- 标题
- 摘要
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- 实验方案
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Using a commercial mini-X-ray source for calibrating Bragg crystals
摘要： In this paper we describe a procedure for calibration of Bragg crystals used for X-ray spectroscopy of laser plasmas. The method uses a relatively inexpensive commercially available X-ray source. By using the source to pump a metallic foil such as vanadium or titanium we were able to create a K-α emission source with minimal background radiation outside the desired photon energy. By using photon counting techniques with a CCD detector we were able to get absolute calibrations of curved and flat Bragg crystals in the 4–5 keV region. An important advantage of our method is that absolute calibration was not necessary either for the commercial source or the detector.
关键词： X-ray detectors and telescopes,spectroscopy and imaging,Plasma diagnostics - interferometry
更新于2025-09-23 15:23:52
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The distribution of OH in surface micro-discharge with different electrode widths by laser-induced fluorescence
摘要： Cold atmospheric plasma has been successfully applied in the field of biomedicine. One of the most pressing challenge is the development of plasma devices, for example, large-area application in wound healing. Surface micro-discharge device is one new type of dielectric barrier discharge design with desirable plasma features, such as homogeneity over a large surface area. In this study, two devices with electrode width varying from 0.25 to 1.00 mm were fabricated. The contribution focuses on the impact of the hexagonal mesh electrode width on the degree of uniformity of hydroxyl (OH) radicals in the downstream region and the OH transport efficiency. Accordingly, OH radicals were measured as an indicator by laser-induced fluorescence. Steady state measurements of OH perpendicular to the dielectric surface demonstrated that narrow electrode width could not offer a high degree of uniformity, and will reduce the transport efficiency of reactive species.
关键词： Plasma diagnostics - interferometry, spectroscopy and imaging,Plasma diagnostics - high speed photography
更新于2025-09-19 17:13:59
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Design of Neutron Imaging Aperture for Inertial Confinement Fusion in Laser Fusion Research Center
摘要： Neutron Imaging System (NIS) has been used to image the burn volume and cold fuel volume of imploding fusion capsules. In this work, we present a design of neutron imaging aperture for inertial con?nement fusion in Laser Fusion Research Center. Since the total neutron yield should be less than 1014, the penumbral aperture has been chosen. A geometric model has been developed to assess the performance of the neutron imaging system, including the spatial resolution, the ?eld of view and the signal-to-noise ratio. This model reproduces the performances of neutron image systems on OMEGA. The spatial resolution of designed NIS is about 22 μm for a ?eld of view of 250 μm. The signal-to-noise ratio can be better than 10, if the neutron yield is higher than 1013.
关键词： Nuclear instruments and methods for hot plasma diagnostics,Plasma diagnostics - interferometry, spectroscopy and imaging
更新于2025-09-16 10:30:52
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Laser absorption spectroscopy studies to characterize Cs oven performances for the negative ion source SPIDER
摘要： The SPIDER H?/D? ion source is currently in operation in the Neutral Beam Test facility (NBTF) at Consorzio RFX (Padova, Italy) to prove the possibility of generating up to 40 A of negative ions, with a maximum extracted current density of 350 A/m2 (H)/285 A/m2 (D) and a fraction of co-extracted electrons not greater than 0.5 (H)/1 (D). These performances are required for the realization of the ITER Neutral Beam Injector (NBI), which should deliver 16.7 MW to the plasma by means of negative ions accelerated up to 1 MeV and neutralized before being injected into the ITER tokamak. In order to obtain such high extracted current densities and low co-extracted electron fractions it is necessary to lower the work function of the surface of the acceleration system grid facing the source; this will be accomplished by coating the surfaces with Cs, routinely evaporated by three ovens. The functionality of the ovens has been tested at the CAesium oven Test Stand (CATS), hosted at NBTF. The test stand is equipped with several diagnostics, among which a Laser Absorption Spectroscopy (LAS) diagnostic. Using a tunable laser diode, the LAS diagnostic gets the high resolution absorption spectrum of the Cs 852 nm D2 line along a line of sight to measure Cs density at ground state. The paper describes the test stand and the LAS diagnostic, together with the characterization of the ovens to be installed in SPIDER. The paper will also study the systematic density underestimation e?ect caused by Cs ground state depopulation, as a function of laser intensity and of Cs density, in the perspective of correcting the density evaluation.
关键词： Plasma diagnostics - interferometry, spectroscopy and imaging,Ion sources (positive ions, negative ions, electron cyclotron resonance (ECR), electron beam (EBIS))
更新于2025-09-16 10:30:52
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The spatial-temporal distribution of the electron density and temperature in nanosecond pulsed discharge plasma measured by laser Thomson scattering
摘要： The spatial-temporal distribution of the electron temperature (Te) and density (ne) in a nanosecond pulsed discharge (NPD) argon plasma with a ball-to-plate electrode con?guration at 2 × 103 Pa has been measured by Laser Thomson Scattering (LTS). The peak voltage between two electrodes is 1520 V and the current is 3 A when the ball-like electrode is connected to the negative high voltage. The results indicate that it is possible to enhance the electron density of the plasma discharge using the rising edge of pulse voltage. The measured plasma parameters: Te decreases exponentially from 1.75 eV to 0.1 eV and ne increases rapidly to 3.94 × 1020 m?3 from 15 ns to 115 ns then decreases to 1.17 × 1019 m?3. In the discharge with cylindrical geometric symmetry, Te increases from ball to plate, while ne is opposite. In the r-direction, both Te and ne decrease from central to edge at 3.4 mm. Value of ne varies by 20 times from maximum to minimum and Te is only about 1.5 times.
关键词： Plasma diagnostics - interferometry, spectroscopy and imaging,Pulsed power
更新于2025-09-16 10:30:52
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New infrared imaging diagnostic for the Neutral Beam Heating System at the TJ-II stellarator
摘要： An upgraded infrared imaging system has been installed at the stellarator TJ-II as a diagnostic tool of the Neutral Beam Injection heating. Thermographic analysis of the beam-wall interaction areas can be used to estimate the beam power lost through reionization and shine-through mechanisms in Neutral Beam heated plasmas. Three di?erent Regions of Interest inside TJ-II vacuum vessel have been determined whose thermographic analysis will be applied to the study of beam related processes. The optical conditions required for each application have been used to de?ne the speci?cations of the IR camera. Optimization of the optical design has been carried out by means of the optical simulation code ZEMAX. The IR window size has been increased to maximize the fraction of the ?eld of view that is free from vignetting. The system has been fully commissioned and is now operative, routinely providing thermographic data of the regions of interest during the last TJ-II experimental campaign. The IR diagnostic is described in detail and its applicability to study beam power deposition on di?erent targets is discussed.
关键词： Plasma diagnostics - high speed photography,Nuclear instruments and methods for hot plasma diagnostics,Beam Optics,Plasma diagnostics - interferometry, spectroscopy and imaging
更新于2025-09-12 10:27:22
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Comprehensive diagnostics of hot electron emission from plasmas produced by sub-nanosecond terawatt laser on thin foil metal targets
摘要： Interaction of high-power and high-energy lasers with matter generates plasmas emitting considerable amounts of relativistic electrons. In this contribution such plasmas were produced by PALS kJ laser facility delivering the beam with intensity of the order of 3 · 1016 W · cm?2 in 400 ps on thin foil metal targets. To study the emission of hot electrons in horizontal plane around the target, an array of electron spectrometers was employed to record the electron emission from the plasma in several angles around the target. For experimental determination of the total number of hot electrons escaping from the plasma through the plasma barrier a target probe was used in order to measure the target return current which neutralizes the positive target charge produced by these escaping hot electrons. Together with this diagnostics the femtosecond interferometry was used to obtain spatial electron density pro?les in close proximity to the irradiated target at selected time delays. Interferograms indicated occurrence of plasma density modulations in front of the target and made it possible to calculate the number of electrons contained within thermal fraction of the plasma produced by the laser. The number of these electrons correlates with the ?ux of soft x-ray radiation observed with the use of an x-ray streak camera.
关键词： Plasma diagnostics - probes,Pulsed power,Interaction of radiation with matter,Plasma diagnostics - interferometry, spectroscopy and imaging
更新于2025-09-12 10:27:22
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X-ray imaging of bio/medical samples using laser-plasma-based X-ray sources and LiF detector
摘要： This contribution to ECPD2019 is dedicated to the memory of Anatoly Faenov. During a period of approximately thirteen years 1994–2006, Anatoly and his wife Tatiana Pikuz (simply “Tania” for friends), accepting the frequent invitations of the National Institute for Nuclear Physics (INFN) and of the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), cooperated with many Italian research laboratories dedicated to EUV and soft X-ray generation, spread in di?erent towns (L’Aquila, Frascati, Milano, Padova, Pisa, Roma, etc.). In spite of the fact that they could stay in Italy only about one or two months per year, their activity was so intense that more than 50 peer- reviewed publications were generated from their experimental and theoretical work (just considering only the results obtained at L’Aquila and Tor Vergata — Rome Universities and at the ENEA Research Center of Frascati), without mentioning the cultural atmosphere that they stimulated in the ?eld of Science and Humanity. The numerous experimental spectra obtained at ENEA by means of their spherically bent mica spectrometers, together with the corresponding theoretical simulations performed in Moscow, allowed to study the changing role of di?erent excitations mechanisms for various plasma conditions, and to characterize at best the ENEA laser-plasma source for di?erent applications: polychromatic and monochromatic micro-radiography of dried biological samples at 1 keV, soft X-ray contact microscopy (SXCM) of living cells in the water-window spectral region, spectroscopy of hollow atoms, etc. In this memorial paper, the main results of biological samples imaging on lithium ?uoride (LiF) detectors, obtained with the ENEA and Tor Vergata University laser-plasma sources, are presented. In particular, the improvement of the micro-radiography and of the SXCM techniques obtained after moving from photoresist detectors and photographic ?lms to lithium ?uoride (LiF) detectors are discussed, for both dried and wet biological samples.
关键词： X-ray detectors,Plasma generation (laser-produced, RF, x ray-produced),Plasma diagnostics - interferometry, spectroscopy and imaging
更新于2025-09-12 10:27:22
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Tomographic capabilities of the new GEM based SXR diagnostic of WEST
摘要： The tokamak WEST (Tungsten Environment in Steady-State Tokamak) will start operating by the end of 2016 as a test bed for the ITER divertor components in long pulse operation. In this context, radiative cooling of heavy impurities like tungsten (W) in the Soft X-ray (SXR) range [0.1 keV; 20 keV] is a critical issue for the plasma core performances. Thus reliable tools are required to monitor the local impurity density and avoid W accumulation. The WEST SXR diagnostic will be equipped with two new GEM (Gas Electron Multiplier) based poloidal cameras allowing to perform 2D tomographic reconstructions in tunable energy bands. In this paper tomographic capabilities of the Minimum Fisher Information (MFI) algorithm developed for Tore Supra and upgraded for WEST are investigated, in particular through a set of emissivity phantoms and the standard WEST scenario including reconstruction errors, in?uence of noise as well as computational time.
关键词： Plasma diagnostics - interferometry, spectroscopy and imaging,X-ray detectors,Micropattern gaseous detectors (MSGC, GEM, THGEM, RETHGEM, MHSP, MICROPIC, MICROMEGAS, InGrid, etc),Radiation calculations
更新于2025-09-09 09:28:46
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Multi-diagnostic setup to investigate the two-close-frequency phenomena
摘要： While the mechanism is still not fully clear, the beneficial effect (higher intensity of highly charged ions, stable plasma conditions) of the second microwave injected to the ECR plasma was observed in many laboratories, both with close and far frequencies. Due to the complexity of the phenomena (e.g. interaction of resonant zones, damped instabilities) complex diagnostic methods are demanded to understand its mechanism better and to fully exploit the potential hidden in it. It is a challenging task since complex diagnostics methods require the arsenal of diagnostic tools to be installed to a relatively small size plasma chamber. Effect of the injected second 13.6–14.6 GHz microwave to the 14.25 GHz basic plasma has been investigated by means of soft and (time-resolved) hard X-ray spectroscopy, by X-ray imaging and space-resolved spectroscopy and by probing the rf signals emitted by the plasma. Concerning the characterization of the X radiation, in order to separate the source and position of different X-ray photons special metallic materials for the main parts of the plasma chamber were chosen. A detailed description and explanation of the full experimental setup and the applied non-invasive diagnostics tools and its roles are presented in this paper.
关键词： Ion sources (positive ions, negative ions, electron cyclotron resonance (ECR), electron beam (EBIS)),X-ray detectors,Plasma diagnostics - interferometry, spectroscopy and imaging,Plasma generation (laser-produced, RF, x ray-produced)
更新于2025-09-09 09:28:46