Experiments with Supersonic Beams as a Source of Cold Atoms

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Figure 3.13: A CAD image of the redesigned spindle. The shaft of the feedthrough is shown in black. The spindle is blue, with the clamp that tightens the collet of the spindle onto the feedthrough shaft shown in red. The rotor is silver, and the clamp that holds the rotor in the V-groove of the spindle is green. collet used in machine tool holders, and is be much more rigid, as well as being self centering. The method of clamping the rotor is also changed to a V-groove, instead of a cylindrical clamp, which is self centering and easier to machine with high accuracy. A CAD image of the new spindle can be seen in figure 3.13. Finite element calculations performed on the new spindle predict resonant frequencies well above 100 Hz, which is a significant improvement on the old spindle. With the new spindle in place, the rotor has successfully been spun up to 60 Hz without any serious resonances appearing. The large spindle holders are still in place, and the increased mass at the rotor tip means that higher speeds are deemed to be too large a risk. With the vibrational stability of the rotor improved by the new spindle, the rotor can spin at the speeds required for potential future experiments. 43
3.3.3 Detection An SRS [61] residual gas analyzer (RGA) is used to detect the beams. The experiment uses two RGAs, one to detect the slowed helium beam (RGA 200), and one which detects the beam when the rotor is out of the way (RGA 100). Both RGAs work by ionizing the helium via electron bombardment in an ionization region. The ions are then focused into a quadrupole mass spectrometer which provides mass filtering, and detected by a continuous dynode electron multiplier. The output of the electron multiplier is fed directly into a current pre-amplifier, and from there the signal is read by the data acquisition card in the computer. Because the beams are detected by ionizing the helium, the detection efficiency for helium is on the order of 10 −5 [62]. The ionization efficiency should scale with the time the atoms spend in the ionization volume, a slow beam should have a greater detection efficiency than a fast one. 3.3.4 Control Systems The experiment is controlled by a data acquisition card made by National Instruments (NI PCI-6120), run by a custom control program written in LabVIEW. The motor driving the rotor is a 380 watt Moog motor fitted with an 8000 line encoder, and is servo controlled by a Galil controller. This permits the rotational frequency of the rotor to be controlled to a few thousandths of a Hz. The servo controller is also capable of controlling the static position of the rotor to within 0.25 ◦ , and communicates with the computer control system through a serial connection. The data acquisition card also controls the timing of the experiment. The nozzle must pulse at the correct phase of the rotor’s rotation for the beam to reflect at the correct position. Figure 3.14 illustrates the method used to achieve the required phase locking between the rotor and the nozzle. The motor controller delivers a 44
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Copyright by Adam Alexander Libson
Page 3 and 4:
General Methods of Controlling Atom
Page 5 and 6:
Acknowledgments First and foremost,
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to problems, and I frequently went
Page 9 and 10: General Methods of Controlling Atom
Page 11 and 12: Table of Contents Acknowledgments v
Page 13 and 14: Chapter 5. Towards Trapping and Coo
Page 15 and 16: List of Figures 2.1 Comparison of e
Page 17 and 18: 5.12 Faraday Rotation Signal During
Page 19 and 20: producing a cold sample. Alternativ
Page 21 and 22: place inside a dilution refrigerato
Page 23 and 24: atoms or molecules are slowed using
Page 25 and 26: 2.1 Thermodynamics of Ideal Gases F
Page 27 and 28: Since there will be no heat exchang
Page 29 and 30: Using equation 2.17 to modify equat
Page 31 and 32: Normalized Effusive Beam Flux Norma
Page 33 and 34: general method for producing cold a
Page 35 and 36: The gas throughput of the nozzle ca
Page 37 and 38: Chapter 3 Slowing Supersonic Beams
Page 39 and 40: 3.1 Using Helium for Atom Optics Ex
Page 41 and 42: Figure 3.1: Calculated elastic scat
Page 43 and 44: that they can be prepared ex-situ a
Page 45 and 46: successful. Any water that remains
Page 47 and 48: Skimmer 300 l/s Turbo Pump Even-Lav
Page 49 and 50: Figure 3.5: A CAD image of the dete
Page 51 and 52: from tubular aluminum welded togeth
Page 53 and 54: Figure 3.7: A CAD image of the roto
Page 55 and 56: Figure 3.10: A CAD image of large c
Page 57 and 58: Figure 3.11: This plot shows the am
Page 59: approximations are made in this cal
Page 63 and 64: TTL pulse to the data acquisition c
Page 65 and 66: A comparison of the time-of-flight
Page 67 and 68: eceding crystal. Each curve is the
Page 69 and 70: calculated slow beam velocity is qu
Page 71 and 72: the RGA does have an effect on the
Page 73 and 74: Chapter 4 The Atomic and Molecular
Page 75 and 76: field. In the L − S coupling regi
Page 77 and 78: 3 P2 E Figure 4.2: This graph gives
Page 79 and 80: For intermediate fields, the full p
Page 81 and 82: Figure 4.4: This figure illustrates
Page 83 and 84: The same effect is also responsible
Page 85 and 86: (a) (b) (c) Time Figure 4.5: A pict
Page 87 and 88: which the particles enter). The oth
Page 89 and 90: the coil can instead be switched be
Page 91 and 92: the magnitude of the field some dis
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
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258V 1MΩ TTL 2.2mF 50Ω TTL 5V 5V
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closed. With the new thyristor gate
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HeNe M2 M1 BB /2 L BB PC coil PC PD
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Table 4.1: Peak magnetic fields mea
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Figure 4.28: A cut-away CAD image o
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ameters. The coilgun chamber consis
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Table 4.2: Final velocities (vf), s
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MCP Signal [arb. units] 2.0 1.5 (1)
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viability for molecules essential.
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8 Ω LN2 Liquid Nitrogen Dewar Nozz
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Figure 4.33: Molecular oxygen slowi
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Chapter 5 Towards Trapping and Cool
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Energy meV 0.05 0.00 0.05 0.0 0.2 0
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10 mm 2.0 T 1.8 1.6 1.4 1.2 1.0 0.8
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250V 1MΩ 3x 2.2mF TTL 5V feedback
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Magnetic Field (T) 1.9 1.7 1.5 1.3
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5.2.2.1 Principle of Operation of t
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Figure 5.8: Photograph of the trapp
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4.1.3. In an anti-Helmholtz trap, t
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Figure 5.11: Photograph of the hydr
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Photodiode Signal (V) Time (s) Figu
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Figure 5.13: Time of flight plot of
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500 l/s Turbo Pump Supersonic Nozzl
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Ionizer 500 l/s Turbo Pump Ion Opti
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guided the design of the apparatus.
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Z − Velocity (m/s) 100 60 30 0
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Atom Number 60 50 40 30 20 10 0.6 0
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scattered photon to extract informa
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where k1 · pi = − k2 · pi, wh
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the electron g-factor which causes
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Figure 5.24: A schematic of the tel
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prevent the determination of the is
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(a) (b) time Figure 5.25: A 1D illu
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experiment, where a being is capabl
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potential position 2 x 243 nm Lα |
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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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