Re: Build-up Cap

["Mike Bohan" <mike.bohan@yale.edu>]

        Reply to:   RE>Build-up Cap 

Travis,

A "build-up cap" is not needed for most health physics measurements because it
is generally only needed in radiation fields above 1 MeV in energy.  The cap
is used to provide the electron equilibrium which would be present in tissue. 
This is an important issue in the therapeutic use of radiation and is a topic
covered in most radiation therapy references. 

I would recommend the following references:

"The Physics of Radiation Therapy", Faiz M. Khan, 2nd Ed. (1994), pgs. 137-140

"The Physics of Radiology", H.E. Johns & J.R. Cunningham, 4th Ed. (1983), pgs.
239, 255, & 311

Happy Holidays! 

<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><
Michael J. Bohan, RSO   |  e-mail: mike.bohan@yale.edu
Yale-New Haven Hospital |    Tele: (203) 785-2950
Radiological Physics    |     FAX: (203) 737-4252
20 York St. - WWW 204   |    As usual, everything I say may be plausibly
New Haven, CT    06504  |    denied at my employer's convenience ...
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--------------------------------------
Date: 26/12/96 12:55 PM
To: Mike Bohan
From: radsafe@romulus.ehs.uiuc.edu
One of the questions on the 1996 Part II ABHP exam asked for the purpose
of a "build-up cap" on an ion chamber.  I have looked in several texts
(Cember, Knoll, Price) but cannot find reference to the cap.  Can anyone
help?

Travis N. Beard
Corp. H.P.
Northern States Power Co.
brdt07@nspco.com
612-337-2018