AW: [ RadSafe ] Optical Couplant

Tue Nov 3 17:35:53 CST 2009

RADSAFErs,

Another case of fundamental lack of very basic understanding: How much Tl is
in such a crystal? What is the LD 50 of Tl? Has ever anybody eaten or at
least tasted a NaI(Tl) crystal? How does it taste? How does the mineral oil
taste and should one also use a little vinegar when eating it? Anybody aware
that NaCl (also called "salt") is deadly if consumed in large amounts? 

This statement reminds me on the infamous statements about the toxicity of
plutonium, polonium, radium and all other radionuclides. "The dose makes the
poison!" - Famous statement of the famous Paracelsus, which is still valid.
(Btw, he is buried in Salzburg in a beautiful romantic graveyard.)

Best regards,

Franz

Franz Schoenhofer, PhD
MinRat i.R.
Habicherg. 31/7
A-1160 Wien/Vienna
AUSTRIA

-----Ursprüngliche Nachricht-----
Von: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] Im Auftrag
von Geo>K0FF
Gesendet: Dienstag, 03. November 2009 20:59
An: AnaLog Services, Inc.; Edmond Baratta; alstonchris at netscape.net
Cc: radsafe at radlab.nl
Betreff: Re: [ RadSafe ] Optical Couplant

It is the Thallium dopant that is so very toxic in the NaI(Tl) crystals.

In the early days, crystals were mounted right on the PMT but immersed in a 
cup of
mineral oil. Today, these 1950's units still work if the oil is intact. Many

of them have leaked though, creating quite a mess.

George Dowell
----- Original Message ----- 
From: "AnaLog Services, Inc." <AnaLog at logwell.com>
To: "Edmond Baratta" <edmond0033 at comcast.net>; <alstonchris at netscape.net>
Cc: <radsafe at radlab.nl>
Sent: Tuesday, October 27, 2009 11:52 PM
Subject: Re: [ RadSafe ] Optical Couplant

> As far as I know, it is rare to have naked crystal material coupled 
> directly to the PMT face.  At least it is rare in my industry.  I have 
> seen it, but only a couple of times.  NaI is quite hygroscopic so dealing 
> with bare crystal material except in a special facility is problematic.  I

> believe NaI is regarded as toxic also.
>
> Heck, we have problems with crystals turning yellow even in the hermetic 
> containers.
>
> Syd H. Levine
> AnaLog Services, Inc.
> Phone:  (270) 276-5671
> Telefax:  (270) 276-5588
> E-mail:  analog at logwell.com
> Web URL:  www.logwell.com
>
> ----- Original Message ----- 
> From: "Edmond Baratta" <edmond0033 at comcast.net>
> To: <syd.levine at mindspring.com>; <alstonchris at netscape.net>
> Cc: <radsafe at radlab.nl>
> Sent: Tuesday, October 27, 2009 8:11 PM
> Subject: Re: [ RadSafe ] Optical Couplant
>
>
>>I believe only the older ones were coupled.  Most of the newer ones are 
>>coupled directly and sealed.  The manufacturers used to supply (sell) the 
>>material to couple the older ones.
>>
>> Ed Baratta
>>
>> edmond0033 at comcast.net
>>
>> --------------------------------------------------
>> From: <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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>>
>>
>
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