2004 Fiscal Year Final Research Report Summary
Change of a Decay Constant of ^<40>K under Ultra High Pressure
| Project/Area Number |
15340082
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Particle/Nuclear/Cosmic ray/Astro physics
|
|---|
| Research Institution | Nishinippon Institute of Technology |
|---|
Principal Investigator |
ODAHARA Atsuko Nishinippon Inst.of Tech., Fac.of Tech., AP, 工学部, 助教授 (30264013)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
GONO Yasuyuki RIKEN, Cyclotron Center, Researcher, 加速器基盤研究部, 研究嘱託 (50016127)
ISOZUMI Yasuhito Kyoto Univ., RI Center, Professor, 放射性同位元素総合センター, 教授 (50027603)
KIKEGAWA Takumi KEK, PF, Researcher, 物質構造科学研究所・物質化学第2研究系, 助手 (70195220)
MOCHIZUKI Yuko RIKEN, Cyclotron Center, Researcher, 加速器基盤研究部, RIBFプロジェクトスタッフ (90332246)
|
|---|
| Project Period (FY) |
2003 – 2004
|
| Keywords | change of a decay constant / electron capture decay / high pressure / ^<40>K / Compton camera |
|---|
| Research Abstract |
A change of a decay constant of ^<40>K with life time of 1.28 x 10^9 year under ultra high pressure is interested in the region of nuclear physics and earth science.
As much amount of ^<40>K chemical compound is included in the earth, the γ-ray of 1461keV is easily observed as a natural background. In order to exclude this natural background γ-ray, tests of two methods were carried out. First method is to shield Ge detectors by using lead bricks. Second method is to use Compton camera which can make the image of the distribution of the γ-ray source. By selecting events that the only γ-rays are emitted from the source position, it was found that the back ground γ-rays could be reduced about 94 %. This effect corresponds to that by a shield of the 4.7 cm thick lead bricks. The former method was adopted, as it is crucial the good statistics. Photo peak efficiency in former case is more by 10^5 times than that in the latter case.
New type of diamond anvil cell was developed to install the amount of 1 mg ^<40>KCl powder. Measurements of pressure were carried out in KEK-PF.
As high-pressure is considered to affect the density of atomic electrons, decay rate of electron capture is supposed to change. Based on this consideration, change of decay constant was also theoretically estimated.
Measurements of γ-rays after electron capture decay of ^<40>K under high pressure of 8.7, 11.4 and 20.1 GPa were carried out in the prefab building at RIKEN. As this results, the accuracy of this measurements was 〜10^<-2>. This was considered to be caused by the problems of Ge detectors, shield configuration of lead bricks, stability of DAQ, method of analysis of γ-ray spectra and so on. We will continue this study in order to obtain the good statistics and the accuracy to be 10^<-3>.
|
