Maintenance And Service; Decontamination; Chamber Decontamination; Ultra Detector Decontamination - Ametek ORTEC Alpha Duo Hardware User's Manual

4. Maintenance and Service

4.1

DECONTAMINATION

The normal background count above 3 MeV for an Alpha chamber should be <24 counts per day for
the 300 mm 2 and 450 mm
by contamination of the chamber and/or the detector by residual deposits of alpha-emitting materials.
Decontamination of the chamber and of the detector (if ULTRA or Ruggedized) is indicated.
CAUTION Non-ULTRA or non-Ruggedized surface barrier detectors cannot be subjected to
cleaning procedures; consult the instruction manual for the detector to determine how
to clean it.
4.1.1

Chamber Decontamination

To decontaminate an Alpha chamber in place:
1) Turn off bias to the detector and vent the chamber.
2) Remove the detector from the chamber by rotating it counterclockwise.
CAUTION To avoid damaging the detector, make sure its protective cover (supplied) is in place
before the detector is removed. Wear plastic gloves to keep from contaminating your
hands or the chamber.
3) Pour the cleaning agent into a clean beaker. Methanol, or water with a methanol rinse, can be
used as the cleaning agent.
4) Dip a cotton swab or a cotton-covered stick into the agent and gently wipe the internal surfaces
of the chamber to remove any contamination. Avoid contaminating vacuum or vacuum gauge
ports. Plug holes if necessary.
5) When contamination from the surface is visible on the cotton swab, discard it and use a clean
one to avoid returning the contaminant to other areas of the chamber.
6) When the chamber is clean, blow it dry with clean nitrogen gas.
4.1.2

ULTRA Detector Decontamination

The front surface of an ULTRA detector can be cleaned with a cotton swab moistened with acetone.
Gently rub the detector surface with the swab. Repeat with fresh acetone and a fresh swab. Blow dry
with dry nitrogen gas. Before applying bias, leave the detector under vacuum for 30 minutes to remove
all surface moisture.
4.1.3

Ruggedized Detector Decontamination

To decontaminate the front (aluminum) surface of a Ruggedized detector:
1) Turn off bias to the detector, vent the Alpha chamber, power off its enclosure, and disconnect
the enclosure from ac mains power. Optionally, users can slide the Alpha chamber out of its
enclosure as shown in Figure 14 and Figure 15 of Appendix B.
2 ULTRA detectors. If an increase of background is noted, this may be caused
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