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E-166 Experiment

E-166 Experiment. E-166 is a demonstration of undulator-based polarized positron production for linear colliders. E-166 uses the 50 GeV FFTB beam in conjunction with 1 m-long, helical undulator (  = 2.4 mm, ID = 0.9 mm) to make 10-MeV polarized photons. These photons are converted in a

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E-166 Experiment

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  1. E-166 Experiment E-166 is a demonstration of undulator-based polarized positron production for linear colliders. • E-166 uses the 50 GeV FFTB beam in conjunction with 1 m-long, helical undulator ( = 2.4 mm, ID = 0.9 mm) to make 10-MeV polarized photons. • These photons are converted in a ~ 0.5 rad. len. thick target into e+ (and e-) with ~ 50% polarization. • The polarization of the positrons and photons will be measured. • E-166 was approved in June 2003, for a main data run in 2005.

  2. E-166 Collaboration (47 Collaborators) (16 Institutions)

  3. E-166 Beam Measurements • Photon flux and polarization as a function of undulator K • (Pg ~ 75% for Eg > 5 MeV). • Positron flux and polarization vs. energy for K = 0.17, 0.5 r.l. of Ti • (Pe+ ~ 50%). • Positron flux and polarization for 0.1 r.l. and 0.25 r.l. Ti and 0.1, • 0.25, and 0.5 r.l. W targets. • Each measurement is expected to take about 20 minutes. • A relative polarization measurement of 5% is sufficient to • validate the polarized positron production processes. • The undulator will be pulsed in a random pattern of beam pulses • to permit continuous monitoring of undulator-off background levels.

  4. E-166 Undulator(built at Cornell U. by Mikhailichenko) Two helices wound on a 0.9-mm ID, 1-m-long hypodermic needle. 1.4 kA pulses, ~ 5 μs long provide field of ~ 1 T on axis,  k ~ 0.15.

  5. Positron Spectrometer(magnets built at Princeton)

  6. Aerogel Cerenkov Counters(built at Princeton) Two Cerenkov counters with aerogel of index n = 1.0095 are now in the FFTB tunnel. Index measured with a Michaelson interferometer.

  7. Preliminary Results from Runsof E-166 in June and Sept 2005 Linac ran at 46.6 GeV, rather than 50 GeV,  max. positron energy only 8 MeV. Positron asymmetries observed of order 1%. Preliminary calculation of analyzing power implies that positron polarizations of up to 80-90% were observed.

  8. Implications The use of undulator-based production of positrons was accepted as the ILC baseline at SNOWMASS’05. The use of a helical undulator for production of polarized positrons is the recommended option. This option must now be established as cost effective.

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