Experiments with Supersonic Beams as a Source of Cold Atoms

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show that the acceptance volume in phase space of a magnetic adiabatic decelerator is well matched to the phase space volume of a supersonic beam after the skimmer. This means that the adiabatic decelerator should capture the greatest possible flux at the highest possible phase space density. The configuration used in these last experiments is the one which will be implemented here. 5.4.3 Single-Photon Cooling of Hydrogen The coilgun method can bring samples of atoms to rest in the laboratory frame, where they can then be trapped at temperatures in the tens of millikelvin. For some applications though, the trapped atoms need to be colder than this. For true precision spectroscopy, trapping the atoms in a magic wavelength optical trap would be ideal [129], and this requires cooling the atoms to load them into the shallower optical potential. Studies of degenerate gases also require further cooling, since efficient evaporative cooling to degeneracy requires a high initial phase space density to enable collisions and short rethermalization times. This section presents a general cooling technique called single-photon cooling, which is capable of cooling nearly any species to the recoil limit [130–134]. A proposed scheme for applying single-photon cooling to atomic hydrogen isotopes [81, 135] is discussed. The principle of single-photon cooling is the creation of a one-way wall, which is permeable to atoms approaching the barrier from one direction but not from the other. A one-way wall permits a sample to be compressed without doing work on it, thus increasing the phase space density. This is illustrated for atoms trapped in a 1D potential in figure 5.25(a). While the wall increases the phase space density, the temperature of the sample is not reduced. Figure 5.25(b) illustrates how starting the wall at the edge of the trap and sweeping it slowly through the potential allows the wall to both compress the sample and reduce its temperature. In this example, the 157
(a) (b) time Figure 5.25: A 1D illustration of how a one-way call can be used to cool and compress phase space. In (a) the one-way wall is placed at the center of the trap. Atoms can pass through the wall in one direction, but not the other, compressing the atoms and increasing the density without doing work or heating the atoms. In (b) the wall is swept through the 1D trapping potential, starting from the edge of the trap. By sweeping the wall slowly, each atom encounters the wall near its classical turning point, resulting in their having low kinetic energy when they pass through the wall and are trapped by the wall and the original potential. By sweeping the wall though the entire sample, each atom has its energy reduced and the entire trap is cooled. 158
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Copyright by Adam Alexander Libson
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General Methods of Controlling Atom
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Acknowledgments First and foremost,
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to problems, and I frequently went
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General Methods of Controlling Atom
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Table of Contents Acknowledgments v
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Chapter 5. Towards Trapping and Coo
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List of Figures 2.1 Comparison of e
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5.12 Faraday Rotation Signal During
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producing a cold sample. Alternativ
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place inside a dilution refrigerato
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atoms or molecules are slowed using
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2.1 Thermodynamics of Ideal Gases F
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Since there will be no heat exchang
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Using equation 2.17 to modify equat
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Normalized Effusive Beam Flux Norma
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general method for producing cold a
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The gas throughput of the nozzle ca
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Chapter 3 Slowing Supersonic Beams
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3.1 Using Helium for Atom Optics Ex
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Figure 3.1: Calculated elastic scat
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that they can be prepared ex-situ a
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successful. Any water that remains
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Skimmer 300 l/s Turbo Pump Even-Lav
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Figure 3.5: A CAD image of the dete
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from tubular aluminum welded togeth
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Figure 3.7: A CAD image of the roto
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Figure 3.10: A CAD image of large c
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Figure 3.11: This plot shows the am
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approximations are made in this cal
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3.3.3 Detection An SRS [61] residua
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TTL pulse to the data acquisition c
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A comparison of the time-of-flight
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eceding crystal. Each curve is the
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calculated slow beam velocity is qu
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the RGA does have an effect on the
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Chapter 4 The Atomic and Molecular
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field. In the L − S coupling regi
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3 P2 E Figure 4.2: This graph gives
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For intermediate fields, the full p
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Figure 4.4: This figure illustrates
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The same effect is also responsible
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(a) (b) (c) Time Figure 4.5: A pict
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which the particles enter). The oth
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the coil can instead be switched be
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the magnitude of the field some dis
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nozzle front surface aluminum catho
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Figure 4.9: A CAD overview of the s
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258V 1MΩ 5V 1mF DC/DC Converter TT
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Figure 4.12: An oscilloscope trace
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(a) (b) Figure 4.14: A CAD image of
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-HV PS 4 M MCP Anode 10 M 1 M Trans
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Signal [V] 2.5 2.0 1.5 1.0 0.5 refe
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Figure 4.20: An exploded view of th
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(a) (b) (c) (e) Figure 4.21: A pict
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258V 1MΩ TTL 2.2mF 50Ω TTL 5V 5V
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closed. With the new thyristor gate
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HeNe M2 M1 BB /2 L BB PC coil PC PD
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Table 4.1: Peak magnetic fields mea
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Figure 4.28: A cut-away CAD image o
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ameters. The coilgun chamber consis
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Page 125 and 126: MCP Signal [arb. units] 2.0 1.5 (1)
Page 127 and 128: viability for molecules essential.
Page 129 and 130: 8 Ω LN2 Liquid Nitrogen Dewar Nozz
Page 131 and 132: Figure 4.33: Molecular oxygen slowi
Page 133 and 134: Chapter 5 Towards Trapping and Cool
Page 135 and 136: Energy meV 0.05 0.00 0.05 0.0 0.2 0
Page 137 and 138: 10 mm 2.0 T 1.8 1.6 1.4 1.2 1.0 0.8
Page 139 and 140: 250V 1MΩ 3x 2.2mF TTL 5V feedback
Page 141 and 142: Magnetic Field (T) 1.9 1.7 1.5 1.3
Page 143 and 144: 5.2.2.1 Principle of Operation of t
Page 145 and 146: Figure 5.8: Photograph of the trapp
Page 147 and 148: 4.1.3. In an anti-Helmholtz trap, t
Page 149 and 150: Figure 5.11: Photograph of the hydr
Page 151 and 152: Photodiode Signal (V) Time (s) Figu
Page 153 and 154: Figure 5.13: Time of flight plot of
Page 155 and 156: 500 l/s Turbo Pump Supersonic Nozzl
Page 157 and 158: Ionizer 500 l/s Turbo Pump Ion Opti
Page 159 and 160: guided the design of the apparatus.
Page 161 and 162: Z − Velocity (m/s) 100 60 30 0
Page 163 and 164: Atom Number 60 50 40 30 20 10 0.6 0
Page 165 and 166: scattered photon to extract informa
Page 167 and 168: where k1 · pi = − k2 · pi, wh
Page 169 and 170: the electron g-factor which causes
Page 171 and 172: Figure 5.24: A schematic of the tel
Page 173: prevent the determination of the is
Page 177 and 178: experiment, where a being is capabl
Page 179 and 180: potential position 2 x 243 nm Lα |
Page 181 and 182: Appendix 164
Page 183 and 184: y x V i Figure A.1: The geometry us
Page 185 and 186: Bibliography [1] H.J.MetcalfandP.va
Page 187 and 188: [17] Brian C. Sawyer, Benjamin L. L
Page 189 and 190: [34] R. Campargue. Progress in over
Page 191 and 192: [51] O. Carnal, M. Sigel, T. Sleato
Page 193 and 194: [70] Edvardas Narevicius, Adam Libs
Page 195 and 196: [87] Willis E. Lamb and Robert C. R
Page 197 and 198: [96] G.Gabrielse,N.S.Bowden,P.Oxley
Page 199 and 200: [110] N. Kolachevsky, J. Alnis, S.
Page 201 and 202: [125] Andreas Osterwalder, Samuel A
Page 203 and 204: [142] C. Cohen-Tannoudji, B. Diu, a
Page 205 and 206: [161] Paulo F. Bedaque, Aurel Bulga
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Experiments with Supersonic Beams as a Source of Cold Atoms

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