Optical absorption of Tl+ ions in KBr1-xIx:TlI mixed crystals

spectra of gamma irradiated mixed crystals showed F band, which shifts towards low energy side with the composition of iodine ions in the mixed crystals.     

BESⅢ量能器总装中CsI(Tl)晶体探测单元的光脉冲检测

主要介绍BESⅢ量能器总体安装过程中的光脉冲质量检测,对6240个CsI(Tl)晶体探测单元进行了三次光脉冲检测,介绍了量能器上光纤系统在检测晶体探测单元质量上的重要作用,并根据光脉冲测量的不同结果得出了晶体探测单元的不同问题及其解决方法.     

Selectivity controlling in the hydrogenation of 1,3-butadiene on Tl-modified Pd catalyst

The selectivity and reactivity in the hydrogenation of 1,3-butadiene catalyzed by Tl-modified 5 wt% Pd/Al₂O₃ catalysts vary with amounts of Tl loading and with the reduction temperatures, that is, the main product was 1-butene and trans-2-butene for values of Tl loading of 0.5 and 2 in Tl/Pd atomic ratio, respectively, when the catalysts were reduced at 673 K. 1,3-butadiene was hydrogenated selectively towards 1-butene and trans-2-butene when the Tl modified 5 wt% Pd/Al₂O₃ catalyst of Tl/Pd = 2 was reduced at 300 and 373 K or above, respectively. On the catalyst with Tl/Pd = 2 reduced at 373 K or above, the butenes formed are not hydrogenated to butane, even after a long reaction time. These results suggest the formation of Pd-Tl alloy or intermetallic compounds during the reduction procedure which is responsible for the selectivity controlling in the reaction. TPR and XRD results were in consistence with the reaction data.     

研制一个用于研究（中子,带电粒子）反应的望远镜系统

文章讨论了一个研究(中子,带电粒子)反应双微分截面多路望远镜系统中△E和E探测器的选择、制作、刻度及性能测试。对CsI(Tl)探测器的非线性能量响应关系进行了精心刻度。研制的CsI(Tl)探测器,其性能达到国外同类装置的水平。     

Measurement of keV-Neutron Capture Cross Sections and Capture Gamma-Ray Spectra of 167 Er

The neutron capture cross sections and capture γ-ray spectra of ¹⁶⁷Er were measured in the neutron energy region of 10 to 90keV and at 550 keV. Using a neutron time-of-flight method with a 1.5-ns pulsed neutron source by the ⁷Li(p, n)⁷Be reaction, the measurement was performed by detecting prompt γ rays from an enriched capture sample with a large anti-Compton Nal(Tl) spectrometer. A pulse-height weighting technique was applied to observed capture γ-ray pulse-height spectra to extract capture yields. The capture cross sections were derived with the error of about 5% by using the standard capture cross sections of ¹⁹⁷Au. The present results were compared with the evaluated values of ENDF/B-VI and the previous measurement. The present measurement at 550 keV was the first one. The capture γ-ray spectra were obtained by unfolding the observed capture γ-ray pulse-height spectra. An anomalous shoulder was clearly observed around 3 MeV in the γ-ray spectra and the energy position of the shoulder was consistent with the systematics obtained in our previous work. The multiplicities of the observed γ rays were derived from the γ-ray spectra.     

Experiments on high excitation density, quenching, and radiative kinetics in CsI:Tl scintillator

Information on quenching as a function of electron-hole density through the range of 10¹⁹ to 2×10²⁰ e-h/cm³ typically deposited towards the end of an electron track has been acquired using 0.5 ps pulses of 5.9 eV light to excite in the band-to-band or high-exciton region of CsI and CsI:Tl. A streak camera records partially quenched luminescence from self-trapped excitons (STE) and excited activators (Tl^+?). Both the Tl^+? and STE luminescence exhibit decreasing light yield versus excitation density N_max, but it is only the 302 nm STE luminescence that exhibits decay time quenching dependent on N_max. Fitting the STE decay time data to a model of dipole-dipole quenching yields the time-dependent bimolecular rate constant for quenching of STEs (and Tl^+? light yield) in CsI at room temperature: k₂(t)=2.4×10⁻¹⁵ cm³ s^−1/2 (t^−1/2).     

Efficiency Determination for NaI (Tl) Detectors in the 23 keV to 1333 keV Energy Range

Abstract

The photopeak efficiency of a NaI (Tl) detector was determined experimentally for 23‐1333 keV photon energy by using polyester coated radioisotopes ²²Na, ⁵⁴Mn, ⁵⁷Co, ⁶⁰Co, ¹⁰⁹Cd, ¹³⁷Cs, and ¹³³Ba. The energy resolution of the NaI (Tl) detector was also measured. The data were analyzed using the Genie‐2000 from Canberra. The experimental values were fitted to an analytical function of photon energy and an agreement was observed for the entire range of the studied energies. The results have shown that the NaI (Tl) detector is a particularly attractive detector for field application, as it works at room temperature and has a high probability of detecting gamma radiation.     

Improvement of an Energy Spectrum by Means of a Timing Technique

Abstract

The constant fraction (CF) discrimination technique was applied to gamma rays emitted from a gamma source via a developed spectrometer. Experimental energy spectra, with and without the CF discrimination technique, were obtained separately. After the application of the technique, the spurious radiations on the low energy tail of the energy spectrum which had arisen from the low‐energy background, backscattering and Compton radiations were partly discriminated, leading to improvement in the energy spectrum.     

G(E)法与Gravel法处理能谱-剂量转换效果研究

为准确地得到γ射线的辐射剂量,对G(E)函数法和Gravel算法处理能谱-剂量的转换效果进行了研究。根据实际应用需求,采取蒙特卡罗方法模拟获取了?50 mm×50 mm NaI(Tl)探测器的Gravel法响应矩阵,并使用Matlab得到探测器的G(E)函数。使用NaI(Tl)探测器和多道谱仪系统测量标准源的能谱,分别使用G(E)法和Gravel法计算剂量值并与理论值进行比较,同时在计算过程中总结对比了两种方法的特点。     

NaI(Tl)γ谱的计算机稳峰技术

介绍了一种改进型NaI(Tl)γ谱仪的稳谱技术。该稳谱技术基于241Am源的等效γ峰作为系统的参考峰,根据参考峰位偏差运用数字PID调整可编程增益放大器来稳谱,是一种“硬件 参考源 软件”的稳谱技术。这种计算机稳谱技术具有稳定度高,稳谱速度快等优点。