PV-DIS Toroid Detector: outline and costs

1. PV-DIS Toroid Detector:outline and costs Paul E. Reimer 12 GeV PV-DIS detector meeting 12-13 August Introduction to Toroid Concept (presenting work done by Eugene Chudakov) See Eugene’s talk and http://www.jlab.org/~gen/jlab12gev/tor_sim/ Detector Package (my rough guess) Cost Estimate (my even rougher guess)

2. Toroid concept • Tracking detectors screened from target. See Eugene’s page at http://www.jlab.org/~gen/jlab12gev/tor_sim/ • 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 2nd magnet • Limited to particles with one charge (a solenoid without baffles can take both) • Potentially larger error on the scattering angle. Paul E. Reimer 12 GeV PV-DIS Large Acceptance Detector

3. High current density High current density Low current density Low current density Toroidal Field • 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=0I/(2 R) = 2£ 10-7 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=0.4-1.5 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≅0.5-1.5 m. • Again, see Eugene’s work for more details Paul E. Reimer 12 GeV PV-DIS Large Acceptance Detector

4. Toroidal Field Paul E. Reimer 12 GeV PV-DIS Large Acceptance Detector

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

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

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

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

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

10. Shower • Pb-Glass calorimeter • 10x10x40 cm3 blocks • ≈$0.764/cm3 • Volume area ≈6,100 cm2 x 40 cm deep ≈224k cm3 • 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 Paul E. Reimer 12 GeV PV-DIS Large Acceptance Detector

11. PreShower • Pb-Glass calorimeter • 10x10x(35-60) cm3 blocks (shorter off axis) • Cost estimate from PrimEx Pb-Glass from ITEP • ≈$0.764/cm3 • Volume area ≈6,100 cm2 x 10 cm deep ≈61k cm3 • 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 Paul E. Reimer 12 GeV PV-DIS Large Acceptance Detector

12. 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.) • Each station has y, y0 u, u0 and v, v0 layers • Stations 1 and 2: 100 cm < R < 150 cm • Station 3 50 cm < R < 150 cm Paul E. Reimer 12 GeV PV-DIS Large Acceptance Detector

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

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

15. Bottom line on costwithout magnet • 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, x0, y, y0 • 1140 PMT channels @$550 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? Caveat: This is a “straw person” cost estimate—meant to be shot down • No attempt to reuse available equipment: • Tracking electronics, PMT, ADC readout, Scintillator? Paul E. Reimer 12 GeV PV-DIS Large Acceptance Detector

16. Conclusion • Toroid magnet concept can make appropriate measurements for PVDIS studies—see Eugene’s talk and http://www.jlab.org/~gen/jlab12gev/tor_sim/ • 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 Paul E. Reimer 12 GeV PV-DIS Large Acceptance Detector