Machine parameters and limitations in the EURISOL beta-beam baseline

A.FabichAB department, CERN

On behalf of theBeta-beam study group

http://cern.ch/beta-beam

BENE week, Nov. 2005

A.Fabich, CERN

Beta-beam baseline:

Parameters & Limits, 2

Outline

Conceptual Design study Beta-beam baseline design Machine parameters Ion intensities

Limitations Production Decay losses Acceptance Tune shift

Conclusions

BENE week, Nov. 2005

A.Fabich, CERN

Beta-beam baseline:

Parameters & Limits, 3

Conceptual design study EURISOL Design Study

Within the 6th framework program of EU Conceptual Design Report for Beta-Beam

The baseline scenario is based on ISOL technique at CERN: usage of PS and SPS machines

The Beta-beam Design Study is aiming for: A beta-beam facility that will run for a “normalized” year of 107 s Providing an annual rate of

2.9*1018 anti-neutrinos (from 6He at =100) 1.1*1018 neutrinos (from 18Ne at =100)

BENE week, Nov. 2005

A.Fabich, CERN

Beta-beam baseline:

Parameters & Limits, 4

Beta-beam baseline design

Neutrino

Source

Decay Ring

Ion production

ISOL target & Ion source

Proton Driver

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

BENE week, Nov. 2005

A.Fabich, CERN

Beta-beam baseline:

Parameters & Limits, 5

mag

net

cyc

le (

abs

tra

ct)

cycle of 6He

Machine cycle

Baseline version:

Production 6He, 18Ne

ECR, Linac and RCS Cycling at 10 Hertz

Accumulation in the PS Accumulation of 20 RCS bunches (~2 seconds)

Acceleration through PS and SPS as fast as possible 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

BENE week, Nov. 2005

A.Fabich, CERN

Beta-beam baseline:

Parameters & Limits, 6

For the design goal of2.9*1018 antineutrinos/year1.1*1018 neutrinos/year

Required isotope intensities: Baseline version

Typical intensities of 108-109 ions for LHC injector operation (PS and SPS)

Ion intensities

6He 18Ne

Decay ring [ions stored] 9.7*1013 7.5*1013

SPS ej [ions/cycle] 9. 0*1012 4.3*1012

PS ej [ions/cycle] 9.5*1012 4.3*1012

Source rate [ions/s] 2*1013 2*1013

Top-dow

n

BENE week, Nov. 2005

A.Fabich, CERN

Beta-beam baseline:

Parameters & Limits, 7

Limitations

Isotope production

The self-imposed requirement to re-use a maximum of existing CERN

infrastructure

Cycling time, aperture limitations, collimation systems etc.

The high intensity ion bunches in the accelerator chain and decay ring

Space charge

Decay losses

BENE week, Nov. 2005

A.Fabich, CERN

Beta-beam baseline:

Parameters & Limits, 8

Ion production 6He figures have reached the design values but no safety margin is

yet provided.

18Ne figures are more than one order of magnitude below the desired performance. Missing factor (~25) for 18Ne production Within baseline:

Improvement of isotope production/preparation Possibly include an accumulation scenario at low energy

19Ne no immediate solution (for baseline scenario) Production rate much higher, but life time 10 times higher Acceleration of an order of magnitude more ions

Excluded by space charge limits in the PS and SPS

BENE week, Nov. 2005

A.Fabich, CERN

Beta-beam baseline:

Parameters & Limits, 9

Decay distribution

70% of first 6He bunch are lost before 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

BENE week, Nov. 2005

A.Fabich, CERN

Beta-beam baseline:

Parameters & Limits, 10

Decay losses (1)

Relative decay distribution similar for both isotopes

~90% of all decays before entering decay ring occur in the PS

Can be translated into power losses and compared with “existing” high intensity operation

…

BENE week, Nov. 2005

A.Fabich, CERN

Beta-beam baseline:

Parameters & Limits, 11

In the PS most losses occur at low energy accumulation PS: (6He) [1.5 ; 9.3], (18Ne) [2.2 ; 15.5]

1st

20th

Decay losses (2)

1st

20th

BENE week, Nov. 2005

A.Fabich, CERN

Beta-beam baseline:

Parameters & Limits, 12

Power losses

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

cyclet

nucleonloss dttT

dt

dIcycleE )(/

machinecycle

lossloss ncecircumferet

cycleElP

*

//

Energy loss/cycle

Power loss

BENE week, Nov. 2005

A.Fabich, CERN

Beta-beam baseline:

Parameters & Limits, 13

H,V [µm] 6He 18Ne Cf., Acceptance

RCS inj 16.4, 8.8 16.4, 8.8 ?

PS inj 6.6, 3.5 4.0, 2.1 60, 20

SPS inj 0.8, 0.4 0.5, 0.3 28, 4.5

Scaling from normalized rms values of 7.8µm (H) and 4.2µm (V) for 11Tm 6He ions at PS injection, then

),(

),(*),(

machineion

PSinjrefmachineion

We assume the 18Ne has the same normalized emittance as the 6He because it comes from the Linac with identical βγ and is multi-turn injected into the RCS with the same geometrical set-up.

S.Hancock1σ Physical Emittance

BENE week, Nov. 2005

A.Fabich, CERN

Beta-beam baseline:

Parameters & Limits, 14

Max 6He ions Max 18Ne ions Max |QV|inj

RCS ej (1 bunch) 7×1012 0.8×1012 0.5 (?)

PS ej (20 bunches) 7×1012 3×1012 0.3

SPS ej (20 bunches) 6×1012 3×1012 0.2

Considering for simplicity a round Gaussian beam of fully stripped ions, the self-field incoherent (“Laslett”) tune shift is

V

b

b

p

pV

NR

c

r

A

ZQ

3

2

4

3

We assume τb = 80% of the rf bucket duration in all cases.

This allows upper limits on the total number of ions per shot to be estimated (taking into account unequal bunches) based on known limits at injection.

S.HancockLimits due to Tune Shift

BENE week, Nov. 2005

A.Fabich, CERN

Beta-beam baseline:

Parameters & Limits, 15

Solve tune shift limit

1. Two batches from the PS instead of one.

2. One could also imagine deliberately blowing up the emittance to improve the situation in the downstream machine.

6He 18Ne

required QV,inj limit required QV,inj limit

RCS ej (1 bunch) 0.63×1012 7×1012 0.16×1012 0.8×1012

PS ej (20 bunches) 6.7×1012 7×1012 2.6×1012 3×1012

SPS ej (40 bunches) 11×1012 10×1012 4.9×1012 5×1012

S.Hancock

BENE week, Nov. 2005

A.Fabich, CERN

Beta-beam baseline:

Parameters & Limits, 16

Conclusions

Baseline parameters fixed Study goes now into detail of different machines and aspects

Average power losses are comparable to CNGS case (which is accepted) PS has to stand the most demanding losses Power losses < 3 W/m

Limits set by space charge in both the PS and SPS machines.

Main efforts will now focus on 18Ne shortfall.