New experimental measurement of natSe(n, γ) cross section between 1 eV to 1 keV at the CSNS Back-n facility

The ⁷⁴Se is one of 35 p-nuclei, and ⁸²Se is a r-process only nucleus, and their (n, γ) cross sections are vital input parameters for nuclear astrophysics reaction network calculations. The neutron capture cross section in the resonance range of isotopes and even natural selenium samples has not been measured. Prompt γ-rays originating from neutron-induced capture events were detected by four C₆D₆ liquid scintillator detectors at the Back-n facility of China Spallation Neutron Source (CSNS). The pulse height weighting technique (PHWT) was used to analyze the data in the 1 eV to 100 keV region. The deduced neutron capture cross section was compared with ENDF/B-VIII.0, JEFF-3.2, and JENDL-4.0, and some differences were found. Resonance parameters were extracted by the R-matrix code SAMMY in the 1 eV-1 keV region. All the cross sections of ^natSe and resonance parameters are given in the datasets. The datasets are openly available at http://www.doi.org/10.11922/sciencedb.j00113.00019.     

Coherent phonon dynamics in short-period InAs/GaSb superlattices

We have performed ultrafast pump-probe spectroscopy studies on a series of InAs/GaSb-based short-period superlattice (SL) samples with periods ranging from 46 Å to 71 Å. We observe two types of oscillations in the differential reflectivity with fast (∼$\sim$1–2 ps) and slow (∼$\sim$24 ps) periods. The period of the fast oscillations changes with the SL period and can be explained as coherent acoustic phonons generated from carriers photoexcited within the SL. This mode provides an alternative method for determining the SL period. The period of the slow mode depends on the wavelength of the probe pulse and can be understood as a propagating coherent phonon wavepacket modulating the reflectivity of the probe pulse as it travels from the surface into the sample.     

微分吸收法测量二极管电压

给出了微分吸收法测量二极管电压的基本原理和实验结果。利用MCNP程序对轫致辐射-衰减-探测器系统建模,模拟得到了输出剂量与二极管工作电压关系拟合曲线。建立了微分吸收法测量二极管电压测量系统,通过在探测器前端放置不同厚度的吸收片,得到了衰减程度不同的波形。结合理论计算的拟合曲线和实验波形,利用迭代法计算得到了晨光号加速器二极管电压,电压峰值为0.58 MV。和传统方法所测得二极管工作电压进行了比较,结果较为一致。     

Comparison of Lu3Al5O12:Pr and Bi4Ge3O12 scintillators for gamma-ray detection

The scintillation properties of Lu₃Al₅O₁₂:Pr³⁺ (LuAG:Pr) single crystal grown by the Czochralski method with praseodymium concentration of 0.19 mol% were investigated. For a comparison, a good quality Bi₄Ge₃O₁₂ (BGO) single crystal grown by Bridgman method was also studied. The light yield and energy resolution were measured using photomultiplier tube (XP5200B PMT) readout. Moderate light yield of 15,900 photons per MeV was measured for the LuAG:Pr(0.19%) crystal. For 662 keV gamma rays (¹³⁷Cs source), an energy resolution of 6.5% obtained for LuAG:Pr(0.19%) is much better than that of 9.0% obtained for BGO. The light yield non-proportionality and energy resolution versus energy of gamma rays were measured and the intrinsic resolution of the crystals was determined after correcting the measured energy resolution for PMT statistics. The LuAG:Pr(0.19%) showed a good proportionality of the light yield within 5% over the energy range from 1274.5 keV down to 32 keV, which is much better than that of 14% for BGO. The photofraction was determined at 320 and 662 keV for both crystals and compared with the ratio of the cross-sections for the photoelectric effect to the total one calculated using WinXCOM program.     

组合透镜法测量透镜焦距方法研究及数值分析

为了解决神光系列装置所需长焦透镜焦距的检测问题,在现有斐索干涉仪的基础上,对常规组合透镜方法进行了拓展,提出了双探头光栅尺法。对两种方法的工作原理及检测方法进行了分析,同时计算分析了测量数据误差对测量结果的影响,得出测量数据测量误差的上限要求。这两种方法具有测量精度高、重复性好、测量过程简单的优点,对于各类透镜焦距的检测具有重要的实用价值。     

光子计数位置灵敏探测器畸变多项式校正

采用多项式校正方法对光子计数位置灵敏探测器成像畸变进行校正。介绍光子计数位置灵敏探测器工作原理并分析其畸变产生原因;介绍多项式校正原理,并给出光子计数位置灵敏探测器畸变多项式校正流程;采用该方法对两种不同畸变程度的基于楔条形阳极该类探测器进行了畸变校正,校正后残余误差分别为2.5pixel和1.2pixel。实验结果表明,多项式校正法能够有效校正光子计数位置灵敏探测器成像畸变。     

Comparison of Amperometric and Coulometric Electrchemical Detectors for HPLC Through a Figure of Merit

Abstract

Performance characteristics of electrochemical detectors for high performance liquid chromatooraphy are difficult to predict from presently avaliable information relating response to design parameters. A fiqure of merit is proposed which allows an operational comparison to be made, based upon specific response, noise and band spread. On this basis, it is shown that a meaningful comparison of an amperometric design with a coulometric design can be obtained and that, contrary to previous predictions, this coulometric type is generally superior.     

发光二极管诱导荧光检测器*

发光二极管诱导荧光检测器（LED-IF）是近十年来发展起来的一种微型化荧光检测器,在流动注射、毛细管液相色谱、毛细管电泳及芯片电泳等微流动分析系统中具有广泛的应用。本文讨论了LED-IF的4种光学结构,并对其主要器件,包括光源、滤光片、透镜、光纤、光电检测器以及检测池作了详细讨论,还介绍了LED-IF与其它技术的联用及其在生物、医药和环境样品检测中的应用,对未来的发展趋势作了展望。     

Compensation for thermal effects in mirrors of gravitational wave interferometers

In this paper we study several means of compensating for thermal lensing which, otherwise, should be a source of concern for future upgrades of interferometric detectors of gravitational waves. The methods we develop are based on the principle of heating the cold parts of the mirrors. We find that thermal compensation can help a lot but can not do miracles. It seems finally that the best strategy for future upgrades (“advanced configurations”) is may be to use thermal compensation together with another substrate materials than silica, for example sapphire. Received 26 April 2001     

Noise Characterization for Laser Interferometer Gravitational Wave Detectors

This work incorporates a review of the status, in Australia, of data analysis for gravitational wave detection using laser interferometers, within an overview of the present state of such research in the world generally. In this context, data analysis refers not so much to signal simulation as to what might be called the thorough process of noise characterization and the subsequent, quality-controlled signal extraction. To the extent that problems identified here arise for all currently planned instruments, there is necessarily a global component to the discussion presented. In Australia, there are unique circumstances, associated with attempting to carry out work in gravitational wave detection, which demand also a local aspect to the ensuing discussion.