ORTEC DSPEC Pro, Руководство пользователя по оборудованию

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DSPEC Pro
®
Digital Gamma-Ray Spectrometer User’s Manual 794380D / 0914
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Patent number 6,327,549.
10
Mode Uncorrected
Spectrum
ZDT Corrected
Spectrum
ZDT Error
Spectrum
Off (ZDT Disabled) Yes No No
NORM_CORR (ZDT–LTC Mode) Yes Yes No
CORR_ERR (ZDT–ERR Mode) No Yes Yes
Table 1. ZDT Modes.
will no longer be counting the same source as when the losses occurred. As a result, the number
of counts in the peak will not be correct.
When a supported ORTEC MCB operates in ZDT
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mode, it adjusts for the dead-time losses by
taking very short acquisitions and applying a correction in real time — that is, as the data are
coming in — to the number of counts in the spectrum. This technique allows the gamma-ray flux
to change while the acquisition is in progress, yet the total counts recorded in each of the peaks
are correct. The resulting spectrum has no dead time at all — in ZDT mode, the data are correc-
ted, not the acquisition time. Thus, the net counts in a peak are divided by the real time to deter-
mine the count rate.
ZDT mode has a unique feature in that it can store both the corrected spectrum and the uncor-
rected spectrum, or the corrected spectrum and the uncertainty spectrum. Therefore, supported
MCBs allow you to choose between three ZDT Mode settings on the ADC tab under MCB
Properties...: Off, NORM_CORR, and CORR_ERR.
Table 1 shows which spectra are collected in the three possible ZDT modes.
1.6.1. Off — Uncorrected Spectrum Only
In this mode, only the uncorrected spectrum (live time and real time with dead-time losses) —
also called the live-time-corrected or LTC spectrum — is collected and stored in the
.SPC
file.
The LTC spectrum can be used to determine exactly how many pulses at any energy were pro-
cessed by the spectrometer. The corrected spectrum gives the best estimate of the total counts
that would have been in the peak if the system were free of dead-time effects. The uncertainty
spectrum can be used to calculate the counting uncertainty, channel by channel, in the corrected
spectrum.