CONFIGURATION UPDATES TO THE 10 DECEMBER 1997 BASELINE DESIGN

  1. Optical Cavity Chicane Layout - Updated 11 February 1997 to accomodate additional radiation shielding for optical components. Bend angles slightly reduced (bend radii changed; physical length of dipole is fixed by hardware design!) and spacings slightly increased (outboard bends moved out, inboard bends moved in ) to increase available space. Longitudinal center of chicane held fixed, transverse offset increased slightly; path length held exactly fixed and momentum compaction kept approximately the same. Matching telescopes reset to compensate changes in dipole focussing. Reference DIMAD files ~douglas/prinzipal/optics/IRFEL_optics/irapr96/baseline/problems/simulation/1216simulations/simchicane and simchicaneout.
  2. Patch For Wiggler Focussing - Updated 7 May 1997 to correct oversite in model of wiggler (earlier files had beam rigidity in wiggler evaluated at 40 MeV/c rather than 42.00310846 MeV/c. Resulted in small change in wiggler focussing (compensated by refitting matching telescope excitations), very small change in momentum compaction, very very small change in path length. No changes in hardware layouts or parameters, very small changes in matching/trim quad excitations, sextupole excitations. Reference DIMAD files ~douglas/prinzipal/optics/IRFEL_optics/irapr96/baseline/problems/simulation/1216simulations/sim0318/sim0507 and sim0507out.
  3. Reinjection Telescope Layout - Updated 23 May 1997 to provide additional space for diagnostics. Doublet internal spacing increased by 0.15 m and doublet-to-doublet spacing increased by 0.15 m. First quad position held fixed; next two moved 0.15 m downstream, last quad moved 0.3 m downstream. All quads refit to give same reinjection condition. Reference DIMAD files ~douglas/prinzipal/optics/IRFEL_optics/irapr96/baseline/problems/simulation/1216simulations/sim0318/sim0523 and sim0523out.
  4. Corrector Field Range - Updated 3 June 1997 on the advice of the commissioning meeting to reduce the correctors from +/- 6 sigma of rms anticipated error (as estimated in CEBAF-TN-96-035) to +/- 4 sigma of rms anticipated error. This reduces the corrector dynamic range from +/- 10 mrad/+/- 1500 g-cm at 42 MeV to +/- 6.7 mrad/+/- 1000 g-cm at 42 MeV.
  5. DX Transverse Field Flatness/Good Field Spec - Updated 4 November 1997 to reflect observed failure of delivered DX dipoles to meet a stringent field flatness/good field spec originally imposed for the DQ dipoles and simply copied for the DX dipoles. The original spec, required for DQ dipoles at a 2 m dispersion, was 202 mm [6*(sigma betatron + eta sigma dp/p)+ 40 mm working aperture + 35 mm sagitta]. Sigma betatron ~ 1.25 mm, eta sigma dp/p ~ 20 mm, giving the 202 mm number. The DX dipoles are used at a point where eta<=0.125 m, meaning eta sigma dp/p ~ 1.25 mm; consequently, the required good field is ~90 mm, with 20 mm additional allowance for transversely moving the magnet to adjust its effective length. New spec: 10^-4 field linearity over 110 mm width. This is met.
  6. DV Transverse Field Flatness/Good Field Spec - Updated 24 November 1997 to reflect observed failure of delivered DV dipoles to meet a stringent field flatness/good field spec originally imposed for the DU dipoles and simply copied for the DV dipoles. The original spec, required for DU dipoles transporting injected/recirculated or energy-recovered/recirculated beams, was 95 mm [6*(sigma betatron + eta sigma dp/p)+ 40 mm working aperture + 28 mm sagitta]. Sigma betatron ~ 2.55 mm, eta sigma dp/p ~ 2 mm, giving the 95 mm number. The DV dipoles are used on a single 42 MeV beam at a point where eta<=0.05 m (with potentially large momentum spread, at reinjection), beta ~13 m, and the energy is higher, meaning eta sigma dp/p ~ 0.5 mm and the sigma betatron is ~ 1.4 mm; consequently, the required good field is 62 mm. New spec: 10^-4 field linearity over 62 mm width. This is met, more or less, even with magnetic shielding for the injection/energy recovery line in place.
  7. DV Effective Length Spec - Updated 1 December 1997 The effective length of the DV dipoles must track that of the DUs. The latter was set without backing out the contribution of the earth's field, resulting, for a fixed core field (that closely matches the design value), in a magnet that is order 0.5% too long, with a resultantly large bend angle. This does not significantly alter the focussing properties; it does, however, potentially steer the beam. Therefore, the DV effective length is modified to track and compensate this effect in the DU. The incremental length is of order 3 mm; this will be added by shimming each end of the DV with 1/16" shims.
Last modified: 9 July 1997
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