Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

A bright source of cold atoms

Yu Lu

Published May 1, 2019• 0 citations
Publisher

Abstract

This dissertation describes a general approach of generating a high flux of cold atoms that can be confined in a magneto-optical trap. As an alternative to the state-of-the-art laser cooling method, this approach widens our ability to cool and control atoms without relying on a specific atomic transition and availability of laser. In this dissertation I will discuss the design, construction of the experiment and characterization of a pulsed cold atom source in detail. This work is based on a new paradigm: entrainment of atoms in the carrier gas of a supersonic beam, followed by the magnetic deceleration and trapping. Our methodology is based on the supersonic beam created by the expansion of a dense carrier gas from a pulsed release of gas through a small aperture. Cold noble gas emerging from this pulsed high pressure supersonic nozzle acts as a carrier, into which atoms of interest are then entrained. In our studies with the lithium atoms, up to 10¹¹ atoms per pulse could be entrained into a supersonic beam of helium at a translation temperature of below 100 mK. The supersonic valve is typically operated at a rate of below 1 Hz in the experiment. A much larger flux can be achieved at a higher repetition rate. These atoms are moving at a speed of 500 ms⁻¹ and need to be decelerated almost to a complete stop, in order to be trapped and cooled to quantum degeneracy. A 2.5-meter long moving-trap magnetic decelerator with 480 coil pairs was built and characterized. Atoms moving at a speed around 500 ms⁻¹ were trapped and decelerated to various final velocities ranging from 400 ms⁻¹ to 50 ms⁻¹, at a resulting temperature of 30 mK and a flux of 10⁸ ~ 10⁹ atoms per pulse. This whole process takes place within only 10 ms, at a repetition rate of 100 Hz 10¹⁰ ~ 10¹¹ atoms can be delivered per second. This approach is very general compared to the laser cooling, since most atoms in the periodic table have a magnetic moment in their ground state or can be optically pumped to a long-lived para-magnetic metastable state. In this dissertation, I show the working principle of each component of our experiment and characterize the atom beam at multiple stages. I describe in detail the construction and optimization of our magnetic decelerator, and demonstrate the control and monitoring system with the experiment results. Also implemented in this work is a flexible laser system that is composed of a reference diode laser and two tapered amplifiers to control and probe the internal states of atoms, as well as provide the trapping force. I also explore the optical molasses and chirped cooling techniques which help load the atoms into a magneto-optical trap. The successful demonstration of this method of creating a cold atom source leads us to believe that the magnetically decelerated supersonic atoms will play an important role in the area of cold atom physics

DOI
10.26153/tsw/2954

Related papers

A comparative study of entrainment in supersonic beams

Jan‐Karl Burkhardt

In the field of atomic physics, there is a growing demand for large numbers of dense, trapped atoms. The traditional method of generating trapped atoms is through laser cooling, however the field has reached saturation in terms of cold atom flux and phase-space density and is fundamentally limited to atoms that can be addressed using a two-level transition accessible with available lasers. Because of this a new, more general technique of generating dense clouds of trapped atoms is necessary. This technique will surpass laser cooling with higher cold atom flux and phase-space density, as well as be applicable to particles which cannot be put into a two-level system. This thesis explores the first step necessary for the generation of a new method of cooling which will be more general than laser cooling and will produce a higher cold atom flux in denser phase-space. This method of cooling will rely on the sympathetic cooling of vaporized particles with a pulsed supersonic beam before slowing the entrained particles to rest using magnetic fields. Because the cooling in the entrainment step relies on sympathetic cooling, there is no two-level requirement and thus it is applicable to all paramagnetic species including both atoms and molecules. The experiments outlined in this thesis focus on utilizing different methods of entraining vaporized atoms into a supersonic beam as an alternative method of generating cold atoms. A comprehensive comparison of entrainment efficiency using these different entrainment techniques is included as well as a discussion regarding future applications of this new cooling process.

•Jan 1, 2016•0 citations

Pulsed magnetic slowing of supersonic beams

Christian G. Parthey

Supersonic beams provide a source of cold atoms where laser cooling is not applicable. Although the atoms' temperature in the co-moving frame is in the subkelvin range their velocity is on the order of several hundreds of meters per second. This thesis describes the experimental realization of a novel method to slow atoms and molecules with permanent magnetic moments using pulsed magnetic fields. The method is suitable for most elements since most atomic species are paramagnetic, and can also be applied to certain molecules, as well as electronically excited metastable states and most radicals. We show the slowing of metastable neon in a proof of principle experiment where the mean velocity is reduced from 461.0[plus or minus] 7.7 m/s to 403 [plus or minus]16 m/s in 18 stages. A second setup with 64 stages is now operating and allows us to stop metastable neon in principle. Preliminary results showing slowing from 447[plus or minus]3m/s to 136[plus or minus]5m/s with an efficiency of up to 3.9% are included here, and the slower has been shown to generate atoms as slow as 50 m/s. We find that the slowing efficiency depends strongly on the switching phase. In addition to the experimental results described above, we present simulations of a moving trap which allows trapping and decelerating at the same time.

•Jan 1, 2017•0 citations

A moving magnetic trap decelerator: a new source of cold atoms and molecules

Etay Lavert-Ofir, Sasha Gersten, Alon Henson +4 more

We present an experimental realization of a moving magnetic trap decelerator, where paramagnetic particles entrained in a cold supersonic beam are decelerated in a co-moving magnetic trap.Our method allows for an efficient slowing down of both paramagnetic atoms and molecules to near stopping velocities.We show that under realistic conditions we will be able to trap and decelerate a large fraction of the initial supersonic beam.We present our first results on deceleration in a moving magnetic trap by bringing metastable neon atoms to near rest.Our estimated phase space volume occupied by decelerated particles at a final velocity of 50 m s -1 shows an improvement of two orders of magnitude as compared to currently available deceleration techniques.Cold chemistry (at temperature of ∼1 K) is a fast developing field with many interesting theoretical predictions yet only a few experiments [1][2][3][4].It has been predicted that in the cold chemistry regime, reactions might proceed through resonance states [5] and both reaction rate and path could be controlled [6] via external magnetic or electrostatic fields.Low-temperature chemistry is not limited to artificially created conditions alone but occurs naturally at the low temperature of interstellar space [7] and the atmospheres of remote planets and moons [8].It is anticipated that cold chemistry will follow the enormous progress in molecular chemistry that was spurred by the advent of supersonic beams more than half a century ago [9].However, the progress in experimental cold chemistry is rather slow partly due to the absence of a general method of atomic and molecular cooling.Although the low-temperature environment created within a supersonic expansion has been used to observe many reactions [10], a direct 1 Author to whom any correspondence should be addressed.

arXiv:1011.0418•New Journal of Physics•Oct 24, 2011•51 citations

Creation, trapping and manipulation of a cold argon gas

C. Maher-McWilliams

This thesis describes the construction and characterisation of a unique cold argon atom source for sympathetic cooling of molecules. Argon atoms were laser cooled from their lowest lying metastable state using the 4s[3/2]2 → 4p[5/2]3 transition at 811.5 nm. A magneto-optical trap (MOT) was used to cool the metastable argon (Ar*) atoms to 73.2 ± 0.4 μK and trap them at a density of 3.93 × 10^9 cm-3. Cooling was facilitated using an external-cavity diode laser which was frequency-stabilised to the cooling transition using a magnetic dichroism technique. This was the first application of this technique to a plasma operated at our pressures where the applied magnetic field affected the gas behaviour. The Ar* atoms in the MOT were used to demonstrate chirped optical Stark acceleration for the first time. Atoms were accelerated up to velocities of 191 ± 1 ms-1 while maintaining narrow energy spreads in the accelerated ensemble (30-100 mK). The acceleration occurred over tens of nanoseconds and on micrometre length scales. Control over the number of particles accelerated was achieved by tailoring the depth of the optical lattice potential. Monte Carlo numerical simulations of acceleration were used to fit experimental results and study the dynamics of particles over the acceleration duration. Trapping of Ar* atoms in a quasi-electrostatic trap (QUEST) has also been demonstrated. The QUEST was formed at the focus of a 100 W laser beam with a wavelength of 10.6 μm. A trap lifetime of 18.3 ± 0.3 ms was measured.

•Jan 28, 2013•1 citation

Realization of an intense cold Rb atomic beam based on a two-dimensional magneto-optical trap: Experiments and comparison with simulations

Saptarishi Chaudhuri, Sanjukta Roy, C. S. Unnikrishnan

We discuss the implementation and characterization of the source of a slow, intense, and collimated beam of rubidium atoms. The cold atomic beam is produced by two-dimensional magneto-optical trapping in directions transverse to the atomic beam axis and unbalanced Doppler cooling in the axial direction. The vacuum design allows use of relatively low laser power and a considerably simplified assembly. The atomic beam has a high flux of about $2\ifmmode\times\else\texttimes\fi{}{10}^{10}\phantom{\rule{0.3em}{0ex}}\mathrm{atoms}∕\mathrm{s}$ at a total cooling laser power of $55\phantom{\rule{0.3em}{0ex}}\mathrm{mW}$. It has a narrow longitudinal velocity distribution with mean velocity $15\phantom{\rule{0.3em}{0ex}}\mathrm{m}∕\mathrm{s}$ with full width at half maximum $3.5\phantom{\rule{0.3em}{0ex}}\mathrm{m}∕\mathrm{s}$ and has a low divergence of $26\phantom{\rule{0.3em}{0ex}}\mathrm{mrad}$. The high flux enables ultrafast loading of about ${10}^{10}$ atoms into a three-dimensional (3D) magneto-optical trap within 500 ms. The variation of the atomic beam flux was studied as a function of the rubidium vapor pressure, cooling laser power, transverse cooling laser beam length, detuning of the cooling laser, and relative intensities of the cooling beams along the atomic beam axis. We also discuss a detailed comparison of our measurements of the cold atomic beam with a 3D numerical simulation.

Physical Review A•Aug 18, 2006•63 citations

Laser cooling of a magnetically guided ultra cold atom beam

Anoush Aghajani-Talesh

This thesis examines two complimentary methods for the laser cooling of a magnetically guided ultra-cold atom beam. If combined, these methods could serve as a starting point for high-through put and possibly even continuous production of Bose-Einstein condensates. First, a mechanism is outlined to harvest ultra cold atoms from a magnetically guided atom beam into an optical dipole trap. A continuous loading scheme is described that dissipates the directed kinetic energy of a captured atom via deceleration by a magnetic potential barrier followed by optical pumping to the energetically lowest Zeeman sublevel. The application of this scheme to the transfer of ultra cold chromium atoms from a magnetically guided atom beam into a deep optical dipole trap is investigated via numerical simulations of the loading process. Based on the results of the theoretical studies the feasibility and the efficiency of our loading scheme, including the realisation of a suitable magnetic field configuration, are analysed. Second, experiments were conducted on the transverse laser cooling of a magnetically guided beam of ultra cold chromium atoms. Radial compression by a tapering of the guide is employed to adiabatically heat the beam. Inside the tapered section heat is extracted from the atom beam by a two-dimensional optical molasses perpendicular to it, resulting in a significant increase of atomic phase space density. A magnetic offset field is applied to prevent optical pumping to untrapped states. Our results demonstrate that by a suitable choice of the magnetic offset field, the cooling beam intensity and detuning, atom losses and longitudinal heating can be avoided. Final temperatures below 65 µK have been achieved, corresponding to an increase of phase space density in the guided beam by more than a factor of 30.

•Jan 1, 2014•9 citations
This dissertation describes a general approach of generating a high flux of cold atoms that can be confined in a magneto-optical trap. As an alternative to the state-of-the-art laser cooling method, this approach widens our ability to cool and control atoms without relying on a specific atomic transition and availability of laser. In this dissertation I will discuss the design, construction of the experiment and characterization of a pulsed cold atom source in detail. This work is based on a new paradigm: entrainment of atoms in the carrier gas of a supersonic beam, followed by the magnetic deceleration and trapping. Our methodology is based on the supersonic beam created by the expansion of a dense carrier gas from a pulsed release of gas through a small aperture. Cold noble gas emerging from this pulsed high pressure supersonic nozzle acts as a carrier, into which atoms of interest are then entrained. In our studies with the lithium atoms, up to 10¹¹ atoms per pulse could be entrained into a supersonic beam of helium at a translation temperature of below 100 mK. The supersonic valve is typically operated at a rate of below 1 Hz in the experiment. A much larger flux can be achieved at a higher repetition rate. These atoms are moving at a speed of 500 ms⁻¹ and need to be decelerated almost to a complete stop, in order to be trapped and cooled to quantum degeneracy. A 2.5-meter long moving-trap magnetic decelerator with 480 coil pairs was built and characterized. Atoms moving at a speed around 500 ms⁻¹ were trapped and decelerated to various final velocities ranging from 400 ms⁻¹ to 50 ms⁻¹, at a resulting temperature of 30 mK and a flux of 10⁸ ~ 10⁹ atoms per pulse. This whole process takes place within only 10 ms, at a repetition rate of 100 Hz 10¹⁰ ~ 10¹¹ atoms can be delivered per second. This approach is very general compared to the laser cooling, since most atoms in the periodic table have a magnetic moment in their ground state or can be optically pumped to a long-lived para-magnetic metastable state. In this dissertation, I show the working principle of each component of our experiment and characterize the atom beam at multiple stages. I describe in detail the construction and optimization of our magnetic decelerator, and demonstrate the control and monitoring system with the experiment results. Also implemented in this work is a flexible laser system that is composed of a reference diode laser and two tapered amplifiers to control and probe the internal states of atoms, as well as provide the trapping force. I also explore the optical molasses and chirped cooling techniques which help load the atoms into a magneto-optical trap. The successful demonstration of this method of creating a cold atom source leads us to believe that the magnetically decelerated supersonic atoms will play an important role in the area of cold atom physics
In the field of atomic physics, there is a growing demand for large numbers of dense, trapped atoms. The traditional method of generating trapped atoms is through laser cooling, however the field has reached saturation in terms of cold atom flux and phase-space density and is fundamentally limited to atoms that can be addressed using a two-level transition accessible with available lasers. Because of this a new, more general technique of generating dense clouds of trapped atoms is necessary. This technique will surpass laser cooling with higher cold atom flux and phase-space density, as well as be applicable to particles which cannot be put into a two-level system. This thesis explores the first step necessary for the generation of a new method of cooling which will be more general than laser cooling and will produce a higher cold atom flux in denser phase-space. This method of cooling will rely on the sympathetic cooling of vaporized particles with a pulsed supersonic beam before slowing the entrained particles to rest using magnetic fields. Because the cooling in the entrainment step relies on sympathetic cooling, there is no two-level requirement and thus it is applicable to all paramagnetic species including both atoms and molecules. The experiments outlined in this thesis focus on utilizing different methods of entraining vaporized atoms into a supersonic beam as an alternative method of generating cold atoms. A comprehensive comparison of entrainment efficiency using these different entrainment techniques is included as well as a discussion regarding future applications of this new cooling process.
Supersonic beams provide a source of cold atoms where laser cooling is not applicable. Although the atoms' temperature in the co-moving frame is in the subkelvin range their velocity is on the order of several hundreds of meters per second. This thesis describes the experimental realization of a novel method to slow atoms and molecules with permanent magnetic moments using pulsed magnetic fields. The method is suitable for most elements since most atomic species are paramagnetic, and can also be applied to certain molecules, as well as electronically excited metastable states and most radicals. We show the slowing of metastable neon in a proof of principle experiment where the mean velocity is reduced from 461.0[plus or minus] 7.7 m/s to 403 [plus or minus]16 m/s in 18 stages. A second setup with 64 stages is now operating and allows us to stop metastable neon in principle. Preliminary results showing slowing from 447[plus or minus]3m/s to 136[plus or minus]5m/s with an efficiency of up to 3.9% are included here, and the slower has been shown to generate atoms as slow as 50 m/s. We find that the slowing efficiency depends strongly on the switching phase. In addition to the experimental results described above, we present simulations of a moving trap which allows trapping and decelerating at the same time.
We present an experimental realization of a moving magnetic trap decelerator, where paramagnetic particles entrained in a cold supersonic beam are decelerated in a co-moving magnetic trap.Our method allows for an efficient slowing down of both paramagnetic atoms and molecules to near stopping velocities.We show that under realistic conditions we will be able to trap and decelerate a large fraction of the initial supersonic beam.We present our first results on deceleration in a moving magnetic trap by bringing metastable neon atoms to near rest.Our estimated phase space volume occupied by decelerated particles at a final velocity of 50 m s -1 shows an improvement of two orders of magnitude as compared to currently available deceleration techniques.Cold chemistry (at temperature of ∼1 K) is a fast developing field with many interesting theoretical predictions yet only a few experiments [1][2][3][4].It has been predicted that in the cold chemistry regime, reactions might proceed through resonance states [5] and both reaction rate and path could be controlled [6] via external magnetic or electrostatic fields.Low-temperature chemistry is not limited to artificially created conditions alone but occurs naturally at the low temperature of interstellar space [7] and the atmospheres of remote planets and moons [8].It is anticipated that cold chemistry will follow the enormous progress in molecular chemistry that was spurred by the advent of supersonic beams more than half a century ago [9].However, the progress in experimental cold chemistry is rather slow partly due to the absence of a general method of atomic and molecular cooling.Although the low-temperature environment created within a supersonic expansion has been used to observe many reactions [10], a direct 1 Author to whom any correspondence should be addressed.
This thesis describes the construction and characterisation of a unique cold argon atom source for sympathetic cooling of molecules. Argon atoms were laser cooled from their lowest lying metastable state using the 4s[3/2]2 → 4p[5/2]3 transition at 811.5 nm. A magneto-optical trap (MOT) was used to cool the metastable argon (Ar*) atoms to 73.2 ± 0.4 μK and trap them at a density of 3.93 × 10^9 cm-3. Cooling was facilitated using an external-cavity diode laser which was frequency-stabilised to the cooling transition using a magnetic dichroism technique. This was the first application of this technique to a plasma operated at our pressures where the applied magnetic field affected the gas behaviour. The Ar* atoms in the MOT were used to demonstrate chirped optical Stark acceleration for the first time. Atoms were accelerated up to velocities of 191 ± 1 ms-1 while maintaining narrow energy spreads in the accelerated ensemble (30-100 mK). The acceleration occurred over tens of nanoseconds and on micrometre length scales. Control over the number of particles accelerated was achieved by tailoring the depth of the optical lattice potential. Monte Carlo numerical simulations of acceleration were used to fit experimental results and study the dynamics of particles over the acceleration duration. Trapping of Ar* atoms in a quasi-electrostatic trap (QUEST) has also been demonstrated. The QUEST was formed at the focus of a 100 W laser beam with a wavelength of 10.6 μm. A trap lifetime of 18.3 ± 0.3 ms was measured.
We discuss the implementation and characterization of the source of a slow, intense, and collimated beam of rubidium atoms. The cold atomic beam is produced by two-dimensional magneto-optical trapping in directions transverse to the atomic beam axis and unbalanced Doppler cooling in the axial direction. The vacuum design allows use of relatively low laser power and a considerably simplified assembly. The atomic beam has a high flux of about $2\ifmmode\times\else\texttimes\fi{}{10}^{10}\phantom{\rule{0.3em}{0ex}}\mathrm{atoms}∕\mathrm{s}$ at a total cooling laser power of 55mW55\phantom{\rule{0.3em}{0ex}}\mathrm{mW}55mW. It has a narrow longitudinal velocity distribution with mean velocity 15m∕s15\phantom{\rule{0.3em}{0ex}}\mathrm{m}∕\mathrm{s}15m∕s with full width at half maximum 3.5m∕s3.5\phantom{\rule{0.3em}{0ex}}\mathrm{m}∕\mathrm{s}3.5m∕s and has a low divergence of 26mrad26\phantom{\rule{0.3em}{0ex}}\mathrm{mrad}26mrad. The high flux enables ultrafast loading of about 1010{10}^{10}1010 atoms into a three-dimensional (3D) magneto-optical trap within 500 ms. The variation of the atomic beam flux was studied as a function of the rubidium vapor pressure, cooling laser power, transverse cooling laser beam length, detuning of the cooling laser, and relative intensities of the cooling beams along the atomic beam axis. We also discuss a detailed comparison of our measurements of the cold atomic beam with a 3D numerical simulation.
This thesis examines two complimentary methods for the laser cooling of a magnetically guided ultra-cold atom beam. If combined, these methods could serve as a starting point for high-through put and possibly even continuous production of Bose-Einstein condensates. First, a mechanism is outlined to harvest ultra cold atoms from a magnetically guided atom beam into an optical dipole trap. A continuous loading scheme is described that dissipates the directed kinetic energy of a captured atom via deceleration by a magnetic potential barrier followed by optical pumping to the energetically lowest Zeeman sublevel. The application of this scheme to the transfer of ultra cold chromium atoms from a magnetically guided atom beam into a deep optical dipole trap is investigated via numerical simulations of the loading process. Based on the results of the theoretical studies the feasibility and the efficiency of our loading scheme, including the realisation of a suitable magnetic field configuration, are analysed. Second, experiments were conducted on the transverse laser cooling of a magnetically guided beam of ultra cold chromium atoms. Radial compression by a tapering of the guide is employed to adiabatically heat the beam. Inside the tapered section heat is extracted from the atom beam by a two-dimensional optical molasses perpendicular to it, resulting in a significant increase of atomic phase space density. A magnetic offset field is applied to prevent optical pumping to untrapped states. Our results demonstrate that by a suitable choice of the magnetic offset field, the cooling beam intensity and detuning, atom losses and longitudinal heating can be avoided. Final temperatures below 65 µK have been achieved, corresponding to an increase of phase space density in the guided beam by more than a factor of 30.