Direct Double-Helix Magnet Technology
R.B. Meinke, J. Lammers, P. Masson, G. Stelzer
Advanced Magnet Lab, Inc. Palm Bay, Florida
Double Helix Coil Configurations
Currents described by the following equations produce axial and
transverse magnetic fields simultaneously:
Superimposing two such currents with appropriate direction allows
cancelation of either the axial or the transverse magnetic field.
Dipoles for Horizontal and Vertical Beam Steering
ABSTRACT
Magnets for beam steering, focusing and optical corrections often have demanding requirements on
field strength, field uniformity, mechanical robustness and high radiation strength.
The achievable field strength in normal conducting magnets is limited by resistive heating of the
conductor. A break-through magnet technology, called “Direct Double Helix” allows operation at current
densities in excess of 100 A/mm2.
The conductive path that generates the magnetic field is machined out of conductive cylinders, which
are arranged as concentric structures. Geometrical constraints of conventional conductors, based on wire
manufacturing, are eliminated.
The coolant, typically water or air, is in direct contact with the conductor and yields very high cooling
efficiency.
Based on Double-helix technology the conductor path is optimized for high field uniformity for
accelerator magnets with arbitrary multipole order or combined function magnets.
Advanced machining technologies, using lasers or electron beams, enables unprecedented magnet
miniaturization.
With only metals and ceramic materials these magnets could operate at temperatures of several
hundred degrees Celsius and can sustain high radiation levels.
Concentric dipole coils for horizontal and vertical beam steering.
Beam aperture ≈ 20 mm --- Magnet OD ≈ 40 mm
Material Choices
Quadrupole
Dipole
Pure transverse magnetic fields of arbitrary multipole order can be
produced. Coils based on this technology have high field uniformity
without the use of field forming spacers as required in other winding
configurations.
The conductor surrounds the coil aperture and yields intrinsic
mechanical stability to the coils.
Normal conducting coils using Cu or Al conductors
Carbon or tungsten conductor for high operational temperatures
Advanced composite conductors (carbon nanotubes in Cu matrix)
Graphene conductor for small coils
HTS and LTS conductors
Ceramic support structures for high temperature and high radiation
level applications
Electrical
Cond. Thick. Current
(mm)
(A)
C
o
a
t
e
d
Cu
Magnet Types
Direct Double-Helix Technology
0.56
0.56
0.56
0.56
0.56
0.56
5.5
7.0
8.5
10
11
13
Water Cooling
Power Jc Peak Flow Rate T Inlet T Peak Delta T
(Gauss)
(W)
(A/mm2) (gpm)
(C)
(C)
(C)
73
120
181
251
309
369
39
49
60
70
78
92
1
1
1
1
1
1
Electrical
Machine current path out of conductive cylinder instead of
conventional winding technique using wires, cables, or tapes
Coils are self supporting or
stabilized with support
structures
Dipoles for beam steering
Quadrupoles for beam focusing
Combined function magnets (typical dipole + quadrupole)
Twisted dipoles for polarized beams
Twisted quadrupoles for multi-directional focusing
Cond. Thick. Current
(mm)
(A)
Miniture dipole for medical applications
The tool path through the material forms the
insulator between adjacent winding turns.
The set of concentric cylinders forming the DDH coils enable
highly efficient cooling of the conductor with the following
unique features:
Minimum back pressure for coolant (conventional hollow Cu
conductors require high water pressure)
Small temperature gradient along cooling path
Conductor cooling from ≥3 sides possible
Conductive coil support structure for further increase in
cooling efficiency
39.6
42.7
46.3
51
55
44
4.6
7.7
11.3
16
20
34
Water Cooling
83
105
128
150
165
195
Field
Power Jc Peak Flow Rate T Inlet T Peak Delta T
(Gauss)
(W)
(A/mm2) (gpm)
(C)
(C)
(C)
Cu
20
25
30
35
40
45
174
268
387
515
692
792
38
48
58
67
77
86
1
1
1
1
1
1
35
35
35
35
35
35
41.1
44.4
47.8
52.2
57.5
57.0
6.1
9.4
12.8
17.2
22.5
22.0
308
385
463
540
617
694
Cu
Cu
2.05
2.05
55
60
578
714
106
115
1
1
10
10
62.5
77.8
52.5
67.8
848
925
Test data for beam steering magnets
CONCLUSIONS
Field generating current path machined out of conductive cylinders
Complete control over conductor cross section along its path
Constraints caused by wire manufacturing eliminated
Very high cooling efficiency with insignificant thermal gradients
Current densities in excess of 100 A/mm2 in DC operation of normal
conductors achieved
High field uniformity due to Double-Helix winding configuration
Magnets with arbitrary multipole order and combined function
Highly cost-effective since no magnet-specific tooling is needed
Unprecedented miniaturization of coils feasible
High radiation hardness based on metals and ceramic materials
Advantages of Machined Conductor
Variable conductor cross section
Rectangular conductor; ~25% larger than round wire in same
space
Choice of conductor material not limited by wire or cable
manufacturing process
No bending radius limitations; no change in cross section due to
bending
Intrinsic robustness of winding -- conductors surround coil
aperture
No field forming spacers required
Cost effective -- no magnet specific tooling
35
35
35
35
35
10
2.05
2.05
2.05
2.05
2.05
2.05
C
o
a
t
e
d
Conductor Cooling
Field
Left: Temperature distribution along one winding turn.
Right: Current density distribution in one arc section.
Advanced Magnet Lab, Inc.
1720 Main Street, Palm Bay, Florida 32905
Tel. 321 728 7543, www.magnetlab.com
Quadrupole Magnet
E-mails:
rbmeinke@magnetlab.com
pmasson@magnetlab.com