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Particle Identification of High-Energy Heavy Ions by a Tilted Electrode Gas Ionization Chamber

倾斜电极气体电离室对高能重离子的粒子识别

基本信息

批准号：
14540284
负责人：
KIMURA Kikuo
金额：
$ 2.24万
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 Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14540284/
关键词：
Gas Ionization Chamber Unstable Nucleus Beam Particle Identification RI Beam Factory Heavy Ion 高エネルギー重イオン RIビームガス電離箱粒子識別

项目摘要

A high rate particle identification device for high-energy heavy ions, which is intended to be used in the forthcoming RI beam factory has been developed. A gas detector named tilted electrode gas ionization chamber was constructed and was tested at the RIKEN ring cyclotron. Gas length dependence of the detector resolution was measured using nuclear fragments of 56Fe. It was found that the resolution was nearly proportional to inverse square of gas length just as expected when the resolution is determined simply by statistical fluctuations of ionization loss. But the resolution does not tend to zero toward the infinite gas length and has a small offset. This offset value increases with the increase of the atomic number Z of the detected particles. Up to Z=25, the resolution remains well within the acceptable value. But if we extrapolate the increasing trend toward larger Z, the resolution exceeds the acceptable value around Z=50. The reason of this deterioration of the resolution seems to be due to the electrode foils used in our detector. It is thus necessary to use thinner foils for the identification of heavy ions around Z=50.Counting rate dependence of the detector resolution was measured using nuclear fragments of 40Ar. In this measurement two kinds of gas mixtures, Ar-CH4 and Ar-CF4, were compared. It was found that the resolution of the gas mixture Ar-CH4 is very good up to a counting rate of 300kcps but deteriorates rapidly above this counting rate. In contrast to this, the resolution of the gas mixture Ar-CF4 was found to be almost constant up to the measured maximum counting rate 1Mcps. The better rate dependence of the gas mixture Ar-CF4 is probably due to a larger electron drift velocity of this gas compared to the gas mixture Ar-CH4. As for high-rate operation of the detector, a satisfactory result was obtained.

一种用于高能重离子的高速粒子识别装置已经研制成功，该装置将用于即将建成的RI束流工厂。建立了一种气体探测器--倾斜电极气体电离室，并在RIKEN环形回旋加速器上进行了测试。用56Fe核碎片测量了探测器分辨率与气体长度的关系。结果表明，当分辨率仅由电离损耗的统计涨落决定时，分辨率几乎与气体长度的平方成反比。但分辨率并不趋向于在无限长的气体中趋于零，并且有一个很小的偏移量。这个偏移值随着被检测粒子的原子序数Z的增加而增加。直到Z=25，分辨率仍保持在可接受的范围内。但如果我们外推增大Z的趋势，分辨率将超过Z=50左右的可接受值。分辨率下降的原因似乎是由于我们探测器中使用的电极箔。因此，有必要使用更薄的薄片来识别Z=50附近的重离子。用40Ar的核碎片测量了探测器分辨率的计数速率关系。在测量中，比较了Ar-CH4和Ar-CF4两种混合气体。结果表明，Ar-CH4混合气体在300kcps的计数速率下具有很好的分辨率，但超过300kcps的计数速率后，分辨率急剧下降。与此相反，气体混合物Ar-CF4的分辨率在测量的最大计数速率1Mcps时几乎是恒定的。Ar-CF4混合气体比Ar-CH4混合气体具有更好的速率依赖性，这可能是因为这种气体的电子漂移速度比Ar-CH4混合气体大。对于探测器的高速率工作，获得了满意的结果。