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