Re: FDC meeting minutes

["Fernando J. Barbosa" <barbosa@jlab.org>]

Hi Simon,

    Just a small correction. The maximum junction temperature for the 
regulator is Tj=125 degree C and, for reliability reasons, we need to 
operate all devices below 100 degree C.

    May a foolishly suggest we stick with degree C for any further 
discussions? Metric system anyone?

Regards,
Fernando




Simon Taylor wrote:
> Hi.
>
> I've posted the minutes for the Dec 6 meeting to the wiki:
> http://www.jlab.org/Hall-D/software/wiki/index.php/Minutes_12-6-2007
>
> For convenience they are also appended below.  Feel free to send
> comments/corrections/complaints to me.
>
> Simon
> _______________________________________________
>
> Attending:  Fernando B., Bill C., Roger F., Chuck H., Mark I., Brian K.,
> Kim S., Simon T., Tim W.
>
> *Cooling system
>
> Bill presented two solutions for cooling the preamp cards, one involving
> straps between the cooling lines and cards and the second a refinement of
> the
> scheme with the clamps and aluminum tubes he presented last time.  The
> "strap" method did not provide sufficient heat transfer.  The temperature
> at the cards
> in this scheme would be about 159.4 degrees F, significantly higher that
> the ~125 degree F ceiling for the ASICs.  Fernando indicated that the
> temperature at the regulator on the preamp cards should be kept below 100
> degrees F due to problems of reliability at high temperatures, which means
> that at the copper brackets this temperature should be less than about 30
> degrees C (=86 degrees F).  The "tube" method leads to about 90 degrees F
> at the copper bracket, so it is clearly a better solution than the "strap"
> method.
> Bill was able to position connectors on the cathode boards for the cooling
> system to accommodate both the cathode and anode cards without moving any
> of the connector positions on the anode boards, which means that Kim does
> not have to modify the STB board design.  The coolant we are planning to
> use is fluorinert ([http://en.wikipedia.org/wiki/Fluorinert wikipedia
> article] at about 72 degrees F.  It is not clear we will need a chiller,
> but it might be nice.   The coolant feed will be in the region of the
> rails.  The tubes will be attached to the frames at various places.  One
> possible place where the design could be improved is the mechanism of heat
> transfer from the brackets to the tube: the current idea is to use thermal
> epoxy but a few degree improvement may be possible with another choice.
> Tim suggested indium.  Since the "tube" design is right on the borderline
> of being acceptable for the amount of cooling the cards need, we should
> probably
> do a test.  Bill has already generated suitable drawings of the brackets.
>
> *Wire frames for winding test
>
> Brian has constructed 4 of the 5 frames (2 with low density Rohacell and 2
> with medium density Rohacell).  The 5th should be done by some time next
> week,
> whereupon the next task is to work on the cathode planes.  We are only
> planning to ship 3 of the 5 to whereever we end up doing the winding.
>
> *Cathode readout
>
> Roger is continuing to work on the rigid-flex boards.  The rigid boards
> will have to be 2-layer boards; the board dimensions have also changed.
> This means
> that another round of estimates from vendors will be needed.  The layout
> for cathode strip readout is also underway pending the new connector
> positions
> that the cooling design requires.  Chuck will provide the information to
> Roger.
>
> *HVTBs/ STBs
>
> Kim has started working on the traces for routing HV to the wires.  At the
> time of the meeting she needed input as to how many wires should be fed
> by a single high voltage line.  After the meeting Simon provided the
> scheme we will be using, namely a 20-16-12-12-16-20 pattern for sense
> wires
> and a 20-16-12-12-16-21 pattern for the field wires.   We also discussed
> how the high voltage will be supplied to the boards.  We will most likely
> use
> pigtails soldered to the boards.  There are a couple of possible
> connectors that we could use.  Fernando suggested that we fan out from
> 52-pin Radiall connectors to which the multi-wire cable would be
> connnected on both ends.  These connectors are used by CAEN HV supply
> boards.
>
> *Status of drawings.
>
> The drawings are in good shape with the exception that Chuck needs to
> incorporate Bill's design for the cooling system.  We should expect PDFs
> next week.
>
> *Preparations for ASIC/preamp card tests
>
> Fernando provided Simon two fine-pitch cables, low voltage cables, and
> preamp cards with adaptor boards.  He is working on a plan regarding what
> studies of the ASIC performance we would like to perform with the
> prototype.   He also indicated that a 250MHz FADC should be ready for
> Simon's use on or about January 15.
>
> *Miscellaneous items
>
> - The cooling design impacts the positions of the gas inlets.  The metal
> inserts may need to be bent at some angle as they exit the frames, which
> complicates daisy-chaining
> the chambers together with tubes connected to T's.  This needs to be
> worked out but is unlikely to be a serious problem.
>
> - We need to identify suitable o-ring material that has no conductive
> filler, is sufficiently soft, and reasonably radiation hard.  Tim has some
> candidate materials in mind.
>
>   
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