| 摘要 |
PURPOSE:To raise space resolution and uniformity, by changing a current flowing to a weighing resistance of a position calculating circuit for calculating a scintillation position. CONSTITUTION:Each PMT output passes through a pre-amplifier 21 and a voltage-current converting circuit 22, and is sent to weighing resistances RXi, RYi and RZi of position calculating circuits 5, 6 and an energy calculating circuit 7. Voltage being proportional to that which is obtained by adding output voltage from the pre-amplifier and bias voltage, by an adding amplifier consisting of resistances 24-26 and an OP amplifier 27 is applied as control voltage VGS to a voltage control resistor (VCR)23, and the smaller the output voltage of the pre-amplifier 21 is, the smaller a resistance value RVCR of the VCR23 becomes. The smaller the RVCR is, the smaller a current IS to the position calculating circuits 5, 6, etc. becomes, therefore, the smaller the PMT output is, the harder it becomes that a current flows to the weighing resistance of the position calculating circuit, contribution to calculation of a position is reduced, and the resolution can be raised. |
