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ABOVEGROUND OBSERVATION OF DARK MATTER USING A CRYOGENIC PARTICLE DETECTOR

使用低温粒子探测器对暗物质进行地面观测

基本信息

批准号：
07640420
负责人：
WATANABE Tadashi
金额：
$ 1.22万
依托单位：
TOKYO UNIVERSITY OF INFORMATION SICENCES
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

By using a cryogenic detector with the target composed of about 344,000 tinmicrospheres of 0.0354g weight (in 30 micron diameter each), we have carried out a preliminary observation of dark-matter candidate particles in cosmic rays. It was performed at the temperature of 30mK and the applied field of 326 Gauss by use of the signal-readout system with a damped resonance circuit (the resonant frequency of about 1 MHz).By analysing the temporal spacings of signals and the pulse height, we confirmed what follows :(1) When an incident particle causes multiple spheres flip at a time, it is a charged cosmic one with certainty. For a single transition signal, however, we are unable to infer it whether due to the usual cosmic ray or a dark-matter particle without taking an event-coincidence procedure.(2) For the 5-micron variance of the size of the tin spheres used the super-heating superconducting field varies widely from 250 to 400G at 30mK,which reduces the effective mass of the target. The precision of the diameter within 1 micron is desired for the narrower allowance of the field.(3) The uniform distribution of the microspheres in the filling stuff is also critically important. A transition of a single sphere, one of the target ones in close vicinity each other, may trigger the nearest neighbor one and the chain reaction occurs successively. Provided that the first transition has owed to the very dark-matter particle, the resultant chain reaction is inferred to be caused by a charged particle.In conclusion, the particle detector based on the phase transition of the superheated superconducting spheres has some issues yet to overcome, the precise selection of the sphere size, the progress of the readout system with a higher sensitivity and the target of unifomly distributed spheres.

我们利用低温探测器，对宇宙射线中的暗物质候选粒子进行了初步观测，探测目标为34.4万个重0.0354克（每个直径30微米）的锡微球。采用带阻尼谐振电路的信号读出系统（谐振频率约为1 MHz），在温度为30mK，外加326高斯的场域中进行了实验。通过分析信号的时间间隔和脉冲高度，我们证实了以下几点：(1)当一个入射粒子同时引起多个球体翻转时，它肯定是一个带电的宇宙球体。然而，对于一个单一的过渡信号，如果不采取事件巧合程序，我们无法推断它是由于通常的宇宙射线还是暗物质粒子。(2)对于使用的锡球尺寸的5微米差异，在30mK时，过热超导场在250 ~ 400G之间变化很大，这降低了目标的有效质量。直径的精度在1微米以内是为较窄的余量领域所期望的。(3)充填物料中微球的均匀分布也至关重要。单个球体的跃迁，相邻目标中的一个可能触发最近的一个，链式反应依次发生。假设第一次跃迁是由非常暗的物质粒子引起的，那么由此产生的链式反应就推断是由带电粒子引起的。综上所述，基于过热超导球相变的粒子探测器在球尺寸的精确选择、更高灵敏度的读出系统的进展以及球均匀分布的目标等方面还有待克服。