URSA-II Odd Spectrum Display

Skip to first unread message

Keith Brown

Sep 12, 2023, 11:45:56 AMSep 12
to URSA-II MCA Users Group
I have notice something odd about the appearance of a spectrum I collected, and I am hoping someone has some insight. Our URSA-II is connected to a 3x3 NaI(Tl). This spectrum was collected from an activated item. There is no background subtraction being done. When the screenshot was taken, the cursor was in the center of the second peak (the one not cut off by the discriminator). Note that the vertical scale is showing the peak at about 245,000 counts while the information bar at the bottom is showing 328,000 counts there (channel 77). The region of that peak goes from (according to the ROI panel) channel 52 to 108. Scanning to find the minima that appear to be just outside that ROI, I find them at channel 55 (24,715 counts), and on the other side at channel 115 (9543 counts). Clearly, channel 55 is inside of the ROI, but the visual shows the minimum a few channels outside the ROI.

Since I want to draw a background under each peak based on the counts above and below the peaks (yes, I should fit everything, but I do not need to be that accurate), I am concerned about the apparent discrepancy between the scales on the axes of the graph versus the numbers in the information bar. Has anyone noticed anything similar, and if so, can I assume the data in the information bar is correct?

URSA-II Spectrum.jpg


Sep 13, 2023, 7:18:38 PMSep 13
to URSA-II MCA Users Group
First, you should consider using a more recent version of the software.  The latest broad release can be downloaded from https://seintl.com/media/downloads/URSA-II_MCA_64-bit_Software.zip.  I believe it's version 2.0.30.

What you are seeing isn't really a bug.  You have the spectrum smoothing factor set to 24 but the cursor channel is showing the value of the raw spectrum.  Change your smoothing factor to 0 and you'll see there isn't any discrepancy.

Best Regards,

Reply all
Reply to author
0 new messages