660
Dual 5-kV Detector Bias Supply
•Two independent bias supplies in a single
module 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 660 Dual 5-kV Detector Bias
upply contains two independently adjustable
S
power supplies for furnishing the bias voltage to
germanium detectors, silicon detectors, or
ionization chambers. It can be used with any
etector that draws less than 100 µA of current,
d
and whose gain is insensitive to the applied
voltage. The output voltages are continuously
adjustable from zero to full scale with calibrated
and locking 5-turn dials. Each supply provides two
outputs controlled by the same dial: a 0 to 5 kV
output, and a 0 to 500 V output. Two 10-segment
bar-graph indicators verify that the selected
voltages are being supplied at the outputs.
Security against accidentally changing the output
polarity to the wrong state is ensured by two
features. The selected output polarity for each
supply 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 660 includes a remote shutdown
feature to protect the preamplifier FET against
damage when a cooled germanium or Si(Li)
detector warms up. Each supply includes a BIAS
SHUTDOWN input that is compatible with the
standard warmup sensor output on ORTEC
preamplifiers. When the preamplifier signals a
warmup condition, the Model 660 shuts off the
bias voltage to that detector, and turns on a
SHUTDOWN 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 push button. 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 shut-down 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 660 can be moved to the TTL position to
make the bias shutdown input com-patible 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 660 is shipped from the factory with
oth supplies set to the ORTEC mode.
b
The high voltage outputs are protected against
overload. When the bias supply senses an
xcessive output current demand, it turns on the
e
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.
Specifications
Channels A and B are independent supplies. The specifications
listed below apply to either channel.
PERFORMANCE
BIAS VOLTAGE RANGES 0–5 kV, or 0–500 V, on
separate outputs, with each output controlled by a
common, 5-turn, direct-reading, precision potentiometer
located on the front panel.
BIAS VOLTAGE POLARITY Positive or negative.
Internally selectable. Polarity indicated by front-panel
LEDs whenever bin power is on.
RATED OUTPUT CURRENT 0–100 µA.
OUTPUT LINEARITY Within ±3% of dial setting from
10% to 100% of full range.
TEMPERATURE SENSITIVITY OF OUTPUT VOLTAGE
<±0.08%/°C through the 10 to 50°C operating range.
VOLTAGE STABILITY <±0.1%/h variation in output
voltage with constant temperature, constant load, and
constant input voltages from the bin supply.
NOISE AND RIPPLE <10 mV peak-to-peak from 5 Hz
to 50 MHz.
OUTPUT VOLTAGE RISE TIME Nominally 500 ms.
INDICATORS
0 kV–5 kV Front-panel, 10-segment, bar-graph display
indicates actual output voltage at the 0–5 kV output.
Each segment corresponds to a 0.5-kV increment in
output voltage, starting with 0.5 kV to turn on the first
segment, and ending with 5 kV to turn on the tenth
segment.
POS Front-panel LED is lit when the bin power is on, if
the positive output polarity has been selected.
NEG Front-panel LED is lit when the bin power is on, if
the negative output polarity has been selected.
ON Front-panel LED indicates when the output bias
voltage is turned on. This LED turns off when the HV
ON/OFF switch is turned off, the bin power is off, or the
shutdown mode has been activated.
OVERLOAD Front-panel LED turns on when the bias
supply senses an excessive output current demanded by
the external load. Under overload, the output voltage is
reduced automatically until the output current is within
660
Dual 5-kV Detector Bias Supply
tolerable limits. Recovery from overload is automatic
when the overload is eliminated.
SHUTDOWN Front-panel LED turns on when the
shutdown mode has been activated to turn off the output
voltage. The shutdown mode is activated by the
appropriate signal level on the rear-panel, BIAS
SHUTDOWN input, or whenever the bin power is turned
off and on.
CONTROLS
0–5 kV Front-panel, 5-turn, direct-reading, locking
potentiometer with 500 dial divisions adjusts the output
voltages simultaneously for the 0–500 V and the 0–5 kV
outputs.
HV ON/OFF Front-panel toggle switch turns the
0–500 V and the 0–5 kV outputs on or off. For added
safety, the RESET push button must be pressed after
turning the HV ON/OFF switch to the ON position, in
order to turn on the output voltage. The output voltage
will not turn on if a shutdown condition is present at the
BIAS SHUTDOWN input.
RESET Pressing this front-panel push-button switch
enables the high voltage to turn on after the bin power
has been turned on, the HV ON/OFF switch has been
turned on, or the supply has been disabled by the BIAS
SHUTDOWN input. If a shutdown condition is still
present at the BIAS SHUTDOWN input, the RESET
button will be ineffective.
ORTEC/TTL/BYPASS Internal printed wiring board
jumper selects the operating mode of the BIAS
SHUTDOWN input for compatibility with the warmup
sensor in the associated Ge detector. The ORTEC
position is used for ORTEC detectors. The TTL position
is for detectors employing TTL levels. The BYPASS
position disables the BIAS SHUTDOWN input, but does
not alter the function of the RESET button. The Model
660 is shipped with this jumper in the ORTEC mode.
OUTPUT VOLTAGE POLARITY The output polarity is
changed between positive and negative by changing the
position of a daughter board in the module.
INPUTS
BIAS SHUTDOWN INPUT Rear-panel BNC connector
accepts signals from warmup sensors in cooled
germanium detectors. When a warmup is signalled, this
input turns off the detector bias voltage in order to
protect the preamplifier FET input. The
ORTEC/TTL/BYPASS jumper selects the operating mode
of the BIAS SHUTDOWN input for compatibility with the
warmup sensor in the associated Ge detector.
ORTEC Mode The input is compatible with the
warmup sensor output on ORTEC germanium
detectors. For added safety, an open or shorted
coaxial cable on the BIAS SHUTDOWN input will
also cause the supply to shut down.
TTL Mode A source supplying >+2 V or an open
circuit will allow the Model 660 to produce the full
output voltage. A source supplying <+0.8 V and
capable of sinking 700 µA will shut down the high
voltage output.
BYPASS MODE The BIAS SHUTDOWN input is
rendered inactive, and cannot trigger a bias
shutdown.
OUTPUTS
0–5 kV Rear-panel SHV connector furnishes the
adjusted output voltage in the 0 to 5-kV range through
an output impedance of approximately 2 M W. A voltage
foldback circuit protects the output against demands for
excessive output current. Recovery from overload is
automatic when the overload is eliminated.
0–500 V Rear-panel SHV connector furnishes the
adjusted output voltage in the 0 to 500-V range through
an output impedance of approximately 700 kW. A voltage
foldback circuit protects the output against demands for
excessive output current. Recovery from overload is
automatic when the overload is eliminated.
ELECTRICAL AND MECHANICAL
POWER REQUIREMENTS The Model 660 derives its
power from a NIM bin power supply. Required DC
voltages and currents are: +24 V at 135 mA, +12 V at
150 mA, –12 V at 100 mA, –24 V at 75 mA.
WEIGHT
Net 0.90 kg (2.0 lb).
Shipping 1.4 kg (3.0 lb).
DIMENSIONS Standard single-width NIM module, 3.43
X 22.13 cm (1.35 X 8.714 in.) front panel per DOE/ER0457T.
Ordering Information
To order, specify:
Model Description
660 5-kV Detector Bias Supply
OPTIONAL CABLE ACCESSORIES
Model Description
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
Specifications subject to change
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