GammaVision
®
v7 (A66-BW) 783620H / 1013
Just as for the PHA mode display, the vertical scale can be adjusted with the vertical adjustments. The display can be set to Log mode, but the peak shapes do not have a familiar shape in this display. The Auto mode will adjust the vertical scale for each pulse. The pulse is shown before the amplifier gain has been applied, so the relation between channel number and pulse height is not fixed.
The horizontal scale extends from 16 to 256 channels. The display is expanded around the marker position which means that in some cases the peak will disappear from the display when it is expanded.
The display can be switched from the current MCB to another Detector or the buffer. The other
Detector will be shown in its most recent mode (PHA or InSight). The buffer will always be shown in PHA mode. When you return to the current MCB, the display will return to the InSight mode. This also holds true if you exit GammaVision while in InSight mode; on next startup, this
MCB will still be in InSight mode.
The display can include a Mark to indicate one of the other signals shown in Fig. 89. The Mark is a solid-color region displayed similarly to that of an ROI in the spectrum. This Mark can be used to set the timing for the gate pulse. It can also be used to set the shaping times and flattop parameters to get the best performance. For example, suppose you need to obtain the best resolution at the highest throughput possible. By viewing the pulses and the pileup reject marker, the rise time can be increased or decreased to obtain a minimum of pileup reject pulses.
Fig. 89. Mark
List.
Mark Types
For the Mark, choose either “points” or “filled” (to the zero line) display. This is controlled by the selection in the Display/Preferences menu item. That choice does not affect the PHA mode choice. The colors are the same as for the PHA mode. (Not all DSP MCBs support all marks.)
None
No channels are marked in the display.
PUR
BLN
The region marked indicates when the PUR circuit has detected pileup and is rejecting the marked pulses.
This shows when the negative baseline discriminator has been triggered. Typically this signal only marks the TRP reset pulse. The signal is used internally in the live-time correction, baseline restoration, and pile-up rejection circuits.
BLRG
This shows when the baseline restorer is actively restoring the baseline.
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783620H / 1013 5. MENU COMMANDS
BLD
BUSY
This shows when the positive baseline discriminator has been triggered. The signal is used internally in the live-time correction, baseline restoration, and pileup rejection circuits.
When the busy signal is active, Busy shows in the Mark box. It represents the dead time.
GATE
This shows when the gate signal is present on the gate input connector. If the
Gate mode on the ADC tab (see Fig. 88) is set to Off, then all regions are marked. If the mode is set to Coincidence, then the marked region must overlap the pulse peak (that is, must start before the beginning of the flattop and stop after the end of the flattop) for the pulse to be counted. If the mode is set to Anticoin-
cidence, then the marked region will show the pulses that are accepted. That is, the rejected peaks will not be marked. Simply put, in all modes the accepted peaks are marked.
RESV
Reserved.
PKDET
This is the peak detect pulse. It indicates when the peak detect circuit has detected a valid pulse. The Mark occurs about 1.5
μs after the pulse maximum on the display.
On the lower right of the InSight display are the shaping parameter controls. The controls are split into two groups, and the other controls... button switches between them. (Not all DSP
MCBs support all of the controls.)
One group includes Rise Time, Flattop, Tilt, and the Optimize button. The Rise Time value is for both the rise and fall times; thus, changing the rise time has the effect of spreading or narrowing the quasi-trapezoid symmetrically.
The Flattop controls adjust the top of the quasi-trapezoid. The Width adjusts the extent of the flattop (from 0.3 to 2.4
μs). The Tilt adjustment varies the “flatness” of this section slightly. The
Tilt can be positive or negative. Choosing a positive value results in a flattop that slopes downward; choosing a negative value gives an upward slope. Alternatively, Optimize can set the tilt value automatically. This value is normally the best for resolution, but it can be changed on this dialog and in the InSight mode to accommodate particular throughput/resolution tradeoffs. The
Optimize button also automatically adjusts the pole-zero setting.
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