intensity limits and beam performances in the h igh- e nergy s torage r ing

9/15/05 A. Lehrach, HESR, Coulomb ’05 1

Intensity Limits and Intensity Limits and Beam Performances in the Beam Performances in the HHigh-igh-EEnergy nergy SStorage torage RRingingHESR-Consortium: FZJ, GSI, TSL, and Univ. of Bonn and Dortmund

HESR Layout Beam Equilibrium Beam Losses and Luminosity Other Intensity Limiting Effects Summary & Outlook

http://www.fz-juelich.de/portal/index.php


Accumulation and Accelerationof Antiprotons at FAIR

Antiproton production

Linac: 50 MeV H-

SIS18: 5·1012 protons / cycle SIS100: 2-2.5·1013 protons / cycle

26 GeV protons bunch compressed to 50nsec

Production target: antiprotons 3% momentum spread

CR: bunch rotation and stochastic cooling at 3.8 GeV/c

RESR: accumulation at 3.8 GeV/cProduction rate

p2·107/s (7·1010/h) antiprotons



HESR Layout

One half of the arc super-periodMomentum range 1.5 – 15 GeV/c6-fold symmetry arcs with a length of 155 m each.Mirror symmetric FODO structure designed as pseudo second order achromat with dispersion suppression.Two straight sections of 132 m length each. Ring circumference 574 m.

Qx = 12.16 Qy = 12.18γtr = 6.5i



“High Resolution Mode” “High Luminosity Mode”

Momentum range Up to 9 GeV/c Full momentum range

Number of antiprotons 1010 1011

Target thickness 4·1015 cm-2 4·1015 cm-2

Peak luminosity 2·1031 cm-2s-1 2·1032 cm-2s-1

Beam emittance 1-2 mm mrad 1-2 mm mrad

Momentum resolution p/prms = 10-5 p/prms = 10-4

Beam Cooling Electron Cooling Stochastic Cooling

Experimental RequirementsPANDA (Strong Interaction Studies with Antiprotons):

Momentum range: 1.5 to 15 GeV/c



12 m

Charger: H- Cyclotron

30 m

Solenoid

High voltage (8 MV) tank

HESRbeam

Feasibility study of magnetized electron cooling for the HESR 9/2003

(Budker Institute, Novosibirsk, RUS)

HESR Electron Cooler

Electron Cooler

Cooling section

HV section electrostatic accelerator 0.45 - 8 MV, up to 2 A charged by H- beam Cooling section sc solenoid length 30 m magnetic field 0.2 - 0.5 T straightness 10-5

beam diameter 6 - 10 mm Bending section electrostatic up to 21 KV/cm bending radius 4 m

Acceleration column

8 m



Electron Cooling ForceParkhomchuk model (*particle frame):

Effective Coulomb log:

Coolig rate:

Longitudinal force (momentum spread ):

Fit to Parkhomchuk formula

CELSIUS measurement Dec. 2004

veff* 104 m/s

Measurements at CELSIUS seem topredict an accuracy of the longitudinal Parkhomchuk force within a factor of 2

2/32*2*

***

))()(()(

effC vv

vKLvF

10ln max

bbLC

3*

3

20

21

0 )(4

eff

eceep

vc

ALcnrrZ

2/322

31

0|| )(

eff

effeF



Pellet target (WASA@CELSIUS)

Formation of frozen hydrogen pellets

H2 (=0.08 g/cm3)60000 pellets/s

<n> = 5x1015 cm-2

d=30 m

1 mm

HESR: Target will be switched on after injection and cooling/IBS equilibrium Transverse heating is required to ensure 1 mm spot size on the target

Beam spot



Beam HeatingTransverse emittance growth in the target:βx,y small, D=D‘=0, θrms: Mean Coulomb scattering angle

radrmsrevrmsyx

yx

xx

cpMeVf

dtd 2

22,

, 1.14,21

Longitudinal emittance growth in the target:βs=h|η|/Qs (bunched beams), δrms: Mean relative momentum deviation

revrmsss f

dtd 2

21

Multiple IBS: (Soerensen or ‘plasma’ model)

Diffusion constant:

CLcrn ciiIBS2/13

030

2

|| 4

22/3||1

|| ~

IBSIBS

2/3||

||

IBSIBSD

2/5||

21

||

221

~

IBS

x

xIBS

x

xIBS DD



Equilibrium for Core Particles(rms analytic model)

Results compare very well with BetaCool simulations

With equilibrium emittance With fixed emittance

O. Boine-Frankenheim et al.

Electron Cooler:L = 30 mIe = 0.2 Aveff = 2·104 m/sc = 100 m

Target:Pellet Streamdt = 4·1015 cm-2

t = 1 m

1010 particles1010 particles

1011 particles

1011 particles



INTAS Project “Advanced Beam Dynamics for Storage Rings”

Kinetic simulation of cooling dynamics Benchmarking of different models for IBS, cooling

forces and beam-target interaction Analytical and numerical studies of instability

thresholds in the presence of cooling and space charge Impedance library Kinetic simulation studies of accumulation schemes

FZ Jülich, GSI Darmstadt, JINR Dubna, Univ. Kiev, ITEP Moscow, TSL Uppsala



Beam Loss Mechanisms

Hadronic Interaction

Single Target Scattering out of the acceptance

Energy straggling out of the acceptance

Single IBS Scattering (Touschek loss rate)



Hadronic Interaction

totalpptrev

tHloss nf )( 1

1.5 GeV/c 9 GeV/c 15 GeV/c

Relative loss rate / s-1 1.7·10-4 1.2·10-4 1.1·10-4

1/e lifetime 1.6 h 2.3 h 2.5 h

nt = 4·1015 cm-2

frev = 443, 519, 521 kHzσppbar = 100, 57, 51 mbarn

Loss rate: PDG



Single Coulomb Scattering

t

teff

eff

titrev

tCloss

nrZZf i

,

4)( 22

040

2221

,

1.5 GeV/c 9 GeV/c 15 GeV/cRelative Beam Loss Rate / s-1 1.8·10-4 7.3·10-6 2.1·10-6

1/e lifetime / h 1.5 h 38.1 h 132.3 h

εt = 1 mm mradnt = 4·1015 cm-2, Hydrogenfrev = 443, 519, 521 kHz

Rutherford Cross Section

Loss rate:



Energy Loss Straggling

][4.153 20

2

keVxAZZ

t

t

20

20

20

max )/(/212

pepe

e

mmmmm

max

202 1)(

w

Single collision energy loss probability ( energy loss):

Maximum energy transfer:

Scaling quantity (~ mean energy loss):

020 E



Energy Loss Straggling

1.5 GeV/c 9 GeV/c 15 GeV/c

Relative Beam Loss Rate / s-1 3.5·10-4 4.1·10-5 2.8·10-5

1/e Beam life time / h 0.79 6.8 9.9

δeff= -εeff/(β20E0)=10-3

frev = 443, 519, 521 kHz

Loss probability per turn

effeffrevrev

tSloss fdwf

eff

max

max

20

max

1||, ln11)()(

max

Loss rate:



Single IBS: Touschek Loss Rate

Relative Beam Loss Rate / s-1 1.5 GeV/c 9 GeV/c 15 GeV/c

0.01mm mrad 4·10-2 2·10-4 4·10-5

1mm mrad 4·10-5 2·10-7 4·10-8

1/e Beam life time / h 6.9 1390 7000

Loss rate:

Touschek (IBS) lifetime increases with larger emittance

2||

0

1 1)(effC

IBStIBSloss L

DT

Single IBS changes the scattered particle momentum sufficiently that it excides the momentum acceptance of the accelerator

δeff=10-3

1/T0 = frev = 443, 519, 521 kHz



Beam Life Time

tIBSloss

tSloss

tClossHloss

tTotalloss )()()()()( 11111

1.5GeV/c 9 GeV/c 15 GeV/c

Relative Beam Loss Rate / s-1 7.4·10-4 1.7·10-4 1.4·10-4

1/e Beam life time / s ~ 1400 ~ 6000 ~ 7200

11100 10 to10, prevtp nfnnL

L0: initial luminosityτ: beam lifetimetexp: experimental timetprep: beam preparation timenp: number of particlent: target desnityfrev revolution frequency

prepexp

t

tteLL

]1[exp

0



HESR Nominal Cycle



Average Luminosity for HL

for different pbar production rates!



Effects on the Beam

Injection: Losses due to injection oscillation and RF capture

Pre-Cooling: Cooled and hot beams merge

Ramp: Snapback Non-linear part of the rampTune and Chromaticity control

Beam preparation: SqueezeOrbit Control for beam-target overlap

Physics: Beam-Target Interaction, IBS, beam losses



Theoretical “forecast”:N.S.Dikansky, V.V.Parkhomchuk, D.V.Pestrikov, Instability of Bunched Proton Beam interacting with ion “footprint”, Rus. Journ. Of Tech. Physics, v.46 (1976) 2551.

P. Zenkevich, A. Dolinskii and I. Hofmann, Dipole instability of a circulating beam due to the ion cloud in an electron cooling system, NIM A 532 (October 2004).

Effect of Electron Beam

Coherent Dipole Instabilities: In the presence of the electron beam in the cooling section, both longitudinal and transverse instability could take place for the circulating beam due to ion clouds

Tune shift:

2332

0

*

12

ecrrI

Q cpee

01.0 eQ

.

AIe 1

ξ: neutralization factor at lowest momentum

Electron heating



Summary & Outlook

Beam equilibrium is dominated by IBS

heat the beam transversely

Major beam losses are induces by beam-target interaction

sufficient pbar production rate needed at low momenta

Beam effects and losses during cycle

Effect of the electron beam on the circulating beam


intensity limits and beam performances in the h igh- e nergy s torage r ing

Documents

beam performances

beam diameter

presence of cooling

stochastic cooling

cooling forces

nsec production target

pellet target wasa

bending section electrostatic