Wednesday, March 30, 10:00 AM EDT

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  1. General goals for this "supergroup" (Mark/KK)
  2. Beam monitoring (Mark)
    1. Background material Beam monitoring info
    2. Beam size monitor with cavities (Mike Woods, SLAC, KK mentioned this)
    3. Beam monitor parasitic development work (KK potentially has graduate student available for this)
    4. Synchrotron radiation - any issues here?
    5. R&D plan needs to focus primarily on charge monitoring - how to proceed? (ie. parasitic work in Hall A or C or both? Qweak may be resistant to changes since things are working at an acceptable level now, but that is not confirmed.)
  3. Tracking (Mark, David A.)
    1. Background: Director's Review Tracking Talk (see slides 4,8,9,10,12) Tracking background info
    2. Background: Initial CAD layout from Dec. 2010 KK talk Tracking CAD info
    3. Background: Small acceptance pion counting detector from Souder Dec. 2010 talk Souder pion detector info
    4. Are we happy with decision to just measure scattered theta and not E'?
    5. Can initial work proceed without further simulations (other than default profiles of the scattered flux at the three z locations in the most current spectrometer design)?
    6. What work needs to be done by summer? (suggestions:)
      1. further "Roman pot" research
      2. finalize decision for "Region 3" technology - straws or GEMs?
      3. Learn more about running GEMs in vacuum (assuming that is default choice for Region 1 and 2)
      4. Number/sizes of detectors in each region
      5. Is this the correct subgroup for Souder's counting mode pion detector?
  4. Integrating detectors (Mark, Michael, Dave M.)
    1. Background: Director's Review Integrating Detectors Talk (see slides 2,3,18,19,27,31) Integrating Detectors info
    2. Background: Initial CAD layout from Dec. 2010 KK talk Detectors CAD info
    3. Can initial work proceed without further simulations (other than default profiles of the scattered flux at the focal plane in the most current spectrometer design)?
    4. Stand-alone GEANT4 light transport simulations for some default radiator/air lightguide combinations will probably be useful.
    5. PMT diameter, Winston cones? (KK can comment)
    6. Pion detector ideas (KK)
    7. Ideas for coupling others into UMass Solidworks CAD design for detector/supports
  5. Next meeting time/goals
    1. Mark Pitt will establish three separate JLAB mailing lists (for beam monitoring, tracking detectors, integrating detectors), since some sub-group discussions may become too detailed for general consumption. This is also a way to self-organize and find out who might be available to contribute.
    2. For next meeting, a good goal would be for each subgroup leader to establish communications with his sub-group via email, prepare a list of goals for mid-summer, determine what tools (CAD, simulation, etc.) are needed to proceed, and have an initial list of volunteers to work on the topics.
    3. Perhaps we need 3 weeks till we can do this next supergroup meeting (week of April 18-22)?
    4. After that, how does meeting every 3 weeks for the supergroup sound? Subgroups can meet as they see fit in between time (email exchanges, teleconferences, etc.)


Participants: Dave Mack, David Armstrong, Jay Benesch, Dustin McNulty, Paul King, Julie Roche, Nilanga Liyanage, Krishna Kumar, Abdellah Ahmidouch, Wouter Deconinck, Kent Paschke, Michael Gericke, Sam Danagoulian

Minutes prepared by Mark Pitt; these are my best attempt at capturing the variety of ideas and questions brought up on the call. Hopefully this can serve as a reminder list of items that need further discussions in the subgroups.

  1. Beam monitoring
    • Mark Pitt and Dave Mack describe the Qweak experience with BCM resolution; best observed so far ~ 75 ppm @ 960 Hz @ 165 uA (from 4/20/20110, but sometimes is much larger for as yet unknown reasons; Dave Mack's tests with RF signal generator give ~ 15 ppm; the real beam has more amplitude modulation, though
    • Local oscillator noise: it was pointed out that (in contrast to some systems) each of the BCM's has its own local oscillator
    • KK mentions that the local oscillator noise was a major issue for E158 BCM's; Yury K. is the expert who kept track of that
    • Somebody raised a question about temperature control; (minute taker can't recall the answer, but I know the BCMs in question do have pretty good temperature control/regulation, so this is likely not the cause of the Qweak issues)
    • KK mentions that after the 12 GeV upgrade it should be possible to do commissioning of any upgraded beamline hardware we develop in running to the Hall A dump; such work could be incorporated as DOE CD2 or CD3 tasks
    • The issue of monitoring helicity-correlated beam size with higher mode microwave cavities was discussed. Dave Mack's Qweak tech note involving three cavity monitors was discussed briefly. Paschke said he thought the idea required rastered beam, and the size modulation we were looking for might not be detectable. The issue was left unresolved and needs further discussion in the sub-group.
    • There was some discussion led by KK on the desired number of charge monitors; my notes here were a bit garbled - 2 pairs was certainly mentioned plus two more well upstream; I also had written "total of eight", so not sure where that comes from...
    • Possible R&D activity (suggested by KK I think): Develop position sensitive cavities at "superlow" currents (resolution of 1 mm @ 50 nA was mentioned, but that may be what has already been seen in Hall A when trying this with special Musson electronics; need to follow up on this)
    • Paul King inquired about the possibility of a wire array for monitoring helicity-correlated size; KK said E158 had used such a system and about 1/5 of the data was taken with it in place
    • KK mentioned that beamline element commissioning with full parity DAQ could in principle happen during PREXII if it occurs early in the 12 GeV era
    • The possibility of a synchrotron light monitor for energy was discussed briefly, but my notes were a bit garbled
    • KK asked Kent whether it might be useful to try the Hall A BCM electronics at 1 kHz
    • Jay Benesch pointed out that the current design has only 5.5 m from the end of the fast raster to the Moller target; perhaps 2 additional meters could be squeezed out by reconfiguring the Compton
    • The fact there is only 5.5 m led to discussion of: what angular resolution do we need?, can one set of BPMs be upstream of the fast raster?, etc. --> bottom line is the beam monitor subgroup needs to think through the implications of this 5.5 m carefully
    • David Armstrong pointed out that Qweak should also look at double differences of stripline 4-wire sums (as well as the cavity BCMs) as an additional diagnostic in understanding the behavior of the BCM double differences
    • KK asked if Qweak had looked at the BCM double differences at 30 Hz to compare to our existing experience; answer: no, but in principle we can get it from existing Qweak data by combining events (since then Kent's student Emmanouil Kargiantoulakis has indicated this is possible)
    • Sam D. mentioned an earlier idea for a beam profile monitor using residual gas; KK suggests this sub-group put in the numbers and see if the proposed device would meet our requirements Beam profile monitor document
  2. Tracking
    • In response to questions, David Armstrong points out that nearly the entire azimuth is active for the tracking detectors, and there is the potential for interference of the GEM read-out electronics in the next octant. Nilanga pointed out that the super-Big-Bite has read-out cards bent by 90 degrees, so that could alleviate this issue somewhat.
    • Pion detector: KK is working on a full 3D concept that he will discuss more at the next meeting.
    • In response to the question: "Are we happy with just measuring scattered theta and not E'?", KK says that some members of the Prescott committee had recommended the idea of a portable calorimeter and said such things exist; this subgroup should explore this possibility.
    • GEMS vs. straws in "Region 3" with the largest active area was discussed. Nilanga points out that the cost of GEMs has come down, so it may be feasible to do GEMs in Region 3.
    • David Armstrong raised the question of triggering for the tracking system; it was suggested that perhaps the sandwich detector behind the main quartz could be a trigger, but that doesn't exist for the e-p region; the other suggestion was perhaps just large scintillators behind the last set of trackers--> Clearly, this will be an important issue for the tracking subgroup to deal with.
    • Dave Mack suggests that a possible technology for region 3 might be MWPC with small wire pitch (depending on what resolution we really need in Region 3)
    • David Armstrong indicated that in the short term, he would have discussions with Nilanga to get an initial sense of the possibilities for GEMs (costs, number needed to cover the active area, etc.)
  3. Integrating detectors
    • In general, KK answered questions about some existing U. Mass CAD design diagrams that were posted for the meeting (further details about that will be presented at the April 22, 2011 meeting.
    • Generally speaking, the goal of the integrating detectors group is to consider the tradeoffs and optimize the size and number of channels of the integrating detectors.
    • Sam D. asks a specific question about whether it is necessary to polish the quartz on all sides (more expensive) or is it possible to just polish the side coupled to the air lightguide while painting the other sides with aluminum paint. This is an example of an issue that this sub-group should consider.
  4. Next meeting
    • Tentatively, we will schedule the next meeting in the April 21-22 timeframe.

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