The Large Hadron Collider and the role of superconductivity in one
CERN, 11 th June 2013
HiLumi, WP2 meeting
E. Todesco
FIELD QUALITY IN D2
E. Todesco
CERN, Geneva, Switzerland
This estimate relies on the work presented by R. Gupta in Napa valley HiLumi meeting https://indico.fnal.gov/conferenceDisplay.py?confId=6164
DESIGN OPTIONS
Coil width: either 10 mm RHIC like coil, or 15 mm LHC like coil
One layer since we need space
Margin on loadline 20% minumum
So one has two options
LHC cable, 20% margin, 5 T operational field (7-m-long)
Smaller cable or larger margin, 3.5 T operational field as today, 10-m-long
Larger field, worse field quality
Worse, but perhaps acceptable
First question: do we need the additional 3 m ?
E. Todesco Field quality in D2 - 2
DESIGN CHALLENGES
Large aperture, fixed distance between beams, large crosstalk
Signs of even multipoles
B2 have opposite signs in the ap
B1 have the same sign b2 have opposite sign
E. Todesco Field quality in D2 - 3
ALLOWED MULTIPOLES
General framework : optimization at high field
Allowed multipoles: strong saturation effect, to be compensated with geometric
140 units of b
3
, 20 units of b
5
(5 T), reduced by a factor 2.5 at 3.5 T
I assume that the correction can be done with 20% error, so residual
30 units and 4 units, probably very pessimist
E. Todesco Field quality in D2 - 4
ALLOWED MULTIPOLES
Random part
Allowed multipoles: strong saturation effect, to be compensated with geometric
140 units of b
3
, 20 units of b
5
(5 T), reduced by a factor 2.5 at 3.5 T
I assume a spread of 3-5% of the saturation effect, so
5 units of b
3
, 1 unit of b
5
So spread of saturation dominates over spread of geometric (new situation)
Magnetic shimming could help to reduce the spread of one multipole
E. Todesco Field quality in D2 - 5
Quadrupole
General framework : the magnet has a very large quadrupole component due to two-in-one cross-talk
One could cure at high field with asymmetric coils, but I don’t think this is needed – reproducible effect
So I just give you the numbers … 100 units at 5 T, 40 at 3.5 T
Also in this case a factor 2.5 gained lowering field from 5 to 3.5 T
Random part – also in this case 5% of saturation, so 5 units
E. Todesco Field quality in D2 - 6
OCtUPOLE
General framework : the magnet also has a very large octupole component due to two-in-one cross-talk
This is bad and not so easy to correct
The numbers: 40 units at 5 T, 15 at 3.5 T
Also in this case a faactor 2.5 gained lowering field from 5 to 3.5 T
Random part – also in this case 5% of saturation, so 2 units
E. Todesco Field quality in D2 - 7
E. Todesco
FIELD QUALITY GUESS
8
9
10
11
12
13
14
15
11
12
13
14
15
6
7
8
9
10
Skew
2
3
4
5
6
7
Recombination dipole D2 field quality version 1.2 - June 11 2013 - R ref
=35 mm
Systematic Uncertainty Random
Normal Geometric Saturation Persistent Injection High Field Injection High Field Injection High Field
4
5
2
3
0.000
100.000
0.000
0.000
40.000
0.000
0.000
100.000
0.200
110.000
-140.000
-14.200
95.800
-30.000
0.727
0.000
40.000
16.000
-20.000
-1.000
15.000
-4.000
2.000
0.365
5.000
5.000
2.000
1.000
0.200
0.727
0.126
0.365
5.000
5.000
2.000
1.000
0.000
0.800
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
-1.000
-0.700
0.000
0.000
0.090
0.000
0.030
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.020
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.100
0.000
0.020
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
-0.200
0.000
0.090
0.000
0.030
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.060
0.165
0.027
0.065
0.008
0.019
0.003
0.006
0.001
0.002
0.679
0.282
0.444
0.152
0.176
0.057
0.061
0.020
0.025
0.007
0.008
0.002
0.003
0.001
0.060
0.165
0.027
0.065
0.008
0.019
0.003
0.006
0.001
0.002
0.679
0.282
0.444
0.152
0.176
0.057
0.061
0.020
0.025
0.007
0.008
0.002
0.003
0.001
0.060
0.165
0.027
0.065
0.008
0.019
0.003
0.006
0.001
0.002
0.679
0.282
0.444
0.152
0.176
0.057
0.061
0.020
0.025
0.007
0.008
0.002
0.003
0.001
0.060
0.165
0.027
0.065
0.008
0.019
0.003
0.006
0.001
0.002
0.679
0.282
0.444
0.152
0.176
0.057
0.061
0.020
0.025
0.007
0.008
0.002
0.003
0.001
Field quality in D2 - 8
FIELD QUALITY GUESS
E. Todesco
13
14
15
10
11
12
7
8
9
4
5
6
Recombination dipole D2 field quality version 1.2 - June 11 2013 - R ref
=35 mm
Systematic Uncertainty Random
Normal Geometric Saturation Persistent Injection High Field Injection High Field Injection High Field
2 0.000
100.000
0.000
0.000
100.000
0.200
5.000
0.200
5.000
3 110.000
-140.000
-14.200
95.800
-30.000
0.727
5.000
0.727
5.000
0.000
40.000
0.000
0.000
40.000
2.000
16.000
-20.000
-1.000
15.000
-4.000
0.365
0.000
0.000
0.000
0.090
0.000
0.800
-1.000
-0.700
0.000
0.000
0.000
0.020
0.000
0.100
0.000
0.020
0.000
-0.200
0.000
0.090
0.060
0.165
0.027
0.065
2.000
1.000
0.060
0.165
0.027
0.065
0.126
0.365
0.060
0.165
0.027
0.065
2.000
1.000
0.060
0.165
0.027
0.065
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.030
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.030
0.000
0.000
0.000
0.000
0.008
0.019
0.003
0.006
0.001
0.002
0.008
0.019
0.003
0.006
0.001
0.002
0.008
0.019
0.003
0.006
0.001
0.002
0.008
0.019
0.003
0.006
0.001
0.002
Field quality in D2 - 9
CONCLUSIONS
I provided the worst case of field quality
We need to know what to optimize
Is b2 a problem ?
Is b4 to be reduced ? – this can be done with iron shaping
Hard to reduce both b2 and b4 …
If the b3 and b5 are too large, we should go to longer magnet
Real estimate of the possiblity of controlling saturation and its spread is not easy to judge
Going from 5 T to 3.5 T (and from 7 m to 10 m) one gains a factor 2.4 in critical multipoles, both systematic and random
E. Todesco Field quality in D2 - 10
