2003 Fiscal Year Final Research Report Summary
Particle Identification of High-Energy Heavy Ions by a Tilted Electrode Gas Ionization Chamber
| Project/Area Number |
14540284
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
素粒子・核・宇宙線
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| Research Institution | Nagasaki Institute of Applied Science |
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Principal Investigator |
KIMURA Kikuo Nagasaki Institute of Applied Science, Engineering, Professor, 工学部, 教授 (60108636)
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| Project Period (FY) |
2002 – 2003
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| Keywords | Gas Ionization Chamber / Unstable Nucleus Beam / Particle Identification / RI Beam Factory / Heavy Ion |
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| Research Abstract |
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.
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