Blue MOT Trap atom number Loading Rate Zeeman slower flux
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Transcript of Blue MOT Trap atom number Loading Rate Zeeman slower flux
Blue MOT Trap atom number
Loading RateZeeman slower flux
Trap laser (6 mW - 1 cm diameter) x 6-G/2 detuned to 171Yb 1P1
oven Zeeman slower
Trapped atom number
Lens f=7.5 cm, diameter d=2.54 cm
PMT = 5 V @ vcon= 0.3 V
Power meter = 0.3 mW
D=15 cm
𝜃
= 0.14𝑠=
𝑠01+¿¿
Gn
n
oven Zeeman slower
Flux measurement
Trap laser (6 mW - 1 cm diameter) x 20 Hz detuned to 171Yb 1P1
PMT = ~ 2 V @ vcon= 0.608 V
Fluorescent power of atomic beam is too weak to be measured by power meter, thus a calibrated PMT was used. Calibration reference PMT = 5 V @ vcon= 0.300 V P = 0.3 W
However PMT gain varies with control voltage, thus PMT gain with control voltage was measured.
PMT gain with control voltage
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9100
101
102
103
104
105
PM
T vo
ltage
(V)
control voltage (V)
PMT voltage (V) is normalized to be 1 volt when control voltage is 0.2 V
0.18 0.20 0.22 0.24 0.26 0.28 0.30 0.32 0.34 0.36 0.38
0
20
40
60
80
100
PM
T vo
ltage
(V)
control voltage (V)0.50 0.52 0.54 0.56 0.58 0.60 0.62 0.64 0.66 0.68 0.70
0
2000
4000
6000
8000
10000
PM
T vo
ltage
(V)
control voltage (V)
Gain ratio =189
Mixture of ther-mal and slowed atoms
Thermal atoms 1
Thermal atoms 2
Non-atomic scattering
Probe laser o o o oMagnetic field o x o oZeeman slowing laser o o x oAtomic beam o o o xPMT voltage (v) 2.45 2.35 2.10 0.14V - 0.14 2.31 2.21 1.96 0
1. What was measured is the number of atoms inside interaction volume.
2. What is to be measured is the loading rate of MOT, which is the flux of atomic beam.
3. Flux is always preserved while the speed of atoms vary with Zeeman slower.
4. Flux varies only with oven temperature.
5. The number of atoms inside interaction volume varies with the speed of atoms.
Atomic beam fluorescence
Total number of atoms interacting with probe laser𝑁=𝐹𝑙𝑣
F is flux of atomic beam : N cm-2s-1
A is area of interaction L is interacting lengthv is velocity of atoms
𝑙
𝐴𝐹𝑣
Density of atoms interacting with probe laser n=N/cm-3𝑛= 𝐹𝑣𝐴
PMT signal : 2 V @ vcon=0.608 V 0.011 V @ vcon=0.300 V 0.00066 W
= 0.1=0)
Gn
n
= 30000 cm/s
= 1.4 = 1.54 /cm2
= 1.5 l𝑜𝑎𝑑𝑖𝑛𝑔𝑟𝑎𝑡𝑒𝛼=𝜀 𝐹𝐴𝑡𝑟𝑎𝑝𝑐𝑟𝑜𝑠𝑠𝑠𝑒𝑐𝑡𝑖𝑜𝑛
-10 -5 0 5 10
0
2
4
6
8
PM
T si
gnal
( V)
s
Model ExpDecayEquation y = y0 + A
1*exp(-(x-x0)/t1)Reduced
Chi-Sqr0.06023
Adj. R-Sq 0.9736Value Standard
DPO3014 y0 6.386 0.00308DPO3014 x0 1.218 --DPO3014 A1 -6.22 --DPO3014 t1 0.616 0.00169
N atoms = 3X107 ( pmt signal 6 v)
Loading rate = = 4.8
=0.032
3.2 % of atoms are trapped. Atoms may defuse out by Zeeman slower. Only a small fraction of slowed atoms can reach MOT re-gion.
Loading rate from MOT experiment
=
Zeeman slowed Atom density
n()=
Atom density ) variation by a contribution of slowed atom of
We can know the value of by comparing the PMT signal of the table
Mixture of ther-mal and slowed atoms
Thermal atoms 1
Thermal atoms 2
Non-atomic scattering
Probe laser o o o oMagnetic field o x o oZeeman slowing laser o o x oAtomic beam o o o xPMT voltage (v) 2.45 2.35 2.10 0.14V - 0.14 2.31 2.21 1.96 0
Assume vslow=30 m/sVmp =300 m/s
0.005 0.02