ATF2 Magnets ATF2 Magnets 11Mar '08, Weekly MtgCherrill Spencer Status Report ATF2 FD quads 1 Status Report on the ATF2 “Final Doublet” quads being made at SLAC from old FFTB “QC3” style quads: 11 th March 2008 Cherrill Spencer, SLAC Member of ATF2 Magnet Team

ATF2 Magnets ATF2 Magnets 11Mar '08, Weekly MtgCherrill Spencer Status Report ATF2 FD quads 2 Concern about affect of nearby steel H beam on the QD0 field Shintake monitor’s support structure, closest approach to QD0

ATF2 Magnets ATF2 Magnets 11Mar '08, Weekly MtgCherrill Spencer Status Report ATF2 FD quads 3 Plan view of Shintake support & magnet support table showing about 40 cm from middle of H steel beam to closest edge of QD0 steel core Closest approach here QD0

ATF2 Magnets ATF2 Magnets 11Mar '08, Weekly MtgCherrill Spencer Status Report ATF2 FD quads 4 Use a ~60cm long steel H beam of approx correct dimensions and put it 40 cm from core edge, stand it up vertically for ease of installation & is worst case. Size & shape of H beam: A=B=15cm T 1 =0.7cm Steel H beam QD0 being measured

ATF2 Magnets ATF2 Magnets 11Mar '08, Weekly MtgCherrill Spencer Status Report ATF2 FD quads 5 Measure QD0’s integrated strength & multipoles at 132 amps, 5 times without H beam & 5 times with H beam Calculate averages of ∫G.dl/amp without and with H beam: Without: / T/A With: / T/A –Delta=0.0019% -> insignificant 12-pole without with as % of quad at 1cm > NO change in multipoles

ATF2 Magnets ATF2 Magnets 11Mar '08, Weekly MtgCherrill Spencer Status Report ATF2 FD quads 6 Chosen method for enlarging the FFTB “QC3” quad’s bore diameter Place a very flat and precise thickness shim in each split plane to “explode” the quad and enlarge the bore diameter. Shim will be low carbon steel, ground to ” flatness Hyperbolic pole-tip is moved, along a radius, further out than it’s equation says it should be. XY= r 2 /2. Consequence: the 12-pole component increases, ~17 times predicts POISSON. ATF2 has very tight tolerances on the multipoles in QD0 & QF1

ATF2 Magnets ATF2 Magnets 11Mar '08, Weekly MtgCherrill Spencer Status Report ATF2 FD quads 7 Drawings of the modified core with ground shims in place Sextupole component is very sensitive to poletip being at wrong radius or the poletip being offset “azimuthally” GOAL :Adjacent pole distances (red arrow above) adjusted to be same to +/ mm. Then cores pieces pinned –BUT DOWEL PIN HOLES TOO SMALL, so achieved +/-0.031mm

ATF2 Magnets ATF2 Magnets 11Mar '08, Weekly MtgCherrill Spencer Status Report ATF2 FD quads 8 Close up view of modified quad Shim added at split plane Large bolts keep 4 core quadrants attached to each other

ATF2 Magnets ATF2 Magnets 11Mar '08, Weekly MtgCherrill Spencer Status Report ATF2 FD quads 9 POLE SIDE SHIMS IN PLACE- reduce the 12-pole to below tolerance

ATF2 Magnets ATF2 Magnets 11Mar '08, Weekly MtgCherrill Spencer Status Report ATF2 FD quads 10 Sextupole/quad values did not change when installed pole side-shims 12 pole/quad at 1cm reduced from 0.17% to 0.034% [tolerance was <0.05%] Sextupole/quad still at 0.038% at 1cm Much too large said Glenn White. The spot size at the IP is very sensitive to the sextupole components in QD0 and QF1 –The unwanted sextupole is mostly a skew sextupole, it affects the spot size, we have to improve the adjacent pole distance symmetry. The pole side- shims having some asymmetry [ ~0.3 mm] did not increase the sextupole component.

ATF2 Magnets ATF2 Magnets 11Mar '08, Weekly MtgCherrill Spencer Status Report ATF2 FD quads 11 Worked with technician to improve adjacent pole symmetry Had to enlarge the dowel pin holes so could adjust the quadrant positions- first try did not improve the symmetry on quad #1, so worked on quad #2 – bolt torque settings adjusted iteratively, distances re- measured Have achieved much closer distances, largest difference is mm, or +/ mm, other differences are smaller. Measured field without pole-side shims: sextupole/quad at 1cm = 0.013% –i.e. one-third its previous value.

ATF2 Magnets ATF2 Magnets 11Mar '08, Weekly MtgCherrill Spencer Status Report ATF2 FD quads 12 Magnetic measurements also measure the angle of the first south pole of any multipole, relative to horizontal axis The angle measurements indicate there is significant skew sextupole mixed in with the normal sextupole. Glen White has modelled the beam passing through QF1 & QD0 with the smallest multipoles I have achieved, at their measured angles, and the spot size is still “too large”. But when the FD sextupoles strength and roll (using their magnet movers) are adjusted to compensate for the unwanted sextupoles in QF1 & QD0 then the spot size is below 40 nm.

ATF2 Magnets ATF2 Magnets 11Mar '08, Weekly MtgCherrill Spencer Status Report ATF2 FD quads 13 How to maintain the best positions of the 4 quadrants, e.g. after quad been split for SBPM to be installed? Problem: when the pole side-shims are installed you cannot access the ends of the hyperbolic poletip to measure the adjacent pole distances anymore. The shim to shim distances don’t tell you how good the poletip distances are. But need these poletip distances to be correct to better than 0.010mm We will shorten the pole-side shims by about 1cm at each end so gauge blocks can still be used to adjust the adjacent pole distances. 12-pole will increase a little- but we are sufficiently below the 12-pole tolerance we can afford to let it increase.

ATF2 Magnets ATF2 Magnets 11Mar '08, Weekly MtgCherrill Spencer Status Report ATF2 FD quads 14 Thermal behaviour & integrated strength Thermal tests : run at 150 amps for ~ 1 hour with 2.5 gpm total in 8 water circuits –Cooling water temperature increased by ~1.3°C [will be less at operating current] Will run at amps to get required nominal ∫G.dl. In order to shift the IP spot onto the Honda monitor, QD0 needs to run much stronger- will need 220 amps. Did a thermal test at 220 amps also. LCW temp increased by ~1.8°C- acceptable increase.

ATF2 Magnets ATF2 Magnets 11Mar '08, Weekly MtgCherrill Spencer Status Report ATF2 FD quads 15 ATF2 FD quad run at 150 amps for 45 minutes

ATF2 Magnets ATF2 Magnets 11Mar '08, Weekly MtgCherrill Spencer Status Report ATF2 FD quads 16 ATF2 FD quad run at 220 amps for 2 hours