PV-DIS Toroid Detector: outline and costs

PV-DIS Toroid Detector:outline and costs

Paul E. Reimer

12 GeV PV-DIS detector meeting

12-13 August

1. Introduction to Toroid Concept (presenting work done by Eugene Chudakov)

See Eugene’s talk and

http://www.jlab.org/~gen/jlab12gev/tor_sim/

2. Detector Package (my rough guess)

3. Cost Estimate (my even rougher guess)


212-13 August 2008Paul 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 2nd 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 http://www.jlab.org/~gen/jlab12gev/tor_sim/



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 isB=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


Toroidal Field

Parameter G0 TOR1

Ideal Calculation 1 Calculation 2

Number of coils 8 8 8 12

Full current along Z at R=0.4 m 5.76 MA 5.00 MA 5.00 MA 5.00 MA

Full current along Z at R=1.5 m 5.76 MA 18.75 MA 18.75 MA 18.75 MA

Superconductor cable 20 strands 36 strands 36 strands 36 strands

Cross section of the copper support cable 20×5 mm² same same same

Current density 5000 A/cm²10000 A/cm²

10000 A/cm² 6666 A/cm²

Cable layers per coil 4 2 4 4

Coil cross section, at R=0.4 m 8×18 cm² 4×15.6 cm² 8×8 cm² 8×8 cm²

Full coil thickness in φ 15 cm 11 cm 15 cm 15 cm

Bφ at 0.4 m≅ 2.88 T 2.50 T 2.30 T 2.30 T

Bφ at 1.5 m 0.77 T 2.50 T 1.43 T 1.64 T

Bmax - - 7.6 T 5.5 T

Full current density dI/dR at R=0.4-1.5 m none 125 kA/cm 125 kA/cm ? 125 kA/cm ?

Cables per unit length in R, at R=0.4-1.5 m

none 0.78 per cm 1.25 per cm 1.25 per cm

Coil cross section, at Rmax 1.5 m ≅ 8×18 cm² 4×60 cm² 8×30 cm² 8×30 cm²

Full number of turs per coil - - 196 196

Stored energy, MJ 7.6 - 52 45


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



Kinematic Resolution


Momentum measurement

Need trajectory and a point:


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


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


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



– Cost per wedge ≈$8.8k Preshower

– Cost per wedge ≈$55.5k

– Total ≈$444k


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

MWPC Drift Chamber

Station 1 or 2 3 1 or 2 3

Chamber Plane pair

(y, y0)

$38k $38k $30k $30k

y, y0, u, u0,

v, v0

$114k $114k $90k $90k

Readout channels/plane

250 500 50 100

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, y0 u, u0 and v, v0 layers

Stations 1 and 2:

100 cm < R < 150 cm Station 3

50 cm < R < 150 cm


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



– Cost per wedge ≈$27k Total Cost

– Cost per wedge ≈$39k

– Total ≈$312k


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


Bottom line on costwithout magnet Item Cost

MWPC Drift

Shower counter Pb-Glass $1,800k $1,800k

PreShower counter Pb-Glass $444k $444k

Tracking $5,200k $2,700k

Hodoscopes $312k $312k

Threshold Cerenkov $360k $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, 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?

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


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


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PV-DIS Toroid Detector: outline and costs