Minutes-5-15-2008
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FDC Weekly Meeting
Date: May 15, 2008
Participants: Daniel, Simon, Brian, Fernando, Roger, Bill, Mark
Next Meeting: May 22, 2008 @ 1:30 p.m.
Contents
Cathode Planning
- Roger visited Allflex in Minnesota last week and spent the better
part of a day talking with the company representatives and touring
the different parts of their facility. In short, they are very
excited about the possibility of working with us on the FDC
cathode project. Roger was very impressed with the facility and
the level of cleanliness and professionalism displayed. He noted
that Allflex works only with flex circuits and materials.
- As a result of Roger's meeting with the sales representatives, they
came up with a list of questions for us to address when preparing the
PR. Each is listed with the results of the discussion from the
meeting.
* What degree of issue are pinholes in the material? Pinholes can
occur when a speck of dust or material is trapped between the
photo-resist material and the copper surface during the lamination
process. While every effort is made to ensure that the copper
surface is clean, these can/do occasionally occur.
We feel that given all work is done in a class-100 clean room, this
is the only specification that we need to provide. We are satisfied
that any pinholes (on a scale of a few mils in size) will not affect
the cathode performance given that we have reasonably with traces.
* What tolerance/percentage of line defects are acceptable? This includes
over-etched and spurious copper (under-etched) lines widths. Should we
consider 5%, 10% of the width?
Fernando believes that if they are willing to work to provide a 5%
spec that we would be satisfied with this.
* Gold-plating of the connector pads is not feasible, given the additional
handling necessary and possibility of damage to the panels during the
process. Allflex will investigate alternatives such as a peelable mask
or an organic mask material to prevent oxidation of the connector pads.
We are working to ensure that the cathode exposure to air is minimal,
therefore we feel that gold-plating should not be necessary. We also
felt that the inclusion of masks is not a necessity.
* Automated testing of the finished panels is not feasible due to the
disparity in size of their test fixture vs. the panel size. Manual
testing of each cathode strip to the connector pad can be done. Note
that there is no metal tie-coat that needs to be removed, so there is no
issue with a dead-short panel.
Our options here are obvious limited. We do require checkout of each
strip on each board before acceptance. As this work cannot be done by
Allflex, we will have to do the job here at JLab. Compounding the
situation is that Allflex has no history with 2 micron Cu thicknesses on
their boards, so we do not even have an expected probability of problems.
The issue is not opens or shorts on the boards given that there is no
tie coat on the material, the issue is strips with high resistances that
might result from fractures or microfractures on the traces. We need to
find out from Allflex what we can do if we find a board that does not meet
our electrical checkout specs.
* Panel-to-panel Joints - Allflex suggests that they provide us with uncut
edges and we trim them in-house during our assembly process. This is of
particular concern with the center section, as there is already minimal
width available for their tooling and alignment holes.
Our current assembly procedure relies on having a
precise edge on each board so that we can butt neighbors up against
each other. Roger will inquire whether Allflex could take this on and
develop a procedure to leave 0.5 mm of Kapton at the joint edges of the
cathode boards.
* Flex Material - In anticipation of our purchase order, Allflex has
ordered a sufficient amount of 2 micron material to accommodate our
prototype fabrication. We discussed the possibility of JLAB purchasing
a custom-made 5 micron copper Espanex material in sufficient quantity
for the production run. Allflex is exploring that avenue with their
associate representing the Nippon Steel Corporation in the USA.
We are still very interested in obtaining samples of boards with 5 micron
Cu. However, if its availability is uncertain for the short term, we
will order a larger sample of 2 micron Cu boards (perhaps 10 full sets).
This will leave us with extras in case of QA problems and will give us
boards for testing (both Fernando and Gerard have expressed interested
in performing basic checks on the boards).
- Roger will work to prepare the PR, however, there are several issues that
need to be dealt with. First, Fernando has reviewed the board design and
has asked Roger to make some minor changes to improve the grounding
layout. This work is in progress. He will recheck the boards after
Roger has completed his work. Second, Bill has come up with a layout
for the through-holes in the cathode boards to enable good filling and
gas definition throughout the active layers. We decided that he can
provide Roger with the coordinates of these holes and Roger can include
them in the design. Note that Bill will update the frame drawings to
include the new holes.
- No progress has been made during the past week on additional solder
tests of the rigid-flex assembly to the cathode board mock up. Greg
Arnold's group had allegedly purchased a hot air pencil, but we found
out that the order never when out because of problems with funds.
Fernando will lend one for this use from the Fast Electronics Group.
- Note that due to the height of the solder connection between the
cathode board and the rigid flex assembly, we will have to revisit
the design from the standpoint of adding clearance pockets on the
surfaces that mate up against this solder region. We did find out a
new option for the ends of the rigid-flex assemblies. The company can
actually leave the last portion of the assembly without Kapton backing
so the copper traces stick out past the end of the flex piece. This will
enable easier soldering. We will have to investigate this further, but
in any case, we will still have to modify the design to allow for
proper clearance for the connection between the rigid-flex assembly
and the cathode board.
- Bill will look into ordering a storage box (called a pelican box) for
the long-term cathode storage. Roger learned that the cathodes will
come from Allflex shipped flat. If we can order this box and ship it
to Allflex, they can use it for a delivery container. We can easily
modify the box to include the nitrogen gas fittings.
- Brian will modify his Lucite box design for storage of the completed
cathode planes. This cathode planes can stack up on top of one another
(unlike the strung wire frames). He will make some minor modifications
to the existing box drawings and prepare the PR.
Full-Scale Prototype
- Outstanding procurements for the full-scale prototype:
* The HV capacitors will be delivered to us in a few weeks.
* The 2nd construction station PR has not been started. Brian
will get to this when he is available.
* The rails (all 4-m length of them) have arrived.
* The rail attachment assemblies are being worked on by Bill. He
has provided a draft set of drawings to Tim Whitlatch to review.
* We are still awaiting delivery of the 2-mm Rohacell for
the cathode backing. While Brian was cleaning up EEL 126, he came
across a box with a half dozen 2-mm sheets, so we have enough for
now.
- The clean tent in the EEL clean (ha!) room is now ready for us to
move in. Brian will start by moving in a table and a cabinet. He
will prepare a PR for two 5 ft x 5 ft granite tables. One will go
into the clean tent, and the other will go into our new assembly area
in EEL 126.
- Brian needs to provide Casey with a drawing for the modifications to
the aluminum tooling plate used for our wire plane and cathode
construction. Once he does, it will probably be at least 2 weeks before
we get the plate back.
- Brian and Bill will work to update our wire frame construction sequence
document. Brian will provide a first draft to Bill who will work to
polish it up. We would like to provide this to Casey so his group
(and of course ours) can full understand the procedures.
Test Frame Wire Winding
- The Phase 1 wire winding contract ended officially on Friday
May 2. DSC has received a preliminary report on the status of
the work, and this report will be improved by IUCF and updated
over the next week. Basically they gave us what they had to
fulfill the contract requirements, but it is not complete.
- IUCF ended up winding 3 planes. Brian brought back two of them
with him to study the transport scheme (looks like no wires broke
on the 12 hour ride from Bloomington to NN). There were some
problems that were found during the winding process:
* The technique used to support the wire frames under the wires
was non-ideal and this cause significant problems with the
final wire placement on the boards. This problem was diagnosed
after winding the first two wire planes. A modified procedure
was used on the third plane with improved results.
* The placement on of the field wires on the winding table, done
after the sense wires were wound, had a minor problem. The
technician did not account for the differences in wire size.
Thus the wire spacing had an offset (too big on one side of the
sense wire, too small on the other). This is not a real problem,
and will be accounted for in future winding.
* The wire placement distribution shows a fairly sizeable number
of wires outside the +/-50 micron spec. The fraction of these
outliers is about 10%. This is more than an order of magnitude
too large. The folks at IUCF are investigating this, but believe
that it may be caused by worn equipment on their wire spooling
and winding equipment.
* There was suspicion that the wire measurements had a correlation
of where on the measuring machine the wire frame was placed. Data
were taken to quantify this problem, but DSC has not gotten the
analysis as of yet.
* The wire tension measuring system was painfully slow, and so full
tensions measurements on all wires were not completed. Kim provided
the IUCF folks with the wire lengths, and they have taken hopefully
sufficient tension measurement data to give us a feeling of what
tolerance they can provide. We had requested +/-5%, but it may
be that +/-10% is what their system can provide. We will know more
shortly.
* DSC will go over the Phase 1 data and meet with Elke to plan on
when and if Phase 2 will take place. We need to be sure that
IUCF can meet our specifications, both in terms of the detector
requirements and the budget. There are rumors that IUCF is working
to prepare a budget for Phase 2, but nothing has come our way yet.
* Finally, much thanks to Brian who spent a long week at IUCF
representing our group.
- DSC is working with Steve Christo to prepare a wire specification
document for the tungsten and CuBe wires leading up to procurement.
Steve is preparing a document for the Hall B chambers and we will
most likely adopt this document for Hall D. DSC reviewed the
existing Hall B documents to give folks a flavor of how these
documents have been prepared in the past. We need to make decisions
on what is required for the FDCs.
Stack Assembly Procedures
- DSC, Brian, Tim, and Bill will work to finalize the stack assembly construction document that has been prepared. This document should be in place before we get too far in the construction process.
Composite Cathode Updates
- Denny has extracted the tensioning system from mothballs and it is now being setup in the shop. Brian will work to make a tensioned cathode without foam backing on his return. In tensioning the cathode plane he will study how the 3 piece cathode reacts under tension. He will also measure the electrode distortion as the tension is increased. - The cathode tensioning work has been delayed due to a miscommunication between us and the shop on what was to be done. As the instructions Casey had received were not complete, DSC put the work on hold until all necessary equipment for the measurements was in place. Brian will be directly involved in all aspects of this work. - Denny has the Acquity Laser system from Fernando and has it fully set up trailer 94B. He has done some test measurements and verified that the measurement results agree with crude measurements. Bill completed the PR for the laser and it is now ours. Denny is modifying his setup to provide a more robust support frame for the cathode frame and is incorporating the ability to do 2D measurements with the system. DSC will push Denny to provide 1D measurements of our prototype cathodes down the middle so that we can understand the gravitational sag scale of the cathodes with the 2-mm thick foam backing. - David Lawrence will be supervising a high school student for the summer. This student will work on taking Denny's flatness measuring system and automating it to do full 2-D scans of our cathodes. This student will be arriving in the middle of June. - Fernando has indicated that he is worried about the quality of the cathode ground if we only provide a connection through the 10th daughter board. He has asked that we work to include additional ground connection points about the cathode perimeter. We have to look into this. One suggestion that came up was to make the cathode support frame a PC board (a simple one) that we could connect to.
Cooling System Tests
- Denny completed the set up of the cooling system. He then packed it up and will move it to F117 after the system review. Fernando will take over the measurements and study the cooling properties with a fully loaded preamp daughter board in place.
Gas System Design
- Vladislav (Slava) Razmyslovich is working on a preliminary layout of the gas handling system for the CDC and FDC in preparation for the upcoming systems review. We will sit down with him in a specialized meeting to review the design concepts when we get a chance.
Gas Volume Definition
- Bill has put some time into moving the design forward and the main points are given earlier in the minutes. Basically as the gas fills the volume like a liquid, he wants to include a series of holes in the cathode about the full perimeter of the board. This will require modification of the support frame (the G10 skin onto which the cathode is mounted) to allow for the gas to go through the G10 and the foam core. Note that any foam exposed to the gas must be sealed.
STB/HVTB Discussion
- Kim needs to provide an instructional writeup for the Phase 1 and Phase 2 wire frame PCB component attachment. This is on her to-do list, but is not a high priority for now.
Cathode Board Discussion
- Roger needs to prepare a document for QA/stuffing/cleaning for the cathode boards and a similar document for the cathode daughter boards and ground boards.
Small-Scale Prototype
- Work continues on characterizing the preamp daughter boards to specify the ASIC dynamic range for both the FDC cathodes and wires. Simon is extracting from the data the amplitude distributions. In detail, he is extracting the peak voltage amplitude from each FADC distribution. Sample results are in the FDC log book for the cathodes and the anodes. Knowing the gain of the ASICs, cables, and shaper (in fC/mV) we can work backwards for the muon data to specify the dynamic range. We can then specify the dynamics range for the more heavily ionizing protons and (more importantly) pions in the FDC chambers (know the difference in energy loss in the FDC for these different particles). Fernando will characterize the gain of the ASIC/cable/shaper combo for us in his lab. Simon is also working with simulations to try to come up with a cross check of the dynamic range that we extract from the data. For this, he is working with some advanced features of GARFIELD that model the ionization and clustering. - Simon, Fernando, and DSC will prepare a write-up of the analysis results and our analysis of the required dynamic range of the anodes and cathodes. Fernando will be in contact with Mitch Newcomer on our progress and plans. Our goal is to have a first draft of a report on this work by the end of next week. After the systems review, we will spend a few days to polish up the report and circulate it to a wider group for comments before passing the information on to Mitch. - Note that as we need to characterize the ASICs for both the FDC and CDC, it may be beneficial to the project for Yves to visit us from CMU to go over the measurement results and connection from the data to the final specification of the dynamic range. It is not clear when this visit would be most useful. Things will come into focus over the next several weeks. - Note: it is apparent that we will not have completed our work on the characterization of the ASIC dynamic range before the next submission deadline to MOSIS. However, it seems that we will have another submission opportunity later in the summer. This should not delay us too much - Brian will perform an optical scan of the cathode strip edges in one of our spare 2 micron Cu cathode planes. We want to make sure that there are no obvious systematic problems with the construction. He will work to find a x50 microscope to do this work.
Drawings
- 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. - Also folks should send DSC the latest design drawings where there have been changes to keep this web site up-to-date through the review season.
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.
