Future%20Spectrometer%20for%20Hall%20A

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Future Spectrometer for Hall A

• John LeRose
• Hall A Collaboration Meeting
• 6/24/2005

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History

• We Approached The Budker Institute re a
  collaborative arrangement for building the MAD
  (and SHMS)

• They came back with a report suggesting a
  purely quadrupole design.
• Magnets would be cheaper and easier to build
• Performance would be similar to MAD

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On the optics of the SHMS and MAD
spectrometers I.A.Koop, D.M.Nikolenko, BINP,
Novosibirsk, Russia
1 Introduction. Making tracking of the scattered
electrons through the optical system of the SHMS
spectrometer 1 authors find out that often the
phase space portraits of rays with different
momenta overlap, as it is illustrated in the
Figure 1. Optics parameters of the SHMS
spectrometer were taken from the Table 34 of 1
for the Large Solid Angle tune. For convenience
they are listed below in the Table 1.
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From the Budker report
Figure 6. Trajectories of electrons with energies
ranging from 25 up to 25. For compactness
here are shown superimposed views in (x,s) and
(y,s) planes. The scattering angles are x200
mrad, y35 mrad. The proposed optical system (a
doublet of quads) provides unambiguous
reconstruction of a particles momentum. This is
because of essentially different position of the
crossovers of rays with different energies. The
flux of ?-rays, that comes from the target
region, will be intercepted by a stopper, which
presents a trapezoidal plate extended in the
y-direction. Such absorber also intercepts
electrons with angles xlt65 mrad. In the
y-direction there is no any screening for
electrons, because their trajectories are
traversing above or below the stopper.
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Even Less Expensive!

• We have large bore, high field gradient
  quadrupoles already (Q2 and Q3)
• What do we get if we make such a device using
  them?

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Cost (from Paul Brindza)
Direct Cost Items 2Q "Lite" 2Q "Heavy"
Electrical Dismantling 10 20
Plumbing dismantling 10 20
Remove Q2Q3 110 110
Cut carriage NA 50
Remove Dipole NA 90
Temp support box beam NA 50
Remove jacksburnout stands NA 50
Dis assemble dipole and rig out NA 80
Fabricate Box Beam supports NA 120
Install new Box beam support NA 50
Re-weld carriage NA 50
Remove Link 4 NA
Re-attach link 6 NA
Remove Inner Drive Bogies 8 NA
Re mount Drive Bogies 12 NA
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Costs continued
Intermediate Hillman Rollers 30 NA
Fabricate Carriage 40 NA
Fabricate Beam legs 35 NA
Fabricate Q3 Hanger 25 25
Fabricate Q2Q3Cradles 5 5
Assemble carriage,beam legs 22 NA
Install quads 22 NA
Fab new detector stand 35 35
Electrical Installation 10 10
Cable tray and installation 5 5
Plumbing installation 10 10
Cryo Gas Lines Materials 20 NA
Fab new Q2Q3 Transfer line 40 NA
Fab Q2Q3 vacuum connection 10 10
Fab Entrance Exit window 20 20
Fab New Sieve slit 40 40
Total Cost K 529 850
doesnt include Hall A labor or detectors
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Acceptance
-25 lt d lt25 P0 8.8 GeV/c
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Multiple Scattering etc. _at_8.8 GeV/c
8800 MeV/c
RL q0 length sy sq
Helium bag 0.155 0.000046 8.8 m 0.00023 m 2.65E-05
Bag exit window 0.009 0.000009 0.3 m 0.00000 m 5.43E-06
Air between exit and chambers 0.099 0.000036 0.3 m 0.00001 m 2.06E-05
1st chamber 0.100 0.000036 0.0 m 0.00000 m 2.08E-05
Air between chambers 0.329 0.000069 0.0 m 0.00000 m 4.00E-05
chamber Intrinsic 0.00008 m 1.10E-04
quadsum 2.45E-04 1.24E-04
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Resolution
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Detector Size
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Summary Q2 Q3 Spectrometer

• Comparable to MAD in momentum, position, and
  angular resolution
• Uniform acceptance
• Large momentum range (25)
• Extended targets (at least 20 cm)
• But very small ?O and no in-plane acceptance
• Inexpensive, compact, lightweight
• Is the background manageable?
• Do we want to give up the right HRS?