[PPT] - Eddy Current Septum Magnet Optimization Powering Options of SMH42 PowerPoint Presentation

SLIDE 1

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)

SLIDE 2

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

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SLIDE 3

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

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SLIDE 4

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: By and ∫Bydl.

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7ms half sine 3mm septum

SLIDE 5

Baseline Design Performance

ʃBy,gapdlmax = 502.67Tmm
By,gap,max = 542mT
ʃBy,fringedlmax = -1.37Tmm (after the current pulse)
By,fringe,max = -1.4mT (after the current pulse)
Idriving,max = 30251A
Gap fringe

field shape:

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SLIDE 6

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

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SLIDE 7

Analysis in Time Domain (2/2)

6 values for each simulated moment:

– t [ms] – I [kA] – By (gap) – ∫Bydl (gap) – By (fringe) – ∫Bydl (fringe)

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“gap”: the middle of the aperture “fringe”: 5mm from the septum

SLIDE 8

Comparing By of Full Sine and Half Sine

Fringe field extents

after excitation.

Full sine:

By = -1.4mT

Half sine:

By = 15mT

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1 2 3 4 5 6

40
30
20
10

10 20 30 40 Current [kA] Time [ms] 1 2 3 4 5 6

2

2 4 6 8 10 12 14 x 10

3

Magnetic flux density [T] 1 2 3 4 5 6 20 40 Current [kA] Time [ms] 1 2 3 4 5 6 0.01 0.02 Magnetic flux density [T]

SLIDE 9

Comparing ʃBydl of Full Sine and Half Sine

Integrated fringe

field extents after excitation.

Full sine:

∫Bydl = -1.37Tmm

Half sine:

∫Bydl = 14.28Tmm

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1 2 3 4 5 6

50

50 Current [kA] Time [ms] 1 2 3 4 5 6

20

20 Field integral [Tmm] 1 2 3 4 5 6 20 40 Current [kA] Time [ms] 1 2 3 4 5 6 10 20 Field integral [Tmm]

SLIDE 10

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 10.4-10.7 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.

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SLIDE 11

Comparing By of 5mm and 3mm Septa

Fringe field extents

after excitation.

5mm septum blade:

By = -1.4mT

3mm septum blade:

By = -3.6mT

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1 2 3 4 5 6

40
30
20
10

10 20 30 40 Current [kA] Time [ms] 1 2 3 4 5 6

2

2 4 6 8 10 12 14 x 10

3

Magnetic flux density [T] 1 2 3 4 5 6

40
20

20 40 Current [kA] Time [ms] 1 2 3 4 5 6

0.01

0.01 0.02 0.03 Magnetic flux density [T]

SLIDE 12

Comparing ʃBydl of 5mm and 3mm Septa

Integrated fringe

field extents after excitation.

5mm septum blade :

∫Bydl = -1.37Tmm

3mm septum blade :

∫Bydl = -3.51Tmm

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1 2 3 4 5 6

50

50 Current [kA] Time [ms] 1 2 3 4 5 6

20

20 Field integral [Tmm] 1 2 3 4 5 6

40
20

20 40 Current [kA] Time [ms] 1 2 3 4 5 6

10

10 20 30 Field integral [Tmm]

SLIDE 13

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 1.7-2.6 times lower

using 5mm septum instead of 3mm.

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SLIDE 14

Comparing By of 2ms and 7ms Wavelength

Fringe field extents

after excitation.

2ms wavelength:

By = -1.4mT

7ms wavelength:

By = -15.6mT

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1 2 3 4 5 6

40
30
20
10

10 20 30 40 Current [kA] Time [ms] 1 2 3 4 5 6

2

2 4 6 8 10 12 14 x 10

3

Magnetic flux density [T] 5 10 15 20 25

40
20

20 40 Current [kA] Time [ms] 5 10 15 20 25

0.02

0.02 0.04 0.06 Magnetic flux density [T]

SLIDE 15

Comparing ʃBydl of 2ms and 7ms Wavelength

Integrated fringe

field extents after excitation.

2ms wavelength :

∫Bydl = -1.37Tmm

7ms wavelength :

∫Bydl = -15.14Tmm

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1 2 3 4 5 6

50

50 Current [kA] Time [ms] 1 2 3 4 5 6

20

20 Field integral [Tmm] 5 10 15 20 25

40
20

20 40 Current [kA] Time [ms] 5 10 15 20 25

20

20 40 60 Field integral [Tmm]

SLIDE 16

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 3.2-11.1 times

lower using 2ms full sine wave instead of 7ms.

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SLIDE 17

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.

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SLIDE 18

References

Full documentation: Z. Szoke: Eddy Current Septa Magnet

Optimization

M. J. Barnes, J. Borburgh, B. Goddard, M. Hourican, in Proceedings
f the CAS-CERN Accelerator School: Magnets, Bruges, Belgium, 16-

25 June 2009, edited by D. Brandt, CERN-2010-004, pp. 167-184

Finite element simulations: Cobham Opera 16
Data processing: MATLAB R2013b

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SLIDE 19

Thank You for Your Attention! Q&A

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