helmholtzzentrum für schwerionenforschung
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Helmholtzzentrum für Schwerionenforschung
Fluorescence detection in a Penning trapFluorescence detection in a Penning trap
Radu CazanRadu Cazan
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~50 MHz
Flu
ore
sce
nce
ra
te (
cps)
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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Flu
ore
sce
nce
ra
te (
cps)
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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500000 1072024,8 1072025,2 1072025,6
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Frequency (GHz)
Flu
ores
cenc
e ra
te (
cps)
Zeeman shift
Zeeman shift: 13.996 GHz/Tesla
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Laser detunning (MHz)
+Flu
ore
sce
nce
ra
te (
cps)
-
Fluorescence vs. polarization
Quantized fluorescence jumps
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Laser detunning (MHz)
4 ions
3 ions
Flu
ore
sce
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ra
te (
cps)
2 ions
0 1 2 3 4 5 6 7 8 9 10 110
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1600D
ete
cte
d p
ho
ton
s
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
-500 -400 -300 -200 -100 0 100 200
0
100000
200000
300000
400000
500000
600000
700000
800000
~50 MHz
Flu
ore
sce
nce
ra
te (
cps)
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
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