Journal articles: 'Thomson Microwave Scattering'

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Tanaka, K., M. Nishiura, S. Kubo, T. Shimozuma, and T. Saito. "Progress of microwave collective Thomson scattering in LHD." Journal of Instrumentation 10, no. 12 (December 1, 2015): C12001. http://dx.doi.org/10.1088/1748-0221/10/12/c12001.

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Foote, J. H., J. D. Barter, N. R. Sewall, J. J. Jolly, and L. F. Schlander. "Thomson scattering diagnostic for the microwave tokamak experiment." Review of Scientific Instruments 61, no. 10 (October 1990): 2861–63. http://dx.doi.org/10.1063/1.1141807.

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Chalyavi, Nahid, Peter S. Doidge, Richard J. S. Morrison, and Guthrie B. Partridge. "Fundamental studies of an atmospheric-pressure microwave plasma sustained in nitrogen for atomic emission spectrometry." Journal of Analytical Atomic Spectrometry 32, no. 10 (2017): 1988–2002. http://dx.doi.org/10.1039/c7ja00159b.

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Fundamental characteristics of a microwave plasma sustained in nitrogen (Agilent 4200 MP-ES) are investigated by a combination of thermochemical modelling and spectroscopic techniques, including Thomson scattering.

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Miles, Richard B., James B. Michael, Christopher M. Limbach, Sean D. McGuire, Tat Loon Chng, Matthew R. Edwards, Nicholas J. DeLuca, Mikhail N. Shneider, and Arthur Dogariu. "New diagnostic methods for laser plasma- and microwave-enhanced combustion." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 373, no. 2048 (August 13, 2015): 20140338. http://dx.doi.org/10.1098/rsta.2014.0338.

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The study of pulsed laser- and microwave-induced plasma interactions with atmospheric and higher pressure combusting gases requires rapid diagnostic methods that are capable of determining the mechanisms by which these interactions are taking place. New rapid diagnostics are presented here extending the capabilities of Rayleigh and Thomson scattering and resonance-enhanced multi-photon ionization (REMPI) detection and introducing femtosecond laser-induced velocity and temperature profile imaging. Spectrally filtered Rayleigh scattering provides a method for the planar imaging of temperature fields for constant pressure interactions and line imaging of velocity, temperature and density profiles. Depolarization of Rayleigh scattering provides a measure of the dissociation fraction, and multi-wavelength line imaging enables the separation of Thomson scattering from Rayleigh scattering. Radar REMPI takes advantage of high-frequency microwave scattering from the region of laser-selected species ionization to extend REMPI to atmospheric pressures and implement it as a stand-off detection method for atomic and molecular species in combusting environments. Femtosecond laser electronic excitation tagging (FLEET) generates highly excited molecular species and dissociation through the focal zone of the laser. The prompt fluorescence from excited molecular species yields temperature profiles, and the delayed fluorescence from recombining atomic fragments yields velocity profiles.

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van der Mullen, Joost, Mariana Atanasova, Adam Obrusník, and Lenka Zajíčková. "Thomson scattering versus modeling of the microwave plasma torch: a long standing discrepancy almost solved." Journal of Analytical Atomic Spectrometry 35, no. 9 (2020): 2064–74. http://dx.doi.org/10.1039/d0ja00161a.

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This paper resolves a long standing discrepancy between theoretical modeling of atmospheric microwave plasma jets and their diagnostics by Thomson scattering. The discrepancy is found to be created by the filamentary behavior of the plasma.

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Ranjan, Apoorv, Adam Patel, Xingxing Wang, and Alexey Shashurin. "Thomson microwave scattering for diagnostics of small plasma objects enclosed within glass tubes." Review of Scientific Instruments 93, no. 11 (November 1, 2022): 113541. http://dx.doi.org/10.1063/5.0111685.

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In this work, coherent microwave scattering in the Thomson regime was demonstrated for small-scale plasmas enclosed within a glass tube and validated using a well-known hairpin resonator probe technique. The experiments were conducted in a DC discharge tube with a diameter of 1.5 cm and a length of 7 cm. Thomson microwave scattering (TMS) diagnostics yielded electron number densities of about 5.9 × 1010 cm−3, 2.8 × 1010 cm−3, and 1.8 × 1010 cm−3 for air pressures in the discharge tube of 0.2, 0.5, and 2.5 Torr, respectively. Measurements using the TMS technique were consistent across the tested microwave frequencies of 3–3.9 GHz within the margin of error associated with non-idealities of the IQ mixer utilized in the circuit. The corresponding densities measured with the hairpin resonator probe were 4.8 × 1010, 3.8 × 1010, and 2.6 × 1010 cm−3. Discrepancies between the two techniques were within 30% and can be attributed to inaccuracies in the sheath thickness estimation required for correct interpretation of the hairpin resonator probe results.

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Carbone, E. A. D., S. Hübner, J. M. Palomares, and J. J. A. M. van der Mullen. "The radial contraction of argon microwave plasmas studied by Thomson scattering." Journal of Physics D: Applied Physics 45, no. 34 (August 10, 2012): 345203. http://dx.doi.org/10.1088/0022-3727/45/34/345203.

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Minami, Takashi, Hisamichi Funaba, Kazumichi Narihara, Ichihiro Yamada, Hiroshi Hayashi, and Toshikazu Kohmoto. "Proposal ofin situdensity calibration for Thomson scattering measurement by microwave reflectometry." Review of Scientific Instruments 79, no. 10 (October 2008): 10F110. http://dx.doi.org/10.1063/1.2992520.

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Kentaro, Tomita, Yamamoto Naoji, Yamasaki Naoto, Tsuru Teppei, Uchino Kiichiro, and Nakashima Hideki. "Thomson-Scattering Diagnostics of Plasmas Produced in Miniature Microwave Discharge Ion Engine." Journal of Propulsion and Power 26, no. 2 (March 2010): 381–84. http://dx.doi.org/10.2514/1.39145.

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Abramovic, I., D. Moseev, T. Stange, S. Marsen, W. Kasparek, S. K. Nielsen, A. Tancetti, et al. "Optimization of the Collective Thomson scattering diagnostic for future operation." Journal of Instrumentation 14, no. 10 (October 1, 2019): C10021. http://dx.doi.org/10.1088/1748-0221/14/10/c10021.

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Collective Thomson scattering (CTS) is a microwave diagnostic allowing measurements of a number of plasma parameters such as the bulk ion temperature, the plasma composition, drift velocities and fast ion velocity distribution function. A CTS system has been successfully installed and commissioned on the Wendelstein 7-X (W7-X) stellarator. The measured spectra are analyzed by the means of the CTS forward model eCTS and the Minerva scientific framework enabling the use of Bayesian inference of relevant plasma parameters. Here we discuss the options for further optimization of the CTS diagnostic and focus on two topics of importance for the inference of bulk ion temperature values from CTS spectra: influence of impurities on the CTS spectra and the width of the notch filters that are employed to protect the receiver from high-power radiation. In addition to that we discuss the possibility of effective charge measurements by CTS. We explore the existence of an optimal notch filter width.

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Obrusník, A., P. Synek, S. Hübner, J. J. A. M. van der Mullen, L. Zajíčková, and S. Nijdam. "Coherent and incoherent Thomson scattering on an argon/hydrogen microwave plasma torch with transient behaviour." Plasma Sources Science and Technology 25, no. 5 (September 9, 2016): 055018. http://dx.doi.org/10.1088/0963-0252/25/5/055018.

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Aryshev, A., A. Araki, M. Fukuda, P. Karataev, G. Naumenko, A. Potylitsyn, K. Sakaue, L. Sukhikh, J. Urakawa, and D. Verigin. "Development of microwave and soft X-ray sources based on coherent radiation and Thomson scattering." Journal of Physics: Conference Series 236 (June 1, 2010): 012009. http://dx.doi.org/10.1088/1742-6596/236/1/012009.

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Shalashov, A. G., E. D. Gospodchikov, L. V. Lubyako, T. A. Khusainov, A. L. Solomakhin, and M. E. Viktorov. "Fast-Ion Diagnostics With Collective Thomson Scattering of Microwave Radiation for the GDT Open Magnetic Trap." Izvestiya vysshikh uchebnykh zavedenii. Radiofizika 65, no. 5-6 (2022): 353–69. http://dx.doi.org/10.52452/00213462_2022_65_05_353.

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14

Huang, M., D. S. Hanselman, Q. Jin, and G. M. Hieftje. "Non-thermal features of atmospheric-pressure argon and helium microwave-induced plasmas observed by laser-light Thomson scattering and Rayleigh scattering." Spectrochimica Acta Part B: Atomic Spectroscopy 45, no. 12 (January 1990): 1339–52. http://dx.doi.org/10.1016/0584-8547(90)80187-n.

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15

Hübner, S., J. M. Palomares, E. A. D. Carbone, and J. J. A. M. van der Mullen. "A power pulsed low-pressure argon microwave plasma investigated by Thomson scattering: evidence for molecular assisted recombination." Journal of Physics D: Applied Physics 45, no. 5 (January 19, 2012): 055203. http://dx.doi.org/10.1088/0022-3727/45/5/055203.

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16

Wilkinson, D. T., and F. Melchiorri. "2. Anisotropy of the blackbody radiation." Transactions of the International Astronomical Union 19, no. 1 (1985): 661–64. http://dx.doi.org/10.1017/s0251107x00006738.

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The 2.7 K microwave background radiation provides a sensitive probe of the universe in the interesting, but poorly understood, epoch around z ˜ 1000. At this time (age ~ 10 yr) the universe has cooled to T ~ 4000 K, the plasma combines, Thomson scattering ceases, and matter and blackbody radiation decouple. Subsequently, the radiation freely propagates to us, carrying the imprint of temperature fluctuations on the z ~ 1000 surface. The temperature fluctuations could have been caused by primordial density fluctuations, anisotropy in the expansion of the universe, or inhomogeneity in the initial temperature distribution; the z = 1000 surface we see was not causally connected at the time the radiation was released. Interpretation of the anisotropy measurements is complicated by the possibility that the matter may have been reionized (e.g. by massive stars), so the radiation may have been rescattered, possibly as late as z ~ 7.

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Yamamoto, N., K. Tomita, N. Yamasaki, T. Tsuru, T. Ezaki, Y. Kotani, K. Uchino, and H. Nakashima. "Measurements of electron density and temperature in a miniature microwave discharge ion thruster using laser Thomson scattering technique." Plasma Sources Science and Technology 19, no. 4 (June 15, 2010): 045009. http://dx.doi.org/10.1088/0963-0252/19/4/045009.

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18

Melia, Fulvio. "A Population III–Generated Dust Screen at z ∼ 16." Astrophysical Journal 941, no. 2 (December 1, 2022): 178. http://dx.doi.org/10.3847/1538-4357/aca412.

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Abstract The search for alternative cosmological models is largely motivated by the growing discordance between the predictions of ΛCDM and the ever-improving observations, such as the disparity in the value of H 0 measured at low and high redshifts. One model in particular, known as the R h = ct universe, has been highly successful in mitigating or removing all of the inconsistencies. In this picture, however, the anisotropies in the cosmic microwave background (CMB) would have emerged at a redshift z ∼ 16, rather than via fluctuations in the recombination zone at z ∼ 1080. We demonstrate here that a CMB created in the early universe, followed by scattering through a Population III–generated dust screen, is consistent with all of the current data. Indeed, the Planck measurements provide a hint of an ∼2%–4% frequency dependence in the CMB power spectrum, which would be naturally explained as a variation in the optical depth through the dust but not a Thomson scattering–dominated recombination environment. Upcoming measurements should be able to easily distinguish between these two scenarios, e.g., via the detection of recombination lines at z ∼ 1080, which would completely eliminate the dust-reprocessing idea.

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van der Mullen, J. J. A. M., M. J. van de Sande, N. de Vries, B. Broks, E. Iordanova, A. Gamero, J. Torres, and A. Sola. "Single-shot Thomson scattering on argon plasmas created by the Microwave Plasma Torch; evidence for a new plasma class." Spectrochimica Acta Part B: Atomic Spectroscopy 62, no. 10 (October 2007): 1135–46. http://dx.doi.org/10.1016/j.sab.2007.07.006.

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20

Holder, Gilbert P., Zoltan Haiman, Manoj Kaplinghat, and Lloyd Knox. "The Reionization History at High Redshifts. II. Estimating the Optical Depth to Thomson Scattering from Cosmic Microwave Background Polarization." Astrophysical Journal 595, no. 1 (September 20, 2003): 13–18. http://dx.doi.org/10.1086/377338.

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21

Kitazawa, Noriaki. "Reionization process dependence of the ratio of CMB polarization power spectra at low-ℓ." Journal of Cosmology and Astroparticle Physics 2022, no. 05 (May 1, 2022): 016. http://dx.doi.org/10.1088/1475-7516/2022/05/016.

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Abstract We investigate how much the ratio of cosmic microwave background (CMB) polarization power spectra CBB ℓ /CEE ℓ at low-ℓ (ℓ ≲ 10) depends on the process of reionization. Both such low-ℓ B-mode and E-mode polarization powers are dominantly produced by Thomson scattering of CMB photons off the free electrons which are produced in the process of reionization. Since the reionization should be finished until at least the redshift z ≃ 6 and the low-ℓ polarization powers are produced at late time, the ratio is rather insensitive by the ionization process at higher redshifts, but it is sensitive to the value of optical depth. The value of the ratio at ℓ = 2, however, is almost insensitive to the reionization process including the value of optical depth, and the value is approximately half of the value of tensor-to-scalar ratio. This fact can be utilized for future determination of tensor-to-scalar ratio in spite of the ambiguity due to cosmic variance.

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van der Mullen, Joost, Guillaume Boidin, and Marco van de Sandea. "High-resolution electron density and temperature maps of a microwave plasma torch measured with a 2-D Thomson scattering system." Spectrochimica Acta Part B: Atomic Spectroscopy 59, no. 7 (July 2004): 929–40. http://dx.doi.org/10.1016/j.sab.2004.04.004.

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Yoshikawa, M., J. Kohagura, Y. Shima, H. Nakanishi, T. Mouri, S. Suto, K. Nojiri, et al. "First electron temperature and density measurements of D-module plasma in GAMMA 10/PDX using Thomson scattering and microwave interferometer systems." Journal of Instrumentation 14, no. 06 (June 24, 2019): P06033. http://dx.doi.org/10.1088/1748-0221/14/06/p06033.

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Narishige, Soushi, Seiji Suzuki, Mark D. Bowden, Kiichiro Uchino, Katsunori Muraoka, Tadanori Sakoda, and Won Zoo Park. "Thomson Scattering Measurement of Electron Density and Temperature of a Microwave Plasma Produced in a Hydrogen Gas at a Moderate Pressure." Japanese Journal of Applied Physics 39, Part 1, No. 12A (December 15, 2000): 6732–36. http://dx.doi.org/10.1143/jjap.39.6732.

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MENZLER, ULF, and REINHARD SCHLICKEISER. "THE INFLUENCE OF PLASMA EFFECTS OF PAIR BEAMS ON THE INTERGALACTIC CASCADE EMISSION OF BLAZARS." International Journal of Modern Physics: Conference Series 28 (January 2014): 1460208. http://dx.doi.org/10.1142/s2010194514602087.

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The attenuation of TeV γ-rays from distant blazars by the extragalactic background light (EBL) produces relativistic electron-positron pair beams. It has been shown by Broderick et. al. (2012) and Schlickeiser et. al (2012) that a pair beam traversing the intergalactic medium is unstable to linear two-stream instabilities of both electrostatic and electromagnetic nature. While for strong blazars all free pair energy is dissipated in heating the intergalactic medium and a potential electromagnetic cascade via inverse-Compton scattering with the cosmic microwave background is suppressed, we investigate the case of weak blazars where the back reaction of generated electrostatic turbulence leads to a plateauing of the electron energy spectrum. In the ultra-relativistic Thomson limit we analytically calculate the inverse-Compton spectral energy distribution for both an unplateaued and a plateaued beam scenario, showing a peak reduction factor of Rpeak ≈ 0.345. This is consistent with the FERMI non-measurements of a GeV excess in the spectrum of EBL attenuated TeV blazars. Claims on the lower bound of the intergalactic magnetic field strengths, made by several authors neglecting plasma effects, are thus put into question.

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Hashimoto, Tetsuya, Tomotsugu Goto, Ting-Yi Lu, Alvina Y. L. On, Daryl Joe D. Santos, Seong Jin Kim, Ece Kilerci Eser, Simon C.-C. Ho, Tiger Y.-Y. Hsiao, and Leo Y.-W. Lin. "Revealing the cosmic reionization history with fast radio bursts in the era of Square Kilometre Array." Monthly Notices of the Royal Astronomical Society 502, no. 2 (January 23, 2021): 2346–55. http://dx.doi.org/10.1093/mnras/stab186.

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ABSTRACT Revealing the cosmic reionization history is at the frontier of extragalactic astronomy. The power spectrum of the cosmic microwave background (CMB) polarization can be used to constrain the reionization history. Here, we propose a CMB-independent method using fast radio bursts (FRBs) to directly measure the ionization fraction of the intergalactic medium (IGM) as a function of redshift. FRBs are new astronomical transients with millisecond time-scales. Their dispersion measure (DMIGM) is an indicator of the amount of ionized material in the IGM. Since the differential of DMIGM against redshift is proportional to the ionization fraction, our method allows us to directly measure the reionization history without any assumption on its functional shape. As a proof of concept, we constructed mock non-repeating FRB sources to be detected with the Square Kilometre Array, assuming three different reionization histories with the same optical depth of Thomson scattering. We considered three cases of redshift measurements: (A) spectroscopic redshift for all mock data, (B) spectroscopic redshift for 10 per cent of mock data, and (C) redshift estimated from an empirical relation of FRBs between their time-integrated luminosity and rest-frame intrinsic duration. In all cases, the reionization histories are consistently reconstructed from the mock FRB data using our method. Our results demonstrate the capability of future FRBs in constraining the reionization history.

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Beniamini, Paz, Pawan Kumar, Xiangcheng Ma, and Eliot Quataert. "Exploring the epoch of hydrogen reionization using FRBs." Monthly Notices of the Royal Astronomical Society 502, no. 4 (February 4, 2021): 5134–46. http://dx.doi.org/10.1093/mnras/stab309.

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ABSTRACT We describe three different methods for exploring the hydrogen reionization epoch using fast radio bursts (FRBs) and provide arguments for the existence of FRBs at high redshift (z). The simplest way, observationally, is to determine the maximum dispersion measure (DMmax) of FRBs for an ensemble that includes bursts during the reionization. The DMmax provides information regarding reionization much like the optical depth of the cosmic microwave background to Thomson scattering does, and it has the potential to be more accurate than constraints from Planck, if DMmax can be measured to a precision better than 500 pccm−3. Another method is to measure redshifts of about 40 FRBs between z of 6 and 10 with ${\sim}10{{\ \rm per\ cent}}$ accuracy to obtain the average electron density in four different z-bins with ${\sim}4{{\ \rm per\ cent}}$ accuracy. These two methods do not require knowledge of the FRB luminosity function and its possible redshift evolution. Finally, we show that the reionization history is reflected in the number of FRBs per unit DM, given a fluence limited survey of FRBs that includes bursts during the reionization epoch; we show using FIRE simulations that the contribution to DM from the FRB host galaxy and circumgalactic medium during the reionization era is a small fraction of the observed DM. This third method requires no redshift information but does require knowledge of the FRB luminosity function.

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Mirocha, Jordan, Henri Lamarre, and Adrian Liu. "Systematic uncertainties in models of the cosmic dawn." Monthly Notices of the Royal Astronomical Society 504, no. 2 (April 5, 2021): 1555–64. http://dx.doi.org/10.1093/mnras/stab949.

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ABSTRACT Models of the reionization and reheating of the intergalactic medium (IGM) at redshifts z ≳ 6 continue to grow more sophisticated in anticipation of near-future 21-cm, cosmic microwave background, and galaxy survey measurements. However, there are many potential sources of systematic uncertainty in models that could bias and/or degrade upcoming constraints if left unaccounted for. In this work, we examine three commonly ignored sources of uncertainty in models for the mean reionization and thermal histories of the IGM: the underlying cosmology, halo mass function (HMF), and choice of stellar population synthesis (SPS) model. We find that cosmological uncertainties affect the Thomson scattering optical depth at the few per cent level and the amplitude of the global 21-cm signal at the ∼5–10 mK level. The differences brought about by choice of HMF and SPS models are more dramatic, comparable to the 1σ error bar on τe and an ∼20 mK effect on the global 21-cm signal amplitude. Finally, we jointly fit galaxy luminosity functions and global 21-cm signals for all HMF/SPS combinations and find that (i) doing so requires additional free parameters to compensate for modelling systematics and (ii) the spread in constraints on parameters of interest for different HMF and SPS choices, assuming 5 mK noise in the global signal, is comparable to those obtained when adopting the 'true' HMF and SPS with ≳20 mK errors. Our work highlights the need for dedicated efforts to reduce modelling uncertainties in order to enable precision inference with future data sets.

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Minashin, Pavel V., and Alexander B. Kukushkin. "Spectral Intensity of Electron Cyclotron Radiation Emerging from the Plasma to the First Wall in ITER." Symmetry 15, no. 1 (December 31, 2022): 118. http://dx.doi.org/10.3390/sym15010118.

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It is predicted that in ITER, due to high values of electron temperature and magnetic field strength, electron cyclotron (EC) radiation emitted by plasma will be a significant source (together with external EC radiation injected for auxiliary plasma heating and non-inductive current drive) of additional thermal and electromagnetic loads for microwave and optical diagnostics. The spectral distribution of plasma EC radiation is particularly important to consider in millimeter-wave diagnostics, namely for high- and low-magnetic-field side reflectometry, plasma position reflectometry, and collective Thomson scattering diagnostic, because the transmission lines of these diagnostics yield the transport of EC waves emitted by the plasma. The development of semi-analytical methods used to describe the spectral distribution of plasma-generated EC radiation in tokamaks, starting from the work of S. Tamor, is based on the dominance of multiple reflections of this radiation from the first wall in a toroidal axially symmetric vacuum chamber. Here, we present calculations using the CYNEQ code of the spectral intensity of the EC radiation emerging from the plasma to the first wall and port plugs for five scenarios of ITER operation. This code uses the symmetry-based effect of approximate isotropy and homogeneity of radiation intensity in a substantial part of the phase space and has been successfully tested by comparison with first-principles codes. The energy flux density in the range of 30–200 kW/m2 is predicted for wall reflectance in the range of 0.6–0.95. The possible effect of this radiation on in-vessel components and diagnostics is assessed by calculating the surface density of the energy absorbed by various materials of the ITER first wall.

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Prokisch, C., A. M. Bilgic, E. Voges, J. A. C. Broekaert, J. Jonkers, M. van Sande, and J. A. M. van der Mullen. "Photographic plasma images and electron number density as well as electron temperature mappings of a plasma sustained with a modified argon microwave plasma torch (MPT) measured by spatially resolved Thomson scattering." Spectrochimica Acta Part B: Atomic Spectroscopy 54, no. 9 (September 1999): 1253–66. http://dx.doi.org/10.1016/s0584-8547(99)00074-9.

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Krachmalnicoff, N., and M. Tomasi. "Convolutional neural networks on the HEALPix sphere: a pixel-based algorithm and its application to CMB data analysis." Astronomy & Astrophysics 628 (August 2019): A129. http://dx.doi.org/10.1051/0004-6361/201935211.

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We describe a novel method for the application of convolutional neural networks (CNNs) to fields defined on the sphere, using the Hierarchical Equal Area Latitude Pixelization scheme (HEALPix). Specifically, we have developed a pixel-based approach to implement convolutional and pooling layers on the spherical surface, similarly to what is commonly done for CNNs applied to Euclidean space. The main advantage of our algorithm is to be fully integrable with existing, highly optimized libraries for NNs (e.g., PyTorch, TensorFlow, etc.). We present two applications of our method: (i) recognition of handwritten digits projected on the sphere; (ii) estimation of cosmological parameter from simulated maps of the cosmic microwave background (CMB). The latter represents the main target of this exploratory work, whose goal is to show the applicability of our CNN to CMB parameter estimation. We have built a simple NN architecture, consisting of four convolutional and pooling layers, and we have used it for all the applications explored herein. Concerning the recognition of handwritten digits, our CNN reaches an accuracy of ∼95%, comparable with other existing spherical CNNs, and this is true regardless of the position and orientation of the image on the sphere. For CMB-related applications, we tested the CNN on the estimation of a mock cosmological parameter, defining the angular scale at which the power spectrum of a Gaussian field projected on the sphere peaks. We estimated the value of this parameter directly from simulated maps, in several cases: temperature and polarization maps, presence of white noise, and partially covered maps. For temperature maps, the NN performances are comparable with those from standard spectrum-based Bayesian methods. For polarization, CNNs perform about a factor four worse than standard algorithms. Nonetheless, our results demonstrate, for the first time, that CNNs are able to extract information from polarization fields, both in full-sky and masked maps, and to distinguish between E and B-modes in pixel space. Lastly, we have applied our CNN to the estimation of the Thomson scattering optical depth at reionization (τ) from simulated CMB maps. Even without any specific optimization of the NN architecture, we reach an accuracy comparable with standard Bayesian methods. This work represents a first step towards the exploitation of NNs in CMB parameter estimation and demonstrates the feasibility of our approach.

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Galligani, Victoria Sol, Die Wang, Milagros Alvarez Imaz, Paola Salio, and Catherine Prigent. "Analysis and evaluation of WRF microphysical schemes for deep moist convection over south-eastern South America (SESA) using microwave satellite observations and radiative transfer simulations." Atmospheric Measurement Techniques 10, no. 10 (October 5, 2017): 3627–49. http://dx.doi.org/10.5194/amt-10-3627-2017.

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Abstract. In the present study, three meteorological events of extreme deep moist convection, characteristic of south-eastern South America, are considered to conduct a systematic evaluation of the microphysical parameterizations available in the Weather Research and Forecasting (WRF) model by undertaking a direct comparison between satellite-based simulated and observed microwave radiances. A research radiative transfer model, the Atmospheric Radiative Transfer Simulator (ARTS), is coupled with the WRF model under three different microphysical parameterizations (WSM6, WDM6 and Thompson schemes). Microwave radiometry has shown a promising ability in the characterization of frozen hydrometeors. At high microwave frequencies, however, frozen hydrometeors significantly scatter radiation, and the relationship between radiation and hydrometeor populations becomes very complex. The main difficulty in microwave remote sensing of frozen hydrometeor characterization is correctly characterizing this scattering signal due to the complex and variable nature of the size, composition and shape of frozen hydrometeors. The present study further aims at improving the understanding of frozen hydrometeor optical properties characteristic of deep moist convection events in south-eastern South America. In the present study, bulk optical properties are computed by integrating the single-scattering properties of the Liu(2008) discrete dipole approximation (DDA) single-scattering database across the particle size distributions parameterized by the different WRF schemes in a consistent manner, introducing the equal mass approach. The equal mass approach consists of describing the optical properties of the WRF snow and graupel hydrometeors with the optical properties of habits in the DDA database whose dimensions might be different (Dmax′) but whose mass is conserved. The performance of the radiative transfer simulations is evaluated by comparing the simulations with the available coincident microwave observations up to 190 GHz (with observations from Tropical Rainfall Measuring Mission's (TRMM) Microwave Imager (TMI), Microwave Humidity Sounder (MHS) and Special Sensor Microwave Imager/Sounder (SSMI/S)) using the χ2 test. Good agreement is obtained with all observations provided special care is taken to represent the scattering properties of the snow and graupel species.

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Qin, Yuxiang, Vivian Poulin, Andrei Mesinger, Bradley Greig, Steven Murray, and Jaehong Park. "Reionization inference from the CMB optical depth and E-mode polarization power spectra." Monthly Notices of the Royal Astronomical Society 499, no. 1 (July 22, 2020): 550–58. http://dx.doi.org/10.1093/mnras/staa2797.

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ABSTRACT The Epoch of Reionization (EoR) depends on the complex astrophysics governing the birth and evolution of the first galaxies and structures in the intergalactic medium. EoR models rely on cosmic microwave background (CMB) observations, and in particular the large-scale E-mode polarization power spectra (EE PS), to help constrain their highly uncertain parameters. However, rather than directly forward-modelling the EE PS, most EoR models are constrained using a summary statistic – the Thompson scattering optical depth, τe. Compressing CMB observations to τe requires adopting a basis set for the EoR history. The common choice is the unphysical, redshift-symmetric hyperbolic tangent (tanh) function, which differs in shape from physical EoR models based on hierarchical structure formation. Combining public EoR and CMB codes, 21cmfast and class, here we quantify how inference using the τe summary statistic impacts the resulting constraints on galaxy properties and EoR histories. Using the last Planck 2018 data release, we show that the marginalized constraints on the EoR history are more sensitive to the choice of the basis set (tanh versus physical model) than to the CMB likelihood statistic (τe versus PS). For example, EoR histories implied by the growth of structure show a small tail of partial reionization extending to higher redshifts. However, biases in inference using τe are negligible for the Planck 2018 data. Using EoR constraints from high-redshift observations including the quasar dark fraction, galaxy UV luminosity functions, and CMB EE PS, our physical model recovers $\tau _\mathrm{ e} = 0.0569_{-0.0066}^{+0.0081}$.

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Mourre, L., T. Condom, C. Junquas, T. Lebel, J. E. Sicart, R. Figueroa, and A. Cochachin. "Spatio-temporal assessment of WRF, TRMM and in situ precipitation data in a tropical mountain environment (Cordillera Blanca, Peru)." Hydrology and Earth System Sciences Discussions 12, no. 7 (July 9, 2015): 6635–81. http://dx.doi.org/10.5194/hessd-12-6635-2015.

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Abstract. The estimation of precipitation over the broad range of scales of interest for climatologists, meteorologists and hydrologists is challenging in high altitudes of tropical regions, where the spatial variability of precipitation is important while in situ measurements remain scarce largely due to operational constraints. Three different types of rainfall products – ground based, satellite derived, RCM outputs – are compared here during the hydrological year 2012/13 in order to retrieve rainfall patterns at time scales ranging from sub-daily to annual over a watershed of approximately 10 000 km2 in Peru. It is a high altitude catchment, located in the region of the Cordillera Blanca, with 41 % of its area above 4000 m a.s.l. and 340 km2 glaciated. Daily in situ data are interpolated using a kriging with external drift (KED) algorithm; the satellite product is TRMM 3B42, which incorporates monthly gauge data; RCM outputs are obtained from WRF run with a Thompson microphysical scheme at three nested resolutions: 27, 9 and 3 km. The performances of each product are assessed from a double perspective. A local comparison with gauge data is first carried out when relevant (diurnal and seasonal cycles, statistics of rainfall occurrence); then the ability of each product to reproduce some well-known spatial features of rain fields at various time scales (from annual down to daily) is analysed. WRF simulations largely overestimate the annual totals, especially at low spatial resolution, while reproducing correctly the diurnal cycle and locating the spots of heavy rainfall more realistically than either the ground-based KED or the TRMM products. The main weakness of the KED data is the production of annual rainfall maxima over the summit rather than on the slopes, induced by a lack of in situ data above 3800 m a.s.l. One main limitation of the TRMM product is its poor performance over ice-covered areas because ice on the ground behaves in a similar way as rain or ice drops in the atmosphere in term of scattering the microwave energy. While all three products are able to correctly represent the spatial rainfall patterns at the annual scale, it not surprisingly turns out that none of them meets the challenge of representing both accumulated quantities of precipitation and frequency of occurrence at the short time scales (sub-daily and daily) required for glacio-hydrological studies in this region. It is concluded that new methods should be used to merge various rainfall products so as to make the most of their respective strengths.

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Patel, Adam R., Apoorv Ranjan, Xingxing Wang, Mikhail N. Slipchenko, Mikhail N. Shneider, and Alexey Shashurin. "Thomson and collisional regimes of in-phase coherent microwave scattering off gaseous microplasmas." Scientific Reports 11, no. 1 (December 2021). http://dx.doi.org/10.1038/s41598-021-02500-y.

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AbstractThe total number of electrons in a classical microplasma can be non-intrusively measured through elastic in-phase coherent microwave scattering (CMS). Here, we establish a theoretical basis for the CMS diagnostic technique with an emphasis on Thomson and collisional scattering in short, thin unmagnetized plasma media. Experimental validation of the diagnostic is subsequently performed via linearly polarized, variable frequency (10.5–12 GHz) microwave scattering off laser induced 1–760 Torr air-based microplasmas (287.5 nm O2 resonant photoionization by ~ 5 ns, < 3 mJ pulses) with diverse ionization and collisional features. Namely, conducted studies include a verification of short-dipole-like radiation behavior, plasma volume imaging via ICCD photography, and measurements of relative phases, total scattering cross-sections, and total number of electrons $$N_{e}$$ N e in the generated plasma filaments following absolute calibration using a dielectric scattering sample. Findings of the paper suggest an ideality of CMS in the Thomson “free-electron” regime—where a detailed knowledge of plasma and collisional properties (which are often difficult to accurately characterize due to the potential influence of inhomogeneities, local temperatures and densities, present species, and so on) is unnecessary to extract $$N_{e}$$ N e from the scattered signal. The Thomson scattering regime of microwaves is further experimentally verified via measurements of the relative phase between the incident electric field and electron displacement.

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Patel, Adam R., Xingxing Wang, Erik L. Braun, Apoorv Ranjan, Mikhail Slipchenko, Sergey Macheret, Mikhail Shneider, and Alexey Shashurin. "Electron momentum-transfer collision frequency measurements in small plasma objects via Coherent Microwave Scattering." Plasma Sources Science and Technology, November 18, 2022. http://dx.doi.org/10.1088/1361-6595/aca430.

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Abstract We present the possibility of using coherent microwave scattering (CMS) for temporally resolved measurements of the electron momentum-transfer collision frequency in small plasma objects. Specifically, the electron collision frequency is inferred via phase information from microwave scattering off microplasmas operating in the mixed collisional-Thomson scattering regime. We further suggest the combination of phase and amplitude measurements to derive total electron count and temperature in small plasmas. An experimental validation of this concept is performed by 10.5 GHz CMS off laser-induced, variable-pressure oxygen and air plasmas.

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Vialetto, Luca, Alex van de Steeg, Pedro Viegas, Savino Longo, Gerard J. Van Rooij, Richard Van de Sanden, Jan van Dijk, and Paola Diomede. "Charged particle kinetics and gas heating in CO₂ microwave plasma contraction: comparisons of simulations and experiments." Plasma Sources Science and Technology, February 18, 2022. http://dx.doi.org/10.1088/1361-6595/ac56c5.

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Abstract This work investigates kinetics and transport of CO2 microwave plasmas through simulation results from a 1-D radial ﬂuid model and experiments. Simulation results are validated against spatially resolved measurements of neutral species mole fractions, gas temperature, electron number density and temperature obtained by means of Thomson and Raman scattering diagnostics, yielding good agreement. As such, the model is used to complement experiments and assess the main chemical reactions, mass and energy transport in diﬀuse and contracted plasma regimes. From model results, it is found that, as pressure is raised, the inhomogeneous gas heating induces signiﬁcant gradients in neutral and charged species mole fractions proﬁles. Moreover, the transition from diﬀuse to contracted plasma is accompanied by a change in the dominant charged species, which favours electron-ion recombination over dissociative attachment. Associative ionization rates increase in the plasma core from diﬀuse to contracted regime. These processes contribute to the increase in the peak electron number density with pressure, that determines radial plasma contraction.

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Ren, Tong, Ping Yang, Kevin Garrett, Yingtao Ma, Jiachen Ding, and James Coy. "A Microphysics-scheme Consistent Snow Optical Parameterization for the Community Radiative Transfer Model." Monthly Weather Review, October 26, 2022. http://dx.doi.org/10.1175/mwr-d-22-0145.1.

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Abstract The satellite observational data assimilation community requires consistent hydrometer descriptions—including mass-size relation and particle size distribution—to be used in both the forecast model and observation operator. We develop a microphysics scheme-consistent snow and graupel single-scattering property database to meet this requirement. In this database, snowflakes are modeled as a mixture of small column and large aggregated ice particles, the mixing ratios of which may be adjusted to satisfy a given mass-size relation. Snow single-scattering properties are computed for four different mass-size relations. Subsequently, the snow description in the Thompson microphysics scheme is used as an example to demonstrate how microphysics scheme-consistent snow bulk optical properties are derived. The Thompson scheme-consistent snow bulk optical properties are added to the Community Radiative Transfer Model (CRTM) version 2.4.0. With CloudSat Cloud Profiling Radar (CPR) snow and liquid precipitation retrievals as the inputs, CRTM simulations are performed over global oceans and compared with four collocated Global Precipitation Measurement (GPM) Microwave Imager (GMI) high-frequency channel observations. The CRTM simulated brightness temperatures show agreement with the GMI observed brightness temperatures in cases of light-to-moderate precipitation over extratropical and polar ice-free oceans, with root mean square errors (RMSEs) of 4.3, 13.0, 1.8, and 3.3 K in the 166 GHz (vertical polarization), 166 GHz (horizontal polarization), 183±3 GHz (vertical polarization), and 183±7 GHz (vertical polarization) channels, respectively. The result demonstrates the potential of using the newly developed microphysics scheme-consistent snow optical parameterization in data assimilation applications.

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Journal articles on the topic 'Thomson Microwave Scattering'

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