Experiments with Supersonic Beams as a Source of Cold Atoms

More documents

Recommendations

Info

of the IGBTs used for the coilgun coil switching circuit, has to do with the “on” state behavior of these devices. In their “on” state, IGBTs behave like diodes with a relatively fixed voltage drop as a function of current. They are also susceptible to thermal runaway, as the forward voltage drop decreases with increasing temperature. This makes it difficult to place multiple IGBTs in parallel. However, the forward voltage drop will even then lead to significant losses. While MOSFETs do not have blocking voltages as high as an IGBT, they behave like a resistive load in their “on’ state, and their positive temperature co-efficient stops thermal runaway, enabling simple parallelling of multiple devices. Parallelling MOSFETs reduces the “on” state losses since the current is distributed across what is effectively many resistors in parallel, allowing the effective resistance to be reduced. For the low voltage but high current switching needed in the magnetic trapping coils, using MOSFETs enables lower losses in the switches. The final element of the circuit is a high voltage capacitor and an IGBT (Powerex CM600HA-24H) in parallel with the power supply. This part of the circuit is used to turn the coils on rapidly by briefly increasing the voltage across the circuit. This voltage boost is particularly necessary when the front coil is turned on to create an anti-Helmholtz trap. The front coil must switch on quickly to capture the atoms once they have been stopped. As the switching of the front trap coil is particularly important in the trapping sequence, the temporal switching profile is shown in figure 5.12. The profile is mea- sured by Faraday rotation with the crystal located in the middle of the front trapping coil. This shows that the front coil switches off and on linearly in 150 μs. The IGBT provides a voltage boost to shorten the switch on time (it is over 600 μs without the IGBT in the circuit). 133
Photodiode Signal (V) Time (s) Figure 5.12: The Faraday rotation signal for a crystal located in the front trapping coil during the trapping sequence. Initially, both coils are on in a Helmholtz configuration (1.11T. The front coil is then switched off (without switching the rear coil) at t =0μs. The field falls linearly over 150 μs and the coil remains off for 400 μs. At this time, the front coil is switched back on with the opposite polarity (using the IGBT boost) and the field in the center of the coil rises linearly over 150 μs to.85 T. The TGG crystal used to take this measurement is 5 mm long. 134
Page 1 and 2:
Copyright by Adam Alexander Libson
Page 3 and 4:
General Methods of Controlling Atom
Page 5 and 6:
Acknowledgments First and foremost,
Page 7 and 8:
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 and 60:
approximations are made in this cal
Page 61 and 62:
3.3.3 Detection An SRS [61] residua
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
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: Figure 5.11: Photograph of the hydr
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
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
show all

Experiments with Supersonic Beams as a Source of Cold Atoms

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?