Low Field Magnet R

1
Low Field Magnet RD

• Purpose
• Design, fabricate and test a superferric magnet
  for a
• VLHC Stage 1, P-P accelerator of 40 TeV cm
  energy
• Other applications possible e.g. as a higher
  energy
• injector for the LHC factor-two energy
  upgrade
• As this work is winding down the goal is to
  capture the
• intellectual and technological advances by
  finishing
• this RD program and publishing results
• Participants
• G.W.Foster, S.Hays,
  Y.Huang, V.Kashikhin, E.Malamud,
• P.O.Mazur, A.Oleck,
  H.Piekarz, R.Rabehl, P.Schlabach,
• C.Sylvester, J.Volk
  (FNAL) , and
• M.Wake (KEK)

2
Intellectual and Technological AdvancesResulting
from the Superferric Magnet RD

• Magnet assembly and welding technique
• 100 kA dc power supply
• 100 kA dc power leads
• Operation of a superferric magnet model
• Magnetic measurements for a small bore
• Accelerator quality magnetic measurements

3
Basic Features of the Magnet

• Combined function
• gradient dipole
• 2-in-1 warm iron yoke
• 2 Tesla bend field
• 20 mm pole gap
• Alternating gradient 65m
• (half-dipole length)
• Single-turn 100 kA
• transmission line conductor
• Operating temperature up
• to 6.5 K
• Warm beam pipe vacuum
• system

4
Lamination Design Study
Slots
Top Pole
Bottom Pole

• Use of slots in poles helps to reduce saturation
  sextupole defect and gradient shift
• Results from a water
• cooled magnet model
• showed that overall
• B-field stability is
• /- 0.02 within the
• 20 mm pole gap
• The slides show that
• the field shape did not
• change between 1.25 T
• and 1.8 T

5
Test Magnets Half-Cores

• Test magnet half-cores of
• 1.5 m, 3 m and 6 m length
• are being fabricated at the
• Efremov Inst., St. Petersburg,
• Russia
• The laminations are produced
• using high precision die and
• assembled into half-cores with
• tolerances lt 0.02 mm
• Expected delivery to Fermilab
• in July, 2002

Top and bottom half-cores
6
Transmission Line Conductor RD

• All conductor types to be used for the
  superferric magnet were successfully tested in
  our Superconductor Test Facility in MW9. A
  magnetic field from a dipole magnet generated up
  to 100 kA current in the superconducting loop

7
Transmission Line Conductor RD

• All conductor lines use invar tubing for
  cryopipes to minimize shrinkage
• Conductor properties
• - Drive bus
• - Braid of 288 SSC outer dipole strands
• - 100 kA current _at_ 1 Tesla at 6.5K
• - LHe channel 25.3 mm dia.
• - Return bus
• - As above, except for the increase of
• the LHe channel dia. to 36.8 mm in
• order to minimize the pressure drop
• - Corrector space conductors
• - 9 Rutherford cables (270 SSC inner dipole
  strands)
• - 100 kA current _at_ 1.5 Tesla at 7 K
• allows to place drive and return
• buses at 5cm of each other

8
Transmission Line Conductor RD

• Conductor assembly
• Swaging technique (pulling a series of carbide
  steel balls through the LHe channel) was
  successfully used to fix conductor firmly inside
  the cryo-pipe and thus greatly simplifying the
  assembly process
• Status
• - All components exist to assemble up to 100
  m of a drive conductor
• - In all upcoming tests the drive conductor
  will also be used as a return bus
• - All bent conductor sections will be made of
  assembly of 9 SSC inner dipole cables ( all
  components exist, assembly in progress )

Assembly of a 6 m long transmission line
conductor
9
Transmission Line Conductor RD

• Conductor splicing techniques
• Used aluminum block heaters with large
  compression force on the splice
• - Spliced conductors
• ( i) 9 to 9 Rutherford cables,
• 30 cm length, 3.6 kW power
• (ii) Braid to 8 Rutherford cables
• 10 cm length, 1.2 kW power
• - Splice resistance
• Less than 0.02 nOhm ( limit of the
• measurements )
• - Power dissipation at 100 kA
  
• Less than 0.2 W per splice
• ( limit of the measurements )

10
Magnet Assembly Technique RD

• Will use laser technology
• to weld connecting plates
• between half-cores
• Laser welding reduces the heat
• affected area by a factor of 100
• with respect to TIG welds
• Welding sequence
• 1. Weld split connecting
• plates to half-cores
• 2. Weld connecting plates
• together through slots in
• the spacer bar
• A key in the connecting plates
• prevents spill of the molten steel
• onto the cryostat wall

11
Magnet Assembly Technique RD

• Preset press on the half-cores assembly 5 T/m
• Expected tension after welding gtgt 10 T/m
• Preset press on the
• conductor cryostat
• 200 kG/m
• Cold pipe supports made
• of ultem (large cost
• reduction) expected shrinkage 0.1 mm/peg
• A preset press of 200
• kG/m compensates for
• shrinkage of pegs

Cold Pipe Supports Shield
Welding Press Fixture
Spacer Bar
Conductor Cryostat
Conductor He Channel
Connecting Plates
12
Magnet Assembly Technique RD
Laser beam will move between press posts (skip
welding mode) and then weld connecting
plates through the slots in the spacer
bar. Lamination damage due to laser generated
heat was successfully tested. The forthcoming
test is to determine tension after laser weld.

• A 3.5 kW laser mounted on a 4m long gantry at
  Laser Mach. Inc., Somerset, WI that will be used
  for welding our magnets.
• The YAG or CO2 laser will make 3 mm deep welds at
  a speed up to 4 cm/s with positioning precision
• down to 10 microns

Laser Head
Gantry
13
Magnet Test Arrangement

• In order to test the VLHC superferric magnets at
  Fermilab we
• had to design and build both the 100 kA
  power supply and the 100 kA power leads

14
100 kA DC Power Supply RD

• Rectifier cells
• 400 V x 60 A ? 1.5 V x 10 kA
• 15 cells assembled and
• individually tested
• 10 cells successfully tested
• in a parallel operation at
• 100 kA
• A B-field regulation system
• was successfully tested
• Work in progress on better
• than E(-4) regulation

15
100 kA Power Leads RD

• Design complete
• 208 Cu 1.65m long,
• 6 mm dia rods/lead
• Horizontal LHe flow
• (anodized Al baffles
• force flow up/down
• along the lead)
• LHe consumption
• - 3 g/s standby
• - 6 g/s at 100 kA

16
100 kA Power Leads RD

• Performance projection
• Optimized for 90 kA, a
• nominal current of the
• VLHC magnet
• At 100 kA unstable with
• LHe flow lt 5.6 g/s
• The resistance of the solder joint of the rods at
  the cold end is the key factor to keep LHe flow
  at the projected level. Based on preliminary
  tests and analysis we predict that this
  resistance in both leads will be in a nano-ohm
  range at LHe temperature, thus being very
  satisfactory.

17
100 kA Power Leads RD
A close-up view of SC cables and Cu rods
soldered to the cold end of the current lead

• Assembly of a current lead required simultaneous
  soldering of 202 copper rods to both warm and
  cold ends as well as soldering of 9 SC cables to
  the cold end. It was done by heating-up the whole
  assembly to 400 F in IB2 oven.

18
Cryogenic System for Magnet Tests

• Two 500 l dewar LHe supply system. A cryobox
  (used in MW9 tests) allows to swap dewars during
  system cool-downs.

19
Cryogenic System for Magnet Tests Rd

• Cryogenic electrical
• insulators (new compared to MW9 system)
• Sizes from 0.25 dia. (Instr.)
• to 3 dia. (Leads GHe exit)
• All insulators developed and
• fabricated at MTF Products
• - Ceramics with invar sleeves
• - 6 kV breakdown voltage
• (3 kV expected for VLHC)
• Bellows are installed above and
• below the insulators to protect
• ceramics to invar tube joints during
• cooldown and warmup processes

A part of the Instrumentation Tower design
Insulator
Bellows
20
Magnetic Measurements RD

• Multi Hall Probe Station
• Fabricated at Efremov Inst.,
• St. Petersburg, Russia
• - 50 elements ( in each beam
• gap ) arranged in 3 planes
• to facilitate measurement
• of higher harmonics
• - Laser tracking system for the
• station position on the magnet
• - Radio-wave communication
• for transferring data
• Hall Probe Station tests are
• in progress at MS6

Laser Receptor
Hall Probe Holder and Carriage, (same is on the
opposite side)
Pole Gap
Structure imitating Magnet
21
Magnetic Measurements RD

• Will use tangential coils to measure higher
  harmonics
• of the B-field
• Coil parameters
• - Length 3m 6m
• - Opening angle 15 deg
• - Number of turns 20
• Preliminary design and
• cost estimate done

Neoprone Elastoner Springs
Vespel SP-211 Probes
Vespel Sleeve Bearing
Nylatron GS
22
Schedule and Manpower

• FY 2002 schedule
• Assemble test system in MS6
• Commission 100 kA power supply
• Commission 100 kA power leads
• Assemble and install 1.5m magnet
• Test system and magnet operations
• Measure magnetic field quality
• using multi-Hall probe station
• Complete design of MS6 to MW8 conductor transfer
  lines and make final design of tangential coils
• FY 2002 manpower
• 1 FTE Scientist
• 1.5 FTE Engineer
• 1 FTE Technician

MW8 TUNNEL
MS6 ENCLOSURE
23
Schedule and Manpower
MS6 Enclosure

• FY 2003 schedule
• Install MS6 to MW8 conductor
• transfer lines (10 m length)
• Assemble and install in MW8
• the 3m and 6m magnets
• Fabricate tangential coils
• Test new magnets operation
• Perform B-field measurements using tangential
  coils
• Publish results
• Secure MS6 and MW8 for
• possible future superferric
• magnet studies
• FY 2003 manpower
• 0.1 FTE Scientist
• 0.3 FTE Engineer
• 1 FTE Technician

MW8 Enclosure
Conductor transfer line to be assembled in FY 2003
24
Summary and Conclusions

• Design and fabrication of all major components
  (magnets, power leads and power supply) is nearly
  complete and the test system with 1.5 m magnet
  will be assembled and commissioned in FY 2002
• The 3m and 6m magnets (together with the
  tangential coil magnetic measurement system) will
  be assembled and installed in MW8 in the first
  half of FY 2003
• The accelerator quality magnetic measurements of
  the VLHC superferric magnets will conclude in FY
  2003
• With rather small effort in FY 2003 the
  intellectual and technological advances resulting
  from nearly 4 years of the superferric magnet RD
  will be captured and available for publication