USPAS - Alternate High-Field Magnet designs for Particle Accelerators [presentation slides]

45 Pages·2000·2.413 MB·English

by  R. Gupta

Superconducting
Magnet Division
Alternate High Field Magnet
Designs for Future Accelerators
Ramesh Gupta
Superconducting Magnet Division
Brookhaven National Laboratory
Upton, NY 11973 USA
Ramesh Gupta, BNL, June, 2000
VLHC: The Challenge is the Cost
Superconducting
Magnet Division
VLHC can be built with the present technology.
But the cost may be too high.
To change the cost substantially, we have to do things differently.
• Superconducting dipoles are the cost and technology driver and require a
large lead time for magnet R&D.
• Their cost is significant (~1/4 of the total machine cost).
• Critically examine all major components and sub-systems. See if some of
them can be eliminated. Alternate “magnet system design” can be spring-
board for bringing additional savings in the overall machine cost.
Ramesh Gupta, BNL, June, 2000
Present Magnet Design and Technology
Superconducting
Magnet Division
Tevatron Dipole HERA Dipole
• All magnets use Nb-Ti
Superconductor
• All designs use cosine
theta coil geometry
LHC Dipole
RHIC Dipole • The technology has
been in use for
decades.
• The cost is unlikely to
reduce significantly.
Ramesh Gupta, BNL, June, 2000
The Basic Guiding Principles for
Superconducting An Innovative R&D Program
Magnet Division
Remember the next machine is 10+ years away
In addition to maintaining the expertise we have acquired,
e
this is also a unique time to explor
(cid:135)Explore alternate concepts and technologies
(cid:135)Explore other conductors (Nb Sn, HTS) for high fields
3
(cid:135)Use the “Magnet R&D Factory” approach:
- faster turn-around is important to try ideas outside the “comfort zone”
Ramesh Gupta, BNL, June, 2000
High Field Magnets and High
Temperature Superconductors (HTS)
Superconducting
Magnet Division
American Supercondctors
Long Lengths
For high field LTS
2
m
magnets, we are
m
HTS
interested in the /
HTS
A
“Low Temperature”,
,
c
J
performance of
“High Temperature
Superconductors”.
At very high fields,
HTS have a better
performance.
Applied Field, T
Ramesh Gupta, BNL, June, 2000
High Field Magnets and High
Temperature Superconductors (HTS)
Superconducting
Magnet Division
For high field
Short Lengths (100 meter)
magnets, we are
interested in the
“Low Temperature”,
characteristic of
“High Temperature
HTS Superconductors”.
But what really matters is the engineering current density (J )!
e
Ramesh Gupta, BNL, June, 2000
High Temperature Superconductors (HTS)
in Accelerator Magnets
Superconducting
Magnet Division
• HTS in accelerator magnets: An exciting possibility, BNL
is leading this initiative
• Applications: vlhc & muon colliders/storage rings
• May allow higher fields, higher operating temperature,
higher heat loads and less stringent operating conditions
• However, the conventional magnet designs are not well
suited for them (HTS is too brittle for them)
End of a conventional magnet
Ramesh Gupta, BNL, June, 2000
Common Coil Design
(The Basic Concept)
Superconducting
Magnet Division
• Simple 2-d geometry with large
bend radius (no complex 3-d ends)
• Conductor friendly (suitable for
brittle materials - most are - Nb Sn,
3
HTS tapes and HTS cables)
Coil #1 • Compact (compared to single
aperture LBL’s D20 magnet, half
the yoke size for two apertures)
1
#
m • Block design (for large Lorentz
a
e
B
forces at high fields)
• Efficient and methodical R&D due
to simple & modular design
# 2 • Minimum requirements on big
m
a
e
B expensive tooling and labor
Coil #2 • Lower cost magnets expected
Main Coils of the Common Coil Design
Ramesh Gupta, BNL, June, 2000
Field Lines at 15 T in a
Common Coil Magnet Design
Superconducting
Magnet Division
Aperture #1
Aperture #2
Place of
maximum iron
saturation
Ramesh Gupta, BNL, June, 2000
Investigations for Very High Fields
(to probe the limit of technology)
Superconducting
Magnet Division
Vary aperture after the coils are made
a unique feature of this design
Lower separation (aperture)
T
3 reduces peak field, increases T.F.
.
6
1 => Higher B
= ss
k
p May not be practical for machine magnet
B A
k
,
T 5 but an attractive way to address
2 2.
6. 1 technology questions
1 =
= 2
I
Bss A, Determine stress degradation in an actual
; k conductor/coil configuration
e
r 5
u .
8
rt = Max. stress accumulation at high margin
e 1
p I region
a

m
When do we really need a stress management
m
0 scheme (cost and conductor efficiency
1
questions), and how much is the penalty?
Simulate the future (better J ) conductor
c
Ramesh Gupta, BNL, June, 2000