Production and characterization of a custom-made ²²⁸Th source with reduced neutron source strength for the Borexino experiment

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• 作者：W. Maneschg^a ; ^{werner.maneschg@mpi-hd.mpg.de} ; L. Baudis^b ; R. Dressler^c ; K. Eberhardt^d ; R. Eichler^c ; H. Keller^d ; R. Lackner^a ; B. Praast^d ; R. Santorelli^b ; J. Schreiner^a ; M. Tarka^b ; B. Wiegel^e ; A. Zimbal^e
• 关键词：Solar neutrinos ; External background ; Thorium ; Neutron source strength ; Low-radioactivity
• 刊名：Nuclear Instruments and Methods in Physics Research Section A ; Accelerators ; Spectrometers ; Detectors and Associated Equipment
• 出版年：2012
• 期刊代码：41_01689002
• 类别：ph
• 出版时间：11 July, 2012
• 卷：680
• 期：Complete
• 页码：161-167
• 文件大小：824 K

摘要

A custom-made ²²⁸Th source of several MBq activities was produced for the Borexino experiment to study the external background of the detector. The aim was to reduce the unwanted neutron emission produced via reactions in ceramics typically used for commercial ²²⁸Th sources. For this purpose a ThCl₄ solution was chemically converted into ThO₂ and embedded in a gold foil.

The paper describes the production of the custom-made source and its characterization by means of , dose rate and neutron source strength measurements. From measurements it was deduced that activity transfer from the initial solution to the final source was (at 68%C.L.) and the final activity was (5.41卤0.30) MBq. The dose rate was measured with two dosimeters yielding 12.1 mSv/h and 14.3 mSv/h in 1 cm distance. The neutron source strength of the 5.41 MBq ²²⁸Th source was determined to be (6.59卤0.85) s^鈭?.