Kein Folientitel

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Techniques for precision laser spectroscopy of
trapped, highly-charged ions
M. Vogel, D.F.A. Winters, D.M. Segal, R.C.
Thompson
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What do we want to measure?
Energy of the ground state hyperfine transition
in highly charged ions
nuclear spin
e.g. 207Pb81 i.e. all but one electron stripped
FIJ
e- angular momentum
DEHFS
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Why in highly charged ions?
in atoms and singly charged ions transition is in
MW domain -gt no access with lasers, ...BUT in
hydrogen-like ions
lHFS Z-3 -gt transition in
laser-accessible range above Z60 t Z-9
-gt short lifetimes, high fluorescence rates DE
Zeeman ltlt DE HFS -gt Zeeman splitting 10-4 of HFS
207Pb81
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What do we learn?
-gt test certain aspects of HFS calculations and
their assumptions -gt a comparison of e.g. H-like
and Li-like systems cancels nuclear effects,
allows for bound-state QED tests (QED in high
fields)
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Why do it in a trap?
Ions can be cooled nearly to rest -gt small
Doppler shift Ions are well-localized -gt laser
irradiation is easy Many ions in a dense ion
cloud can be investigated at the same time -gt
high fluorescense signal Extended time for
measurement -gt makes life easier, allows slow
transitions
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Scheme of the trap setup
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Capture and trapping sequence
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Where do the ions come from?
UNILAC
400 MeV/u
U73
U92
ESR
electron coolingand deceleration down to 4 MeV/u
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Resistive cooling of an ion cloud
Cloud of 12C5 ions
we expect cooling times of several 10 s
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Rotating wall
Use segmented ring electrode to create a rotating
dipole field

Cloud rotation around z induces Lorentz force
which compresses the cloud
torque A Dw-1 T-1/2
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Choice of the magnetic field strength
Cloud dimensions and ion number density as a
function of B
Already for B1 T expected S/N is 50 -gt permanent
magnets?
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Required laser intensity
intensity to saturate the transition is given by
where A is the transition probability
Total laser power necessary is typically mW
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Expected measurement accuracy
Expected Dl/l is typically of order 10-7
e.g. 207Pb81
natural linewidth 3Hz Doppler-broadened 30
MHz transition frequency 1014 Hz Excitation
lifetime ms -gt relative accuracy 10-7
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Conclusion
We have tools to capture, confine, cool and
compress a cloud of highly-charged ions The
energy of the hyperfine transition can be
measured with an accuracy of order 10-7, which is
three orders of magnitudes better than any
previous result These measurements will allow
for a highly sensitive test of corresponding
calculations and their assumptions Comparison of
results for H-like and Li-like systems will help
to rule out nuclear effects Method also
applicable to radioactive isotopes with T½ 1h
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People involved
Richard Thompson Danny Segal Danyal
Winters Manuel Vogel Abubaker Abdullah Rafael
Castrejon-Pita