HT-6B上的硬X射线测量

HT-6B托卡马克一直对各种放电状态下硬X射线的辐射强度进行着常规监测。在HT-6B低q运行期间,测量并比较了放电不同阶段的硬X射线能谱,对硬X射线的锯齿振荡同软X射线的锯齿振荡做了对照分析。在最近HT-6B低杂波电流驱动实验中。同时观测了从等离子体内部发射的硬X射线和限制器上的厚靶轫致辐射。初步的分析表明它们产生于不同的发射机制。     

HT-6B上的硬X射线测量(英文)

HT-6B托卡马克一直对各种放电状态下硬X射线的辐射强度进行着常规监测。在HT-6B低q运行期间,测量并比较了放电不同阶段的硬X射线能谱,对硬X射线的锯齿振荡同软X射线的锯齿振荡做了对照分析。在最近HT-6B低杂波电流驱动实验中,同时观测了从等离子体内部发射的硬X射线和限制器上的厚靶轫致辐射。初步的分析表明它们产生于不同的发射机制。     

碘化汞探测器及其对HL-1M装置中X射线辐射测量

本文叙述新研制的以高纯度碘化汞晶体为基片的低噪声、高探测效率、高计数率、较高能量分辨率，常温状态下运行的ＨｇＩ２半导体探测器的特点，以及特制的电荷灵敏前放和主放大器组成的探测系统对ＨＬ－１Ｍ托卡马克在欧姆加热、低杂波电流驱动、外加径向电场以及激光吹气掺杂等实验条件下，来自等离子体心部的硬Ｘ射线辐射进行测量，得到辐射强度和能谱随时间的变化等实验结果，并对实验结果作了初步的解释。     

MM-2装置中ECR等离子体空间分辨的观测(英文)

介绍了用硬X射线的针孔成像法测量简单磁镜装置MM-2中ECR等离子体特性的方法及结果。这种非破坏性的成像法,直观显示了热电子等离子体的空间分布,一次放电即可成一帧清晰的像。大量实验照片给出了发射强度随放电参数的变化关系。     

MM-2装置中ECR等离子体空间分辨的观测

介绍了用硬X射线的针孔成像法测量简单磁镜装置MM-2中ECR等离子体特性的方法及结果。这种非破坏性的成像法,直观显示了热电子等离子体的空间分布,一次放电即可成一帧清晰的像。大量实验照片给出了发射强度随放电参数的变化关系。     

HL-1M装置LHCD和ECRH实验的边缘流速和电场测量

在聚变装置中等离子体边界条件对整个等离子体约束性能的影响是非常敏感的。L-H模转换机制与边界径向电场E_r,E_r的梯度及极向旋转速度等参数密切相关;同时,边缘等离子体的径向输运与边缘极向电场E_θ的变化有关。在HL-1M装置中利用低杂波(LHW)注入和电子回旋加热(ECRH)实验,观测边缘等离子体流速和电场的径向分布和变化来研究改善约束性能与E_θ,E_r,dE_r/dr及边界涨落的关系。     

托卡马克LHCD系统的等离子体电流熄灭保护技术

根据实际HT－7托卡马克的实验需要,提出并实现了等离子体电流熄灭保护装置,杜绝了等离子体电流熄灭或在低等离子体电流下,强功率、长脉冲的低杂波对托卡马克装置及低杂波系统的威胁。     

HL-1M装置边缘等离子体特性研究

边缘和芯部等离子体的同时控制对优化托卡马克等离子体性能是重要的。边缘等离子体密度、温度和空间电位等通常采用朗缪尔静电探针测量,而旋转速度可用马赫探针测量。好的加料技术对于获得高性能等离子体也很重要,在HL-1M装置上已开展了8发弹丸注入和分子束注入(MBI)加料实验,它能使等离子体产生中空的温度和电流密度分布,并容易获得高密度和良好的约束。本文主要介绍在低杂波电流驱动(LHCD)、多发弹丸注入和MBI三种典型放电中边缘等离子体参数的测量结果。     

超导托克马克TRIAM—1M的最新进展

在超导托卡马克ＴＲＩＡＭ－１Ｍ上,广泛开展了稳态托卡马克反应堆的研究。用２．４５ＧＨｚ低杂波电流驱动已演示了密度为ｎｃ＝２＊１０＾１８ｍ＾－３,持续时间超过２ｈ的放电。在孔栏５ＭＷ．ｍ＾－２的高平均壁负载条件下,用８．２ＧＨｚ的杂波电流驱动使ｎｃ＝２＊１０＾１９ｍ＾－３高密度等离子体维持了１ｍｉｎ。     

CdTe探测器对EAST托卡马克中20–200keV硬X射线测量

介绍了EAST托卡马克装置硬X射线诊断系统。该系统由探测器阵列和电子线路组成,探测器采用水平七道的碲化镉(CdTe)探测器阵列。在EAST托卡马克装置上建立了一套较完善的硬X射线能谱诊断系统,用来测量等离子体在硬X射线辐射能段(20–200 keV)的能谱。实验结果表明,该系统能满足测量相应能量范围的等离子体硬X射线轫致辐射要求。文中给出了碲化镉探测器的标定结果及典型的放电结果。     

高气压充氙多丝正比室

研制了一个高气压充氙多丝正比室。其灵敏面积近700cm~2,充以3个大气压的氙-甲烷混合气体(95％Xe+5％CH_4),可探测10—200keV的硬X射线。对~(241)Am的59.54keV X射线,单丝能量分辨率(FWHH)10％,全部阳极丝并联输出则为19％,对其29.8keV的逃逸峰则分别为17％和20％。在密封不流气状态下可工作数月而保持良好的能量分辨率。     

X-Ray Measurement and Enhancement of SBUPF1 Plasma Focus Device in Different Ar Pressures and Operating Voltages

In this paper, best condition of filling gas pressure and operating voltage for SBUPF1 plasma focus device to have maximum intensity of hard and soft X-ray emission has been reported. For time resolved X-ray detection, PIN detector and fast plastic Scintillator detector with appropriate filters have been used and for time integrated X-ray emission measurement, radiography films with appropriate filter masks have been used. Rogowski coil has been used for pinch detection. The highest hard X-ray emission has been observed at the pressure of 0.45 mbar of Argon and discharge voltage about 23.5 kV. The highest Soft X-ray emission has been observed at the pressure of 0.35 mbar of Argon and discharge voltage about 23.5 kV. For enhancement of hard X-ray emission intensity, lead disk was placed in copper anode tip and measurements were repeated. Results have shown that hard X-ray emission has been enhanced about 23% and soft X-ray emission has been enhanced about 33% with inserting a high atomic number metal disk like lead. Results from integral X-ray measurement have shown presence of dominant peaks in ranges 13.2–15, 21–21.9 and 23.4–24.3 keV with significant spectral components in the range of 0–50 keV. Pinch size has measured with pin hole camera and it is about 0.6 mm × 2.12 mm. Captured images with SBUPF1 have confirmed that it is a suitable source for introspective imaging with capability of showing very fine details.     

Effect of the laser focus position on characteristics of X-ray and ion emission from gold plasmas generated by a sub-nanosecond laser

X-ray and ion emission from gold plasma produced by a sub-nanosecond Nd:glass laser has been studies as a function of distance of the target from the best focus position. Thermal ion (kinetic energy <19 keV) signals and soft X-ray flux (photon energy >0.7 keV) measurements decrease as the target is moved closer to the best focus position in spite of an increase in laser intensity. We observe simultaneously a strong correlation between the onset of this drop in the flux of soft X-ray and the growth of harder X-ray (photon energy 3–5 keV), alongside a growth in fast ion (energy >67 keV) numbers. This is indicative of the onset of non-linear processes at the higher irradiances (～10¹⁴ W/cm²) associated with the best focus position. Our results show that when using laser plasmas as X-ray or ion sources, X-ray and ion emission in a desired spectral range can be optimized by adjusting the focusing on the target.     

On the Production of Relativistic Runaway Electrons in Damavand Tokamak

Experimental observations in Damavand tokamak show that hard X-ray is produced by either disruption with I _p  < 20 kA or by shots with I _p  > 20 kA. Hard X-ray also persists from the initiation of plasma discharge to the end. Occurrence of multiple spikes in hard X-ray during the discharge is evident. The propagation of hard X-ray is attributed to runaway electrons. We observe runaway electrons in two regimes with different characteristics. Regime (RADI) is similar to the observations of other Tokamak during disruption on that the plasma current is reduced abruptly and interpreted by Dreicer theory. In the regime of RADII, hard X-ray and subsequently runaway electrons are observed from starting of plasma discharge which provides the condition that the most of runaway electrons contain the toroidal plasma current. Runaway electron beam excites whistler waves and scattered electrons in velocity space and prevent growing the runaway electrons beam.     

A novel compact Tokamak Hard X-ray diagnostic detector

A compact X-ray detector based on the lutetium yttrium oxyorthosilicate scintillator(LYSO) and silicon photomultiplier(Si PM) has been designed and fabricated for the hard X-ray diagnosis on the HL_2A and HL_2M Tokamak devices. The LYSO scintillator and Si PM in small dimensions were combined in a heat shrink tube package, making the detector compact and integrative. The Monte Carlo particle transport simulation tool,Geant4, was utilized for the design of the detector for the hard X-ray from 10 keV to 200 keV and the best structure scheme was presented. Finally, the detector was used to measure the photon spectrum of a ~(137)Cs gamma source with a pre-amplifier and a multichannel amplitude analyzer. The measured spectrum is consistent with the theoretic spectrum, it has shown that the energy resolution of the detector is less than 14.8% at an energy of 662 keV.     

超短脉冲激光与固体靶相互作用的硬X射线能谱

本实验使用高纯锗探测器，运用单光子法，对超短脉冲激光与固体铜靶相互作用产生的硬X射线能谱进行测量。实验结果表明：在激光强度I≈8×10¹⁶W/cm²的P极化光以45°入射角照射5 mm铜靶、探测立体角为4.5×10^－6的实验条件下，产生的硬X射线的能量主要集中在低于100keV能量范围内，超热电子温度分别为(7.4±0.7)keV和(19.5±1.6)keV。     

Characterization of dose delivery in a hard X-ray irradiation facility

The Radiation Bioengineering Laboratory at Seoul National University (SNU) operates a user-constructed hard X-ray irradiation facility for radiation biology and radiation therapy physics studies. The system package of YXLON model 450-D08 operating at the anode voltage of up to 450 kV is a key part of the facility, which enables in vitro cell irradiation and animal irradiation for in vivo studies. In this article, dose delivery in the hard X-ray irradiation facility was characterized in terms of the dose vs. operational parametric combination of the facility. The operational parameters included beam tube anode voltage, beam tube current, irradiation time, and beam exit-to-sample distance. Bremsstrahlung X-rays at energy below approximately 20 keV were filtered out by a 3 mm-thick aluminum plate fitted over the 5 mm-thick beryllium window. Gafchromic EBT films were used as radiation sensor materials in dose measurement. The characterization was validated via experimental observation of the in vitro biological responses of cells to radiation exposure. The biological responses obtained using the new hard X-ray irradiator were highly comparable with those obtained using a commercial gamma-ray irradiator.     

Radiation damage (blistering) in Al,Cu, Si by exposure to a plasma focus discharge

Plates of Al, Cu (polycrystalline) and Si (monocrystal) have been irradiated with beams of D⁺ ions (keV to MeV) and other radiation by exposure to a single discharge of a 5–10-kJ Plasma Focus in deuterium. Scanning electron microscope and elemental X-ray energy dispersive analysis are used for diagnostics. The nonuniformity of the ion beam causes a nonuniform damage with formation of clusters of blisters. A statistical analysis of blister parameters (diameter and skin thickness) is used to investigate the internal structure of a deuteron beam ejected from the plasma. The value K ～ 10–20 keV is obtained as the typical ion energy for the bulk of the deuterons and an ion energy E ～ 200–230 keV is typical for individual ion groups (ion strings) forming the high-energy deuteron beam.     

High resolution X-ray photon-counting detector with scintillator-deposited charge-coupled device

We report on a new photon-counting detector possessing unprecedented spatial resolution and moderate spectral resolution for 0.1-100 keV X-rays. It consists of an X-ray charge-coupled device (CCD) and a scintillator. The scintillator is directly coupled to the back surface of the X-ray CCD. Low-energy X-rays below 10 keV can be directly detected by the CCD. The majority of hard X-rays above 10 keV pass through the CCD but can be absorbed by the scintillator, generating visible photons. We coupled needlelike CsI(Tl) on the front surface of the back-illuminated (BI) CCD. The high detection efficiency of BI CCDs in the visible band enables us to collect visible photons emitted from the CsI(Tl) efficiently, leading to the moderate spectral resolution of 28.4% at 22.1 keV and 25% at 59.5 keV. We also investigated the imaging capability of our device and demonstrated high resolution imaging with an accuracy of 10 /spl plusmn/3 /spl mu/m at 17.4 keV.     

Plasma Stability Evaluation Based on MHD Activity and Hard X-Ray Emission in the IR-T1 Tokamak

Determinations of the poloidal beta, internal inductance, plasma energy, plasma pressure, plasma temperature, plasma resistance, plasma effective atomic number, magneto-hydrodynamics (MHD) activity, Runaway electrons energy and energy confinement time are essential for tokamak experiments and optimized operation. Also some of the plasma information can be deduced from these parameters, such as plasma toroidal current profile, and MHD instabilities. In this contribution we investigated about measurements of some plasma parameters as well as MHD activity and Runaway electrons energy. For this purpose we used the magnetic diagnostics and a hard X-ray spectroscopy in IR-T1 tokamak. A hard X-ray emission is produced by collision of the Runaway electrons with the plasma particles or limiters. The mean energy was calculated from the slope of the energy spectrum of hard X-ray photons. In this paper in order to measure energy of the Runaway electrons, we obtained hard X-ray energy in every 5 ms intervals, from the beginning to the end of plasma. Results indicated mean energy of Runaway electrons is maximum during the 0–5 ms interval.