同轴单开端型Ge(Li)探测器的研制

同轴单开端型Ge(Li)探测器的制作过程是:先将施主杂质锂蒸发到P型锗单晶表面,经扩散形成N~+P结构,然后在反向偏压作用下,锂离子由扩散区(N~+)向中心漂移,逐渐补偿受主杂质镓,形成PIN结构。它实际上相当一个固体电离宝,其I区为灵敏区。由于在Ge中产生一个电子-空穴对所需的平均能量(2.96eV)比在气体电离室中产生一个电子-离子对所需的能量小十倍,比闪烁计数器产生光电子所需能量小几十倍,因此,Ge(Li)探测器就有比这些探测器高得多的能量分辨率。     

配Si(Li)探测器的脉冲光反馈前置放大器和脉冲处理器

本文介绍配Si(Li)探侧器的脉冲光反馈前置放大器和脉冲处理器的工作原理及性能。配有φ4mmSi(Li) 探测器的整个系统的电子噪声为190eV(FWHM)_(st),对~(55)Fe5.9keV的分辨率为240eV(FWHM)。     

用于半导体X射线探测器的电荷灵敏前置放大器

本文叙述了脉冲光反馈和电阻反馈两种方式的优缺点,并分析了电阻反馈中产生噪声的各项因素及减小噪声的方法。文中还引述了一种减小噪声斜率的办法。根据以上分析研制的前置放大器外接电容为零时的噪声为140～150eV,与硅锂探测器相配时,对MnK_α线的能量分辨率为243eV。     

高分辨率硅(锂)X射线探测器

本文介绍了GL1221型硅(锂)X射线探测器管芯的制造工艺及与之相配合的脉冲光反馈低温前置放大器。探测器系统的能量分辨率为165eV(对~(55)Fe 5.89keV Mn-KaX射线),计数率为1020cps,电子学噪声104eV。该指标已达到国外同类产品的商品水平。     

Formulae for secondary electron yield from insulators and semiconductors

The processes and characteristics of secondary electron emission in insulators and semiconductors were studied, and the formulae for the maximum yield(δ_m) at W_(pOm)≤ 800 eV and the secondary electron yield from insulators and semiconductors δ at the primary incident energy of 2 keV≤ W_(pO) 10 keV(δ_(2-10)) and10 keV ≤ W_(pO)≤100 keV(δ_(10-100)) were deduced. The calculation results were compared with their corresponding experimental data. It is concluded that the deduced formulae can be used to calculate δ_(2-100)at W_(pOm)≤ 800 eV.     

Effects of the phase variation and high-order momentum transfer components of NN amplitude on p-~4He elastic scattering

Elastic scattering differential cross sections for a p- ~4He system are calculated within the framework of optical limit approximation of the Glauber multiple scattering model. Three different ranges for proton energy(E_(lab)), 19〈E_(lab)〈50 Me V, 100≤E_(lab)≤1730 Me V, and 45 ≤E_(lab)≤393 Ge V are considered. It is shown that the Pauli blocking fails to describe the data up to the proton energy, E_(lab)〈100 Me V. For higher proton energies, a qualitative agreement is obtained. The observed elastic scattering differential cross section is nicely reproduced in the whole range of scattering angles in the center of mass system up to Θ_(c.m.)〈200° for 19〈E_(lab) ≤100 Me V when the effect of both the nucleon–nucleon(NN) phase variation parameter γNN and higher-order momentum transfer components(λ_n; n = 1 and 2) of(NN) elastic scattering amplitude is included. In the range of 200 E_(lab) 1730 Me V, introducing λ_n plays a significant role in describing the data up to the momentum transfer, q~2≤1:2(Ge V/c)~2.Moreover, it is found that considering only the effect of phase variation parameter, cNN, improved the agreement in the region of minima for elastic scattering differential cross section for 45≤E_(lab)≤393 Ge V. The values of cNNand kn as a function of incident proton energies are presented.     

低噪声脉冲光反馈电荷灵敏前置放大器的进展

本文介绍用于低能X射线Si(Li)谱仪低噪声脉冲光反馈电荷灵敏前置放大器的进展,其零电容电子学噪声FWHM=85-110eV(对Si),并给出实验结果。     

精密低噪声前置放大电路的设计

介绍了一种中、低频低噪声前置放大电路的设计方案。理论分析影响低噪声前置放大电路的因素;采用抑制噪声和直流漂移电路减小噪声干扰;并对设计电路进行测试和分析。测试表明其等效输入噪声失真率≤0.04%(输出9.5 rms时);在1~100 kHz范围内,频率稳定度≤0.01%。     

低噪声电荷灵敏前置放大器

本文介绍一种低噪声电荷灵敏前置放大器,零外接电容噪声1.49keV,电容噪声斜率为15eV/pF,外接电容1000pF时上升时间12ns,输出动态范围±10V。     

脉冲光反馈电荷灵敏前置放大器

从六十年代中期Elad等人制造出第一台半导体X射线谱仪以来,低噪声前置放大器的研制发展很快,先后出现电阻反馈、直流光反馈、脉冲光反馈及漏反馈等技术。目前,多采用后两种,其零电容电子学噪声可达70—80eV(FWHM,Si),用于Si(Li)X射线谱仪系统时,对5.9keV射线的能量分辨率在150eV左右。     

YAG晶体在软X射线荧光靶探测器中的应用

荧光靶探测器是同步辐射光源光束位置定位的重要设备之一,本文在96 500 eV软X射线内对CVD金刚石薄片和Ce:YAG晶体薄片进行光致发光亮度的测试,观察到Ce:YAG在该能量段的发光亮度比金刚石高,完成了上海光源软X射线荧光靶探测器靶材的实验研究与探测器的设计;同时给出了YAG晶体荧光靶探测器在线使用时观察到的相干光的衍射图像。     

一种基于SiPM的具有高能量分辨率的紧凑型溴化镧γ谱仪

基于光电倍增管(photomultiplier tube,简称PMT)的LaBr₃:Ce γ谱仪具有比NaI(Tl)γ谱仪更高的能量分辨率,但具有体积大、对磁场敏感、需要高电压等缺点。硅光电倍增管(Silicon photomultiplier tube,简称SiPM)具有与PMT相近的增益和效率,同时具有诸如高定时分辨率、抗磁场能力强、低偏压和紧凑尺寸等优良特性。本文将LaBr₃:Ce晶体与SiPM阵列耦合,设计研制基于SiPM的紧凑型LaBr₃:Ce γ谱仪,通过降噪、优化工作电压等措施改善SiPM的缺点对γ谱仪性能的影响。工作电压的噪声会导致能量分辨率发生恶化,通过设计无源滤波电路CLC π型滤波器,利用其对直/交流阻抗的不同特性,滤除高频纹波,工作电压的信噪比从未降噪前的62.6 dB提高到74.64 dB;能量分辨率最优值对应于表示暗噪声、串扰、光电探测效率和SiPM增益之间折衷的最佳工作电压。通过实验给出不同工作电压下的能量分辨率,确定最佳工作电压为54.8 V,该电压下的能量分辨率为3.06%(@662 keV),结果与使用光电倍增管(PMT)测量的2.89％非常接近。     

Readout electronics of a prototype spectrometer for measuring low-energy ions in solar wind plasma

Readout electronics is developed for a prototype spectrometer for in situ measurement of low-energy ions of30 e V/e–20 ke V/e in the solar wind plasma.A low-noise preamplifier/discriminator(A111F) is employed for each channel to process the signal from micro-channel plate(MCP) detectors.A high-voltage(HV) supply solution based on a HV module and a HV optocoupler is adopted to generate a fast sweeping HV and a fixed HV.Due to limitation of telemetry bandwidth in space communication,an algorithm is implemented in an FPGA(field programmable gate array) to compress the raw data.Test results show that the electronics achieves a 1 MHz event rate and a large input dynamic range of 95 p C.A slew rate of 0.8 V/ls and an integral nonlinearity of 0.7-LSB for the sweeping HV,and a precision of less than 0.8 % for the fixed HV are obtained.A vacuum beam test shows an energy resolution of 12 ± 0.7 % full width at half maximum(FWHM) is achieved,and noise counts are less than10/sec,indicating that the performance meets the physical requirement.     

Electron population properties with different energies in a helicon plasma source

The characteristics of electrons play a dominant role in determining the ionization and acceleration processes of plasmas. Compared with electrostatic diagnostics, the optical method is independent of the radio frequency(RF) noise, magnetic field, and electric field. In this paper, an optical emission spectroscope was used to determine the plasma emission spectra, electron excitation energy population distributions(EEEPDs), growth rates of low-energy and highenergy electrons, and their intensity jumps with input powers. The 56 emission lines with the highest signal-to-noise ratio and their corresponding electron excitation energy were used for the translation of the spectrum into EEEPD. One discrete EEEPD has two clear different regions,namely the low-energy electron excitation region(neutral lines with threshold energy of13–15 eV) and the high-energy electron excitation region(ionic lines with threshold energy?19 e V). The EEEPD variations with different diameters of discharge tubes(20 mm, 40 mm,and 60 mm) and different input RF powers(200–1800 W) were investigated. By normalized intensity comparison of the ionic and neutral lines, the growth rate of the ionic population was higher than the neutral one, especially when the tube diameter was less than 40 mm and the input power was higher than 1000 W. Moreover, we found that the intensities of low-energy electrons and high-energy electrons jump at different input powers from inductively coupled(H) mode to helicon(W) mode; therefore, the determination of W mode needs to be carefully considered.     

Pixel X-ray detectors in epitaxial gallium arsenide withhigh-energy resolution capabilities (Fano factor experimentaldetermination)

Gallium Arsenide pixel detectors with an area of 170×320 μm² and thickness of 5 μm, realized by molecular beam epitaxy, have been designed and tested with X- and γ rays. No significant charge trapping effects have been observed, and a charge collection efficiency of 100% has been measured. At room temperature an energy resolution of 671 eV full width at half maximum (FWHM) at 59.54 keV has been obtained, with an electronic noise of 532 eV FWHM. With the detector cooled to 243 K, the electronic noise is reduced to 373 eV FWHM, and the K_α and K_β lines of the ⁵⁵Fe spectrum can be resolved. The Fano factor for GaAs has been measured at room temperature with 59.5 keV photons yielding F=0.12±0.01     

Timing properties of LuAP:Ce studied with large-area avalanchephotodiodes

Prompted by recent interest in positron emission tomography scanners equipped with LuAP:Ce (LuAlO₃:Ce) scintillators read by avalanche photodiodes, we have measured timing properties of this scintillating material with large-area avalanche photodiodes (LAAPDs) from Advanced Photonix, Inc. (API). We have obtained a time resolution of 1.16±0.06 ns for 511 keV peak from a ²²Na source with energy threshold set at 400 keV and 680±35 ps for ⁶⁰ Co source with energy threshold set at I MeV. The dependence of time resolution on LAAPD gain was measured showing improved timing at gains over 200, but at the cost of higher excess noise. Comparing the time resolution of LuAP:Ce and LSO:Ce measured with LAAPD and photomultipliers, we discuss the dependence of timing properties on the tight output and decay time of these scintillators     

Si related defects in the VUV in silicon multi-energy implanted Type III silica

Some effects on the vacuum ultraviolet optical bands (6-8 eV) produced by implanted Si, using multi-energies ranging from 320 to 35 keV energies to produce a layer of constant concentration in (Type III) silica, approximately 600 nm thick, have been measured. Based on two methods of analyzing the spectra as a function of implanted layer concentration; first, by subtracting the spectrum of an un-implanted sample from each spectrum of the implanted samples and second, subtracting the spectrum of one concentration from the spectrum of the next largest concentration, we have identified band maxima. In the case of the first subtraction the maxima are at ∼7.54, 7.7, and 7.92 eV. In the case of the second subtraction the maxima are at ∼7.5, 7.85, and 7.95 eV. These difference spectra show that the various states have differing rates of increase with increase in Si concentration. The absorption between 6 and 7 eV increases with increasing Si concentration indicating that there is/are a band or bands in this region of the spectra. Because all of the bands that are resolved increase with increasing Si concentration we attribute these bands to Si related electronic states. An estimate of the oscillator strengths of these bands is made by comparison of their peak absorption with that of the E′ optical band at 5.83 eV, f = 0.14 ± 0.05, in the same samples. This comparison shows that all of the resolved bands between 6 and 8 eV have oscillator strengths equal to or larger than the E′ state, consistent with our assignment of the bands to Si related states. By comparing to the spectra from the Si implanted samples, the bands produced by radiation damage in an Ar implanted sample are between 7.3 and 8 eV bands are attributed to Si related states.     

Film growth by polyatomic C2H5 bombarding a diamond (1 0 0) surfaces: Molecular dynamics study

The deposition of polyatomic C₂H₅⁺ ions is studied using classical molecular dynamics simulations with a new improved Brenner potentials developed by Brenner. The simulation results show that when the incident energy is less than 65 eV, the deposition coefficient of H is larger than that of C atoms. When the incident energy is larger than 65 eV, the deposition of H is less than that of C atoms. With increasing incident energy, a transition from Csp3-rich to Csp2-rich in the grown films is found.     

Modele elementaire sur les dommages radio-induits dans le graphite en pile: correlation entre temperature et flux

A model based on displacement spikes is examined (and confirmed) for the primary defects induced by neutron bombardment. It is shown that, before any random annealing takes place, these spikes consist of about 4 stably displaced atoms, either isolated or grouped as interstitials or vacancies. There are no vacancy-type defects with activation energies less than 4 eV. The effects of irradiation temperature on dimensional changes in graphite (as published in the literature) are readily described in terms of this model. In particular, this model permits one to account for the effect of dose rate on the defect concentration. At low temperatures ($\text{T}\text{\$}\text{?}\text{300°C}$), the theoretical treatment is equivalent to the currently accepted empirical treatment, and its extrapolates well to higher temperatures. A series of experiments is presented which helps to refine the model for high temperature and sets a lower limit of 4 eV for the vacancy activation energy in the displacement spike. Q = 4 eV is proposed for the purposes of temperature correction in the range 600–1400°C. More generally, as a first approximation, the model shows that a temperature rise of 7% (in degrees Kelvin) compensates for a 10-fold increase of flux, at constant fluence.