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EMMA Magnet Design
Ben ShepherdMagnetics and Radiation Sources Group
ASTeCSTFC Daresbury Laboratory
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
Overview
Introduction – the EMMA lattice EMMA magnets – ‘interesting’ aspects 3D modelling Current status Next steps
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
ERLP and EMMA
EMMA will be an FFAG addon to the Energy Recovery Linac Prototype (ERLP) project at Daresbury
EMMA: 10MeV 20MeV
ERLP is in the early stages of commissioning – the photoinjector gun is being commissioned and the booster linac is about to be installed
Ready by the end of 2007…?
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
The EMMA Ring
21 cells, each has:
2x D magnet2x F magnet
84 magnets in main ring
+ injection
+ extraction
6m
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
EMMA Cell Layout
FD D
Cavity
15 MeV Reference orbit centreline
ClockwiseBeam
Inside of ring
Outside of ring
Magnet Reference OffsetsD = 34.048 mmF = 7.514 mm
Geometry consisting of 42 identical(ish) straight line segments of length 394.481 mm
Long drift 210.000 mm
F Quad 58.782 mm
Short drift 50.000 mm
D Quad 75.699 mm
Magnet Yoke LengthsD = 65 mmF = 55 mm
Circumference = 16.568m
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
Magnet Challenges
‘Combined function’ magnets Dipole and quadrupole fields
Independent field and gradient adjustment Movable off-centre quads used
Very thin magnets Yoke length of same order as inscribed radius ‘End effects’ dominate the field distribution Full 3D modelling required from the outset
Large aperture + offset Good field region (0.1%) must be very wide
Close to other components Field leakage into long straight should be minimised
Close to each other Extremely small gap between magnets F & D fields interact
Full 3D modelling and prototyping essential!
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
F magnet
D magnet
http://www.cst.com/
Modelling carried out using CST EM Studio
Combined modelwith ‘realistic’ steel –B-H curve provided by Tesla
also produce Microwave Studio
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
F Magnet
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
D Magnet
Smaller horizontal aperture – but further out – so more challenging!
Smaller horizontal aperture – but further out – so more challenging!
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
Reduction of gradient with yoke length (F)
2D model gradient only reached by extending the magnet longitudinally by a factor of 3.
However, end effects are dominant, and the integrated gradient is larger than in the hard-edge model.
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
Field Clamps
Tracking studies suggest that field clamps are needed
Reduce the amount of field leaking into the long straight
Symmetric or asymmetric? Occupy space and increase
power demand
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.1
-250 -200 -150 -100 -50 0 50 100 150 200 250
none
symmetric
asymmetric
clamp plate position
Field Clamps
0.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0.040
0.045
-250 -200 -150 -100 -50 0 50 100 150 200 250
z / mm
fiel
d /
T
no clamp plate
symmetric clamp plate
asymmetric clamp plate
clamp plate position
`
F magnet
D magnet
Field at clamp reduced by ~80%in each case
Difference between asymmetric and symmetric windows is negligible
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
-300 -200 - 100 0 100 200z / mm
-0.004
-0.002
0
0.002
gx'
/T/
mm
Adjusted gradient on central trajectory
-200 -150 -100 - 50 0 50 100z / mm
-50
-40
-30
-20
-10
0
x/
mm
Trajectories through both magnets; gradient evaluated at =3.88°
— QBD— QBF— added— combined
-300 -200 - 100 0 100 200z / mm
-0.004
-0.002
0
0.002g
x'/
T/m
m
Adjusted gradient on central trajectory
max difference ~0.25T/m (5%)
Plot of absolute x gradient
Differences between separate and combined models
F
D
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
Shape Optimisation
Two variables tangent point chamfer size
Optimise in terms of normalised integrated gradient quality
integrate vertical field along z
differentiate w.r.t x
normalise to value at centre of vac chamber
0.1% region
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
Tangent point variation
QBD – tangent point 10mm tangent point 48mm
hyperbolic region
tangent region
poleprofile
inscribed radius
QBF Pole Shape
10
12
14
16
18
20
22
24
30 35 40 45 50 55 60
X / mm
Y /
mm
hyperbola
16
20
11
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
No chamfer 10mm chamfer
size of chamfer
Variation of chamfer on pole ends
Angle can be adjusted too – 45° used up to now
OPERA-3D results suggest that a chamfer of up to 5mm has negligible effect on field quality
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
Magnet Apertures
F magnet D magnet
Beam stay clear apertures highlighted
F: -28.2…13.8mm (42 mm)D: -41.6…-17.3mm (24.3 mm)
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
2D Modelling of F Magnet
Using OPERA 2D (Neil Marks):
0.02% over required good gradient region
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
3D Modelling
In OPERA 3D (Takeichiro Yokoi)
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
Tangent point variation
11mm
pole shape
gradient quality
+5%
-5%
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
Tangent point variation
14mm
pole shape
gradient quality
+5%
-5%
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
Tangent point variation
15mm
pole shape
gradient quality
+5%
-5%
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
Tangent point variation
16mm
pole shape
gradient quality
+5%
-5%
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
Tangent point variation
20mm
pole shape
gradient quality
+5%
-5%
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
Tangent point variation
28mm
pole shape
gradient quality
+5%
-5%
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
Optimal result (OPERA-3D)
Tangent point at 11mm Good field region: ±26mm
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
3D Field Effects
Transverse gradient strength changes as the integration region is expanded
‘End effects’ are dominant over full range
z
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
Pole Shape - Alternatives
Optimisation done so far in terms of ‘hyperbolic section’ and ‘tangent section’
‘End effects’ mean that the field profile is different to a long magnet
Maybe try a slightly different pole shape? Difficult to set parameters for a ‘free’ curve Quadratic section? Polynomial approximation of hyperbola? Try to guess optimal shape from ‘constant integrated
gradient’ contours
What tweaks to the pole shape are
required to make the gradient more
uniform?
What tweaks to the pole shape are
required to make the gradient more
uniform?
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
Future Work
Complete yoke shape optimisation Include field clamp plates Model both magnets together
Finalise current-turns in combined model Build and test prototypes
Requests for quotes were sent out last week Comparison of codes
CST & OPERA results must agree Interface: magnet codes tracking codes
EMMA Magnet Design – Ben Shepherd FFAG 2007 - Grenoble, April 12-17 2007
Conclusions
EMMA Magnets: design is “nearly finished” Good gradient region should be improved Pole shapes could be tweaked further
Prototypes are in the process of being ordered Tests from these will validate 3D codes
Acknowledgements: Takeichiro Yokoi Neil Marks Neil Bliss