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Measurements of SMA108-1 (a similar magnet, SMA107-1, is now being tested)

Measurements of SMA108-1 (a similar magnet, SMA107-1, is now being tested). Development & Test Dept. H. Glass 4/30/1999 (updated 6/22/01). SMA108-1 multipole corrector. Two coils: -sextupole, 600 A max +octupole, 60 A max (HP supply limited to 50A) aperture ~ 4.2” (vert) x 14” (horiz)

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Measurements of SMA108-1 (a similar magnet, SMA107-1, is now being tested)

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  1. Measurements of SMA108-1(a similar magnet, SMA107-1, is now being tested) Development & Test Dept. H. Glass 4/30/1999 (updated 6/22/01)

  2. SMA108-1 multipole corrector • Two coils: • -sextupole, 600 A max • +octupole, 60 A max (HP supply limited to 50A) • aperture ~ 4.2” (vert) x 14” (horiz) • Measurement goal: strength & harmonics in region x < 4.0” vs 6p, 8p currents

  3. Measurement Setup on Stand B • View from non-lead end +x

  4. Measurement plan • New checklist SMA_2P_harmonics_at_fixed_8P • 3 octupole hysteresis loops 050 0 • set fixed octupole current i8p • 3 sextupole hysteresis loops 0 600 0 • loop over sextupole currents • i6p = {0,200,300,400,500,600} • measure reference using 2p • measure harmonics using {4p,6p,8p,12p,20p,2p} • Each sequence has unique (x, i8p) • i8p = {0, 20, 40, 50} • x = {0, ±1, ±2, ±3, ±4} inches

  5. Measurement plan (2) • Additional checklist SMA_6P_harmonics_at_fixed_8P • uses 6p winding as reference • done at a few places to verify 2P checklist data • Report harmonics in fixed coordinate system • probe reference mark must remain fixed and aligned to encoder index throughout data collection

  6. Fixed coordinate system Standard MTF reporting is relative to direction of reference harmonic not desirable in this case: reference dir changes with x, current Choose coordinate system so that normal harmonics point toward vertical (+y) at all (x, i6p, i8p) determine actual field direction at, e.g., (x=0, i8p=0, i6p=600) using magnaprobe; this is n(i0) find measured field direction (depends on details of probe layout, starting rotation angle, encoder index); this is n(i0) correct measured phases everywhere using these parameters:

  7. Sequence summary • 2P runs analyzed using 1(i0) = 114.781(i0) = 0. • Note dipole field reversal for x3”, x-2” • 6P runs analyzed using 3(i0) = 117.963(i0) = 180.m = 1 • Stability of 3is good indicator probe ref marked stayed fixed

  8. Comparison of 2P & 6P data • Absolute fields from both data sets agree reasonably well (some skews don’t agree so well) • use best fit to correct 1(i0) - 3(i0); find D = 14 mrad

  9. Magnetic center calculation using harmonics at x=0, i8p=0 Calculated xctr, yctr are consistent with uncertainty in probe placement

  10. 6P & 8P strengths Measurements at x = 0 B4 excitation pieced together from several sequences (6P hysteresis loops between each data point) DB3 with i8P @50 < 0.25% (stronger) DB4 with i6P @600  2% (weaker)

  11. Trivial way to plot field shape: plot dipole vs x and connect the dots • dipole and sextupole have opposite signs (expected since magnet doesn’t have 6-fold symmetry

  12. Reconstructed field (up to 14-pole) fits together smoothly

  13. Change of field shape with 8P current as expected (+octupole ~x3 )

  14. Normal harmonics at 1.0” relative to B3 Interesting things: b2 shows mag ctr shift with i8p; b1 grows faster than b3; b5 = -17 units @600A

  15. Skew harmonics at 1” relative to B3

  16. For more information... • Complete data set found in http://tdpc02.fnal.gov/glass/SMA108-1_summary.xls • contains all harmonics in hr_good_harms file format • plots from this presentation • tables of B1, B3, B4 as functions of (x, i6p, i8p) • tables of normal and skew harmonics normalized to 6P

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