PROGRESS TOWARDS AN OPEN MIDPLANE

SEPARATION DIPOLE

P. Wanderer, BNL

with R. Gupta, A. Ghosh, N. Mokhov

HHH-AMT 12 November 2004

LARP at BNL

• Magnet activity – look at open midplane dipole for LHC IR upgrade with “dipole first” optics and block coils

• Other activities –– Beam instrumentation for present LHC– Accelerator physics– Superconductor development– Superconductor, magnet testing for other US

labs working on LARP

Interaction Region Upgrade

Quad or Dipole first? Single bore or twin bore?

Large crossing angles with superbunches or crab cavities?

Long range (parasitic Beam-Beam collisions?

D1 parameters for this IR

Bdl = 15T x 10m Nb3Sn

– If block coils R&W or W&R coils

• Coil apertures studied: 84, 160, 120 mm

• Field quality – typical δB/B ~10-4

• Magnet & cryo system tolerant of beam heating9 kW (4.5K) fully open midplane + absorber

at temperature >> 4.5K

Some design challenges

• Any “dipole-first” D1: large forces, stored energy, radiation heating

• Open midplane, block coils– less efficient than cosθ coils– Good field quality harder to achieve– Weak vertical support of coil

Issues for R&D program

• Goal: design, build, test proof-of-principal model

• LARP main effort is IR quadrupole limited resources

POP design phase – June 04

• Design for 10m dipole-first D1– June, 2004 LARP review

– Achieved 10-4 FQ, reasonable strain on conductor =>”proof of principal” design

– Complex coil

– ~ 50% of radiation deposited in cold mass

– coil aperture 160 mm

– ~ 1m yoke OD => $$$ to build

– 10m length => $$$ to build

– Needed resources inconsistent with LARP’s focus on quad

LAPAC Meeting, June 16-17, 2004 Dipole Design Status, Ramesh Gupta, BNL

Navigation of Lorentz Forces (1)A new and major consideration in design

optimizationVertical Component of the Lorentz Force Density

Since there is no downward force on the lower block (there is slight upward force), we do not need much support below it, if the structure is segmented. The support structure can be designed to deal with the downward force on the upper block using the space between the upper and the lower blocks.

Vertical Lorentz force density in certain designs

~Zero vertical Lorentz force density line

This allows the lower block to move closer to midplane to improve field quality.

LAPAC Meeting, June 16-17, 2004 Dipole Design Status, Ramesh Gupta, BNL

Navigation of Lorentz Forces (2)(Transferring vertical forces between blocks)

Vertical force comes from the horizontal component of the field : Ly = Jz X Bx.

“Block A” with height more than that of “Block B” straightens field lines that reduce Bx and the downward force on “Block B” by ~50%.

AB

Design with 50 mm midplane gap:

Note: There is a plenty of space for support structure below “Block A”

Moving Block A upward also minimizes the secondary energy deposition from target.

Blocks must be strategically segmented to minimize maximum stress build-up, navigate Lorentz forces, minimize peak fields and optimize field quality.

The task is to demonstrate that it is

possible to satisfy all of the above requirements

at the same time.

Power (mW/g) at L = 5m, 10m

N. Mokhov – LARP Napa Oct 04

Design Progress – October 04

• Relax design parameters:– Horizontal aperture 120 mm– Field quality – δB/B ~10-3

• Separate D1 into two magnets, D1a, D1b

– D1a: ~84mm aperture, develop fully under LARP– D1b: develop only proof-of-principal design– More details on next slide

Starting Point and some estimates on D1A Parameters (to be iterated)

SuperconductingMagnet Division

R. Gupta, BNL LARP Dipole R&D, LARP Collaboration Meeting, Port Jefferson, NY, September 17, 2003. Slide No. 12

I mprovement in Field Quality

A reduction in midplane gap, straightens the field lines atmidplane and improves the field quality.

The actual field quality optimization will be done with thecoil optimization programs. But 10-4 relative error impliesthat a magnetic design with low harmonics is possible.

D1A (to be developed under LARP):

Horizontal Aperture : ~70 mmMagnet Length : ~ 5 meterQuench Field : 15+TYoke outer radius: ~400 mm(or a rectangular yoke with smaller vertical size?)

Design Goal: An open Midplane design with large horizontal and small vertical aperture that includes a warm absorber inside the cold-mass to avoid a major upgrade in CERN cryogenic facility and to remove ~9KW at an affordable cost.

A preliminary design presented at Port Jeff in 9/2003

D1B (NOT to be developed under LARP):

Horizontal Aperture : ~140 mmMagnet Length : ~ 5 meterQuench Field : ~13TYoke outer radius: ~600 mmNote: D1B may have similar Lorentz forces as D1A

LARP Collaboration Meeting, Oct. 19-21, 2004 Dipole for LHC IR Upgrade - Ramesh Gupta

Overall Parameters of the Reduced Aperture Open Midplane Dipole

Preliminary Design

Outer Yoke Radius : 600 mm to 700 mm (old value 1 meter)

Horizontal Coil Spacing : 120 mm (old value 160 mm)

Vertical Coil Spacing : 30 mm (old value 50 mm)

Field errors: 2.10-3, projected to be 5.10-4 with more optimization at +/- 50 mm

(old value 5.10-5 at +/- 36 mm)

Quench Field: ~14.5 T (old value ~15 T)

• Conductor requirements: ~60% of previous design

The above magnet is much smaller than before.However, it still has a significant size.

LARP Collaboration Meeting, Oct. 19-21, 2004 Dipole for LHC IR Upgrade - Ramesh Gupta

A Lower Cost Open Midplane Dipole Proposal

Trajectory in D1

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Z(m)

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• At present, the aperture of D1 is determined by the requirements at the far end of IP.

• We propose dividing each D1 in two dipoles D1A and D1B. We also propose to develop only D1A under LARP.

• D1A will be shorter and will have lower aperture.

• One can also consider raising field in D1A and reducing in D1B. This will balance Lorentz forces better between D1A (higher field, lower aperture) and D1B (lower field, larger aperture).

Beam Trajectory

LARP Collaboration Meeting, Oct. 19-21, 2004 Dipole for LHC IR Upgrade - Ramesh Gupta

A Proposal to Build D1A Under LARP

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Consider increasing the field in the first D1 (D1A), and also consider using HTS there.HTS has a potential to generate higher fields and can tolerate higher heat loads, as well.

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A lower aperture, lower length, lower cost, open midplane racetrack coil dipole that while developing and proving the basic technology, also gets used in LHC IR upgrade

Beam Trajectory

LARP Collaboration Meeting, Oct. 19-21, 2004 Dipole for LHC IR Upgrade - Ramesh Gupta

A Similar Layout Was Considered for VLHC

SuperconductingMagnet Division

Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 11

VLHC-2 IR Layout forFlat Beam Optics

• Optics and magnet requirements (field & aperture) depends crucially on theminimum spacing in the first 2-in-1 IR Quadrupole (doublet optics)

• 23KW of beam power radiated from the IP makes this a natural for HTS.

Beam optics reasons were different, but magnet design reasons were partly similar.

First Magnet (D1A):Higher field, lower aperture, taking help of HTS.

Second Magnet (D1B):Lower field, larger aperture, based entirely on Nb3Sn.

Given the time frame of LHC IR Upgrade, we would consider HTS. However, we

won’t make the design contingent on that.

Hardware Progress – October 04

• Better understanding of conductor – flux jumps, RRR

• New winding machine for reacted Nb3Sn

• Successful test of ten-turn, common coil dipole (DCC016)

• Plan to use LBL subcoils (L ~ 30 cm)

• Use BNL ten-turn fixtures, with spacers, to assemble subcoils

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0 2 4 6 8 10 12Peak Field at the Cable, (T)

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DCC015 A &B Coil RRR ~5DCC016 Coil B RRR~ 92DCC016 Coil A RRR~ 40-50DCC008- ITERITER-Cable Ic

Cable Ic from Strand I c

RRR 5, 2200 A/mm2

RRR 5, 2900 A/mm2

RRR 40-50, 3790 A/mm2

RRR 110, >4650 A/mm2

LAPAC Meeting, June 16-17, 2004 Dipole Design Status, Ramesh Gupta, BNL

Technology Development TestsSub-scale Coils in Open Midplane

StructureShort coils made and pre-tested for other applications can be used in an open midplane configuration to examine the basic technological issues. (BNL/LBL collaboration).

The support structure for this open midplane dipole test will be designed such that it:• Produces similar deflections (after the 1st test with ~zero deflection) • Allows variation in pre-stress• Allows variation in vertical separation

Max. stress in actual magnet:Horizontal = 150-200 MPaVertical = 90-100 MPa

Looking ahead - 1

• Assemble subcoils for test of open midplane concept. (Assemble and test in ~ a year?)

• Plan intermediate steps– Experiments with magnets, especially preload

• Minimum & maximum preload

– Model magnet features

Looking ahead - 2

• Determine parameters for D1a + D1b– Aperture, length, field quality accelerator

physics – Radiation heating LHC cryo ops, heating

calculations

• Design, build, test proof-of-principle model

This program will be reviewed in mid-December