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Collimation of accelerated radioisotopes for beta-beams . P. Delahaye, AB-ATB-EET FLUKA user meeting 27/11/08.

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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 inlet**Gas cell BEAM Extraction FP7: novelideas Beam 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**Momentum**collimation Arcs Arc Arc Straight section Arc Straight section Momentum collimation 50% 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)**ACCSIM calculation**• Repeated for 18Ne « Taking care that the longitdunal emittance doesn’t filament »**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)**Lossmap for a typicalset-up**• 6He GeV/pr/cm3 GeV/pr/cm3 Primarycollimator 30cm**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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