Helmholtzzentrum für Schwerionenforschung

Fluorescence detection in a Penning trapFluorescence detection in a Penning trap

Radu CazanRadu Cazan

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Laser detunning (MHz)

-> laser scanned in 100 sec over 2 GHz

First peak – from where?

?

26Mg+: ~3 GHz to the right!

The beamline & the trap

Channel Photomultiplier

Injection of externally produced ions

• dynamic ion capture cycle

• low energy and TOF allow selection of captured ions

Option with a cooling mechanism: Stacking of successive ion bunches

• 2 ms gate

• up to 5 Hz

• almost no ion loss

No detectable fluorescence for hot ions – the ones which are most probably in the middle!

Maintain the laser redshifted for a cold ion and leave the axial motion do the job:

ωz

ωz

Cooling time for 100 eV ions: ~1 s.

Cooling the axial motion

Isat=2.5 mW/mm2

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Laser detunning (MHz)

-> laser scanned in 100 sec over 2 GHz

100 K 1.57 GHz

10 K 496 MHz

1 K 157 MHz

Natural linewidth

43 MHz

1 mK (ħΓ/2kB)

2 MHz => T~0.1 K

=> T<<0.1 K

Fluorescence and line profile

1072024,8 1072025,2 1072025,6

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Flu

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Zeeman shift

Zeeman shift: 13.996 GHz/Tesla

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Fluorescence vs. polarization

Quantized fluorescence jumps

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Laser detunning (MHz)

4 ions

3 ions

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2 ions

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Trapped ions

Y = A + B * X

Parameter Value Error------------------------------------------------------------A 26,97901 19,53865B 144,48816 3,62167------------------------------------------------------------

~145 photons per ion per cooling cycle~ 300 cps fluorescence rate per trapped ion

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Laser detunning (MHz)

-> laser scanned in 100 sec over 1 GHz

Estimation of the trapped ion number

~ 145 photons per ion per cooling cycle~ 300 cps fluorescence rate per ion

Height=728.000 cps => ~2400 ions

Area=1.950.000 photons=> up to 13.500 ions

Laser system for cooling of Mg+

= 1118 nm

= 279 nm

P ≈ 950 mW

= 559 nm

P ≈ 4 mW

P ≈ 320 mW

P ≈ 17 mW

P ≈ 200 mWP ≈ 100 mW

P ≈ 500 mW

Further planned measurements

Type Ion Transition [nm] A [1/s]

low q 207Pb+ 2P1/2 - 2P3/2 710.17 24

B-like 40Ar13+ 2P1/2 - 2P3/2 441.24 104

C-like 40Ca14+ 3P0 - 3P1 569.44 95

H-like207Pb81+ F=0 - F=1 1019.7 20209Bi82+ F=4 - F=5 243.9 2849

Li-like 209Bi80+ F=4 - F=5 1555 12

final accuracy limited by the Doppler broadening

• with resistive cooling /0 ≈ 10-6 to 10-7

• with sympathetic cooling /0 ≈ 10-7 to 10-82

0

2ln8

mc

TkBD

Type Ion Transition [nm] A [1/s]

low q 207Pb+ 2P1/2 - 2P3/2 710.17 24

Verdi V18 pumped Ti:Sa Laser, 700-1100 nm, ~1 W output with 10 W of 532 nm

Type Ion Transition [nm] A [1/s]

C-like 40Ca14+ 3P0 - 3P1 569.44 95

Verdi V18 pumped Coherent 699 Dye Laser, >0.5 W output with 9 W of 532 nm

view of the trap and the magnet