Physical Review Letters

Sympathetic cooling of trapped ions: A laser-cooled two-species nonneutral ion plasma

Daniel J. Larson, Jonas Bergquist, J. J. Bollinger, Wayne M. Itano, David J. Wineland

Published Jul 7, 1986• 375 citations

Abstract

Sympathetic cooling of trapped ions has been demonstrated in an experiment where $^{198}\mathrm{Hg}^{+}$ ions were confined in a Penning ion trap with laser-cooled $^{9}\mathrm{Be}^{+}$ ions. $^{198}\mathrm{Hg}^{+}$ temperatures below 1 K were achieved. Ion plasma sizes, shapes, and rotation frequencies were measured. Dramatic changes in the $^{9}\mathrm{Be}^{+}$ plasma were observed when the $^{198}\mathrm{Hg}^{+}$ ions were introduced into the trap. These observations are consistent with the prediction of centrifugal separation for ions of different charge-to-mass ratios.

DOI: 10.1103/physrevlett.57.70

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Sympathetic cooling in two-species ion crystals in a Penning trap

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Ion trapping techniques: laser cooling and sympathetic cooling

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Physical Review Letters

Sympathetic cooling of trapped ions: A laser-cooled two-species nonneutral ion plasma

Daniel J. Larson, Jonas Bergquist, J. J. Bollinger, Wayne M. Itano, David J. Wineland

Published Jul 7, 1986• 375 citations

Publisher

Abstract

Sympathetic cooling of trapped ions has been demonstrated in an experiment where

^{198}\mathrm{Hg}^{+}

ions were confined in a Penning ion trap with laser-cooled

^{9}\mathrm{Be}^{+}

ions.

^{198}\mathrm{Hg}^{+}

temperatures below 1 K were achieved. Ion plasma sizes, shapes, and rotation frequencies were measured. Dramatic changes in the

^{9}\mathrm{Be}^{+}

plasma were observed when the

^{198}\mathrm{Hg}^{+}

ions were introduced into the trap. These observations are consistent with the prediction of centrifugal separation for ions of different charge-to-mass ratios.

DOI: 10.1103/physrevlett.57.70

Related papers

Sympathetic cooling in two-species ion crystals in a Penning trap

S. Schmidt, T. Murböck, Zoran Andelkovic +5 more

We have studied the formation and properties of two-species ion Coulomb crystals in the Penning trap of the SpecTrap experiment. These crystals have been formed by injection of admixture ions from an external source into a previously confined and laser-cooled cloud of magnesium ions. This kind of study, performed over a range of the admixture ions’ charge-to-mass ratios, indicates the conditions for their sympathetic cooling and the formation of two-species ion crystals. This mechanism allows efficient cooling of the admixed species such as highly charged ions which do not feature suitable laser-cooling transitions, and thus make them accessible to high-resolution laser spectroscopy.We have studied the formation and properties of two-species ion Coulomb crystals in the Penning trap of the SpecTrap experiment. These crystals have been formed by injection of admixture ions from an external source into a previously confined and laser-cooled cloud of magnesium ions. This kind of study, performed over a range of the admixture ions’ charge-to-mass ratios, indicates the conditions for their sympathetic cooling and the formation of two-species ion crystals. This mechanism allows efficient cooling of the admixed species such as highly charged ions which do not feature suitable laser-cooling transitions, and thus make them accessible to high-resolution laser spectroscopy.

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Natural ${\mathrm{Cd}}^{+}$ ions in a Penning trap are cooled sympathetically below 1 K by a Coulomb interaction with directly laser-cooled ${\mathrm{Be}}^{+}$ ions. Spatial separation of the ${\mathrm{Be}}^{+}$ and ${\mathrm{Cd}}^{+}$ ion clouds due to centrifugal force is observed directly. When the frequency of rotation of the ion clouds is accelerated, the separation between ${\mathrm{Cd}}^{+}$ -ion isotopes (A=110 and 116) can be clearly observed, though their mass difference is very small. The equations of motion for 100 ${\mathrm{Be}}^{+}$ ions and 50 ${\mathrm{Cd}}^{+}$ ions are solved to simulate the experiments, and the result shows the spatial separation between the two ion species. The separation between the ${\mathrm{Cd}}^{+}$ -ion isotopes is investigated by comparing the experimental results with numerical calculations.Natural ${\mathrm{Cd}}^{+}$ ions in a Penning trap are cooled sympathetically below 1 K by a Coulomb interaction with directly laser-cooled ${\mathrm{Be}}^{+}$ ions. Spatial separation of the ${\mathrm{Be}}^{+}$ and ${\mathrm{Cd}}^{+}$ ion clouds due to centrifugal force is observed directly. When the frequency of rotation of the ion clouds is accelerated, the separation between ${\mathrm{Cd}}^{+}$ -ion isotopes (A=110 and 116) can be clearly observed, though their mass difference is very small. The equations of motion for 100 ${\mathrm{Be}}^{+}$ ions and 50 ${\mathrm{Cd}}^{+}$ ions are solved to simulate the experiments, and the result shows the spatial separation between the two ion species. The separation between the ${\mathrm{Cd}}^{+}$ -ion isotopes is investigated by comparing the experimental results with numerical calculations.

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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 10Radiation 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

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Sympathetic cooling and detection of molecular ions in a Penning trap

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We have trapped and sympathetically cooled the molecular ions ${\mathrm{HCO}}^{+}$ and ${\mathrm{N}}_{2}{\mathrm{H}}^{+}$ in a Penning trap. Through their Coulomb interaction with laser-cooled ${\mathrm{Mg}}^{+}$ ions the molecules were sympathetically cooled to cryogenic temperatures. We identify the molecules through a measurement of their characteristic mass-dependent breathing mode frequencies. From a measurement of the temperature of the ${\mathrm{Mg}}^{+}$ ions we estimate that the final temperature of the sympathetically cooled molecules is 4 K.We have trapped and sympathetically cooled the molecular ions ${\mathrm{HCO}}^{+}$ and ${\mathrm{N}}_{2}{\mathrm{H}}^{+}$ in a Penning trap. Through their Coulomb interaction with laser-cooled ${\mathrm{Mg}}^{+}$ ions the molecules were sympathetically cooled to cryogenic temperatures. We identify the molecules through a measurement of their characteristic mass-dependent breathing mode frequencies. From a measurement of the temperature of the ${\mathrm{Mg}}^{+}$ ions we estimate that the final temperature of the sympathetically cooled molecules is 4 K.

Physical Review ANov 1, 199944 citations

Laser cooling of externally produced Mg ions in a Penning trap for sympathetic cooling of highly charged ions

Zoran Andelkovic, Radu Cazan, W. Nörtershäuser +7 more

We have performed laser cooling of Mg ${}^{+}$ ions confined in a Penning trap. The externally produced ions were captured in flight, stored, and laser cooled. Laser-induced fluorescence was observed perpendicular to the cooling laser axis. Optical detection down to the single-ion level together with the electronic detection of the ion oscillations inside the Penning trap have been used to acquire information on the ion storage time, ion number, and ion temperature. Evidence for the formation of ion crystals has been observed. These investigations are an important prerequisite for the sympathetic cooling of simultaneously stored highly charged ions and the precision laser spectroscopy of forbidden transitions in these.We have performed laser cooling of Mg${}^{+}$ ions confined in a Penning trap. The externally produced ions were captured in flight, stored, and laser cooled. Laser-induced fluorescence was observed perpendicular to the cooling laser axis. Optical detection down to the single-ion level together with the electronic detection of the ion oscillations inside the Penning trap have been used to acquire information on the ion storage time, ion number, and ion temperature. Evidence for the formation of ion crystals has been observed. These investigations are an important prerequisite for the sympathetic cooling of simultaneously stored highly charged ions and the precision laser spectroscopy of forbidden transitions in these.

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Sympathetic cooling of mixed-species two-ion crystals for precision spectroscopy

Jannes B. Wübbena, Sana Amairi‐Pyka, Olaf Mandel +1 more

Sympathetic cooling of trapped ions has become an indispensable tool for quantum-information processing and precision spectroscopy. In the simplest situation a single Doppler-cooled ion sympathetically cools another ion which typically has a different mass. We analytically investigate the effect of the mass ratio of such an ion crystal on the achievable temperature limit in the presence of external heating. As an example, we show that cooling of a single Al ${}^{+}$ with Be ${}^{+}$ , Mg ${}^{+}$ , and Ca ${}^{+}$ ions provides similar results for heating rates typically observed in ion traps, whereas cooling ions with a larger mass perform worse. Furthermore, we present numerical simulation results of the rethermalization dynamics after a background gas collision for the Al ${}^{+}$ -Ca ${}^{+}$ crystal for different cooling laser configurations.Sympathetic cooling of trapped ions has become an indispensable tool for quantum-information processing and precision spectroscopy. In the simplest situation a single Doppler-cooled ion sympathetically cools another ion which typically has a different mass. We analytically investigate the effect of the mass ratio of such an ion crystal on the achievable temperature limit in the presence of external heating. As an example, we show that cooling of a single Al${}^{+}$ with Be${}^{+}$, Mg${}^{+}$, and Ca${}^{+}$ ions provides similar results for heating rates typically observed in ion traps, whereas cooling ions with a larger mass perform worse. Furthermore, we present numerical simulation results of the rethermalization dynamics after a background gas collision for the Al${}^{+}$-Ca${}^{+}$ crystal for different cooling laser configurations.

arXiv:1202.2730Physical Review AApr 13, 201299 citations

Sympathetic cooling of trapped ions has been demonstrated in an experiment where

^{198}\mathrm{Hg}^{+}

ions were confined in a Penning ion trap with laser-cooled

^{9}\mathrm{Be}^{+}

ions.

^{198}\mathrm{Hg}^{+}

temperatures below 1 K were achieved. Ion plasma sizes, shapes, and rotation frequencies were measured. Dramatic changes in the

^{9}\mathrm{Be}^{+}

plasma were observed when the

^{198}\mathrm{Hg}^{+}

ions were introduced into the trap. These observations are consistent with the prediction of centrifugal separation for ions of different charge-to-mass ratios.

Natural

{\mathrm{Cd}}^{+}

ions in a Penning trap are cooled sympathetically below 1 K by a Coulomb interaction with directly laser-cooled

{\mathrm{Be}}^{+}

ions. Spatial separation of the

{\mathrm{Be}}^{+}

and

{\mathrm{Cd}}^{+}

ion clouds due to centrifugal force is observed directly. When the frequency of rotation of the ion clouds is accelerated, the separation between

{\mathrm{Cd}}^{+}

-ion isotopes (A=110 and 116) can be clearly observed, though their mass difference is very small. The equations of motion for 100

{\mathrm{Be}}^{+}

ions and 50

{\mathrm{Cd}}^{+}

ions are solved to simulate the experiments, and the result shows the spatial separation between the two ion species. The separation between the

{\mathrm{Cd}}^{+}

-ion isotopes is investigated by comparing the experimental results with numerical calculations.

We have trapped and sympathetically cooled the molecular ions

{\mathrm{HCO}}^{+}

and

{\mathrm{N}}_{2}{\mathrm{H}}^{+}

in a Penning trap. Through their Coulomb interaction with laser-cooled

{\mathrm{Mg}}^{+}

ions the molecules were sympathetically cooled to cryogenic temperatures. We identify the molecules through a measurement of their characteristic mass-dependent breathing mode frequencies. From a measurement of the temperature of the

{\mathrm{Mg}}^{+}

ions we estimate that the final temperature of the sympathetically cooled molecules is 4 K.

We have performed laser cooling of Mg

{}^{+}

ions confined in a Penning trap. The externally produced ions were captured in flight, stored, and laser cooled. Laser-induced fluorescence was observed perpendicular to the cooling laser axis. Optical detection down to the single-ion level together with the electronic detection of the ion oscillations inside the Penning trap have been used to acquire information on the ion storage time, ion number, and ion temperature. Evidence for the formation of ion crystals has been observed. These investigations are an important prerequisite for the sympathetic cooling of simultaneously stored highly charged ions and the precision laser spectroscopy of forbidden transitions in these.

{}^{+}

with Be

{}^{+}

, Mg

{}^{+}

, and Ca

{}^{+}

ions provides similar results for heating rates typically observed in ion traps, whereas cooling ions with a larger mass perform worse. Furthermore, we present numerical simulation results of the rethermalization dynamics after a background gas collision for the Al

{}^{+}

-Ca

{}^{+}

crystal for different cooling laser configurations.