[Halld-tagger] [EXTERNAL] photon beam working group

[Richard Jones]

Hello Elton,

The only radiator we have that is thinner than 50 microns is the 20 micron
crystal that was heavily used and radiation damaged back in 2018. But we do
have a 50 micron diamond that is type III (electronic grade). That is the
one I was speaking of. We don't know for sure how much better it will be
than our standard type II cvd crystals from E6, but we hope it will be
substantially better. We plan to take it to CLS in December and take
rocking curve scans to find out.

-Richard Jones

On Wed, Nov 24, 2021 at 7:54 AM Elton Smith <elton at jlab.org> wrote:

> *Message sent from a system outside of UConn.*
>
> Hi Richard,
>
> Thanks for the summary.
>
> For the CPP experiment, I believe you had proposed using a thin diamond (<
> 50 um), so the we could run at higher beam current. Is this still the plan
> and which diamond are you suggesting? Are you planning to characterize it
> during the upcoming run at Saskatoon?
>
> Thanks, Elton.
>
> ------------------------------------
> Elton Smith
> Jefferson Lab MS 12H3
> 12000 Jefferson Ave STE 4
> Newport News, VA 23606
> (757)269-7625
>
> On Nov 23, 2021, at 9:20 AM, Richard Jones <richard.t.jones at uconn.edu>
> wrote:
>
> Today would be the regular biweekly meeting of the Photon Beam working
> group, but I think we can substitute the meeting today with the following
> summary.
>
>    - Mike Dugger continues to work through an issue with slow file
>    transfers between Jefferson Lab and his server at ASU. Last week he and I
>    sat for a work session to study this issue, and we found the issue is
>    larger than just the specific endpoints in question. We found that transfer
>    rates between centrally managed data transfer nodes at ASU and similar
>    endpoints at UConn also showed the same bottleneck, limiting throughput to
>    the range 5-10 MB / s using high-performance tools like globus online and
>    perfsonar. At the same time, I was seeing rates > 500 MB/s from Jefferson
>    Lab to UConn. This seems to be a recent phenomenon because Mike has done
>    transfers in the past using commandline tools and seen much better rates.
>    Mike is reaching out to ASU network experts to try and find out what is
>    going on.
>
>
>    - Andrew Schick has been occupied on a number of fronts, in
>    preparation for the upcoming CPP run, but he continues to move forward with
>    systematics studies of the analyzing power from his BH analysis. Since the
>    last meeting, I generated new samples of muon pairs to complement the
>    existing e+e- samples, and compare with the UMass generator for both 2H and
>    208Pb targets. These samples have been reduced (accept/reject, energy,
>    angle cuts) and transferred to Jlab where Andrew has begun to process them
>    through his simulation and analysis pipeline. Problems with the use of
>    MCwrapper for these studies with the UConn generator were explained as due
>    to the use of too old a version of hdgeant4. Andrew has yet to confirm that
>    he is able to run his entire analysis through MCwrapper for both
>    generators, by selecting a newer tagged version of hdgeant4, but I claim
>    that this should be the case.
>
>
>    - Early on in the SRC run, we have seen contradictory results between
>    the projected photon beam focal spot at the collimator based on
>    extrapolation from the harps and the measured transmission through the
>    collimator. As soon as the run is over, we should have a discussion on what
>    might be the cause of this, and how to improve our ability to determine the
>    photon beam phase space distribution, so that we can reliably predict how
>    changes in the beam tune are related to transmission through the collimator.
>
>
>    - Plans are being finalized for a run in mid-December at the Saskatoon
>    CLS to measure the crystal quality of the 3 new diamond samples obtained in
>    2020 from Element Six.
>
>
> -Richard Jones
>
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