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Reference, Questions and Help => Nuke Q&A => Instrument Q&A => Topic started by: Irradiated1 on Mar 10, 2008, 09:52

Title: Question regarding the calibration of Keithley Ion Chamber (36150)
Post by: Irradiated1 on Mar 10, 2008, 09:52

First off,

I have a 150 mCi Cs-137 Shepard calibration source I'm working with and is normally used to calibrate GM's. However, I've been asked to attempt calibration of our Keithley Ion Chamber model 36150. I want to achieve 1.0 +/- 20% on all three scales.

Can anyone give me some calculations or ideas on the best method to calibrate this ion chamber? This is a basic calbration and not to be held to ANSI standards.

Thanks in advance

Title: Re: Question regarding the calibration of Keithley Ion Chamber (36150)
Post by: Irradiated1 on Mar 12, 2008, 08:20

Well, it seems I have no replies. Does anyone have a copy of the manual for the 31650 they could scan and send me? If you have one send it to cvande2@emory.edu

Anyone know who owns Keithley?

Title: Re: Question regarding the calibration of Keithley Ion Chamber (36150)
Post by: spentfuel on Mar 12, 2008, 12:38

Perhaps no one understands your question.

There is no difference in calibrating a gm or ion chamber to gamma in a shepherd.

Place the detector in the proper geometry and distance at what ever value you know and adjust the meter to read what it should at that distance.

For example I have used a shepherd that I know the table dial setting of 200 give me a dose rate of 250 mr/hr I set the instrument there and adjust as needed.  This calibrates the instrument to gamma only.  From my experience to use it for beta also you need a beta source with a known strength at a known distance.  You take a reading and then determine a beta efficiency and appropriate multiplication factors.

open window-closed window times beta correction factor give you a beta dose rate.

I have never heard of the instrument you mention but I have seen the process I describe used at various nuclear plants.

Hope that helps
sf