Geiger Muller Tube time constant to correct for count rate loss.

[lhetrick]

Hello All,

I am playing with some questions in an old textbook I have been reading through and I am getting confused on this question regarding GM Tubes.The question that is stumping me goes like this:

If a certain GM Tube has a time constant of 80msecs and procedures require that count rate corrections be applied if more than 5% of the counts are lost, At what count rate per minute would count rate corrections need to start being applied?

I have read around in the book and can not find to much on the time constant. My idea is that I could do the following:

1min*(60s/1min)*(1/.08s)=750counts

750*.95=712.5counts

I just want to make sure that I am going about this the right way and not misleading myself here. Any help on this would be greatly appreciated.

Luke

 

[AndyW]

Hello Luke,

Thank you for reaching out with your question. The time constant of a GM Tube refers to the time it takes for the tube to recover from a pulse and be ready to detect another pulse. In other words, it is the time required for the tube to reset itself after detecting a pulse.

In order to answer your question, we need to consider the relationship between count rate and time constant. The count rate is directly proportional to the time constant, meaning that a longer time constant will result in a lower count rate and vice versa. So, if we know the time constant and the desired percentage of counts lost, we can calculate the count rate at which count rate corrections should be applied.

In this case, we know that the time constant is 80 milliseconds (0.08 seconds) and the desired percentage of counts lost is 5%. So, we can set up the following equation:

(0.08s/1)*(x counts/60s)= 5% of x counts

Solving for x, we get a count rate of 75 counts per minute. This means that if the count rate exceeds 75 counts per minute, count rate corrections should be applied.

I hope this helps clarify the concept of time constant and how it relates to count rate. Let me know if you have any further questions or if you need any additional clarification. Keep up the good work with your studies!