[Halld-tagger] Fwd: [EXTERNAL] TAGM Move for CPP

Elton Smith elton at jlab.org
Tue Dec 7 08:03:34 EST 2021

Hi Richard et al.,

I am forwarding some emails following our meeting on the microscope move in April to the tagger list  for ease of reference.  The main conclusion was to “adopt the y=0 conversion for specifying the position of the microscope.”  James also provided information and links to information about the microscope at UConn.

Cheers, Elton.

Begin forwarded message:

From: Richard Jones <richard.t.jones at uconn.edu<mailto:richard.t.jones at uconn.edu>>
Subject: Re: [EXTERNAL] TAGM Move for CPP
Date: April 24, 2021 at 7:21:28 AM EDT
To: Elton Smith <elton at jlab.org<mailto:elton at jlab.org>>
Cc: James McIntyre <james.mcintyre at uconn.edu<mailto:james.mcintyre at uconn.edu>>, Timothy Whitlatch <whitey at jlab.org<mailto:whitey at jlab.org>>

Hello All,

I think we should all adopt the y=0 convention for specifying the position of the microscope. That is where it should go unless there are physical obstructions that prevent it from getting closer. I know that at the nominal 9 GeV position there was interference from the massive support pillar for the tagger magnet that gets in the way of pushing the TAGM all the way into the correct position. This should not be the case at the new position, but there may be other obstructions. That's fine, we will deal with them when the time comes. But the correct placement of the scintillator ends is y=0, by design. We should not let offsets that come from support structure interference at the 9 GeV position somehow get adopted as nominal when we move to another position on the focal plane.


On Fri, Apr 23, 2021 at 2:36 PM Elton Smith <elton at jlab.org<mailto:elton at jlab.org>> wrote:

*Message sent from a system outside of UConn.*

Hi James,

Thanks for your summary and the (important) work that you are completing.

I just want to veify that we decided to place the microscope at y=-0.93 cm? I glanced at your extensive documentation and all graphs (probably legacy) all indicate the focal plane. I assume we will have an update at the Beamline meeting on Tuesday and finalize any details.

Thanks!  Elton

Elton Smith
Jefferson Lab MS 12H3
12000 Jefferson Ave STE 4
Newport News, VA 23606

On Apr 21, 2021, at 3:34 PM, James McIntyre <james.mcintyre at uconn.edu<mailto:james.mcintyre at uconn.edu>> wrote:

Hi Elton,

Just a quick update.

- I've reviewed the numbers in your slide show and found that I get the same. The only difference is that I use y(focal plane) = 0 as a reference when discussing most things.

- To alleviate any confusion, I've created a table in my Excel calculations to show the center ([x, y]_fp) of the front-face of the forward bundle half of each fiber bundle. This automatically updates when a new starting energy (highest tagged photon energy) is inputted into the Excel. This will be useful when surveys are conducted.

- I've completed the drawings for the three components needed to adjust the parallel railing system for a move to tag 6.2 - 4.7 GeV photons. This setup utilizes only 16 of 17 possible (5x6) fiber bundles due to the limitation imposed by the small beta angle and parallel railing length, as discussed at the last meeting. This will not cause any issues.

- I've gotten a quote from our usual vendor for the new components needed for the move, and it is with Richard.

- Our wiki has permanent links to design CAD files and the spreadsheet needed for the move. Here are the links to the wiki pages:

- I will be training Daniel (Richard's new grad student) so that he will be well prepared when it's time to perform the move.

- A few design concepts have been presented to our group with regards to fixing the issue of fibers pushing the darkening shroud up into the TAGH. All of these are simple fixes that can be quickly implemented. I will continue to work with Richard on this fix.

I will continue to work with Daniel on move preparations. Please let me know if you need anything else.


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