The Collinear Resonance Ionization
Spectroscopy (CRIS) Programme atISOLDE
Jon Billowes for the CRIS Collaboration

Isotope shift of an atomic transition
ppm shift

Analysis of shift yields the change innuclear mean square charge radius:δ<r2> = <r2>A´
Isotope A<r2>AA´volumeRθ

R = R0 ( 1 + β2 Y2,0 (θ,φ))zdeformation

Hyperfine Structure of atomic transition
Analysis of hyperfine
factors

Upper atomicstate

ν0Nuclear spin I
Lower atomicstate

Magnetic moment µQuadrupole moment Qs

Experimental
spectrum+isotope shifts
ν0For measurements on radioactive nuclei, need:• High sensitivity• High (sub-Doppler) resolution

δ<r2>High sensitivity method developed at JYFL:
Bunched‐beam collinear laser spectroscopy
Gas‐filled linear RFQ trap

Ion beamcoolerLaser beam
Light collection region
5 μs(Laser resonance fluorescence)+39.9 kV
40 kV

Reduces energy-spread of ion beam
Improves emittance of ion beam

+40 kVIon source

Trap and accumulates ions – typically for 300 ms
Photons
only
countedduring the 5µs when ionReleases
ions ina 15µs bunchbeam passes photomultiplier tube.
50 ms trapping = 104 reduction in backgroundcompared with a continuous ion beam

High sensitivity method developed at JYFL:
Bunched‐beam collinear laser spectroscopy
Gas‐filled linear RFQ trap

Ion beamcooler

Laser beam
Light collection region(Laser resonance fluorescence)+39.9 kV
40 kV

Reduces energy-spread of ion beam
Improves emittance of ion beam

+40 kVIon source

Inefficientof signal ions – typically for 300 ms
Trapdetection
and accumulates
All improved by• Smallsolid angle
Releasesions in a 15 µs bunch counting ions
• Low quantum efficiency
instead of photons• Background from laser lightCount ions instead:
Collinear Resonance Ionization Spectroscopy (CRIS)
Atom bunch(mass selected, A)(only a very small fraction of thisbeam may be the nuclide ofinterest)

Synchronizedlaser pulses

Lasers only ionize
selected element, Z

Method can either measure laser resonances with highsensitivity and low background

Microchannel
plate
Ion Counter6

Count ions instead:
Collinear Resonance Ionization Spectroscopy (CRIS)
Atom bunch(mass selected, A)(only a very small fraction of thisbeam may be the nuclide ofinterest)

Synchronizedlaser pulses

Lasers only ionize
selected element, Z

Method can either measure laser resonances with highsensitivity and low background

Ion Counter

oror

provide hyper‐pure samples of exotic nuclei, forlow‐background nuclear spectroscopy

Catcher foil station &Nuclear radiation detectors(LANDS: Laser‐assisted nuclear decay spectroscopy)
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ISOLDE ‐ CERN
1.4 GeV protons
from PSB

GPS target

radioactive
laboratory
HRS target

GPSHRS
controlroom

ISCOOL

CRIS laser line

ion beambuncher
HIE ‐ ISOLDE extension

CRIS beam-line

Interaction region(ultra high vacuum tominimize collisionalionization)

First measurements – francium isotopes
202-206,218,219,229,231Fr
179-185Tl

197,198,203,205,207,209,211,217At

191-210,216,218Po
182-189Pb
177-182Au

Neutron-rich Fr with CRIS:
Poster PS1-B031 (Ivan Budincevic)

N = 126
Neutron-deficient Fr isotopes at TRIUMF (high resolution):
A. Voss et al., Phys. Rev. Lett. 111, 122501 (2013)

30 Hz Nd:YAG (15 mJ)
synchronized with a pulse from a

RILIS frequency-doubled
10 kHz Ti:Sa (~50 mW)

Francium laser ionization scheme

K.T. Flanagan et al: proposal to INTC tomeasure Fr isotopes, 200811

Example spectrum: 204Fr ground state and two isomers

Resolution: limited only by Ti:Sa pulsed laser to 1.5 GHz
Efficiency: 1% - including beam transport, neutralization, ionization and detection
Lowest yield: 202Fr measured with production yield of ~100 atoms/sec
Neutron-deficient isotopes measured: Charge radii and magnetic moments for 202g,202m,203,204g, 204m1, 204m2, 205, 206g, 206m1, 206m2,

LANDS – laser assisted nuclear
decay spectroscopy:
separation of 204Fr ground state andtwo isomers

Alpha spectrum
K.M. Lynch et al., Phys. Rev. X 4 011055 (2014)

Laser resonance spectrum

Mean square charge radii of francium isotopes

The CRIS Collaboration

J. Billowes, T.E. Cocolios, K.T. Flanagan, T.J. Procter, A. Smith, I. Strashnov,
K.M. Lynch, S. Franchoo, V. Fedosseev, B. Marsh, G. Simpson, M. Bissell,
I. Budincevic, R.P. De Groote, S. De Schepper, R.F. Garcia Ruiz, H. Heylen, J.
Papuga, G. Neyens, H.H. Stroke, R.E. Rossel, S. Rothe, K. Wendt

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kara.marie.lynch@cern.ch