Minutes of the CALICE-UK Steering Board meeting, UCL, 28/07/04 ============================================================== Present: Jon Butterworth, Paul Dauncey, David Ward, Nigel Watson By phone: Chris Hawkes, Matthew Wing Minutes: Paul News: For the ECFA Durham meeting, Nigel has been told by Ken Peach that we can charge travel (only) to the CALICE-UK budget if there is a CALICE-UK meeting during the workshop. We will be having such a meeting. In addition, Paul has been asked by Jean-Claude to try to get as many UK people as possible to volunteer for presentations. Everyone should persuade the people in their group to sign up. As part of the last round of GridPP2 posts, Imperial gained a "portal" post, for which some fraction is for expanding the Grid to smaller experiments. CALICE is named specifically (with Dark Matter) as an experiment which should be helped by the person in this post. Interviews to fill the position were held last and this week and an offer will be made very soon. The first thing to get the person working on is to try and put the MC into shape to generate large datasets. It will also be useful to get the first level raw data to LCIO processing step automated. The latest draft (V6) of the MoA is available on the web site. This is similar to the previous version and, although it has a few gaps, is getting close to completion. Future plans: There are four possible strands for the future bid: o On/off detector electronics o Monolithic active pixel sensors (MAPS) o Plastic semiconductors o Thermal mechanics The context is that, although the LC seems far off (2015), the technology choice needs to be made by the time of the TDR (2009) so that final system prototyping can be done in 2010-2011 and calorimeter construction can begin in 2012. This gives only five years to have a verified technology. On/off detector electronics: This had been mainly discussed in the morning meeting, for which minutes can be found at http://www.hep.ph.ic.ac.uk/calice/elecLongterm/040728ucl/minutes.txt There seem to be several places where it is reasonable to start R&D now and there is also some enthusiasm to do so. Hence, this area is likely to form at least part of the future bid. Monolithic active pixel sensors: Paul has been investigating the technical aspects of MAPS. There is a strong UK group in this area lead by Renato Turchetta at RAL/TD. Paul was connected to him by Geoff Hall at Imperial who is interested in MAPS for SLHC work. Paul send Renato a draft of the MAPS discussion document which was distributed at the last SB meeting and this was not dismissed out of hand. Renato has expressed some interest in pursuing this further and so Paul is trying to arrange a meeting. Unfortunately, due to holidays, etc, this is likely not to be before the second half of August. The outstanding issues for our use for which we need answers seem to be: o The readout time (effectively the time resolution): for the warm machine case it would need to be of order 1ns to resolve the warm machine crossings. o The noise suppression: for a threshold on a MIP, we would need a noise rate of order 10^{-6} to reduce the data rate to something reasonable. o The pixel size: the pixel S/N drops as the pixel size increases. We would like to aim for pixels at least 50x50 microns^2, if not 100x100 microns^2. To make any bid feasible, we would need to do simulation work to show in which areas MAPS give a significant improvement (if indeed they do at all). Initial guesses were that fast MAPS (i.e. high speed readout) would clearly help with gamma-gamma minijet pileup event rejection at a warm machine. Also, the much finer pixel sizes might help significantly in the endcap for boosted events such as WW, where the jet density is higher. Chris Ainsley has been doing a lot of the relevant work within the UK but he is leaving Cambridge in mid-August to move to the US. He will continue to work remotely until around the end of the year. Ideally, the simulation would check the following properties: o The pixel size needed to really reduce the probability of two or more MIPs within one pixel to a negligible level. This should be judged on high energy hadronic jets, not Bhabhas, as some saturation would be acceptable in the latter. The working assumption on size being considered for electronics discussions is around 50x50 microns^2, which results in 40k pixels per standard pad. Chris Ainsley was going to study the effect of pad size and so this could be covered by him. o The change of reconstruction efficiency and purity (as defined by Chris Ainsley) for Z events (mainly barrel) and W events (mainly endcap) when using pads or pixels. o The change of reconstruction efficiency and purity due to mixing in minijet events and hence the effect of the timing resolution. This will be best done by mixing the ascii file outputs after the events are separately simulated. Matthew has generated such events and thinks this should be straightforward. Clearly, overlaying extra events will degrade any missing E_T measurement; however it was not known what are the benchmark physics processes which require good missing E_T resolution (SUSY?). Unfortunately, due to the way the pad numbering is stored in Mokka, it is not completely trivial to implement much smaller pixels in the simulation. It was also not clear how much work would be required to overlay minijet events, particularly if they were to be offset in time. Nigel had asked Ken Peach for some MAPS effort as part of the RAL "New Initiatives" funds and had not had a favourable reply. We will aim to get as much of the technical and simlation work done as possible by the end of September so that a decision on whether to include MAPS in the bid can be made then (see below). Plastic semiconductors: Nigel had discussed this with some people at RAL. Two recent technical reviews there had not indicated this as a possible research area in the future. A RAL spin-off start-up company, Printable Field Emitters, which had been looking into flat display screens, had recently folded. From looking through the journal EE Times, Nigel had concluded that an initial burst of activity around five years ago had reduced over the last few years. David reported that he and Mark Thomson had met with the head of the microelectronics group at Cambridge, where plastic semiconductors had first been discovered. The typical thicknesses are a few 100's of nm to a few microns, made by evaporating solvent onto a subtrate. The usual uses are light emission (for flat screens) or light detection. For our purposes, a thickness of at least 100 microns, if not a mm, would be needed to get a significant energy deposit compared to a silicon detector, particularly when the lower Z of the plastic (mainly carbon and hydrogen) is considered. In addition, the mobilities are low, with values of 10^-2 to 10^-1 cm^2/Vs given in an article Nigel had with him. Translating this to a speed for a 100 micron detector with 100V across it (a reasonable bias which would not involve too many HV complications), then this gives speeds of 10^2 to 10^3 cm/s and so would take 10^-4 to 10^-5 s for the charge to cross the detector. This seems slow even for the cold machine with 337 ns crossing times. Paul had met with a member of the Imperial group working on light detectors with plastic semiconductors and had heard similar things. It is possible to get much higher mobilities but this requires the plastic to be made as a crystalline material, i.e. not amorphous. This is of course much harder to do and would push the manufacturing cost up enormously, which removes one of the main motivations. The conclusion seems to be that this technology is not yet mature enough to be a viable choice within five years. Longer term, it does look interesting and the Cambridge group may pursue it as a blue-skies project, but this would not be done within the context of the LC bid under discussion. Thermal mechanics: Paul had had a talk with Roger at SLAC the week before to see where Manchester's interests were. Roger had said, given the experience of the people involved, they would fit in best with a mechanics involvement. Specifically, the issues are to do with the thermal properties of the mechanics and how to cool any electronics on the wafers. Ian Duerdoth did some work in this area earlier on in CALICE. However, before committing to anything, Roger really needs to wait until he is back from his LTA, which ends in August, so he can discuss a future direction with the Manchester group. It was thought that it would be perfectly acceptable for there to be a mechanical R&D part to the bid and so if Manchester wanted to take this further, this would be supported by the other groups. It would of course look more balanced if there was another group besides Manchester involved in this side of the bid. However, the groups represented at the meeting (Birmingham, Cambridge, Imperial and RAL) all thought an electronics project would be more suited to their strengths. It is of course not excluded that we try to involve a new group and certainly if Manchester want to pursue a new direction, we should encourage them to investigate other partners also. Timescale for bid: One of the main factors pushing for an early submission of the bid is the extension of the George Mavromanolakis post. This runs out in August 2005 and it would be good to confirm its extension before Easter so that he doesn't start applying for other jobs. He seems to be enthusiastic about staying in the LC area and getting involved in the test beams, so he is likely to stay for the third year if we can get the extension. It was thought that the bid should clearly separate the two components, i.e. the completion of the original CALICE bid and the future program. The idea here would be that, even if there is some prolonged discussion on the shape (and hence delay on the approval) of the future program, we could ask that the CALICE completion part is approved on a shorter timescale so we can continue to exploit the investment already made. The CALICE completion would now have to cover two FYs, not just one, as the HCAL delays have meant it is unlikely the test beam analysis will be complete before the end of 2006. However, this part of the bid will have no equipment or TD component; it will be for the extension of George Mavromanolakis' post and for travel. The former will be for around 45k and for the latter, something like 70k for FY05/06 and 40k for FY06/07 would be appropriate, so the extra FY will be a minor part of the total. Jon thought getting the bid through would not be too difficult as long as we brief the relevant people about what to expect in advance. The LC is a major part of PPARC's future program and we are expected to return with a long-term bid so this is all in our favour. It is clear that not approving the remaining part of the CALICE bid would be a major embarrassment to the UK as it would have to withdraw from the collaboration after having already built all the equipment. It is hard to see why this part would be turned down unless there is a complete disaster with the electronics board production, which is due to start next month and so should be completed before any bid is submitted. Jon also mentioned that LCFI recently got 900k for the next year as "bridging funds" to keep them going until the warm/cold machine decision is made. On this scale, our bid should appear relatively minor. It would clearly be advantageous to have some positive results from the electronics before the new bid is considered. There will be single-stack cosmic tests (i.e. ten silicon layers) in October, which will be followed by a DESY electron beam test in November. This test will start with a single stack but should build up to two and then all three stacks in December and January, respectively. Clearly, even single-stack beam test event displays would be extremely useful to show in any presentation to the PPRP and/or Science Committee. It was decided that the bid should be submitted so it can be considered by the PPRP at the end of January. This is in line with their expectations and also gives us some extra time to sort out the various areas under discussion. This is somewhat late with regard to George Mavromanolakis' extension, but given the plan to try to minimise delays in approval for this part of the bid, David was prepared to go along with this schedule. This means the written bid will need to be submitted sometime in December. To meet this timescale, we need to make a decision on MAPS by the end of September, as mentioned above. Obviously the electronics and mechanics aspects need to firmed up around the same time also. Jon, as Chair of the PPRP, said he would accept this as sufficient notification for the PPRP. Next meeting: There will be an informal CALICE-UK meeting at Durham; Nigel, David and Paul will be there, but not Chris, Matthew or Jon. Whether anyone from Manchester will go is not known; given their LC-ABD involvement, it is likely someone will be there. In addition, at least Mark Thomson and Dan Bowerman will be going. The next CALICE-UK SB meeting proper will be at UCL on Oct 7 or 8 (TBD).