Thoughts on material reduction in FDC

[Elton Smith <elton@jlab.org>]

HI Dan,

Here are some thoughts reducing material in FDCs but keeping basic design.

Simon, David and I were discussing ways of reducing the material in the
FDCs, in this case without changing the basic design. We assume we use Cu
for the cathode strips as before, but reduce the number of measurements.

Material in active region

o Reduce planes per package from 6 to 4.
- Argument for six planes comes from improved resolution which was
obtained with the MCFast. This can be checked by David using the updated
geometry and full reconstruction. To the extent that we are
multiple-scattering limited, the resolution should improve even though we
are giving up some position measurements.
- Additional studies need to be performed to check the track finding
efficiency with realistic backgrounds in the counters.
- reduces material in the support rings by the same amount.

o Reduce the number of cathode layers to one per wire plane in 2 of the
four planes.
- This will increase the position resolution in 2 of the four planes by
30%. Again, if m.s. dominates, this should not significantly impact
resolution.
- This will have the added benefit of also reducing the number of spacers
for the rings.

o Eliminate foam from active area of FDC
- This is simply a question as to performance for cathode planes that are
not perfectly flat, or distortions due to stretching them.

Estimated reduction is 4/6 x 0.6 x 6/8 = 0.3.


Material in Beam

Our 30 cm H2 target is 3.3% of a radiation length. Ideally, this should
dominate beam backgrounds, but at the moment the FDC has 4.5% rad length.
Here are some ideas to reduce their thickness:

o eliminate foam in the beam region (no brainer)
o Eliminate Cu strips through the beam area
- This can be used to cut the strips in two and reduce the rate
- Read strips from both sides of the chamber. This could actually be
taken as an advantage as the readout end likely requires more real estate
compared to the HV end. For example, have a prepamp board and grounding on
every other strip.

o Implement pads around the beam hole to carry the highest rate
- Use vias and traces on the back side of cathode sheet to bring out
signal?



Elton Smith
Jefferson Lab MS 12H5
12000 Jefferson Ave
Suite # 16
Newport News, VA 23606
elton@jlab.org
(757) 269-7625

On Tue, 13 Mar 2007, Elke-Caroline Aschenauer wrote:

> On Tue, 13 Mar 2007, Elke-Caroline Aschenauer wrote:
>
> Dear all,
>
> there is 3 more items, which I would like to discuss tomorrow.
>
> 1. summer students
>    ---> I send around some information a while ago,
>         so somebody interessted?
>
> 2. ideas/preparations for the open house @ 21st of april
>
> 3. discussion on comments/recommendations from the chamber review
>    ----> see my mail
> http://www.jlab.org/ccc/mail_archives/HALLD/halld-tracking-hw/CURRENT/msg00105.html
>
> See you all tomorrow
> elke
>
>
>
> > Date: Tue, 13 Mar 2007 15:02:37 -0400 (EDT)
> > From: Elke-Caroline Aschenauer <elke@jlab.org>
> > To: halld-jlab@jlab.org
> > Subject: tomorrows meeting
> >
> >
> > Dear all,
> >
> > as last weeks meeting was canceled due to the detector review we will have
> > again our regular meeting at 8:45 in room F324-F325.
> >
> > I set up a link on the wiki for contributions.
> > http://www.jlab.org/Hall-D/software/wiki/index.php?title=2007-03-14&action=edit
> >
> > Richard will present a summary on all his work on the
> >
> > * Diamond Radiator Development
> >   Tagger readout with SiPMTs and his beam studies.
> >
> > Please put any other plots you intend to present under the link listed
> > above, we will have telephon connection available as usual.
> >
> > regards elke
> >
> > >
> > > To connect by telephone:
> > > 1.) dial:
> > > 800-377-8846 : US
> > > 888-276-7715 : Canada
> > > 302-709-8424 : International
> > >
> > > 2.) enter participant code: 39527048#  (remember the "#")
> >
> >
> >  ( `,_' )+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=
> >   )    `\                                                  -
> >  /    '. |                                                  +
> >  |       `,              Elke-Caroline Aschenauer            =
> >   \,_  `-/                                                    -
> >   ,&&&&&V         Jefferson Lab                                +
> >  ,&&&&&&&&:       HALL-D 12C / F381       121-A Atlantic Avenue =
> > ,&&&&&&&&&&;      Mailstop: 12H5          Hampton, VA 23664      -
> > |  |&&&&&&&;\     12000 Jefferson Ave                             +
> > |  |       :_) _  Newport News, VA 23606  Tel.:  001-757-224-1216  =
> > |  |       ;--' | Mail:  elke@jlab.org    Mobil: 001-757-256-5224   -
> > '--'   `-.--.   |                                                    +
> >    \_    |  |---' Tel.:  001-757-269-5352                             =
> >      `-._\__/     Fax.:  001-757-269-6248                              -
> >             +=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+
> >
>
>  ( `,_' )+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=
>   )    `\                                                  -
>  /    '. |                                                  +
>  |       `,              Elke-Caroline Aschenauer            =
>   \,_  `-/                                                    -
>   ,&&&&&V         Jefferson Lab                                +
>  ,&&&&&&&&:       HALL-D 12C / F381       121-A Atlantic Avenue =
> ,&&&&&&&&&&;      Mailstop: 12H5          Hampton, VA 23664      -
> |  |&&&&&&&;\     12000 Jefferson Ave                             +
> |  |       :_) _  Newport News, VA 23606  Tel.:  001-757-224-1216  =
> |  |       ;--' | Mail:  elke@jlab.org    Mobil: 001-757-256-5224   -
> '--'   `-.--.   |                                                    +
>    \_    |  |---' Tel.:  001-757-269-5352                             =
>      `-._\__/     Fax.:  001-757-269-6248                              -
>             +=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+
>