Re: CDC configuration

[Beni Zihlmann <zihlmann@jlab.org>]

Hi All,
 so from what I see Friday 27th at 9:30 we will have this meeting.
I will organize a room hopefully with esnet.

cheers,
Beni
>
> 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.
>
>     * - curtis
>
> -------------------------------------------------------------------------------------------
>
> 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.
>
> ---------------------------------------------------------------------------------------------
>
> 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/
>


-- 
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Benedikt Zihlmann
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