ORTEC 142IH Service manual

Model 142IH
Preamplifier
Operating and Service Manual
Printed in U.S.A. ORTEC®Part No. 717590 1202
Manual Revision C

Advanced Measurement Technology, Inc.
a/k/a/ ORTEC®, a subsidiary of AMETEK®, Inc.
WARRANTY
ORTEC* warrants that the items will be delivered free from defects in material or workmanship. ORTEC makes
no other warranties, express or implied, and specifically NO WARRANTY OF MERCHANTABILITY OR
FITNESS FOR A PARTICULAR PURPOSE.
ORTEC’s exclusive liability is limited to repairing or replacing at ORTEC’s option, items found by ORTEC to
be defective in workmanship or materials within one year from the date of delivery. ORTEC’s liability on any
claim of any kind, including negligence, loss, or damages arising out of, connected with, or from the performance
or breach thereof, or from the manufacture, sale, delivery, resale, repair, or use of any item or services covered
by this agreement or purchase order, shall in no case exceed the price allocable to the item or service furnished
or any part thereof that gives rise to the claim. In the event ORTEC fails to manufacture or deliver items called
for in this agreement or purchaseorder, ORTEC’s exclusiveliabilityandbuyer’s exclusiveremedy shallbe release
of the buyer from the obligation to pay the purchase price. In no event shall ORTEC be liable for special or
consequential damages. Quality Control
Before being approved for shipment, each ORTEC instrument must pass a stringent set of quality control tests
designed to expose any flaws in materials or workmanship. Permanent records of these tests are maintained for
use in warranty repair and as a source of statistical information for design improvements.
Repair Service
If it becomes necessary to return this instrument for repair, it is essential that Customer Services be contacted in
advance of its return so that a Return Authorization Number can be assigned to the unit. Also, ORTEC must be
informed, either in writing, by telephone [[phone]] or by facsimile transmission [[phone]], of the
nature of the fault of the instrument being returned and of the model, serial, and revision ("Rev" on rear panel)
numbers. Failure to do so may cause unnecessary delays in getting the unit repaired. The ORTEC standard
procedure requires that instruments returned for repair pass the same quality control tests that are used for
new-production instruments. Instruments that are returned should be packed so that they will withstand normal
transit handling and must be shipped PREPAID via Air Parcel Post or United Parcel Service to the designated
ORTEC repair center. The address label and the package should include the Return Authorization Number
assigned. Instruments being returned that are damaged in transit due to inadequate packing will berepaired at the
sender's expense, and it will be the sender's responsibility to make claim with the shipper. Instruments not in
warranty should follow the same procedure and ORTEC will provide a quotation.
Damage in Transit
Shipments should be examined immediately upon receipt for evidenceof externalor concealeddamage. Thecarrier
making deliveryshouldbenotifiedimmediatelyofanysuchdamage, sincethecarrier is normallyliable for damage
in shipment. Packing materials, waybills, and other such documentation should be preserved in order to establish
claims. After such notification to the carrier, please notify ORTEC of the circumstances so that assistancecan be
provided in making damage claims and in providing replacement equipment, if necessary.
Copyright © 2002, Advanced Measurement Technology, Inc. All rights reserved.
*ORTEC®is a registered trademark of Advanced Measurement Technology, Inc. All other trademarks used
herein are the property of their respective owners.

iii
CONTENTS
WARRANTY ....................................................................... ii
SAFETY INSTRUCTIONS AND SYMBOLS ............................................... iv
SAFETY WARNINGS AND CLEANING INSTRUCTIONS ..................................... v
1. DESCRIPTION................................................................... 2
2. SPECIFICATIONS ................................................................ 3
2.1. PERFORMANCE ............................................................. 3
2.2. INPUTS .................................................................... 3
2.3. OUTPUTS .................................................................. 3
2.4. CONNECTORS .............................................................. 3
2.5. ELECTRICALANDMECHANICAL................................................ 3
3. INSTALLATION .................................................................. 3
3.1. CONNECTIONTODETECTOR.................................................. 3
3.2. CONNECTIONTOAMPLIFIERS................................................. 4
3.3. INPUTPOWER .............................................................. 4
3.4. TESTPULSE................................................................ 4
3.5. DETECTORBIASINPUT....................................................... 4
4. OPERATION .................................................................... 5
4.1. GENERAL .................................................................. 5
4.2. DETECTORBIAS ............................................................ 6
4.3. ENERGYOUTPUT ........................................................... 6
4.4. TIMINGOUTPUT............................................................. 6
4.5. INPUTPROTECTION ......................................................... 6
5. MAINTENANCE INSTRUCTIONS .................................................... 7
5.1. TESTINGPERFORMANCE..................................................... 7
5.2. FACTORY REPAIR ........................................................... 8

iv
SAFETY INSTRUCTIONS AND SYMBOLS
This manual contains up to three levels of safety instructions that must be observed in order to avoid
personal injury and/or damage to equipment or other property. These are:
DANGER Indicates a hazard that could result in death or serious bodily harm if the safety instruction is
not observed.
WARNING Indicates a hazard that could result in bodily harm if the safety instruction is not observed.
CAUTION Indicates a hazard that could result in property damage if the safety instruction is not
observed.
Please read all safety instructions carefully and make sure you understand them fully before attempting to
use this product.
In addition, the following symbol may appear on the product:
ATTENTION – Refer to Manual
DANGER – High Voltage
Please read all safety instructions carefully and make sure you understand them fully before attempting to
use this product.

v
DANGER Opening the cover of this instrument is likely to expose dangerous voltages. Disconnect the
instrument from all voltage sources while it is being opened.
WARNING Using this instrument in a manner not specified by the manufacturer may impair the
protection provided by the instrument.
CAUTION To prevent moisture inside of the instrument during external cleaning, use only enough liquid
to dampen the cloth or applicator.
SAFETY WARNINGS AND CLEANING INSTRUCTIONS
Cleaning Instructions
To clean the instrument exterior:
! Unplug the instrument from the ac power supply.
! Remove loose dust on the outside of the instrument with a lint-free cloth.
! Remove remaining dirt with a lint-free cloth dampened in a general-purpose detergent and water
solution. Do not use abrasive cleaners.
! Allow the instrument to dry completely before reconnecting it to the power source.

vi

1
NOTICE
This preamplifier has been shipped to you with its
protection circuit connected into the input circuit.
The protection circuit prevents destruction of the
input FET due to large transients that may occur
duringabnormal operatingconditionsandservesas
an impedance matching termination for the input
cable from the detector. The presence of the
protection circuit imposes only a slight resolution
degradation. With the protection circuit installed,
the preamplifier is immune to almost anything the
operator is likely to do that causes transients at
either the detector input or the bias input connector.
The protection circuit does not protect the detector,
but even if the detector breaks down as a result of
overvoltage, the preamplifier will survive the
resulting large transients if the protection circuit is
in. This, of course, would not be true if the
protection circuit were taken out, in which case the
input FET is very susceptible to destruction by
transients at the input connector on the
preamplifier.
If the input protection circuit must be taken out for
any reason, this involves disconnecting one
transistorleadandinstalling a jumper acrossa 51
S
series resistor. The Warranty of the 142IH is void if
the protection circuit is taken out unless all of the
following precautions are taken:
1. COMPLETELY DISCHARGE the bias circuitry
before connecting a lowimpedance, a cable, orany
other capacitive device to the Input connector on
the preamplifier.
2. Discharge the bias circuitry before making any
connections to the Input connector and before
disconnecting the preamplifier from the detector.
3. To discharge the bias circuitry, connect a low
impedance (shorting cap is preferred) for at least
one minute across the Bias connector on the
preamplifier.
The input circuit will be destroyed if the Input
connector isshorted while the bias components are
charged, and the quality of these capacitors is such
that they will retain a charge through a long period
of time. Such a short could result from connecting
a detector, cable, or other capacitive device such
as a voltmeter probe. A short circuit, either short
term or continuous, will cause the applied bias
(stored on C2) to be coupled directly to the input
transistor, causing a catastrophic breakdown.
If a variable bias supply is used, merely turn down
the voltage control to zero and leave it for at least
one minute. This will suffice since the bias circuitry
can discharge itself through the output of the bias
supply.
Sometimes it is necessary to simply disconnect the
bias supply, such as is the case when using
batteriesforbias.Thissituationleavesnodischarge
path, so a path must be provided by placing ashort
circuit or low impedance across the Bias connector
on the rear panel of the preamplifier. DO NOT
SHORT THE INPUT CONNECTOR on the front
panel of the instrument unless the input circuitry
has been completely discharged.

2
ORTEC 142IH PREAMPLIFIER
1. DESCRIPTION
TheORTEC142IHcharge-sensitive Preamplifieris
designed as a minimum-cost general-purpose unit.
It is intended for use in systems where the detector,
rather that the preamplifier, is the major noise
source in the system or in systems where the
ultimatein performance is not required andthe cost
of the system must be minimized. It can be used
with semiconductor detectors, proportional
counters, scintillation counters, ionization
chambers, etc.
A bias circuit is included to accept the operating
voltage required by the detector and to furnish this
bias out to the detector through the signal input
cable. The bias input circuit in the 142IH
Preamplifier includes a 100-M
S load resistor, R4,
and any detector leakage current will have to pass
through this resistance as well as through R1,
1.5 M
S , in series. A considerable voltage drop will
be expected across this 100-M
S resistor for a
detectorwithhighleakage,andresistorR3(shipped
as an accessory) can be installed in parallel with
R4; R3 has a value of only 10 M
S .
An input protection circuit is built into the
preamplifier. It protects the input FET from any
large transient voltages that would otherwise
damage the transistor. This is discussed in the
Notice inside the front cover. The protection circuit
also provides a damping resistance on the input so
that relatively long cable lengths can be used
between the detector and the preamplifier without
disrupting the system stability.
A Test Pulse connector with built-in charge
terminator is provided for use with a pulse
generator such as the ORTEC 419, 448, or 480 to
simulate the signal from the detector. This allows a
check of the system performance while an
experiment is in progress.
The 142IH will accommodate up to ±3000 V for the
detector. The output pulse polarity is the same as
the applied bias polarity. The 142IH Preamplifier
output can be connected to a shaping main
amplifier such as the ORTEC 451, 485, or 572 for
energy spectroscopy or to a timing filter amplifier
such as the ORTEC 474 for time spectroscopy.
Output connectors are provided so that both types
of analysis can be operated simultaneously.
If it is necessary to open the case for any reason,
observe the following instructions carefully to
prevent serious injury to yourself and/or damage to
the instrument.
Observe the steps that are included in the
Notice at the front of the manual to discharge
thehighvoltageandprevent shock; thevoltage
levels that can be used are lethal and the
capacitors are very high quality so they retain a
charge much longer than normally expected.
Do not touch the high-megohm resistors, R4
and R7, with your bare fingers; the presence of
skin oil can reduce the resistance of the
component and alter operating characteristics.
See Section 4 for instructions that involve the
protection circuit.

3
2. SPECIFICATIONS
2.1. PERFORMANCE
NOISEIncreaseswithincreasinginputcapacitance.
Typical performance values, based on silicon
equivalent of
, = 3.6 eV at J = 2µs, are 1.9 keV at
0 pF; these degrade to 4.6 keV at 100 pF and to
35 keV at 1000 pF.
RISETIME Based on a +0.5V signal through either
output into a 93
S circuit and measured from 10%
to 90% of peak amplitude; 20 ns at 0 pF and 50 ns
at 100 pF.
SENSITIVITY Nominal, measured through either
output, 45 mV/MeV Si.
ENERGY RANGE 0 to 100 MeV Si.
ENERGY RATE 3 X 105MeV/s.
DYNAMIC INPUT CAPACITANCE 10,000 pF.
INTEGRAL NONLINEARITY
# 0.05% for 0 to ±7 V
open circuit, or ±3.5 V terminated in 93
S .
TEMPERATUREINSTABILITY
# ±100ppm/°,273
to 323 K (0 to 50°C).
DETECTOR BIAS ISOLATION ±3000 V.
OPEN LOOP GAIN
$ 40,000.
2.2. INPUTS
INPUT Accepts input signal from a detector and
extends operating bias to the detector.
BIAS Acceptsthe biasvoltage forthe detector from
a bias supply.
TEST PULSE Accepts input voltage pulses from a
pulse generator for instrument and system check
and calibration; Rin = 93
S .
2.3. OUTPUTS
EANDT (forEnergyand Timing)Twoconnectors
furnish identical signals through two output paths;
either or both outputs can be used as required, and
they are interchangeable; R0= 93
S through each
connector and the output polarity is opposite from
the input pulse polarity (output pulse polarity is the
same as bias polarity).
2.4. CONNECTORS
INPUT and BIAS Type SHV.
TEST PULSE, E, and T Type BNC.
POWER CABLE 10-ft (3 m) captive power cable,
ORTEC 121-C1; longer lengths available from
ORTEC on special order.
2.5. ELECTRICAL AND MECHANICAL
POWER REQUIRED Furnished from NIM bin and
power supply through any ORTEC main amplifier,
or from an ORTEC 114Preamplifier Power Supply;
built-in captive cable is compatible with either
source.
+24 V, 30 mA; -24 V, 10 mA; +12 V, 15 mA;
-12 V, 15 mA.
DIMENSIONS 1.5 x 2.4 x 4.5 in., plus 10-ft cable
(38 x 61 x 114 mm, plus 3 m cable).
3. INSTALLATION
3.1. CONNECTION TO DETECTOR
A direct connection with shielded cable should be
made between the detector and the Input SHV
connector on the preamplifier. The performance of
the 142IH Preamplifier, like that of all similar
instruments, is degraded as the capacity at the
input increases. Therefore it is important that the
length of coaxial cable used between the detector
and the preamplifier be kept at the minimum length
that is necessary. Alsoit ispreferable to use 93
S or
100
S characteristic impedance cable rather than
75
S or 50 S cable because the capacity per foot is
less for the cable with the higher characteristic
impedance. Type RG-62/U cable is recommended;
this has a 93
S impedance and a capacitance of
13.5 pF/ft (40.1 pF/m). An AMP 51426-2 connector
mates with the SHV connector on the 142I
Preamplifier.

4
Once the input cable installation has been made,
the electronic noise performance of the 142IH can
be predicted by calculating the cable capacity from
the above information and adding the capacity
expected from the detector.
3.2. CONNECTION TO AMPLIFIERS
Either or both the E and T outputs of the 142IH can
be connected to an amplifier input for further
processing.Theoutput impedancethrougheitherof
these connectors is 93
S , providing a series
terminationfor93
S cablesothatlongcablelengths
can be driven easily. Although the outputs are
marked E (for Energy) and T (for Timing), the pulse
characteristics are identical and the circuits are
interchangeable.
In an energy spectroscopy system, the preamplifier
output is furnished into a shaping main amplifier. In
a timing spectrometer system, the preamplifier
output isfurnishedinto atimingfilteramplifier. With
the dual output connections on the 142IH, the
signals can be furnished simultaneously to both
types of spectrometer systems. If either the E or T
output connector is not being used, it should simply
be left open-circuited (unterminated).
3.3. INPUT POWER
Power for the 142IH is supplied through the Power
Cable that is captive through the rear panel of the
unit. The normal connection for this power cable is
included on the rear panel of the mating ORTEC
amplifier, furnishing ±12 V and ±24 V from the bin
andpowersupplyinwhichtheamplifierisoperated.
If thisfacility isnot availableor if such a connection
would increase the loading on the bin and power
supply beyond its maximum rated capacity, use an
ORTEC 114 Preamplifier Power Supply to furnish
the operating power requirements through the
captive cable. The ORTEC 114 can furnish power
for two ORTEC preamplifiers simultaneously if
desired.
3.4. TEST PULSE
A voltage test pulse for energy calibration can be
acceptedthrough the TestPulse input connector on
the 142IH without the use of an external charge
terminator. The test input of the preamplifier has an
input impedance of 93
S and its circuitry provides
charge injection to the preamplifier input. The
shape of this pulse should be a fast risetime (less
than 40 ns) followed by a slow exponential decay
back to the baseline (200 to 400 µs). While the test
pulses are being furnished, connect either the
detector (with bias applied) or the equivalent
capacitance (without bias applied) to the Input
connector on the 142IH.
The Test Pulse input may be used in conjunction
with the output of a pulser such as the ORTEC 419
or 448 to calibrate the preamplifier E output
amplitude in terms of energy for calibration of a
multichannel analyzer. However, due to stray
coupling between the test circuit and other portions
of the preamplifier circuitry, the transient
performance of the preamplifier is best determined
byconnecting theactual detectorsignal throughthe
Input connectorinsteadof usingthepulsegenerator
output signals for this calibration.
A voltage test pulse for transient response in the
142IHcanbeacceptedthroughachargeterminator
and into the Input connector on the 142IH. If
external capacitance is to be included for these
tests, anSHV tee can beinsertedbetweenthe Input
connector and the charge terminator, and this will
then accommodate the test capacitances. Do not
furnish any bias during these tests.
3.5. DETECTOR BIAS INPUT
Operating bias for the detector is supplied to the
Bias connector on the 142IH and, through a filter
and a large bias resistance, to the Input signal
connector.From thereitisfurnishedoutthroughthe
signal input cable to the detector.
Connect a cable from the detector bias supply
(ORTEC428or 459istypical)to theBiasconnector
on the142IH. Type SHV connectorsare used in this
high-voltage circuit and the mating cable shouldbe
furnished with the bias supply module.