Fluke Biomedical 943-35 - Manual (Page 9)

Introduction
Functional Description
1
1-5
The Nal crystal is optically coupled to the photomultiplier tube so that light pulses occurring in the crystal
are visible to the photocathode of the photomultiplier tube. The electrons in the photocathode become
excited by the light, resulting in emission of electrons from the surface of the photocathode. The voltage
potential differences in the dynode network start a cascade of electrons, which, upon reaching the anode,
become a pulse of current. The anode collects this pulse and makes it available to the preamplifier.
Preamplifier
The preamplifier provides amplification of the output from the photomultiplier tube and cable driving
capabilities. Operational amplifier Z1 is configured to provide a voltage gain of 6 for the output of the
photomultiplier tube. Transistors Q1 and Q2 provide cable-driving capability for up to 1500 feet of cable.
Using the detector as typically set up by the Fluke Biomedical calibration process, the output of the
photomultiplier tube produces a negative pulse from approximately 200 millivolts to 6 Volts, corresponding
to an 80 keV to 2 MeV photon energy range. This signal is amplified to a 12 Volt negative pulse at the
emitter of Q2, which is coupled to the cable by capacitor C6.
The combination of impedance matching resistor R11 and the termination resistor in the readout (ideally
50 ohms) results in a received pulse with a pulse height proportional to incident energy.
1.6 Receiving Inspection
Upon receipt of the package:
1. Inspect the cartons (s) and contents for damage. If damage is evident, file a claim with the carrier
and notify Fluke Biomedical, Radiation Management Services at 440.248.9300.
2. Carefully remove the contents from the packing material. The crystal end is fragile.
3. Verify that all items listed on the packing list have been received and are in good order.
If any of the listed items are missing or damaged,
notify Fluke Biomedical.
1.7 Storage
Instruments storage must comply with Level B storage requirements as outlined in ANSI N45.2.2 (1972)
Section 6.1.2(.2). The storage area shall comply with ANSI N45.2.2 (1972) Section 6.2 Storage Area,
Paragraphs 6.2.1 through 6.2.5. Housekeeping shall conform to ANSI N45.2.3 (1972).
Level B components shall be stored within a fire resistant, tear resistant, weather tight enclosure, in a
well-ventilated building or equivalent.
Instrument storage must comply with the following:
1. Inspection and examination of items in storage must be in accordance with ANSI N45.2.2 (1972)
Section 6.4.1.
2. Requirements for proper storage must be documented and written procedures or instructions must
be established.
3. In the event of fire, post-fire evaluation must be in accordance with ANSI N45.2.2 (1972), Section
6.4.3.
4. Removal of items from storage must be in accordance with ANSI N45.2.2 (1972), Sections 6.5 and
6.6.
NOTE