[Primexd] Target installation plan

[gasparan at jlab.org]

  Dear Justin,

 Thanks for the information: however, any symmetrical pipe inside of the
 FCAL room (or the FCAL) should not give such a asymmetrical Compton
 distribution unless (a) that physical thing is hanging in one side of
 the beam; or (b) either FCal or CCal have some strange asymmetric trigger
 acceptance.

 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.

 Ashot


> Hi PrimEx folks,
>
> At this morning’s RC meeting we discussed the asymmetry observed in the
> compton plots
> https://logbooks.jlab.org/files/2019/02/3660842/61322_ComptonMonitoring.pdf
> (page 2 top left) at length.  There was some concern about material
> shadowing the CompCal, which was visually investigated this morning during
> an access to the Hall.  The conclusion is provided in Matt’s log entry
> https://logbooks.jlab.org/entry/3661206, that the limiting aperture for
> the CompCal is given by the steel pipe in the FCAL dark room, which is
> ~9.4 cm across.  Further analysis of the Be compton data we have may help
> to determine the origin of this asymmetry, but one future suggestion is to
> collect compton data with the CompCal at a few different positions to
> identify how this feature changes (or not) with the detector position.
>
> In any case, the current plan is to run with the empty target (already
> installed) from ~1 pm this afternoon (Thursday) until 6 am tomorrow
> (Friday) morning.  Starting at 6 am on Friday we’ll go into controlled
> access for installation and survey/alignment of the LHe target, which will
> run over the weekend.  If any modification to this plan is required, it
> needs to be decided by the PrimEx spokespeople and agreed to by 4 pm today
> (Thursday), so other groups can plan their work accordingly.
>
> Justin
> Hall D Run Coordinator