[Halld-tracking-hw] FDC Prototype Gas leak discussion

[Tim Whitlatch]

Hi Fernando,

Thank you for your comments. All of this will be looked at so the most 
robust design is arrived at that meets the physics requirements. A Test 
plan and report will be written. The tests will not be performed on the 
prototype but a separate test set up will be developed to test any 
configurations before they will be used in production..

Cheers,

       Tim

Fernando J. Barbosa wrote:
> Hi Tim,
>
> I have a few concerns about the re-design to address the gas leaks 
> with foam gaskets. I suggest getting more information on the foam 
> gaskets:
>
> a. material composition
> b. outgassing
> c. adhesive
> d. long term performance with Ar-CO2
> e. radiation "hardness".
>
> Most foam gaskets and contact adhesives loose their properties over 
> time. In particular, most foam gaskets loose their elasticity and 
> crumble, even with closed cell compositions. I am concerned that after 
> 2 years of operation leaks will develop.
>
> Because the FDC is such a complex detector, there is likely room for 
> improvement in several areas and the prototype serves as a good model 
> for further tests and modifications. I know that a number of remedies 
> have been tried. I, however, would like to see a document detailing 
> systematic tests and results with the prototype, i.e. a test report. A 
> lot of effort has been devoted to the nominal design with O-rings over 
> the years and Bill has worked very hard to get it working. I am 
> concerned that we will have a complete re-design of the "sealing" 
> approach before assessing all the risks and root causes of the problem 
> with the prototype.
>
> Best regards,
> Fernando
>
>
> Best regards,
> Fernando
>
>
>
>
> Tim Whitlatch wrote:
>> Hi All,
>>
>> Here are my notes from the discussion of the gas leaks in the FDC 
>> full scale prototype.
>>
>> 1. Causes and potential fixes for the production  packages were 
>> discussed
>> 2. Some known and Possible causes of leaks include leaks through the 
>> rohacel bonding boudaries, deflection of unsupported wireplane pc 
>> board under o-ring, grounding vias on pc board, bond voids on cathode 
>> sandwich, protrusion of traces (3-4 mils) on pc board, not enough 
>> compression on o-ring, too much compression on rohacel, not enough 
>> stifnness in outer channel supports.
>>  
>> Action items
>>
>> a. Develop test plan for testing existing design, slightly changed 
>> design and addition of G10 ring to support bolts and gas seal (Bill 
>> Crahen)
>> b. Get worst case additional material to Simon for background 
>> analysis (Bill Crahen)
>> c. Perform background analysis on increased material (Indiana U?)
>> d. Gather all changes needed for production pc board (Kim Shinault).
>>
>> Cheers,
>>
>>        Tim
>>
>>
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