DETECTION OF LOW LEVEL ALPHA EMITTING MATERIAL USING A BRAGG CURVE COUNTER

使用布拉格曲线计数器检测低水平阿尔法发射材料

• 批准号: 05640360
• 负责人: KIMURA Kikuo
• 金额: $ 1.41万
• 依托单位: NAGASAKI INSTITUTE OF APPLIED SCIENCE
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1993
• 资助国家: 日本
• 起止时间: 1993 至 1994
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05640360/
• 关键词: Bragg curve counter; Multi-wire proportional counter; Alpha radioactive material; Environmental radioactivity; 多線比例係数管; 環境放射能; 電離箱; 比例計数管

Background CountingA Bragg curve counter using a multi-wire proportional chamber was constructed and the background level of this counter was measured.A raw counting rate was about one per minute.Since all the counts were recorded as waveform data of output signals, it was determined whether each signal was due to an alpha particle or not and what angle did the particle entered into the counter by analyzing waveform data.As a result of this, alpha particles emitted around the place where a test sample will be located was found to be 4 counts per hour.This remains as a final background which cannot be rejected even by applying wavefrom cut.Since this background looked to originate from alpha emitters contained in the counter material, the material was replaced by a less alpha emitting one.Then the final background was reduced to 0.4 count per hour.Measurement using an environmental sampleAlpha particle counting form a lead sheet used as a painting tube was made by the Bragg curve counter.The events which looked to be alpha particles emitted from the place near the lead sample were selected from the raw data.It was found that the number of events when the lead sample was placed were about 10 times larger than that without the sample, that is, S/N-ratio was about 10.This result was obtained for the sample of continuous alpha spectrum.For the sample of discrete spectrum S/N is expected to be much higher than this value if the source strength is same.Thus the alpha counting system now constructed can be applicable to low level alpha counting of various environmental materials if combined with the extracting technique of alpha emitting material.

本底计数采用多丝正比室构成布拉格曲线计数器，测量了该计数器的本底水平。原始计数率约为每分钟一个。由于所有计数都记录为输出信号的波形数据，因此通过分析波形数据来确定每个信号是否由α粒子引起以及粒子进入计数器的角度。结果，在测试样品所在位置周围发射的α粒子被发现是每小时4个计数。这仍然是最终的背景，即使通过应用waveform cut也不能被拒绝。因为这个背景看起来来自计数器材料中包含的α发射体，用一种α辐射较少的材料代替这种材料，然后将最终的本底减少到每小时0.4个计数。使用环境样品进行测量α粒子计数表用布拉格曲线计数器制作了一张用作画管的铅片，从原始数据中选取了看起来像是从铅样品附近发射的α粒子的事例，发现放置铅样品时的事例数比没有放置样品时的大10倍左右，即，这一结果是对连续α谱样品得到的，对离散谱样品得到的S/N比约为10。在源强相同的情况下，N值可望远大于这个值，因此，我们所建立的α计数系统可以适用于低水平的α计数如果与α发射材料的提取技术相结合，则可以对各种环境材料进行α计数。