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32-channel photomultiplier hv system/ lacory
32-Channel Photomultiplier HV System
The LeCroy Model HV4032 is the first complete photomultiplier high voltage system. It includes 32 microprocessor-controlled high voltage supplies rated at -3 kV, 2.0 mA. Each supply may be set and read out either remotely or locally with 1 V precision. Remote operation of up to 63 units (2016 channels) is possible with either a standard TTY or an HV-to-CAMAC interface, LeCroy Model 2132.
Remote operation affords both operational and economic ad- vantages. By mounting the high voltage chassis near the appa- ratus, long cable runs are eliminated along with the expense and manpower required to install them. Having computer con- trol finally closes the loop, allowing the continuous gain control required of large systems.
The HV4032 replaces the conventional high voltage supply, the space-consuming distribution system, the monitor ADC system, and often several kilometers of high voltage cable. It also allows ease of setup under local control, remote operation without a computer, and on-line computer control. It has suffi- cient local intelligence to guard against a possible catastrophe caused by power failures, computer errors, software bugs, or even operator errors.
The HV4032 uses an F8 microprocessor to perform all functions. A DMA of the 32 voltage set-points continuously updates the high voltage supplies via a 12 bit multiplexed DAC. A separate divider and multiplexer along with a 12-bit ADC are used to read the output voltages. Turn-on, turn-off, and voltage changes are done under program control in order to achieve a safe 1 kv/sec rate.
The voltage of all channels may be commonly set and any channel may be read out, set, zeroed, or restored under remote control (CAMAC or TTY) or under local control (front panel). Operation with the front-panel control employs a two-digit LED channel display and a four-digit voltage display. Selecting a channel automatically causes the voltage to be displayed.
A single command can return 32 voltage settings to a TTY or to the 32-word buffer memory of the Model 2132. In the CAMAC mode, a low-priority LAM condition is set after the 32-word transfer is complete. A jack on the front panel of the 2132 allows this LAM to be masked off. This allows measurements to be made during a beam spill and read out between spills. The high-priority LAM, generated by error-checking faults, cannot be masked off.
Numerous safeguards and error-checking subroutines are in- cluded in the HV4032 microprogram. The ADC readings are repetitively compared with the 32 voltage set-points stored in memory. A front-panel vernier sets an output voltage limit. An auto-rechargeable battery guards against memory data loss due to power failures of up to 24 hours. In addition, a bit pat- tern loaded into memory at power-down serves to test the bat- tery backup system.
Model HV4032 32-Channel Photomultiplier HV System
32: SHV rear-panel connectors.
Adjustable from near 0 to - 3 kV.
0.01%/OC of ambient air (+10'C to +40'C).
Protected from damage against continuous short circuit conditions.
Internally programmed at a 1 kv/sec rate.
2 decimal digits; indicates selected channel.
4 decimal digits, indicates the actual output voltage of the selected channel (except when the voltage is being changed; in which case it indicates the internally stored set point).
3-position momentary toggle switch; enables voltage or address to be changed by Increase/Decrease switch. Selection of channel "32" permits all channels (0-31) to be changed in common.
3-position momentary toggle switch; increases (decreases) channel number if ad- dress control is selected; increases (decreases) voltage of selected channel if voltage control is selected. (Note that the voltage and all channels may be changed simultaneously by the selection of channel "32".)
3-position momentary toggle switch; sets addressed channel to approximately zero, or restores it to its original value. An OFF channel may have an open circuit voltage of up to -150 volts, but will supply less than 30 uA shorted, therefore presenting no hazard to personnel.
Momentary front-panel pushbutton reduces all output voltages to zero or restores them to original setting. Alternately, this function may be performed by remote command from TTY or CAMAC.
Selects local manual control or remote control (TTY or LeCroy Model 2132 CAMAC Interface).
Toggle switch controls AC main power. Rechargeable battery supplies memory power for 24 hours when main power is off or lost, recharges when AC power is on.
Banana jacks. Analog output of selected channel, 1 volt/kv.
BNC connector. When clamped to ground, all output voltages are decreased to less than -100 V.
High intensity LED. Indicates HV is on.
Two multipin connectors, with front-panel retainer, provides "daisy-chain" capa- bility. Five pairs interconnect the modules, two pairs are 20 mA current loops (trans- mit and receive), two pairs are used for bus control, and one pair selects the BAUD rate. (1 10 or 300 BAUD rate to TTY, 2400 to CAMAC).
19" rack-mount chassis, 17" x 21 & 1/8" x 6 & 5/8". Side-panel slides facilitate internal access.
110 V, 60 Hz or 220 V, 50 Hz by rear panel switch selection.
