Experiments with Supersonic Beams as a Source of Cold Atoms

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coilgun is only able to slow a portion of initial phase space volume. Part of this is due to the phase space acceptance of the coilgun as defined by its volume of phase stability. It is also partially due to the fact that not all of the oxygen molecules in the initial beam are in the correct angular momentum state to be slowed by the coilgun. Comparison with simulation indicates that the oxygen coilgun has an efficiency which ranges from around a percent for the least slowing, to about a tenth of a percent for maximal slowing. Slowing of a molecule using the coilgun method demonstrates the broad ap- plicability of pulsed magnetic slowing of supersonic beams. The supersonic source is a general method of producing cold but fast samples and, as demonstrated here, the coilgun is a general method of reducing the velocity of these cold samples to trap- pable velocities. These techniques combine to provide a general method of controlling atomic motion. 115
Chapter 5 Towards Trapping and Cooling of Atomic Hydrogen Isotopes Having verified that the coilgun functions as a general method of producing slow and cold samples, the next step is to use the samples it produces to make a phys- ical measurement. For many measurements, such as precision spectroscopy, a long interrogation time is highly desirable. Even with a slow beam, the observation time is limited because the atoms are not confined to the interrogation region. However, by integrating a trap with the end of the coilgun, the atoms can be observed for several seconds at a time (depending on the lifetime of the trap). This chapter describes the ongoing experiment to trap, cool, and study atomic hydrogen isotopes. The coilgun is modified to a hydrogen specific device and these modifications, along with the reasons behind them, are described. Hydrogen plays a particularly important role in physics and the rational behind the desire use the coilgun to study hydrogen is explained. An anti-Helmholtz magnetic trap is added to the end of the coilgun to trap the slowed atoms, and this trap and its switching electronics are detailed. The entire device is characterized and is believed to be working properly. While the experiment has not yet succeeded in detecting trapped hydrogen, for reasons which are explained, detailed simulations have been performed. These simulations suggest that the hydrogen coilgun and trap will operate with high efficiency, trapping a significant quantity of the atomic hydrogen entering the coilgun. The apparatus described in this chapter is also described in [81]. Finally, the future goals of the experiment, including a proposed method for cooling the trapped atoms 116
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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
Page 81 and 82: Figure 4.4: This figure illustrates
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Page 85 and 86: (a) (b) (c) Time Figure 4.5: A pict
Page 87 and 88: which the particles enter). The oth
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Page 93 and 94: nozzle front surface aluminum catho
Page 95 and 96: Figure 4.9: A CAD overview of the s
Page 97 and 98: 258V 1MΩ 5V 1mF DC/DC Converter TT
Page 99 and 100: Figure 4.12: An oscilloscope trace
Page 101 and 102: (a) (b) Figure 4.14: A CAD image of
Page 103 and 104: -HV PS 4 M MCP Anode 10 M 1 M Trans
Page 105 and 106: Signal [V] 2.5 2.0 1.5 1.0 0.5 refe
Page 107 and 108: Figure 4.20: An exploded view of th
Page 109 and 110: (a) (b) (c) (e) Figure 4.21: A pict
Page 111 and 112: 258V 1MΩ TTL 2.2mF 50Ω TTL 5V 5V
Page 113 and 114: closed. With the new thyristor gate
Page 115 and 116: HeNe M2 M1 BB /2 L BB PC coil PC PD
Page 117 and 118: Table 4.1: Peak magnetic fields mea
Page 119 and 120: 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
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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
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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 and 174: prevent the determination of the is
Page 175 and 176: (a) (b) time Figure 5.25: A 1D illu
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Page 181 and 182: Appendix 164
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y x V i Figure A.1: The geometry us
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Bibliography [1] H.J.MetcalfandP.va
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[17] Brian C. Sawyer, Benjamin L. L
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[34] R. Campargue. Progress in over
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[51] O. Carnal, M. Sigel, T. Sleato
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[70] Edvardas Narevicius, Adam Libs
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[87] Willis E. Lamb and Robert C. R
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[96] G.Gabrielse,N.S.Bowden,P.Oxley
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[110] N. Kolachevsky, J. Alnis, S.
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[125] Andreas Osterwalder, Samuel A
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[142] C. Cohen-Tannoudji, B. Diu, a
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[161] Paulo F. Bedaque, Aurel Bulga
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Experiments with Supersonic Beams as a Source of Cold Atoms

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