Development and evaluation of a collection apparatus for recoil products for study of the deexcitation process of 235mU
Development and evaluation of a collection apparatus for recoil products for study of the deexcitation process of 235mU
复制标题
用于研究235mU去励磁过程的反冲产物收集装置的开发和评估
DOI：
10.1063/1.4950900
复制
发表时间：
2016
影响因子：
1.6
通讯作者：
and A. Shinohara
中科院分区：
文献类型：
--
作者：
Y. Shigekawa;Y. Kasamatsu;and A. Shinohara
原子核{sup 235m}U是一种激发能极低（76.8 eV）的异构体，主要通过内转换（IC）过程衰变。由于IC过程涉及到外层电子，所以U的衰变常数取决于它的化学环境。我们计划通过测量IC电子的能谱和各种化学形式的衰变常数来研究U的去激发过程。本文报道了利用α -反冲能从{sup 239}Pu中制备{sup 235}U样品的方法。制作了反冲产物收集装置，并通过收集{sup 228}Th电沉积源和沉淀源中反冲的{sup 224}Ra，测定了不同条件下的收集效率。装置内的压力（真空或1atm的N{sub 2}气体）会根据施加在收集器上的负电压影响收集效率的变化。收集效率的最大值主要受{sup 228}Th源厚度的影响。根据这些结果，确定了{sup 239}Pu源制备{sup 235}U的适宜条件。此外，通过用溶液洗涤收集的{sup 224}Ra来测定溶解效率。将{sup 224}Ra收集于1atm的N{sub 2}气体中，与水等极性溶液溶解，其溶解效率接近100%。快速溶解反冲产物的方法适用于快速制备各种化学形式的短寿命U样品。
The nucleus {sup 235m}U is an isomer with extremely low excitation energy (76.8 eV) and decays dominantly through the internal conversion (IC) process. Because outer-shell electrons are involved in the IC process, the decay constant of {sup 235m}U depends on its chemical environment. We plan to study the deexcitation process of {sup 235m}U by measuring the energy spectra of IC electrons in addition to the decay constants for various chemical forms. In this paper, the preparation method of {sup 235m}U samples from {sup 239}Pu by using alpha-recoil energy is reported. A Collection Apparatus for Recoil Products was fabricated, and then collection efficiencies under various conditions were determined by collecting {sup 224}Ra recoiling out of {sup 228}Th electrodeposited and precipitated sources. The pressure in the apparatus (vacuum or 1 atm of N{sub 2} gas) affected the variations of the collection efficiencies depending on the negative voltage applied to the collector. The maximum values of the collection efficiencies were mainly affected by the thickness of the {sup 228}Th sources. From these results, the suitable conditions of the {sup 239}Pu sources for preparation of {sup 235m}U were determined. In addition, dissolution efficiencies were determined by washing collected {sup 224}Ra with solutions. When {sup 224}Ra was collected in 1 atm of N{sub 2} gas and dissolved with polar solutions such as water, the dissolution efficiencies were nearly 100%. The method of rapid dissolution of recoil products would be applicable to rapid preparation of short-lived {sup 235m}U samples for various chemical forms.