optimizing quadrupole design for ilc final focus
DESCRIPTION
Optimizing Quadrupole Design for ILC Final Focus. Peter McIntyre and Akhdiyor Sattarov Texas A&M University. Presented to ILC BDS Working Group 7/19/2005. ILC Strawman BDS Layout. e-. e+. 2 mrad IR, L* = 3.5 m. 20 mrad IR, L*= 3.5 m. Challenges. Maximize gradient - PowerPoint PPT PresentationTRANSCRIPT
Optimizing Quadrupole Design for ILC Final Focus
Peter McIntyre and Akhdiyor Sattarov
Texas A&M University
Presented to ILC BDS Working Group7/19/2005.
e- e+
ILC Strawman BDS Layout
2 mrad IR, L* = 3.5 m
20 mrad IR, L*= 3.5 m
Challenges
• Maximize gradient
• Move as close as possible to IP – no steel
• Can Q0 be designed to tolerate heat, radiation damage from synchrotron radiation?
These are the same challenges that one faces in optimizing IR for LHC
IR
20 40 60
.02
.04
.06
.08
Q1340 T/m6 m long40 mm aperture
Q2450 T/m10 m long50 mm aperture
Q3450 T/m5 m long50 mm aperture
D18.0 T10 m long56 x 120 mm aperture
D28.0 T10 m long56 mm aperture
m
detector
Q1 is in harm’s way of particle lossesanalog effect for ILC is SR
D1
Q1
Multiplicity ~ f() e-bt Eparticle ~ pt /
So energy flow concentrates strongly down the beam direction.
Design Q1 using structured cable
6-on-1 cabling of Nb3Sn strand around thin-wall inconel X750 spring tube
Draw within a thicker inconel 718 jacket
Interior is not impregnated – only region between cables in winding
Volumetric cooling to handle volumetric heating from particle losses
3 mm
Stress analysis of structured cable
• Motivation, Design and Finite Element Analysis (FEA) of the 6-on-1 cable in conduit
• Nb3Sn: Heat treatment, properties, peculiarities, and how to work with it
• A few words about the conduit and Inconel X 750• Fabrication of the cable and coil• Testing of coils and short samples• Conclusion
Cable designSix strands of Nb3Sn are cabled around a hollow
Inconel X 750 tube
Then the assembly is sheathed in an outer armor that is drawn onto the 6-on-1 configuration
By virtue of its low effective Young’s modulus, the hollow inner tube protects the Nb3Sn wire from external loads
Mesh for FEAApply 100 MPa external load, look at how it distributes in the cable elements.
Strain (Von Mises)
Stress (Von Mises)
Zoom-in of von Mises strain on bottom middle wire
Ironless Quadrupole for Q1
20 mm bore radius, 340 T/m
4.5-6 K supercritical cooling
Impregnate rad-hard filler between cables, but leave interior of cables free for He flow
No insulation between cables
• During normal operation, current follows superconductor.
• During quench, current redistributes as necessary, no voltage can develop, coil quenches as if it were a single turn.
• Insulation is traditionally the weak link for radiation damage.
• No insulation what is next weak link?
Magnetics methodology
Placement of inner turns controls multipoles
Remove turns in regions of Bmax to enhance gradient
Place inner turns at smallest radius possible: G Bmax/R
Cryogenics
• All turns have jackets opened at ends• Liquid helium flows through hollow channels in
cables – superfluid or supercritical?• Zone flow in radial regions of similar Q• Probably can handle Q ~ 100 W/m cryogenic load
kerf cuts around end arcs of each turn
Voids between turns filled to seal He
Structured cable works nicely with BNL’s serpentine coil winding technique
by Brett Parker: 50 mm bore radius, 145 T/m gradient
Fabrication of structured cable
Prototype cabler used to make ~10 m piece lengths. Long lengths can be made at N.E. Electric.
Compressing Inconel sheath on cable
Short lengths prepared by drawing sheath onto cable.
For long lengths, compress sheath in hydraulic die.
Best is to compress to rounded hex final shape.
Bending cable on tight radius does not damage strands
Bending cable ovals outer sheath, ovals inner tube, but leaves the 6 strands round.0.8 mm strand, 1 cm radius OK.Important for small-bore quad!
Other special magnets for LHC IR-any use to ILC?
• block-coil Nb3Sn quads to 450 T/m
• Levitated pole dipole – 8 T bend, ~impervious to swept losses
Q2, Q3: push gradient usingblock-coil Nb3Sn quadrupoles
450 T/m @2 K superfluid cooling (w/iron)
D1: levitated-pole dipole
Cold iron pole piece, warm iron flux return.
Cancel Lorentz forces on coils, pole steel.
8.0 T
4.5 K
This is what optimized superconducting magnets can do for LHC IR
Comparison to baseline IR:
Reduce * 0.15 m
Reduce * 5 km
Reduce # of subsidiary bunch crossings 5
Reduce sensitivity to error fields and placements
Open space for another doublet to fully separate corrections in x, y.
Help me to optimize quads for ILC IRs
• Micro-lattice, what apertures are critical?• What is flux distribution in synchrotron
light, spent beam in first quad region?• How close into detector can an ironless
quad be placed?• Remember: for most optical effects of
multipoles, misalignments, etc., the closer Q0 is to the IP the less the impact on luminosity.