Alignment Requirements Introduction

1
Alignment RequirementsIntroduction

• General method in NuMI Note L-221
• (Oct. 96, old 3 horn beam)
• Medium Energy Beam in TDR sect 3.6
• Detailed data here for Low Energy Beam, but
  still
• Uncorrected PBEAM bugs
• Horn current assumed at inner radius of inner
  conductor
• Target width of 3.2 mm used (latest 6.4)

2
Beam Element accuracy requirements

• At low neutrino energies, the NuMI beam at the
  far detector is several kilometers wide, making
  it easy to hit with some neutrinos.
• Much more demanding is the physics (energy
  spectrum test) requirement to calculate the far
  detector spectrum (without oscillations) from the
  measured near detector spectrum.

If
3
Beam Element accuracy requirements

• Use PBEAM_WMC Monte Carlo program to find v
  energy spectra in the far and near detectors with
  an element aligned.

If element is offset by X, then FAR(X)/NEAR(X)
should have been used instead. Correction factor
RR
4
Horn 1 X2 mm Flux, Ratio at Detectors
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RR Horn 1 X2 mm
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Calculation Scheme

1. Select alignment reasonably achievable
2. Find Far Near Detector Spectra with everything
   aligned
3. Guess several displacements (x) of one element
   find spectra
4. Find RR for each displacement
5. Select peaks in RR
6. Fit RR (E peak) to Axp
7. Find RR variation at selected alignment accuracy
8. Repeat for all elements
9. Compare with 2 year run stats.

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Beam Position on Target Accuracy Estimate
Beam Position Chambers
Target

Beam
a
b
dxt transverse error at target dxc transverse
error at each chamber r b/a 9.65 / 14.63
0.66 dxt dxc 2r2 2r 10.5 Assume dxc
0.25 mm, then dxt 0.45 mm
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RR-1Beam X on Target
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6 GeVSensitivities
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Add Magnet Power Supply Regulation
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Conclusions

• Details are preliminary due to beam line changes
  PBEAM Monte Carlo difficulties.
• Assuming they add in quadrature, seven magnet
  strings that each produce a 0.25 mm error at the
  target are acceptable.
• Increasing this to 0.5 mm each stretches the
  tolerance budget.
• Anything more is not acceptable.