Development of high resolution silicon surface barrier detectors

Fabrication methods for silicon surface barrier detectors and their correlated properties which result in the production of high resolution (< 20 keV) devices have been studied. The techniques for fabrication and testing of the detectors currently employed at our Centre are presented. An FWHM of 14keV for 5·486 MeV²⁴¹Am α has been achieved. Our results are therefore comparable with the best in the world.     

Dead time corrections to photon counting statistics II: Quantum theory

The recent formulation of the quantum theory of photodetection, based on the quantum theory of continuous measurements, is extended to the case of a (nonideal) detector which has non-zero dead time. A general result is proven which expresses the dead time modified counting statistics in terms of the counting statistics of anassociated ideal detector. As an illustration, the dead time corrections to the counting statistics of a single-mode free field are worked out, and these corrections are shown to be identical in form to the dead time corrections for a classical optical field of constant intensity.     

Determination of phenols by HPLC down to PPT levels

Summary A mixture of eleven priority pollutant phenols (PPP) have been separated using a Dionex 4000 chromatograph; VAL-U-PAK ODS (250 × 4.6 mm I.D.) column; eluents A: CH₃CN/0.2M NaH₂PO₄/CH₃COOH 40/60/1 and B: CH₃CN with/without gradient; detectors: UV-254 nm and Pulse Amperometric Detector (PAD) with glassycarbon electrode (+1.20V). With preconcentration unit (guard RP-18 column) on line and PAD, detectability limit at ten ppt was achieved. The method has been applied for determination of PPP in tap-water and in leachates from sanitary and industrial landfill sites.     

Time-resolved photoluminescence study of AgCl:Cd solid state nuclear track detectors

Crystalline AgCl:Cd²⁺ thin foils (Cd²⁺ concentration 62.5 – 5000 ppm) were studied by time-resolved photoluminescence spectroscopy in temperature range 20 – 80K using a mechanical phoroscope. Simple method is presented how to use the photoluminescence behaviour to check suitability of AgCl:Cd²⁺ foils to record high-energy particles tracks.     

Retention prediction system coupled with a multichannel ultraviolet detector for the identification of polycyclic aromatic hydrocarbons

Summary The retention prediction system assisted by a micro-computer coupled with an UV multichannel detector has been investigated in the separation of polycyclic aromatic hydrocarbons. The method offered very precise identification of components in NBS-SRM-1647 sample without any standard reference substances. It has been proven that the system makes very precise, non-pollutive and convenient environmental analysis possible.     

超巨磁电阻薄膜在光探测上的新应用

混合价态钙钛矿锰氧化物在外界温度变化和磁场作用下表现出巨大的磁电阻(colossal magnetoreslstance，简记为CMR)效应，引起了人们的广泛关注．由于CMR材料在传感器、探测器以及硬盘读出磁头等应用器件研发上极具潜力，科学家们对其进行了大量研究．文章在简单介绍CMR材料结构和机理的基础上，着重报道了作者利用CMR薄膜的激光感生热电电势(LITV)制备激光功率／能量探测器和利用电阻在室温附近的巨大变化研制光热辐射探测器(bolometer)方面的新进展．     

Radon exhalation studies in building materials using solid-state nuclear track detectors

Indoor radon has been recognized as one of the health hazards for mankind. Building materials constitute the second most important source of radon in dwellings. The common building materials used in the construction of dwellings are studied for radon exhalation rate. The ‘Can’ technique using LR-115 type-II solid-state nuclear track detector has been used for these measurements. The radon exhalation rate in these samples varies from 4.75 m Bq m⁻² h⁻¹ (0.14 m Bq kg⁻¹ h⁻¹) for limestone to 506.76 m Bq m⁻² h⁻¹ (15.24 m Bq kg⁻¹ h⁻¹) for soil.     

在改进的等离子体源质谱仪中加入电光离子检测器

从整个质谱学的历史来看，阵列检测器一直用来进行同时和连续的质谱测量研究。利用阵列检测器获取多道数据的好处已为人们所熟知，这包括较大的占空因素、供助比值和内标技术改善的精度以及对快信号瞬变过程较好的定量分析，由于有这些好处，多种基于阵列检测器的测量仪器得到开发，包括光学的和质谱仪，本文描述配备多道电光离子检测器的等离子体源Mattauch-Herzog质谱仪改善了性能，所有的实验均采用一个辉光放电源，过去报道的这台质谱仪的基于阵列检测器的数据在质量方面受到严重的局限,谱峰形状和分辨率都极差。本文将介绍与阵列检测器有关的几个性能指数，这包括灵敏度、分辨率、谱峰形状以及同位素灵敏度。所有这些性能指数都得到明显的改善。阵列检测器性能方面有待解决的问题包括对磁场的敏感性以及在整个阵列表面灵敏度缺乏均匀性。