PV-DIS Toroid Detector: outline and costs Paul E. Reimer 12 GeV PV-DIS detector meeting August 1.Introduction to Toroid Concept (presenting work done by Eugene Chudakov) See Eugene’s talk and 2.Detector Package (my rough guess) 3.Cost Estimate (my even rougher guess)

August 2008 Paul E. Reimer 12 GeV PV-DIS Large Acceptance Detector Toroid concept With long targets, the momentum can not be measured. Solution: Use two toroidal magnets: –TOR1: a strong magnet focusing the DIS electrons parallel to the beam; –TOR2: a magnet similar dimensions as TOR1, but weaker, providing the momentum measurement. Both TOR1 and TOR2 bend electrons toward the beam. Detectors are located between TOR1 and TOR2 and downstream of TOR2. Drawbacks –The need to build at least 1 new magnet—G0 magnet may work for 2 nd magnet –Limited to particles with one charge (a solenoid without baffles can take both) –Potentially larger error on the scattering angle. Tracking detectors screened from target. See Eugene’s page at

August 2008 Paul E. Reimer 12 GeV PV-DIS Large Acceptance Detector Toroidal Field Low current density High current density Low current density High current density Standard 1/R field will not focus particles of interest Constant field (e.g. dipole) provides better focusing The average azimuthal (along φ) field at a radius R is B  =  0 I/(2  R) = 2 £ I/R where R is the current flowing through the circle of radius R. The units are T, m, A. TOR1 needs a uniform field of 2.5 T at R= m. –Requires I=5 MA at R=0.4 m and I=18.75 MA at R=1.5 m, changing linearly with R. Wind coils with 1/R current density –Possibly use iron to additionally shape field For comparison, the G0 magnet uses a current of I=5.76 MA at R≅ m. Again, see Eugene’s work for more details

August 2008 Paul E. Reimer 12 GeV PV-DIS Large Acceptance Detector Toroidal Field ParameterG0 TOR1 IdealCalculation 1Calculation 2 Number of coils88812 Full current along Z at R=0.4 m5.76 MA5.00 MA Full current along Z at R=1.5 m5.76 MA18.75 MA Superconductor cable20 strands36 strands Cross section of the copper support cable20×5 mm²same Current density5000 A/cm²10000 A/cm² 6666 A/cm² Cable layers per coil4244 Coil cross section, at R=0.4 m8×18 cm²4×15.6 cm²8×8 cm² Full coil thickness in φ15 cm11 cm15 cm B φ at ≅ 0.4 m 2.88 T2.50 T2.30 T B φ at 1.5 m0.77 T2.50 T1.43 T1.64 T B max T5.5 T Full current density dI/dR at R= mnone125 kA/cm125 kA/cm ? Cables per unit length in R, at R= mnone0.78 per cm1.25 per cm Coil cross section, at R max ≅ 1.5 m 8×18 cm²4×60 cm²8×30 cm² Full number of turs per coil--196 Stored energy, MJ

August 2008 Paul E. Reimer 12 GeV PV-DIS Large Acceptance Detector Close to the coils, at the lower radii of R<100 cm, the field has a radial component. This component cases a "defocusing" of the trajectories at smaller scattering angles, moving them toward the coil. At larger angles some focusing occurs, with the trajectories moved to the center of the sector. The effect is illustrated on the next picture for the map (2), made with no absorption in the ideal TOR2 coils. The effect leads to a loss of acceptance, since some of the "defocused" electrons hit the coil of TOR2. The trajectories for DIS at φ=12°, 22°<θ<35°, 0.65;<x<0.85. The field map (1) was

August 2008 Paul E. Reimer 12 GeV PV-DIS Large Acceptance Detector

August 2008 Paul E. Reimer 12 GeV PV-DIS Large Acceptance Detector Kinematic Resolution

August 2008 Paul E. Reimer 12 GeV PV-DIS Large Acceptance Detector Momentum measurement Need trajectory and a point:

August 2008 Paul E. Reimer 12 GeV PV-DIS Large Acceptance Detector Detector Package Minimum needed for momentum measurement: –Trajectory on one side of the magnet and a point on the other –Select up stream for trajectory (smaller chambers) downstream for point Both preshower and shower detectors 2 x-y hodoscope arrays Cherenkov counter

August 2008 Paul E. Reimer 12 GeV PV-DIS Large Acceptance Detector Shower Pb-Glass calorimeter 10x10x40 cm 3 blocks –≈$0.764/cm 3 –Volume area ≈6,100 cm 2 x 40 cm deep ≈224k cm 3 –Cost per wedge ≈$187k Readout –66 channels –PMT, base, shield ≈$400/channel –ADC, Delay, Splitter, discriminator ≈$150/channel –Cost per wedge ≈$33.6k Total Cost –Cost per wedge ≈$223k –Total ≈$1.8M

August 2008 Paul E. Reimer 12 GeV PV-DIS Large Acceptance Detector PreShower Pb-Glass calorimeter 10x10x(35-60) cm 3 blocks (shorter off axis) Cost estimate from PrimEx Pb-Glass from ITEP –≈$0.764/cm 3 –Volume area ≈6,100 cm 2 x 10 cm deep ≈61k cm 3 –Cost per wedge ≈$46.7k Readout –16 channels –PMT, base, shield ≈$400/channel –ADC, Delay, Splitter, discriminator ≈$150/channel –Cost per wedge ≈$8.8k Preshower –Cost per wedge ≈$55.5k –Total ≈$444k

August 2008 Paul E. Reimer 12 GeV PV-DIS Large Acceptance Detector Drift chambers or MWPC Issue is rate capability vs cost –MWPC can take 10×rate (occupancy & faster gas) –MWPC cost more (Channels and recirc. gas syst.) Readout cost/channel Based on E906/Drell-Yan PreAmp$12.50 Custom FPGA- based readout $27.50 Total/channel$40.00 MWPCDrift Chamber Station1 or 23 3 ChamberPlane pair (y, y 0 ) $38k $30k y, y 0, u, u 0, v, v 0 $114k $90k Readoutchannels/ plane Plane$10k$20k$2k$4k Chamber$60k$120k$12k$24k Total/wedge$174k$234k$102k$120k Gas system$200k$50k 8 wedges$1.6M$2.0M$866k$961k Total$5.2M$2.7M Each station has y, y 0 u, u 0 and v, v 0 layers Stations 1 and 2: 100 cm < R < 150 cm Station 3 50 cm < R < 150 cm

August 2008 Paul E. Reimer 12 GeV PV-DIS Large Acceptance Detector Hodoscopes 10 cm wide x and y planes to match Pb-glass –≈$1,300 for scintillator, diamond milled for each layer (x or y) –≈$700 Light guide material for each layer Based on Spring ’07 quote for E906/Drell-Yan, but Scintillator is made from Oil—expect factor of 1.5 inflation –Cost per wedge ≈($1,300+$700) x 2 layers (x, y) x 2 stations x 1.5 inflation ≈$12k/wedge Readout –30 channels/wedge/station x 2 stations = 60 channels/wedge –PMT, base, shield ≈$400/channel –ADC, Delay, Splitter, discriminator ≈$150/channel –Cost per wedge ≈$27k Total Cost –Cost per wedge ≈$39k –Total ≈$312k

August 2008 Paul E. Reimer 12 GeV PV-DIS Large Acceptance Detector Cherenkov Counter Based on CLAS High Threshold Cherenkov for 12 GeV upgrade –≈$750k for 6 fold symmetry or $125k/wedge –Less contingency, etc (put these back in later) $125k/1.4=$90k –Smaller individual volumes and less complication $90k/2 = $45k/wedge Total Cost $360k for 8 wedges

August 2008 Paul E. Reimer 12 GeV PV-DIS Large Acceptance Detector Bottom line on cost without magnet ItemCost MWPCDrift Shower counter Pb-Glass$1,800k PreShower counter Pb-Glass$444k Tracking$5,200k$2,700k Hodoscopes$312k Threshold Cerenkov$360k Total$8,116k$5,616k Contingency factor × 1.3$10,551k$7,300k Inflation factor × (1.03) 2 = 1.06$11,200k$7,740k This could be too expensive Where can there be savings: Pb-Glass –Fewer radiation lengths? –In kind contribution from foreign source? Reduce tracking resolution –x, x 0, y, y PMT each –Do we need this granularity? –Can it be obtained more cheaply? 6 wedges rather than 8? –Fewer channels –Less uniform field Are all detector elements necessary? No attempt to reuse available equipment: –Tracking electronics, PMT, ADC readout, Scintillator? Caveat: This is a “straw person” cost estimate—meant to be shot down

August 2008 Paul E. Reimer 12 GeV PV-DIS Large Acceptance Detector Conclusion Toroid magnet concept can make appropriate measurements for PVDIS studies—see Eugene’s talk and Potential for other physics needs to be examined –Spectrometer can only focus one charge of particle at a time! Requires double toroid with nearly constant B field in each toroid –Done with multiple radius windings No complicated spiral baffles –No scattering from baffles Drawbacks: –Toroid fabrication possibly costly –Detector package possibly costly