Considerations on 3 - 4 GeV H- injection for PS2

• Basic considerations• Injection system geometry

– Chicane– Injection– Extraction of H0 and H- beams

• Foil issues– Thickness & efficiency– Heating– Emittance blow-up

Basics

CNGS LHC

Total p+ injected 1.5 x 1014 7.2 x 1013

Turns@1.2 x 1012 p+/turn 135 60

Turns@6.0 x 1011 p+/turn 270 120

Injected emittance (um.n) 0.5 0.5

Final emittance H/V (um.n) 15.0/8.0 3.0/3.0

40 mA SPL

20 mA SPL

Injection system geometry

• Had assumed in 1.5 FODO cells (a la JPARC)

-100

-50

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682 686 690 694 698 702 706 710 714 718S [m]

X [

mm

]

BS: 11.5 mradMSI : 25 mm, 200 mrad

QFA QDA

QD

H- INJECTONSEPTUM

3-4 GeV H- injection for PS2

H-/H0 DUMPSEPTUM

To dump lineH-

QF

beam

Injection septum½ cell

Chicane & stripping foil ½ cell

Dump septum ½ cell

Limits

• Lorentz stripping– Injection septum <0.14 T

• Bend angle ~9 mrad/m• Need full half-cell for septum

– Injection chicane• First 2 dipoles deflect main H- beam – need <0.14 T

• Second 2 see unstripped H0 and H- - could make stronger?

Chicane ½ cell geometry~

23 m

m

• 23 mm chicane bump, 23 mm painting bump (4 other magnets….)• 1.0 m long magnets with 2.5 m centres give ~9 mrad and ~23 mm• Foil edge at about 40 mm – just outside ‘aperture’ (50 mm x max)

1.0 m 9.0 mrad QFQD

~70

mm

Fo

il 1Fo

il 2

2.5 m1.0 m

10.0 m beam

Injection septum ½ cell geometry

• Covered by Wolfgang– ½ cell full of septum - at limit (8 m magnetic in ~10 m drift)– Seems preferable to not rely on injecting through quad coil

window (aperture, extra fields, constraints, quad design)

60 m

m

570

mm

Difficult (but maybe not impossible!) to get past upstream quad yoke and into the downstream quad aperture

2.0 m, 18.0 mrad

beam

H-/H0 dump ½ cell geometry

• Can use ‘real’ septum (>1.0 T); easy to get beam out (2 m 130 mrad)• ~5 kW of protons – need large acceptance TL….or internal dump?• Only use about half of the ½ cell

QD

beam

To dump

2.0 m, 130 mrad

~3.0 m

QF

Alternative geometries…

• Also will investigate injection system insertion between doublets (a la SNS)?– flat functions between lattice quads– Fit whole injection system (septa, chicane)

into this drift– Avoid problems with lattice quads– Generate enough space in insertion?

Painting and foils

CNGS beam, 135 turns LHC beam, 60 turns

• Linear painting functions with anti-correlated H/V

Foil thickness & efficiency

- assume thickness of 400-500 ug/cm2 and H0 yield of about 2%- detailed scaling needed to check 3 and 4 GeV cases

4 GeV

Foil heating and hits

CNGS 270 turns,1540 K, 17.8 hits/p+CNGS 135 turns,1210 K, 9.7 hits/p+

LHC 120 turns, 1240 K, 17.2 hits/p+

T ~1540 K!

LHC 60 turns, 820 K, 10.2 hits/p+

Assuming injected H- beam deposits ~2.4 times dE/dx as p+ (p+ dE/dx is 1.75 MeV/g/cm2

, e- dE/dx is 1.2 MeV/g/cm2)

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foil delta T [K]

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foil delta T [K]

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foil delta T [K]

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m]

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foil delta T [K]

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Repeated heating

• Not an issue for 2.4 s period (0.5 s gives extra 100 K)

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T [

K]

t [s]

Emittance growth and losses (3 GeV)

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Foil hits

rela

tive

beam

loss

Relative beam loss vs foil hits for 3 and 5 um foil

3 um f oil

5 um f oil

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1

Foil hits

norm

alis

ed e

mitt

ance

mm

.mra

d

Delta en vs foil hits for 3 um foil (500 ug/cm2)

delta e

n x

delta en y

Loss < 0.02 %n < 0.1 .mm.mrad

…not an issue

Foil effects summary

CNGS LHC

20 mA 40 mA 20 mA 40 mA

Injection turns 270 135 120 60

Paint bump H [mm] 27 27 27 27

Paint angle V [mrad] 0.86 .86 0.45 0.45

Paint fall time [turns] 860 430 950 500

H/V rms n [mm.mrad] 14.7 / 7.8 14.7 / 7.7 2.7 / 2.8 2.5 / 2.8

Foil hits (/p+) 17.8 9.7 17.2 10.2

Foil T (K) 1540 1210 1240 820

H/V n from foil [mm.mrad] <0.05 <0.05 <0.05 <0.05

Beam loss from foil [%] 0.02 0.01 0.02 0.01

Conclusion/outlook/remarks• First studies under way…system is a challenge!

• Try and fit into FODO structure– H-painting with 23 mm bump – 4 magnets outside chicane ½ cell– Vertical painting with ~1 mrad angle – bumper/kickers needed

• ~500 g/cm2 foil assumed to be needed (~3 m thick)– Few % of unstripped H0 to extract with septum and transfer to dump - ~5 kW

• Painting very ‘slow’ to maintain emittance (need ~1000 turns fall for LHC) – Increasing injected turns by factor of 2 makes injection more difficult

• Foil hits ~double (18 per p+) and high foil heating (>1400 K T) – Emittance blow-up quite small (<0.05 n)– Beam losses from nuclear scattering <2x10-4 level

• To avoid too-high p+ density at foil assumed large (~15 m) s at end of TL (H- beam size).

• Injection system fields max 0.14 T – complicates geometry (fill ½ cells…)

• Much more study and optimization needed….!

Next steps

• More rigorous conceptual design in FODO structure– Use baseline optics– Trajectories, envelopes and apertures

• Warning from SNS – do this properly from start!

– Painting optimisations, foil physics– Dump – internal/external + TL?– Longitudinal painting – dispersion limits for lattice/TL– Large aperture quad feasibility

• Start investigating Doublet insertion – pros/cons

Los Alamos PSR 800 MeV H-