Experiments with Supersonic Beams as a Source of Cold Atoms

Atom Number
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1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9
x 10 −3
0
Time (s)
Atom Number
1100
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100 200 300 400 500 600
Z − Velocity (m/s)
Figure 5.19: Simulated time-of-flight and corresponding velocity distribution for
slowed hydrogen. The simulated initial beam parameters were for a 527 m/s velocity
and 525 mK temperature. The phase of the simulated coilgun switching is
45.2 ◦ . Of the 10,000 simulated atoms entering the coilgun, 579 reach the trap center
with a velocity within 10 m/s of the 119 m/s target velocity.
with the correct velocity to be brought to rest at the center of the trap. Figure 5.19
shows the simulated time of flight and velocity distribution of a beam of atoms slowed
by the coilgun to a target velocity of 119 m/s, using a coilgun phase of 45.2 ◦ .Ofthe
10,000 simulated atoms that enter the coilgun, 668 arrive at the trap location with a
z-velocity less than 130 m/s, and 579 atoms have a final velocity within 10 m/s of the
target velocity, giving a slowing efficiency of about 6%.
Trapping of the atoms is simulated with the same initial beam conditions and
parameters. The coilgun is used in an identical configuration, and with the same phase
as above. The front trapping coil is used as the final slowing coil in this simulation.
Since there is no coil spacing which can be used in calculating the phase angle, the
position of the synchronous atom relative to the center of the coil when the front coil
is switched is used instead. A distance of 4 mm is used as the front coil switching
parameter in this simulation. The other parameter that needs to be determined is
the time when the front coil is switched back on in anti-Helmholtz orientation. While
small variations in this parameter do not greatly change the number of atoms trapped,
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