E166 Background Test Simulations: Overview-what do we need J. C. Sheppard

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E166Background Test SimulationsOverview-what
do we needJ. C. Sheppard
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E-166 Background Tests

• Review and Advisory Committee
• Robert Noble (chair), C. Field, H. Lynch, and M.
  Ross
• Design a test in the FFTB to validate that the
  backgrounds in E-166 are acceptable
• Review results and recommend to Dorfan and
  Paterson to proceed with E-166
• E-166 to be run in early calendar 2005
• Background results roughly by end of calendar 2003

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E-166 Beamline Schematic
50 GeV, low emittance electron beam 2.4 mm
period, K0.17 helical undulator 0-10 MeV
polarized photons 0.5 rad. len. converter
target 51-54 positron polarization
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E166 Polarimeter Overview

g Polarimeter
4 x 109 ? ? 4 x 107?
1 x 1010 e- ? 4 x 109 ?
4 x 109 ? ? 2 x 107 e
4 x 105 e ? 1 x 103 ?
2 x 107 e ? 4 x 105 e
and Polarimeter
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E-166 Background Tests

• There are three sources of E-166 background
• Streaming from up-beam of the undulator
• Interception at the undulator
• Secondaries produced in the spectrometer
• Background studies test the first two sources
• First meeting of RA committee June 26, 2003

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E-166 Background Test, June 2003
Shielding to be added as indicated by modeling
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E-166 Background Test, now
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E166 Background Test Goals
The goals of the E166 Background Test are to
transport a low emittance beam through a small
aperture tube located at IP1 in the FFTB and to
measure the background levels at the locations of
the E166 detectors. Success for this test is
demonstrated by being able to keep the beam on
with the small aperture tube in place (loss
levels below the FFTB radiation limits) and by
measuring the background levels at each of 5
detectors to be less than 5 of the signal levels
anticipated for E166 proper.
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E-166 Background Test
For the background tests, a beam energy of 28 GeV
is sufficient. A 1.2 mm id1, 1 meter long, thin
walled SS tube and a protection collimator will
be installed at IP1. Five detectors two
Cerenkov-aerogel flux counters, a Si-W
calorimeter, a Si-Pad calorimeter, and a CsI
calorimeter will be located about 35 m downstream
of IP1. Figure 1 shows the approximate layout of
the required equipment in the FFTB enclosure.
Shielding for the detectors, including Fe blocks
representing the E166 magnetized absorbers, for
the background tests is commensurate the full
E166 experiment. Table 1 lists the expected E-166
signal strengths and 5 background levels
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E-166 Background Tests
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1. The 0.9 mm aperture of the E-166 undulator is
scaled inversely with the square root of the beam
energy from the 50 GeV of E-166 proper to the 28
GeV of the background test. Thus
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E166 Background Tests, Simulations

• Questions for the Simulations
• How much lead
• How much Boron-Polyethylene
• How much blasts thru the 3 mm hole
• Do we need floor, ceiling, side wall shielding
• What is expected change from 28 GeV to 50 GeV
• We are concentrating on beam splat on the
  undulator tube and collimator, ignoring
  essentially everything else (upstream sources,
  synchrotron radiation, ). Are we fooling
  ourselves?