Compact back-to-back lithium glass detector for online tritium production rate measurement
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摘要: 为了实现强伽马场环境下的造氚率在线测量，研制了小型“背靠背”6Li/7Li玻璃探测器。每块锂玻璃闪烁体的尺寸为3.0 mm×3.0 mm×0.4 mm，闪烁体之间及侧面采用0.5 mm二氧化钛作为反射层，整体尺寸为4.0 mm×4.0 mm×1.3 mm。7Li玻璃探测器测量伽马产生的信号作为6Li玻璃探测器的伽马本底扣除。通过对标准60Co源的伽马射线脉冲幅度谱测量，验证了两个闪烁体对伽马场响应的一致性；在反应堆热中子孔道处和252Cf中子源直照等强伽马环境下测量了脉冲幅度谱，获得的中子伽马信噪比都大于1，表明可以有效扣除伽马本底。验证实验研制的锂玻璃探测器在强伽马场环境下仍能有效甄别伽马，可用于聚变堆和聚变-裂变混合堆实验包层模块内造氚率高精度在线测量。Abstract: To realize online measurement of tritium production rate in a strong gamma field environment, we developed a compact back-to-back 6Li/7Li glass detector. The size of each lithium glass scintillator is 3.0 mm×3.0 mm×0.4 mm. Titanium dioxide with a thickness of 0.5 mm acts as a reflective layer between and on the side of the scintillators. The whole volume of the detector is 4.0 mm×4.0 mm×1.3 mm, which ensures that gamma rays of the two scintillators are almost the same and realizes simultaneous measurement of the gamma rays. The gamma signal produced by the 7Li glass detector is used as the gamma background deduction of the 6Li glass detector. Pulse height spectra of the two lithium glass scintillators irradiated by 60Co gamma are almost the same, which verifies the consistency of gamma signals of the two scintillators. The pulse amplitude spectrum were measured at the thermal neutron channel of the reactor and under the direct irradiation of 252Cf, the signal-to-noise ratio of neutron gamma obtained are both greater than 1, which can effectively deduct the gamma background. The above experiments show that the developed small lithium glass detector can effectively discriminate the gamma rays under strong gamma environment, and is used for on-line measurement of tritium production in the simulated blanket of fusion-fission hybrid reactor.
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图 1 不同能量伽马射线在底面积为3.0 mm×3.0 mm、厚度为0.3 mm、0.4 mm和0.5 mm 锂玻璃中的能量沉积
Figure 1. Energy deposition of different gamma energy in lithium glass with bottom size of 3.0 mm×3.0 mm and thickness of 0.3 mm, 0.4 mm and 0.5 mm
图 2 3.0 mm ×3.0 mm ×0.4 mm锂玻璃闪烁体中子和伽马幅度谱
Figure 2. Comparison of neutron and gamma amplitude spectra in 3.0 mm ×3.0 mm ×0.4 mm lithium glass scintillators
图 5 造氚率测量系统电子学框图
572: spectroscopy amplifier; 927: dual multichannel buffer; MCA: multichannel analyzer
Figure 5. Layout of the front-end electronics for tritium production rate (TPR) measurement
图 6 60Co 伽马在锂玻璃中产生的幅度谱
Figure 6. Pulse height spectra of lithium glass detector irradiated by 60Co gamma rays
图 7 252Cf源中子-伽马混合激发下的脉冲高度谱
Figure 7. Pulse height spectra excited by neutron-gamma mixed field of 252Cf
图 8 电子学框图
Figure 8. Schematic diagram of the electronic circuit
572: spectroscopy amplifier; 927: dual multichannel buffer; 556: high voltage power supply; 113: scintillation preamplifier
图 9 252Cf源直照下的锂玻璃探测器脉冲高度谱
Figure 9. Pulse height spectra of lithium glass detector irradiated directly by 252Cf
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