[ RadSafe ] Optical Couplant

[Geo>K0FF]

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
>>>>
>>>>
>>>>
>>>>
>>> _______________________________________________
>>> You are currently subscribed to the RadSafe mailing list
>>>
>>> Before posting a message to RadSafe be sure to have read and understood 
>>> the RadSafe rules. These can be found at: 
>>> http://radlab.nl/radsafe/radsaferules.html
>>>
>>> For information on how to subscribe or unsubscribe and other settings 
>>> visit: http://radlab.nl/radsafe/
>>>
>>> =
>>> _______________________________________________
>>> You are currently subscribed to the RadSafe mailing list
>>>
>>> Before posting a message to RadSafe be sure to have read and understood 
>>> the RadSafe rules. These can be found at: 
>>> http://radlab.nl/radsafe/radsaferules.html
>>>
>>> For information on how to subscribe or unsubscribe and other settings 
>>> visit: http://radlab.nl/radsafe/
>>>
>>
>>
>
> _______________________________________________
> You are currently subscribed to the RadSafe mailing list
>
> Before posting a message to RadSafe be sure to have read and understood 
> the RadSafe rules. These can be found at: 
> http://radlab.nl/radsafe/radsaferules.html
>
> For information on how to subscribe or unsubscribe and other settings 
> visit: http://radlab.nl/radsafe/