Zygmanski Piotr, Sajo Erno
Department of Radiation Oncology, Brigham and Women's Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts 02115.
Department of Physics and Applied Physics, Medical Physics Program, University of Massachusetts Lowell, Lowell, Massachusetts 01854.
Med Phys. 2016 Jan;43(1):4. doi: 10.1118/1.4935531.
The authors introduce a radiation detection method that relies on high-energy current (HEC) formed by secondary charged particles in the detector material, which induces conduction current in an external readout circuit. Direct energy conversion of the incident radiation powers the signal formation without the need for external bias voltage or amplification. The detector the authors consider is a thin-film multilayer device, composed of alternating disparate electrically conductive and insulating layers. The optimal design of HEC detectors consists of microscopic or nanoscopic structures.
Theoretical and computational developments are presented to illustrate the salient properties of the HEC detector and to demonstrate its feasibility. In this work, the authors examine single-sandwiched and periodic layers of Cu and Al, and Au and Al, ranging in thickness from 100 nm to 300 μm and separated by similarly sized dielectric gaps, exposed to 120 kVp x-ray beam (half-value thickness of 4.1 mm of Al). The energy deposition characteristics and the high-energy current were determined using radiation transport computations.
The authors found that in a dual-layer configuration, the signal is in the measurable range. For a defined total detector thickness in a multilayer structure, the signal sharply increases with decreasing thickness of the high-Z conductive layers. This paper focuses on the computational results while a companion paper reports the experimental findings.
Significant advantages of the device are that it does not require external power supply and amplification to create a measurable signal; it can be made in any size and geometry, including very thin (sub-millimeter to submicron) flexible curvilinear forms, and it is inexpensive. Potential applications include medical dosimetry (both in vivo and external), radiation protection, and other settings where one or more of the above qualities are desired.
作者介绍了一种辐射检测方法，该方法依赖于探测器材料中次级带电粒子形成的高能电流（HEC），它会在外部读出电路中感应出传导电流。入射辐射的直接能量转换为信号形成提供了动力，无需外部偏置电压或放大。作者所考虑的探测器是一种薄膜多层器件，由交替的不同导电层和绝缘层组成。HEC探测器的最佳设计包括微观或纳米结构。
通过理论和计算发展来阐述HEC探测器的显著特性并证明其可行性。在这项工作中，作者研究了厚度从100纳米到300微米的铜与铝、金与铝的单夹层和周期性层，它们由尺寸相似的介电间隙隔开，并暴露于120 kVp的X射线束（铝的半值厚度为4.1毫米）下。使用辐射传输计算确定能量沉积特性和高能电流。
作者发现，在双层配置中，信号处于可测量范围内。对于多层结构中定义的总探测器厚度，信号随着高Z导电层厚度的减小而急剧增加。本文重点关注计算结果，而另一篇配套论文报告了实验结果。
该器件的显著优点是无需外部电源和放大即可产生可测量的信号；它可以制成任何尺寸和几何形状，包括非常薄（亚毫米到亚微米）的柔性曲线形式，并且成本低廉。潜在应用包括医学剂量测定（体内和体外）、辐射防护以及其他需要上述一种或多种特性的场景。
