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Methodology

Methodology. Tracking to downstream end of CC-1 with ASTRA Using PI parameters (possibly) suited for 3.2nC/bunch and bunch compression Egun @ 40MV/m, -12 °; CC-1 @ 60MV/m -15° (wrt max. acceleration) Dark current originating uniformly on 16mm dia. Mo cathode plug

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Methodology

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  1. Methodology • Tracking to downstream end of CC-1 with ASTRA • Using PI parameters (possibly) suited for 3.2nC/bunch and bunch compression • Egun @ 40MV/m, -12°; CC-1 @ 60MV/m -15° (wrt max. acceleration) • Dark current originating uniformly on 16mm dia. Mo cathode plug • Using gaussian approximation to “Han” time distribution (see next slide) • I(t) = A*sin2.5(wt)*exp(-B/sin(wt)); B=5 • ~ A*exp(-.5*t2/s2) • Using apertures from R. Andrew’s drawings • Using ABCI to calculate collimator wakefield

  2. Dark Current Time Distribution @ Cathode RF phase (deg)

  3. Dark Current Intensity vs. Distance from Cathode (table)

  4. Dark Current Intensity vs. Distance from Cathode (graph)

  5. Transverse Wakefield from Collimator (from ABCI) gaussian bunch, sz = 1.8mm 1.0 cm dia: peak wake = 750 V/pC/m 1.2 cm dia: peak wake = 520 V/pC/m 1.4 cm dia: peak wake = 370 V/pC/m 1.6 cm dia: peak wake = 270 V/pC/m 1.8 cm dia: peak wake = 200 V/pc/m 2.0 cm dia: peak wake = 160 V/pC/m

  6. Beam Alignment Criteria at the Collimator Limit transverse jitter of downstream beam to < .1sy Dqcoll<20mrad. Using average wake field ~ ½ peak wake field; 3.2 nC; Pbeam=4.7 MeV/c 2 cm dia. collimator: Dyjitter < 380 mm 1 cm dia. collimator: Dyjitter < 80 mm Limit emittance blowup downstream beam to < 10%. De/e = 2*Ds/s < Dx/s  Dqcoll less stringent than previous criterion

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