URSA II TIME setting and deadtime question

Skip to first unread message


Jul 8, 2015, 10:22:34 AM7/8/15
to URS...@googlegroups.com
Is the TIME setting live time or clock time? Can it be altered to one or the other?
Is there an indicator of % deadtime in the MCA mode to assist in geometry selection?

George Dowell


Jul 9, 2015, 9:36:12 AM7/9/15
to URS...@googlegroups.com
Hello George,
Dead-time is handled somewhat differently with the URSA-II than in most other MCAs because the spectrum is not accumulated within the device.  Each pulse height measurement is transmitted to the PC as it is taken (as a three-byte packet) and that transmission time is responsible for the majority of the "dead time," as the processor cannot measure a pulse height simultaneously with sending out data.
However, the processor can keep track of the number of counts that exceed the threshold, whether pulse-height analyzed or not.  So the number of "unanalyzed pulses" is included with the transmitted packet, and the spectrum is adjusted accordingly.  All that is a long way of saying that it automatically compensates for dead-time losses...  In most cases at moderate count rates the corrections are practically negligible.  Under the Misc menu is a setting where you can disable the dead time correction.  Oh, and therefore count times are always real/clock time.
I encourage you (and anyone who wants it) to download the latest beta URSA-II software from https://dl.dropboxusercontent.com/u/75707783/RSA/URSA_MCA_v2.1.12_Setup.exe

It does display the percent dead time, and has a bunch of other features (including the ability to import BNC/Termo N42 files).  Alas, the manual has not kept up with all of the changes.  Interested in being hired to write a manual?
Best Regards,
Paul R. Steinmeyer
Health Physicist, Electronics and Software Design
Radiation Safety Associates, Inc.
PO Box 107/19 Pendleton Drive
Hebron, CT 06248
Phone: 860/228-0487
Fax: 860/228-4402
Reply all
Reply to author
0 new messages