NuMI-L-563 R. Plunkett MINUTES OF THE MINOS INTEGRATION WORKING GROUP ---------------------------------------------- October 17, 1999 Agenda ------ This meeting was held at RAL (actually at Cosenor's house - thanks!) and concentrated on near detector issues with some discussion of the far detector when there were relevant overlaps. Attending --------- R. Plunkett (chair), A. Byon-Wagner, D. Ayres, J. Thron, B. Baller, J. Nelson, E. Peterson , B. Miller , D. Michael, J. Urheim, J. Alner, P. Adamson (apologies to anyone missed). Item: Steel Tolerances ----------------------- Jeff Nelson presented a recap of the tolerance issues. Near waviness spec has been a concern because we might want to make the gap bigger, then the far must follow. Once gap is set, thickness tolerances set overall length. Collar is another concern, as it needs to be shimmed during assembly to keep it straight. Need enough tolerance in center to deal with this. During assembly of 4PP, there were crunchy moments when the scintillator contacted, probably the collar. Recommendation is to increase the bypass tolerance. Discussion: The bypass tolerance is near the point where another whole strip will be sacrificed if it is increased. A long discussion of the sag in the columns and the collar shimming procedure showed people still think this is a major worry. The waviness problem in the near is probably small enough that it can be dealt with by retrofits to adjust a few gaps or by plate sorting. (Note - a study by Rob shows it's probably less than an 8% problem). We DECIDED not to recommend changing gap thickness. Earl P. proposed that we accelerate purchase of 40 planes of near steel to see if vendor continues to have problems with the waviness (right now several plates required rework to meet specs - but it was successful). Because of the cost, this idea will need to be considered carefully by project management. The buildup of steel thickness tolerances may also not be a problem, and there are ways to deal with it (by changing bolt head thickness by a little, e.g.). It was decided the length issue needed another iteration to reach closure. Item: Near Module Layout ------------------------ Bruce Baller recapped his presentation to the scintillator group. The main remaining issues were the reflector connector and the module layout. It is also possible to bisect the coil hole by moving modules around, but the module layout change is probably preferable. Discussion: Doug reported that the scintillator group prefers the reflector connector. Action items listed below will get more information. Low intensity running will help understand the time overlaps. Going to 16-wide modules looks like the preferred layout solution of this meeting. Project management agreed with this idea. Cost needs to be understood, but is likely to be modest impact. Item: Trial Near Rack Layout ----------------------------- Rob presented the current thinking on near frontend rack layout. The number of phototubes per rack is approx. 30, arranged in horizontal MUX boxes which hold 4 in one level of 4.5" (for partial planes) or 6 in two levels of 4.5" (for full planes). Numerology works out to 9 racks. The only way to do this is to put two racks together so that only one side is accessible for each one. If one assumes that there is one M16 handled by one 6U VME card, and makes reasonable estimates of power supplies, rack monitoring, and cooling, there are 3" left over at the bottom of the rack. Discussion: The main concern voiced was that this simple census doesn't prove that the heat can be removed from such a densely packed rack. A real airflow design by an experienced engineer is required before we can settle. Obviously the M16/M64 decision affects this density - first estimates by Rob show that it would require 5 racks instead of 9, since the electronics is using up a fair bit of space. There is discussion going on about doubling the density of the electronics, which may be doable if the cards are long enough. As noted below under MUX boxes, some more space could be recovered by fitting 6 PMT into a single row, if it can be done. Jonathan floated an idea to put the MUX boxes and the VME crates on the same level. This minimizes their cable run, provides an air channel for cool air, and gives more vertical space. The access difficulties and connection difficulties look quite serious. Item: Near Mux Boxes (with discussion of far) --------------------------------------------- John Alner discussed his trial horizontal Mux box design. Useful in the near detector, he listed advantages also for the far detector. This were: i) More connector space ii) Support bar for fiber strain relief iii) Easier to connect near edges (I think - notes confused) The aluminum box is sturdy and accesses from the rear. A mu-metal shield is integral to the tube-holding assembly. Discussion: Questions arose about the ability to make 4-wide and 6-wide versions. (Model shown was 3-wide). Four can be done easily, six needs thought but may well be achievable. The mu-metal shield needs to be extended into the light- tight volume to cover the photocathode; can this be done? J.A. will contact Stuart to discuss shielding. How are cables routed out of the box? No one was perfectly comfortable with a bundle of RG174 because of bulk and difficulty of mass termination. Length of cable needs to be held to 3 ft. if possible. Conclusion was that more information will be gathered before any proposal to change the far detector; this model will be used for near detector design studies. Item: Light Injection System ----------------------------- Phil Adamson presented current plans. There are two options in the far detector for pulser placement. Both have the system either daisy-chained together with RS485 control lines or hooked to ethernet. Pulsers must illuminate the fibers, PIN diodes, and possibly monitor tubes. First option has a pulser box in each frontend rack. Fibers run 30 planes in length, doing 15 planes in the relevant view. Thus each LED illuminates 15 fibers on different planes. There are 20 LED required by the module numerology. Please note each LED can actually handle 60 fibers. In the second option, pulser boxes are on midlevel. Fibers light up 60 planes. Right now component costs look comparable, with a tradeoff between fiber runs and extra boxes being looked into. For the near detector the numerology depends on the module with choice. Need 8 LED for M64, and it's enough for M16 too. May need 2 or more probably 3 boxes per catwalk in near ==> 2 calorimeter/1 spectrometer. Discussion: Concern was expressed about using expensive ethernet modules for all these connections - is that the right decision by the controls group? It turns out that there is also a timing cable issue - fiber lengths need to be evened out for, e.g. PIN diode delay. This needs to have its space taken into account. In far option 2, the designers were expecting to get 60 connectors into 15" of vertical space. This could be very difficult, and the group anticipates that 21" will be needed if this option is adopted. (It's not the base design right now.) Near detector needs about 30 connectors/box. Action items were generated, as listed below. Item:Near Cavern Width ---------------------- The change to QIE has put pressure on the cavern width in the near hall. Agressive choice of narrow racks, 6" for wall utilities, and 8" behind racks just fit with no extra clearance. Also requires moving cavern over to eliminate unused inches on magnet side of detector. Discussion: The group felt cost of extra space needed to be pursued with Chris Laughton. Options to reduce cost impact would be to only do part of the hall, or to eliminate the DAQ room. NOTE: Since this meeting a request to widen the hall by 18" in the downstream half, and to remove the DAQ room, has been submitted to project managment. - RP Item: Survey Needs ------------------- Dave Ayres pointed out that there is not yet a L3 manager for survey, and some question about the exact extent of the survey needs. The 4PP used a lot of time and expensive equipment; we have costed cheaper equipment with some labor help in the TDR. Discussion: Doug feels strongly that there is not a need for supreme accuracy in the survey. These are 4cm strips dominated by multiple scattering. Discussion focused on the possibility of measuring the one important coordinate (the transverse strip edges) with simple tape measure and jig setups. Several ideas were advanced, like a collar jig to measure from the hole outwards. It was recommended that we measure the last plane with a tape technique to compare with what the surveyors get. Action Items ------------ - Fermilab will measure the timing distribution of a reflector connector on a module, and draw up a near detector layout using them. - Electronics group needs to give a PIN diode interface concept to the the integration group - suggested by review of near electronics. - Integration group to communicate module layout specifics to Sussex ASAP. - Steel group to communicate scale field varies over, as it affects survey needs. - Scintillator module edges to be measured with tape before plane raised!!! R. Plunkett 9/12/99 Please note: any errors are entirely my fault and can be corrected if necessary.