EG&G ORTEC 113 Manual de operação e serviço - Página 6
Procurar online ou descarregar pdf Manual de operação e serviço para Amplificador EG&G ORTEC 113. EG&G ORTEC 113 9 páginas. Scintillation preamplifier
Imprimir páginaimpedance of the 113 is 93S2; therefore if the 93f2 cable is
used, it is not necessary to terminate it at the receiving end. If
unterminated cable is used on the output, with impedance
other than 93f2, resistor R24 should be adjusted for an
output impedance equal to the value of the cable imped
ance to prevent pulse reflections.
3.3. INPUT POWER
Power for the 113 is supplied through an Amphenol
connector (17-20090) on the rear of the chassis. Power
may be supplied by a single 45-V battery with a tap at
22.5 V (use the tap as ground, providing -1-22.5 V and
-22.5 V; current drain is 17 mA)or by any well-filtered
±24-V power supply such as the ORTEC 114 Preamplifier
Power Supply.
If the 113 is used with ORTEC transistor main amplifiers,
power for the preamplifier can be supplied from the main
amplifier through the interconnecting cable supplied with
the 113.
3.4. TEST PULSE
A voltage pulse can be inserted at the Test Pulse connector
on the rear of the 113. The 113 has a built-in charge
terminator that converts the input voltage to an input
charge to simulate a charge pulse from the photomultiplier
tube. The shape of the voltage test pulse should have a fast
rise time (less than 10"® sec) followed by a slow ex
ponential decay back to the baseline (2 to 4 x 10""* sec).
A 1-V input signal at the Test Pulse connector produces a
pulse of approximately 135 mV when an input capacity of
1 GO pF is selected by SI.
4. OPERATING INSTRUCTIONS
The shape of the output pulse from the photomultiplier
tube is dependent on the form -of the l ight pulse, the
transit-time spread in the photomultiplier, and the anode
resistance and capacitance. Since the form of the light
pulse and the transit time of the tube cannot be altered, our
concern is with the anode and associated circuitry. The
signal at the anode appears as a current pulse or a quantity
of charge, and the voltage produced by this quantity of
charge is given by
where C = Cj -t Cjn (see Fig. 4.1). (Cj and C2 are coupling
capacitors that are large in value compared to C, and
therefore accumulate a negligible amount of voltage from
the charge transferred.) The voltage developed across
Cy + Cjn wil l decay with a time constant of ry= R^C, where
Rr =
Rin (
+ Rj)
Rin + Ri + Rs
and R5 = high-voltage supply output resistance.
From the above equations it can be seen that the pulse
amplitude can be varied by varying Cjn, which can be
ANODE
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1 ^Bin
Fig. 4.1. Functional Diagram of the 113 Preamplifier.
varied by steps with switch SI on the front panel. The input
capacity of the 113 is approximately 45 pF plus the
capacity selected by SI. Rjn was selected to produce a fall
time constant of 50 insec, assuming a driving source im
pedance of 1 X 10® f2. If a pole-zero-cancelled amplifier
is used following the 113, it wil l be necessary to adjust the
pole-zero trim on the amplifier each time a different input
capacitance is selected for the 113.