Laser pumping of ions in a cooler-buncher The University of Manchester, UK The University of...
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Transcript of Laser pumping of ions in a cooler-buncher The University of Manchester, UK The University of...
Laser pumping of ionsin a cooler-buncher
The University ofManchester, UK
The University ofBirmingham, UK
At the JYFL accelerator facility, Finland
Collinear laser spectroscopy
Laser Ion source (cooler)
PMTGates
+40kV
+/-≈3kV
Platform
∙ Isotope shifts
∙ Hyperfine splitting
Magnetic moment<β2>Quadrupole moment
δ<r2>
δσ
Size
Shape
Diffuseness
• Fast and sensitive
δ<β22>
Reduced peak skewingReduced peak skewing
The RF cooler-buncher
z
V
z
He buffer gas End plate
Energy spread 100eV 1eV
Emittance = 3п.mm.mrad
Less spectral broadening
Better laser-ion overlap
Bunching and laser spectroscopy
Cou
nts
Cou
nts
0
30
100
2005.25 hours 48 minutes8000 ions/s 2000 ions/s
100V
zEnd
pla
te p
oten
tial Accumulate
Release
Before
After
PMT
15µs gate
Background eg. 200ms accumulation=20µs gate widthsuppression ~10
4
New results: multi QP isomers
Raghavan'89
Multi-QP states Reduced pairing• Less diffuse or more rigid
• Linked to origins of odd-even staggering?
Yttrium results
J = 0 J = 1 electronic transition
⇒ 3 peaks for each nuclide (maximum)
gives the centroid, μ and Q
One resonant photon per 2000 ions
Efficiency:-
• Shape change at N=59
• 98m is well deformed
Problem 2: “Collapsed” ground states
Difficult to resolve underlying peaks and ordering
Spin ½
Spin 2
Spin ½ + isomer peak
363 nm pumping of yttrium
1 photon for every 6000 ions becomes 1 for every 3000 ions
(End of the beam line)
• Indifference to bunching
• Pumping saturates at 30mW
• Can use broadband lasers
Other possibilities: background suppression
Bro
adba
nd la
ser
pum
ping
ste
p Hig
h re
solu
tion
l
aser
ste
p
Hig
h re
solu
tion
l
aser
ste
p
Dec
ay d
etec
ted
by P
MT
Dec
ay d
etec
ted
by P
MT
Future work: polarisation
F=5/2
F=3/2
MF =-5/2 -3/2
-1/2
+1/2 +3/2 +5/2
-3/2
-1/2
+1/2 +3/2
In a strong magnetic field, the spins decouple leaving the nuclearspins polarised and allowing NMR experiments to be performed
Weak magnetic field ⇒ Zeeman splittingσ+ circularly polarised light ⇒ spin polarisation in state of maximum MF
Summary
• Method of controlling state population
• Choose transitions on basis of strengths, spins, splitting and charge state
• Cooler provides a focal point of slowly travelling ions
• Ti:Sa lasers provides wider range of wavelengthsand bandwidth or pulsing does not matter
• Necessary for yttrium; other cases being considered
• Aim to produce polarised beams out of the cooler for β-NMR work
Collaborators
The University of Manchester, UK
The University of Birmingham, UK
The JYFL accelerator laboratory, Jyväskylä, Finland
J. Billowes, P. Campbell, B.Cheal, B.A. Marsh, B.W. Tordoff
T. Eronen, J. Huikari, A. Jokinen, T. Kessler, I.D. Moore, A. NiemenenH. Pentillä, S. Rinta-Antila, J. Äystö
M.L. Bissell, D.H. Forest, G. Tungate