Experiments with Supersonic Beams as a Source of Cold Atoms
Experiments with Supersonic Beams as a Source of Cold Atoms
Experiments with Supersonic Beams as a Source of Cold Atoms
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the RGA does have an effect on the reflected intensity <strong>of</strong> the beam, and electrons or<br />
met<strong>as</strong>table atoms from the RGA may be de-p<strong>as</strong>sivating the surface <strong>of</strong> the crystal.<br />
Since it appears that de-p<strong>as</strong>sivation <strong>of</strong> the silicon surface is at le<strong>as</strong>t partially<br />
responsible for the decay in the reflected intensity, other crystal options were consid-<br />
ered. Lithium fluoride is also a very p<strong>as</strong>sive crystal and can be cleaved to create clean<br />
smooth surfaces. Lithium fluoride w<strong>as</strong> studied <strong>as</strong> a possible replacement for silicon<br />
<strong>as</strong> a crystal surface and this work is described in [55].<br />
3.5 Potential Applications<br />
The ability to reduce the velocity <strong>of</strong> a supersonic beam <strong>of</strong> helium <strong>with</strong>out heat-<br />
ing is an enabling technology and this section discusses several potential applications<br />
<strong>of</strong> this technology. One possible use <strong>of</strong> the slowed beam is to study atom-surface<br />
interactions. The short nozzle pulse compared to the slow beam propagation time<br />
leads to an expected energy resolution <strong>of</strong> 2μeV [33]. This energy resolution, combined<br />
<strong>with</strong> ability to quickly and precisely tune the velocity <strong>of</strong> the beam, makes it ideal for<br />
studies <strong>of</strong> the atom-surface potential. The slowing would also permit this potential<br />
to be mapped in a new energy range. There is no re<strong>as</strong>on that this technique would<br />
not work <strong>with</strong> Helium 3 <strong>as</strong> well, permitting even greater energy resolution using the<br />
spin echo technique [47], along <strong>with</strong> precise control over the velocity and an extended<br />
energy range <strong>of</strong> interrogation.<br />
Another potential application is in the field <strong>of</strong> atom interferometry [63–65].<br />
Ground state noble g<strong>as</strong>es are insensitive to magnetic fields to first order, and helium’s<br />
low polarizability makes it comparatively insensitive to electric fields, reducing the<br />
potential for errors due to stray fields. These traits make it an ideal candidate for<br />
use in interferometry. For a white light geometry Mach-Zender interferometer <strong>of</strong><br />
length L rotating at a rate Ω, the ph<strong>as</strong>e shift φ imparted on the beam is φ = 2πΩL2<br />
vd<br />
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