July 6, 2006

From GlueXWiki
Jump to: navigation, search

Summary of meeting with Hall B Engineering staff concerning the BCAL test beamline:

- Platform and alcove available to us any time after 15-Aug (Doug).

- We told Dave Kashy we need one day to uncrate, prepare, and then rig into the alcove (Eric). Then we will set up to take cosmics for at least two weeks (Zisis).

- H-B will arrange for surveying marks on floor and wall (Dave). Eric will verify this is acceptable.

- We said we do NOT need any H-B technician time (Eric). Dave and Doug have have arranged for machine tool access by Eric, who has required training, etc.

- There should be no interference between the BCAL and railings (Eric). Railing top is at 42", beam is at 59" (Doug).

- H-B staff will mount veto counter (supplied by Elton) and Primex photon profiler (David L) on stand at upstream end of platform (Dave). Eric will verify there is no interference between these and the BCAL/cart.

- The 2.6 mm collimator is acceptable (Matt, Elton, etc). 2.6 mm spot is 1.9 cm at BCAL. Matt and Elton agree timing measurements will be acceptable with this spot size.

- H-B suggested extending the plate into the alcove to give a level surface for the cart (Doug, Dave). Eric will send them the cart footprint so the plate size can be determined.

- No instrumentation will be added to the Pair Spectrometer...it will be used as a cleanup sweeping magnet only (Zisis).

- For TPE there will be additional radiators. We have a choice of 10**-4, 10**-5, others (Dave). Standard for us is 1 nA on 10**-4 radiator (Elton).

Next meeting Thurs 13-Jul 11am.




Below is Franz's note on beamline requirements:

What we need is essentially the photon beamline installed:

- standard tagger radiators + tagger harp, - tagger monitoring via epics scalers (or do we need tagger information per event: then pipeline TDCs <=coda)

- collimator box with active collimator and 2.6mm passive collimator),

- sweepy magnets,

- photon harp+Primex magnet,

- beam-halo counters (4 PMTs around beampipe downstream of Primex magnet),

- probably fiber beam pipe into CLAS and He-bag downstream of CLAS (Dave should decide whether it all can be a long He-bag),

- photon profile monitor (scint.fiber arrays) is in front of electron dump downstream of alcove); if there is enough space at the entrance to the alcove, the Primex beam profile monitor should be installed there (I don't know where it is now!).


"Clean-up collimator" really don't make sense: they produce more background than do cleaning (except there is a sweepy behind it).

Whether the Primex spectrometer should be installed and running, depends upon whether we want to extend the test to a measurement of absolute efficiencies (requires TDC-readout <=coda).

The active collimator has a 2mm bore, if a 1mm bore is needed, we've to stack the sheath with those discs.

Positioning of collimator and photon beam will be done via harp scans at goniometer (2C21 harp) and radiator position (tagger harp) and at Primex target position (photon harp=2H00 harp). We can use the gamma profile monitor at its nominal position to get an information about beam spot position and size, then put the BCAL module in place.