Testing of the KRI-developed Silicon PIN Radioxenon Detector

Foxe, Michael P.¹  McIntyre, Justin I.¹ 

[1] Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

关键词: ISOMERIC NUCLEI;    XENON 133;    ELECTRON DETECTION;    XENON 131;    XENON 135;    PLASTIC SCINTILLATION DETECTORS;    ENERGY RESOLUTION;    SI SEMICONDUCTOR DETECTORS;    CTBT;    COMPARATIVE EVALUATIONS;    CONCENTRATION RATIO;    NOISE;    CTBTO;    TESTING;    ISOTOPE RATIO;    DESIGN;    MONITORING;    OPERATION;    PEAKS;    SENSITIVITY;    SHIELDING;    VERIFICATION Testing of the KRI-developed Silicon PIN Radioxenon Detector;   

DOI  :  10.2172/1258733
RP-ID  :  PNNL--23995
PID  :  OSTI ID: 1258733
Others  :  Other: NN2003000
Others  :  TRN: US1601521

美国|英语

来源: SciTech Connect

【 摘 要 】

Radioxenon detectors are used for the verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) in a network of detectors throughout the world called the International Monitoring System (IMS). The Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) Provisional Technical Secretariat (PTS) has tasked Pacific Northwest National Laboratory (PNNL) with testing a V.G. Khlopin Radium Institute (KRI) and Lares Ltd-developed Silicon PIN detector for radioxenon detection. PNNL measured radioxenon with the silicon PIN detector and determined its potential compared to current plastic scintillator beta cells. While the PNNL tested Si detector experienced noise issues, a second detector was tested in Russia at Lares Ltd, which did not exhibit the noise issues. Without the noise issues, the Si detector produces much better energy resolution and isomer peak separation than a conventional plastic scintillator cell used in the SAUNA systems in the IMS. Under the assumption of 1 cm³ of Xe in laboratory-like conditions, 24-hr count time (12-hr count time for the SAUNA), with the respective shielding the minimum detectable concentrations for the Si detector tested by Lares Ltd (and a conventional SAUNA system) were calculated to be: ^131mXe ??? 0.12 mBq/m³ (0.12 mBq/m³); ¹³³Xe ??? 0.18 mBq/m³ (0.21 mBq/m³); ^133mXe ??? 0.07 mBq/m³ (0.15 mBq/m³); ¹³⁵Xe ??? 0.45 mBq/m³ (0.67 mBq/m³). Detection limits, which are one of the important factors in choosing the best detection technique for radioxenon in field conditions, are significantly better than for SAUNA-like detection systems for ^131mXe and ^133mXe, but similar for ¹³³Xe and ¹³⁵Xe. Another important factor is the amount of ???memory effect??? or carry over signal from one radioxenon measurement to the subsequent sample. The memory effect is reduced by a factor of 10 in the Si PIN detector compared to the current plastic scintillator cells. There is potential for further reduction with the removal of plastics within the cell, which will need to be explored in future work. A third important parameter in choosing the best detection technique for radioxenon is the resolution of the electron detection. While the resolution is important in determining the minimum detectable concentration, it plays a larger role in source identification when there is a visible signal. The Silicon PIN diodes generated improved resolution over a similar plastic scintillator cell. With the improved resolution, it becomes easier to distinguish the radioxenon isomers (^133mXe and ^131mXe) from the ¹³³Xe beta continuum background. With the beta background from ¹³³Xe ever present with the detection of the isomers, the improved resolution proves vital in calculating the ratios of the three isotopes. With an accurate measurement of the isotopic ratios, the anthropogenic sources of radioxenon (medical isotope production and nuclear reactors) can be more accurately distinguished. Based on the results shown within this report, a Si PIN beta cell shows the potential to aid in the operation and discriminating power of the IMS for the CTBTO. However, there are a number of issues that need attention before a detector of this design would be reliable enough for field operations in the IMS. Issues that need develop include, but are not limited to: studying the robustness of the design in field conditions, eliminating or minimizing the noise and variability of individual Si detector elements, understanding the long-term gain stability of the Si detectors, and reducing the non-Si materials within the cell (i.e. the plastic housing).