bi.bsw chicane magnets

BI.BSW Chicane MagnetsD. Aguglia, J. Borburgh,

B. Balhan, C. Baud, C. Bracco, C. Carli, M. Cieslak, M. Hourican, D. Nisbet, W. Weterings

0 336 1032 1296 1560 2256 2654

0

20

40

60

80

100

120

140

160

Drift Space [mm]

Am

plit

ud

e [m

m]

PSB Injection Geometry for 380mm magnets, 316mm magnetic length, 66mrad, 340mT, 126mTm

35

149

InjectedH- Beam

CirculatingH+ Beam

BSW1 BSW2 BSW3 BSW4

StrippingFoil

H0

Dump

H-

Chicane layout

9/11/2011 J. Borburgh BSW magnets 2Review on PSB 160 MeV H- injection

Beta beating mitigation

• S-bend– Only effective for a fixed angle, not throughout the ramp– More difficult to implement mechanically, in particular on

short magnets

• Combined function magnets – Only effective for a fixed angle, not throughout the ramp

• R-bend and active compensation – Chosen as baseline solution


Powering• Ramp down time ~ 5 ms.• Controlled ramp down to allow active compensation.• All four magnets per ring powered in series.• Each power converter will occupy either 2 or 3 19’’ standard

racks.• 4 power converters + 1 spare = 10 to 15 racks.• Controllable switch mode power converter + current step-up

transformer in the tunnel• Transformers to be placed near magnets, assuming 10μH

margin (for cables + uncertainty on magnet inductance + transformer leakage inductance) → transformers must be placed not farther than ~5m from magnets!


0.045 0.05 0.055 0.06 0.065-1000

-500

0

500

1000

Time [s]

Prim

ary

vo

ltag

e [V

]

0.045 0.05 0.055 0.06 0.065-500

0

500

1000

1500

Time [s]

Prim

ary

Cu

rre

nt [

A]

Topology : AC/DC conversion to 1kVDC & DC/DC conversion via two interleaved IGBTs H-Bridges.Interleaved topology allows using standard IGBTs (current share) and reduces current ripple.Magnetic energy regenerated into the capacitor banks (minimized losses & power consumption)

Ma

gn

ets400VAC

Racks in Building 361 (ground flor)

Tunnel

Simulated primary voltage and current

Power converter output:1kV - 1.5kA 1.5MW peak power

Power converters

Bump closure flexibility

• Following recommendation of “PS Booster with Linac4” review (January 2009), magnets are assumed to be powered in series per ring.

→All magnets will have to provide same ∫B.dl/I.→Magnets should be aligned precisely at their

position longitudinally.

Would trim power supplies be desirable?


Space constraints


Magnets must be removable from ring without breaking vacuum. Permissible septum thickness limited.Longitudinal space limited to 380 mm, to allow sufficient space for stripping foil mechanism.Magnetic length maximised (↘β beating).

Baseline magnet parameters

Magnet Aperture

H x V[mm x mm]

Magnetic Length

[mm]

Physical Length

[mm]

∫Bydl[Tm]

Deflection[mrad]

BSW1 162 x 85 316 373 0.126 66.0

BSW2 218 x 85 316 380 0.126 66.0

BSW3 218 x 85 316 380 0.126 66.0

BSW4 242 x 85 316 380 0.126 66.0

Assumes ceramic vacuum chamber with a vertical beam acceptance ~ 65 mm.


Parameters per magnet typeMagnetic Properties BSW1 BSW2/

BSW3BSW4

Field in the center of the magnet [T] 0.399 0.399 0.399

∫Bydl at magnet centre [m.Tm] 126 126 126

Electric current [kA] 13.5 13.5 13.5

Field homogeneity [%] 1 1 1

Good field region (h x v) [mm] 85x140 85x196 85x220

R (mΩ) 0.3 0.3 0.32

L (μH) 3.3 4.2 4.7

Number of turns 2 2 2

Mechanical properties

Physical length [mm] 373 380 380

Septum conductor thickness [mm] 7 n.a. n.a.

Pole face length [mm] 297.8 301 296

Endplate thickness [mm] 13.6 15.5 12

Yoke cross section [mm] 260x260 390x220 390x220

Aperture [mm] 162x85 218x85 242x85

Water cooling [ l/min.] 4 3.4 3.3

Water cooling pressure [bar] 12 12 12


How to describe field imperfections• What to calculate?• How to take into account field

perturbations by dump and beam instrumentation?

• Vacuum chamber coating neglected so far.

• All calculations refer to By. 4500 6500 8500 10500 12500 14500315.99

316

316.01

316.02

316.03

316.04

316.05

316.06

316.07

316.08

316.09

316.1

0.009326

0.009327

0.009328

0.009329

0.00933

0.009331

0.009332

0.009333

0.009334

0.009335

Leq [mm]∫Bdl/I

I [A]

Lm [m

m]

6 26 46 66 86 106 126 146 1660

5

10

15

20

25

30

35

40

45

By homogenity [mT.m]

-100 -80 -60 -40 -20 0 20 40 60 80121.5

122122.5

123123.5

124124.5

125125.5

126126.5

f(x) = − 0.000000127286 x⁴ − 0.00000127088 x³ + 0.000183605 x² + 0.00269541 x + 125.94756

BSW1 ∫Bydl [mT.m]

ByPolynomial (By)

9/11/2011 J. Borburgh BSW magnets 10Review on PSB 160 MeV H- injection Blue area within 1% of ∫Bnom.dl

How to take into account field imperfections

Static field imperfection can be described as dipole with higher orders, but these are position dependant during the ramp.Influence of eddy currents could be neglected if sufficiently low (dump, vacuum chamber coating).Field maps could be used, but would have to be calculated for each turn. Imposing a maximum limit on the field imperfections (in space and time)? May lead to unrealistic values for such short magnets (magnetic length is less than 4 gap heights).


BSW1 leak field

• Requirement not formalised.• Targeted leak field: 10-3∫Bnominal.dl.• External magnetic screen foreseen.

• Count on injection steerers to compensate remaining leak field.


• 2D and 3D simulations performed.

• Both solid as well as segmented dumps evaluated.

Influence of dump on field in BS4

Field distortion by dump eddy currents

Simulation Parameters

Value units

Dump material conductivity

1.0E+05 S/m

Eddy current in dump

0.37 A

Simulated magnet Field

0.422 T

Switch off time 5 ms


DUMP and its monitoring

H0

H-

e-

2e-

p+

p+

Dump block

Monitors

BI equipment not taken into account for simulations as yet.Dump specification defines a limit on the field disturbance due to presence of dump (1%).Dump material suggested in specification: Carbon with resistivity in 1-510-5 Ωm range.


Magnetic field on stripping foil

Jmod < 0.7 μA rose coloured


Bmod < 6 mT rose coloured areas.

• Forces induced on the foil not evaluated yet, but J and B rather low.

• How to track electrons escaping from the foil?

Mechanical integration (1/3)

2 turn coil, split-able magnets, outer dimensions, support developmentInterference with neighbouring equipment (BI, Stripping, Vacuum equipment).

Mechanical integration (2/3)2 turn coil, split-able magnets. 0.35 mm thick laminations, glued magnets blocks.Glued end plates, same material as yoke.

Is the use of glued laminated magnets a reliable over time?Fixation to be studied. Outer dimensions limited in height and length.Magnet support and bus bars to be developed and integrated.Transformers to be integrated in vicinity:

dimensions to be evaluated, but rough estimation 80cmx80cmx80cm!Interference with neighbouring equipment (BI, stripping foils,

vacuum equipment). Ease of maintenance required (RP ALARA)!


Mechanical integration (3/3)


• Mechanical concept design started• Coil and yoke design to be completed at CERN• Coil and yoke manufacture to be subcontracted to

industry• Mechanical support and installation jig to be designed and

built in house

What if we adopt Inconel vacuum chambers? (1/2)

+ Mechanically more robust+ Less costly+ Potentially less activation

Field deformation due to induced eddy currents:

- delay (depending on vacuum chamber width)- deformed field shape

Approximate field delays vary from 47μs (BSW1) to 90 μs (BSW4).


Current distribution in race track shaped vacuum chamber.

What if we adopt Inconel vacuum chambers? (2/2)

― Field quality deterioration.― Introduction of higher order field components, magnetic centre

not on the central orbit.± Sextupolar components manageable, but quadrupolar

component potentially dangerous (needs precise compensation to avoid resonance).

± Field delay depends on width of vacuum chamber! ― 3 field delays implies three power supplies per ring -> space for

transformers (12!) ?± Try to design all magnets same gap and vacuum chamber width

(inductance ↗, BS1 may become too tall or even more non-linear)?


Summary of outstanding questions

• Would trim power supplies be recommended when powering all BSW per ring in series?

• What to calculate to simulate the impact of field imperfections?• How to add the field deformation provoked by dump and its measurement

systems?• Would imposing a limit on the absolute field imperfections (in space and

time) be realistic?• Is septum (BSW1) leak field critical?• Is it necessary and how to track the electrons escaping from the stripping

foil?• Are glued laminated yoke reliable over time in a radioactive environment?• What should be the preferred vacuum chamber material?• Have we overlooked anything else?9/11/2011 J. Borburgh BSW magnets 22Review on PSB 160 MeV H- injection

bi.bsw chicane magnets

Documents