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I would like to know what exactly is the "ticking" sound produced when using solid state Unfors Survey detector, i.e., when it is connected to its Xi Base unit and turned "ON" in the R/F mode, what is the the Survey detector actually measuring during this stand-by period, i.e., no radiation source present and just before diagnostic X-rays are produced. During this stand-by period, the meter Dose display (in Roentgens) continuously accumulates until the detector is switched OFF. The unit obviously "ticks" when responding to direct or scatterd X-rays when they are produces but what is it responding to when there is no X-radiation? Is it the same response to cosmic and environmental gamma radiation as that of a Geiger tube instrument? Or is it simply electronic noise? Note: Unlike the Geiger tube, the solid state Survey detector is diode based detector and calibrated to the diagnostic X-ray and medical nuclear gamma radiation range. Thanks

I tried to measure the environmental background radiation in my (radiation source free) office. This was to establish a base line background measurement when the detector is in stand-by, to subtract from the total measurement following exposure to actual X-rays, i.e., the net X-ray dose. I performed several (30) consecutive 10 minute measurements. The results indicated a very wide variation. i.e., Mean: 30.6 micro-Roentgens, Standard Deviation: 27.9 micro-Roentgens, resulting in a Coefficient of Variation of 0.915. This seems that the either the solid state Survey detector assembly is mal-functioning or that the detector is not actually measuring environmental background radiation, i.e., simply displaying random internal electronic noise. Similar environmental radiation measurements, using a properly functioning Geiger tube instrument, would typically provide a more reliable result with a Coefficient of Variation of about 0.15 to 0.2 maximum.

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Almost all of that background will be due to electrical and thermal noise in the electronics and the detector.

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