Hi Everyone -
I had intended to get this email out earlier today, but have been running
around with my lab class until now. Included are the dimensions of things
that we used in the latest prototype. The straws here are just slightly under
1.6cm OD and are what we have used all along. These dimensions leave
on the order of 150 microns between straws in the layers and are what
the hole patterns are based on (this does both end-plates and at the center).
The other thing that has changed is the hole diameter through the endplate.
It is slightly larger here than before to accomodate the modified "insert
diameter".
It may indeed be possible to shrink the straws a bit and recover the 28.
First estimates are with the OD at 1.55 versus current design. The other
consideration is the donut, but shaving a couple hundred microns off
the OD of the donut should be ok.
Friday at 9:30am works for Yves and I. Gary is away until the end of
next week.
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CDC Information:
The following numbers may be slightly different for earlier numbers for
the CDC. They are based on the material that was used to build the small
prototype chamber. The tubes have always been the numbers quoted below,
these are what we got. But we have been claiming that they were 1.600cm
diamter ( we are 125 microns smaller). The hole through the endplate
changed slightly from before as we had slightly redesigned the donut and
insert to allow for a better glue joint. The hole is now slightly larger
than before.
We would like to spec the straw ID to +1-0 mil, but need to iterate this with
the vendor. The OD has looser specs because of wrapping, thus the 150
micron spacing that we have left.
Straw Tubes: OD = 0.625 inches = 1.5875 cm
ID = 0.615 inches = 1.5672 cm
On all parts below, we have a tolerance of +1-0mil on an OD and -1+0 on an ID.
Donuts: OD = 0.615 inches = 1.5621 cm
ID = 0.437 inches = 1.1100 cm
Inserts: OD = 0.437 inches = 1.1100 cm
ID = 0.250
Pin Holder: OD = 0.250
ID =
Holes in endplate = 0.437 inches = 1.1100 cm
Upstream Endplate 0.375 inch tooling plate = 0.9525 cm thick
Downstream Endplate 0.236 inches = 0.6000 cm thick carbon fiber.
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On Wed February 25 2009, Beni Zihlmann wrote:
> Hi All,
>
> I had some information exchange with Slava this morning. And I realized many
> different parameters and issues regarding the end-plate are not familiar
> to everybody.
> like the following:
> 1) from mechanical tolerances there need to be a "gap" between tubes
> in a given layer of about 0.1mm to 0.15mm depending on the tolerances
> of the tube itself and its parts at the end.
> this is true not just at the end-plate but also at the center of
> the CDC for axial and stereo layers.
> Distances of 20 micro meters between straws is not realistic
> considering that there are no
> numbers available for tolerances of the tube diameter, wall
> thickness, glue joints, etc.
>
> 2) at the same level one could rather change the number of tubes in a
> given layer then changing
> its radius and play with the gap between straws (-> point 1)
>
> 3) there needs to be sufficient spacing after the last straw for the gas
> cover sheet and
> the support rods (about 1.9") as well as the suspension mechanism.
>
> 4) since the straws have to be custom made one could think of make them
> a few micro meters
> smaller in diameter to fit 28 layers in the allocated space.
>
> 5) the holes into the end plate have to be specified with position and
> angle such that a CNC machine
> can be programmed accordingly.
>
> 6) ...other points ??
>
> we really need a meeting to discuss this with all parties involved to
> settle all the issues once and for all.
> If we could meet still this week would be great. How about
> Thursday late afternoon say 4:00pm ?
> or Friday morning say 9:30am ?
>
> cheers,
> Beni
>
>
>
>
>
--
Professor Curtis A. Meyer Department of Physics
Phone: (412) 268-2745 Carnegie Mellon University
Fax: (412) 681-0648 Pittsburgh PA 15213-3890
cmeyer@ernest.phys.cmu.edu http://www.curtismeyer.com/