From settles@mppmu.mpg.de Sat Nov 15 18:36:17 2008 Date: Sat, 15 Nov 2008 18:35:54 +0100 (CET) From: Ronald Dean Settles To: lctpc@desy.de Subject: Advanced TPC-endcap: summary of 10.11.2008, agenda for today Dear lctpc friends, Jan sent mails with details of today's meeting, see http://ilcagenda.cern.ch/conferenceDisplay.py?confId=3140. In preparation for the advanced-endcap part, here is a draft summary of the previous meeting on 10.11.2008; those slides are at http://ilcagenda.linearcollider.org/conferenceDisplay.py?confId=3123. Please let me know if know if there are modifications to the summary below and I will include them in the final version... Greetings, Ron Advanced-Endcap#4 10/11/2008 Room 32-1-A24 at CERN ---------------------------------------------------- Monday 10 November 2008 West Coast East Coast W.Europe Japan 05.00 08.00 14.00 22.00 Agenda: ------- 1. TPC-endcap issues (15') Introduction by Ron Settles 2. LCTPC electronics issues (15') by Luciano Musa 3. Cooling issues from CMS experience (15') by Alain Herve 4. DAQ issues (15') by Xavier Janssen Summary: -------- 1. TPC-endcap issues. - We had three advanced-endcap meetings last year: 14 June, 26 July 2007 and 10 October 2007. The first two covered mainly the new electronics and the third included first thoughts by Luciano on the layout of and heat generated by the "advanced endcap" electronics. - There are three main, highly-correlated and sometimes self-contradicting aspects: electronics (as many pads as possible), cooling (as little heat generated as possible) and mechanics (as thin as possible). In addition there are two main developments: standard TPC or pixel TPC. - The density we choose will be governed by cooling (heat) and mechanics (X_0), as well as by the momentum resolution we want. How the problem was solved by Aleph was shown: 25% X_0 for 22000 pads and 1.3kW per side cooled using combined water and forced-air cooling. - The heat generated will depend not only on the electronic density but also on how well the power-switching works. If it turns out we are generating too much heat or the endcap is too thick due to electonic density, we will have to reduce the number of pads and there are ideas as to how to do this while maintaining the momentum resolution, but the price you pay is higher occupancy. =>=> However we don't want to consider this option yet, because we are still in the process of understanding the issues. 2. LCTPC electronics issues. Luciano reviewed the Alice endcap: 285000 pads per side, an order of magnitude more that Aleph. Whereas Aleph only had the preamps on the endcap, Alice has the whole PASA/Altro chain which sums up to 11kw per side to be cooled. Copper cladding of all the electronics and water cooling solved the Alice heat problem, but Alice does not worry about thickness of the endcap so that such a solution for the LCTPC is not possible. The strategy for LCTPC is that power pulsing will work and reduce the heat to a managable level. Luciano found that a density of 330000 pads per m^2 would be possible, based on preliminary layout of the PCB. He also showed first thoughts towards a power-pulsing circuit; if 1:100 power reduction can be achieved, that would leave 1.67 W/m^2 x 1/3 = 56 W/m^2 to cool for 1 million pads per endcap. Finally he said that a cooling layer can be included in the PCB. 3. Cooling issues from CMS experience. Alain reviewed the ideas used for CMS; these ideas are meant to open the discussion for the lctpc: - Each sub-detector is basically adiabatic wrt others. - The bulk of heat is removed locally by water as near as possible of where heat is created. Water is still the best liquid for that; there exist alternatives to water but they are expensive. - The remaining part of heat is removed by natural convection in the surrounding inert atmosphere; vacuum vessel and massive detector components are used as cold sinks. This is compatible with an inert atmosphere inside the vacuum vessel as required for fire protection. - Alain expressed concern that power-pulsing may cause problems for the mechnical stability of the detectors. 4. DAQ issues. Xavier dispayed first thoughts. - The advanced endplate electronics will be much more highly integrated than now and include more FEC and RCU functionalities. What is put on the endcap and what goes into the electronic hut must be decided. -For the several options for the advanced-endplate electronics, a common data transfer protocol and DAQ should be defined. -A "trigger" concept will be needed. E.g., the "trigger" should wake up the electronics before the bunch-train arrival and prepare for arrival of the data, and then put the electronics back to sleep after the bunch train has passed. -Also data transfer needs redundancy and Xavier showed the architecture being planned by CALICE.