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Nuclear asrophysics with low energy beams of short-lived nuclei

短寿命原子核低能束的核天体物理学

基本信息

批准号：
62540206
负责人：
SHIMODA Tadashi
金额：
$ 1.22万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1987
资助国家：
日本
起止时间：
1987 至 1988
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-62540206/
关键词：
Ion-Trapping In Liquid Helium Long Lifetime Of Trapping Ion-Source For Beams Of Radio-Active Nuclei Small Beam Emittance Thermo-Nuclear Reactions Via Radioactive Nuclei 液体ヘリウム中のイオンイオンの閉じ込め閉じ込め効率取り出し効率天体熱核反応

项目摘要

We have investigated the possible use of liquid helium as an effective ion-source for beams of radio-active nuclei, which open up studies of nuclear synthesis via reactions associated with unstable nuclei under environments of very high temperature and high density such as in novae. An ion introduced into the liquid helium gathers many helium atoms around itself due to the electrostriction and the ion is trapped in the cluster of helium atoms. This charged cluster is referred to as "snowball" When the ions of radioactive nuclei produced in nuclear reactions are stopped and trapped in very low temperature liquid helium, the extracted beams from the liquid will have very small emittance.The feasibility of such ion-source relies on achieving (i) the high efficiency in forming the snowball, (ii) long lifetime of the snowball and (iii) high efficiency in extracting the ions from the liquid. We have examined the characteristics of the snowball in the following experiments; ions of ^<14>N with energy of 90 MeV are implanted into the liquid helium, and the ion currents have been measured under the electric fields applied in correlation with the beam pulse. The results we obtained are as follows:(1) The lifetime of the snowball was found to be about 700 ms, which is much longer than in the other methods of ion trapping.(2) The ion current depended much on the electron density around the ion in the liquid. This implies that the efficiency in forming the snowball may be increased by decreasing the implantation energy of the ions and by increasing applied field.(3) The mobility of the snowball was much larger in the superfluid helium than in the normal helium. Therefor more rapid control of the snowball is possible in the superfluid. In summary the liquid helium ion-source for the radio-active nuclear beams is quite promising.

我们研究了液氦作为放射性核束的有效离子源的可能性，这开启了在新星等非常高温和高密度的环境下，通过与不稳定核相关的反应进行核合成的研究。由于电致伸缩，引入液氦的离子在其周围聚集了许多氦原子，离子被困在氦原子团中。当核反应中产生的放射性核离子停止并被困在极低温度的液氦中时，从液体中提取的束流将具有很小的发射率。这种离子源的可行性取决于(1)形成雪球的高效率，(2)雪球的长寿命和(3)从液体中提取离子的高效率。我们在以下实验中考察了雪球的特性：将能量为90 MeV的~(14)N离子注入到液氦中，并在与束流脉冲相关的电场作用下测量了离子电流。我们得到的结果如下：(1)雪球的寿命约为700ms，比其他离子捕获方法的寿命要长得多。(2)离子流很大程度上依赖于液体中离子周围的电子密度。这意味着可以通过降低离子注入能量和增加外加电场来提高雪球的形成效率。(3)雪球在超流氦中的迁移率远大于在正常氦中的迁移率。因此，在超流体中更快速地控制雪球是可能的。综上所述，用于放射性核束的液氦离子源是很有前途的。