Eddy Current Septum Magnet Optimization Powering Options of SMH42 and the Influence of the Septum Thickness on the Fringe Field Zsolt SZOKE (TE/ABT/SE)

Outline Eddy Current Septa Magnets Our Goal Baseline Design Performance Analysis in Time Domain Comparing Full Sine and Half Sine Excitation Comparing 5mm and 3mm Septum Blades Comparing 2ms and 7ms Wavelength 19/08/2014LIU-PS Meeting2

Eddy Current Septa Magnets Different types of septa: – direct drive (DC, pulsed) – eddy current (only pulsed) Eddy current type - advantages: – coil dimensions are not critical – the pulsed coil has such a magnetic field which induces eddy currents in the septum counteracting the fringe field – septum can be very thin 19/08/2014LIU-PS Meeting3

Our Goal Optimize different eddy current septum magnet parameters. 3 comparisons made with the baseline design. Baseline: 2ms, full sine, 5mm septum. Examination of the fringe field: B y and ∫B y dl. 19/08/2014LIU-PS Meeting4 7ms half sine 3mm septum

Baseline Design Performance ʃ B y,gap dl max = Tmm B y,gap,max = 542mT ʃ B y,fringe dl max = -1.37Tmm (after the current pulse) B y,fringe,max = -1.4mT (after the current pulse) I driving,max = 30251A Gap fringe field shape: 19/08/2014LIU-PS Meeting5

Analysis in Time Domain (1/2) Opera finite element simulation, spanning 3× the excitation time Discrete moments  interpolation in MATLAB 2 types of interpolation: – PCHIP: for plotting – SPLINE: for peak determination 19/08/2014LIU-PS Meeting6

Analysis in Time Domain (2/2) 6 values for each simulated moment: – t [ms] – I [kA] – B y (gap) – ∫B y dl (gap) – B y (fringe) – ∫B y dl (fringe) 19/08/2014LIU-PS Meeting7 “gap”: the middle of the aperture “fringe”: 5mm from the septum

Comparing B y of Full Sine and Half Sine Fringe field extents after excitation. Full sine: B y = -1.4mT Half sine: B y = 15mT 19/08/2014LIU-PS Meeting8

Comparing ʃ B y dl of Full Sine and Half Sine Integrated fringe field extents after excitation. Full sine: ∫B y dl = -1.37Tmm Half sine: ∫B y dl = 14.28Tmm 19/08/2014LIU-PS Meeting9

Comparing Full Sine and Half Sine Huge time constants in both cases: – 1 or 2ms excitation time (half or full sine) – time constant: >4ms Fringe field peak values are times lower using full sine wave instead of half sine. Using ‘direct damping’ of the fringe field (full sine excitation) proves to be very effective. 19/08/2014LIU-PS Meeting10

Comparing B y of 5mm and 3mm Septa Fringe field extents after excitation. 5mm septum blade: B y = -1.4mT 3mm septum blade: B y = -3.6mT 19/08/2014LIU-PS Meeting11

Comparing ʃ B y dl of 5mm and 3mm Septa Integrated fringe field extents after excitation. 5mm septum blade : ∫B y dl = -1.37Tmm 3mm septum blade : ∫B y dl = -3.51Tmm 19/08/2014LIU-PS Meeting12

Comparing 5mm and 3mm Septa A thinner septum blade is advantageous for the beam: lower continuous losses. 3 mm septum blade has higher current density. Fringe field peak values are times lower using 5mm septum instead of 3mm. 19/08/2014LIU-PS Meeting13

Comparing B y of 2ms and 7ms Wavelength Fringe field extents after excitation. 2ms wavelength: B y = -1.4mT 7ms wavelength: B y = -15.6mT 19/08/2014LIU-PS Meeting14

Comparing ʃ B y dl of 2ms and 7ms Wavelength Integrated fringe field extents after excitation. 2ms wavelength : ∫B y dl = -1.37Tmm 7ms wavelength : ∫B y dl = Tmm 19/08/2014LIU-PS Meeting15

Comparing 2ms Wavelength and 7ms 3.5 ms pulse half sine shape would be a pulse length similar to present SMH42. Shorter pulse length (w.r.t. baseline design) wasn’t investigated, since it will be very difficult to build a compatible magnet. Fringe field peak values are times lower using 2ms full sine wave instead of 7ms. 19/08/2014LIU-PS Meeting16

Final Conclusion Full sine vs. Half sine Direct fringe field cancellation very effective 5mm septum vs. 3mm septum The thicker the septum, the lower the fringe field 2ms wavelength vs. 7ms wavelength The shorter the pulse, the lower the fringe field The base line design appears a good compromise. Next: the BMP42 septum bumper analysis. 19/08/2014LIU-PS Meeting17

References Full documentation: Z. Szoke: Eddy Current Septa Magnet Optimization M. J. Barnes, J. Borburgh, B. Goddard, M. Hourican, in Proceedings of the CAS-CERN Accelerator School: Magnets, Bruges, Belgium, June 2009, edited by D. Brandt, CERN , pp Finite element simulations: Cobham Opera 16 Data processing: MATLAB R2013b 19/08/2014LIU-PS Meeting18

Thank You for Your Attention! Q&A 19/08/2014LIU-PS Meeting19