Röntgenhintergrundstrahlung. Spätere Satellitenmissionen detektierten ein Maximum dieser Strahlung bei ~30 keV. Abbildenden Röntgensatelliten wie ROSAT (1990-1999) gelang es, bis zu 80% des diffusen Hintergrundes unter 2 keV in einzelne Punktquellen aufzulösen, von denen die überwiegende Mehrheit aktive Galaxienkerne waren. Der Röntgenhintergrund ist somit wahrscheinlich als die Emission der Gesamtheit aller akkretierenden superschweren (mehrere Millionen Sonnenmassen) schwarzen Löcher in den Zentren von Galaxien in der kosmischen Geschichte zu verstehen. Zur Erklärung des Maximums der spektralen Energieverteilung der Röntgenhintergrundstrahlung bei ~30 keV benötigen theoretische Modelle jedoch zusätzliche Populationen von röntgenabsorbierenden aktiven Galaxienkernen (AGN). Derzeitige Röntgenmissionen wie XMM-Newton und Chandra ermöglichen die Untersuchung dieser Quellklassen. Die vorliegende Arbeit untersucht die Quellpopulationen, die den Röntgenhimmel dominieren. Dazu wird die 120 ksec XMM-Newton Beobachtung im Marano Feld, Ziel einer früheren optischen AGN-Durchmusterung am Südhimmel, ausgewertet. Die optischen und Röntgeneigenschaften der unterschiedlichen Quellpopulationen werden untersucht und Unterschiede erarbeitet. Für die röntgenabsorbierende Objektklasse der Typ II AGN, die man als möglichen Erzeuger der Röntgenstrahlung um 30 keV betrachtet, wird aus den Röntgenspektren das Ausmaß der Absorption ermittelt. Um die Anzahl dieser selten gefundenen Objekte zu erhöhen, werden in dieser Arbeit zusätzliche Objekte aus der Röntgendurchmusterung des “XMM-Newton Serendipitous Medium Sample” einbezogen. Die Abhängigkeit der Absorption von der Rotverschiebung und der Röntgenleuchtkraft wird untersucht. Von 328 Röntgenquellen im Marano Feld konnten 140 spektroskopisch klassifiziert werden. Es wurden 89 Typ I AGN, 36 Typ II AGN, 6 Galaxien und 9 Sterne gefunden. Nur basierend auf den optischen und Röntgeneigenschaften können AGN, Galaxien und Sterne unterschieden werden. Typ I und II AGN lassen sich nicht klar trennen und zeigen große Gemeinsamkeiten in den untersuchten Eigenschaften. Mit Hilfe von zusätzlichen Aufnahmen im nahen Infraroten (K-Band) konnten erfolgreich mehrere seltene Typ II AGN identifiziert werden. Die Röntgenspektren von Typ II AGN aus dem XMM-Newton Marano Feld und dem “XMM-Newton Serendipitous Medium Sample” wurden ausgewertet. Die Objekte weisen nur eine mäßige Absorption auf und scheinen somit nicht einen Hauptbestandteil des Röntgenstrahlungshintergrundes um 30 keV zu erzeugen. Obwohl Selektionseffekte nicht vollständig verstanden sind, zeigen Typ II AGN keine erkennbare Abhängigkeit der Absorption von der Rotverschiebung oder der Röntgenleuchtkraft.
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Nazary, Mineh. "Optimization of X-ray Source for Digital Mammography - X-ray Optics Approach." Thesis, Linköpings universitet, Institutionen för medicinsk teknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-84857.
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The work presents a new design of X-ray source for digital mammography imaging with the help of crystal sources and X-ray optics technology. The aim of the project was to introduce a new source for medical x ray imaging and evaluate its ability of performance. The source is build of an array of multiple micro-emitters instead of a single source. These sources are made of pyroelectric crystals. The produced Xrays are then getting focused by passing through prism array lenses. These lenses are used as focusing pre-object collimator, to reduces the divergence of the beam and increases the utilization of the available X-rays. The lenses are coupled with collimators to avoid scatter rays. The software used for the simulations of the system and evaluations is MATLAB. Several methods, like calculating the point spread function and modulation transfer function, have been applied in order to evaluate the system imaging ability and the system efficiency. Later on in calculations, an anti scatter grid is added as a post collimator and system efficiency is calculated again before and after the grid. The ability of the system to perform is calculated for digital mammography. The results in the end showed how the lenses perform while using different photon energies. However the current results were not enough to approve the ability of the system for medical imaging uses. For achieving more comprehensive and certain answers further investigations will be necessary.
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Froud, Christopher Andrew. "Designing a nanoscale X-ray source : towards single molecule X-ray scattering." Thesis, University of Southampton, 2007. https://eprints.soton.ac.uk/52042/.
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This thesis describes the design and construction of a femtosecond X-ray source based on high harmonic generation in an argon filled hollow capillary waveguide. The system has demonstrated excellent efficiency at generating harmonics in the range 20-50 eV and is tuneable by exploiting the ionization-induced blue-shift that occurs in the waveguide. The X-ray source is designed for X-ray scattering experiments, which will ultimately allow the imaging of single biomolecules. Such experiments will require an intense, focused X-ray beam. Towards this aim, this thesis demonstrates focusing techniques based on tapered capillary optics, including a model that was developed to understand their behaviour.
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Eckart, Megan Elizabeth Harrison Fiona A. Harrison Fiona A. "Measurements of X-ray selected AGN and novel superconducting X-ray detectors /." Diss., Pasadena, Calif. : California Institute of Technology, 2007. http://resolver.caltech.edu/CaltechETD:etd-06072007-130804.
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Lott, Dieter. "Magnetic X-ray Reflectivity." Diss., lmu, 2001. http://nbn-resolving.de/urn:nbn:de:bvb:19-3439.
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Alshehabi, Abbas. "Grazing X-Ray Analysis." 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/157580.
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Zora, J. A. "X-ray diffraction studies." Thesis, University of Sussex, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374467.
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Sutton, Andrew. "Ultraluminous X-ray sources." Thesis, Durham University, 2013. http://etheses.dur.ac.uk/9431/.
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Ultraluminous X-ray sources (ULXs) are accreting black holes with X-ray luminosities in excess of the Eddington limit for a typical ~10 solar mass Galactic black hole. There is an emerging consensus that most ULXs are probably fairly typical stellar remnant black holes in a new super-Eddington `ultraluminous' accretion state, characterised by a soft excess and high energy spectral curvature, which may be associated with a radiatively-driven wind and cool, optically thick Comptonisation respectively. However, this scenario may be insufficient to produce some of the most luminous ULXs. Here we present a sample of extreme luminosity ULXs, and show that their X-ray spectral and timing properties are consistent with most of them being in the sub-Eddington low/hard state. Given their luminosities, this suggests that these ULXs contain 10^3-10^4 solar mass black holes. But, in one of the extreme ULXs we find evidence of high energy spectral curvature, which is a key feature of the ultraluminous state. We explore this ULX further, and show that its X-ray spectrum is consistent with being in the ultraluminous state, but with any wind emission obscured from view by the high column density of material in the direction of the source. We also investigate the ultraluminous state further, and present an X-ray spectral and timing study of ULXs with some of the highest quality XMM-Newton data. We show that their spectral and timing properties are consistent with current models of super-Eddington accretion, where a massive, radiatively-driven wind forms a funnel-like geometry around the source. Then, the observed X-ray properties are dependant on both the accretion rate, and the inclination at which the ULX system is observed. Finally, we consider optical counterparts to a small sample of ULXs. We fit the X-ray and optical data of these with a new spectral model of an irradiated, colour-temperature-corrected accretion disc, finding that ~0.1 per cent of their bolometric luminosity is reprocessed in the outer disc. This may be due to the opposing effects of self-shielding in the accretion disc and reflection in a super-Eddington wind.
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Marchesini, Stefano. "X ray fluorescence holography." Université Joseph Fourier (Grenoble), 2000. http://www.theses.fr/2000GRE10012.
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Dans de nombreux cas la structure atomique des solides ne peut etre resolue par les techniques traditionnelles de la cristallographie. Cela peut etre le cas, par exemple, pour les etudes locales d'impuretes diluees, les interfaces enterrees et plus generalement les systemes non periodiques. En 1996 une nouvelle methode structurale, l'holographie x a resolution atomique est apparue. Elle a pour origine la technique d'imagerie holographique, inventee par gabor il y a 50 ans. Dans ce travail, nous presentons d'abord le principe et le cadre theorique de l'holographie par fluorescence, fondes sur le concept de source / detecteur interne. Puis nous decrivons les developpements techniques que nous avons progressivement obtenus, afin de transposer cette methode des rayons x de laboratoire vers la source synchrotron esrf ; ceci sous le double point vue du montage experimental et de l'analyse des donnees. Des resultats intermediaires interessants sont l'imagerie des configurations des lignes de kossel et des ondes stationnaires, a partir desquelles des informations structurales - parametre de reseau, symetrie et orientation cristallines - peuvent etre deduites. Puis l'hologramme et la reconstruction atomique de monocristaux modeles tels que coo(111) sont presentes, avec - pour la premiere fois, une resolution isotrope de 0,5 a et une qualite d'image qui n'avait pas ete obtenue jusqu'a present. Enfin, la premiere application de l'holographie par fluorescence aux films epitaxiques est donnee. Des differences significatives entre des films d'alliages fept chimiquement ordonne et desordonne ont ete obtenus, ouvrant la voie a l'etude de l'ordre a courte distance directionnel dans de tels systemes, au-dela des possibilites de la spectroscopie xafs. De nouvelles perspectives sont offertes en conclusion, concernant l'holographie atomique resolue en temps, ainsi que - sur la base d'une etude preliminaire d'holographie nucleaire - le potentiel de cette technique pour le magnetisme local et la selectivite en site.
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Bompadre, Silvia G. "Bremsstrahlung x-ray holography /." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/9716.
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Sasmaz, Mus Sinem. "X-ray And Timing Properties Of Anomalous X-ray Pulsar 1e 2259+586." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/3/12608625/index.pdf.
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In this thesis, we present the spectral and timing variabilities of anomalous X-ray pulsar 1E 2259+586 observed with European Photon Imaging PN Camera (EPIC PN) on board X-ray Multi Mirror Mission (XMM), Proportional Counter Array (PCA) on board Rossi X-ray Timing Explorer (RXTE) and Advanced CCD Imaging Spectrometer (ACIS) on board Chandra X-ray Observatory.
We presented the results of spectral analysis of 2000 January 11 ACIS observation. Pulse phase spectroscopy was performed on two XMM observations before and after the outburst. Pulse profiles of two XMM observations before the outburst and three XMM observations after the outburst were studied. Results are consistent with the those presented by Patel et al. (2001) and Woods et al. (2004).
We searched for the spectral variations versus spin rate during the outburst. Long-term spectral, frequency and spin-down rate variations are presented between 1996 and 2006 including 98 RXTE and 4 XMM observations. However, except outburst region (Woods et al. 2004) no significant spectral and spin rate variabilities were seen. Around the outburst region we confirmed the spectral hardening with increasing spin rate and flux.
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McCluskey, Philip James. "X-ray emission and x-ray photoelectron spectroscopy of alloy and catalyst surfaces." Thesis, Queen Mary, University of London, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264926.
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Atkins, C. "Active X-ray optics for the next generation of X-ray space telescopes." Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/19312/.
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Described within is the design, manufacture, metrology and X-ray testing of an active X-ray prototype intended for the next generation of X-ray telescopes. One of the challenges faced by the X-ray telescope community is how to combine high resolution and high sensitivity into one system, as weight limitations place constraints on the optics that can be launched. Therefore the mandate of the active X-ray prototype is to provide high sensitivity through the ability of the optics to be nested and to deliver high angular resolution through the active control of the optic’s form. Piezoelectric unimorph actuators provide the active component: it is intended that they will correct for figure errors within the optic and therefore increase the angular resolution capability. The prototype’s design is based upon an ellipsoidal segment which provides point-to-point focussing of an X-ray source. The prototype itself is composed of an electroformed nickel optic where the non-reflective surface is populated with 30 piezoelectric actuators and it is the production of the prototype that is the core of the presented research. Metrology of the actuators’ influence functions is presented and highlight the prototype’s ability to deform its optic surface by microns. In addition, the measured influence functions are compared against finite element models and a distinct similarity between the functions is observed. The prototype was tested at an X-ray beamline facility in November 2008 and the results showed the prototype’s ability to correct the optic to achieve an improved angular resolution: from 0.786 arc-minutes to 0.686 arc-minutes in terms of full width half maximum. Finally, difficulties in the manufacture of the prototype and X-ray testing shall be presented alongside future work in conclusion to this thesis.
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Benlloch, García Sara. "Long-term x-ray variability of active galactic nuclei and x-ray binaries." [S.l. : s.n.], 2004. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB11051893.
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Marsden, David. "X-ray observations of soft gamma-ray repeaters /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC IP addresses, 1999. http://wwwlib.umi.com/cr/ucsd/fullcit?p9935475.
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Yamazaki, Ryo. "Toward the Unified Theory of Long and Short Gamma-Ray Bursts, X-Ray Rich Gamma-Ray Bursts, and X-Ray Flashes." 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/147812.
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Griffiths, Richard. "X-ray spectral studies of Scorpius X-1." Thesis, University of Leicester, 1995. http://hdl.handle.net/2381/34092.
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The thesis describes the design, testing and flight results from two Skylark rocket experiments which were primarily intended to make high-resolution searches for line emission in the X-ray spectrum of Scorpius X-1. The observations of Sco X-1, up to the end of 1968, over all frequencies of the electromagnetic spectrum, are summarised, together with the astrophysical models of the object and their implications for the X-ray spectrum. The decision to search for line emission in the spectrum arose from the need to establish whether the X-rays are of bremsstrahlung or synchrotron origin. The first Bragg crystal spectrometer to study a non-solar X-ray source was flown on a sun-pointing British Skylark from Woomera in March 1970, and an improved experiment of the same kind was flown on an E.S.R.O. Skylark from Sardinia in March 1971. The payloads were the first to employ roll stabilisation on an X-ray star using proportional detectors. The proportional detector experiments confirmed the bremsstrahlung nature of the X-ray emission, while the high-resolution spectrometers established that Doppler-broadened Fe XXV line emission is at least an order of magnitude less intense than is expected from a low-density plasma. Fluctuations in the X-ray intensity were observed on 1 minute time scales, as found in the optical data. A summary is given of contemporary work on Sco X-1, and the absence of narrow line emission is found to be consistent with those models of the X-ray source which envisage a high-density, toroidal plasma in orbit around a central white-dwarf or neutron star.
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Koliopanos, Filippos [Verfasser], and Rashid [Akademischer Betreuer] Sunyaev. "X-ray diagnostics of ultra-compact X-ray binaries / Filippos Koliopanos. Betreuer: Rashid Sunyaev." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2015. http://d-nb.info/1073825965/34.
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Gislason-Lee, Amber Jill. "The effect of X-ray system settings on perception in cardiac X-ray imaging." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/15568/.
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Cardiologists use coronary angiograms to diagnose and treat cardiac patients during percutaneous coronary interventions (PCI). The X-ray photon fluence used to capture an X-ray image is directly related to image noise, whereby more fluence improves image quality; however exposure to X-rays can be harmful, therefore fluence level must be optimised. Digital image processing (DIP) may enhance image quality such that it allows for lower levels of photon fluence during image capture. The effect of changes in photon fluence and DIP on perception of coronary angiograms by clinicians was determined. Computer-generated quantum noise was added to five unprocessed patient angiograms to simulate incremental reductions in photon fluence, followed by state-of-the-art DIP. The noise adding software was calibrated for clinically-relevant settings, and validated using standard objective and subjective measurements. The degraded images were viewed next to corresponding original (not degraded) images in a staircase psychophysics experiment, with and without DIP; 12 observers selected their preferred angiogram until the point of subjective equality (PSE), i.e. level of degradation at which the observer could not perceive a difference between the original and degraded images, was determined. The PSEs were 33±15% and 34±15% reductions in fluence for unprocessed and processed images respectively. In a second psychophysics experiment angiograms representing selected fluence levels, with and without DIP, were scored individually by 16 observers on a continuous scale. Scores were analysed by a statistical regression model to quantify the fluence reduction facilitated by DIP. The DIP facilitated 25% [19%, 31%] reduction in fluence compared to no processing for the same image quality score. A significant amount of image noise can be added to coronary angiograms without being perceived, indicating potential for a significant reduction in radiation exposure exclusive to that which can be facilitated by DIP. These reductions would benefit both PCI patients and personnel.
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Gorman, Martin Gerard. "X-ray diffraction studies of shock compressed bismuth using X-ray free electron lasers." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/25865.
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The ability to diagnose the structure of a material at extreme conditions of high-pressure and high-temperature is fundamental to understanding its behaviour, especially since it was found that materials will adopt complex crystal structures at pressures in the Terapascal regime (1TPa). Static compression, using the diamond anvil cell coupled with synchrotron radiation has to date been the primary method for structural studies of materials at high pressure. However, dynamic compression is the only method capable of reaching pressures comparable to the conditions found in the interior of newly discovered exo-planets and gas giants where such exotic high-pressure behaviour is predicted to be commonplace among materials. While generating extreme conditions using shock compression has become a mature science, it has proved a considerable experimental challenge to directly observe and study such phase transformations that have been observed using static studies due to the lack of sufficiently bright X-ray sources. However, the commissioning of new 4th generation light sources known as free electron lasers now provide stable, ultrafast pulses of X-rays of unprecedented brightness allowing in situ structural studies of shock compressed materials and their phase transformation kinetics in unprecedented detail. Bismuth, with its highly complex phase diagram at modest pressures and temperatures, has been one of the most studied systems using both static and dynamic compression. Despite this, there has been no structural characterisation of the phases observed on shock compression and it is therefore the ideal candidate for the first structural studies using X-ray radiation from a free electron laser. Here, bismuth was shock compressed with an optical laser and probed in situ with X-ray radiation from a free electron laser. The evolution of the crystal structure (or lack there of) during compression and shock release are documented by taking snapshots of successive experiments, delayed in time. The melting of Bi on release from Bi-V was studied, with precise time scans showing the pressure releasing from high-pressure Bi-V phase until the melt curve is reached off-Hugoniot. Remarkable agreement with the equilibrium melt curve is found and the promise of this technique has for future off-Hugoniot melt curve studies at extreme conditions is discussed. In addition, shock melting studies of Bi were performed. The high-pressure Bi - V phase is observed to melt along the Hugoniot where melting is unambiguously identified with the emergence of a broad liquid-scattering signature. These measurements definitively pin down where the Hugoniot intersects the melt curve - a source of some disagreement in recent years. Evidence is also presented for a change in the local structure of the liquid on shock release. The impact of these results are discussed. Finally, a sequence of solid-solid phase transformations is observed on shock compression as well as shock release and is detected by distinct changes in the obtained diffraction patterns. The well established sequence of solid-solid phase transformations observed in previous static studies is not observed in our experiments. Rather, Bi is found to exist in some metastable structures instead of forming equilibrium phases. The implications these results have for observing reconstructive phase transformations in other materials on shock timescales are discussed.
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Piccinardi, Rita. "X-Ray Free-Electron Lasers." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10286/.
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Recenti sviluppi nella progettazione di impianti di luce di sincrotrone di quarta generazione riguardano la produzione di fasci di luce nella banda dei raggi X con elevate caratteristiche in termini di brillanza, coerenza e impulsi estremamente brevi ( femtosecondo ) . I principali schemi per la produzione della radiazione XFEL riguardano l’impiego di ondulatori con differenti modalità di seeding. L’utilizzo dei fasci di radiazione XFEL nelle linee di luce per applicazioni di imaging, spettroscopia e diffrazione, ha determinato un costante sforzo sia nello sviluppo di dispositivi ottici in grado di selezionare e focalizzare il fascio su dimensioni nanometriche, che nella sperimentazione di tecniche “lensless” in grado di superare i limiti imposti dall’utilizzo di tali dispositivi . I risultati ottenuti nella produzione dei fasci hanno consentito nuove possibilità di indagine nella struttura dei materiali su distanze atomiche nella definizione, senza precedenti di dettagli su scale temporali del femtosecondo, permettendo lo studio, non solo di strutture atomiche in condizioni di equilibrio stabile quanto di stati della materia velocemente dinamici e di non equilibrio.
CXDI e Spettroscopia Strutturale Ultraveloce risolte in tempo sono alcune delle tecniche in cui l’utilizzo della radiazione XFEL apre nuove possibilità di indagine agli stati transienti della materia permettendo la ricostruzione della dinamica di processi chimico –fisici su intervalli temporali finora inaccessibili .
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Johansson, Göran. "Compact Soft X-Ray Microscopy." Doctoral thesis, KTH, Physics, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3518.
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This thesis describes the development of soft x-rayreflective optics, instrumentation and applications for compactsoft x-ray microscopy. The microscope is based on a table-topliquid-jet-target laser-plasma source in combination with aspherical normal-incidence multilayer condenser mirror andnanofabricated diffractive optics for imaging. High-resolutionimaging is performed at the wavelength 3.374 nm in thewater-window (2.3 - 4.4 nm), where natural contrast betweencarbon and oxygen allows imaging of unstained biologicalmaterial in their natural aqueous environment.
The design and implementation of a compact soft x-rayreflectometer based on a laser-plasma source is described. Thereflectometer allows rapid and accurate characterization ofnormal-incidence multilayer coatings used at water-windowwavelengths. This instrument, which measures absolutereflectivity and multilayer period, is now used in thefabrication process, aiming to improve the soft x-raynormal-incidence multilayer condenser system of the compactsoft x-ray microscope. Latest results from the developmentprocess are presented.
A new design of the compact soft x-ray microscope, withimprovements in mechanical and thermal stability, providesuser-friendly and daily operation. This includes also a newnozzle design for the liquid-jet-target laser-plasma source,which enables higher source stability and operation withcryogenic liquids. In addition, a new experimental arrangementunder construction is briefly described. It will utilize acondenser zone plate and operate at the wavelength 2.478nm.
Finally, performance test of the compact soft x-raymicroscope is presented and discussed. In addition, a projectto explore the use of soft x-ray microscopy for imaging sensorycells is described. The high-resolution imaging of these cellswas performed at the synchrotron-based soft x-ray microscope atLawrence Berkeley National Laboratory (LBNL).
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Boye, Pit. "Nanofocusing Refractive X-Ray Lenses." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-27137.
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This thesis is concerned with the optimization and development of the production of nanofocusing refractive x-ray lenses. These optics made of either silicon or diamond are well-suited for high resolution x-ray microscopy. The goal of this work is the design of a reproducible manufacturing process which allows the production of silicon lenses with high precision, high quality and high piece number. Furthermore a process for the production of diamond lenses is to be developed and established. In this work, the theoretical basics of x-rays and their interaction with matter are described. Especially, aspects of synchrotron radiation are emphasized. Important in x-ray microscopy are the different optics. The details, advantages and disadvantages, in particular those of refractive lenses are given. To achieve small x-ray beams well beyond the 100nm range a small focal length is required. This is achieved in refractive lenses by moving to a compact lens design where several single lenses are stacked behind each other. The, so-called nanofocusing refractive lenses (NFLs) have a parabolic cylindrical shape with lateral structure sizes in the micrometer range. NFLs are produced by using micro-machining techniques. These micro-fabrication processes and technologies are introduced. The results of the optimization and the final fabrication process for silicon lenses are presented. Subsequently, two experiments that are exemplary for the use of NFLs, are introduced. The first one employs a high-resolution scanning fluorescence mapping of a geological sample, and the second one is a coherent x-ray diffraction imaging (CXDI) experiment. CXDI is able to reconstruct the illuminated object from recorded coherent diffraction patterns. In a scanning mode, referred to as ptychography, this method is even able to reconstruct the illumination and the object simultaneously. Especially the reconstructed illumination and the possibility of computed propagation of the wavefield along the focused beam yields findings about the optic used. The collected data give interesting information about the lenses and their aberrations. Comparison of simulated and measured data shows good agreement. Following this, the fabrication process of diamond lenses is described. Diamond with its extraordinary properties is well-suited as lens material for refractive lenses. Finally, a concluding overview of the present and future work of nanofocusing lenses is givenDiese Dissertation beschäftigt sich mit der Entwicklung und Optimierung der Herstellungsprozesse von refraktiven nanofokussierenden Röntgenlinsen. Diese aus Silizium oder Diamant hergestellten Optiken, sind hervorragend für hochauflösende Röntgen\-mikroskopie geeignet. Ziel dieser Arbeit ist es, einen reproduzierbaren Herstellungsprozess zu erarbeiten, der es erlaubt, Siliziumlinsen von hoher Präzision, Qualität und Quantität zu fertigen. Zusätzlich soll ein Prozess für Diamantlinsen entwickelt und etabliert werden. In der folgenden Arbeit werden die theoretischen Grundlagen von Röntgenstrahlung und deren Wechselwirkung mit Materie beschrieben. Spezielle Aspekte der Synchrotronstrahlung werden hervorgehoben. Wichtig im Zusammenhang mit Röntgenmikroskopie sind die verschieden Optiken. Deren Details, Vor- und Nachteile, insbesondere die der brechenden Linsen, werden genannt. Zur Erzeugung fein gebündelter Röntgenmikrostrahlen im Bereich unter 100nm lateraler Größe benötigt man sehr kurze Brennweiten. Mit brechenden Linsen lässt sich dieses mittels eines kompakten Linsendesigns von vielen hintereinander gestapelten Einzellinsen realisieren. Die so genannten refraktiven nanofokussierenden Linsen (NFLs) besitzen eine parabolische Zylinderform mit lateralen Strukturgrößen im Mikrometerbereich. NFLs werden mittels spezieller Technologien der Mikroprozessierung hergestellt. Diese Mikrostrukturierungsverfahren werden mit ihren jeweiligen Prozessschritten und zugehörenden Technologien vorgestellt. Die Ergebnisse der Optimierung und der endgültige Mikrostrukturierungsprozess für Siliziumlinsen werden dargelegt. Im Anschluss daran werden zwei Experimente erläutert, die beispielhaft für die Anwendung von NFLs stehen. Ersteres ist ein ortsaufgelöstes Fluoreszenzrasterexperiment einer geologischen Probe und das zweite ein kohärentes Röntgen-Beugungsexperiment (CXDI). CXDI ist in der Lage, aus kohärent aufgenommen Beugungsbildern das beleuchtete Objekt zu rekonstruieren. Kombiniert mit einem rasternden Verfahren, welches Ptychographie genannt wird, ist diese Methode in der Lage, die Beleuchtungsfunktion und das Objekt gleichzeitig zu rekonstruieren. Besonderes die rekonstruierte Beleuchtungsfunktion und die Möglichkeit der computergestützten Propagation des Wellenfeldes entlang des fokussierten Strahls, geben aufschlussreiche Informationen über die verwendete Optik. Neue Erkenntnisse über die Linsen und deren Aberrationen können so gewonnen werden. Vergleiche von simulierten mit gemessenen Daten zeigen gute Übereinstimmung. Daran anschließend erfolgt die Beschreibung der Entwicklung eines Fabrikationsprozess für Diamantlinsen. Diamant mit seinen außergewöhnlichen Materialeigenschaften ist besonders gut als Linsenmaterial für refraktive Röntgenlinsen geeignet. Abschliessend wird ein zusammenfassender Überblick über die derzeitigen und die zu erwartenden Entwicklungen bei refraktiven Linsen gegeben
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Paudel, Krishna. "Stitching of X-ray Images." Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-184441.
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Image processing and analysis algorithms are widely used in medical systems to analyze medical images to help diagnose the disease of a patient. This thesis covers one of the demanding problems of a medical system: Stitching of X-ray Images. The flat panel of an X-ray system cannot cover all part of a body, so image stitching is incorporated in the medical system to combine two or more X-ray images and get a single high resolution image. The output of this thesis work is to develop a real-time and user interactive stitching application which works for all X-ray images with different intensity and orientation. The stitching of X-ray images is carried out by employing two basic steps: registration and blending. The classical registration methods search for all the pixels to get the best registration. These methods are slow and cannot perform well for high resolution X-ray images. The feature based registration methods are faster and always gives the best registration. This thesis evaluates three popular feature based registration methods: HARRIS, SIFT and SURF. The exhaustive nearest neighborhood method has been modified to get faster matching of key points. The overlapping areas of the composite image are blended to remove the seams and discontinuities. This thesis evaluates some faster blending techniques and incorporates an advanced blending method using blending masks to blend complexly aligned images.
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Klos, Richard A. "Scattering from X-ray mirrors." Thesis, University of Leicester, 1987. http://hdl.handle.net/2381/35710.
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Scattering from X-ray Mirrors deals with the the phenomena observed when x-rays are reflected from high quality mirror surfaces at grazing incidence. The presence of micro- irregularities in the reflecting surface causes power to be deviated away from the specular direction and into the wings of the angular distribution of radiation. Both theoretical and experimental investigations are presented. The two principal theories of the scattering of electromagnetic radiation are reviewed and are shown to produce identical results in the smooth surface limit. The scalar theory is further developed so as to be applicable to a scattering surface which can be described by an arbitrary surface height distribution function for any surface autocovariance function. The theoretical advances reported suggest a means by which the surface height distribution statistics of mirror surfaces might be derived from experimental scattering measurements. The experimental work in the thesis deals with a scattering experiment designed to test these theoretical developments. The development work involved in the construction of the Variable Angle Scattering Experiment (VASE) is presented and the anomalous results obtained from scattering measurements from two test flat x-ray mirrors are discussed. A shadowing model is devised to account for the anomalous results from the VASE. The shadowing model is then shown to be in good agreement with the VASE data and with data from other scattering experiments. The shadowing model, which provides a means of measuring the properties of pure mirror surfaces, is further developed to enable measurements of surface structure on mirrors which have become specked with small sparse contaminant features, thus allowing highly sensitive estimates of contaminant density and height to be made.
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Eriksson, Fredrik. "Soft X-ray multilayer mirrors /." Linköping : Univ, 2004. http://www.bibl.liu.se/liupubl/disp/disp2004/tek875s.pdf.
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Klein-Wolt, Marc. "Black hole X-ray binaries." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2004. http://dare.uva.nl/document/91386.
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Duxbury, Dominic Mark. "Novel X-ray imaging detectors." Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243037.
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Lindsay, Simon Thomas. "X-ray observations of Mercury." Thesis, University of Leicester, 2015. http://hdl.handle.net/2381/31433.
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Data from MESSENGER and the GOES solar activity archive are used to deduce properties of Mercury and its X-ray environment in preparation for the forthcoming ESA/JAXA BepiColombo mission to Mercury. Data from MESSENGER’s X-ray spectrometer operations at Mercury exhibit background X-ray enhancements which are identified as the results of astrophysical sources crossing the instrument field of view and of electron bombardment of the X-ray spectrometer causing fluorescence within the instrument. These electron enhancements are analysed and mapped, leading to a three-dimensional representation of low-energy electron populations in the Mercury environment, the distributions of which are associated with features of Mercury’s magnetosphere, including the sunward magnetopause and magnetic equator. The population is characterised, producing estimates of low-energy electron number densities which are consistent with previous observations. Thus, the X-ray spectrometer functions as a proxy detector for electrons with energies below the threshold of dedicated electron detectors. Variations in seasonal X-ray background flux observed by the MESSENGER X-ray spectrometer are investigated, with a modulation visible with a periodicity of one Mercury year. Several telemetry parameters, including temperature, show corresponding variations. The origin of the variation in background flux is identified as the calculation in spacecraft telemetry relating instrument live time to instrument integration time, which varies on the same yearly period. The GOES solar activity archive is used to generate a model of solar X-ray flux levels, with the intention of providing an estimate of the levels of X-ray flux the BepiColombo mission will encounter, and subsequently the volume and rate of data that the MIXS instrument will produce. This model is used to predict the likelihood of the instrument experiencing data loss events by exceeding the data storage available, and how this likelihood varies with the level of solar flux and the onboard storage space that is allocated to the instrument.
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Kim, Victoria. "Hard X-ray test objects." Thesis, KTH, Tillämpad fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-233228.
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Hontsova, S. S., and E. M. Maksimova. "X-Ray analysis of meteorite." Thesis, Sumy State University, 2014. http://essuir.sumdu.edu.ua/handle/123456789/39427.
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Meteorites are one of the most accessible objects of extraterrestrial matter. Therefore the study of the structural features and physical properties of crystals of meteorites can provide information about the formation of the crystal structure of matter in extraterrestrial conditions.
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Venturini, Federica. "Soft X-ray photoemission spectroscopy." Université Joseph Fourier (Grenoble), 2005. http://www.theses.fr/2005GRE10175.
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La motivation principale de cette thèse a été de déterminer les avantages et les inconvénients de l'utilisation de la spectroscopie de photoémission résolue en angle dans le domaine des rayons X mous. L'étude d'un système bien connu, Ag(001) nous permet de discuter plusieurs questions telles que le rôle de la quantité de mouvement du photon, la pertinence de l'approximation d'électron libre à l'état final, et le rôle des phonons. La polarisation de la lumière incidente a aussi été exploitée. En choisissant un tel système, nous avons aussi voulu comparer les résultats expérimentaux avec des spectres calculés de photoémission résolue en angle dans cette gamme d'énergie. Le comportement à basse température atypique des composés de Cérium est généralement imputé à l'effet Kondo. Des résultats originaux ont été obtenus en étudiant la bande de valence de trois composés monocristallins iso-structuraux de Cérium, CeCu2Ge2, CeNi2Ge2 et CeC02Ge2. La position du seuil d'absorption M5 du Cérium dans la bande d'énergie des rayons X mous est exploitée pour isoler la contribution 4f à ces spectres. De plus, l'utilisation de photons incidents d'énergie relativement élevée permet de minimiser les effets de surface. Les spectres de photoémission présentés dam cette thèse incluent des études de dépendance en température, des spectres à la résonance, des spectres résolus en angle ou bien intégrés angulairement. Les premiers sont en accord avec le modèle d'impureté unique d'Anderson, alors que les derniers suggèrent qu'il est important de prendre en compte le réseau cristallinThe main motivation behind this thesis has been to determine both the advantages and the disadvantages ofthe soft X-ray application of angle-resolved photoemission spectroscopy. The investigation of a weil known system, Ag(001), enables us to discuss several questions such as the role of the photon momentum, the applicability ofthe fiee-electron-like final state approximation and the role ofphonons. The polarisation of the incoming light has also been exploited. The choice of such a system also cornes from our des ire to compare the results with calculations of angle-resolved photoemission spectra in this energy range. The anomalous low temperature properties of Ce-based compounds are generally related to the Kondo effect. Original results have been obtained by investigating the valence band of three iso-structural single crystalline Ce compounds, CeCu2Ge2, CeNi2Ge2 and CeC02Ge2. The location of the Ce M5 absorption edge within the soft X-ray energy range is exploited in order to isolate the 4f contribution to the spectra. Added to this, the use of relatively high incoming photon energies allows minimising the surface contribution. Temperature dependent, resonant, angle-resolved and angle-integrated photoemission measurements have been performed. The former are in qualitative agreement with the single impurity Anderson model, whereas the latter suggest the importance of taking the lattice into account
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Godber, S. X. "Annular beam X-ray imaging." Thesis, Nottingham Trent University, 2014. http://irep.ntu.ac.uk/id/eprint/4009/.
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This thesis presents an investigation of depth‐resolved absorption imaging by scanning objects through an annular beam of X‐rays. The resultant ring shaped projections record depth dependent parallax. The study focuses on two different scanning methods. First, a single axis scan has been employed to record curvilinear stereoscopic images. Second, a two axis raster scanning approach enables focal plane images to be produced via tomosynthesis. These novel absorption contrast methods have been carefully designed to complement X-ray diffraction considerations. Prior work employing an annular beam concerned the collection of Xray diffraction data for structural analysis/phase identification. This method, termed Focal Construct Geometry (FCG), provided orders of magnitude increase in the intensity of the diffracted X-rays within the beam’s dark interior to enable rapid processing. However, this work relied upon a priori sample position. The research presented in this thesis establishes a complementary absorption imaging modality, which is designed to support and inform the analysis of the diffraction data by providing quantitative spatial information. This approach is essential for the autonomous interrogation of unknown objects at unknown positions within an inspection volume e.g. aviation security baggage screening. Two novel approaches have been developed and investigated. The first, termed Annular Beam Scanning (ABS), treats each annular field as a pair of semi‐annular projections as defined by an axis perpendicular to the scan direction. The resultant curvilinear stereoscopic image pairs contain depth dependent parallax along this scan direction. Algorithms to extract three‐dimensional information from the curvilinear images have been derived and validated. It has been shown that range information is proportional to the opening half‐angle ϕ of the annular beam but inversely proportional to the angular position σ of each matched element pair on the semi‐annular sensors. The second approach reassembles pixel data from a matrix of annular projections to form Multidirectional Perspective Views (MPV). These views encode object range as circular parallax. The application of Digital Tomosynthesis (DTS) employing a Shift‐and‐Add process enables focal plane images to be recorded. Unlike conventional DTS the minimum resolvable axial increment is independent of focal plane position within the inspected volume. While both approaches provide three‐dimensional data, MPV/DTS is the optimal method for combination with FCG diffraction datasets. The final part of this thesis describes results combining DTS with simulated diffraction image spaces to autonomously determine 2θ diffraction angles. This research programme has established a new annular beam imaging modality, which contributes significantly to the body of knowledge in the field of analytical 3D X‐ray imaging.