Re: fcal test in hall-b

[Elke-Caroline Aschenauer <elke@jlab.org>]

On Fri, 27 Apr 2007, Daniel S. Carman wrote:

Dear Dan,

your point to use this test to justify that using a cathode strip chamber
is at all the correct technology is well taken. And to make things clear I
always thought the test must be done, the only question I have and still
have, is what we learn really fully scalable to the full scale prototype.

I guess what I'm trying to say is that if we see things are workable from
the resolution point of view for the small protoype, we want to redo the
test with the full scale one once more.

The only remaining concern I have with this is do we have really the
manpower to do this tests twice.
Maybe in one of the next fdc meeting, I would like to discuss a longer
range plan for chamber prototype tests.

Cheers elke






>
> Elke,
>
> Your question is a good one and we have been discussing this in
> the group for some time.  I think that we feel that the 200 micron
> resolution goal is going to be extremely demanding from the standpoint
> of design and reconstruction.  At this point, using our small-scale
> prototype, we have direct measurements of all of the main contributions
> to the FDC resolution, with one notable exception.  How will the
> performance of the chambers be degraded when they are in a 2.2T magnetic
> field?  We already know that this contribution to the resolution
> will be the dominant one (by far).  What we do not know, because there is
> very little direct information in the literature, is how much the
> resolution will be degraded as a function of field strength.  We
> have seen some published information (in a cathode chamber with an
> electrode structure quite different from ours) that the chamber
> resolution degraded by a factor of 8 at 2T.  Certainly if this was
> the case, I think we would have to go back to the design drawing
> board and reconsider what we are trying to build.
>
> So the bottom line is that we are extremely concerned about the
> impact of the field and we want to know as soon as possible if our
> current design plans will work.  We do not want to go through the
> design and construction of a full-scale chamber system if we are
> ultimately going to have to come up with an entirely new concept
> or radically change our approach.  In short, the resolution degradation
> of the FDCs in the magnetic field is the single biggest unanswered
> question as we move forward.
>
> With this said, we feel strongly that we want to address this question
> before too much more serious design work proceeds.  The amount of
> manpower to set up the test is minimal, and we have an opportunity
> to really ensure that our design is sound.  It may set us back a month
> or so to spend the time to acquire and analyze the data after we take it,
> but this seems to be a much better option than proceeding with a design
> that we cannot guarantee will meet the tight specifications required
> from this tracking system.  Our deadline for completing the design is
> Oct 2008.  We would be much more comfortable getting this question out
> of the way in 2007 than allowing ourselves to go into 2008 with this
> unknown hanging over us.
>
> Anyway, let me know what you think.
>
>
> 				Regards,
>
> 					Daniel
>
>
> **********************************************************************
> *                                                                    *
> * Dr. Daniel S. Carman                   e-mail : carman@jlab.org    *
> * Staff Scientist                        office : (757)-269-5586     *
> * Jefferson Laboratory                   web: www.jlab.org/~carman   *
> *                                                                    *
> **********************************************************************
>
>
>
>
>

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