Experiments with Supersonic Beams as a Source of Cold Atoms

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field can be seen in figure 5.6. There are two curves shown here, one for the initial pulse, and one after the wires and resistors in the circuit have heated up by pulsing the coil at a .5 Hz repetition rate. One other change made from the coilgun used to slow neon and oxygen is in the control electronics. The larger coils of the hydrogen slower mean that the timing resolution needed in the control circuitry is reduced. Simulations show that the timing resolution of 100ns used in the 64 stage coilgun does not have any benefit over a much easier to implement 1 μs resolution. Because the experiment is controlled by LabVIEW, it is simpler to use LabVIEW and National Instruments data acquisition cards (NI PCIe-6259) to control the coil timing, rather than using LabVIEW for data acquisition and an FPGA for control. 5.2.2 Trapping Coils and Electronics The experimental goals require trapping the slowed hydrogen atoms at the end of the coilgun, and so the experiment must incorporate a trapping potential and a method of bringing the atoms to rest at the center of that potential. Because the coilgun operates on low-field-seekers, the slowed atoms are already in a magnetically trappable state, and state preparation between the coilgun and the trap is not nec- essary. A static magnetic trap is a conservative potential, and the atoms must first be brought to rest in the trapping volume. The proposed trapping sequence this is explained in this section. The details of the anti-Helmholtz magnetic trap and the switching circuitry built to control the magnetic potentials created by the trapping coils are described. 125
5.2.2.1 Principle of Operation of the Trap To maximize the number of atoms trapped at the end of the coilgun, the coilgun and trap need to be mode-matched. What this means is that the stable phase space volume of the trap should closely match with the phase space volume occupied by the slowed atoms at the end of the coilgun. Using an anti-Helmholtz trap configuration, with appropriate coil dimensions and spacing, enables this. The anti-Helmholtz trap is placed as close as possible to the end of the coilgun, and the coils are co-axial with the coilgun coils. To aid in the mode-matching of the atoms to the trap, the first trapping coil the atoms encounter (this is referred to from now on as the front trapping coil) will be used as a final slowing coil, and will be operated in the same manner as the coilgun coils. Initially both trap coils are turned on with the same polarity (the polarity of the coilgun coils). As the atoms enter the front trapping coil, the coil is switched off, in an exact analog to the coilgun coils used to slow the atoms. Using the front trapping coil in this manner serves several purposes. First, since the coil is used as the final slowing coil, the atoms can be extracted from the coilgun at a slightly higher velocity, enabling a slightly greater stable phase space volume in the coilgun. Additionally, using the front trapping coil to do the final slowing means that the atoms do not have much distance to propagate between the last slowing coil and the trap center, limiting the degree to which the packet of atoms will spread out during this propagation. Finally, the phase stability and waveguide effects of the coil serve to preserve the phase space density of the slowed packet and aid in the mode matching of the slowed atoms to the trap. After the atoms have passed through the front trapping coil, they enter the trapping region and will be brought to rest by the magnetic potential of the rear trapping coil. The phases of the coils in the coilgun can be tuned such that the 126
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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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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
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: Magnetic Field (T) 1.9 1.7 1.5 1.3
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 and 174: prevent the determination of the is
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
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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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