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Collimation of accelerated radioisotopes for beta-beams

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## Collimation of accelerated radioisotopes for beta-beams

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### Collimation of accelerated radioisotopes for beta-beams

P. Delahaye, AB-ATB-EET

FLUKA user meeting 27/11/08

For a boost in an arbitrary direction withvelocity , itisconvenient to decompose the spatial vectorinto components perpendicular and parallel to the velocity : … . Thenonly the component in the direction of is 'warped' by the gamma factor:

wherenow

q1/g

q

Lorentz boost

Generation of nbeams by post-acceleratingradioisotopes- A pure beam of ne to study the nenm oscillation
- A beam of ne, ne from b-decaying nuclides
- A Lorentz boost for a collimated beam (high g)

FP6 baseline scenario

TOP – DOWN APPROACH

6He: 2.9 1018n/year

18Ne: 1.1 1018n/year

6He: 2. 1013 /s

18Ne: 2. 1013/s

A year of exploitation: 107 s

What I won’t talk about…

Converter technology: (J. Nolen, NPA 701 (2002) 312c)

CEA Saclay OptimizedGeometry

9Be(n,a)

T. Stora et al, EURISOL-TN03-25-2006-0003

N Thollieres et al. EURISOL-TN03-25-2006-0004

6He and 18Ne as first candidates (FP6)

Production

- 18Ne
- 2GeV p on 100kW MgOtarget: factor 24 missing
- Lowenergy3He beam on LiFtarget and on 16O gaseoustarget, tests at LLN
- Multiple targets and cooling and accumulating rings

60 cm diametertargetMgO

2MW 3He beam (14.8MeV, 130mA)

101318Ne/s

M. Loiselet and S. Mitrofanov,

LLN

- 18Ne
- 2GeV p on 100kW MgOtarget: factor 24 missing
- Lowenergy3He beam on LiFtarget and on 16O gaseoustarget, tests at LLN

Gas cell

BEAM

Extraction

FP7: novelideasBeam cooling with ionisation losses – C. Rubbia, A Ferrari, Y. Kadi and V. Vlachoudis in NIM A,568(2006) 475

7Li(d,p)8Li

6Li(3He,n)8B

7Li

6Li

IGISOL

ISOL or IGISOL extraction

M. Lindroos et al, NIC-IX proceedings,

P. Delahaye and U. Koester, Nufact08 proceedings

See also: Development of FFAG accelerators and their applications for intense secondary particle production, Y. Mori, NIM A562(2006)591

8Li, 8B: higher Q value

Longer baseline scenario

C. Rubbia arxiv.org/pdf/hep-ph/0609235

Collimation for beta-beams

- Steady –state stackamountsto:
- 8.9 shotsaccumulated for 6He
- 14.0 for 18Ne

Last step:

Symmetricmerging

S. Hancock, ESME simulations

M. Benedikt, S. Hancock, A novel scheme for injection and stacking of radioactive ions at high energy, NIM A 550 (2005) 1–5

S. Hancock et al., Stacking Simulations in the Beta-beam Decay Ring, EPAC 2006

- Stackingmechanism in the decay ring: asymetricbunchmerging

collimation

Arcs

Arc

Arc

Straight section

Arc

Straight section

Momentum collimation50% of 1013/s

75% of 4.3 1012/s

Momentum

collimation

18Ne

6He

Fabich,

EURISOL town

meeting 2007

Straight sections

merging

p-collimation

injection

1.6MW in 0.3s

2.8MW in 0.3s

merging

p-collimation

decay losses

injection

decay losses

Asymetricbunchmerging

- Steady –state stackamountsto:
- 8.9 shotsaccumulated for 6He
- 14.0 for 18Ne

Last step:

Symmetricmerging

S. Hancock, ESME simulations

M. Benedikt, S. Hancock, A novel scheme for injection and stacking of radioactive ions at high energy, NIM A 550 (2005) 1–5

S. Hancock et al., Stacking Simulations in the Beta-beam Decay Ring, EPAC 2006

Momentum collimation

- The collimation durationcanbetunedaccording to the RF program
- Energy distribution of the stack halo wascalculatedwith ESME for 6He and 18Ne

Bunchshorteningwhenraising the second harmonics

6He

Shaving off whend>2.5‰

Recently Fred Jones implemented the bunchshorteningstepinto ACCSIM for 6He startingfrom a longitunal distribution generated by ESME (when second harmonics=0)

ACCSIM calculation

- Longitudinal phase spacebeforebunchshorteningfrom Steve
- Shortened RF program – 12ms instead of typically 300ms (~2 synchrotron periods)

Results

- Placement of the primarycollimator as defined by A. Chancé in the lattice
- Condition (B. Jeanneret et al.)
- Has been verified
- Collimatorelement +-X under ACCSIM has been modified/corrected and validated
- Lossmapswerecreated and adapted for an easy use under FLUKA
- Number of elementwherelost, number of turn, X, Y, Z(S), TX,TY, TZ direction cosinuses and Tk

Cutafterbunchshortening

Total deposited power

From ESME (S. Hancock):

Number of scraped ions increaseslinearlywith time = quite constant power

ACCSIM

18Ne

Avgpower

Oscillations:

Probably non physical!!

Variation +-50% according to average

Similar pattern for 6He

FLUKA simulations

- « Minimal » collimation section
- Straight section + 2ndbump
- Magneticfields, beam pipe and collimators

ACCSIM??

ACCSIM

Placement of the collimators

- Primary and « secondary » collimatorsplacedaccording to the beam enveloppe atd=2.5‰

- In blue:
- Negativeenergies
- Beam enveloppe:
- dmax=-2.5‰
- e=2.6p.mm.mrad
- (100%)

1) Only horizontal collimation

2) Not somucheffect of the secondary if too far awayfrom the beam enveloppe!!

Different sets of conditions

- Thickness of the primarycollimator (10, 20, 30, 50 and 100cm blocks)
- Distance from the beam enveloppe for the secondarycollimators
- Material of the collimators (12C as for LHC, Copper)

Results

- ACCSIM (primarycollimator)
- Primarycollimator on the beam enveloppe as definedabove
- 6He: ~5.6% of the bunchiscollimated
- 18Ne: ~6.0% of the bunchiscollimated

ESME: 6.3%

ESME: 5.4%

Average power 6He

12C collimators, secondaries 1m long at 4mm frombeam enveloppe

6He: 5 1012particleslost/cycle

Average power (W)

1s collimation time (300ms:3X more!!)

Usuallimit

Thicknessprimary (cm)

Average power 18Ne

12C collimators, secondaries 1m long at 4mm frombeam enveloppe

18Ne: 3.4 1012particleslost/cycle

Average power (W)

1s collimation time (300ms:3X more!!)

Usuallimit 10kW

Thicknessprimary (cm)

Energy balance

- Taking 30 cm as the reference case, only 27% (32%) of energyisdissipated in the system (mainlycollimators and beam pipe) for 6He (18Ne)
- In reality the restwillbedumped in the surroundingmaterials, and in the bump

Escapingenergy

3%

6He 30 cm primarycollimator

0.1%

3%

53%

13%

- Mainly6He or 18Ne with
- no interaction
- smallscattering angles

Corrected for in the calculation of the deposited power!!

More collimation and less dump…

- 3 primaries (30cm) instead of 2 secondaries
- 2nd and 3rd Collimators are placed on the beam enveloppe

Average power (W)

18Ne

Lessdeposited power on the 2nd and 3rd collimator!

Due to thicknessmainly

Thicknessprimary (cm)

More collimation and less dump…

- Tryinganothermaterial: 29Cu
- 1 primary 30 cm 2 secondaries 100cm

Primary 112kW!!

Secondaries more efficient!

Conclusions

- A primarycollimator of 30cm willprobably stand the deposited power for 6He and 18Ne
- Efficient collimation on the secondariesimpliesprobably the use of othermaterial (Cu?)
- Absorber materialsafter the primarycollimator
- A detailedstudy of the losses in the surroundingmaterial (magnets in particular!) isabsolutelyneeded
- The lossesat the bumpmightbequitecritical
- Not somany fragments passing the bump (3H: 5‰ per primary6He)

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