Experiments with Supersonic Beams as a Source of Cold Atoms

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signal is masked by the background due to molecules. Figure 5.13 shows the ratio of DtoD2 (multiplied by 100) with and without the discharge. The background signal due to molecular hydrogen left in the beam presents a major problem for the experiment. This signal obscures the atomic signal and the experiment has been unable to use the quadrupole as originally intended. Other detection methods are being investigated, and their use is more fully explored in section 5.4.1. 5.2.4 Vacuum Chambers The vacuum chambers for the hydrogen experiment can be divided into three sections, the beam creation and differential pumping chambers, the slowing and trapping chamber, and the detection chamber. While the beam creation chamber is quite similar to the design used for the previous experiments, the beam slowing and trapping chamber is quite different from the one used in previous generations of the coilgun since the coils are outside of the vacuum envelope. Also, in the previous coilgun experiments there was no dedicated detection chamber. Previously the supersonic nozzle was in the center of a 6-way 6 inch cross, but in the hydrogen experiment the nozzle is in the center of a 6-way 8 inch cross. This change was made to allow for more space around the nozzle, as placing the filament for the discharge was difficult in the previous setup. The cross is pumped by a 500l/s Varian turbomolecular pump. The base of the skimmer (5mm diameter) now sits 142 mm from the exit of the nozzle. From the skimmer, the beam goes though a2− 3/4 inch bellows to a 4-way 2 − 3/4 inch cross which is pumped by a 70 l/s Varian turbo pump. Another skimmer (3 mm diameter) sits 380 mm from the nozzle. This second chamber provides differential pumping. Differential pumping is needed because of the small diameter of the slowing and trapping chamber. The conductance 137
500 l/s Turbo Pump Supersonic Nozzle 70 l/s Turbo Pump Skimmer Locations Figure 5.14: A CAD image of the hydrogen valve chamber and differential pumping chamber. The nozzle hangs from the pool type cryostat in the center of the 8 inch cross. The chamber on the right provides differential pumping. of these latter chambers is low enough that without differential pumping, the gas load from the supersonic beam would build up in these chambers, decreasing the mean free path and trap lifetime. A CAD drawing of the valve chamber and differential pumping chamber can be seen in figure 5.14. The slowing and trapping chamber consists of two parts, the coilgun tube and the trapping cross. The coilgun tube has two titanium 1.33 inch conflat flanges separated by a 22.0cm grade 5 titanium tube. The tube has a wall thickness of .38mm and an outer diameter of 9.52mm. The reason this titanium alloy is chosen is its high electrical resistance which reduces the eddy currents caused by the coil, coupled with its lack of magnetism and good vacuum properties. The coils are wound around the tube, with the center of the first coil sitting 43.44 cm from the nozzle. This chamber has 15 of the 18 coilgun coils wound around it (the last three coils are wound around the trapping chamber). A CAD image of the slowing and trapping chamber, with the coils, is shown in figure 5.15 and a photograph of the assembled chamber with the coils is presented in figure 5.16. 138
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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
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 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: Figure 5.13: Time of flight plot of
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
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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