Mirion Technologies Lynx II DSA User Manual

Live Time Correction With a Live Source
Lynx II DSA User's Manual – 7096089 169
5. Position the
60
Co source near the Ge detector and adjust for an incoming count rate
of 2 to 5 kcps. The 1173.2 keV
60
Co reference peak should be at approximately
80% of the spectral full scale range. If necessary, adjust the Lynx II gain to
properly locate the peak.
Note: Once in place, the source should not be moved or altered in any way for the
remainder of the experiment!
6. Clear the MCA and acquire a spectrum for 500 live seconds. Record the net area of
the 1173.2 keV
60
Co peak (source “A”).
7. To the
60
Co source, add approximately 25 kcps of
137
Cs to make the total incoming
rate 30 kcps.
8. Clear the MCA, Collect a new spectrum for 500 live seconds, and record the net
area of source “A”.
9. Compare the net area of the 1173.2 keV
60
Co peak acquired in step 6 and compute
the percentage change
10. If improvement is needed, try adjusting the LT TRIM slightly and repeat steps 6
through 9 until an optimum setting is achieved. The LT Trim function is located on
the Gain Device Adjust screen. The value can be decremented/incremented over a
range of 0 to 1000 using the adjustable slide bar (the default setting is 500).
Since the detector-source geometry was maintained and the preset Live Collection
time was held constant, the
60
Co (1173.2 keV) net area can be used as a standard
when comparing the effect of adding background counts from the
137
Cs (661 keV)
source.
Note: Lowering the LT Trim value will decrease the system dead time and counts in
the reference peak area at high count rates. Likewise, increasing LT Trim will
increase the system dead time and counts in the reference peak area.
11. Set the LTC ON/OFF switch to Off. Repeat steps 4 through 9. Compare the
deviation of source “A’s” spectrum when the LTC is ON and the LTC is OFF.
With the LTC OFF, large changes will be observed in the reference net peak are
a function of count rate. With the LTC set ON, changes in the reference peak net
the area will be significantly reduced. The Live Time corrector extends the
collection
time compensating for signal processing time and events rejected due to pileup.
Note: Performance may vary and is dependent on factors such as spectrum energy
distribution, detector characteristics such as geometry, size, and detector
ballistic deficit.

Mirion Technologies Lynx II DSA Specifications

General

Brand	Mirion Technologies
Model	Lynx II DSA
Category	Measuring Instruments
Language	English