Report of Muon Veto Task Force L. Littenberg 9 June 06

Muon veto task force Set up at Feb 06 collaboration meeting Kwong Lau, LL, Changgen Yang Communication via & SKYPE Previous report in 7/8March Conf Call

List of Requirements Cost Efficiency Other interactions with the water Cerenkov Physical configuration Calibration scheme Access to central detectors Robustness Mean time between failures Environmental interactions Maintenance Stability of response Uniformity of response Threshold for muons Rate from ambient radiation at threshold Noise rate at threshold Accidental veto fraction Time resolution Pulse shape

Requirements - 1 Cost –Scint. option is $3.8M in db_cost_3.xls, what’s the limit? Efficiency –At least three different statements in the proposal V3.2. –We’ll take goal of 99.5% for H 2 O + tracker If H 2 O 95% efficient, tracker must be 90% efficient, etc. Other interactions with H 2 O veto –Could add veto when  -tracker and H 2 O both have activity below normal thresholds. Would make determining efficiency harder –Could try to handle stopped  by vetoing on 1  -counter + H 2 O

Requirements - 2 Physical configuration –Feedback situation Calibration scheme –Can exert constraints on veto system Access to central detectors –Need to go in to maintain or move –Top (or side) needs to be open-able If can’t move as 1 piece, some elements must be movable Robustness –Can’t be too fragile to deploy, move to open, take pressure Mean Time Between Failures –Part of robustness, also related to maintenance –Sample calc for tracker: Want >95% efficiency, have 600 elements, can’t fix for 3 years Can stand average of 30 dead elements ~ 20/year Translates into MTBF of 30 years for single element If never want <95%, MTBF must be 60 years for single element If can get in once/year, MTBF goes to 10 (20) years

Requirements - 3 Environmental interactions –Leakage (H 2 O in, LS out) (for scintillators) - probably OK –PMTs in water (for scintillators) - same problem for WC –Sensitivity to temperature, humidity (for RPCs) –Could RPCs be encapsulated & placed in water? Maintenance –Continuous, such as gas supply for RPCs –Sporadic, such as fixing or replacing elements Stability of response –Must be monitored at least –Quantities not in trigger infrequently corrected –Timing an issue unless we have transient recorders Uniformity of response –For long scintillators need to hear from both ends for timing, possibly position (for single layer) –Must be monitored to keep track of efficiency

Requirements - 4 Threshold for muons –Degree to which signal can be distinguished from noise, radioactivity E.g. scint 4cm thick so muon drops 8MeV, & response is 4p.e./MeV Then if radioactivity < 2.5 MeV, game is to distinguish 32 from 10 p.e. If all guassian, 17.5p.e. would give 98% efficiency & reject >98% bkgnd But response a function of position! Rate from ambient radiation at threshold –Depends on intrinsic radiation at site as well as technology of veto Noise rate at threshold –Function of the technology, temperature, etc. Accidental veto fraction –Calculable from rates & resolution –Bottom-line quantity on which requirement imposed What is goal? What is acceptable? 1%? 1.5%? Need separate goal for precision of determining this quantity. –Can be different for near and far halls!

Requirements - 5 Spatial resolution –16cm mentioned, but not somewhat soft –Depends on details of possible systematic checks E.g. want to force  ’s through Gd-doped region Time resolution –Driven by requirement that two muon counters (& 2 ends) in coincidence Coincidence between veto and signal can’t be tight (-400 to 100  sec) –10ns ansatz Pulse shape –I.e. double pulse resolution –Issue is confounding of muon coincidence by an early random –Transient recorders would solve –High threshold also would solve

With no agreed-on configuration… Still many active options for configuration –Classic water pool (see Changgen’s talk) –Aquarium (figure in P5 talk) –Shipping container option Pipe variation (M. Diwan) –Hybrid solid/water shield (see next slide) –etc. Can take a couple of paths -- –Explore (& cost) technology options 0th level costs of proposed options R&D on option Develop an existence-proof (strawman option) –Examine back-pressure veto design exerts on possible configurations (see Changgen’s talk)

Hybrid shield - Kwong Lau ~30m

Strawman Activities Define configuration - 15m  15m  9m far hall pool, 15m  9m  9m near halls, 6 sides, 2 layers (x & y), pmts for active water shield looking inward Define counters - 1  10  750cm (mainly) extruded polystryrene scintillator read out by 2 1mm wls fibers on each end. Fibers multiplexed 8:1 into M4 pmts, differently on the two ends for unique ID Determine cost - a continuing, iterative process (initial cut ~$4M) Design support system - Initial mechanical design under way (by BNL Magnet Division M.E. Kuo-Chen Wu) Test prototypes - several 7m MINOS prototypes from FNAL on order - will vary readout scheme Simulate counters to guide design (get feedback) Object - demonstrate a technically viable system at affordable cost

Cost for scintillator strip option Counters (6800) - $1.39M PMTs (425 M4) - $0.42M Electronics (1700 ch) - $0.43M Packaging & support str. - $1.35M Shipping & installation - $0.38M Total - $3.97M

Scintillator Strip Simulation N. Tagg (in charge of MINOS counter simulation) now joined 1st job - can we understand performance of extant counters?: MINOS OPERA

Cost of LS version 5cm 50cm Liquid $2.5/l) - $0.32M Liquid handling, filling, etc. - $0.35M Modules (inc. wls fibers, etc., 696) - $0.83M PMTs, bases, cables (EMI-9913B) - $0.98M Electronics - $0.35M Support, etc. - $1.15M Shipping & installation - $0.55M Total - $4.53M Notes: no multiplexing, BNL labor rates

RPC R&D in the US Houston, Illinois, UCLA Performance validation of full-size prototype –Signal integrity –Stability –Uniformity –Sensitivity to gas mixtures –Shielding issues

Activities in China Tests of 3-layer RPC setup –Evaluated 2 of 3 selection Simulation work on 10m-long water Cerenkov tank (see talk on this subject) Preliminary mechanical engineering design work on mechanism for moving the top detectors in water pool scheme Design work on water Cerenkov tank in water pool scheme.

Summary We’ve been refining the requirements Developing strawman plastic scintillator system for technical and cost assessment –Prototype studies –MC –Engineering Would like to do something similar with LS –Need more manpower US R&D on RPCs scheduled Work in China on RPCs & configurations Next goal: better integrate collaboration-wide effort Must get input for hall design & get ready for CD1!