I am conducting some testing on a M-400 detector. The detector is housed in a 0.5 cm tungsten collimator. During Calibration Checks using a 7 uCi Cs-137 button source, the Web GUI software correctly identifies Cs-137 but also identifies Am-241. This anomaly has been repeatable with this source/detector configuration at distances of up to ~8 cm from the detector face. At distances greater than 8-10 cm from the detector face, Am-241 no longer is displayed as being present on the Calibration Check isotope identification page. Is this the expected phenomenon with this detector and what is the cause?
Howdy,
My name is David and I’m a research engineer at H3D. You are seeing tungsten X-rays: the k-alpha is roughly the 60 keV of Am241. Some devices, like our H420 with a tungsten coded aperture mask, has a filter to reject this line unless the amplitude is sufficiently high. The M400 isn’t used this logic.
I think the peak may have fallen out of statistical significance when you moved further away. Furthermore, the continuum to noise ratio would have gone up potentially putting the peak below threshold.
Email me at dgoodman@h3dgamma.com if you have any more questions.