HV Board Components

Here is information on the components we plan to use on the HV board.

• Fuses
  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 Wickmann, 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, Tusonics and MuRata. We are evaluating both and will choose the least expensive which meets our requirements.

• Diodes
  CAEN has suggested the Philips BYX90 [PDF]. 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 [PDF].

• Termination Resistor
  This resistor must match the chamber impedance of about 370 ohms. Tolerance should be 1%. No other special requirements.