[Halld-tracking-hw] CDC Straw Tubes

[Curtis A. Meyer]

Hi Tim -

    as far as we know the old kapton straws have held up. We were just 
concerned that
with all the scratches, a small amount of damage to the straw could 
leave some section
of the straw floating "electrically". Optimally, we would like to 
achieve what Lumina
did with the first straw sample that they sent us. That may not be 
possible, but reducing the
amount scratches woul be very good.

    Quantitatively, it is harder to call. I am concerned that in some of 
the straws, the scrathed
area will "float". While it is good that it is confined to about 25% of 
the surface area, I would
like to see that reduced by about a factor of two (at least).

       -- curtis
On 5/18/10 11:59 AM, Tim Whitlatch wrote:
> I have taken pictures against a back light of the 3 straw samples 
> Curtis gave me. They can be found at;
>
> http://www.jlab.org/Hall-D/software/wiki/index.php/CDC#Straws
>
> I am trying to get a handle on the requirements for the straws. The 
> first shows the Stone aluminized Kapton with a back light. As can be 
> seen, most is transparent and the lines can be seen in the direction 
> of the wrap. The 2nd is the latest Lamina aluminized mylar. There are 
> some lines that are transparent and some scratches.
> The 3rd is the original Lamina aluminized straw from Last fall 
> (supposedly the same material as the new ones) This is completely 
> solid against the back light.
>
> What is the requirement here?
> Had the kapton straws held up over the past couple of years in the 
> prototype setup?
> Is the original Lamina straw acceptable?
> I just wish to be clear before I get with the Lamina rep on this.
>
> Thanks,
>
>       Tim
>
>
> Curtis A. Meyer wrote:
>> Hi Everyone -
>>
>>        we have finished going through the 252 straws that were sent 
>> to us by Lumina.
>> Other than the scratches that we talked about at the meeting last 
>> week, the straws
>> appear to be pretty good. The final numbers on the mechanical 
>> acceptance are:
>>
>>      186/252 straws are good
>>        28/252 straws were rejected because they were oval. Better 
>> packing in the
>>                    shipping box would probably recover all of these. 
>> This would give
>>                    us an acceptance rate of:
>>      214/252  or 84.9%   and we would need 4120 straws to get 3500.
>>
>>      Of the rejected ones,  19 were rejects due to imperfections in 
>> the straws,
>>      wrapping, glueing, extra crud stuck to them, ..... The remaining 
>> 17 were
>>      bowed beyond the 1/10 inch specification. This appears to be in 
>> the straw
>>      and not due to shipping or packing.
>>
>>       In order to improve the regular shipment, the box containing 
>> the straws probably
>>       needs to be compartmentalized so that there are fewer straws 
>> pressing on each other.
>>       Perhaps a wine-crate like structure that has ~ 40 straws in 
>> each compartment???
>>
>>       The overall biggest issue that we saw was the scratches on the 
>> straws. The vendor did
>> not have that on the original samples that we received (a year ago).
>>
>>     Curtis
>>


-- 
Prof. Curtis A. Meyer		Department of Physics
Phone:	(412) 268-2745		Carnegie Mellon University
Fax:	(412) 681-0648		Pittsburgh PA 15213-3890
cmeyer at ernest.phys.cmu.edu	http://www.curtismeyer.com/