The specifications cannot be finalized until the choice of PMT is made. The Hamamatsu R7081 family of tube is the tentative choice. Albrecht Karle (U of Wisconsin) tells me they will buy several standard 10 dynode tubes, several optimized 10 dynode tubes and several 12 dynode prototype tubes for evaluation. The 12 dynode tube does not yet have a pin-out defined.
Several options are possible.
a. One could delay design until the PMT is chosen, then design the power supply for that tube.
b. One could design separate power supplys for both a 10 dynode tube and a 12 dynode tube.
c. One could design a power supply which could be 'strapped' for either the 10 or 12 dynode tube.
The pin-out of the R7081 tube is defined, as is the divider chain. Information can be found at http://usa.hamamatsu.com/cmp-pdfs/et/pmt-highenergy.pdf on page 20 and page 41. Design of a power supply for a 10 dynode tube using the standard divider chain could proceed immediately, however there is some risk. If the optimized 10 dynode tube is chosen the voltage set may not match the one published for the standard R7081.
|High temperature PCB material shall be used to improved solderability to Kovar PMT base pins. The laminate should not break down when heated to typical soldering temperatures for thirty seconds minimum. (This may or may not be long enough)|
|Control and readout via synchronous serial port. eg. SPI/QSPI, or I²C|
|The power supply for the remaining dynodes and anode shall be stacked on top of the first dynode voltage.|
|ADC shall be at least 10 bits, two channels (minimum, current monitoring is optional)|
|DAC shall be at least 10 bits
|Power switching circuits, DAC, and ADC shall utilize GND_Power as the power return and reference.|
|Voltage multipliers, Cathode, dynode and anode, and output circuit shall utilize GND_Signal as a common signal|
|Capacitance between GND_Power to GND_Signal shall be 30 pF or less (possibly negotiable)|
|One 0805 footprint for an optional high value resistor shall straddle the divide between Gnd_Power and Gnd_Signal|
|Design for typical operation at
|Anode signal will be transformer coupled using a transmission line transformer made with RG-178B/U teflon coax. The center conductor shall be in the anode circuit, and the shield in the output circuit. The off-board output connection shall be made through 100 ohm coax cable soldered directly to the power supply board.|
|Maximum power supply ripple observed at the output of the secondary of the anode coupling transformer shall be 125 uV when the output is terminated with a 100 ohm resistor.|
|Low power parts will be used wherever possible.|
|Total power consumption shall be 100 mW or less at full output voltage.|
|The failure rate for the PMT power supply in continuous operation for one year should be less than 0.1%. Power cycling and temperature cycling may be necessary to weed out infant failures.|
Other specifications may be added to this list.
Suggestions for additional specifications are welcome. Send me