HV Board Components
E. Hazen - 9 Mar 1998
Here is information on the components we plan to use on the HV board.
Paul Mockett has shown that standard 5mmx20mm fuses with a
250V rating can work reliably at much higher voltages (up to 7kV
in tests). He suggests
type 19194 (ceramic) [PDF] or
type 19193 (glass) [PDF].
We will investigate other manufacturers, but will likely use a
5x20mm part for the prototype.
- HV Capacitors will be through-hole disc type, with the
following basic specifications:
|Capacitance || 0.47nF
|Tolerance || 10% over full voltage and temp. range
|Max Working Voltage || 5kV
|Reliability || << 0.1% failures in 10^6 units in 10 LHC-years
Two manufacturers have been suggested,
We are evaluating both and will choose the least expensive which
meets our requirements.
CAEN has suggested the Philips BYX90
At this point it's specs seem reasonable, and we will use this
part for our prototype layout.
- Current-Limiting Resistor
The resistor must be rated to operate at 5kV. Tolerance
should be 5%.
The reistor value is somewhat under discussion. Conventional
wisdom suggests a 1M resistor. However for reverse bias operation
to "anneal" chamber ageing, larger currents may be required.
For operation at 1mA with a shorted wire, a 1W rating is required.
CAEN has suggested the Philips VR68 series
- Termination Resistor
This resistor must match the chamber impedance of about 370
ohms. Tolerance should be 1%. No other special requirements.