摘要
探测技术是脉冲辐射场诊断的关键和核心技术之一,它直接决定待测对象的种类、范围及测试数据的质量。为了获得脉冲辐射性能优异,可在极端环境下使用的新型半导体探测器件,本文开展了CVD金刚石薄膜探测器作为脉冲辐射探测器件的研究与探索。
首先开展了CVD金刚石薄膜探测器作为脉冲辐射探测器件的可行性研究。通过对目前国内外多批金刚石材料性能测试、器件制作及探测器性能研究,对“探测器级”金刚石薄膜材料提出结晶程度好、尤其要求杂质浓度低的选材准则,制作了欧姆接触良好,暗电流达10pA的高质量CVD金刚石薄膜探测器。
研究了CVD金刚石薄膜探测器的电荷收集特性。理论计算了电荷收集效率与探测器电场强度、规格尺寸的代数关系,分析了金刚石材料质量对电荷收集效率的影响。实验研究获得了所研制探测器的电荷收集效率和载流子寿命,验证了理论计算结果。研究表明,工作电场在2V/μm以上时,探测器可获得稳定的电荷收集效率,所研制探测器的电荷收集效率达60-70%,达到国际先进水平。
系统研究了CVD金刚石薄膜探测器的脉冲辐射特性。利用物理模型计算了探测器的时间响应波形,并在快脉冲紫外激光、X射线及质子束流上开展了相应的实验研究,获得了探测器时间性能指标及金刚石质量对探测器时间性能的影响。完成了探测器辐射响应(灵敏度、能量响应)、n/γ分辨能力的蒙特卡罗模拟计算,开展了探测器对脉冲γ射线、Z-pinch过程脉冲X射线、DPF装置脉冲中子/X射线混合场、BEPC II试验束装置脉冲电子束及国家串列加速器脉冲质子束的辐射响应实验研究。研究表明,所研制金刚石探测器的上升时间达440ps,其时间响应和辐射响应满足脉冲辐射场测量需求。
研究了探测器的耐辐照性能。在2×13MeV国家串列加速器HI-13装置开展了探测器对直流质子束的耐辐照实验研究,结果表明所研制的金刚石探测器的抗辐照能力比硅PIN探测器高3个量级。
本课题所研制的高质量CVD金刚石薄膜探测器具有暗电流小、时间响应快、抗辐照能力强等优点,为高强度脉冲辐射场的诊断提供了新的、性能更加优异的探测元件。
Radiation detection is one of the key technologies in the pulsed radiation field diagnosis. The thesis conducted studies on CVD diamond film detectors for pulsed radiation detection in the purpose of developing new semiconductor detectors which have higher properties and great tolerance of atrocious environment.
The possibility of CVD diamond film detectors for pulsed radiation detection is firstly researched. After times of material testing, detector preparing and researches on detector properties, the concept of“detector grade”diamond film which should have good lattice structures, especially have low impurity concentrations is concluded. Finally, high quality CVD diamond film detectors with good Ohmic contact and dark current as low as 10pA are prepared.
Charge collecting properties of CVD diamond film detectors are studied. The relationship between detector charge collection efficiencies with the electric field and detector sizes is derived, and the relationship between detector charge collection efficiencies with diamond qualities is discussed. The charge collection efficiencies and charge carrier lives of the detectors developed in the thesis are obtained. The results show that, the charge collection efficiencies reach the saturate region when the electric field is higher than 2V/μm. The charge collection efficiencies of the detectors developed in the thesis are as high as 60%-70%, which reach the advanced level of the world.
Pulsed radiation response properties of CVD diamond film detectors are systematically studied. Their time response waveforms are calculated using a physical mode, and the relevant experiments are finished on ultra-fast UV source, X rays and proton beams. Time response parameters of the detectors developed in the thesis and the relationship between the time response of diamond film detectors and diamond qualities are achieved. Basing on the Monte-Carlo calculations of the detectors’responses to radiation and n/γdiscrimination ability, their radiation response properties are experimentally investigated on pulsedγrays, X rays from Z-pinch processes, n/X mixed radiation fields of the DPF neutron generator, electron beams of BEPC II Testing Beam Facility. The results show that the best rise time of the detectors developed in the thesis is as fast as 440ps, their time response and sensitivities satisfy the requirements of pulsed radiation detection.
The radiation hardness are studied on the 2×13MeV Beijing Tandem Accelerator HI-13. The results show that the radiation hardness of detectors developed in the thesis is 3 grade higher than that of Si-PIN detectors.
It can be concluded that the CVD diamond film detectors developed in the thesis have high qualities of low dark currents, fast time response, high radiation hardness and they can be used as a better alternative detectors in the high intensity pulsed radiation diagnosis.
引文
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