Several voltages are needed for operating the detector (exact values are given in each detector data sheet), for example:
- Ring 1 = approx. -20 V
- Ring X = approx. -130 V
- Back = approx. -65 V
The detector voltages should be filtered using the following combinations of resistors and capacitors providing low pass filters:
- Ring 1: RR1 = 15 kΩ, CR1 = 220 nF
- Ring X: RRX = 500 kΩ, CRX = 47 nF/250 V
- Back: RBack = 1 MΩ, CBack = 47 nF/250 V
Before switching on the system, the output-signal of the preamplifier and the shaped signal should be connected to an oscilloscope. The preamplifier operating voltage must be switched on first.
The detector voltages should be switched on in the following order:
R1 – RX – Back
The voltages to be applied must be set according to the detector datasheet. Typical currents flowing are several μA through Ring 1 and Ring X (voltage divider) and approx. 1 nA for the back contact if the back voltage is applied. R1 and RX currents should be equal!
After switching on the detector voltages the signal of the preamplifier should show a ramp. The ramp period depends on the chip temperature. At -35 °C the ramp period should be in the range of several microseconds.