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Different Tagging Philosophy Beam Test Meeting Pisa May 16, 2006 Gary Godfrey

Different Tagging Philosophy Beam Test Meeting Pisa May 16, 2006 Gary Godfrey godfrey@slac.stanford.edu. Philosophy. Calibrate CsI energy with electrons Ebeam=1, 3, 5, 15 GeV Calibrate CsI energy with tagged photons .1 – 1 GeV (Ebeam=1 GeV)

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Different Tagging Philosophy Beam Test Meeting Pisa May 16, 2006 Gary Godfrey

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  1. Different Tagging Philosophy Beam Test Meeting Pisa May 16, 2006 Gary Godfrey godfrey@slac.stanford.edu

  2. Philosophy • Calibrate CsI energy with electrons Ebeam=1, 3, 5, 15 GeV • Calibrate CsI energy with tagged photons .1 – 1 GeV (Ebeam=1 GeV) • Bmagnet=max (.5 T-m) Tagger Position set so unradiated beam is on the inner edge of Si. • NEVER change tagger position. NEVER change magnet strength. • Ebeam=3 GeV (max energy that can be deflected enough onto dump). Also pions start to flash Cherenkov at 5 GeV. • All PSF photons taken with BeamScint*Cherenkov trigger. First two tagger Si readout on every trigger. All tagger Si only read out when tagger scintillator sees an electron. Tagger only tags 1.5-1.9 Gev photons. All photons .1 – 3 GeV are binned by CsI (which is already calibrated). Nice flat spectrum of photons in [photons/fractional size energy bin].

  3. Philosophy • Advantages: • Tagger is calibrated with minimum wasted time. • Get all photons from 0 to 3 GeV without repeating angle/positions multiple times with the tagger (or magnet field) in different positions. • Our desire for statistics, angles, xy positions can fit in the available run time.

  4. Run Time for Estimate for PS (Gary’s suggested runs)

  5. Beam Deflection at the Dump [meters]

  6. Comments • We do not have enough beam time to tag every energy photon (20 Mev to 2.5 Gev) at evergy angle and position that we wish to run. • Therefore, use the full Brems spectrum (Ebeam=2.5 GeV) on every run by using the calibrated CsI calorimeter to put the photons into energy bins. • Use beam electrons to calibrated the CsI for E> 1 GeV • Use tagged photons (1 GeV beam) to calibrate the CsI for E< 1 GeV • Let the tagger read out when ever it sees a electron during the 2.5 GeV running (will tag 1.5 to 1.9 GeV photons). Tagger writes at least 2 SiXY (.6 msec) when there is a CU trigger but no electron in the tagger. • Si tagger sits as close as possible to the bend magnet, but not so close that the magnet fringe field bends the tracks from a straight line in the downstream Si telescope. This close position maximizes the momentum bite of the tagger. • Never move the Si tagger. Never change B. It is possible to place the Si at a reasonable (~11 cm) distance from the beam axis such that an unradiated 1 GeV beam hits the Si inner edge (for B=10 Kgauss). The tagger is now calibrated and will measure E <= 1 GeV radiated beam when Ebeam=2.5 GeV.

  7. Pollution by Double Brems in the Radiator

  8. Pollution by Double Brems versus Radiator Thickness • The radiator thickness is the sum of: • 1) Cherenkov windows and gas • 2) Scintillator • 3) Upstream Tagger telescope (2 windows + 4 Si detectors) Desired

  9. Tagger Photon Resolution for 1 GeV Beam

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