Re: Calibration of a source

[Bernard L Cohen <blc+@pitt.edu>]

On Fri, 5 Jun 1998, Peter Skeels wrote:

> Dear Radsafers,
> 
> 	I am interested in finding a company who can come to our university 
> and calculate an activity of our Co-60 source.  I am told that years 
> ago the Army donated the source to the university and at that time 
> the activity was known.  Unfortunately, that time is gone and no one 
> knows what the activity is now.  We need to use the source for 
> calibrations, so the activity needs to be accurate.  At one time I 
> had heard that J.L Sheppard and Co. did this type of work, but I 
> don't have their number.  If anyone has any info for them or any 
> other company for this type of work, please let me know.  I thank 
> everyone in advance.

	--It would be very much cheaper to buy or borrow a small
calibrated source and measure the Co-60 gamma ray peak with a NaI
scintillation detector at various distances. This calibrates your
detector, so it can then be used to measure your source. By varying the
distances and counting times, you should be able to overcome the very
large difference in source strength. A small calibrated source should not
cost more than $100.