Security System for Electrically-Cooled
HPGe Detectors
• Microprocessor controlled
• Protection against possible failure due to
power outage
• Wide selection of restarting time intervals
• LED indicators show system status at a glance
• Battery backup
When germanium detectors are cooled with an electromechanical
cooler, such as the X-COOLER III from ORTEC, there is a small
possibility of an ac power failure causing detector damage. The
supposed mechanism is that following the power failure, the system
starts warming toward room temperature, and during the warmup,
residual gases are released by the molecular sieve. If, before the
system is completely warmed up, the ac power is restored, some of
the gas is gettered by the detector element, which is then the coldest
object in the vacuum assembly. The condensed gases may short
circuit the reverse-biased detector junction and thereby cause voltage
breakdown. For this reason, many users of electromechanical coolers
prefer the detector to warm completely to room temperature after a
power failure. CryoSecure ensures that this occurs, thus avoiding
possible detector failure.
The CryoSecure Compressor Power Controller allows the operator to
control the following time intervals:
• The “holding time” (4 selectable values) after an ac failure before
allowing the Controller to go in the warming mode
• The “warmup time” (4 selectable values), which is the time the
compressor is unpowered as the detector warms to room
• The “cooling time with bias off” (16 selectable values), the Controller
waits after restarting the compressor, before allowing reapplication
of the detector bias voltage.
Once the desired time intervals are set, CryoSecure operates
automatically under microprocessor control. Designed for worldwide
use, CryoSecure operates with input from 100 V ac to 240 V ac, 47 to
63 Hz.
A rear-panel connector block incorporates a fuse holder and the input
power connector. An international standard IEC power connector
permits the use of power cords and plugs that meet local electrical
standards. Output to the compressor, controlled by a solid-state relay,
is provided via a mating rear-panel connector. The internal
microprocessor-controlled circuit detects ac failure, measures its
duration, and determines an appropriate response based on user
settings. During the power failure, an internal battery supplies power
to CryoSecure for continued operation (nominally 24 hours). Frontpanel LED indicators allow monitoring of the controller status:
• AC Power AC on, the battery is being charged, the cooler is
operating normally.
• Holding System is maintained on hold after a power failure.
• Warming System is in a warmup mode.
• Bias OFF Detector bias voltage is shut down.
• Mains Fail AC power has been interrupted.
A front-panel, two-position rocker switch turns the power on or off and
a push-button Initialize switch allows the user to select the sequence
of operation.
Security System for Electrically-Cooled
HPGe Detectors
INPUT AC VOLTAGE The CryoSecure can accommodate input voltages of 100 V
ac to 240 V ac at 47 to 63 Hz.
INPUT CURRENT Typically 7.5 A rms when connected to a 600-watt compressor.
CIRCUIT PROTECTION The input ac power line is protected with a 10-A fuse
incorporated into the AC POWER input connector.
AC POWER Rear-panel, international standard IEC power connector, type CEE22, accepts power cables wired according to local electrical standards. A power
cable is shipped with the CryoSecure.
BIAS SHUTDOWN Rear-panel BNC connector accepts Bias Shutdown signal
from detector. During normal operation, this signal is passed through a relay
contact to allow bias voltage to be applied to the detector. During a Holding State,
Warming State, or Cooling State, the Bias Shutdown signal is interrupted
preventing bias from being applied to the detector.
COMPRESSOR Rear-panel, type NEMA 5-15R AC, provides ac mains voltage to
the compressor. A solid-state switch in series controls on/off operation of the
BIAS SHUTDOWN Rear-panel BNC connector provides Bias Shutdown signal to
the detector.
AC POWER Front-panel LED indicates presence of ac mains voltage.
BIAS OFF Front-panel LED indicates the bias supply has been shut down.
WARMING Front-panel LED indicates CryoSecure is in the warming phase.
HOLDING Front-panel LED indicates CryoSecure is in the holding phase.
MAINS FAIL Front-panel LED indicates ac mains has failed. CryoSecure is
operating from the internal battery.
Net 2.6 kg (5.8 lb).
Shipping 3.2 kg (7.0 lb).
DIMENSIONS 21.5 cm W x 26 cm D x 10.2 cm H.
Aluminum enclosure.(8.4 x 10.2 x 4.0 inches)
Ordering Information
To order, specify:
Compressor Power Controller
POWER Front-panel rocker switch turns power on or off.
INITIALIZE Front-panel push-button switch begins system operation, and allows
the customer to manually cycle through the operating sequences.
HOLD TIME Internal printed wiring board (PWB)-mounted rotary switches (qty. 2)
allow user to set the amount of time the CryoSecure waits after a mains power
failure, before entering the Warming State.
WARMING TIME Internal PWB-mounted rotary switches (qty. 2) allow the user to
set the amount of time the CryoSecure waits after a mains power failure before
restarting the compressor.
BIAS OFF Internal PWB-mounted rotary switch allows the user to set the amount
of time the CryoSecure waits after restarting the compressor, before allowing the
detector bias voltage to be applied.
DEEP DISCHARGE PROTECTION In the event of a long-term power failure, or if
the ac mains are turned off for an extended period of time, an internal relay will
disconnect the internal circuity from the internal backup battery before the battery
discharges. When ac power is restored, the system will resume normal operation
and the battery will be recharged.
Specifications subject to change
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