[ RadSafe ] x-ray tube fade

[cehn at aol.com]

Doing QC checks with a dental x-ray unit & RadCal, I'm seeing fading of the dose with successive exposures.  Did 10; the first 2 were about the same dose (~40 mrem; 77 kVp, 12 mA; 2.5 sec).  Next 8 dropped by about 0.1% each time. Final exposure was about 1% less than the first. Steady drop.  But kVp measurements held steady.  Is this normal, or does it indicate a problem?  Thanks in advance.
 
Joel Cehn
joelc at alum.wpi.edu
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