Experiments with Supersonic Beams as a Source of Cold Atoms

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Since the output power of the laser described above is only 2 mW, the 1S − 2S transition cannot be driven effectively. Two steps are being taken to increase the power. The first step is the addition of a build up cavity around the atoms. This should allow the UV power to be increased by a factor of around 50. The second step is to replace the ECDL and TA of the current system with an OPSL laser [117, 118]. The OPSL has an output power of over 1.3 W and the mode quality is much better than that of the TA. This should enable more light to be coupled into the first doubler, hopefully increasing the output power at 486 nm to over 500 mW. This much blue power should increase the efficiency of the second doubler, with the goal of having 50 mW of power at 243 nm. When used in conjunction with the build up cavity, the atoms should see 2.5 W of 243 nm light. Calculations performed by Robert Clark indicate that this much light should be sufficient to excite a few percent of the atoms in the trap, and enabling the laser to be used as a background free detection method. Finally, linewidth of the OPSL (and thus the laser linewidth broadening) can be reduced as needed by locking the laser to an external cavity. 5.4.1.3 Spectroscopic Goals While the laser will initially be used to detect the atoms in the trap, it can also be used to perform spectroscopy on the trapped hydrogen. Of particular importance is the isotopic shift of the 1S − 2S transition in tritium. The current uncertainty on this measurement is several MHz [119]. By lowering the uncertainty to a few hundred kHz, the size of the triton charge radius can be measured, which is of great interest to nuclear theorists [120]. There is no reason why the linewidth of the OPSL should not be able to narrowed to below this uncertainty, and the waist of the beam in the cavity can be set so that the time of flight broadening is equivalent to the laser linewidth. Since the Zeeman broadening in the trap is only a few tens of kHz, this should not 155
prevent the determination of the isotopic shift of the 1S − 2S transition in tritium to around 100 kHz with the apparatus described above. 5.4.2 An Adiabatic Coilgun Beyond the problem of detection, research has continued on possible improve- ments to the methods used to bring the cold samples produced by supersonic expansion to rest in the lab frame. The most promising avenue for increasing the flux and phase space density of the final sample is to trap the sample and then decelerate it, as opposed to the current design which first slows and then traps the atoms. By trapping the atoms in a moving magnetic trap, they are confined in all three dimensions even though they are still moving quickly in the lab frame. Adiabatically decelerating the moving trap will then bring the trapped particles to rest without decreasing the phase space density, thereby allowing the high phase space densities produced by the initial supersonic expansion to be maintained through the deceleration process. This idea is proposed in [68]. There are several approaches to creating a moving trap which are appropri- ate for the use in an adiabatic decelerator. Moving magnetic traps have been used to transport atoms in cold atom experiments, both on microchips [121] and using macroscopic coils [122], inspiring the concept of a moving magnetic trap decelerator, though far greater velocities are needed to trap a supersonic beam in the co-moving frame. The moving and decelerated trap concept has also been applied to moving electrostatic traps for chips [123, 124] and for macroscopic electrodes [125], and these designs have been able to capture and slow molecules in a supersonic beam. A moving, though not decelerated magnetic trap has also been used to capture and translate metastable argon atoms in a supersonic beam [126]. An adiabatic magnetic decelerator has been used to stop metastable neon atoms [127, 128]. These last experiments 156
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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
Page 121 and 122: ameters. The coilgun chamber consis
Page 123 and 124: Table 4.2: Final velocities (vf), s
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: Figure 5.24: A schematic of the tel
Page 175 and 176: (a) (b) time Figure 5.25: A 1D illu
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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