FDC Weekly Meeting
Date: January 24, 2008
Participants: Daniel, Brian, Simon, Roger, Chuck, Fernando, Bill, Elke, Denny
Next Meeting: January 31, 2008 @ 1:30 p.m.
Composite Wire Frames
- Two of the three composite wire frames needed for our test winding have been completed in the JLab machine shop. With the third frame, there were some minor problems with the epoxy layer for the o-ring group that required some additional machining time. The last thing to do is to machine the through-holes and the full complement of frames will be done and ready for winding.
- Allison has promised to look at the purchase request for the test wind and hopefully she will move to sign the paperwork soon. More details to come when we have word on progress or delay.
Composite Cathode Construction
- Brian and Denny are now starting work on construction of the first composite cathode. They are gathering all of the necessary parts and pieces to begin assembly. The big aluminum jig plate that is being used to machine the through-holes for the wire frames is needed before epoxy is applied to the G10 skins. Construction should begin tomorrow. - Brian estimates that it will take about two days to complete construction. - Brian will spend some time finalizing the layout of the ground plane that goes between the cathode planes in the sandwich. This cathode needs to have tabs that stick out and are accessible to make connections to the external chamber ground. - We had some discussion about the latest design modification to make each FDC package a single gas volume. The issues are how to make holes in the cathodes and ground planes. Both are very thin and we believe that pre-cutting the boards before installation will not work. The cathode holes, which could be located in the center region where the strips are removed and at the outside edges where there are no strips, could be laser cut after the 2-mm thick foam backing is attached. This will need some testing. The ground planes may be more tricky as they are only 6-microns thick. Brian will think about options and come up with some drawings. It may be that we could put the gas through-holes for the ground plane in the support frame. Bill will talk to Tim about what tools we have for impedance calculations. Whatever options we choose, we want to ensure that we have good gas flow throughout the entire FDC volume.
- Brian plans on mounting the +/-75 deg cathodes to their frames for the small-scale prototype next week. Keep in mind that these are the first boards that we have with 2-micron thick copper. All other boards have 5-micron copper strips. These boards will be installed into the prototype shortly. - Simon and Fernando have prepared a pulse library for Gerard and Mitch from the readout of the prototype with the ASIC preamplifiers. Due to the very large gain, they have attempted to prevent saturation by reducing the HV on the chamber (probably below the plateau knee). These data (8 channels of anode and 8 channels of cathode) were taken with the 18-m long Amphenol Spectra-strip cables on the readout. - The data with the ASICs was taken without the proper setup for Gerard's shaper boards. Gerard will send a list of necessary component modifications to Fernando who will make updates to the board. We will have a meeting with the FDC and CDC folks, along with Mitch to discuss the results of the work in the next several weeks. - Fernando measured the cross-talk on the Amphenol readout cables to be less than 1% -- good news. - Simon will soon take a long cosmic ray run with the ASIC readout to check resolutions and to compare with the prototype readout with the Hall B SIP amplifiers. He will need to perform a gain calibration run. This measure of channel-to-channel gain variations for the ASICs will be nice to compare to the bench measurements that have been made.
B-Field Test Data
- Due to the low statistics and problems with the multiple scattering (and hence track definition), it is not clear if we will every get convincing results from the test run. We had hoped to be able to see the Lorentz shift along the wire compared B on data with B off data. However, given the multiple scattering through the magnet pole, we cannot easily pick out which side of the wire (in the small-scale prototype) the event passed. The issue is that the sign of the Lorentz effect, and hence the shift direction, depends on which side of the wire the event passed on. It may be that we will be able to pick out a width change that can be compared to a model. - Note that the current analysis of the B-field data shows a narrow peak in the difference between the external tracking chambers and the small-scale prototype (which is what we are looking for), but it also shows a sizeable non-symmetric background (that we do not understand). Simon will continue with the data analysis and continue thinking about this analysis, but we agree that this work is not as high a priority as other things that he is working on.
- Fernando has completed his review of the STB and HVTB design and passed his comments on to Kim. He had some issues with the labeling of the signal lines and there were a few places where traces on neighboring boards cross each other on adjacent layers. Kim will work to make changes to the boards. She probably has 2 to 3 days of work to complete the boards. Kim has already started the paperwork to begin procurement as soon as the board design is finished. She will also order the necessary components and connectors at the same time.
Cathode Daughter Boards
- Based on the feedback and discussion from our last meeting, Roger has updated the cathode daughter board to include the ERNI connector and the addressing resistors. Roger will look to the nominal geometry defintions for the cathode frame to be sure that there is room for the now wider cathode daughter boards given the locations of all of the boards and the locations of the through-holes.
- Bill has continued to investigate our options for a chiller system for cooling the FDC preamp boards. He believes our best option will be to construct our own system that employs the LCW in the Hall. He will prepare a block diagram of his ideas and circulate for comment.
LV/HV System Design
- DSC and Fernando will meet with Joe next week to follow up on his planning of the FDC LV and HV systems. Fernando has prepared a low-voltage block diagram that he will pass onto Joe. He has already prepared a similar document for the HV (GlueX-doc-927) that has been posted on the portal. - For the LV system, Fernando is planning on a distribution box just outside the solenoid. The LV lines from the chambers will be cables compatible with the ERNI connectors. They carry both power and signals (for addressing and temperature readout). In the distribution box, the signals for the addressing and readout will be split from the power lines. - Fernando still has not made a decision on whether we will employ a CAEN or a Weiner LV system. Both are possibilities. It is clear that with these power supplies, we will not need a fuse system. - In his layout he has a single cable for each cathode daughter board and will have two cables for each wire plane (one for each STB).
- DSC has collected all of the available FDC subsystem design drawings and placed them on the FDC website. The URL is: http://www.jlab.org/Hall-D/detector/fdc/drawings.html. Folks should go through the drawings and let DSC know what drawings and/or categories are missing for a complete design set.
- The FDC mini-review on technology choice is scheduled for Feb. 1. The reviewers will be Howard Fenker (JLab) and Larry Weinstein (ODU). DSC has prepared a new version of the FDC Technical Design Report to reflect the current system design. This will be provided as part of the pre-briefing material. - The planned speakers for this review are Mark Ito (physics overview and needs), DSC (FDC design), Simon (FDC R&D, measurements, and algorithms), and David (GEANT3 simulations). - We had a planning meeting just after this FDC meeting to begin to review the status of the talks and other preparations and results that are needed both for this review and the March chamber review. Talk versions will be posted soon for all to see.
FDC Insertion and Cabling
- During the collaboration meeting there was some discussion on having the FDC cabling come the upstream end of the solenoid magnet instead of the downstream end. We had a separate meeting of the relevant folks last Friday. Fernando has been working on defining the impacts and relocating the electronics racks for the different detector subsystems.
Space Plan Request
- Elke asked us to prepare a space plan request for the FDC construction, testing, and storage. Brian and DSC will come up with a plan to circulate for feedback.
- 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.