FDC Weekly Meeting
Date: November 29, 2007
Participants: Daniel, Brian, Simon, Roger, Kim, Chuck, Fernando, Bill, Elke, Mark, Tim
Next Meeting: December 6, 2007
- Everyone matrixed into our working on the FDC hardware aspects excluding Tim and Chuck have been provided with a detailed list of tasks and an associated time line for work until the end of June 2008. This is our internal deadline for completion of the construction of the full-scale FDC prototype. - DSC would like everyone in the group who has not already talked to him to schedule a brief meeting with him to go over the schedule to be sure we have an agreement on the list of tasks and the schedule. Please do this in the next few working days.
Formality of Change Requests
- As we are working toward a rather tight deadline to construct the FDC prototype chamber and to complete the system design, we need to have a bit more formality regarding changes in the base design. The issue of course is that the individual sub-projects for the FDC are highly coupled. A change by one person (even a seemingly minor one) may have unintended implications for the work that someone else is doing. - The first question that came up in this regard is "What is our base design". Chuck will review the drawings that he has and we will see if all of our nominal design choices are captured in his drawings. He will present some drawings at our next meeting. - The approach will be that any changes to the design will be advertised in advance of the weekly FDC meeting, then we will go over the requests in detail at the next scheduled meeting. We will either approve the change or not.
Composite Wire Frames
- Two of the composite wire frames have been completed. One has a medium density Rohacell core and the other a low density Rohacell core. The third frame is in progress and will be done on Monday. Within two weeks, all 5 frames will be completed. Three of these will be sent to the wire winding facility. - The construction of the wire frames has relied on our new alignment jig. This system works beautifully and does not seem to need any additional tweaks in design for now. - The wire frame storage box has not arrived yet, but is due into JLab any day now. - Brian has been asked to clearly label each chamber frame and make a clear logbook entry on the construction techniques with each frame. We need to be able to tell which frame is which. The same will be true for all of the frames that we construct, wire frames and cathode frames.
- We are presently awaiting the official budget from IUCF on the wire stringing project. This should be any time now. - DSC and Elke have been in contact with the JLab procurement folks. Due to the fact that we can have a DOE facility bidding against a university, we will not open this project up for bid as our two sources are FNAL and IU. - We will simply look at the two budget and make a decision based on which is the cheapest and complete the wire winding contract. - As things stand now, the paperwork on the JLab side is coming along and the final award of a contract should follow relatively quickly once all budgets are in hand. - We will keep folks up to date as there is news on this front. - No work yet on the strongbacks, but this work will be completed on the time scale of 2 weeks or so.
- Kim has been continuing work on the circuit board layouts for the wire frames. The outline of all six PCBs is complete and she has been laying out the power and ground for the STBs. This work is nearly done. She is ready to layout the traces from the HV isolating capacitors to the daughter board connectors. - Issues have come up with the final placement of the wire frame daughter board connectors due to issues of connecting the preamp board cooling brackets with the cooling lines. More on this issue is included in the cooling discussion below. - The connector placement issues will cause Kim to put the STB trace layout on standby until things are finalized. In the mean time, she will begin work on laying out the HVTB boards. - The issue of additional holes in the STB and HVTB boards was discussed. Presently we have 24 through holes for stack assembly. However, the need for additional holes for strain relief of the cooling system came up. We have decided not to include these holes in the circuit boards, but instead they will be included in the G10 backing skin on the wire frame. - We still have not converged on a final design for connecting high voltage to the HVTB boards. Both Fernando and Simon are investigating the available connectors. If they are too large, they cannot go on the HVTB. The design might then have to rely on pigtails soldered to the HVTB that extend back to a distribution board on the downstream face of each package. Discussions on this front will start to get serious over the next two weeks.
- Bill reviewed the current status of the design for the FDC electronics cooling system. The design is rather complicated due to the need to minimize mass, allow for connectivity to each of the 130+ cards per package, all while trying to meet the cooling system load requirements. This has lead Bill to move around the daughter board connectors on both the cathodes and wire frames. - Of course there is a conflict between the work Bill is doing and the work Kim is doing. She needs the positions of the STB connectors fixed to lay out the traces, but the present locations that Kim is using may not allow for connectivity to the cooling system as it is currently designed. - The cooling system and connectivity plans to the daughter boards cards looks rather cumbersome, with potential issues of accessibility of the daughter boards and other servicing requirements that are essential. We discussed a number of issues for Bill to consider as he moves forward. Certainly we should use aluminum instead of copper wherever we can get away with it to reduce mass. We all agree now that Fluorinert coolant is quite superior to water in this design. We also considered a hybrid system of brackets on some of the daughter board cards to connect to the cooling lines, and flexible straps on other daughter board cards. More thought on tweaking the design will be required to make the system work and still meet the physics (and budget) requirements.
Cathode Board Readout
- Roger has nearly finished his design for a system to connect the cathode boards to the daughter boards. He has gotten a number of price quotes that seem fairly reasonable. He still needs to include resistors for addressing lines for each card (he will use the same system design as Kim is using for the STBs). Once this is finalized, he will place an order for construction of a prototype. The design will use a short flex cable that is soldered onto the cathode. This flex cable will feed through a slot in the cathode support frame that attaches to a backing PCB onto which the daughter board connector is mounted. This backing PCB mounts on the back side of the G10 skin that the cathode is mounted to. - Roger will produce a side view drawing of his assembly so that we can understand how much space is required between the G10 skins of the cathode sandwich. - Roger plans on placing the order for the prototype parts before the end of the year.
- Roger has a design for the cathodes that runs the strips up to the individual daughter board connectors. Again, there are 9 daughter board connectors on each cathode board (eight on top, one on the bottom). This design will be updated once the daughter board connector placement is finalized. - The issue of how to actually construct the cathodes was discussed again. The nominal design choice is to back each 3 piece cathode design with a 2-mm thick layer of low density Rohacell. The main issue with construction is how to guarantee the relative alignment of each of the pieces of the cathode. This is still not worked out in detail. Once the five composite wire frames are constructed, Brian will work to construct a composite cathode. We have not constructed one of these as of yet. - The issue of how to survey the flatness of the cathodes came up again. At the present time, we do not have a scheme in place for flatness measurements. The JLab Survey Group has not closed the loop on doing something, and we have not pushed them lately. Brian will talk with George Biallas to see if he has any contacts that might be able to help us on this matter. - To support the cooling system, we will want to include some holes in the cathode frames near the outer edge. Bill and Chuck will interact with Roger to finalize the number and placement of these connection points.
Magnetic Field Tests
- Simon just got back to town after a week or so in Germany. He still is working on the data analysis. A more detailed report will be given as to where he is at our next meeting.
Daughter Board Testing
- Fernando has the daughter boards and interposed boards done and they are undergoing tests on his bench. We can take possession of them next week (3 cathode boards and 1 anode board). - We have been working to re-setup our cosmic ray test stand in the Test Lab. A lot of progress has been made and Simon is working on getting DAQ up and working. He hopes that by the end of this week, he will be able to take data. We will re-establish chamber operation with the Hall B SIP preamplifiers before we make the change over to the ASIC boards. We have also constructed two 18-m long signal cables of the type that we are envisioning for the final system (Spectrastrip cables). These will be used during the tests to make sure that the appropriate capacitance is modeled. - We test plan for what we need to provide to Mitch and Gerard is being developed. Gerard needs the input on the preamplifier performance for his design of the FADC front end circuitry (shaping) and obviously Mitch needs the information for the next revision of the ASIC chips. In this regard, Gerard and Simon will be traveling to CMU in about two weeks to work on the shaper design. The decision was made to work with the CDC system as this system has the most severe requirements for shaping to get the required time resolution from the FADC data. The lessons learned will allow Gerard to finalize a design that works for both the CDC and FDC. Gerard may also travel to JLab to work with Simon on the FDC in December or January as needed.
- The next FDC Monte Carlo meeting will take place tomorrow. Progress reports will be made on the continuing development of the track finding and fitting algorithms and the issues with modeling the chamber response in the magnetic field. - The FDC meeting on Dec. 13 will be a combined FDC/CDC meeting. We will have an FDC-only meeting from 1:30 to 2:15 p.m. and then the CDC folks will join us. The issues to be discussed are electronics and cooling. We will circulate an agenda as we get closer to the meeting so that we identify the relevant folks that need to be present for the whole meeting (but of course everyone is welcome to stay). - We have new lab space that has been made available in the F-wing of CEBAF Center. We need to decide how we can use this space as well as our space in the EEL building. - Brian will talk to Jack Segal about the FDC system taking up residency in the EEL building clean room tent. We need occupancy in April for prototype construction. - DSC will not be available for next week's FDC meeting. Simon will step up and organize the meeting and prepare the minutes. - The accelerator group has offered manpower to the FDC project. These folks have both electrical and mechanical experience. If there is a mission critical need for special project manpower for the FDC, talk to DSC and Elke and we can discuss it. The trouble is that Elke has no more money to spend.
- 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.