Re: CDC upstream end config

["Fernando J. Barbosa" <barbosa@jlab.org>]

Hi Curtis,

Coax cable manufacturers specify the operating voltage between the  
inner conductor and the shield and where the shield is normally at 
ground - most applications. This spec refers to the dielectric between 
the inner conductor and the shield, among other variables. The 
manufacturers also specify the type and dimensions of the jacket 
insulating material which can then be used to determine their usage or 
application.

Regards,
Fernando



Curtis A. Meyer wrote:
> Hi Fernando -
>
>    I know that you have stated that the shield needs to be at HV, but I 
> originally thought this was because the cable you had was not spec'd 
> for high voltage. Are we sure that any cable is really spec'd to have 
> high voltage on the shield? Most manufacturers spec the inner wire 
> relative the the shield and the outside world, but I don't recall seeing
> a spec from the shield to the outside world?
>
>     Curtis
>
> On Mon December 8 2008, Tim Whitlatch wrote:
>   
>> Thank you Fernando for your reply. This would require someone to install 
>> the FEP jacket on all the wire? Is this shrink wrap?
>>
>> Thanks,
>>
>> Tim
>>
>> Fernando J. Barbosa wrote:
>>     
>>> Hi Tim,
>>>
>>> My comments follow:
>>>
>>> Tim Whitlatch wrote:
>>>       
>>>> Hello All,
>>>>
>>>> Per our video conference this morning, the following was discussed;
>>>>
>>>> Gary will continue to manufacture a 24 place upstream plate with 
>>>> proper geometries from "geometry C". this will give room for 
>>>> simulating worst case spacial considerations for assy. He will pursue 
>>>> the original type setup with 5.5 inch long cables max.
>>>>
>>>> As a backup, Gary will manufacture an offset plate with the 24 holes 
>>>> to take the stress off the conductive rubber sleeve (per SLAVA)
>>>>
>>>> Fernando, Gary followed up on the coax cables you suggested. They all 
>>>> seem to come without an outside insulating jacket. Is it possible to 
>>>> use these cables by keeping the braided shield at ground? Also, is it 
>>>> possible to use cable that is not rated for our high voltage by doing 
>>>> some tests?
>>>>         
>>> Of the two suggestions to check the cable routing, one of the coaxes 
>>> should have a jacket but the semi-rigid cable should have an 
>>> aluminized jacket. In this case, an insulating sleeve/jacket needs to 
>>> be installed and there are various types offered by multiple 
>>> companies. I suggest FEP, if available in the required diameter. The 
>>> shield needs to be at HV and in normal operation the potential 
>>> difference between the shield and the inner conductor is zero. 
>>> However, if a straw wire is disabled, the full HV potential will be 
>>> present and the cable needs to conform to these requirements.
>>>
>>> Cables can certainly be tested at higher voltages than the rated 
>>> operating voltage specified by the manufacturer but that's a safety 
>>> issue. I strongly recommend against overlooking the manufacturer's 
>>> safety specifications.
>>>
>>> Regards,
>>> Fernando
>>>
>>>
>>>       
>>>> I will pursue with Tom Carstens from Hall B about connector leaks on 
>>>> their drift chambers.
>>>>
>>>> Yves will look at getting some extension pcbs made for testing 
>>>> Slava's ides per layout on 9-29-08. Can we get a connector made 
>>>> directly onto the HV board that would plug into this?
>>>>
>>>> Thanks for your time,
>>>>
>>>> Tim
>>>>
>>>>
>>>>
>>>>
>>>>         
>
>
>
>   
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