M. Lindroos NUFACT06 School

A low energy accumulation ring for the beta-beam

Ansgar Simonson, Anders Kaellberg, Mats Lindroos

M. Lindroos NUFACT06 School

Outline

• General concepts: LEIR and HESR• Application to a beta-beam• First results for 18Ne

M. Lindroos NUFACT06 School

The EURISOL beta-beam facility!

M. Lindroos NUFACT06 School

Production

• Major challenge for 18Ne• Workshop at LLN for production,

ionization and bunching this year• New production method proposed by

C.Rubbia and Y.Mori• Accumulation ring?

M. Lindroos NUFACT06 School

The slow cycling time.What can we do?

Production

PS

SPS

Decay ring

Ramp time PS

Time (s)0 8

Wasted time?

Ramp time SPS

Reset time SPS

M. Lindroos NUFACT06 School

Production and accumulation

PS

SPS

Decay ring

Ramp time PS

Time (s)0 2.4

Ramp time SPS

Reset time

4.8 7.2

M. Lindroos NUFACT06 School

Accumulation at 400 MeV/u

2 4 6 8 10

Accumulationtime

21018

41018

61018

81018

11019

1.2 1019

Annualrate 6HeT1/2=1.67 s

T1/2=17 s

T1/2=0.67 s

M. Lindroos NUFACT06 School

Stacking

0.2 0.4 0.6 0.8 1

25000

50000

75000

100000

125000

150000

Multiturn injection with electron cooling

Half life [s] 0.1 1 10Tvacuum [s] 30 30 30Intensity ions [every 100 ms in 30 microsceonds] 104 5 105 5 105

Tcool[ms] 100 100 100Number of turns 10 10 10Final emittance [micrometer] 0.1 0.1 0.1Final number of particles in stack 3 104 3 107 3 108

2 4 6 8 10 12

Time [s]

0

2

4

6

8

Beam

Inte

nsity [

E8 ions]

beam lifetime : 6.5s

Linac III rep rate : 2.5 HzIon beam energy : 4.2 MeV/uElectron energy : 2.35 keVElectron current : 105 mA

Average accumulated intensity : 6E8 ionsPeak intensity : 7.1E8 ions

M. Lindroos NUFACT06 School

Electron Cooling before the RCS

• Can the beams be cooled transversely in 0.1 s?

• Ansgar Simonsson, Anders Kallberg

• 22 May 2006

M. Lindroos NUFACT06 School

Scenario20 cycles during 2 s, then 5 s pause

10 Hz linac cooler ring RCS PS 100 MeV/u 100 MeV/u 300 MeV/u

Accumulation Several linac buches are merged in the cooler

ring with electron cooling for every bunch sent to the RCS

M. Lindroos NUFACT06 School

• A 430 m cooler ring from FAIR

• one 30 m long electron cooler

• one section for injection and extraction

The RCS is 208 m, the cooler ring can be e.g. 104 m or 208 m.

M. Lindroos NUFACT06 School

Electron cooling

fast for cold ions, slower when electron and ion velocities differ

not dependent on ion current

much faster longitudinally than transversely

1/cooling time ~ q2/A×Ie/Θ3, where Θ is the angle between ions and electrons

M. Lindroos NUFACT06 School

Emittance

Intensity

Before cooling

After cooling

M. Lindroos NUFACT06 School

Electron cooler

the cooling section is one to several meters long

up to 2.5 A electron current

55 kV for 100 MeV/u

large -functions give fast cooling, 1/cooling time ~ 1/Θ3 ~ 1.5

M. Lindroos NUFACT06 School

Simulations of transverse cooling

input: hollow ion beams so all ions have the same transverse emittance

simple tracking with 3 D cooling force and electron beam space charge

intrabeam scattering isn’t included, so the results for the coldest ions are wrong

M. Lindroos NUFACT06 School

M. Lindroos NUFACT06 School

18Ne10+ 0.1 s cooling 10% electron cooler2.5 A electron currentx = 16 mx = 100 p mm mrad

PS limit 16 mm / 7 mm

M. Lindroos NUFACT06 School

6He2+ vs 18Ne10+

1/cooling time ~ q2/A (theory) or1/cooling time ~ q1.7/A (CRYRING

measurements)

18Ne10+ / 6He2+= 5 - 8, cooling of neon is much faster

Space charge tune shiftQ = -0.022 / -0.14

M. Lindroos NUFACT06 School

6He2+ 0.1 s cooling 10% electron cooler1 A electron currentx = 16 mx = 100 pi mm mrad

M. Lindroos NUFACT06 School

Conclusions

• A cooling ring with multiturn injection before the RCS can dramatically reduce the horizontal emittance of 18Ne10+ with 0.1 s cooling.

• The 6He2+ case is much more difficult, since the cooling time is longer and the space charge tune shift larger.

• A factor of 4 of the “missing” 18Ne in the decay ring can be recovered using this technique