3
2.5. ELECTRICAL AND MECHANICAL
POWER REQUIRED Furnished from any NIM
bin and power supply through any ORTEC main
amplifier or from an ORTEC 114 Power Supply;
built-in captive cable is compatible with either
source.
+24 V, 30 mA; -24 V, 1 0 mA;
+12 V, 15 mA; -12 V, 15 mA.
DIMENSIONS 1.75 X 5.2 X 4 in., plus 10-ft cable.
(4.45 X 13.2 X 10 cm, plus 3-m cable.)
3. INSTALLATION
3.1. CONNECTION TO DETECTOR
3.2. ENERGY OUTPUT CONNECTION TO
A direct connection with the shortest possible
length of shielded cable should be made between
the detector and the Input connector on the
preamplifier. For best results, the length of this
cable must be as short as possible to minimize
the preamplifier noise (due to the capacitive
loading of the cable) and to maintain the stability
of the preamplifier. The complex impedance
presented to the preamplifier input that is due to
transmission line effects acting on the detector
system impedance can disrupt the stability of the
whole system. Due to vagaries in the detector
system, a definite maximum length cannot be
specified but is typically 60 inches (150 cm).
Type RG-62/U cable is recommended for the
detector to preamplifier connection; this is 72
cable with a capacity of 21 pF/ft.
When operating at bias levels greater than 3 kV,
special care must be taken to minimize spiking
due to corona discharge from the type SHV
connectors on the able between the detector and
the preamplifier. Normally, corona problems in
the bias cable between the bias power supply and
the preamplifier are significant due to the filtering
circuit within the preamplifier.
After the input cable has been installed, the
electronic noise performance of the preamplifier
can be predicted by adding the capacity furnished
by the detector to the capacity of the cable. The
cable capacity can be calculated from its length
and its rated capacity per foot.
MAIN SHAPING AMPLIFIER
The E output of the preamplifier can be used to
drive a long 93
Iine to a shaping main amplifier
and is designed to be directly compatible with
ORTEC main amplifiers. It can be used with any
shaping main amplifier if a power supply is also
used to furnish the preamplifier power
requirements that are available on all ORTEC
main amplifiers.
3.3. TIMING OUTPUT CONNECTION TO
TIMING MODULES
The T output of the preamplifier can be used to
drive a long, terminated 50
cable to a timing
module. Typical timing modules include
amplifiers, fast discriminators, or a time-to-
amplitude converters. When the T output is not
being used, it should be terminated in 50
.
3.4. INPUT OPERATING POWER
Power for the 142AH Preamplifier is supplied
through the captive power cord and 9-pin
Amphenol connector. This connector can be
attached to the mating power connector on any
ORTEC main amplifier or 114 Preamplifier Power
Supply. The preamplifier's power requirements
are added to the operating power, requirements of
the amplifier or power supply to which it is
connected.
