[Primexd] Target installation plan

[Justin Stevens]

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