Status of the BETA-BEAM Task within the EURISOL Design Study

M. Benedikt CARE/BENE CERN 1

Status of the BETA-BEAM Task

within the EURISOL Design

StudyMichael Benedikt

AB Department, CERN

on behalf of the Beta-beam Study Group

http://cern.ch/beta-beam/


Outline

• The Beta-beam study inside EURISOL

• The Beta-beam base line design

• Work progress in the beta beam task

• Conclusions


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).– First stage acceleration (post accelerator ~100 MeV/u).– Radiation protection and safety issues.

• Aims of the Design Study (Feb 2005 – Jan 2009):– Technical Design Report for EURISOL.– Conceptual Design Report for Beta-Beam.


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


The Beta-beam task

• Beta-beam task starts at exit from EURISOL post accelerator and comprises the design of the complete accelerator chain up to the decay ring.

• Conceptual design of an large scale accelerator complex.

• Work is organised in four sub-task:– ST1: Parameters and base line design.

– ST2: Design of low energy rings (RCS + eventually accumulation/cooling ring).

– ST3: Ion acceleration in PS and SPS and design of alternative machines.

– ST4: Decay ring design.

• Participating institutes:– CEA Saclay, CERN, GSI, IN2P3 Orsay, RAL, Stockholm Univ., TRIUMF.


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:

• The status at beginning of the design study (Jan. 2005) was:

– Antineutrino rate (and 6He figures) factor 3 below goal.– Neutrino rate (and 18Ne figures) factor 50 below desired performance.– Excessive incoherent space charge effects at PS injection.

6Helium2+

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

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


ST1: Parameters & baseline design

• Improve base line design (performance, beam physics limitations)

• Provide consistent parameters for complete chain (inj./ej. energies, etc.)

– No modifications on ion production (EURISOL) side (# of targets, etc.), only change is ECR frequency.

– 10 Hz operation of RCS and ECR (100 ms accumulation time in ECR for intensity increase).

– Use of all possible RF buckets in the PS (10 MHz system allows for h=21). 20 buckets filled, one empty for the kicker.

– No bunch merging in PS at top energy at expense of duty factor. – RCS energy range increased from Br = 8 Tm to 11 Tm to decrease

space charge effects at PS injection.– Increased number of injections/merges in decay ring for 18Ne.

Possible due to larger bucket acceptance for 18Ne.


mag

net

cyc

le (

abs

tra

ct)

cycle of 6He

ST1: Base line version2

• DC ion production– 6He, 18Ne

• ECR, Linac and RCS– Cycling at 10 Hertz

• Accumulation in PS– 20 RCS bunches (~2 seconds)

• Acceleration in PS and SPS– top = 100 for both isotopes

• Injection into decay ring– Merging with circulating bunches– Every 6 s for 6He and every 3.6 s for 18Ne

• Present status version2 (after 9 months of the design study):

– 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.


ST2: Design of low energy rings

• 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.


ST2: Design of low energy rings

• 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


ST3: Ion acceleration PS-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



• Power deposition due to beam losses:– PS and SPS comparable for CNGS and Beta-beam operation.– PS exposed to highest power deposition.

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


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


ST4: 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


ST4: 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).


Conclusions

• The Beta-beam design study within EURISOL is advancing well, encouraging results obtained after only 9 months.

• Main efforts will now focus on looking for possibilities to reduce the 18Ne shortfall (together with other EURISOL tasks.

• Going beyond the base line design (at a later stage) with additional accumulation rings, and other new machines (green-field) may open the way to important performance enhancements but efforts are very restricted due to the limited manpower available.

Documents

Status of the BETA-BEAM Task within the EURISOL Design Study