Answers to Reviewer Comments & Questions DC56 Review at CERN, November 14 th, 2012 Matthias Grosse Perdekamp, Illinois For comments and questions concerning FEE & DAQ see Wen-Chen Chang’s slides Comments from (I) Hans Danielsson (II) Igor Konorov (III) Fulvio Tessarotto

2 Comments from Hans Danielsson DC56 Review at CERN, November 14 th, 2012 (1) Material Specifications The main issue is the validation of the cathode material and its manufacturing. What is the plan to validate the cathode material before production? We propose utilizing the graphite coating method used for PV2 and P4567 MWPCs in NMC/SMC (several layers of polished graphite spray). None of these chambers had problems with graphite wear on the cathode planes (or C- deposits on the sense wires). Prototype B will be using the cathodes we intend to use for DC56. We will test prototype B from 3/1/2013 to 6/30/2013 under (partial) radiation exposure and HV and will examine the cathodes after this test for signs of wear and search for Carbon buildup on the sense wires. CF4 is part of the proposed gas mixture. Is there a plan to perform aging/etching tests on wire and other components? We will test prototype B from 3/1/2013 to 6/30/2013 under (partial) radiation exposure and HV and will examine also the anode wires after this test. The anode wires will be inspected for alteration of the surface, deposits and we also plan to analyze the composition of possible deposits found. During the construction it is planned to inspect each wire delivery from Luma for integrity of the gold plating on the sense wire (with an electron microscope).

3 Comments from Hans Danielsson DC56 Review at CERN, November 14 th, 2012 (2)Detector operations What are the consequences if one or several wires brake (performance, repair)? we will loose a whole plane. DC456 have 24 planes, 6 of each projection, and the impact of one lost plane does not significantly change the tracking performance. Based on DC4 experience we do not expect more than 1-2 wire breaks/year. The repair can be carried out in the clean area next to the COMPASS hall. Based on experience with DC4 the repair takes several weeks and will be carried out between runs. What is the maximum particle flux /cm^2 in the hottest region? about 4kHz/cm-wire or 5kHz/cm^2 near the beam killer (190kHz for GPD running for the whole wire). The occupancy will be 1.4%, less than the 3% required to meet COMPASS specs for tracking. What is the expected integrated charge/cm on the hottest wires? The combined accumulated charge for DVCS + DY will be 15mC/cm-wire. What are the corresponding values for DC04 until today’s date? The combined accumulated charge DC4 is about the same, ~17mC/cm-wire.

4 Comments from Hans Danielsson DC56 Review at CERN, November 14 th, 2012 (3) Mechanical design While profiting from existing design (DC04), some improvements and modifications for DC56 are proposed. Concerning the integration and of the modification in the design; Do the prototypes DC56 A & B contain the proposed modification in the grounding scheme (from DC04)? The grounding scheme will be basically identical to DC4 and it is planned that prototype B will have this grounding scheme for realistic tests of the new front end electronics. We also plan to test the DC56 FEE with an original DC4 prototype from Saclay. (Some change in the grounding will be to improve the shielding against noise from nearby detectors).

5 Comments from Hans Danielsson DC56 Review at CERN, November 14 th, 2012 (4) Front-end electronics The CMAD is the base line for the front-end electronics and as was pointed out in the meeting, it is most urgent to validate the performance on a realistic prototype (DC56-B?). Given the status of the FE today, it looks optimistic to solve all the issues in one iteration. What is the back-up solution if the CMAD is not suitable for the proposed detector? The CMAD chip will be tested with prototype B and also with the Saclay DC4 prototype (existing prototype at Saclay with long wires). If the CMAD chip is not suitable for the proposed detector we plan to test an alternative chip. Candidates include NINO (ALICE RPCs), CARIOCA (LHCb, muon MWPCs) and ASCQ (SeaSquest drift chambers). See Wen-Chen’s slides for details. Following the reviewer comments an additional iteration was added to the R&D schedule for the FEE.

6 Comments from Hans Danielsson DC56 Review at CERN, November 14 th, 2012 (5) Manpower and planning The definition of responsibilities for mechanical design and integration is important given the tight schedule and the geographical dispersion of the different activities in the project. What is the profile (technician, engineer, physicist) of the manpower (the 8 FTEs)? 2013, 2014 electrical engineering physicists on electronics mechanical engineering design engineer technicians physicists + students total Is the person responsible for the integration (mechanics and electronics) identified? The person responsible for the overall integration is a UIUC postdoc who is assigned to 80% to the DC56 project. The postdoc has extensive experience with two instrumentation projects in PHENIX. Senior consultants are Alain Magnon, Dominique Durand and Matthias Grosse Perdekamp

7 Comments from Igor Konorov DC56 Review at CERN, November 14 th, 2012 DC56 front-end electronic design is based on CMAD4 preamplifier-discriminator chip. The chip was optimized for photomultiplier and it has not been tested with drift detectors. An information available to reviewers does not allow to conclude whether the ASIC will allow to achieve 200 um space resolution in high intensity muon beam condition and whether its performance will not be affected by ion drifts. Therefore it is advised to perform real detector performance measurements. In case of not satisfactory results one may consider an alternative solution. Real detector performance measurements will be carried out with the existing Saclay DC4 prototype and the protoype B. Alternative frontend chip candidates are NINO (ALICE RPCs), CARIOCA (LHCb, muon MWPCs) and ASCQ (SeaSquest drift chambers). A 3 rd iteration was added to the FEE R&D See Wen-Chen Chang’s slides for more information.

8 Comments from Fulvio Tessarotto DC56 Review at CERN, November 14 th, 2012 (1)Chamber basic design, components and mechanical structure Are all basic parameters and material choices identical to DC4? Yes, with the exception of the cathode graphite coating. Will wire material quality and winding tolerances be at least as good as DC4? Yes, we will obtain material Q&A procedures and criteria from Saclay and will meet DC4 standards. Cathode production is a critical point: a more detailed plan for graphite coating study and a clear definition of the validation protocol would be useful. We follow the cathode design for DC4, except for the graphite coating of the mylar foils. We will use a coating method that was used for PV2 and P4567 MWPCs in NMC/SMC (polished layers of graphite spray). None of these chambers had problems with “graphite wear” off their cathode planes. This will be tested with prototype B. When and how will the final cathode quality be verified? Prototype B will be using the cathodes we intend to use for DC56. We will test prototype B from 3/1/2013 to 6/30/2013 under (partial) radiation exposure and HV and will examine the cathodes after this test for integrity (and the wires for C deposits)

9 Comments from Fulvio Tessarotto DC56 Review at CERN, November 14 th, 2012 (1)Chamber basic design, components and mechanical structure Are the beam killing regions and HV distributions different from DC4? We are planning to use very similar beam killers. The HV distribution may change. Is the mechanical structure design decoupled from the front-end finalization details? Yes, after finalizing FEE board sizes and needs for power bus, cooling and grounding. How many spare components are included in the plan? No spares kept for mechanical detector parts after installation. Two working spares for each type of LV or HV power supply. One working spare for each type of flow controller. 10% working electronics cards 10% spares for cables and fibers used [Comment: we believe that the most important improvement needed in the DC4 design is the improved rigidity of the support frames]

10 Comments from Fulvio Tessarotto DC56 Review at CERN, November 14 th, 2012 (2) Operating conditions in COMPASS Is the proposed increase of a factor 2.5 in average gain with respect to DC4 needed? The HV/gain only will be chosen after a combined test of the final FEE prototype and prototype B. The gain will be set as low as possible while still achieving high efficiency and good position resolution. We hope to achieve the DC4 gain but carry out simulations at various settings. It would be nice to see a comparison of the expected particle flux, in particular at the border of the future beam killing region (is it 30 cm diameter?) with the limit rates for the detector and the read-out. The maximum rates will reach ~4kHz/cm near the beam killer (190kHz for GPD running for the whole wire). The occupancy will be 1.4%, less than the 3% required to meet COMPASS specs for tracking. The combined accumulated charge for DVCS + DY will be 15mC/cm-wire. Have the modifications to COMPASS mechanical support structures, gas, power and cooling systems been taken into account in the plan? A detailed plan for the detector integration has to be developed. The estimates for schedule and cost for the integration are based on DC4 experience. Why are time resolution of 1 ns and position resolution of 200 microns needed? This is driven for the resolution in the kinematics for exclusive and semi inclusive physics (eg. smearing at low x) and not by Drell-Yan physics.

11 Comments from Fulvio Tessarotto DC56 Review at CERN, November 14 th, 2012 (2) Operating conditions in COMPASS What is the impact of the chamber response deterioration on the proposed physics program? DC56 replace straw stations 2 and 3. The straw detectors have temperature dependent high voltage instabilities that force certain areas of the detector to be switched off permanently and other significant parts of the detector are turned off and on depending on temperature. Operation of the detectors with stable acceptance is not longer possible. The Drell-Yan physics program is luminosity hungry and DC56 will provide time independent large acceptance. We hope to avoid aging effects in DC56 for the duration of the COMPASS II physics program. Have the installation, commissioning and operating responsibility efforts been evaluated? Installation & commissioning will be shared by the collaborating institutions. Operations will be largely carried by UIUC and Academia Sinica. For installation, commissioning and operation, UIUC plans to station one research assistant professor, one postdoc and 2 graduate students at CERN for the duration of the COMPASS II running. (3) Electronics  see Wen-Chen Chang’s talk!