# Difference between revisions of "PREX/CREX Jul 18, 2018 10:00am"

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## Logistic information

``` BlueJeans calling instructions:
Toll-Free Number (U.S.&  Canada):  888-240-2560
International toll number:         408-740-7256
Bluejeans CODE:                  627 455 790
Bluejeans link: https://bluejeans.com/627455790
Offline room:   CEBAF Center L210A
```

## Agenda

1. Seamus
• Collimator and updated FoMs PDF
• Transport space with CAD from Adam ELOG 3511
• SR: we have re-evaluated what we need for vacuum transport through the septum and to the quads. This defines the inner edge of our acceptance and implicitly our FOM.
• SR: the Q1 collimator has been redone to make sure we get the best FOM and with the most current constraints
• SR: we have allowed ourselves to go to much smaller angles to maximize our statistics.
• SR: I have done some raytracing code to define what is going on in the transport. Adam Z gave me a set of keep out areas at different z locations.
• SR: CREX is the limiting case, considering we use a common collimator for both exp
• SR: this was mostly dues to the energy delivered vs requested
• SR: to maximize the FOM we decided to move the target back 5cm (helps both PREX and CREX). The bellows gives us enough play to move the chamber back. It will not need significantly more design time.
• SR: for CREX we need something more. In particular we made small modifications vacuum enclosure to maximize FOM (based on measurements of the septum).
• SR: for the dilutions we should get some calculations from Chuck on Ca40 and C12.
• SR: Tyler K has done a more detailed analysis (including radiative corrections).
• SR: the original proposal got us to \Delta R/R of 0.12 and we are pretty close with this configuration. KK: what is the nominal “y_inner”? SR: -0.004 m (as per measurements). DM: we should be careful for the linearity of the main detectors.
• SR: for CREX we will miss the mark (because of the change in angle). in the 5 deg documents we quoted 0.007 \Delta R/R which we will be reached with the current configuration.
• SR: for CREX we will need to run the Septum a little higher.
• SR: the Q2 uncertainty is significantly worse for CREX because of the change in angle.
• KK: what are you doing for running time? SR: using PAC days. KK: we should update this using calendar days so we know how much time we have for commissioning.
• KK: is the 5% increase within the magnet acceptable? SR: should be still waiting the g2p running.
• SR: we will followup on the hardware side to make sure we are ok. But the calculations are now finalized.
• DG: how sensitive are you to the precise value of the energy? For example A1n experiment they are discussing increasing .25%. KK: can you check the lower energy maximize FOM? DG: this sets the scale of the beam energy changes that could be made. Will check. BM: 50 MeV is what we specified. KK: 0.25% is about 5MeV so I can’t imagine going down you won’t find a good polarization angle.
2. Collaboration meeting agenda docDB

## Present

Dave G, Ciprian G, Tao Y, Paul K, Seamus R, Amali P, Caryn P, Victoria O, KK, Devi A, Ryan R, Chandan G, Cameron C, Tyler K, Jinlong Z, Dustin M, Juliette M, Bob Michaels,

### Excused

Adam Z, Kent P, Sanghwa P, David A