659
5-kV Detector Bias Supply
- Bias voltage for germanium and silicon detectors
- 0–5 kV or 0–500 V at 0–100 µA
- Remote shutdown feature compatible with ORTEC and TTL outputs from warmup
sensors on germanium detectors
- Reset safety feature on remote shutdown minimizes risk of preamplifier
FET damage
- Selected output polarity indicated before bias voltage is turned on
- Automatic overload protection and overload indicator
The ORTEC Model 659 5-kV Detector Bias Supply
furnishes bias voltage for germanium detectors, silicon detectors, or ionization chambers.
It can be used with any detector that draws less than 100 µA of current, and whose gain
is insensitive to the applied voltage. The output voltage is continuously adjustable from
zero to full scale with a calibrated and locking 5-turn dial. Separate outputs are
provided for the 0–5 kV and the 0–500 V ranges. A 10-segment bar-graph indicator
verifies that the selected voltage is being supplied at the output.
Security against accidentally changing the
output polarity to the wrong state is ensured by two features. The selected output
polarity is indicated by front-panel LEDs whenever the NIM bin power is turned on. Thus,
the correct polarity can be verified before the HV ON/OFF switch is used to turn on the
bias voltage to the detector. In addition, the side panel must be removed in order to
alter the output polarity. This discourages unintentional changes.
The Model 659 includes a remote shutdown
feature to protect the preamplifier FET against damage when a cooled germanium or Si(Li)
detector warms up. A BIAS SHUTDOWN input that is compatible with the standard warmup
sensor output on ORTEC preamplifiers is provided. When the preamplifier signals a warmup
condition, the Model 659 shuts off the bias voltage and turns on a SHUT-DOWN indicator
light. The bias voltage remains off, independent of the signal from the preamplifier
warmup sensor, until the shutdown mode is manually cancelled by pressing the RESET
pushbutton. This protects the preamplifier FET if the detector is cooling down with the HV
ON/OFF switch accidentally left on. For further protection against operator error in the
ORTEC shutdown mode, the bias shutdown input interprets a disconnected cable or a shorted
cable as a warm detector, and responds by turning off the bias voltage. Some detector
manufacturers provide a TTL logic level output from their detector warmup sensor. A
board-mounted jumper in the Model 659 can be moved to the TTL position to make the bias
shutdown input compatible with detectors supplying a TTL output. It is also possible to
disable the bias shutdown feature by moving the board jumper to the BYPASS position. The
Model 659 is shipped from the factory in the ORTEC mode.
Both high voltage outputs are protected
against overload. When the bias supply senses an excessive output current demand, it turns
on the overload light and reduces the output voltage until the output current is within
tolerable limits. Recovery from overload is automatic when the excessive current demand is
eliminated.ORDERING INFORMATION
| Model |
|
Description |
| 659 |
|
5-kV Detector Bias Supply |
| C-24-12 |
|
RG-62A/U 93-W Cable with two BNC
male plugs; 12-ft length |
| C-36-12 |
|
RG-59A/U 75-W Cable with two SHV female plugs; 12-ft length |
|
