ORTEC 659 User Manual
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
upply furnishes bias voltage for germanium
S
detectors, silicon detectors, or ionization
chambers. It can be used with any detector that
draws less than 100 µA of current, and whose
ain is insensitive to the applied voltage. The
g
output voltage is continuously adjustable from
zero to full scale with a calibrated and locking
5-turn dial. Separate outputs are provided for the
–5 kV and the 0–500 V ranges. A 10-segment
0
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 boardmounted 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
verload light and reduces the output voltage
o
until the output current is within tolerable limits.
Recovery from overload is automatic when the
excessive current demand is eliminated.
Specifications
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 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 a tolerable limit. 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.
659
5-kV Detector Bias Supply
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 659 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 signaled, 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 659 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 MW. 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 659 derives its
power from a NIM bin power supply. Required DC
voltages and currents are +24 V, 80 mA; +12 V,
80 mA; –24 V, 35 mA; and –12 V, 65 mA.
WEIGHT
Net 0.68 kg (1.5 lb).
Shipping 1.1 kg (2.5 lb).
DIMENSIONS Standard single-width NIM module,
3.43 X 22.13 cm (1.35 x 8.714 in.) front panel per
DOE/ER-0457T.
Ordering Information
To order, specify:
Model Description
659 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
102120
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