d'Errico F, Matzke M
Department of Therapeutic Radiology, Yale University, New Haven, CT, USA.
Radiat Prot Dosimetry. 2003;107(1-3):111-24. doi: 10.1093/oxfordjournals.rpd.a006380.
The BINS neutron threshold spectrometer permits the analysis of the main features of a neutron field for radiation protection purposes. The system offers a virtually complete photon discrimination and nested threshold responses to neutrons, which allow the use of very effective 'few-channel' unfolding procedures. To date, the practical operating energy range of a BINS is 0.1-10 MeV, over which a resolving power of 20-30% can be expected when the deconvolution is performed without explicit pre-information. Spectrum unfolding results in relatively high uncertainties on the differential fluence distributions, but due to negative correlations in adjacent energy groups the uncertainties on integral quantities such as dose equivalent are small and of the order of 5% to 10%, similar to the results of other active spectrometers. In comparison with most radiation detectors, the BINS is an extremely slow system due to the intrinsic duration of a bubble pulse and to the time associated with pulse analysis. For example, the maximum sustainable fluence rate of 1 MeV neutrons is about 10(4) cm(-2) s(-1), which is low for many neutron physics experiments. However, this rate corresponds to an ambient dose equivalent rate of about 1 mSv h(-1), making the active device adequate for radiation protection applications in the workplaces described in Section 1. There are ample margins for improvement of the spectrometer. In particular, in the low-energy region a thermal-epithermal neutron group may be added by using chlorine-bearing emulsions stabilised at suitable temperatures. In fact, the latest version of the system achieves this goal by using a single superheated emulsion of dichlorotetrafluoroethane (R-114) operated at temperatures up to 55 degrees C. This extends the range of the spectrometer and at the same time removes the undue enhancement of the UNFANA output in the low energy region. Above 10 MeV, the resolution can be improved by adding more thresholds, e.g. by starting from a lower initial temperature and using finer temperature increments. Based on neutron kinematics, the theoretical upper energy threshold which can be generated with superheated emulsions is greater than 100 MeV. However, this would most likely require refrigerating the detectors, while the current simpler approach is to operate the detectors at incremental temperature steps starting from the ambient temperature. A range that should be easily achieved in practice is from thermal energies to 20 MeV.
BINS中子阈值谱仪可用于分析中子场的主要特征，以实现辐射防护目的。该系统几乎能完全区分光子，并对中子有嵌套阈值响应，这使得可以使用非常有效的“少通道”解谱程序。到目前为止，BINS的实际工作能量范围是0.1 - 10 MeV，在没有明确先验信息进行反卷积时，预计在此能量范围内分辨能力为20% - 30%。谱解谱在微分注量分布上会导致相对较高的不确定性，但由于相邻能量组中的负相关性，诸如剂量当量等积分量的不确定性较小约为5%至10%，与其他有源谱仪的结果类似。与大多数辐射探测器相比，由于气泡脉冲的固有持续时间以及与脉冲分析相关的时间，BINS是一个极其缓慢的系统。例如，1 MeV中子的最大可持续注量率约为10⁴ cm⁻² s⁻¹，这对于许多中子物理实验来说较低。然而，这个速率对应于约1 mSv h⁻¹的环境剂量当量率，使得该有源设备适用于第1节所述工作场所的辐射防护应用。该谱仪有很大的改进空间。特别是在低能区，可以通过使用在合适温度下稳定的含氯乳剂来增加一个热 - 超热中子组。实际上，该系统的最新版本通过使用在高达55摄氏度下运行的二氯四氟乙烷（R - 114）单一过热乳剂实现了这一目标。这扩展了谱仪的范围，同时消除了低能区UNFANA输出的不适当增强。在10 MeV以上，可以通过增加更多阈值来提高分辨率，例如从较低的初始温度开始并使用更精细的温度增量。基于中子运动学，用过热乳剂可产生的理论能量上限大于100 MeV。然而，这很可能需要对探测器进行制冷，而目前更简单的方法是从环境温度开始以递增的温度步长操作探测器。在实际中应该很容易实现从热能到20 MeV的范围。
