【摘要】 本计数器采用了对两只光电倍增管输出的信号先进行幅度分析再送入符合线路的电子学逻辑,减少了串光本底;采用了10cm厚的铅屏蔽,并用一块环形NaI（TI）晶体作反符合屏蔽,大大降低了宇宙射线和外部辐射对本底的贡献;设计了收光效率高,对本底贡献小的样品室及其附件,可以测量2—100ml范围内不同体积的样品;在测量过程中,能自动打印出计数结果。 DYS-1型计数器特别适合于³H和¹⁴C的低水平测量。对20ml的苯样品,³H效率为56％时,本底为2.17min^-1;用100ml的样品瓶测水时,（EV）²/B能大于,100000,能直接测量10TU的水样品;对5ml苯样品,¹⁴C的优值超过10000。更多还原

【Abstract】 A low-level liquid scintillation counter called DYS-1 has been built in our laboratory. A major difference between this and commercial liquid scintillation counter is that different pulse analysis and coincidence technique are introduced. In this instrument, at first, the amplitude of pulses from two PMTs is analysed by two timing single-channel analysers individually, then coincided within a specified time interval, With this, "erosstalk" background can be decreased efficiently. A massive 10cm thick lead shield and an annular NaI （T1）crystal anti-coincidence guard detector are used to reduce the background produced by the external radiation and cosmic rays. Three sizes of sample chambers and some accessories were designed for measurement of 2,5,10,20,50 and 100ml samples under the optimum geometry conditon. The counter can print raw-data automatically during the period of measurement.The counter was specifically designed for the measurement of low specific activity of tritium and carbon-14. For 20ml benzene sample, the efficiency of tritium is 56％ with the background 2.17epm, （EV）²/B of ³H₂O measurement for 100ml sample is greater than 100000, the activity of ³H₂O under 10 TU can be measured directly. For 5mlbenzene sample, figure of merit, E²/B for ¹⁴C measurement is superior to 10,000. Of course,the counter can be used to detect other radioisotopes in low specific activity.Data of more than 60 carbon-14 samples and more than 100 ³H₂O samples have been taken by this instrument.更多还原