iscool: cooled and bunched beams for isolde -...

ISOLDE workshop and users meeting 2006/2007 1/19

ISCOOL: cooled and bunched beams for ISOLDE

E. Mané, 1 P. Delahaye, 2 I. Podadera, 2 M. Lindroos, 2 R. Catherall, 2 T. Giles, 2 H. Franberg, 2 J. Billowes, 1 F. Duval 3 and A. Jokinen 4

1 Schuster Laboratory , University of Manchester, United Kingdom2 CERN, CH-1211 Geneva 23, Switzerland

3 ISMRA, Caen, France4 Department of Physics, University of Jyväskylä, Finland

Presenter: Ernesto ManPresenter: Ernesto Manéé


OutlineOutline

MotivationMotivationScheme of ISCOOLScheme of ISCOOLHow it worksHow it worksOffOff--line tests and resultsline tests and resultsNext stepsNext stepsNew opportunitiesNew opportunitiesSummarySummaryConclusionsConclusions


MotivationMotivation

The The ISISOLDE OLDE coolcooler is a radioer is a radio--frequency quadrupole coolerfrequency quadrupole coolerand buncher (RFQCB) designed to meet those needs.and buncher (RFQCB) designed to meet those needs.

Because it canBecause it can

reduce the beam emittance and energy spread;reduce the beam emittance and energy spread;

control the time structure of the beam.control the time structure of the beam.

Increasing demand for

a better beam quality matching downstream the acceptance of the experiments;

a more efficient use of the HRS beam line;

being able to manipulate radioactive ion beams.


HRS focal pointISOLDE hall

Scheme of ISCOOLScheme of ISCOOL


I. Podadera, CERN-2006-013

mergingswitchyard

ext. quad. triplet valve

diagnostics

exp

bellowinj. quad. triplet

valvediagnostics

HRS

turbopump

support support

injection extraction

bellow

RFQCB

insulators

turbopump

turbopump

trailler/support

60KV

Mainvacuum

Scheme of ISCOOLScheme of ISCOOL

1010--77 mbarmbar 1010--77 mbarmbar


How it works:coolingHow it works:coolingLongitudinal stopping distanceLongitudinal stopping distance

This distance will depend on the:This distance will depend on the:

•• beam energy at the injection (beam energy at the injection (200 eV200 eV););

•• ion massion mass;;

•• buffer gas mass (buffer gas mass (44HeHe););

•• gas pressuregas pressureM. Peterson, Masters Thesis 2002


The RFQ potential is a rotatingThe RFQ potential is a rotating““horse saddlehorse saddle””

Pseudo-potential

x

y

z

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1100

120

140

160

180

200

220

Frequency (MHz)

RF

ampl

itude

zer

o-to

-pea

k (V

)

A=10

A=20

A=50

A=70A=250

amp.amp. freq.freq.

High massHigh mass:

Low massLow mass:

NG-VFO400/200-1200K. Rudolph

Solution:Solution:

I. Podadera, PhD thesis 2006

~

How it works: RFQ confinementHow it works: RFQ confinement

z


How it works: bunchingHow it works: bunching

V

releasetrapped ions

Vtrap

end plate

“kick” modeΔΔtt ΔΔ EE

Normal extNormal ext:

““KickKick”” extext:

z

trap

DC electrodes decoupledDC electrodes decoupled

from the RF field.from the RF field.


OffOff--line testsline tests

They have started in 09/2005 at building 275 in a dedicated They have started in 09/2005 at building 275 in a dedicated test bench.test bench.

They aim at a complete characterisation prior to the installatioThey aim at a complete characterisation prior to the installation of ISCOOL:n of ISCOOL:

Behaviour of vacuum, electronics and high voltage;Behaviour of vacuum, electronics and high voltage;Tests in continuous mode;Tests in continuous mode;Tests in bunched mode.Tests in bunched mode.

E. Mané and P. Delahaye


HV@60KVHV@60KV

TurbopumpsTurbopumps

44He bottleHe bottle

LPC ion sourceLPC ion source

RFRF

Inj quad. tripletInj quad. triplet

Test benchTest benchFaraday cupsFaraday cups(d = 30mm)(d = 30mm)

Li, Na, K, Cs


ResultsResults

Extraction plate (V)

Tran

smis

sion

(%)

energy spreadenergy spread

1.3 eV1.3 eV

133Cs extracted at 30KeV

Transmission in continuous modeTransmission in continuous mode

Energy spread before

reacceleration


ResultsResults

70pA of 133Cs at 30KeVHe flow of 8X10-1 mbar l/s

X% transmission

No cooling, emittance 4No cooling, emittance 4ππ mm.mradmm.mrad Cooled beam, emittance 2Cooled beam, emittance 2ππ mm.mradmm.mrad

10pA of 133Cs at 30KeVNo buffer gas cooling

x% transmission

The The emittanceemittance at the exit of the RFQ is ~ independent of the incoming beam.at the exit of the RFQ is ~ independent of the incoming beam.4 < 20 < 404 < 20 < 40

ISOLDELPC ISCOOL acceptanceWhere is this value from??


Next stepsNext steps

Concerning the offConcerning the off--line commissioning, we shouldline commissioning, we should

•• Finish the tests with the alkalis, in continuous and bunched moFinish the tests with the alkalis, in continuous and bunched modes;des;

•• Extend the tests to other elements with an Extend the tests to other elements with an ISOLDEISOLDE plasma ion source.plasma ion source.


•• RFQ alignment (+RFQ alignment (+-- 1mm)1mm)•• Integration of vacuumIntegration of vacuum•• High voltage platformHigh voltage platform•• High voltage cageHigh voltage cage•• ControlsControls

Richard Catherall

Next stepsNext steps

Position of theodolite for external targets

Position of theodolite for internal targets

High voltage cage

Stefano Marzari

3 targets on the RFQ

3 targets on the inj. quad.

3 targets on the ext. quad.

OnOn--line commissioningline commissioningH. Franberg


Conventional fluorescenceConventional fluorescence--detection methods;detection methods;

Collinear Resonance Ionization Spectroscopy (CRIS).Collinear Resonance Ionization Spectroscopy (CRIS).

New opportunities for laser spectroscopyNew opportunities for laser spectroscopy

Techniques:Techniques:

The cooler also offers a convenient environment for:The cooler also offers a convenient environment for:

performing optical pumping of ions;performing optical pumping of ions;

preparing ions in metastable state;preparing ions in metastable state;

producing polarised or aligned nuclear beams.producing polarised or aligned nuclear beams.

small energy spreadsmall energy spread

small emittance small emittance

bunchingbunching

subsub--Doppler precisionDoppler precision

better beam overlap better beam overlap

single atom sensitivitysingle atom sensitivity

Ref to Jyväskylä

ﾧ


J. Billowes et. al. Laser spectroscopy of gallium isotopes using the ISCOOL RFQ cooler. CERN-INTC-2007-005

Example: Collinear laser technique + bunched ionsExample: Collinear laser technique + bunched ions

Without ISCOOL

With ISCOOL

K. Perarjarvi. 3rd Eurisol Town meeting

K. Flanagan et. al. Laser spectroscopy of radioactive copper isotopes. IS439

accumulation timeconsider space-charge

gate widthisobars

Yield curve for Ga isotopescheck efficiency with bradley

I don’t get the triangle


With ISCOOL at 30 keV and rf at 260 KHz, 480Vp-p, the following preliminary results were accomplished so far for 133Cs :

• Greater than 70% efficiency in continuous mode;• Transverse emittance ~ 2-4 π mm mrad;• Energy spread of 1.3 eV

SummarySummary


• The off-line tests so far suggest that ISCOOL will work as expected;• The best efforts have been put to place it on-line ASAP (September 2007);

ConclusionsConclusions

The use of ISCOOL in conjunction with other techniques will enabThe use of ISCOOL in conjunction with other techniques will enable le

us to further push the limits of the detection of radioactive nuus to further push the limits of the detection of radioactive nuclear clear

beam observables.beam observables.

• And finally


Thank you for your attentionThank you for your attention

iscool: cooled and bunched beams for isolde -...

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