ORTEC DSPEC 50, Руководство пользователя по оборудованию

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932502G / 0618 4, 5. MCB PROPERTIES IN MAESTRO
of the noise by physical means such as common grounding between detectors and instruments,
shielding cables, removing nearby motors/generators, etc. If you cannot eliminate the noise,
increase the rejection level setting until the dead time returns to the expected low value.
!
Note that higher values may reduce the effectiveness of the pile-up rejector when
processing very low-energy pulses.
!
On systems for which very high dead times are expected (i.e., >60%), especially with
very-low-energy sources (e.g.,
241
Am), decreasing this setting can improve the
performance of the spectrometer with respect to live-time correction and the ability to
process signals at higher input rates.
Enhanced Throughput Mode — See Section 1.4 for a discussion of this feature. The valid
Protection Time settings, in 25-ns increments, range as follows:
LFR Mode Highest Throughput
(minimum Protection Time)
Lowest Throughput
(maximum Protection Time)
Off (Rise Time + flattop) (2 × Rise Time + Flattop)
On (3 × Rise Time + 2 × Flattop) (6 × Rise Time + 3 × Flattop)
Turning on this feature automatically sets the minimum protection time (highest throughput
rate) based on your current
Rise Time and Flattop settings, however, you can adjust this value
at any time. Each time you change the rise time or flattop, the DSPEC 50 will automatically set
itself to the new minimum protection time.
Inhibit Width (Advanced Models Only) —Sets a minimum inhibit signal time from 0 to 200
us in increments of 0.025 us. If the inhibit signal is still high after this time period has elapsed
then the inhibit signal remains high until the input signal goes low. The minimum inhibit
width restarts when the inhibit signal goes low and returns to high.
Manual Fast Chan Threshold (Advanced Models Only) —This setting allows setting the
fast channel threshold manually as may be desired when optimizing timing systems that trigger
off the fast channel of two or more detectors. The fast channel refers to the start of a pulse
detection as the signal increases beyond the normal noise level using a very short rise time
filter. This pulse is too noisy for spectroscopy, but it is useful in determining the pulse arrival
time. When the fast channel output exceeds the Fast Channel Threshold then a Fast Channel
event is generated and used to control Live Time, Pileup Rejection, and the Count Rate Meter.
Setting this value too low could significantly increase the system dead time. Setting this value
too high could result in peak detection without the corresponding fast channel event which
could affect pileup rejection and coincidence timing performance.
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