Magnet R

1
Magnet RD for Muon Beam Cooling at FNAL

• Alexander Zlobin
• Fermilab
• Muon Collider Design Workshop,
• BNL
• December 1-3, 2009

2
Contributors

• TD MSD
• N. Andreev, E. Barzi, V.S. Kashikhin, V.V.
  Kashikhin, M. Lamm, V. Lombardo, M. Lopes, A.
  Makarov, D. Orris, A. Rusy, M. Tartaglia, D.
  Turrioni, G. Velev, M. Yu
• APC
• Yu. Alexahin, V. Balbekov, A. Janssen, K.
  Yonehara
• Muons Inc.
• R. Johnson, S. Kahn, M. Turrene et al.
• JLab
• V. Derbenev

3
Intro

• Requirements for a Muon Collider magnet systems
  pose significant challenges beyond the existing
  SC magnet technology.
• The magnets require innovative design approaches,
  new superconductors and structural materials,
  advanced fabrication processes and quality
  control methods, etc.
• Strong focused magnet RD is absolutely necessary
  to support the MC feasibility study
• During last few years Fermilab magnet group
  actively contribute to different MC/NF RD
  focusing on magnets for muon beam cooling
• This year we are also joining the efforts related
  to MC ring and IR magnets brining the experience
  gained during the development and production of
  NbTi IR quads for LHC, and successful HFM program
  developed Nb3Sn accelerator magnet technologies
• This presentation will focused on magnet RD
  results and plans at Fermilab for muon beam
  cooling including
• SC solenoids for 6D muon beam cooling
• ultra-high field HTS solenoids for final cooling

4
6D cooling Helical Cooling Channel
K. Yonehara, S. Kahn, R. Johnson et al.

• Multi-section HCC
• Wide range of fields, helical periods, apertures
• Room for RF system and absorber
• Field tuning more complicate at high fields
• HS concept (FNAL/Muons Inc.)
• Ring coils follow the helical beam orbit
  producing all required field components
• Straight solenoid concept does not work for
  high-field/small-aperture sections

V.S. Kashikhin et al.
M. Lopes et al.
5
HS Technology RD

• Design studies show that it is very complex
  magnet
• significant magnetic forces and stored energy
• must eventually incorporate RF system gt large
  heat depositions
• 4-coil Helical Solenoid Model Program
• Large-aperture HS for the first stage
• High-field HS for the final stage
• The program is partially supported by Muons Inc.
• Goals
• Select conductor
• Develop and validate mechanical structure
  including cryostat
• Develop fabrication methods
• Study and optimize the quench performance and
  margins, field quality, coil cooling scheme,
  quench protection

6
4-Coil Model HSM01

• 4 single-layer SC coils with support structures
  and end flanges.
• Model OD is limited by the VMTF ID.
• Rutherford-type SC cable (NbTi, SSC).
• Inner and outer stainless steel rings provide the
  coil support and intercept the radial Lorentz
  forces.
• At currents 14 kA the fields, forces, and
  stresses in the 4-coil model are close to the
  long HS parameters.

7
HSM01 Quench Performance
The first 4-coil HS model HSM01 reached 85 of
its short sample limit gt close to the design
operation current. No temperature dependence gt
mechanically limited why?
8
HSM01 Field Measurements

• Measured longitudinal and transverse field
  distributions agree well with predictions.
• Some differences in transverse field
  distributions are due to the uncertainty in coil
  position wrt coordinate system gt further care
  will be taken on subsequent magnets to
  fiducialize the coil to facilitate field
  comparisons.

9
HSM01 Autopsy

• HSM01 was cut in several cross-sections to
  evaluate the model design and the quality of
  fabrication

• Findings
• Irregular turn position
• Different turn number
• Poor epoxy impregnation voids
• Thick epoxy layers
• Insufficient coil and splice ground insulation

10
HSM02 NbTi 4-coil model 2

• HSM02 baseline magnetic and mechanical design is
  the same as for HSM01.
• Improved
• mechanical structure and insulation
• cable geometry and insulation
• coil winding and impregnation procedures
• SSC cable re-sized
• Thick side 1.600mm gt1.416mm
• Thin side 1.375mm gt1.271mm
• Avg. 1.413mm gt1.343mm
• Width 12.36mm gt12.945mm
• Cable test gt no degradation
• HSM02 fabrication status
• Preparing for winding
• Test in January 2010

11
Next steps

• Next models will address the issues in
  preparation to the 6D HCC demo model
• Conductor
• MgB2 gt low-field higher-temperature margin or
  operation temperature
• Nb3Sn/Nb3Al gt higher fields higher-temperature
  margin
• Conductor stabilization gt quench protection
• Coil winding
• hard-bend vs. easy-bend gt operation margin
• Cryostat and coil cooling
• Indirect coil cooling gt simple cryostat
• Cable-in-conduit better cooling, simple cryostat

P. Lee, NHMFL
MgB2 6-on-1 cable (FNAL/HyperTech)
12
Hybrid HS Model

• Conceptual design study shows that a Hybrid HS
  may be needed for HCC
• The goal - develop mechanical design and
  technology for HTS section based on G2 tape/cable
  and its assembly with RF and Nb3Sn section
• The work is partially funded and performed in
  collaboration with Muons Inc.

13
Modeling HTS section with RF
14
HS rapid prototyping
15
Updated HCC parameters
Bz_max4-14T gt NbTi/MgB2 and Nb3Sn
16
6D cooling HFOFO Snake

• Yu. Alexahin et al., PAC2009, PAC2007
• HFOFO Helical FOFO channel of alternating
  solenoids (ASOL)
• FOFO-xyz? FOFO with xyz? resonance phase
  advance per cell and one solenoid

Similar conductor and technologies as for HS

• HFOFO-60? (6 cell period, Q??1)
• HFOFO-120? (6 cell period, Q??2) - smaller beta _at_
  absorbers
• FOFO-180? (2 cell period, Q??1) - really low-beta
  FOFO
• HFOFO-270? (4 cell period, Q??3)

17

• Provide input on solenoid design and parameters
  for cooling channel based on HFOFO structure
• Coordinated specifications of magnet system for
  6D cooling demo unit

18
50 T Solenoid Conceptual Design

• Basic Parameters
• Inner bore diameter 50 mm
• Length 1 meter
• Fields 30 T or higher ?
• HTS materials
• Key design issues
• superconductor type
• Jc, effect of field direction in case of HTS
  tapes
• stress management
• quench protection
• cost
• Conceptual design
• hybrid coil design
• coil sections

NbTi
Nb3Sn
BSCCO
19
Strand and Tape Samples
20
HTS/HFS Conductor RD

• Monitoring industry progress to provide input to
  magnet design.
• This includes studies of the engineering current
  density (Je) as a function of
• magnetic field gt up to 28 T (FNAL-NIMS)
• temperature gt from superfluid He to LN
• field orientation (for tapes)
• bending strain
• longitudinal strain gt new fixture being
  commissioned
• transverse pressure gt setup is available.

21
HTS cable RD

• G1 cable
• In FY07-08 fabricated and tested several
  Rutherford cable designs based on Bi-2212 strand
  (OST)
• cabling technology
• effect of cable PF
• Starting from FY2009 continue this work as part
  of National HTS program
• G2 cable
• In FY09 started G2 Roebel cable studies

22
Insert Coil RD

• Present focus on single and double-layer pancake
  coils based on HTS tapes.
• 20 single and double-layer pancake coils made of
  YBCO and Bi-2223 were built and tested in
  self-field and external solenoid
• tape splicing techniques, effect of coil
  impregnation, coil preload
• A modular HTS Insert Test Facility to test up to
  14 double-layer pancake coils inside the 14T/16T
  solenoid (Bgt20 T)
• For the second phase of the coil program, larger
  multi-section HTS coils will be designed,
  fabricated and tested to achieve higher magnetic
  field and force levels.

23
Summary

• The midterm goal of the Fermilabs accelerator
  magnet RD program is to support the Fermilabs
  and national efforts towards the demonstration of
  feasibility of a Muon Collider, with the long
  term goal of building this machine on Fermilab
  site.
• Fermilabs magnet program is making progress in
  all key directions
• Magnet design studies
• Technology development
• HTS material RD
• We collaborate with DOE labs, industries and
  Universities through National HTS Conductor
  program, SBIR and other programs.
• Our efforts are coordinated with National MAP
  RD plan
• Adequate and stable funding is critical for the
  successful magnet RD
• at the present time the program funding is
  provided by MCTF and HFM Program with
  contribution from Muons Inc.
• after MAP approval by DOE we will still need
  substantial contribution from core program and
  other sources