Beta-beam Accelerator requirements

M. Benedikt PAF / CERN 1

Beta-beam Accelerator

requirements


Outline

• The Beta-beam study inside EURISOL

• The Beta-beam base line design

• Work progress on accelerator design

• Summary


Eurisol DS + Beta-beam

• The EURISOL Project– Design of an ISOL type (nuclear physics) facility.– Performance three orders of magnitude above existing facilities.– A first feasibility / conceptual design study was done within FP5.

• Strong synergies with the low-energy part of the beta-beam led to integration of beta-beam design study into EURISOL:– Ion production (proton driver, high power targets).– Beam preparation (cleaning, ionization, bunching).– Radiation protection and safety issues. – First stage acceleration (post accelerator ~100 MeV/u).

• Accelerators studied in other EURISOL Tasks– Proton Driver for ion production.– Post-Accelerator for “pre-acceleration” of radioactive ions.


Beta-beam baseline design

Neutrino

Source

Decay Ring

Ion production

ISOL target & Ion source

Proton Driver SPL

Decay ring

B = 1500 Tm B = ~5 T C = ~7000 m Lss= ~2500 m

6He: = 100 18Ne: = 100

SPS

Acceleration to medium

energy RCS

PS

Acceleration to final energy

PS & SPS

Beam to experiment

Ion acceleration

Linac

Beam preparation ECR

pulsed

Ion production Acceleration Neutrino source

Low-energy part

High-energy part


From dc to very short bunches

1.9s

2 s

tB 1.9 s

t

B

PS

SPS

2 s

tB 1.9 s

PS

t

2 s to decay ring(20 bunches of <5 ns)

PS: 1.9 s flat bottom with 20 injections. Acceleration in 0.8 s to top energy.

Target: dc production during 1.9 s.

60 GHz ECR: accumulation for 0.1 s.Ejection of fully stripped ~20 s pulse. 20 batches during 1.9 s.

RCS: further bunching to ~100 ns. Acceleration to ~500 MeV/u. 10 Hz repetition rate.

SPS: injection of 20 bunches from PS. Acceleration to decay ring energy and ejection. Repetition time 6 s (6He).

1.9s 4.1s

Post accelerator linac: acceleration to ~100 MeV/u. 20 repetitions during 1.9 s.

t


Goals vs. starting conditions

• For the base line design, the aims are (J. Bouchez et al., NuFact’03):

– An annual rate of 2.9 1018 anti-neutrinos (6He) along one straight section– An annual rate of 1.1 1018 neutrinos (18Ne) at =100

– always for a “normalized” year of 107 seconds.

• The corresponding target values for ions in the decay ring are:

• Present status after 10 months design study (Feb. 2005) :

– Antineutrino rate (and 6He figures) have reached the design values but no safety margin is yet provided.

– Neutrino rate (and 18Ne figures) still a factor 20 below desired performance. Achieved improvement factor 2.5. Next step: analyze production side.

6Helium2+

– Intensity (av.): 1.0x1014 ions – Rel. gamma: 100

18Neon10+ (single target)– Intensity (av.): 7.2x1013 ions – Rel. gamma: 100


RCS for the beta-beam

• Comparison Beta-beam RCS (100 MeV/u injection to 11 Tm) to to other machines:

– Dipole field requirements• Beta-beam RCS Bmin=0.24 T Bmax=1.0 T• ISIS(50 Hz, 800 MeV p) Bmin=0.18 T Bmax=0.7 T• AUSTRON(25/50 Hz, 1.6 GeV p) Bmin=0.20 T

Bmax=0.94 T• JPARC(25Hz, 3 GeV protons) Bmin=0.25 T Bmax=1.01 T

– Accelerating voltage and RF frequency• Beta-beam RCS 10 Hz, V=100 kV, h=1, FRF ~ 0.64 to 1.24 MHz for He

FRF ~ 0.64 to 1.45 MHz for Ne

• ISIS 50 Hz, V=140 kV, h=2, FRF=1.34 to 3.1 MHz, • J-Parc RCS 25 Hz, V=450 kV, h=2, FRF=1.23 to 1.67 MHz, • AUSTRON 25/50Hz, V=250 kV, h=2, FRF=1.34 to 2.62 MHz

• Parameters are very similar to other RCS machines.


RCS for the beta-beam

• Analysis of candidate lattices for RCS:– FODO lattices (JParc) have the advantage of relatively low

quadrupole gradient, regular optical functions and easy chromaticity correction.

– Doublet / triplet lattices (ISIS, Austron) provide longer uninterrupted drift space for injection, extraction, RF cavities and collimation system.

– Dispersion suppressed in straight sections to avoid synchro-betatron coupling.

J-Parc layout • The Beta-beam RCS magnet and RF parameters are well inside typical RCS specifications and do not pose critical technical issues.

• Next step: lattice choice/optics design.

A. Tkatchenko


Ion acceleration in PS and SPS

• Analysis of beam losses:

– Relative decay distribution similar for both isotopes– ~90% of all decays (before injection to decay ring) occur in the PS,

conenctrated at low energy (accumulation over 2 s).

A. Fabich


Ion acceleration PS and SPS

• Power deposition due to beam losses:– PS and SPS comparable for CNGS and Beta-beam operation.– Different loss mechanisms – different machine parts concerned.– PS exposed to highest power deposition.– No “operation” losses yet considered for the beta-beam.

cyclet

nucleonloss dttT

dt

dIcycleE )(/

machinecycle

lossloss ncecircumferet

cycleElP

*

//

Energy loss/cycle

Power loss

• Comparison of beam losses Beta-beam - CNGS


pressure evolution in the PS V7

1E-10

1E-09

1E-08

1E-07

0 0.5 1 1.5 2 2.5 3 3.5

t / s

av

era

ge

pre

ss

ure

/ P

a

He

Ne

Ion acceleration PS and SPS

loss distribution in the PS

1E+03

1E+04

1E+05

0 5 10 15 20 25 30

S / m

be

am

lo

ss

es

/ a

.u.

HeNe

loss distribution in the PS V7

1E+02

1E+03

1E+04

1E+05

0 10 20 30 40 50

S / m

be

am

lo

ss

es

/ a

.u.

He

Ne

pressure evolution in the PS

1E-07

1E-06

1E-05

1E-04

0 0,5 1 1,5 2 2,5 3 3,5

t / s

av

era

ge

pre

ss

ure

/ P

a

He

Ne

PS

New“PS”

Pressure evolution due to desorption

Bottom-up

• Loss distribution / dynamic vacuum effects / new PS:

Loss distribution along machine period

– Losses quasi equally distributed in PS, no place for collimation.– Optimized doublet lattice allows separation of decay products and collimation.

P. Spiller


Beta-beam decay ring design

• Detailed studies and simulation of asymmetric merging (accumulation).– The neutrino beam at the experiment has the “time stamp” of the

circulating beam and must be concentrated in as few and as short bunches as possible to maximize the peak number of ions/nanosecond (background suppression).

– Aim for a duty factor of below 10-2.

– Full scale simulation of longitudinal bunch merging.

S. Hancock


Beta-beam decay ring design

– Off-momentum injection on matched dipsersion orbit.

– Needed for asymmetric merging distance between injected and stored bunches 25 ns.

– Avoids very fast elements.

– Has to be paid by additional aperture in the arcs, injection region.

• Next steps:– Collimation strategy and design.– SC magnets, RF system.

Injected beam

Stored beam

-0,06

-0,04

-0,02

0

0,02

0,04

0,06

0,08

0,1

0,12

500 550 600 650

Beam sizes (m) Horizontal

Vertical

s (m)

-0,06

-0,04

-0,02

0

0,02

0,04

0,06

0,08

500 550 600 650

Horizontal

Vertical

Beam sizes (m)

s (m)

• Lattice design and injection region optimisation

A. Chance


Other activities

• Feasibility and performance improvement with additional low-energy accumulation/cooling ring.

• Tracking and beam loss studies for complete chain.

• Improvement possibilities for 18Ne (collaboration with other EURISOL tasks)– Production rate of 18Ne (multiple targets?)

– Charge state distribution after ECR source.

• Analysis of 19Ne as alternative to 18Ne (higher production rate, longer lifetime).


Summary - Accelerators

• Proton driver linac– few 100 kW protons – 1 to few GeV beam energy– DC beam preferred– Studied in EURISOL driver task

• Post accelerator linac– 100 MeV/u energy – 10 Hz pulsed, 20-50 s pulse length– Studied within EURISOL driver/post-accelerator tasks

• RCS– 100 MeV/u to 11 Tm (290 MeV to 2.5 GeV proton equivalent).– 10 Hz (for beta-beam)– Potential interest of option with 20 (50) Hz for protons in parallel.– Studied within EURISOL BETA-BEAM TASK.


Summary - Accelerators

• PS– Accumulation of 20 bunches (1.9s) on flat bottom– Acceleration to top energy– Beam losses and dynamic vacuum effects critical.– Studied within EURISOL BETA-BEAM TASK.

• New PS– Similar or enlarged working range. – Special lattice design for high efficiency collimation system.– Need to study slow vs. 10 Hz option (beam losses at flat bottom).– Studied within EURISOL BETA-BEAM TASK.

• SPS– Acceleration to gamma 100 for both ions– Beam losses similar to CNGS but distributed (less critical than PS)– Studied within EURISOL BETA-BEAM TASK.

• Decay ring– Accumulation and storage of 20 ion bunches.– Special injection/merging scheme with dedicated lattice design.– Studied within EURISOL BETA-BEAM TASK.

Documents

Beta-beam Accelerator requirements