[Halld-tagger] Fixed array counters - corrected

[Alexander Somov]

I would position all counters from the same side (above),
it will be more convenient to allign them as well. We'll
need to place cnt75-143 in two (?) rows.

Cheers,
        Alex


On Tue, 11 Sep 2012, Richard Jones wrote:

> Dan and all,
>
> When you mount the fixed array counters, do you foresee them hanging down 
> from above (like stactites), or sticking up from below (like stalagmites)? 
> It might be more convenient from the point of view of cabling to have them 
> above.  It would also help prevent collisions with the microscope, whose 
> fiber readout is under the focal plane.  We are working on a scheme for 
> shaping the ends of the box to allow fixed array access to the focal plane 
> immediately below and above the microscope coverage.
>
> -Richard J.
>
>
> On 9/11/2012 4:57 PM, Alexander Somov wrote:
>> Dear Dan, all,
>> 
>> I think that the hodoscope rate in the microscope
>> region is reasonable. I would go with a 4 mm counter
>> size. The groups of counters also look good for me.
>> 
>> I would require counters to overlap slightly in the
>> close-packed region to avoid any acceptance gaps.
>> 
>> How should we proceed with the counter location with
>> respect to the focal plane ? Once we decide on this,
>> we can ask Tim to prepare technical drawing for the
>> mounting structure. Tim said that they may need
>> about 1-2 extra cm if we decide to place counters at the
>> focal plane
>> 
>> We also need a few counters to cover the acceptance
>> gap between the microscope scint. and the side plate of
>> the microscope box.
>> 
>> Dan, are you going to make some drawings for light guides ?
>> I would use (straight) fish-tail light guides for
>> all counters. For small counters (cnt22 + with R<20mm)
>> we can just use a cylinder as a light guide. It would make
>> sense to couple the light guides with PMTs in the same
>> way.
>> 
>> I would make the light guide about 5-6 inches long.
>> The fringe field for end-pont counters is below
>> 70 - 80 Gauss for both Bx and By at Y = 20 cm
>> (and drops rapidly with Y).
>> 
>> 
>> Thanks,
>>          Alex
>> 
>> 
>> 
>> On Tue, 7 Aug 2012, Daniel Sober wrote:
>> 
>>> The previous mail, and Point 3 of the file attached to it, did not say 
>>> quite
>>> what I meant to.  Please look at the new pdf file instead.
>>> 
>>> Here's my current best set of counters, with an explanation of the 
>>> criteria
>>> used.  Please look especially at point 3.  The important feature is that 
>>> the
>>> high-Egamma part of the hodoscope be able to run at GlueX rates.  I have 
>>> set
>>> it up so that the counters closest to the Microscope are 4 mm wide, 
>>> compared
>>> to the 2 mm Microscope fibers.  Thus no counter in this region counts 
>>> faster
>>> than twice the incoherent contribution in a microscope column.  Since the
>>> microscope rate will be limited by the coherent peak, where the total flux 
>>> is
>>> ~twice as large, the maximum hodoscope counter rates will be ~ same as
>>> Microscope column rate. Is this reasonable?  If not, I can easily re-do 
>>> the
>>> calculation with a different rate limit.
>>> Dan
>>> -- 
>>> /Daniel Sober
>>> Professor
>>> Physics Department
>>> The Catholic University of America
>>> Washington, DC 20064
>>> Phone: (202) 319-5856, -5315
>>> E-mail: sober at cua.edu/
>>> 
>
>
>