單位面積上的本底平均計(jì)數(shù)率（Nb.min-1cm-2）α≤0.005/β≤0.15；  效率比ηr，α≥80%/β≥50%；    

長期穩(wěn)定性：                                                                                                  

1.效率穩(wěn)定性α＜5%/β＜10%；                                                                           

2.本底穩(wěn)定性α：Nb±3σ/β：Nb±3σ；α  β交叉干擾：α對β＜3%/β對α＜0.5%。