nufact'06, aug. 2006a. fabich, cernradioactive ion beams, 1 radioactive ion beams a. fabich,...

NuFact'06, Aug. 2006 A. Fabich, CERNRadioactive Ion Beams,

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Radioactive Ion Beams

A. Fabich, CERN

on behalf of the Beta-beam Study Grouphttp://cern.ch/beta-beam

NuFact’06, UCIrvine


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Outline

Beta-beam concept

EURISOL DS scenario Layout Main issues on acceleration scheme Physics reach

Other scenarios High-energy Beta-beams Monochromatic beams with electron capture

Summary


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Beta-beam principle

Aim: production of (anti-)neutrino beams from the beta decay of radio-active ions circulating in a storage ring Similar concept to the neutrino factory, but parent particle is a beta-active isotope instead of a muon.

Beta-decay at rest spectrum well known from electron spectrum Reaction energy Q typically of a few MeV

Accelerated parent ion to relativistic max Boosted neutrino energy spectrum: E2Q Forward focusing of neutrinos: 1/

Pure electron (anti-)neutrino beam! NB: Depending on +- or --decay we get a neutrino or anti-neutrino Two (or more) different parent ions for neutrino and anti-neutrino beams

Physics applications of a beta-beam Primarily neutrino oscillation physics and CP-violation Cross-sections of neutrino-nucleus interaction

=100


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Production chain

-factory uses beam of 4th generation. Beta-beam uses 3rd generation beam. Beta-beam is technically closer to existing/used accelerator technology.

.

protontarget

+ ...

+ (super-beam)

e+ + e

and charge conjugated

-factory

beta-beam protontarget

isotope

isotope* +e+ e

Ion source Acceleration Storage Neutrino beam


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+ or -

Choice of ion species Beta-active isotopes

Distance from stability Production rates Life time

Reasonable lifetime at rest If too short: decay during acceleration If too long: low neutrino production Optimum life time given by acceleration scenario and neutrino rate optimization In the order of a second

Low Z preferred Minimize ratio of accelerated mass/charges per neutrino produced One ion produces one neutrino. Reduce space charge problems

NuBase

t1/2 at rest (ground state)

1 – 60 s1ms – 1s

EURISOL DS


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Baseline and detectorNeutrino physics similar as in -factory, but at different -energies.

Baseline distance: Relativistic gamma in the range of 100 – 400 Q-value of MeV E in the range of GeV Baselines in the range of 100-1500 km

Only one detector one baseline

Location available for detector underground area? E.g. Fermilab-Soudan 730 km

Suitable for 6He=350.

Detector technology No magnetized detector necessary Water Cherenkov is the standard choice.

Technically considerable in the Megaton class Energy resolution of ~250 MeV

LAr as an alternative choice. Higher resolution (~50 MeV) Technological challenge CERN-Frejus: 130 km


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Guideline to -beam scenarios

based on radio-active ions Low-energy beta-beam: relativistic < 20 Physics case: neutrino scattering

Medium energy beta-beam: 100 E.g. EURISOL DS Today the only detailed study of a beta-beam accelerator complex

High energy beta-beam: >350 Take advantage of increased interaction cross-section of neutrinos

Monochromatic neutrino-beam Take advantage of electron-capture process

Accelerator physicists together with neutrino physicists defined the accelerator case of =100/100 to be studied first (EURISOL DS).


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The EURISOL scenario Based on CERN boundaries Ion choice: 6He and 18Ne

Relativistic gamma=100/100 SPS allows maximum of 150 (6He) or 250 (18Ne) Gamma choice optimized for physics reach

Based on existing technology and machines Ion production through ISOL technique Post acceleration: ECR, linac Rapid cycling synchrotron Use of existing machines: PS and SPS

Achieve an annual neutrino rate of either 2.9*1018 anti-neutrinos from 6He Or 1.1 1018 neutrinos from 18Ne

Once we have thoroughly studied the EURISOL scenario, we can “easily” extrapolate to other cases. EURISOL study could serve as a reference.

EURISOL scenario


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Ion production – ISOL method6He production

converter technology using spallation neutrons

Nominal production rate 5*1013 ions/s can be achieved.

18Ne production Spallation of close-by target

nuclides 18Ne from MgO: 24Mg12 (p, p3 n4) 18Ne10

Direct target: the beam hits directly the oxide target

Required production rate of 5*1013 ions/s

(for 200 kW dc, few GeV proton beam) Estimated production rate more than

one order of magnitude too low! Novel production scenarios required.


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EURISOL design

Low-energy accumulation Optional scenario to overcome short-fall in production rate

Target operated in DC mode Not 100% of production is used

Dead time during acceleration Simultaneous accumulation in low-energy ring

Design of a low-energy accumulation ring dedicated for isotope accumulation.

Possible solution. Yet not all technical issues addressed and solved.


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Production with re-circulating ions

Production of unstable isotopes: Primary ions circulate in the beam

until they undergo nuclear processes in the thin target foil.

Injection Permanent accumulation of

primary ions: Single ionized ions are fully stripped by a thin foil.

Compensating ionization losses: Acceleration at each turn by an

adequate RF-cavity

Ion channel: E.g.: 7Li + D 8Li + p

8Li: t1/2~0.8 s, <E>~6.7MeV Rate: > 1014 ions/s

C. Rubbia et al. (see talk this week)


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Use of existing accelerators

Use of CERN PS and SPS

Difficulties Not designed for high intensity operation of radioactive ions

No collimation, non-baked vacuum system, ... Slow cycling Allows no optimization on machine design

Large ion loss Considerable activation Vacuum degradation Space charge

Advantages Possible cost reduction Maximize use of well-known machines


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Intensity evolution during acceleration

Cycle optimized for neutrino rate towards the detector

30% of first 6He bunch injected are reaching decay ring Overall only 50% (6He) and 80% (18Ne) reach decay ring

Normalization Single bunch intensity to maximum/bunch Total intensity to total number accumulated in RCS

Bunch20th

15th

10th

5th1st

total


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Power losses - Activation

Nucleon losses compared PS and SPS comparable for CNGS and bb operation PS exposed to highest power losses

Ploss/l [ions] Beta-beam

CNGS 6He 18Ne

RCS - 0.17 0.14

PS 3.3 2.2 2.8

SPS 0.25 0.4 0.25

Power loss per unit circumference of a machine

machinecycle

lossloss ncecircumferet

cycleElP

*

//


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Dynamic vacuum Decay losses cause degradation of the vacuum

due to desorption from the vacuum chamber

The current study includes the PS, which does not have an optimized lattice for unstable ion transport and has no collimation system The dynamic vacuum degrades to 3*10-8 Pa

in steady state (6He)

An optimized lattice with collimation system would improve the situation by more than an order of magnitude.

1.00E+08

1.00E+09

1.00E+10

0 5 10 15 20 25 30 35

s [m]

6L

i lo

ss

es

[/0

.1m

/6s

-cy

cle

]

P. Spiller et al., GSI

C. Omet et al., GSI


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Decay ring

Geometrical considerations Maximize straight section Shortest arcs possible

High magnetic field SC magnets

For EURISOL scenario (=100) Circumference: 6900 m Length of straight section: 2500m Ratio straight section/circumference = 0.36

Geometric sizing for other gamma ranges just by linear scaling ratio always about 36%;

Neutrino rate:

-5

0

5

10

15

20

0 1000 2000 3000

1/2 (m) x1/2

y1/2

Dx

x = 18.23

y = 10.16

cycletionstraightcyclesps

tt

merges

tfmergesIeRcycle

/**1 sec/

)2ln(

2/1

A. Chance et al., CEA Saclay


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Stacking process

1) Injection

2) Rotation

3a) Single merge

3b) Repeated merging

Longitudinal merging Mandatory for success of the Beta-beam concept Lifetime of ions (minutes) is much longer than cycle time

(seconds) of a beta-beam complex

1. Injection: off-momentum

2. Rotation

3. Merging: “oldest” particles pushed outside longitudinal acceptance momentum collimation


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~1 MJ beam energy/cycle injected equivalent ion number to be removed

~25 W/m average

Momentum collimation: ~5*1012 6He ions to be collimated per cycle Decay: ~5*1012 6Li ions to be removed per cycle per meter

p-collimation

me

rgin

g

decay losses

inje

ctio

n

Particle turnover

Straight section

Straight section

Arc

Arc

Momentum

collimation

LHC project report 773

bb


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Collimation and absorption Merging:

increases longitudinal emittance Ions pushed outside longitudinal acceptance

momentum collimationin straight section

Decay product Daughter ion occurring continuously along decay

ring To be avoided:

magnet quenching: reduce particle deposition (average 10 W/m)

Uncontrolled activation

Arcs: Lattice optimized for absorber system OR open mid-plane dipoles

Straight section:

Ion extraction et each end

s (m)

s (m)

De

po

site

d P

ow

er

(W/m

)

x

Opt

ical

fun

ctio

ns (

m) primary

collimatory

A. Chance et al., CEA Saclay


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Physics reach

EURISOL scenario =100 each 6He and 18Ne with a 5-year run 2.9*1018 6He decays/year or 1.1*1018 6Ne decays/year

Physics reach Sensitivity on 13 down to ~1o

Sin2(2 13)

CP [

de

g]


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Towards high-energy beta-beams

Beta-beam operation at higher relativistic reduces the annual rate R due to

Extended acceleration time

Simple analytical approximation

Boosted life time

Average neutrino rate R at decay ring

at fixed ion rates from production.

Physics reach on neutrino beam side: PR R

rationhighAccele

rationhighAccele

onaccumulati

accum

ationLowAcceler

rationlowEaccele

t

tt

t

t

t

producedion

gammatopion eN

N )(

2/

)(

)2log(

_

_ 2/1

cycle

tionstraightgammatopiont

tN

t

fNeRate top

cyclemerges

sec_

)2log(

2/11

/s]

R 1/


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Using existing HE hadron machines

Tevatron most realistic scenario Comparable fast acceleration in all energy regimes top=350

About 70% survival probability for 6He Compare with 45% in the EURISOL DS

(2 seconds accumulation time considered) Reduced decay losses and activation during acceleration

Several studies on the physics reach exist, but annual neutrino rates have to be reviewed.

Machine tramp (including injector chain) [s] max(proton) max (6He2+) max (18Ne10+)

Tevatron 18 1045 349 581

RHIC 101 (41) 268 89 149

LHC ~1200 7600 2500 3500


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-Spectra Wide spectra from super- and Beta-beams

Requires energy reconstruction in detectors

“solution”: EC monochromatic beam Electron capture:

p++e- n+ Sharp energy spectrum of the neutrino beam

D.A. Harris, FERMILAB-Conf-03/328-E


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Monochromatic -beam

Disentangle measurement of 13 and CP running at two different

Ion species: 150Dysprosium Physics reach for 1018 neutrinos/year at DR, each 5-year run at two different

Decay t1/2 BR EC/+ E [MeV] E[MeV]

148Dy148Tb 3.1m 1 0.96 2.1

150Dy150Tb 7.2m 0.64 1 1.4

152Tm152Er 8.0s 1 0.45 4.4 0.52

150Tm1508Dy 72s 1 0.77 3.0 0.4

13 [deg]

CP [

de

g]


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Special aspects of a EC -beam Requires acceleration of partly stripped ions

Vacuum lifetime comparable to half-life Particle losses due to charge state change negligible

Most promising candidate: 150Dysprosium

Main characteristics: Heavy and exotic isotope Long lifetime

Production required: >1015 150Dy atoms/second Production achievable: 1011 150Dy atoms/second

50 microAmps primary proton beam with existing technology (TRIUMF)

Acceleration demanding Balance for charge state between high magnetic rigidity and space charge

Decay t1/2 BR EC/+ E [MeV] E[MeV]

150Dy150Tb 7.2m 0.64 1 1.4


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For >1O a Beta-beam scenario is useful. Improved situation in combination with

Super-beam Simultaneous analysis of atmospheric neutrinos

Physics reach in comparison


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Summary

Beta-beam accelerator complex is a very high technical challenge due to high ion intensities

Activation Space charge

So far it looks technically feasible.

The physics reach for technically achievable scenarios is competitive for >1O. Usefulness depends on the short/mid-term findings by other neutrino search

facilities.

Acknowledgment of the input given by M. Benedikt, A. Jansson, M. Lindroos, M. Mezzetto, beta-beam task group and related EURISOL tasks

nufact'06, aug. 2006a. fabich, cernradioactive ion beams, 1 radioactive ion beams a. fabich,...

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