Experiments to Control Atom Number and Phase-Space Density in ...

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BGauss 0.5 0.4 0.3 0.2 0.1 0.0zm Figure 7.13: Measured Zeeman slower field profile. The ideal beam profile (black) and the expected profile (grey) are compared to experimental data (blue). atom numbers. During the experiment the Zeeman slower does not run continuously, but turns on only for one to two seconds during each experimental cycle. It is therefore not necessary to cool the Zeeman slower coils. However, during the alignment procedure the Zeeman slower is frequently run at a larger duty cycle. In order to avoid overheating of the Zeeman slower coils, an interlock system is installed that will automatically shut-off the current if the temperature of the coils exceeds 65 ◦ C. It also limits the time the Zeeman slower can be run continously to 15 minutes. The current to the Zeeman slower is provided by two separate power supplies. Coils 1-7 are driven by a Sorensen power supply (DCR40-35A), the current to coil 8 is provided by a Kepco power supply (36-15M). To improve the current stability, a PID current controller regulates the current [68]. In addition this current controller is TTL- controlled by the computer control program, so that the current to the Zeeman slower coils can be turned on and off remotely. 105 700 600 500 400 300 200 100
7.2.2 MOT Coils A second set of coils used during the experimental sequence is a pair of anti- Helmholtz coils that creates the quadrupole magnetic field of the MOT. These coils are designed to fit around the flange of the reentrant viewport, see figure 7.14. Each MOT coil is comprised of four individual coils, which are then stacked and wired in series. The individual coils have 22 windings made from flat wire with dimensions 4.85 mm × 1.12 mm (MWS Wire Industries, 41172) and polyimide-220 coating. The inner radius of the coils is 152 mm, just large enough to slide over the flange of the reentrant viewport. The coil windings are connected using Epoxy Technology 360 epoxy. The individual layers are then glued together using a thermally conductive epoxy (Epoxy Technology, 920) and attached to a copper plate. This copper plate is water-cooled to avoid overheating of the coils. The flow rates through the copper plate are 2.4 l/min and 2.6 l/min for the lower and upper MOT coils respectively. Figure 7.14: MOT coils mounted around the reentrant viewport. The MOT coils are separated by 70.6 mm, the height of the spherical octagon. At a current of 36 A, the gradients near the center of the trap are 43.7 G/cm axially, and 21.9 G/cm radially. The coils are wired in series, and the current is supplied by three power supplies (Lambda, GEN80-19) wired in parallel. One of the power supplies is programmed as the master power supply, the other two as slave power supplies. In this configuration only one of the power supplies needs to be controlled; the other two will 106
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Copyright by Kirsten Viering 2012
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Experiments to Control Atom Number
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Acknowledgments First of all, I wou
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Experiments to Control Atom Number
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Table of Contents Acknowledgments v
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Chapter 7. Lithium Apparatus 92 7.1
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List of Tables 2.1 Physical propert
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4.1 Vacuum chamber . . . . . . . .
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7.39 Future vertical axis optics .
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The development of techniques to la
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Ptorr 10 5 10 6 10 7 10 8 10 9 260
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Property Symbol Value Reference Ato
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2.3.2 Hyperfine Structure So far th
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The Wigner-Eckhart theorem can be u
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The total magnetic moment of an ato
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interaction. The shift in the energ
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(a) (b) scattering length a 0 Energ
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a laser field with frequency ω. Th
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Here ω0 is the resonance frequency
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Optical molasses do not provide a s
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J=1 J=0 -1 Δ σ + σ - σ - 0 +1 -
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phase-space density is defined as
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which maintains a constant η = U/k
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2.12.1 Saturated Absorption Spectro
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Figure 2.22: Saturation absorption
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Signal 0 Signal (a) (b) Signal Freq
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(a) (b) (c) (d) Figure 2.24: Absorp
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y more complex energy level structu
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ight side of the box. An irreversib
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time (a) (b) (c) Figure 3.3: Single
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them to move from B to A, but close
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Figure 4.1: Vacuum chamber. Photogr
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( ( Figure 4.3: Helicoflex seal. (a
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88 mm 4.2.3 Auxiliary Coils 62 mm Q
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5 2 P 3/2 5 2 S 1/2 384. 230 484 46
Page 71 and 72: distribution of the MOT master lase
Page 73 and 74: shifts. First a frequency shift of
Page 75 and 76: transition. However, the laser freq
Page 77 and 78: 4.3.1.4 Upper MOT Horizontal Slave
Page 79 and 80: provides the beam for the upper MOT
Page 81 and 82: demon beam λ λ horizontal MOT bea
Page 83 and 84: scholar, Florian Schreck. It is wri
Page 85 and 86: Atoms are then optically pumped to
Page 87 and 88: ferred into the |F = 1,mF = 0〉 or
Page 89 and 90: 5.2 Branching Ratios and Population
Page 91 and 92: effect of the reflected beam at zer
Page 93 and 94: y the repulsive trough beams, gaini
Page 95 and 96: Figure 5.9: Atom number as a functi
Page 97 and 98: Figure 5.10: Radius of the magnetic
Page 99 and 100: on the collision rate of atoms insi
Page 101 and 102: ferred via the single-photon coolin
Page 103 and 104: By comparison an atomic Fock state
Page 105 and 106: of atoms in the two hyperfine groun
Page 107 and 108: difference in the lifetimes is dete
Page 109 and 110: Chapter 7 Lithium Apparatus Creatin
Page 111 and 112: angle valve rotary feedthrough ion
Page 113 and 114: an ion gauge controller (Granville
Page 115 and 116: viewports (MDC, 450002) are attache
Page 117 and 118: not trapped by the MOT impinge on t
Page 119 and 120: Should contamination of the vacuum
Page 121: Figure 7.12: The assembled Zeeman s
Page 125 and 126: BGauss 250 200 150 100 50 30 20 10
Page 127 and 128: are required to create the high mag
Page 129 and 130: The coils are then checked for shor
Page 131 and 132: + B A Figure 7.23: Feshbach coil H-
Page 133 and 134: ensure that no particulates build u
Page 135 and 136: 118 Figure 7.26: Optical layout of
Page 137 and 138: The error signal shows three lines,
Page 139 and 140: into the CO2 laser. The optical lay
Page 141 and 142: Thorlabs PDA10A Coupler ZDC-10-1 to
Page 143 and 144: Imaging ber Imaging ber from Imagin
Page 145 and 146: Table 7.4 summarizes the beam power
Page 147 and 148: CO2 laser 40 MHz AOM f=2 in f=2 in
Page 149 and 150: 132 Figure 7.38: Optical layout aro
Page 151 and 152: Feshbach coil objective lenses atom
Page 153 and 154: MOT beams are no longer traveling a
Page 155 and 156: The second card (NI6733) offers eig
Page 157 and 158: Averaging over the magnetic subleve
Page 159 and 160: 2 2 P 3/2 D 2=670.977nm 2 2 S 1/2 m
Page 161 and 162: The right hand side of equation 7.1
Page 163 and 164: = E0 1 −n2 √2 exp σ0 ± iE0
Page 165 and 166: esidual potentials besides gravitat
Page 167 and 168: Figure 8.1: MOT loading. Typical lo
Page 169 and 170: A linear ramp typically changes the
Page 171 and 172: A typical MOT is density-limited at
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ubidium [113-115] and cesium[116].
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that most of the noise is due to th
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(a) (c) y . x z X=0.0mm Z=2.5mm 1)
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Figure 8.11: Different shapes of MO
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ZnSe lens f=5 in knife edge ZnSe wi
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shown in figure 8.13. By matching t
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Figure 8.15: Atom number and temper
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275 Hz. Using these values the beam
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system. Maybe the easiest way to ac
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Appendix A Magic Wavelength of Hydr
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transitions for the excited state p
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Bibliography [1] J.J. Thomson. Cath
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[22] C.J. Foot. Atomic Physics. Oxf
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[46] E.D. Black. An introduction to
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[67] J.L. Hanssen. Controlling Atom
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[88] D.S. Naik, C.G. Peterson, A.G.
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[110] J.W. Goodman. Introduction to
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[132] C. Degenhardt, H. Stoehr, U.
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