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The Follow-up X-ray telescope (FXT) is one of the instruments on board the Einstein Probe (EP) satellite of the Chinese Academy of Sciences (CAS) which was launched in January 2024. The EP mission is dedicated to the study of time-domain high-energy astrophysics, utilising a lobster-eye-based wide-field telescope, complemented by an eROSITA-like optics for follow-up observations. Max Planck Institute for Extraterrestrial Physics (MPE) has provided hardware and conducted measurement campaigns at its test facilities as part of a European contribution to Einstein Probe by ESA, and in addition the eROSITA flight spare mirror assembly as the second FXT module. Three FXT mirror assemblies – structural-thermal, qualification and flight models – have been manufactured. All components underwent acceptance testing using X-rays, followed by the installation of X-ray baffles for stray-light rejection. Subsequently, they underwent environmental tests and X-ray performance evaluations. The final tests of the qualification model, serving as a flight spare, and the flight model included an X-ray calibration at various photon energies ranging from about 0.3 keV to 8 keV. All tests were performed at MPE's test facilities: the laboratory for vibration and thermal-vacuum testing, and the PANTER X-ray facility. Reported are the setups and the results of the respective test sequences, focusing on the qualification and flight mirror assemblies. After delivery to China, all mirror assemblies were subjected to complementary measurements in the X-ray test facility of the Institute for High Energy Physics (IHEP) of CAS. • Design of the Follow-up X-ray telescope (FXT) on Einstein Probe. • FXT model philosophy and test matrix. • FXT X-ray test and calibration results. [ABSTRACT FROM AUTHOR]

The generation of ultrashort pulses is a hot topic in ultrafast physics. In the framework of classical electrodynamics, the process of nonlinear cross Thomson scattering which involves sideways radiation generation by a high-energy single electron cross-colliding with a tightly focused circularly polarized intense laser pulse is investigated through numerical simulation. For spatial limited tightly focused laser pulses, the laser delay time determines the position the electron interacts with, so precise control of the laser delay time to ensure the electron collides with the laser center is the key to obtaining high-power radiation. Through the research on the time evolution of electron radiation, it is found that the nonlinear cross Thomson scattering power is related to the coupling of electron velocity and its acceleration, where the increase of the electron velocity is critical to obtaining higher-power radiation. For off-axis electrons, the increase in deviation distance mainly leads to a decrease in radiation power, rather than pulse width and central photon energy. For low initial energy electrons, the asymmetry brought about by cross-collisions will improve the spatial collimation. For high-energy electrons, the asymmetry is weakened but the spatial collimation is enhanced. Using a single electron with an initial energy of 100 MeV and a laser pulse with an intensity of about 1. 25 × 1 0 19 W/cm 2 , 1. 5 zs hard X -rays can be generated. This study reveals part of the mechanism of nonlinear cross Thomson scattering and provides the theoretical basis and parameter suggestions for the design of the next generation ultrashort high-energy pulse generator. • Higher-order field development is derived for intense tightly focused laser pulses. • Delay time of laser determines the radiation when cross-colliding with an electron. • Radiation of moving electron is affected by the coupling of velocity and acceleration. • Laser–electron cross-collision potentially generates 1.5 zeptosecond hard X-rays. [ABSTRACT FROM AUTHOR]

• High-energy 532 nm laser designed for stable output of 10 Hz/3.5 j over 1000 s. • Tra grating is employed to enhance scattering light splitting efficiency. • Three-step image enhancement technique achieves 3000 counts/photon detection. • The measurement te range is 50 eV - 2 keV, error < 7 %. This paper presents the latest development of a tangential TVTS (Television Thomson scattering) system on the EAST Tokamak and the preliminary results obtained recently. For the goals of the thousand-second H-mode on EAST, it is obviously essential for the experimental operation and physical research to develop a high spatial resolution edge Thomson scattering diagnostic system. The new system uses a tangential optical path, mainly covering plasma ρ = 0.8 – 1.1 region. A high energy 532 nm laser was designed as the light source, which can realize the stable output of 10 Hz/3.5 J in the time of a thousand seconds through the new optical structure technology. In order to improve the scattering light splitting efficiency, the transmission grating is used as the main splitting device. We use a three-step image enhancement amplification technique so that the detection efficiency of the system can reach 3000 counts/photon. At present, the spatial resolution of the system is about 3 mm, and the measurement electron temperature (T e) range is 50 eV - 2 keV, the electron temperature error is expected <7 %. [ABSTRACT FROM AUTHOR]

The utilization of X-rays produced by interaction between relativistic electrons and laser pulses finds profound application in domains such as photoelectron spectroscopy. Through numerical simulation, the influence of the laser pulse delay time τ 0 and the initial Lorentz factor γ 0 on the spatial and spectral properties of radiation produced by electron cross collision with a circularly polarized laser pulse is investigated. Also, the optimal parameters for generating quasi-monochromatic pulses and high-order harmonic radiation are discussed. The results reveal that when | τ 0 | is large, the electron collides with the leading or trailing edge of the laser pulse, resulting in superior quasi-monochromatic radiation pulses. However, when τ 0 =0, the electron collides with the center of the laser pulse, which is most favorable for the generation of high-order harmonics. Furthermore, γ 0 has a negligible impact on the monochromaticity of the fundamental harmonic but plays a detrimental role in forming a single quasi-monochromatic pulse at higher values. Instead, higher γ 0 promotes the broadening of high-order harmonics. These results are important for obtaining radiating X-rays with different properties according to practical requirements. [ABSTRACT FROM AUTHOR]

Tritiated titanium targets were irradiated by the short-pulse OMEGA EP laser (1.25 kJ, 10 ps) to generate a laser-accelerated pulsed beam of tritons by target normal sheath acceleration. Using a Thomson parabola, the beam was found to contain 1012 tritons per pulse, with a mean energy of 2.2 MeV and an exponential tail reaching up to 10 MeV. In a separate experiment, the triton beam was directed onto a secondary deuterated polyethylene (CD) target to induce deuterium–tritium (D–T) nuclear reactions. Using neutron time-of-flight spectrometers, approximately 108 D–T fusion neutrons were observed per laser pulse. This triton beam presents new research opportunities for the study of the 3H(t, 2n)4He reaction and di-neutron transfers to lithium and beryllium that may produce exotic neutron-rich nuclei of interest to basic nuclear science, astrophysics, and inertial confinement fusion technology. [ABSTRACT FROM AUTHOR]

The Modulation Transfer Function (MTF) offers an objective measure to assess the imaging performance of streak cameras. This study aims to enhance the diagnostic precision of streak camera used in laser-driven inertial confinement fusion research. We introduce a novel method for evaluating the MTF of a recently developed large imaging area streak tube. This method integrates the electron optical MTF theory and the production of a reticle plate-type photocathode. Using ultraviolet and femtosecond lasers, we established two calibration platforms for the streak camera in both static and dynamic modes. We measured the radius of the electrons reaching fluorescent screen and obtained MTFs. Our findings reveal that the ultimate spatial resolutions at off-axis distances of 1.2, 4.7, 8.2, and 11.7mm are 28.5, 27.2, 26.4, 24.9 lp/mm (static) and 25.0, 22.8, 23.0, 21.2 lp/mm (dynamic). Notably, we successfully charted the ultimate spatial resolution distributions across the streak camera's full imaging area in both modes. • A novel method for calibrating the MTF of a large imaging area streak tube is reported. • The radius of the electrons reaching fluorescent screen and the static and dynamic MTFs are measured. • The ultimate spatial resolution distributions across the streak camera's full imaging area in both image modes are obtained. [ABSTRACT FROM AUTHOR]

• In the absence of ion temperature measurements, a technique often adopted in tokamak plasmas is to estimate the ion temperature by reverse engineering of the total neutron yield, assuming Maxwellian distributions for the ions. • When ICRH external heating is applied, the ion distributions are no longer Maxwellian. • An improvement of the procedure is proposed to account for Non-Maxwellian ion distributions in order to get a better estimate of the ion temperature. Accurate measurements of the ion and electron temperatures in tokamaks are essential for understanding the heating and transport properties of the plasma. While electron temperature measurements are readily available in most devices (e.g. with electron cyclotron emission or Thomson scattering diagnostics), ion temperature estimates usually require more sophisticated procedures such as charge-exchange recombination spectroscopy [ 1 ] or crystal spectroscopy [ 2 ]. In the absence of such dedicated ion temperature measurements, a technique often adopted in tokamak plasmas is to estimate the ion temperature by reverse engineering of the total neutron yield, assuming Maxwellian distributions for the ions. In the absence of external ion heating, this procedure is satisfactory since it mainly depends on the nuclear reaction cross sections and the bulk ion density, usually inferred from a combination of the electron density and the plasma dilution measurements. On the other hand, when Ion-Cyclotron Resonance Heating (ICRH) or Neutral-Beam Injection (NBI) is applied, the ion distribution functions are distorted and the Maxwellian representation used for the ion temperature estimate is not necessarily justified, typically leading to an overestimate of the thermal component of the ion temperature. By using a coupled wave / Fokker-Planck numerical solver to calculate the actual ion distribution functions under the influence of external heating and the resulting neutron yield, the fast and thermal components of the bulk ion distributions can be disentangled and a 'thermal-only' ion temperature consistent with the neutron measurements can be extracted. An example of this procedure for the WEST tokamak with ICRF heating will be presented and the differences between the results obtained with respect to the simplified Maxwellian-based procedure will be discussed. [ABSTRACT FROM AUTHOR]

Thomson scattering sources are known for generating quasi-monochromatic, high-brightness, and polarization-tunable X-rays, which are widely applied in fields such as fluorescence imaging, magnetic circular dichroism, and nuclear physics. In this paper, we present an experimental demonstration of polarization control at the Tsinghua Thomson scattering X-ray source (TTX) by adjusting the laser polarization. A specially designed Compton polarimeter is employed to effectively analyze the Degree of Linear Polarization (DoLP) of the X-rays produced at the TTX. Our results indicate that the DoLP of X-rays within a collecting angle of 1 / (3 γ) , where γ is the Lorentz factor of the relativistic electron, closely matches the DoLP of the laser. Furthermore, we demonstrate that the X-ray polarization can be continuously modulated from linear polarization to circular polarization by adjusting the laser polarization, which can significantly enhance the functionality and applicability of Thomson Scattering sources for scientific research. [ABSTRACT FROM AUTHOR]

The lobster eye lens uses square channels to reflect and converge light. It has no fixed optical axis and possesses advantages such as a broad field of view (FOV) and no chromatic aberration. Moreover, lobster eye lenses based on microporous optics manufacturing technology have been successfully applied to the spatial detection of soft X-ray spectra. Based on the penetrability of hard X-rays, lobster eye lenses can detect the perspective of hidden targets, which can be applied to fields such as safety inspection and industrial flaw detection. This study proposes an algorithm for comprehensive analysis of the imaging ability of a hard X-ray lobster eye lens, focusing on the stray rays transmitted by high-penetration X-rays. The simulation results showed that the point-spread function of the off-axis FOV is different. With the increase in the photon energy, the enhanced superposition effect of the cross-arm decreases the image contrast. Both the simulated and experimental images show that the image contrast decreases as the photon energy increases. The image contrast can be improved by adding more Pb to the materials used to create the lobster eye lens owing to the strong attenuation ability of Pb to X-rays. These results can contribute to the improvement of lobster eye lenses in X-ray backscatter imaging. • Lobster eye lenses can detect the perspective of hidden targets using hard X-rays. • We analyse imaging of a large-field-of-view hard X-ray lobster eye lens. • The analysis focuses on the stray light transmitted by high-penetration X-rays. • The image contrast can be improved by adding more Pb. • Findings contribute to improving lobster eye lenses in X-ray backscatter imaging. [ABSTRACT FROM AUTHOR]

The thermoluminescent material CaF 2 (Tm), known as TLD-300 (Harshaw/Bicron), shows a remarkable dependence of its glow curve shape on the quality of the radiation field. The quotient of high-temperature (maximum at about 265 °C) and low-temperature peaks (maximum at about 175 °C) depends strongly on LET (ions) and photon energy. The shape of the glow curve is parameterized by the high-to-low-temperature ratio, HLTR, a decreasing function of photon energy. Our goal has been to investigate the TLD-300 glow curve shape for six photon energies between 6 and 28 keV, and to apply this extended HLTR calibration to determine the effective energy of triboluminescence-generated X-rays (TGXs) produced when peeling adhesive tape in vacuum. For calibration, TLD-300 chips were exposed to X-rays from a W-anode tube (9.7–27.7 keV effective energies), X-rays from a Cu-anode tube (8.0 keV) and a 55Fe radioactive source (5.9 keV). The chips were subjected to an annealing protocol designed to improve the stability of the low-temperature peaks. Doses were low and deconvolution into 7 peaks was performed with custom-made software. For the TGXs investigation, TLD-300 chips and TLD-100 microcubes were exposed inside a vacuum chamber to radiation generated by the peeling of adhesive tape from its own backing. The dosimeters, located at different angular positions with respect to the tape, were covered with a 21-μm thick layer of Mylar (Dupont Tejjin Films) to eliminate stray radiation and block any UV light that may be emitted along with the TGXs. TLD-300 were thermally handled as in calibration, and the HLTR indicated the effective energy. Microcubes were used as monitors of a controlled exposure. The new calibration data confirmed the previous trend and showed consistency with existing HLTR measurements above 30 keV (after correcting by the different annealing procedures). The TGXs TLD-300 glow curves showed the presence of a low-temperature peak below those included in the usual deconvolution. The measured HLTR indicated effective energies close to 7 keV and constant over a wide range of observation angles. The extended calibration validates the use of this technique to evaluate photon energies below the limits investigated previously. For the investigation of TGXs, TLDs have been used as passive dosimeters, offering new possibilities in cases where pileup would be a limiting factor for active solid-state active detectors. The difference in glow curve shapes between the TGXs and the calibration photons offers a tool for further investigation of processes induced by surface electrification. • The glow curve shape of CaF 2 (Tm) depends on the incident energy. • The high-to-low-temperature ratio (HLTR) parameter quantifies glow curve shape. • Calibration of HLTR for x-ray energies extended to 5.9 keV–1250 keV. • Triboluminescence X-ray effective energy from peeling-off tape was (7.0 ± 0.9) keV. [ABSTRACT FROM AUTHOR]

Thomson scattering is one of the most important diagnostic methods for measuring plasma electron temperature (T e) and electron density (n e). In the diagnostic system, the polychromator is often used to analyze the spectral broadening and intensity of the detected scattered light. The performance of the avalanche photodiode (APD) used in the polychromator is greatly affected by the ambient temperature. The change of ambient temperature will seriously affect the accuracy of Thomson scattering diagnosis. Through experimental analysis, when the ambient temperature increases, the gain of APD will be significantly reduced, resulting in a significant deviation in electron density measurement. Taking the system response at an ambient temperature of 24.1 °C as reference, the deviation of electron density measurement varies from 43% to −16%, with the ambient temperature from 16.6 °C to 29.9 °C. However, the change of ambient temperature has little impact on the measurement of electron temperature. Detailed test of the polychromator shows that the estimated deviation of the electron temperature is within 3%. Due to the change of ambient temperature, the response of the detectors in each channel of the polychromator is inconsistent, which will cause random errors. The influence on electronic temperature calculation is analyzed by numerical simulation. [ABSTRACT FROM AUTHOR]

The ITER Core Plasma Thomson Scattering (CPTS) diagnostic system is designed to measure the electron temperature and density with an accuracy of 10 % and 5 %, respectively, at the Tokamak plasma core with a spatial resolution of 66 mm. A 1064 nm laser is injected into the vacuum vessel during the plasma pulse, where the laser light is scattered by the plasma electrons due to Thomson Scattering. The scattered light is collected and analysed to determine the electron temperature and density. The CPTS diagnostic PDR design proposes a complete, detailed and robust preliminary design, compliant with the system requirements and nuclear regulations. [ABSTRACT FROM AUTHOR]

• The dispersion interferometer based on CO 2 laser was developed for Globus-M2 tokamak. • Time resolution = 20 μs, spatial resolution = 0.02 m, measurement accuracy ≤ 1017 m −2. • During the year long operation, DI has proven to be reliable diagnostic at Globus-M2. • It is planned to use DI measurements for plasma density stabilizing in Globus-M2. The dispersion interferometry diagnostic (DI) based on the CO 2 -laser was commissioned at the Globus-M2 tokamak for absolute measurements of the line-integrated electron density (IED) along the chord in the equatorial plane. IED measurement error corresponding to the intrinsic noise of the acquisition device was below 1017 m −2 with time and spatial resolution 20µs and 2 cm, respectively. Inference of the IED using the second harmonic interference was done by means of spectral algorithm. Execution of the algorithm is performed at the FPGA in real-time mode. During the year long operation, DI was proven to be reliable and robust IED diagnostic at Globus-M2. [ABSTRACT FROM AUTHOR]

ITER Collective Thomson Scattering (CTS) diagnostic system is designed to analyze the alpha particles resulting from Deuterium-Tritium fusion reactions. It consists of one launcher and nine receiver transmission lines. The launcher line transports the high-power microwave emission of 1.2 MW from the gyrotron source to the front-end, while the receiver lines transport the collected microwave emission from the front-end and distribute it to the instrumentation in the Diagnostic Building. Due to the high power transported in the launcher line, it has to be water-cooled to minimize the thermal expansion resulting from the heating caused by the power losses. Therefore, this work primarily focuses on establishing the cooling system parameters for the launcher TL to ensure efficient dissipation of the ohmic losses, while meeting the ITER cooling requirements. Once the parameters of the water cooling system are defined, a thermo-mechanical analysis of the most critical components is performed to assess their temperature distribution and deformations. [ABSTRACT FROM AUTHOR]

• Escaped scattered light from multi-blade and V-groove laser dumps was analyzed. • Increasing depth of beam incidence into dump helps to suppress stray light. • V-groove with small angle can better suppress the escape of scattered light. • An optimal spacing for dump to minimize the intensity of escaping scattered light. Laser dump is an essential optical component in Thomson scattering diagnostic. Both multi-blade and V-grooved dumps can increase the ability of absorbing laser energy by using multiple surfaces to reduce the energy density on the wall surface. Still, the wall edges of the dump easily produce scattered light. The distribution and intensity of scattered light escaping from these two dumps, as well as the distribution and intensity of scattered light on the wall, are analyzed by the theory and simulation. In which an optical-mechanical simulation model of the laser dump was built. The results indicate that increasing the depth of the laser beam incident into the dump can decrease the distribution of escaping scattered light for these two dumps. When both the half-angle of V-groove and the incidence angle of beam on the entrance surface take a small amount, the V-grooved dump has an advantage of weaker escaping scattered light intensity, while there is a problem of heat accumulation at the bottom. For a fixed laser beam diameter, there is an optimal spacing for the dump to minimize the intensity of escaping scattered light. Additionally, the intensity of escaping scattered light is affected by the surface properties of dump, with low surface specular reflection resulting in low intensity. [ABSTRACT FROM AUTHOR]

• Collective Thomson scattering is a powerful diagnostic for ion measurements on DEMO. • Measurements of fusion alpha dynamics in the core of DEMO can be achieved by CTS. • Several DEMO plasma control parameters can be obtained by a CTS diagnostic. Diagnostic systems are essential for burning plasma control and operation of DEMO, but are at the same time challenging in terms of design and integration. The harsh environment around the DEMO plasma, and the space restrictions and need to maximize the first-wall area used for tritium breeding, set limitations on the number and type of diagnostics to be installed. This will focus the efforts on diagnostics needed for control of the DEMO plasma. The robustness and versatility of a microwave-based Collective Thomson Scattering (CTS) diagnostic make it worthwhile to investigate the potential of a DEMO CTS diagnostic. We present the initial exploratory effort on this. The study builds on the experience of existing CTS experiments on e.g. ASDEX Upgrade, and on the recent development of the ITER CTS system, which focuses on measurements of fast ion dynamics in the burning ITER plasma. The initial target of the DEMO CTS diagnostic was to use an Electron Cyclotron Resonance Heating (ECRH) gyrotron beam as the probing source, with the receiving quasi-optical system being a dedicated CTS setup. Based on raytracing calculations including signal-to-noise estimates, it is found that such a setup is not viable. Here, we present studies of alternative solutions, including assessments of which DEMO plasma parameters the CTS diagnostic may contribute to determine. [ABSTRACT FROM AUTHOR]

In-situ Rb-Sr dating of mica by laser ablation ICP-MS/MS has recently emerged as a new tool to date a range of geological processes including magmatic, metamorphic and hydrothermal events. The majority of age results presented to date are based on Rb/Sr calibration using the MicaMG pressed nano-powder pellet. However, some studies have reported low accuracy associated with mica Rb-Sr ages using this method, which are attributed to the different ablation properties of MicaMG and natural mica. In this work, we document the results of a systematic comparison between isotope-dilution and laser-ablation Rb/Sr ages of micas in Cretaceous diamondiferous kimberlites from Bultfontein (South Africa), Koidu and Tonguma (Sierra Leone), with additional in-situ data for the Mt. Dromedary mica (Australia). We adopt two different analytical strategies. While NIST610 SRM is employed to calibrate 87Sr/86Sr in both cases, the first approach follows the convention to utilise MicaMG as calibration material for Rb/Sr. In the second approach, Rb/Sr quantification is initially undertaken with NIST610, with a subsequent correction for Rb/Sr offset based on the age of isochronous micas (WBLK) from the Cretaceous Wimbledon lamproite (South Africa). We show that, using our instrumental set-up, employment of MicaMG as Rb/Sr calibration material commonly provides inaccurate results (generally 5–10% older than the solution-based ages). Conversely, our new approach returns accurate ages (within 3%) and represents a promising avenue to improve the accuracy of mica Rb-Sr age by laser ablation ICP-MS/MS especially once isochronous mica reference materials will be developed. Application of this methodology to multiple samples from Koidu and Tonguma shows that, contrarily to previous inferences based on age-dating of fewer samples, magmatism occurred at both localities in the 145–151 Ma interval. After a temporal hiatus, magmatism restarted exclusively in the Tonguma cluster between 135 and 139 Ma. The relative volumetric importance of these two magmatic stages in the Tonguma diamond mine awaits further evaluation. [ABSTRACT FROM AUTHOR]

Experiments creating extreme states of matter almost invariably create non-equilibrium states. These are very interesting in their own right but need to be understood even if the ultimate goal is to probe high-pressure or high-temperature equilibrium properties like the equation of state. Here, we report on the capabilities of the newly developed imaginary time correlation function (ITCF) technique [1] to detect and quantify non-equilibrium in pump-probe experiments fielding time resolved x-ray scattering diagnostics. We find a high sensitivity of the ITCF even to a small fraction of non-equilibrium electrons in the Wigner distribution. The behavior of the ITCF technique is such that modern lasers and detectors should be able to trace the non-equilibrium relaxation from tens of femto-seconds to several 10s of picoseconds without the need for a model. • The newly developed imaginary time correlation function technique can detect and quantify non-equilibrium in pump-probe experiments. • Time resolved x-ray Thomson scattering is sensitive to a small fraction of non-equilibrium electrons in the Wigner distribution. • Modern setups will allow to trace the relaxation from tens of femto-seconds to several 10s of picoseconds without a model. [ABSTRACT FROM AUTHOR]

• Self-calibration laser energy measurement system based on embedded thin foil curved resistance and centralized controlling, which improves thousands of laser energy meters in-situ self-calibration efficiency. • Mathematical model of the whole measurement and calibration were established and verified by experiments. • The system's calibration linearity is 0.9% at 400 mJ − 20 J and 1% at 500 mJ − 20 J. Precise real-time measurement of high-power laser energy is the foundation for ICF facilities to keep power and energy balance, which requires energy measurement equipment to maintain considerable linearity during a long operation period. The measurement accuracy, efficiency and calibration procedure stability were the key factors for ICF facilities' operation. This work proposed a new thermopile-type energy meter and calibration system to achieve high-precise in-situ measurement and calibrating of high-power laser energy. The study suggested that the thermal energy conversion, electric energy loading and metering, heat transfer, sensor temperature rise, sampling circuit and post-processing significantly affected the high-power laser energy measurement and calibration results. Besides, the whole numerical modeling process was established and verified by experiments on the energy transfer and physical quantity conversion process in energy measurement. The laser energy measurement and calibration system has self-calibration functions and stable operation through numerical simulation and optimization of the key factors. This study is of great significance for the high-power laser energy monitoring and output energy improvement of ICF facilities, broadening the method for the high-precision in-situ measurement system. [ABSTRACT FROM AUTHOR]

X-ray photons attenuation characteristics for the two tellarite based glasses Bi 2 O 3 – B 2 O 3 – TeO 2 – TiO 2 and PbO–ZnO–TeO 2 –B 2 O 3 have been investigated at dental diagnostic energies (between 30-80 keV) using Geant4 code and WinXcom software. The correlation coefficient (R2) is utilized to evaluate the extent to which Geant4 results are related to the WinXcom data. For the both series, R2 is close to 1 for all samples and this implies a perfect degree of association between the Geant4 and WinXcom data. The linear attenuation coefficient is proportionally increased with addition of TeO 2 in both series, which implies that there is a decreasing tendency in the X-ray photon transmission corresponding with an increase in the TeO 2 content in the glasses. The half value layer (HVL) decreases as the density increases and this decreasing is very notable at 70 and 80 keV. The maximum HVL for all samples occurs at 80 keV and this implies that the HVL gradually increases as the energy of the X-ray photons increase. Also, the increment of TO 2 in the glasses (in both systems) leads to reduce the mean free path and BiTeTi6 and PbTeB6 samples have the lowest MFP. The MFP for both systems was compared with three heavy concretes and the comparison revealed that the selected systems can be utilized to fabricate protection masks used during diagnostic radiation of the head or oral cavity. [ABSTRACT FROM AUTHOR]

• The laser-induced fluorescence diagnostic system for measuring the ITER divertor plasma parameters is described. • The LIF spectroscopic schemes and lasers are chosen for measurements of HeII density and temperature. • The LIF and background signals and the relative accuracies are calculated for both He and DT discharges of ITER. Laser-induced fluorescence (LIF) on ITER will be used for local measurement of helium density n He and ion temperature T i in divertor. The LIF diagnostic is combined with the divertor Thomson scattering (DTS) via common laser injection and signal collection optics. Collisional-radiative model developed for helium ions is used to estimate laser parameters required for robust measurement of laser-induced signals against plasma background radiation. The estimations demonstrate feasibility of measuring n HeII with laser parameters provided by available optical parametric oscillator pumped by Nd:YAG. New approach for measuring T i is proposed and the expected errors are estimated using numerical simulations. [ABSTRACT FROM AUTHOR]

• New design of the Divertor Thomson Scattering is presented. • Electromagnetic and contact analyses are conducted. • Conclusions about the obtained stresses and construction survivability are made. This article reports the results of the assessment performed on the ITER Divertor Thomson Scattering (DTS). It is designed to provide an instrument capable of measuring the electron temperature and the related density profiles in the outer divertor plasma, relying on Thomson scattering method. The DTS main components are front rack, back rack, neutron shielding and diagnostic mirrors. Current DTS design has been modified compared to the one described in the previous article dedicated to this object. The most significant changes are: • Upper neutron shielding has been removed. It is now not connected directly with the DTS system. It helped to reduce total weight of the construction; • Dielectric insertions were added in order to reduce influence of the ponderomotive forces on construction strength; • DTS supports were redesigned. Connections of the DTS with radial rails on which the construction is mounted on the sides were explored. Corresponding contact problem was solved and the structure integrity in this area was assessed. Mirrors made of SiC material are the DTS diagnostic elements. They are installed into front and back diagnostic racks. Other elements of the DTS are made of 316L(N)-IG steel. The contact pads on the radial rails are made of 660 steel. The whole Divertor Thomson Scattering system has to withstand all the loads (thermal, mechanical, electromagnetic and seismic) acting on the in-vessel region in which it is located without compromising its integrity. Its design layout is being modified and optimized according to the outcome of the structural assessment. Every step of the design update brings the construction closer to satisfying all of the criterions of structural integrity. This paper describes some important steps that really help moving forward to the DTS implementation. [ABSTRACT FROM AUTHOR]

• Lasers require high power and enough beam quality. • A beam homogenizer providing super-Gaussian can be used for amplifications. • The homogenizer sustains long sustained distance with non-peaked profile. • A deformable mirror improves wavefront surface for enough beam quality. This paper suggests the use of two optical elements for laser transfer in Thomson scattering diagnostics, which are widely used for other laser applications. YAG lasers amplified by flash lamps (repetition frequency of 50–100 Hz having a few Joules output) can sometimes have adverse effects such as peaked beam profiles and wavefront distortion. We used a beam homogenizer, which is a refractive optical element, to change the beam profile from peaked to non-peaked at a designated position. Using a super-Gaussian output profile when amplifying lasers facilitated longer—by a factor of 1.5 (=300 mm/200 mm) compared with top-hat beam profile—sustained distances, i.e. the distance along the laser path having a non-peaked profile. In terms of beam quality, wavefront distortion broke the beam profile in the far field. We used a deformable mirror to correct and flatten the wavefront of the beam. A YAG laser having a wavefront distortion of 0.46 λ peak-to-valley was used to test the application of the deformable mirror, the results of which improved wavefront distortion to a wavelength of 0.1 λ peak-to-valley. [ABSTRACT FROM AUTHOR]

• Upgrade of Thomson scattering system on VEST has been performed. • The laser input power is increased up to 2.8 times by injection system improvement. • Optical fiber bundle replaces a single core fiber to increase the signal level 2.1 times. • Oscilloscope envelope mode is utilized to measure periodic large data for each burst. • Time resolution is improved to 1 ms with new burst laser and fast DAQ systems. A Thomson scattering diagnostic system was developed and successfully measured electron temperature and density of core plasma (R = 0.35 m) in Versatile Experiment Spherical Torus (VEST). However, the current system is able to measure only a single time point in a shot. Therefore, upgrade of the Thomson scattering system has been prepared and is in progress to obtain the time evolution. The upgrade is focused on three parts. First, the laser injection system is improved by introducing a burst mode laser with the energy of 2 J and repetition rate of 1 kHz for 10 ms. Furthermore, the laser injection optics is improved to minimize the optical loss. Second, minimum etendue limit of the collection optics is increased by employing a fiber bundle of three single-core fibers. Finally, a data acquisition system is prepared to record the burst laser signals for high sampling rate. Oscilloscope envelope mode is adopted and tested for measuring ten burst laser signal with 1.25 GS/s. Through the upgrade, the time evolution of electron temperature and density is expected to be measured in a single shot with enhanced signal-to-noise ratio. [ABSTRACT FROM AUTHOR]

• The use of diode pumping in 2 J × 50 Hz 3 ns Nd:YAG laser improve beam quality. • Cavity dumping approach in 946 nm Nd:YAG laser allow to obtain 3 ns pulse duration. • Zero diffraction length Regenerative Amplifier allow to reach 1 J in 946 nm Nd:YAG. • Image-rotation in Regenerative Power Amplifier significantly improves beam quality. We developed high energy Q-switched 1064 nm and 946 nm Nd:YAG lasers for ITER Divertor Thomson Scattering (DTS). The 1064 nm Nd:YAG laser is designed to be used as the main DTS probing laser and features output energy of 2 J at 3 ns pulse duration. MOPA configuration with phase conjugation mirror provides divergence of 1.3 times the diffraction limit and high stability of the output beam parameters with repetition rate varied from 1 to 50 Hz. The 946 nm Nd:YAG laser designed for calibration by an auxiliary Thomson spectrum at the neighboring wavelength. The 946 nm laser consists of MO based on cavity dumping, high gain regenerative preamplifier and zero diffraction length ring cavity regenerative power amplifier with image-rotation providing 1 J × 50 Hz at 3 ns pulse duration with divergence of 1.5 the diffraction limit. As far as we know this is the highest value of the output energy obtained at 946 nm with nanosecond pulse duration until now. Both lasers use unified pump modules providing high maintainability of the system. The paper describes laser design approaches, state of the art and outlook of further developments. [ABSTRACT FROM AUTHOR]

A novel application of strip and pixel silicon radiation detectors for study and characterization of run-away electron events in tokamaks is presented. Main goal was to monitor runaway electrons both directly and indirectly. The strip detector was placed inside the tokamak vacuum chamber in order to monitor the run-away electrons directly. Whereas the pixel detector was placed outside the tokamak chamber behind a pin hole for monitoring the run-away electrons indirectly via radiation produce by interaction of the electrons with the plasma facing material. Results obtained using the silicon detectors are compared with already existing diagnostic methods consisting of scintillation devices detecting X-rays and photo-neutrons, providing the same results in the observable comparisons. Tests with the pixel detector proved that the pinhole camera is able to extract spatial information of interaction point (a place where the runaway electrons hit on the facing material) and the strip detectors indicate presence of additional signal from throughout the discharge. The performed experiments are innovative, illustrating possible development of new and easy to use diagnostic method. [ABSTRACT FROM AUTHOR]

Cobalt matrix carbides are favorite cases of wear and corrosion-resistant coatings. Among thermal spray processes the high-velocity oxy-fuel (HVOF) spraying is a popular choice because of its unique properties. In this paper the effect of particles' temperature on the porosity, corrosion as well as wear behavior of high-velocity oxy-fuel (HVOF) thermally sprayed WC-12Co coating has been studied. The temperature of particles was measured using a Spray-Watch diagnostic system. Also the scanning electron microscopy (SEM), image analysis, and X-ray diffraction (XRD) were used for examining the powder and the coating. The corrosion potential and corrosion current density was evaluated using potentio-dynamic polarization test. Results show that the porosity is affected by thermal flow on the coating surface. Besides, a higher particle temperature resulted in achieving more amorphous phases and eventually the higher corrosion resistance. Sample A was coated with an impact temperature of 2012.4 °C. Although the porosity was higher than other sprayed samples (1.7%), the higher content of amorphous phase led to recording a higher corrosion resistance (64.3E-6A). Sample B was coated with an impact temperature of 1880 °C for which the Jcorr was 67.2E-6 A. Sample C was sprayed with a low impact temperature of 1702 °C for which a surface porosity of 1% and the low corrosion resistance of 79.5E-6A were recorded. Based on the experiments it was concluded that for the WC-12Co coating the corrosion resistant phases have the dominant influences on the corrosion resistance. [ABSTRACT FROM AUTHOR]

Laser Thomson scattering and Rayleigh scattering methods were applied to investigate the dynamics of laser-induced plasmas in atmospheric air. Laser-induced plasma was generated by a 1064 nm, 200 mJ Nd: YAG laser. Another nanosecond Nd: YAG laser (532 nm, 50 mJ) was used as the probe laser. The temporally and spatially resolved electron number density and temperature distributions of the laser-induced plasma were determined from the Thomson scattering spectra. From 1 μs to 21 μs after plasma generation, the electron number density around the centre of the plasma decreased from 4.96 × 1023m‐3 to approximately 1.1 × 1021m‐3, while the electron temperature dropped from approximately 51,500 K to 6900 K. The plasma images and the measured distribution of the electron number density and temperature indicated the formation of a toroidal structure approximately 18 μs after plasma generation. The Rayleigh scattering results show that the Taylor-Sedov model cannot well describe the early evolution of the shockwave in radial directions. Unlabelled Image • Spatially resolved measurement of electron number density and temperature. • Shockwave in the radial direction poorly agrees with the Taylor-Sedov model. • Detailed analysis for the generation and development of toroidal structure. [ABSTRACT FROM AUTHOR]

The new way of generating the attosecond pulses via Thomson scattering of linear polarization Gaussian beam propagating on solid surface is investigated. It is found that a single attosecond laser pulse is generated which renders the appropriate strength electrostatic field to the environment. After studying the influence of the strength of the electrostatic field on it, the results show that a single attosecond pulse is generated when intensity of Gaussian beam is 5 and intensity of the electrostatic field is E s = 5 ×10−4, which is more intense and direction simplification. [ABSTRACT FROM AUTHOR]

Diagnostic and therapeutic nanoparticles have been actively investigated for the last few decades as new platforms for biomedical applications. Despite their great versatility and potency, nanoparticles have generally required further modification with biocompatible materials such as biopolymers and synthetic polymers for in vivo administration to improve their biological functions, stability, and biocompatibility. Among a variety of natural and synthetic biomaterials, hyaluronate (HA) has been considered a promising biomolecule with which to construct nanohybrid systems, as it can enable long-term and efficient delivery of nanoparticles to target sites as well as physiological stabilization of nanoparticles by forming hydrophilic shells. In this review, we first describe various kinds of HA derivatives and their interactions with nanoparticles, and discuss how to design and develop optimal HA-nanoparticle hybrid systems for biomedical applications. Furthermore, we show several exemplary applications of HA-nanoparticle hybrid systems and provide our perspectives to their futuristic translational applications. Unlabelled Image • Hyaluronate (HA) is used to construct multifunctional nanohybrid systems. • HA enables the long-term and facilitated delivery of nanoparticles to target sites. • HA-nanoparticle systems can be used for diagnostic, therapeutic and theranostic applications. • HA-based nanohybrid systems seem promising for further clinical applications. [ABSTRACT FROM AUTHOR]

A Thomson scattering (TS) system has been developed on Versatile Experiment Spherical Torus (VEST) to measure the electron temperature and the density. In VEST, it is quite challenging to measure TS signals because the energy of the utilized pulsed laser and the target electron density are low, 0.85 J and ∼5 × 1018 m−3, respectively. Furthermore, the difficulties caused by filter specifications have to be resolved because of the use of commercial interference filters with broad bandwidth and poor blocking at the laser wavelength. Therefore, we especially optimize the placement order of the filter sets based on the evaluation of the relative errors to overcome the poor spectral resolution. In addition, the amount of the stray light that penetrating filters is reduced by vacuum components such as baffles, louvres, and a viewing dump. With the careful installation and the optimization of the system, we can develop an efficient Thomson scattering system. Recently, TS signals have been successfully measured from the ohmic plasmas, and the electron temperature and the density are determined by analyzing the signals with the Bayesian method. [ABSTRACT FROM AUTHOR]

Highlights • Measurements of magnetic island and ECCD locations are essential for NTM suppression. • Many control systems rely on diagnostics which may not be robust to neutron radiation. • Magnetic island and ECCD locations are both found with a single ECE diagnostic. • The modified Rutherford equation is used to demonstrate the effect of ECCD alignment. Abstract Accurate real-time measurements of magnetic island and electron cyclotron current drive (ECCD) locations are essential for efficient suppression of the neoclassical tearing mode (NTM). To determine these locations, many control systems rely on motional Stark effect constrained equilibria reconstruction and real-time Thomson scattering with TORBEAM current drive evaluation and therefore require time-intensive cross-calibration of at least two different diagnostics. Here we present a simpler, proof-of-concept analysis that uses only a single diagnostic (a radial array electron cyclotron emission radiometer) for the simultaneous determination of both the radial position of a magnetic island and the deposition location of ECCD. Measurements are compared with the modified Rutherford equation to demonstrate the effect of ECCD alignment on NTM suppression. [ABSTRACT FROM AUTHOR]

Highlights • The CTS diagnostic system is being designed to be installed in ITER. • The CTS system will provide spatial and temporal measurements of plasma parameters. • Preliminary thermo-structural analyses were performed on four in vessel components. • The results indicate that active cooling will be required on the components. Abstract The Collective Thomson Scattering (CTS) diagnostic system will be used at ITER to provide spatial and temporal measurements of fast ion velocity distributions. The diagnostic is based on the CTS principle, where a microwave beam scatters off electrons in the plasma. The scattered radiation is then collected and measured, providing information about the fast ions. The system components are either considered in-vessel or ex-vessel depending on their location in the port plug. In this work, thermo-structural analyses were performed on four in-vessel components using the finite-element method (FEM) and the commercial software ANSYS Mechanical v18.0. The analyses indicate that active cooling will be required for most of the analysed components. The thermal stresses will be used to perform the structural assessment of these components based on the RCC-MR code. [ABSTRACT FROM AUTHOR]

• A method of 3D reconstruction for LPBF parts by light field camera is proposed. • Simple and high-precision calibration is achieved by the consistency method. • A LFEPI-Unet is designed for accuracy disparity reconstruction. • Accurately mapping of disparity, depth, and 3D spatial coordinates is established. • First-time application for in situ 3D reconstruction and monitoring of LPBF parts. The assessment of output quality in the laser powder bed fusion process entails the analysis of the three-dimensional morphology of the manufactured parts, which plays a crucial role in quality control to prevent metallurgical defects. This study proposes a novel approach of three-dimensional reconstruction for laser powder bed fusion parts using a light field camera. Initially, a consistency method for high-precision camera calibration was explored to determine the virtual camera pixel size and coefficient of effective focal length of light field camera. Subsequently, the model based light field epipolar-plane image Unet is designed to obtain disparity information without any data augmentation techniques. By leveraging both binocular and light field optical paths, a robust mapping relationship of the disparity, depth, and visually coherent three-dimensional contour was established. Finally, the three-dimensional contours of laser powder bed fusion parts were reconstructed by the established mapping with a single exposure of the light field camera. The proposed method enables three-dimensional contour visualization of laser powder bed fusion parts from multi-view perspectives, which facilitates in situ monitoring of the spattering distance, three-dimensional spatial points and lines of the printed layers and contours of printed parts. With a calibration error of 50 μm and resolution of 180 μm for the light field camera (Lytro illum camera), the maximum relative and absolute errors between reconstructed three-dimensional spatial points were 4.33 % and 260 μm respectively when compared with theoretical dimension, and 0.5 % and 210 μm respectively when compared with manufactured dimension. The maximum root-mean-square error of reconstructed three-dimensional contour surfaces was found to be 1.55 mm. This study represents the first application of a light field camera for in situ three-dimensional reconstruction of laser powder bed fusion parts, which notably can be obtained from only a single round of calibration and exposure, enabling seamless monitoring of their surface morphology and facilitating online quality control. These advancements have vast potential for enhancing high-end additive manufacturing. [ABSTRACT FROM AUTHOR]

This paper reports the development of a method of using incoherent laser Thomson scattering (LTS) to directly measure the electron velocity distribution function (EVDF) within a plasma plume. In this method, a 532 nm wavelength laser is injected into a plasma and Thomson scattering is detected with a CCD camera and a triple-monochromator. First, the measurement settings (e.g., laser power, number of integrations, and data analysis) were validated through a comparison between a microwave cathode and a hollow cathode. The results indicate that lower laser power is required as the photo-ionization from the metastable state particles increases the Thomson scattering. Second, the EVDFs of the microwave cathode at the plume were investigated for various anode currents and propellant flow rates. The results suggest that the non-Maxwellian EVDF was clearly observed at the low propellant flow rate, and the propellant flow rate is a more important parameter for the non-Maxwellian EVDFs than the anode current. • Electrons at a hollow and microwave cathode's plume region were measured. • Electron properties were acquired by incoherent laser Thomson scattering. • Effects of laser power on photo-ionization were evaluated in both cathodes. • Measurements were conducted under various anode currents and propellant flow rates. • Non-Maxwellian distributions were observed in the microwave cathode plume. [ABSTRACT FROM AUTHOR]

The Southern European Thomson back-scattering source for Applied Research (STAR) is a high-energy photon facility located on the campus of the University of Calabria (UniCal). The facility was designed for its first phase to operate with an electron and photon energy up to 85 MeV and 140 keV respectively. For the second phase of the project the energy of the electrons, and thereby the photons, would be increased up to 150 MeV and 350 keV respectively. The Italian Institute for Nuclear Physics (INFN) was awarded the project for installing, testing, and commissioning the energy upgrade of the electron beamline. In this article, we will outline the progress of this upgrade. In particular the completion of the site acceptance test of the RF system and the IT infrastructure combined with the control system software. [ABSTRACT FROM AUTHOR]

Lithium fluoride crystals are used to assess proton-beam energy spectra. Proton irradiation induces laser-active color centers in the crystal, whose density correlates with the absorbed dose. The spatial distribution of photoluminescence emitted by these color centers is exploited to estimate the proton-beam energy spectrum using an analytical Bragg-curve model. This study integrates the effects of multiple Coulomb scattering (MCS) into the model. At high enough energies, MCS leads to proton leakage through the crystal faces with a reduction in absorbed dose along the crystal length. The model incorporates MCS using an empirical approach based on Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

• Isotactic chiral phononic crystals for a low-frequency and broad bandgap. • Comparing the bandgap properties of the isotactic and syndiotactic chiral phononic crystals. • Illuminating an extremely simplified geometry of Thomson Scattering-induced bandgap by a practical example. • The numerical and experimental demonstration for the Thomson Scattering-induced continuous bandgap. Realizing a low-frequency and broad bandgap is extremely challenging because the lattice constant, equivalent stiffness, and equivalent density must be taken into account in practice. Despite the advances of inertial amplification which is one of the ideal strategies to address this issue, the design ideas are mainly limited to the classic geometries featured by mirror symmetry (syndiotacticity), confining then progress in this topic. Here, we report numerical and experimental investigation of a chiral phononic crystal without mirror symmetry (isotacticity) according to the analogous Thomson scattering. Numerical analysis shows that due to the lack of one degree of freedom in isotactic lattice (ISL) compared to syndiotactic lattice (SYL), the bandgap starting-frequency of the ISL is significantly lower than that the one of the SYL by up to 66%. The bandgap properties are further demonstrated by simulation and experimental measurements. This research reveals that the condition of having alternating arrangement orientations between neighboring atoms is not indispensable for this kind of bandgap, and a rational geometry satisfying the Thomson scattering-based bandgap conditions can further reduce the bandgap frequency without affecting the stiffness and lightweight of the structure. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract The growth of stimulated Raman side-scattering of a laser beam propagating in the plasma may be influenced by the presence of co-propagating electron beam. The laser beam excites a pair of plasma wave and side-scattered electromagnetic wave. The side-scattered wave and pump wave couple together and exert a ponderomotive force on beam and plasma electrons which intern enhances the amplitude of plasma wave. The density perturbation in the plasma due to plasma wave couple nonlinearly with pump wave and excite a nonlinear current responsible for the growth of side-scattered electromagnetic wave. The phase matching between plasma wave and electron beam controls the growth of Raman process. Raman process saturates when bounce frequency of beam electrons exceeds the growth rate. [ABSTRACT FROM AUTHOR]

Abstract Circular ("V-mode") polarization is expected to be vanishing in the CMB, since it is not produced in Thomson scattering. However, considering that the conventional CMB anisotropies are generated via an early universe mechanism such as inflation or a bouncing scenario, it is possible that circular polarization could be primordially produced and survive to the surface of last scattering. We study this in detail, and find a large class of inflationary models that produce a nearly scale invariant spectrum of scalar V-mode anisotropies. We study the inflationary production and subsequent evolution via the Boltzmann hierarchy, and show that V-mode polarization present in the CMB is suppressed by a factor of at least 10 10 13 relative to the primordial V , consistent with expectation of negligible V-mode polarization from inflation. We consider alternative possibilities for sourcing V primordially, such as the V-mode polarization induced by circularly polarized primordial gravitational waves, or producing V after inflation, via new interactions at recombination. [ABSTRACT FROM AUTHOR]

Abstract Petawatt class femtosecond lasers and x-ray free electron lasers (XFEL) open up a new page in research fields related to space and vacuum physics. One of fundamental principles can be explored by these new instruments is the equivalence principle, saying that gravitation and acceleration should be treated equivalently. If it is true this must lead to the appearance of the Unruh effect analogous to Hawking's black hole radiation. It says that a detector moving with a constant acceleration w sees a boson's thermal bath with its temperature T w = ℏ w / 2 π k B c. Practical detection of the Unruh effect requires extremely strong acceleration and fast probing sources. Here we demonstrate that x-rays scattering from highly accelerated electrons can be used for such detection. We present two, feasible for the Unruh effect, designs for highly accelerated systems produced in underdense plasma irradiated by high intensity lasers pulses. The first is Thomson scattering of a XFEL pulse from plasma wave excited by an intense laser pulse. Properly chosen observation angles enable us to distinguish the Unruh effect from the normal Doppler shift with a reasonable photon number. The second is a system consisting of electron bunches accelerated by a laser wake-field, as sources and as detectors, which move in a constantly accelerating reference frame (Rindler space) and are probed by x-ray free electron laser pulses. The numbers of photons is shown to be enough to observe reproducible results. [ABSTRACT FROM AUTHOR]

Abstract Laser wakefield acceleration of electrons represents a basis for several types of novel X-ray sources based on Thomson scattering or betatron radiation. The latter provides a high photon flux and a small source size, both being prerequisites for high-quality X-ray imaging. Furthermore, proof-of-principle experiments have demonstrated its application for tomographic imaging. So far this required several hours of acquisition time for a complete tomographic data set. Based on improvements to the laser system, detectors and reconstruction algorithms, we were able to reduce this time for a full tomographic scan to 3 min. In this paper, we discuss these results and give a prospect to future imaging systems. Highlights • Scintillator-based CCDs are superior to direct-detection CCDs for medical radiography. • Advanced reconstruction algorithms are capable of handling small data sets. • Acquisition time for laser-driven tomography can be reduced to few minutes. [ABSTRACT FROM AUTHOR]

Abstract Photon engineering can be exploited to control the nonlinear evolution of the drive pulse in a laser–plasma accelerator (LPA), offering new avenues to tailor electron beam phase space on a femtosecond time scale. One promising option is to drive an LPA with an incoherent stack of two sub-Joule, multi-TW pulses of different colors. Slow self-compression of the bi-color optical driver delays electron dephasing, boosting electron beam energy without accumulation of a massive low-energy tail. The modest energy of the stack affords kHz-scale repetition rate at manageable laser average power. Propagating the stack in a pre-formed plasma channel induces periodic self-focusing in the trailing pulse, causing oscillations in the size of accelerating bucket. The resulting periodic injection generates, over a mm-scale distance, a train of GeV-scale electron bunches with 5D brightness exceeding 1 0 17 A ∕ m 2. This unconventional comb-like beam, with femtosecond synchronization and controllable energy spacing of components, emits, via Thomson scattering, a train of highly collimated gigawatt γ -ray pulses. Each pulse, corresponding to a distinct energy band between 2.5 and 25 MeV, contains over 1 0 6 photons. Highlights • Stacked-pulse-driven laser–plasma electron accelerator (SPD LPA) is introduced. • SPD LPA overcomes limitations of conventional single-color LPA energy scaling. • Joule-scale energy of stack permits kHz repetition rate with kW average laser power. • SPD LPA in plasma channel generates a train of bright, fs-scale GeV electron bunches. • Thomson scattering from e-bunch train produces multi-color train of MeV γ -ray pulses. [ABSTRACT FROM AUTHOR]

Highlights • This paper summarizes the development of components for ITER Edge Thomson scattering measurement system. • The beam combiner allows to minimize neutron streaming through the port plug penetrations used for laser beam injection. • A new type of beam dump to withstand harsh thermo-mechanical loads was designed and verified its concept. • A method to align the collection optics field of view was proposed and verified by ray-tracing simulation. Abstract The in-vessel components for the edge Thomson scattering measurement system in ITER (ETS) will be exposed to high thermal and electromagnetic loads, however, their maintenance will be limited because the ITER radiological environment will not allow operators to align the optics near the vacuum vessel. This paper summarizes the development of components, in particular, the beam combiner so as to minimize neutron streaming through the port plug penetrations used for las er beam injection and the strengthening of the beam dump so it can withstand harsh thermal and mechanical loads. Furthermore, a method to align the collection optics field of view was proposed and verified by ray-tracing simulation. The resolution and accuracy of which were approximately 0.5 mm and 0.1 mm, respectively. These values were much finer than the expected characteristic length of electron temperature and density gradients in the edge plasma of ITER. [ABSTRACT FROM AUTHOR]

Abstract This paper presents measurements of the electron temperature in Wendelstein 7-X (W7-X) stellarator plasmas heated by electron-cyclotron-resonance (ECRH) during the first operational phase (OP1.1). The analysis of the slope of the observed X-ray continuum emission (in a semi-logarithmic plot) measured by the use of the Pulse Height Analysis (PHA) system, provides the information about the electron temperature (T e) of the hydrogen plasma. The determination of this fundamental plasma parameter is based on the exponential dependence of the continuum radiation (Bremsstrahlung) on photon energy assuming Maxwellian distribution. In this paper, some experimental results of the estimated electron temperature are presented and compared to the results obtained from the simulations of X-ray spectrum and other diagnostic like the Thomson Scattering (TS) system. [ABSTRACT FROM AUTHOR]

The Collective Thomson Scattering (CTS) will be the ITER diagnostic responsible for measuring the alpha-particle velocity distribution. Using mirrors, a powerful microwave beam is directed into the plasma via an opening in the plasma-facing wall. The microwaves will scatter off fluctuations in the plasma, and the scattered signal is recorded after transmission through a series of mirrors and waveguides. Several components of the CTS system will be directly exposed to neutron radiation from the plasma which can change the properties of the components and reduce their lifetime. In this paper, a neutronics analysis is presented for the CTS system. A study on the influence of different materials on the nuclear heat loads in the launcher mirror is also presented, along with the design of a simple cooling system. All the studies were conducted using the Monte Carlo program MCNP6. The outputs, in particular the nuclear heat loads, will be used to perform the thermal analysis of the system. [ABSTRACT FROM AUTHOR]

If an electric charge is accelerated by a sufficiently intense electromagnetic field, the effects of the radiation emitted by the charge on the charge dynamics (radiation reaction) cannot be ignored. Here we show that classical radiation-reaction effects alter qualitatively and quantitatively the infrared behavior of the spectrum of the radiation emitted by an electron in the presence of an intense electromagnetic plane wave (nonlinear Thomson scattering). An analytical expression of the infrared limit of nonlinear Thomson scattering is provided, which includes radiation-reaction effects and is valid for an arbitrary plane wave. Apart from their own conceptual importance and as a signature of classical radiation reaction, these results provide the limiting expression of the corresponding and yet unknown exact infrared behavior of strong-field QED in an intense plane wave. [ABSTRACT FROM AUTHOR]

A conceptual design of a cooling system for the launcher and receiver mirrors of ITER Low Field Side (LFS) Collective Thomson Scattering (CTS) diagnostic is presented. It is motivated by the fact that these mirrors are subjected to high thermal loads, e.g., neutron fluxes, that lead to maximum temperatures above the required maximum operational temperature of 450 °C for the material (SS 316L(N)-IG). Thus, it is necessary to develop a cooling system capable of maintaining the maximum temperatures of the mirrors below 450 °C, while complying with the CTS and nuclear fusion requirements. Computer Aided Design (CAD) and Finite Element (FE) models of the mirrors with different cooling channel geometries are developed. Steady state and transient thermal Finite Element Analyses (FEA) considering different mass flow rates are conducted for the assessment of the feasible solutions. The results obtained are conclusive, i.e., the cooling requirements are verified and with one of the proposed configurations it is possible to decrease the maximum temperatures of the SS 316L(N)-IG launcher and receiver mirrors from 2307 °C and 1064 °C to 381 °C and 147 °C, respectively, which, corresponds to a maximum temperature decrease of 83% and 86%, respectively. In future works, fatigue and creep analyses shall be implemented for stress and deformation assessment of the mirrors and respective reflective surfaces. [ABSTRACT FROM AUTHOR]

Inelastic X-ray scattering (IXS) experiments of RT Al 3 ( R = La Ce, T = Cu, Au) were carried out at 300 and 5.5 K. The spectra between LaCuAl 3 and CeCuAl 3 (LaAuAl 3 and CeAuAl 3 ) are nearly identical at both temperatures except for temperature factors such as temperature dependence of Bose factor in IXS spectra and effect on thermal expansion. This means that no evident temperature dependence of IXS spectra was observed in Ce T Al 3 ( T = Cu, Au). Since the major contribution of scattering cross section in IXS measurements is Thomson scattering, the present results failed to confirm the presence of vibron in these compounds. [ABSTRACT FROM AUTHOR]