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

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the same BBAR coating that is applied to the standard viewports. Figure 7.9 shows a photograph of one of the reentrant viewports. Figure 7.9: Photograph of the reentrant viewport. The size of the flange is nominally 6 in. An additional feature of the design is that it allows mounting of the Feshbach coils inside the reentrant viewports. These coils need to be mounted in Helmholtz- configuration to produce the homogeneous magnetic field for tuning the Feshbach resonance during the evaporation sequence. Because the coils can be mounted inside the reentrant viewport, both the radius of the coils and the distance between the coils can be small, thus reducing the current required to generate fields of up to 850 G. A ring of bolt holes simplifies the mounting of the Feshbach coils, see figure 7.8. Opposing the Zeeman slower port, a second 6 inch nipple, customized in our machine shop, connects to an ion pump, a titanium sublimation pump, an ion gauge and an angle valve for the initial pump-out of the vaccum chamber. The ion pump (Duniway Stockroom, RVIP-75-S) is connected through an elbow to the bottom of this 6 inch nipple. The titanium sublimation pump (Duniway Stockroom, TSP-275-003) is mounted on top of the 6 inch nipple. Along the Zeeman slower axis, a 2-3/4 inch cross connects to the ion gauge (Duniway Stockroom, I-NUDE-F with Granville Phillips Controller, 350) and an all-metal angel valve (Vat-Valve, 54032-GE02). This assembly is shown in figure 7.10. At the end of the cross, another 2-3/4 inch viewport, identical to the ones connected to the spherical octagon, seals the last vacuum port. This viewport is used by the Zeeman slower beam. The lithium atoms not slowed by the Zeeman slower or 99
not trapped by the MOT impinge on this viewport. It is therefore constantly heated to a temperatue of about 120 ◦ C with a band heater to avoid coating of the window. Both the 6 inch custom nipple and the 6 inch elbow are electropolished (Central Electropolishing Co.) to reduce outgassing in the science chamber. 7.1.4 Bake-Out Ti:Sub pump ion gauge Zeeman slower window angle valve ion pump Figure 7.10: Science chamber assembly. To achieve vacuum pressures in the 10 −10 Torr range or better, ion pumps and titanium sublimation pumps, rather than turbo-pumps, are connected to the vacuum system. This also eliminates moving pumps, reducing vibrations. However, for the initial pump-out a turbo pump is necessary. The turbo-pump is connected to the vacuum chamber through two angle valves. After bake-out these valves are closed, and the turbo-pump can be disconnected. Ultra-high vacuum pressures would be difficult to reach without baking of the chamber. Baking increases the outgassing speed, especially for water attached to the stainless steel walls of the vacuum chamber parts, thus drastically decreasing the amount of time necessary to reach the desired pressure. At pressures of 10 −6 Torr or better the baking of the chamber can start. Typically the chamber is wrapped with heater-tapes and insulated using aluminum foil. The higher the temperature during the bake-out, 100
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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
Page 65 and 66: ( ( Figure 4.3: Helicoflex seal. (a
Page 67 and 68: 88 mm 4.2.3 Auxiliary Coils 62 mm Q
Page 69 and 70: 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: viewports (MDC, 450002) are attache
Page 119 and 120: Should contamination of the vacuum
Page 121 and 122: Figure 7.12: The assembled Zeeman s
Page 123 and 124: 7.2.2 MOT Coils A second set of coi
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
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Figure 8.1: MOT loading. Typical lo
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A linear ramp typically changes the
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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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