|
|
| Line 54: |
Line 54: |
| | there will be a meeting on Friday to discuss this further and also account for the necessary | | there will be a meeting on Friday to discuss this further and also account for the necessary |
| | space needed if the wire frames would be strung there at Jlab rather than at IUCF. | | space needed if the wire frames would be strung there at Jlab rather than at IUCF. |
| − |
| |
| − | = Electronics =
| |
| − |
| |
| − | - Fernando presented measurements of the discriminator part of the pre-amp cards. The worst card so far is showing ~30% variations (min - max range) in the effective threshold, among the 3x8 channels. The question was whether this is acceptable. We all agreed that we don't want to modify the present design of the cards. The variations of the detector response are expected to be compatible if not bigger than 30%. The only procedure that may be considered if possible, is sorting the ASICs before putting them on the cards.
| |
| − |
| |
| − | - Next week the design of the PCBs will be finalized (Fernando, Kim, Dan) and posted on the web. We discussed also the option of having checking points on the sense wire resistors at the readout side, related to the problems with the resistors discussed later.
| |
| − |
| |
| − | = Frame modification =
| |
| − |
| |
| − | - The one-piece-g10 frame came back from the shop ready to be glued to the PCB ring, the latter is in the shop.
| |
| − |
| |
| − | - Chamber 3 was tested for leakage through the ground plane, using a sniffer at the cathode side gas holes. Once more, the leakage was confirmed. Same test will be performed with chamber 2.
| |
| − |
| |
| − | = Wire winding update =
| |
| − |
| |
| − | - Dan informed us about the latest IUCF budget estimate for phase 3 including the wire winding upgrades. This and other topics related to the transfer of responsibilities from Dan will be discussed in a separate meeting on Monday.
| |
| − |
| |
| − | - The specifications for the wire tension will be revisited at the next meeting (Lubomir)
| |
| − |
| |
| − | = Full scale prototype tests =
| |
| − |
| |
| − | - Several sources of the HV problems we had during the testing were identified:
| |
| − |
| |
| − | 1. We found inside chamber 1 some metal pieces, like a wire piece, probably from the green cables used for grounding. Bill and Mark discussed how to avoid this.
| |
| − |
| |
| − | 2. The corona discharge we observed on the PCBs (at the readout side) was obviously causing some of the problems. It turned out that cleaning of the boards with alcohol helped. Probable explanation is that there are impurities in the epoxy (from the wire frame production) which combined with some impurities on the surface of the boards would create the discharge.
| |
| − |
| |
| − | 3. On one of the boards we found sparking at the card connector. By looking at the pins that were sparking (in dark) we identified the corresponding channels. Replacing two sense wire resistors solved the problem. Possible explanation is that the resistor contacts were damaged when handling the frames.
| |
| − |
| |
| − | - After fixing the above problems on chamber 1 we were able to set the HV at 2200V with 60/40 Ar/C02 gas mixture on all sectors.
| |
| − |
| |
| − | - Beni informed us about the tests he performed inside the tent with chamber 1. Using a scope he looked channel by channel at the signals (cosmics) from the pre-amps on the wires. He found that about 10% of the channels show high rate signals with amplitudes up to 300mV. These signals would disappear if lowering the HV.
| |
| − |
| |
| − | - The plan is to perform such tests for each chamber in the tent as being more efficient, possibly also using DAQ. We also plan to open chamber 1 and try to clean the corresponding wires.
| |
| − |
| |
| − | = Cathode frame design =
| |
| − |
| |
| − | - Alex presented his MC results investigating the size of the hole for the beam. Two separate effects have been studied.
| |
| − |
| |
| − | 1. The first one is the background created by the copper material on the cathodes. No change of the background within the statistics used, was observed when reducing the cathode hole size from the "standard" 2.3, 3.2, 3.9 4.6 cm radius for FDC1, ..., FDC4 to 1.3cm for all the packages. 1.3cm radius is small enough to insure high efficiency for hits with radial distance > 2.3cm as in the standard hole size. The thickness of the copper material (in radiation lengths) is ~20% of the target thickness. This means that the maximum increase of the background (without any hole at the cathodes) will be 20%. So, in principle it is possible to make the hole radius even smaller that 1.3cm.
| |
| − |
| |
| − | 2. The second effect studied, was the occupancies on the strips related to the size of the sensitive area. The latter is defined by the size of the wire deadening area and fortunately we can make a decision about this size later. Based on the strip rates, Alex suggested 3.0, 3.0, 3.9, 3.9 cm radius for the holes in the wire planes for the FDC1,.., FDC4 packages. The advantage would be that we will have two pairs of equal packages. Further investigations with MC using tracking are needed.
| |
| − |
| |
| − | = Other =
| |
| − |
| |
| − | - Bill proposed for the future meetings to have the physics discussions scheduled at the end of the meeting. Lubomir will try to better separate the engineering/organizational topics from the physics ones when scheduling the future meetings.
| |
| − |
| |
| − | <!--
| |
| − |
| |
| − |
| |
| − | [http://www.jlab.org/Hall-D/detector/fdc/frame_redesign.pptx frame design changes].
| |
| − | - The redesigned frame piece for the wire board is expected back from
| |
| − | the shop shortly.
| |
| − |
| |
| − | ==Wire Frame Update==
| |
| − | - The wire frame construction document is located at:
| |
| − | /u/group/halld/Engineering/PRELIMINARY DOCUMENTS.
| |
| − | - The review of the FDC PCBs is now underway. Preliminary comments from
| |
| − | DSC and Bill passed on to Fernando. He will complete his preliminary
| |
| − | review in the next several days. We will send the boards to Keith for
| |
| − | comments after initial questions are fully addressed. The plan is not to
| |
| − | move forward with procurement until after inspection/diagnosis/repairs
| |
| − | of the HV/current problems seen in the full-scale prototype.
| |
| − | - DSC is finalizing the tension specifications for winding. It looks like
| |
| − | the +/-5% spec is unnecessarily tight. Looks like +/-20% is full
| |
| − | satisfactory, although we will likely put a +/-10% spec on the Phase 3
| |
| − | winding requirement.
| |
| − |
| |
| − | ==Cathode Update==
| |
| − |
| |
| − | - We would like to push to get the cathode board procurement started by the
| |
| − | mid-April
| |
| − |
| |
| − | ==Prototype Testing==
| |
| − | - The current version of the full-scale prototype test plan is on the
| |
| − | GlueX portal as ([http://argus.phys.uregina.ca/cgi-bin/private/DocDB/ShowDocument?docid=1304 GlueX-doc-1304]).
| |
| − |
| |
| − | - Two layer test update: See the [http://www.jlab.org/Hall-D/detector/fdclog/ FDC Log Book] for updates on the continuing work.
| |
| − | - The delivery of the remainder of the preamp cards for the full-scale
| |
| − | prototype will be in mid-March.
| |
| − |
| |
| − |
| |
| − |
| |
| − | ==Construction Updates==
| |
| − | - The sense wire SEM checks are now complete and the wire sample reports
| |
| − | have been posted on the FDC [http://www.jlab.org/Hall-D/detector/fdc/new_reports/ Wire sample reports].
| |
| − |
| |
| − | - The original document for the [http://www.jlab.org/Hall-D/detector/fdc/design/phase3_work.pdf Phase 3 Preparation Work] will be reviewed
| |
| − |
| |
| − | - Master list on wire and cathode frame redesign work is located at:
| |
| − | [http://www.jlab.org/Hall-D/detector/fdc/design/modifications.pdf Frame Modification Work].
| |
| − | -->
| |
Pictures are prepared by Bill but not yet sent out. Redesign daughter boards, to fit dimensions.
Expansion of cathode film due to stretching is not compensated for in the current design. Nothing is
currently planed to accommodate for this effect. Main worry of Eugene is the soldering of the flex
boards to the film. Need one good trained person to do this job. 1.3cm hole in the middle of the
cathode boards is fixed. On the sides where the strips are split in two make cut strait while the
strips ending at the border of the 1.3cm Radius hole should be kept round.
Design finished in two weeks.
check Fernando's list.
fiducials for wire positioning will be white ink and behind the solder pads.
no holes on the periphery but other means to apply fixtures for cables.
more R53 further to the right to allow the gas lines more space.
humiceal on the wire frames inside the gas volume might be problematic in the
long run of operating the chambers. There is some concern that chemical reactions
might over a long time period with the humiceal might render the chamber inoperable.
variation in threshold is largest within a given chip. So no special chip selection is needed
or different threshold lines for different chips on the same preamplifier board.
MIP signals are well above the noise. see GlueX-Doc-1470
there will be a meeting on Friday to discuss this further and also account for the necessary
space needed if the wire frames would be strung there at Jlab rather than at IUCF.
