Improvement of Laser Cooling of Ions in a Penning Trap by use of the Axialisation Technique (original) (raw)
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Improvement of laser cooling of ions in a Penning trap by use of the axialization technique
Journal of Physics B: Atomic, Molecular and Optical Physics, 2003
We report a study of the axialisation and laser cooling of single ions and small clouds of ions in a Penning trap. A weak radiofrequency signal applied to a segmented ring electrode couples the magnetron motion to the cyclotron motion, which results in improved laser cooling of the magnetron motion. This allows us to approach the trapping conditions of a Paul trap, but without any micromotion. Using an ICCD camera we show that the motion of a single ion can be confined to dimensions of the order of 20 µm or less. We have measured increased magnetron cooling rates for clouds of a few ions, using an rf-photon correlation technique. For certain laser cooling conditions, the magnetron motion of the center of mass of the cloud grows and stabilises at a large value. This results in the ions orbiting the center of the trap together in a small cloud, as confirmed by photon-photon correlation measurements.
Axialization of Laser Cooled Magnesium Ions in a Penning Trap
Physical Review Letters, 2002
We report the first demonstration of the axialization of laser cooled ions in a Penning trap. Axialization involves the application of a small radial quadrupole drive which couples the cyclotron and magnetron motions. This enhances the laser cooling, allowing tighter confinement of the ions to the central axis of the trap than is otherwise possible. Using an intensified charge-coupled device (ICCD) camera we have imaged the axialization process for the first time. For a single ion, we recorded a large decrease of the magnetron amplitude corresponding to a reduction in ion temperature of approximately 2 orders of magnitude to an upper limit of order 10 mK. We have discovered dynamics specific to the laser cooled system which depend critically on the axial drive frequency and amplitude.
Journal of The Optical Society of America B-optical Physics, 2003
Trapped and laser-cooled ions are increasingly used for a variety of modern high-precision experiments, for frequency standard applications, and for quantum information processing. Therefore laser cooling of trapped ions is reviewed, the current state of the art is reported, and several new cooling techniques are outlined. The principles of ion trapping and the basic concepts of laser cooling for trapped atoms are introduced. The underlying physical mechanisms are presented, and basic experiments are briefly sketched. Particular attention is paid to recent progress by elucidating several milestone experiments. In addition, a number of special cooling techniques pertaining to trapped ions are reviewed; open questions and future research lines are indicated.
Ion dynamics in a linear radio-frequency trap with a single cooling laser
Physical Review A, 2010
We analyse the possibility of cooling ions with a single laser beam, due to the coupling between the three components of their motion induced by the Coulomb interaction. For this purpose, we numerically study the dynamics of ion clouds of up to 140 particles, trapped in a linear quadrupole potential and cooled with a laser beam propagating in the radial plane. We use Molecular Dynamics simulations and model the laser cooling by a stochastic process. For each component of the motion, we systematically study the dependence of the temperature with the anisotropy of the trapping potential. Results obtained using the full radio-frequency (rf) potential are compared to those of the corresponding pseudo-potential. In the rf case, the rotation symmetry of the potential has to be broken to keep ions inside the trap. Then, as for the pseudo-potential case, we show that the efficiency of the Coulomb coupling to thermalize the components of motion depends on the geometrical configuration of the cloud. Coulomb coupling appears to be not efficient when the ions organise as a line or a pancake and the three components of motion reach the same temperature only if the cloud extends in three dimensions.
Laser cooling of trapped ions: The influence of micromotion
Physical Review A, 1994
Laser cooling of a single trapped ion in a Paul trap is discussed theoretically in the Lamb-Dicke limit, with full consideration of the time dependence of the trapping potential. Resulting mean kinetic energies are de6ned as time averages over one period of the micromotion and are compared with 6nal temperatures expected from the laser cooling treatment with harmonic traps. For laser-atom detunings close to the micromotion frequency the results dier signi6cantly from those expected for a harmonic trap potential. A physical interpretation is given and simple formulas are derived for the strong con6nement case.
Ion trapping techniques: Laser cooling and sympathetic cooling
Intense Positron Beams …, 1988
Radiation pressure from lasers has been used to cool and compress 9Be+ ions stored in a combination of static electric and magnetic fields (Penning trap) to tem eratures less than 10 mK and densities greater than lo7 cm-q in a magnetic field of 1.4 T. A technique called sympathetic cooling can be used to transfer this cooling and compression to other ion species. ions sympathetically cooled by laser cooled 9Be+ ions is given. source vi? sympathetic cooling is also discussed. A n example of lg8Hg+ The possibility of making an ultracold positron Ion traps have been used in low energy atomic physics experiments for a period of roughly 30 years.1*2) years, however, the technique of laser cooling and compression has greatly increased the potential use of stored ions in a number of applications. One example is time and frequency standards. With the technique of laser cooling and compression, ion temperatures less than 10 mK, densities a factor of 10 less than the Brillouin limit (defined below), and essentially indefinite confinement times have been obtained. 3,4) Unfortunately, elementary charged particles (electrons, positrons, protons, etc.) can not be directly laser During the past 10
Laser-cooled ion plasmas in Penning Traps | NIST
Journal of Physics B, 2003
A laser-cooled ion plasma in a Penning trap provides a rigorous realization of a strongly coupled one-component plasma. After a brief review of the crystal structures that have been observed in Penning traps, we summarize two recent experiments. First we describe careful measurements of the stability of the plasma rotation which is controlled by a rotating electric field. We then discuss the excitation of plasma wakes produced by radiation pressure from a laser.
Doppler cooling of Ca^{+} ions in a Penning trap
Physical Review A, 2004
We have laser cooled a small cloud of 40 Ca ϩ ions stored in a Penning trap. The large Zeeman splittings that result from the presence of the imposed magnetic field necessitate the use of two cooling lasers tuned to the 2 S 1/2-2 P 1/2 transition near 397 nm ͑whereas only a single blue laser frequency is required in an rf trap͒. The 397 nm radiation is provided by a pair of blue diode lasers operated in extended cavities. Ions can escape from the cooling cycle by falling into a 2 D 3/2 state. There is also a small probability that ions can be pumped into a 2 D 5/2 state. The presence of large Zeeman splittings complicates the provision of repumper radiation to empty the D states. We describe two repumping schemes. The first scheme employs five infrared extended cavity diode lasers ͑ECDL's͒. The second scheme employs three infrared ECDL's, two of which have their injection current modulated to produce sidebands. An upper bound to the temperature of 1 K is inferred from the linewidth of the 397-nm fluorescence for a small cloud of 40 Ca ϩ ions in our Penning trap. This work is part of a program aimed at using atomic ions in a Penning trap for decoherence studies and quantum information processing.
Electron and Positron Cooling of Highly Charged Ions in a Cooler Penning Trap
2003
Electron cooling is a well-established technique to increase the phase space density of particle beams in storage rings. In this paper we discuss the feasibility of electron and positron cooling of ions in a Penning trap. We calculated the cooling times for the cases of trapped bare ions with nuclear charge Z = 1 (protons), Z = 36 (krypton) and Z = 92 (uranium) with the Spitzer formula. Our calculations show that for typical experimental conditions the time for cooling from initial energies of 10 keV per charge down to rest is in the order of a second. We investigate the dependence of the cooling time on the number of ions and electrons, and their charge and mass.