Re: GM response to neutrons?

[Ted de Castro <tdc@XRAYTED.COM>]

Why stop at Indium - Ag wrap will give a HUGE response.  A common

practice years ago and still not unusual today around pulsed

accelerators with sub microsecond pulses and million to one duty

cycles.  Of course rejecting area gamma fields is a problem.



Its called the Albatross.



John Andrews wrote:

> 

> You can get some sensitivity to neutrons from GM tubes by wraping them

> with Indium foil.  This will become radioactive from thermal neutrons

> and decay fairly quickly.  The response will therefore be smoothed out

> and it will not be prompt as with a GM in a gamma or beta field.  We put

> indium foil around the GM detectors in chirpers used in our accelerator

> facility in the mid 60's.  They worked.

> 

> John Andrews

> Knoxville, Tennessee

> 

> Phil Hypes wrote:

> 

> > Based on the times I've played around with GM counters and neutron

> > sources, I'd guess you were responding to the Am gammas.  Of course,

> > there are AmBe sources that are shielded to prevent gamma exposure, so

> > if that was the case you were either detecting higher energy gammas

> > from the Am, or you were in fact detecting neutrons.  My guess would

> > be gammas.  You really need H3 tubes to get any kind of decent neutron

> > response in gas filled detectors.

> >

> > Phil Hypes

> > Los Alamos Radiation Consultants

> > laradcon@hotmail.com

> > 505.920.9712

> >

> >

> >

> >

> >

> >> From: Kai Kaletsch <eic@shaw.ca>

> >> Reply-To: Kai Kaletsch <eic@shaw.ca>

> >> To: RadSafe <radsafe@list.vanderbilt.edu>

> >> Subject: GM response to neutrons?

> >> Date: Wed, 29 Jan 2003 13:39:09 -0600

> >>

> >> Friends,

> >>

> >> could someone educate me about the response of GM tube based

> >> instruments to neutrons?

> >>

> >> I remember playing with Am/Be neutron generators and using a GM based

> >> meter to confirm that the source actually got back in the holder.

> >> (And the regulators where OK with us only having GM based detectors

> >> on hand to locate a possibly lost source. [They did want the

> >> operators to be badged with neutron dosimeters.])

> >>

> >> So, the question is: Was the detector seeing some interaction of the

> >> neutrons, or was it only seeing Am gamma?

> >>

> >> Thanks in advance,

> >> Kai

> >> http://www.eic.nu

> >> http://www.gammawatch.com/

> >

> >

> >

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