GammaVision
®
v7 (A66-BW) 783620H / 1013
coincidence, the gating input signal
must not be present for the conversion of the detector signal. The gating signal must occur prior to and extend 500 ns beyond peak detect (peak maximum).
ZDT Mode — Use this droplist to choose the ZDT Mode to be used for collecting the desired zero dead time spectrum (see Section 5.2.11.4).
The three modes are Off (LTC only),
NORM_ CORR (LTC and ZDT), and CORR_ERR (ERR and ZDT).
If one of the ZDT modes is selected,
Fig. 80. DSPEC-50 ADC Tab.
both spectra are stored in the same spectrum (
.SPC
) file. If you do not need the ZDT spectrum, you should select Off. In Gamma-
Vision, the display can show either of the two spectra. Use <F3> or Acquire/ZDT Display
Select to toggle the display between the two spectra. In the Compare mode, <F3> switches both spectra to the other type and <Shift+F3> switches only the compare spectrum. This allows you to make all types of comparisons.
Conversion Gain — This sets the maximum channel number in the spectrum. If set to 16384, the energy scale will be divided into 16384 channels. The conversion gain is entered in powers of 2 (e.g., 8192, 4096, 2048). The up/down arrow buttons step through the valid settings for the
DSPEC-50.
Upper- and Lower-Level Discriminators — The Lower Level Discriminator sets the level of the lowest amplitude pulse that will be stored. This level establishes a lower-level cutoff by channel number for ADC conversions. The Upper Level Discriminator sets the level of the highest amplitude pulse that will be stored. This level establishes an upper-level cutoff by channel number for storage.
Stabilizer
The DSPEC-50 has both gain and zero stabilizers (see Section ?). This tab (Fig. 81) shows the current stabilizer settings. Each Adjustment section shows how much adjustment is currently applied. The Initialize buttons reset the adjustment to 0. If the value approaches 90% or above, adjust the amplifier gain so the stabilizer can continue to function — when the adjustment value reaches 100%, the stabilizer cannot make further corrections in that direction. The
Center Channel and Width fields show the peak currently used for stabilization.
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