ORTEC DSPEC 50, Руководство пользователя по оборудованию

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DSPEC 50
®
and DSPEC 502
®
Digital Gamma-Ray Spectrometer User’s Manual 932502G / 0618
Gain — Set the amplifier coarse gain by selecting from the Coarse droplist, then adjust the
Fine gain with the horizontal slider bar or the edit box, in the range of 0.5 to 1.1. The resulting
effective gain is shown at the top of the Gain section. The two controls used together cover
the entire range of amplification from 0.5 to 140.8.
Input Polarity — These buttons select the preamplifier input signal polarity for the signal
from the detector. Normally, GEM (p-type) detectors have a positive signal and GMX (n-type)
have a negative signal.
Baseline Restore
— This is used to return the baseline of the pulses to the true zero between
incoming pulses. This improves the resolution by removing low frequency noise from dc shifts
or mains power ac pickup. The baseline settings control the time constant of the circuit that
returns the baseline to zero. There are three fixed choices (
Auto ,
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Fast , and Slow ). The fast
setting is used for high count rates, the slow for low count rates. Auto adjusts the time constant
as appropriate for the input count rate. The settings ( Auto , Fast , or Slow ) are saved in the
DSPEC 50 even when the power is off. The time constant can be manually set on the InSight
display (see the discussion beginning on page 42).
You can view the time when the baseline restorer is active on the InSight display as a
Mark
region (see the discussion on Marks, p. 44). In the automatic mode, the current value is shown
on the InSight sidebar (Fig. 34). For a low-count-rate system, the value will remain at about 90.
Preamplifier Type — Choose Transistor Reset or Resistive Feedback preamplifier
operation. Your choice will depend on the preamplifier supplied with the germanium detector
being used.
Pile-up Rejection (Advanced Models Only) — This option allows the Pile-up Rejection to be
enabled or disabled as selected. By default Pile-Up Rejection is enabled to eliminate pile up
pulses that contribute to noise in the spectrum. Note that the Pile-Up Rejection can also be
enabled or disabled using hardware commands with the DIAG program for the Standard or
Advanced models.
4.1.1. Optimize
The DSPEC 50 is equipped with both automatic pole zero logic
4
and automatic flattop logic.
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The Start Auto (optimize) button uses these features to automatically choose the best pole zero
and flattop tilt settings. Note that if you selected Transistor Reset as the Preamplifier Type
for this DSPEC 50, optimization does not perform the pole zero.
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Patent number 5,821,533.
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