[Primexd] [GlueX] Target installation plan

[Shepherd, Matthew]

(Removing GlueX Collaboration from the cc so we don't keep flooding people with email.)

Hi Ilya,

I don't think anything can be learned from the pictures regarding alignment with beam line as the camera is also not directly aligned with the beam line.  Picture can be used to get an idea of what the pipe looks like, but location must be determined from survey.

Tim or our engineer at IU can provide drawings, but best would be simply to go measure the the pipe yourself.  Then you know for sure.  We were rushed today and just had a standard tape with 1/8" increments, hence my number of 3 11/16".  My expectation based on block size and material dimensions is that the number should be 3.74".

Regarding alignment on the beam axis:  the FCAL is stacked against a fixed side.  A row of blocks is placed and then put horizontally under compression against a side and then clamped.  It means the location of the beam pipe is best defined with respect to this fixed side (the south side, I think).  However, after stacking survey was done to determine the location of the beam pipe and that data was incorporated into the GlueX model to position the FCAL as the beam pipe is the best measure of the location of the detector as we care about it even though it isn't rigidly attached o the frame.  You may want to get the survey data yourself.  I see Simon's note of a 5 mm offset in x.  Whatever the shift is, we seem to know what it is, because data shows good agreement between cluster position and extrapolated tracks to my knowledge.  I think a mistake at the 2 cm level would probably stand out.

Matt

---------------------------------------------------------------------
Matthew Shepherd, Professor
Department of Physics, Indiana University, Swain West 265
727 East Third Street, Bloomington, IN 47405

Office Phone:  +1 812 856 5808

> On Feb 28, 2019, at 2:58 PM, Ilya Larin <ilarin at jlab.org> wrote:
> 
> 
> Hi Matt,
> 
> according to the pictures the square pipe is asymmetrical vs beam line
> and is most likely causing the "shade" on ComCal face.
> Wondering if  FCAL is placed symmetrically vs beam,
> that should mean that pipe doesn't exactly match FCAL hole.
> The exact values from drawings would help and needed for MC
> geometry db to get an exact acceptance.
> If it is the case, that only mean we have to reduce ComCal
> fiducial region for Compton events.
> 
> Thanks for pictures.
> 
> Ilya
> 
> 
> 
> От: GlueX-Collaboration <gluex-collaboration-bounces at jlab.org> от имени Shepherd, Matthew <mashephe at indiana.edu>
> Отправлено: 28 февраля 2019 г. 12:49
> Кому: Ashot Gasparian
> Копия: primexd at jlab.org; andrsmit at jlab.org; GlueX Collaboration; Mark Stevens
> Тема: Re: [GlueX] Target installation plan
> 
> 
> Hi Ashot,
> 
>> On Feb 28, 2019, at 11:58 AM, gasparan at jlab.org wrote:
> 
>> Therefore, it would be extremely important to take pictures of the FCAL
>> insertion part and post on some place to see, before our meeting this
>> evening.
> 
> 
> I've posted pictures of the FCAL insert here:
> 
> https://logbooks.jlab.org/entry/3661206
> 
> It looked today exactly as it did 5+ years ago when these were taken.  (I'm surprised you haven't taken a peek at it before as it defines the acceptance of your detector.)
> 
> The Plexiglas monitoring system is held in the groove on the upstream end.  Anything of any density should be clear of the inner opening in the tube.  From the darkroom all that is visible is what appears to be a thin tedlar cover on the upstream end.  It is needed for a light seal or else there is light path from the hall into the darkroom via the beam pipe.
> 
> Matt
> 
> ---------------------------------------------------------------------
> Matthew Shepherd, Professor
> Department of Physics, Indiana University, Swain West 265
> 727 East Third Street, Bloomington, IN 47405
> 
> Office Phone:  +1 812 856 5808

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