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Superconducting Ultimate-Storage-Ring Design

Weiming Guo, Animesh Jain

NSLS-IIFLS workshop, March 5, 2012, J-Lab

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Outline

•Introduction to the existing designs: prospects and difficulties

•Lattice-structure study: reasons for superconducting

•A design with superconducting magnets

•Approaches to chromaticity correction

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The Basic Idea

Experimental Hall

>10 girders installed

*A. Ropert, EPAC’2000

ε~θ3~(1/N)3

Increase the number of cells;

Or, split the dipole and add focusing

Elements.

To go from 2nm to 8pm: 6 slices

ESRF Multi-bend lattice with 0.3nm emittance

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Existing Designs

Type I: qudrupole triplet + a dipole

Type II: a focusing quadrupole + a defocusing dipole

US7-Michael Borland

SLAC, PEP-x design

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Why Superconducting

Superconducting magnets

QC: QUAD,L=0.4,K1=12.55

DC: DRIF,L=0.1

BH: CSBEND,L=0.2,ANGLE=0.00965,K1=-8.21

Beamline: (BH,DC,QC,DC,BH)

Normal magnets

QC: QUAD,L=0.4,K1=2.1

DC: DRIF,L=2.080831419590222

BH: CSBEND,L=0.2,ANGLE=0.00965,K1=-1.911

Beamline: (BH,DC,QC,DC,BH)

US7: Cx=-1.25,

~6m per dipole

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Limitations of Superconducting Magnets

• Strength: 6T, 30mm bore radiusQUAD: 180 T/m, Sextupole: 1500-3000 T/m2

• Magnet length: the longer the better, ~0.5m• Magnetic field: coil dominated, combined function magnets are possible• Magnet to magnet separation: 0.1m• Precision alignment: difficult• Cryogenic module: 5-8m, 0.5 m separation

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A Compact Design

Circumference: 828m Emittance: 6.4 pm

Number of straights: 60 straight length: 6m

Chromaticity: 336/ 222 Momentum spread: 7x10-4

All quadrupole, no dipoles;

emittance reduction: >63

Sextupole scheme:

Combined quadrupole and sextupole

BC: K2=-6551.7

QC: K2=3638.9

On-momentum dynamic aperture

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Alternative Sextupole Scheme

Requirements to the long straight:

large βx , βy , ηx ;

βx , βy variation;

>2π phase advance for nonlinear correction

The long straightOne-third of the ring, and the parameters

Negative effects

Emittance is mostly produced in the long

straights; nonlinear terms become large due

to large beta functions.

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Other Long-Straight Schemes

2π-transformer

Dispersion flips signsextupole flip sign

nonlinearity adds up

Mini-DBA

Very difficult to obtain

large dispersion due to small H

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Summary

•Advantages of using superconducting magnets for the ultimate-storage-ring design: less chromatic, more compact

•Showed a preliminary design

•Using long straights to correct chromaticity looks promising.