From settles@mppmu.mpg.de Mon Jul 9 13:39:52 2007 Date: Wed, 4 Jul 2007 08:34:22 +0200 (CEST) From: Ronald Dean Settles To: lctpc@desy.de Subject: Summary WP#33 phonemeeting 27.06.2007 Dear LP/LCTPC friends, As we said, there will be no phonemeeeting today 4July, but in one week on 11July. Here is the draft-summary of last Wednesday's meeting which includes additional information from subsequent emails with Takeshi, Dean, Paul and Dan. As you can read, there are still several loose ends to clear up at the next meetings. Let me know if you find anything below that needs modification... Cheers, Ron WP#33 27/06/2007 -------------------------------------------- Wednesday 9 May 2007 West Coast East Coast W.Europe Japan 07.00 10.00 16.00 23.00 Present: --Paul Colas --Klaus Dehmelt --Ralf Diener --Madhu Dixit --Katusmas Ikematsu --Akimasa Ishikawa --Leif Joennson+guests from Brussels (see below) --Sasha Kaukher --Dean Karlen --Martin Killenberg --Vincent Lepeltier --Takeshi Matsuda --Ulf Mjoernmark --Dan Peterson --Ron Settles --Akira Sugiyama --From Brussels: Gilles De Lentdecker Jean-Paul Dewulf Xavier Janssen --anybody forgotten? Agenda -------------------- 1. Klaus Dehmelt led the discussion on the cosmic trigger. The conclusions are: --LP1 should be rotated by 90 degrees for cosmic running. --The trigger hodoscopes should be outside the magnet, above and below to simulate as nearly as possible radial tracks matching the pad layout (the concrete block below will be removed when the table is ready). They will be movable according to the position in PCMAG. --Whether SiLC can be rotated with the TPC to the cosmic position depends on the mounting mechanisms for the TPC and the SiLC. Klaus will be working on this together with the SiLC colleagues. Since one can imagine cosmics tests for the combined TPC+SiLC system, it would be good to find a mechanical solution. If such mechanics turn out to be too complicated, then SiLc will have to be removed for cosmic running. --The number of trigger counters should be minimized. The Calice Hcal people have experience with MPPC (which are needed because of our B-field) and with the topology of counters/fibres, so Takeshi (with Japan Calice) and Klaus (with Desy Calice) will talk with them about the design the counters/lightguides. --Dean meanwhile has sent details of the T2K counters: "The T2K SMRD detector modules consists of 4 scintillator slabs of dimension 870 x 170 x 10 mm for use with SiPM readout...using fibres placed in S grooves. They are making about 500 such modules... the LCTPC would need about 1/2 of a module. We can contact Yuri Kudenko at INR (Russia) if we are interested in this. I think they are ordering 1000 slabs for September." --Responsibilities: Basic design: Klaus Dehmelt Purchasing and fabrication of the scintillator slabs plus light fibres: Paul Colas Electronics and power supply: perhaps Paul Colas (or the CDC group) (under discussion) MPPC: CDC group Assembly and Lab test: perhaps Saclay (under discussion) Support and installation at Desy: Klaus Dehmelt Schedule: ready beginning 2008. 2. After Dan Peterson's and Peter Schade's talks at Desy three weeks ago http://ilcagenda.linearcollider.org/materialDisplay.py?sessionId=51&materialId=0&confId=1296 Dan's slide 4 and Peter's slide 2 are the same, and this slide contains several errors. After today's phonemeeting, here are some points which were clarified; Dan has added a drawing and comments at the usual place http://w4.lns.cornell.edu/~dpp/linear_collider/LargePrototype.html. Here is Dan's summary of the situation as of 3 July: "From the meeting, 2007-06-04, at DESY, we agreed on a new field cage size (as you described 2007-06-27). In summary: ---magnet inner bore 850mm ID --SiLC detectors (see phonemeeting #27) 35mm on radius --clearance inside of SiLC 780mm --extra clearance (see phonemeeting #27) 5mm on radius --OD of field cage 770mm --field cage wall 25mm --ID of field cage 720mm --module insertion clearance to field cage 3mm on radius --"stay clear" diameter 714mm We agreed to have 40 bolts, 6mm x 1mm. There will be bolts mounted in the vertical and horizontal positions. There can be 4 pin positions in the field cage. There are other design parameters on which we must agree: 1) bolt circle radius for the 40 M6 bolts (this is 376mm in the drawing shown on the web page), 2) whether the o-ring groove placed in the field cage flange of in the endplate, 3) o-ring size and radial location (this is a 4mm grove, with IR=365mm, in the drawing on the web page), 4) location of the first field shaping band (this 35mm, to the edge of the first band, in the drawing on the web page), 5) location of the field shaping band that defines the end of the drift field (this determines the step in the endplate). We also discussed whether a gas seal could be made in a G-10 field cage flange. We decided that a gas seal demonstration must be made using the material, o-ring, bolts, and bolt spacing as proposed." --Back to the phonemeeting, Dan asked that the flatness specs be defined. (Note added by RS: To start this discussion, I recall that our tolerance was 20 microns_mechnical in Aleph; we achieved about 20 microns_sigma. Due to the inherent strength of the sandwich construction, the bending by the 6mbar overpressure was 20 microns. For Aleph, the tolerance was mainly to reduce the gain variations due to the wire-to-pad distance, which is not an issue here. Here the issue will be the 2mbar overpressue and also the electron drift of about 50 microns per nanosecond in the drift region and about 1/2 that in the induction gap, and we are trying to achieve about 1-2 ns time-stamping accuracy: a 20-30 micron tolerance would apply to the combined Gem/Micromegas-pad plane). --Gas-tightness tests: 2mbar overpressure will be used from now on since this is the Star experience. --Stress-relief tests: done, analysis in progress. --Cable supports: Dan will include brackets in the design. --Gas inlet/outlet, to be decided later. --Temperature stability/cooling: tolerance to be decided later. 3. Leif and Akira produced layouts for the connectors for a curved padplane. --Lund's layout is for 1mmx4mm pads on a curve (with connector ribbons?) --The CDC prototype is with 1.17mmx5.0mm pads (without connector ribbons?) Discussion: The Lund version is agressive with the highest possible connector density. The CDC version assumes a twice larger area per connection and is thus more conservative. The suggestion by Leif is that a group making a panel is responsible for the pad size, the connector layout and for the production of both; it will likely be necessary to fabricate a tool to help make the connections. Sasha reminded that he is planning to test the TOC electronics which will be mounted directly on the endplate. Paul suggested that a mockup be made by a given group to test the connection proceure. 4. AOB --In conjunction with agenda point 3 above, the pad size was discussed. We have never investigate the pad-angle effect systematically for the overall momentum performance. It would be useful if simulations could be done so that we have a better understanding when it comes time to make a decision. As a reference, for the standard-readout Luciano et al are designing for one channel per mm^2 (the summary of the LCTPC electronics meeting on 14 June will be ciruclated when it is finished). --Takeshi ask about the number of electronic channels for LP1. Leif reminded that 10000 are ordered and the money for at least half of them has been promised by several groups. Leif will make an update to the LP1 electronics situation, since additional money has been secured by the CDC groups. --Leif said the Brussels has decided to join the work for producing the LP DAQ. --Next WP#34 phonemeeting: 11 July 2007, usual time.