Dersch R
Physikalisch-Technische Bundesanstalt, Bundesallee 100, Braunschweig 38116, Germany.
Appl Radiat Isot. 2004 Feb-Apr;60(2-4):387-90. doi: 10.1016/j.apradiso.2003.11.046.
In the past few years, a primary measurement system has been established at the PTB allowing absolute measurements of 222Rn. The activity can be determined by counting the emitted alpha particles in a defined solid angle after condensing the radon at a cold point under vacuum conditions. This primary measurement system is connected to a solid 226Ra source, where 222Rn can be produced up to an activity of about 2MBq. After the measurement, radon can be completely transferred into a glass bulb or a stainless steel cylinder for use as a transfer standard. The results of the measurements, the uncertainties and the realization of the primary measurement system are described. For quality assurance and fast determination of radon activity, a secondary measurement system with an NaI(Tl) detector is also used. Together, both systems provide a reliable tool for the production of gaseous 222Rn activity standards with relative uncertainties of less than 1%.
在过去几年里，德国物理技术研究院（PTB）建立了一个用于绝对测量²²²Rn的初级测量系统。通过在真空条件下将氡冷凝在一个冷点后，在限定的立体角内对发射的α粒子进行计数，即可确定其活度。该初级测量系统连接到一个固态²²⁶Ra源，在那里可以产生高达约2MBq活度的²²²Rn。测量完成后，氡可以完全转移到一个玻璃泡或一个不锈钢圆筒中，用作传递标准。文中描述了测量结果、不确定度以及初级测量系统的实现情况。为了保证质量并快速测定氡活度，还使用了一个配备碘化钠（铊）探测器的次级测量系统。这两个系统共同为生产相对不确定度小于1%的气态²²²Rn活度标准提供了一个可靠的工具。
