[ RadSafe ] Optical Couplant (UNCLASSIFIED)

[Forsee, Gary]

Hello all,

The following is simply my thought on the matter and I welcome your
insight / criticism:  

Knoll addresses the topic of optical couplants on page 249 of Radiation
Detection and Measurement (3rd ed.).  "...total internal
reflection...must be minimized at the surface from which the
scintillator is viewed to prevent internal trapping of the light.
Ideally one would like to optically couple the scintillator to the
photocathode of the PM tube through a transparent medium of the same
index of refraction as the scinitillator.  Then [the critical angle =
sin-1 n1/n0], would predict no internal reflection and all light
incident on the surface would be conducted into the glass window of the
PM tube on which the photocathode is deposited."

In short, by comparison of the indices of refraction between that of air
and that of the optical couplant, a correlation can be derived to the
loss in photon collection efficiency (due to increased internal
reflection or likelihood of critical angle due to small differences in
density between mediums).  Snell's law would give a quantitative number
for the changes in using different optical couplants....or no couplant
at all.


Gary Forsee
IEMA

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of Falo, Gerald A Dr CIV USA MEDCOM CHPPM
Sent: Wednesday, October 28, 2009 8:20 AM
To: syd.levine at mindspring.com
Cc: radsafe at radlab.nl
Subject: RE: [ RadSafe ] Optical Couplant (UNCLASSIFIED)

Classification:  UNCLASSIFIED 
Caveats: NONE

Syd,

There is some information in Techniques for Nuclear and Particle Physics
Experiments - A How-to Approach" by W.R. Leo. I have a 1987 edition, but
there might be a newer edition with more information.

Specifically, chapter 9 covers "Scintillation Detector Mounting and
Operation."  The references for this chapter date between 1952 and 1979,
so the information might be out of date.  There is one section (section
9.2) on "Coupling to the PM<" but there're no data nor references  in
the section.

I don't if this helps, but here it is.

Jerry

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of alstonchris at netscape.net
Sent: Tuesday, October 27, 2009 6:10 PM
To: syd.levine at mindspring.com
Cc: radsafe at radlab.nl
Subject: Re: [ RadSafe ] Optical Couplant


Syd

Is there nothing in Knoll (Radiation Detect and Measure) that's useful
on this subject?  Also, e.g., research-grade NaI crystals are mated
directly to the PMT, no?

Cheers 
cja


-----Original Message-----
From: Syd H. Levine <syd.levine at mindspring.com>
To: J. Marshall Reber <jmarshall.reber at comcast.net>
Cc: radsafe at radlab.nl
Sent: Sat, Oct 17, 2009 10:16 pm
Subject: Re: [ RadSafe ] Optical Couplant


I looked for something, even qualitative, and could not find anything
interesting. I found some stuff related to fiber optics that surprised
me (not as big an improvement as I expected), but I do not know how that
applies to scintillation detectors. I do not *think* a scintillation
detector will work at all without coupling compound. 
 
Syd 
 
----- Original Message ----- From: "J. Marshall Reber"
<jmarshall.reber at comcast.net> 
To: "Syd H. Levine" <syd.levine at mindspring.com> 
Cc: <radsafe at radlab.nl> 
Sent: Saturday, October 17, 2009 3:48 PM 
Subject: Re: [ RadSafe ] Optical Couplant 
 
> 
> On Oct 17, 2009, at 4:21 PM, Syd H. Levine wrote: 
> 
>> I finally got around to writing a page about optical coupling
compounds: 
>> http://www.logwell.com/tech/servtips/optical_coupling_grease.html 
>> 
>> Comments or criticisms needed and much appreciated. 
> 
> It would be useful to quote in quantitative terms the actual light >
transmission improvement of using the coupling compounds. 
> 
> Unfortunately I am unaware of such data. 
> 
> J. Marshall Reber, ScD 
> 165 Berkeley St. 
> Methuen MA 01844 
> 
> Tel/Fax: 978-683-6540 
> Alternate Email: reber at alum.mit.edu 
> 
> 
> 
>  
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Classification:  UNCLASSIFIED 
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