ORTEC 109A - Description; Specifications

1
ORTEC 109A PREAMPLIFIER
1. DESCRIPTION (See Block Diagram)
The 109A is an all-transistor preampl ifier with pole-zero
cancel lation using a field-effect transistor in the input stage.
The circuitry includes a charge-sensitive input loop, an
amplifier stage with switch-selectable gain with a 10:1 ratio,
and a cable driver stage. The preampl ifier is inherently an
inverting preampl ifier: i.e., a negative input pulse yields a
positive output pulse. No pulse shaping is accompl ished
in the preampl ifier, except for a pole-zero-cancelled 50-/xs
differentiation time constant immediately after the charge-
sensitive loop, for the purpose of reduction of pulse pileup
at high count rate. System pulse shaping for optimization
of signal-to-noise ratio wil l be accompl ished in the subse
quent main ampl ifier.
2. SPECIFICATIONS
Basis of Warranty <0.025 keV/pF FWHM (Ge) slope, 2.5 keV FWFIM (Ge) maximum at 0 pF input capacity. Typical perfor
mance is given below:
TYPICAL PERFORMANCE
Noise with 2-ns Preamplifier Output
Single RC Main Amplifier
Pulse
Input
Capacitance
FWHM Si FWHM Ge No. of rms Relative Rise Time (ns).
(pF)
(keV) (keV)
Electrons Amplitude 10-90%
0
2.85 2.29 336
1.000
15
20 3.2 2.6
377 1.000
19
50
3.72 2.99
440 1.000
25
100 5.1
4.1 601
0.996
40
200 7.9
6.4
931
0.993
68
500 16.2
13.0
1910 0.982 175
1000
30.4
24.4 3580
0.963
250
Output Pulse Shape Rise time as in table above, exponential
fal l with bO-fis time constant
Integral Nonlinearlty <0.1% for 0-5 V output span with
internal series termination
Temperature Coefficient ±0.01 %/°C
Detector Bias Isolation 1000 V dc
Input Open Loop Gain >20,000
Power Required +24 V dc at 36 mA, -24 V dc at 36 mA;
supplied from ORTEC main amplifier or from an ORTEC
114 or 115 Preamplifier Power Supply.
Power Cable 10-ft captive power cable is furnished with
each 109A.
COUNT RATE VS. ENERGY See data below, from which it
shaping amplifier.
Input Energy (MeV)
(Si Equivalent)
0.1
1
10
Power Connector Amphenol 17-20090
Saturated Output Amplitude 7 V at end of several hundred
feet of unterminated 93S7 cable
Output Source Impedance Adjustable from 50 to 150J2
Charge Sensitivity 150 mV/MeV (Si), 183 mV/MeV (Ge)
in X10 gain position; 15 mV/MeV (Si), 18.3 mV/MeV (Ge)
in XI gain position
DETECTOR, OUTPUT, AND TEST Pulse Connectors BNC
DETECTOR BIAS Connector SHV
Size 1.8 X 4 X 6 inches (4.5 x 10.2 x 15.3 cm)
Weight Net, 1.5 lb (0.7 kg); gross 2.3 lb (1.1 kg)
is obvious that in almost all cases, the count rate is l imited by the
Count Rate with 1%
Counting Losses (cts/sec)
2x10'
2 X 10'
2x10'