Minutes 7-11-2007
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FDC Weekly Meeting
Date: July 11, 2007
Participants: Daniel, Simon, Brian, Kim, Tim, Chuck, Fernando, Joe
Next Meeting: July 18, 2007
Contents
Cathode Updates
- Brian has not yet heard back from Sierra regarding whether or not they can make our cathode planes. We are now assuming that they will say no. Brian will move to contact CCT Marketing to give them the go ahead on the $14k tooling costs and have them make our boards for the small-scale prototype with 2-um copper on 1-mil Kapton backing. We felt this was important to complete so that these boards are ready for testing in the B-field test coming up next month.
Frames
- Calculations provided by Tim modeling the loaded wire frame with a single (central) wire carrying the full force load, indicated that the shearing force on the end of the frame would lead to failure. He determined that we would be far from any failure point if the composite was made with high density Rohacell instead of low-density Rohacell. - Brian will check these calculations with a potentially destructive test of his existing composite wire frame. He has already ordered the necessary high density Rohacell foam and will make another composite wire frame when this arrives. This new version will have the nominal wire frame dimensions that is 5-mm thick overall. - We also decided that we should move to replace the CH2 spacers with this same composite design. These frames will be much easier to handle than the CH2. - Brian's main worry is that the o-ring groove will fail. That is to say, the spacer needs to have an o-ring groove machined into it on one side. The depth of this groove is more than the 1/32-in thickness of the G10. The plan was to machine in this groove and then to seal it with epoxy. Brian's worry is that any flexing of the frame could cause the seal to crack. He will test this on a prototype frame shortly.
Cathode Boards
- Even though we have not reached a final decision with regard to backing or no-backing of the cathode boards, we all feel that the evidence and test results are indicating that a non-backed cathode simply cannot meet our flatness specifications in the environment inside the magnet. We have discussed a number of options for including a backing structure that still aims to reduce the thickness in the active area. To this end, Brian has ordered some 2-mm thick low density Rohacell that we will use as the backing in our next cathode prototype.
Magnetic Field Tests
- DSC has finalized a loan agreement with IUCF to borrow 8 drift chambers to be used to define the external track through the magnet and the small-scale prototype. These horizontal drift chambers have a half-gap of roughly 5 mm and an area of roughly 45 x 25 cm**2. They should arrive at JLab before the end of next week. DSC and Simon will work out a plan to recondition these chambers which have not been used in about 15 years. In fact DSC built these chambers at IUCF for his thesis experiment! Once calibrated, these chambers should provide a measurement of the track at the location of the small-scale prototype of roughly 200 um. - Simon will work with DSC to come up with a list of components that we need for the test and then work to dig up any missing cables. We will also finalize the test plan for the measurements. - Simon will do some measurements in Hall B to find out exactly what the space requirements are. We would like to put 4 chambers and one trigger scintillator above the magnet and an identical set of chambers and trigger scintillator below the magnet. The upper set should sit on a plastic sheet and the lower set should be raised off the floor. All cabling, power lines, and gas lines should be strung so that they are not a trip hazard and do not get in the way of anyone wanting access to the downstream alcove and F.C.. - Simon will start to prepare the electronics in the Test Lab for movement to Hall B. He will also coordinate with Doug Tilles for the move.
Circuit Boards
- Chuck and Kim will prepare list of detailed questions that they need to get answered to finalize the design of the STBs and HVTBs. These lists should be ready for our next FDC meeting.
ASIC Developments
- The first ASICs have arrived at UPenn where Mitch Newcomer is testing them. We would like to be able to use these amplifiers to read out the small-scale prototype. However there are compatibility issues with the chamber and the readout electronics. To address the issues with the chamber, a small circuit board needs to be designed by Fernando to act as a go between for the daughter board and the chamber. On the read out side, the daughter boards will not be compatible with Gerard's shaper board, nor are they compatible with the VPI postamp. Fernando will think about what needs to be done and the priorities for this work. We will discuss this more at the next FDC meeting.
Space Requirements
- We had a discussion on the short term and longer term space needs for the FDC, both in the EEL building and the new planned test lab building (which should be on-line in roughly 2011). The final ideas where handed over to Tim to present at the upcoming "new building discussion meeting".
Cabling
- Joe provided numbers (actually several weeks ago) on the modified readout cables that we are planning to use. DSC and Simon need to meet with Dave Lawrence to get this modeled in the simulation.
Simulations
- Our requests for Monte Carlo simulations to address the question on the material in the active and in-active portions of the FDC still have not led to anything that we can use. Simon and DSC will meet with Dave Lawrence to find out where the simulations are now and what needs to be done so that we can finalize the material designs. We have been waiting for answers for far too long and this has really hampered our ability to move the design forward. - We again discussed the need for simulation results to enable us to make a decision on the wire plane orientations within an FDC package. The nominal design is U,U,V,V,W,W and we are proposing something more like U,U',V,V',W,W' where the primed notation includes a half-cell offset in the wires between neighboring planes. We need to find a way to address this issue. It is already becoming clear that our tracking algorithms will require local left/right ambiguity resolution.
Work List
- The FDC short-term work list has been posted on the FDC web site (see http://www.jlab.org/Hall-D/detector/fdc/). This is continually being updated and DSC welcomes any feedback or comments from the group.
Minutes prepared by Daniel. Send any comments or corrections along.