Geiger counter unaccounted jump in count rate

In summary, we ran a program in our lab class with a 3 second gate time on a CS-147 source with a voltage of 500v and a threshold of 0.5v. We were getting an average count rate of 250 counts per 3 seconds, but overnight it unexpectedly shifted to 1500 counts per 3 seconds. The setup was not touched, leading to speculation about a janitor entering the lab. However, the increased count rates persisted even when the source was moved and continued to emit at the higher rate regardless of adjustments. It is suspected that there may have been a change in state within the tube and the lab supervisor has been informed.
  • #1
khfrekek92
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I am in a lab class and we are currently measuring count rates for a specific source. Yesterday we ran a program that runs 3 second gate times on a CS-147 source with a voltage of 500v running through the detector, and a threshold of .5v on the counter. This 3 second gate time was to be repeated 135,000 times to be done by friday. In the gate time of 3 seconds we were getting an average count rate of around 250 counts per 3 seconds. However overnight this shifted unexpectedly to around 1500 counts prt 3 seconds giving us 2 very defined gaussian peaks at 250 and 1500 in our "gaussian curve". The setup was not touched or changed at all overnight as the room was locked, and upon inspection nothing had changed except now for some reason we get much increased count rates for our same exact source. Does anyone have any idea what could possibly cause this??
Thanks!
 
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  • #2
Janitors have keys ... do they enter this lab?
 
  • #3
Yeah we thought about that too, but I can't think of anything they could do to increase the activity of a radioactive source sixfold haha? :/
 
  • #4
Counts fall off at the inverse square law ... did it continue at the new count rate?
 
  • #5
Yup. Originally the source was as close to the Geiger tube as possible, and now it's still in the same place, and continues to emit at the increased activity no matter what we do to it. It's almost as if it entered the region of spontaneous emission! Haha
 
  • #6
Then I would suspect a change of state within the tube - certainly report this to your lab supervisor.
 
  • #7
Hmmmm interesting, it definitely could be that, thank you so much!
 

1. What is a Geiger counter?

A Geiger counter is a device used to measure ionizing radiation. It works by detecting the electric charge produced by radiation, and then converting it into an audible click or visual count.

2. What is an unaccounted jump in count rate on a Geiger counter?

An unaccounted jump in count rate on a Geiger counter refers to a sudden increase in the number of clicks or counts that the device registers. This jump is unexpected and cannot be explained by any known sources of radiation in the environment.

3. What could cause an unaccounted jump in count rate on a Geiger counter?

There are several potential causes for an unaccounted jump in count rate on a Geiger counter. This could include a malfunction in the device, a sudden increase in background radiation due to natural sources such as radon gas, or a nearby source of man-made radiation.

4. Is an unaccounted jump in count rate dangerous?

In most cases, an unaccounted jump in count rate on a Geiger counter is not dangerous. It is important to note that Geiger counters are sensitive devices and can pick up small increases in radiation that pose no threat to human health. However, it is always important to investigate and determine the cause of the jump in count rate to ensure safety.

5. How can an unaccounted jump in count rate on a Geiger counter be addressed?

If an unaccounted jump in count rate on a Geiger counter is observed, it is recommended to first check for any obvious sources of radiation in the surrounding area. If no source is found, the device should be checked for any malfunctions or errors. If the jump in count rate persists, it is best to seek the assistance of a trained professional to investigate further.

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