Minutes LCTPC WP meeting #117 on November 11th, 2010 ========================================= Present: At DESY: Steve Aplin, Klaus Dehmelt, Ralf Diener, Isa Heinze, Takeshi Matsuda, Jan Timmermans EVO/phonebridge: Mahdu Dixit, Jochen Kaminski, Martin Killenberg, Dan Peterson, Ron Settles (anybody forgotten?) 1) (General) News: - The date for the general ILD meeting at KEK is now fixed: 23-25 May 2011. Jan will create a doodle poll to find the most popular date(s) for a 2.5 day LCTPC Collaboration meeting (also at KEK), preceeding this ILD meeting: http://www.doodle.com/mnxf932r6wssg38z 2) one AOB point was moved forward: Steve Aplin presented the current Mokka model of the TPC for ILD (see slide under AOB). A few detailed questions by Steve could be answered on the spot. When scaling studies of this model will be made, only the gas volume radius and length can (or need to) be changed. 3) PCMAG/LPTPC status, testbeam schedule: - Klaus Dehmelt: - several small metal pieces were found inside the fieldcage, some of them creating a short between neighbouring fieldstrips. After careful removing them, the total resistance of the resistor chain was back to nominal value. - the cool down of the magnet is being prepared - the Saclay group will come with the Octopuce LP module and hopefully the DESY grid-GEM module will be available next. - as the current Octopuce module operates best with He-isobutane (80/20), the T24 testbeam area has to be prepared for flammable gas usage - the starting date of this ~2-week testbeam campaign is 28 November - Takeshi Matsuda: DESY and KEK are discussing the contract for the money transfer for the PCMAG modification; will be finished on 9 December when Joachim Mnich is visiting KEK. The Toshiba company has confirmed that they will do the modification. Keisuke Fujii and Joachim will visit Toshiba. A somewhat shorter bidding procedure will be done after April 2011. 4) News from groups: DESY (Klaus): the glueing of the GEMs and grids will be finished in few days. This will be followed with tests with T2K gas in a gasbox. the DESY module should be ready for tests with the LP in 2nd week of December Bonn (Jochen): working on a final pad plane for the DESY module Japan (Takeshi): the Japanese groups had a 2-day meeting discussing the problems experienced with their LP modules during last beam tests. They decided to re-make GEMS with more segmentation, 4 parts instead of 2. They could confirm with field calculations, that the distortions observed were due to the wrong voltage settings on the 3 bottom strips (out of 4 strips in total) of the "gate support cover cage". The groups want to do another ('final') beam test probably after May 2011. 5) WP5 discussions Dan Peterson updated results from his work on a low material endplate for LP1 and ILD (see slides file, which contains a nice picture of full size ILD TPC with 8 module layers spaceframes). - adding the inner field cage as endplate 'support' to the 'complete model' with space-frame-separator-plates reduces the deflection of the endplate (under 2 mbar gas overpressure) from 1.23 mm to 0.22 mm - the 'equivalent-plate' model of the LP1 endplate was completed with revised specs for the equivalent plates to obtain equal amount of material and deflection as for the struts model: width and thickness multipliers of 0.39 and 0.43 respectively. - measurements have been performed on 2 out of the 3 testbeams, the strut spaceframe beam and the LP1 mullion beam. The 30" long devices were loaded with 38.6N concentrated in a 15 cm wide region in the center. Apart from the wiggles already observed in the measurements without load (likely due to not employing the iterative machining and stress relief treatment during the production), the maximum deflection for the spaceframe testbeam was 0.042 mm and for the LP1 mullion beam 0.339 mm (factor 8 improvement, where a factor 6 was expected, see WP#103 meeting of 22 Apr. 2010) - the measured deflection of the LP1 mullion is 16% more than calculated, but the shape is accurately reproduced. The strut spaceframe beam deflection coincides rather well with the FEA calculation, but there is some uncertainty due to the amount of cross-sectional area of the struts in the model compared to the physical device. Dan therefore concludes preliminary that the model calculations are consistent with the measurements up to the level of 16% - Dan is considering to make LP1 endplates both in "strut" and in "equivalent-plate" design. We should think about stifness requirements and how much more space can be allowed in z for the ILD endplate (remember, such additional space should be taken from the active gas volume) - Dan will still complete the the 3rd (aluminum/carbon hybrid) small beam 6) further AOB: Mahdu Dixit questioned the TPC resolution parameters as given in LOI and PRC report. Ron Settles commented that the numbers in the performance table should be considered as 'executive summary' numbers, the full description including z and theta dependance are described in the LOI and were also presented in WP#111 meeting of 12 August 2010. Some further update is needed to include phi-angle dependances. Next WP meeting #118: November 25th, 2010 14:00 CET (note half hour earlier (in Europe and Americas) than during summer time) http://ilcagenda.linearcollider.org/conferenceDisplay.py?confId=4899 JT