Off-line Tests and first On-Line Installation Off-line Tests and first On-Line Installation

of the Laser Ion Source Trap LISTof the Laser Ion Source Trap LIST

--

Application for Test of CVC and CKM Unitarity Application for Test of CVC and CKM UnitarityF. Schwellnus1, T. Gottwald1, C. Mattolat1, V. Sonnenschein1, K. Wendt1,

R. Catherall2, B. Marsh2, F. Österdahl3, V. Fedosseev2,

K. Blaum1,4, H.-J. Kluge4, S. Schwarz5

1 Institut für Physik, Johannes Gutenberg Universität Mainz

2 CERN Physics Department

3 Department of Physics, Royal Institute of Technology, Stockholm

4 Gesellschaft für Schwerionenforschung, Darmstadt

5 NSCL, Michigan State University, East Lansing

Proposal to the INTC, 21. May 2007

INTC Meeting 21.05. – 22.05.2007

OverviewOverview

• The idea:

Development of an ion source which combines very high selectivity with

excellent control over the ion beam properties.

• The basis:

The successfull joint material and laser tests for RILIS

at the off-line separator in Jan. 2007

• The method:

Combination of the advantages of a laser ion source with those

of a radio frequency quadrupole cooler and buncher.

• The physics case:

Test of CKM unitarity and constant vector current hypothesis CVC by mass

measurements on 62Ga and 62Zn using ISOLTRAP

• The proposal:

Request for off-line and on-line beam time on 62Ga & 62Zn at ISOLDE in 2008

INTC Meeting 21.05. – 22.05.2007

Motivation for RILIS & LIST

1. Atomic Beam Source

3. Mass Separator 4. Laser System

Proton Beam

Ion Repeller

to Experiments

Laser- Beams

HV Platform

ISOLDE RILIS

Source

IonBeam

Ti:Sa 1

Ti:Sa 2

Ti:Sa 3

Nd:YAG

Laser System

Mass Separator

with Surface Ion Reppeler

Gas filledRFQ Trap

2. Gas filled RFQ Trap Section for Bunching and Cooling

Production of isobarically pure ion beams with optimum spatial and

temporal ion pulse control using a gas-filled RFQ structure

INTC Meeting 21.05. – 22.05.2007

Principle of the LISTPrinciple of the LIST

Electron Repeller

Ion Repeller

Z

Release

10 mmEnd Plate

SIMION 7.0: simulation of the potential distribution

Laser IonsSurface Ions

UDC

Atomizer

Electrons

Laser BeamsAtoms Ions

SwitchableElectrodes

RFQ SegmentsRFQRFQ SegmentsSegments

Accumulate

Helium Buffer Gas ~ 10-3 mbar

Laser Ionization

Electron Repeller

Ion Repeller

Z

Release

10 mmEnd Plate

SIMION 7.0: simulation of the potential distribution

Laser IonsSurface Ions

UDCUDC

Atomizer

Electrons

Laser BeamsAtomsAtoms IonsIons

SwitchableElectrodes

RFQ SegmentsRFQRFQ SegmentsSegments

Accumulate

Helium Buffer Gas ~ 10-3 mbar

Laser Ionization

INTC Meeting 21.05. – 22.05.2007

Technical RealizationTechnical Realization

LIST prototypes developed and characterized in off line tests @ Mainz RISIKO MS

LIST 1 LIST 2 LIST 3 (in preparation)

Efficient resonance ionization via an all-solid state Ti:sapphire laser system:

INTC Meeting 21.05. – 22.05.2007

60 kV RISIKO Mass Separator @ UMz

ISOLDE 2 Frontend

UMz Ti:Sa laser system

Orsay EmittanceMeter

60 kV RISIKOMass Separator

@ IPhy, UMz

INTC Meeting 21.05. – 22.05.2007

Pump laser: Photonics Industries Nd:YAG, 532 nm, >80 W at 10 kHzTunable lasers: 2 single & 1 double sided UMz Ti:Sapphire lasers

- frequency doubling, tripling and quadrupling- computerized temporal and spectral control - efficient ionization of 19 elements demonstrated

tested or in user at: IKch&IPhy@UMz, TRIUMF, JYFL, Oak Ridge, LLN, ISOLDE, UNagoya

commercialized at the International Laser Fair, Munich, June 2007

Mainz Ti:Sapphire Laser Setup Mainz Ti:Sapphire Laser Setup

INTC Meeting 21.05. – 22.05.2007

Characterization of Prototype PerformanceCharacterization of Prototype Performance

LIST 2

Prototype dimensions:

Length: 10 cm

Diameter: 6 cm

Field Radius: 0.5

cm

fitting into ISOLDE target

Tests of different modes of operation:

• Ion guide, without bunching

• Bunching, low intensity, sharp beam energy (< 1 eV)

• Bunching, high intensity, broad beam energy (> 1 eV)

Important parameters for characterization:

• Overall ionization efficiency

• Isobaric selectivity via surface ion suppression

• Spatial emittance

• Energy distribution

• Temporal structure of ion bunches

INTC Meeting 21.05. – 22.05.2007

Distance between source and trap Efficiency

10 mm ~ 1·10-5

5 mm > 3,2·10-5

0 500 1000 1500 2000 2500 3000 3500

0

50

100

150

200

250

300

350

FC

curr

ent /

pA

time / s

4,391012 atoms of 69 Ga collected

6.271012 atoms of 69 and 71 Ga

21017 atoms placed in oven

= 3.1410-5

LIST operation as ion guide without buffer gas or trapping,

surface ion repeller voltage optimized for selectivity

LIST Efficiency in the Ion Guide Mode

Efficiency curve Temporal profile on peak

INTC Meeting 21.05. – 22.05.2007

-2000 0 2000 4000 6000 8000 10000 12000 14000 16000 18000

0

500

1000

1500

2000

FC

Str

om

/ pA

Zeit / s

1.16 1014 Atome Ga 69 und 71 insgesamt

davon 9,71 1012 Atome nichtresonant ionisiert

resonant

= 5.35 10-4

Optimization of Efficiency with LIST 2

Incomplete suppression of background from

too high atomic vapor density in trap:

- collisional ionization

- electron bombardment ionization

- field and black body ionization

INTC Meeting 21.05. – 22.05.2007

Efficiency

2 cm atomizer

Suppression

of surface ions (K/Ga)

Time structure

Trap capacity

Emittance

LIST RILIS@UMz

derived from RILIS and LIST Measurements in Ga @ RISIKO, UMz

5,1·10-5 1,5·10-2

> 1000 -

> 106 ions / shot -

~ 5 s > 50 s

~1.5 mm mrad

Specifications of LIST 2

• Efficiency is fully determined by atomic beam collimation and atomizer length

2 cm oven length

4 cm oven length

~1.0 mm mrad

INTC Meeting 21.05. – 22.05.2007

LIST Geometry and Ionization Efficiency

segmented, linear quadrupole

(filled with He - buffergas)

repeller

electrodes

extraction-

lenses

ionization region

atomic beam source

lasers

extraction region

extraction

electrode

• High Efficiency via well collimated atomic beam & low ionization rate before trap volume

• Optimum value so far: LIST ~ 1% of RILIS efficiency

further improvements of atomic beam source in progress

INTC Meeting 21.05. – 22.05.2007

rms 1,3 mm·mrad

Emittance Measurements Laser vs. Surface Ions Emittance Measurements Laser vs. Surface Ions

rms 1,0 mm·mrad10-7 10-6 10-5 10-4 10-3 10-2 10-1

1,2

1,4

1,6

1,8

2,0

2,2

2,4

2,6

2,8

rms

em

ittance

/ P

i mm

mra

d

buffer gas pressure / mbar

Cooling Time 0.5 ms 1 ms 2 ms

Results from Orsay emittance meter

@RISIKO, UMz, April 2007,

LIST in ion guide mode

Simulations for bunching using

Simion 3D & LISBUN

INTC Meeting 21.05. – 22.05.2007

ISOLDE 2 front end preparation for LIST targetISOLDE 2 front end preparation for LIST target

INTC Meeting 21.05. – 22.05.2007

Placement of the LIST within the ISOLDE target Placement of the LIST within the ISOLDE target unitunit

INTC Meeting 21.05. – 22.05.2007

LIST Status and ISOLDE Beam Requests

OFF-line tests:

UMz Ti:Sa laser system operation at off-line Separator in Jan./Feb. 2008

First characterization of ISOLDE LIST target on Ga, Ca, Ni and Mn

Request for 4 weeks of off-line separator use during winter shut down

in close exchange and collaboration with ISOLDE ion source crew

On-line investigations:

On-line installation & use of first ISOLDE LIST ion source on ZrO2 target

15 shifts in spring/summer 2008 for LIST characterization and 62Ga

12 shifts on autumn 2008 for LIST refinement and 62Zn

using LIST/ZrO2 target/ion source combination with laser ionization

INTC Meeting 21.05. – 22.05.2007

Maximum Ion Storage Capacity

• High importance parameter in case of high production rate of neighboring isotopes

• Integral ion beam 0,2 nA, Trap rate 350 Hz, 5 Lasershots on, 15 off, p = 3.8·10-4 mbar

• Maximum loading capacity: 4·106 Ions / cooling cycle

Loss of reasonable ion pulse time profile

40 50 60 70 80 90 100 110 120 130 140 150

0

20

40

60

80

100

120

Co

un

ts

ToF / s

Maximum loading capability

60 65 70 75 80 85 90

0

200

400

600

800

1000

1200

Cou

nts

ToF / s

Few ions in LIST trap

~10 µs

~ 2 µs

INTC Meeting 21.05. – 22.05.2007

Time StructureTime Structure

20 40 60 80 100 120 14029990

29995

30000

30005

30010

30015

30020

potentialset 1 potentialset 2 potentialset 3

Po

ten

tial /

V

z-axis / mm

60 70 80 90 100 110 120 130 140

0

1000

2000

3000

4000

5000

6000

potentialset 1 potentialset 2 potentialset 3

Co

un

ts

tof / s

20 40 60 80 100 120 140

-2

0

2

4

6

8

10

Po

ten

tial /

V

z-axis / mm

Potentialset 1 Potentialset 2

Trap closed

20 40 60 80 100 120

0

10

20

30

40

50

60

Potentialset 1 Potentialset 2

Counts

tof / s

FWHM 8.2 s

width > 60 s