AIP conference proceedings

Beam dynamics and laser cooling of stored ions

Martin Kristensen, Jørgen S. Nielsen, Shi Peixiong, Ove Poulsen, Jeffrey Scott Hangst

Published Jan 1, 1993• 1 citation

Abstract

The storage ring ASTRID is built for studies in atomic physics, collision physics and laser physics. Beams have been laser cooled to temperature below 1 mK and beam dynamics studied by laser spectroscopy. The role of transverse excitations has been investigated and parameters determining onset of condensation studied. Rf‐laser double resonance spectroscopy has been performed and strict limits put on the requirements for coherent Ramsey‐spectroscopy.

DOI: 10.1063/1.43776

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AIP conference proceedings

Beam dynamics and laser cooling of stored ions

Martin Kristensen, Jørgen S. Nielsen, Shi Peixiong, Ove Poulsen, Jeffrey Scott Hangst

Published Jan 1, 1993• 1 citation

Publisher

Abstract

DOI: 10.1063/1.43776

Related papers

Laser cooling of {sup 24}Mg{sup +} in the ASTRID storage ring

J. S. Nielsen, Jeffrey Scott Hangst, Ove Poulsen +3 more

May 1, 19940 citations

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Kazuya Osaki, H. Okamoto

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Jeff S. Hangst, M. Kristensen, J. S. Nielsen +3 more

The interaction of laser-induced and intrabeam forces has been studied in a dense stored beam of 100-keV $^{7}\mathrm{Li}^{+}$ ions. A fraction of the ions (\ensuremath{\sim}${10}^{\mathrm{\ensuremath{-}}4}$) exist in the metastable 1s2s $^{3}$ S state. Using this state as a laser spectroscopic probe, we observe fast longitudinal heating in the injected, nonequilibrium distribution due to Coulomb scattering. Laser cooling of the metastable ions is ineffective during this heating period. The metastable fraction of the equilibrated beam is subsequently laser cooled to a longitudinal temperature of \ensuremath{\sim}1 mK, the lowest temperature ever reported in a stored ion beam.The interaction of laser-induced and intrabeam forces has been studied in a dense stored beam of 100-keV $^{7}\mathrm{Li}^{+}$ ions. A fraction of the ions (\ensuremath{\sim}${10}^{\mathrm{\ensuremath{-}}4}$) exist in the metastable 1s2s $^{3}$S state. Using this state as a laser spectroscopic probe, we observe fast longitudinal heating in the injected, nonequilibrium distribution due to Coulomb scattering. Laser cooling of the metastable ions is ineffective during this heating period. The metastable fraction of the equilibrated beam is subsequently laser cooled to a longitudinal temperature of \ensuremath{\sim}1 mK, the lowest temperature ever reported in a stored ion beam.

Physical Review LettersSep 2, 1991115 citations

-

|42 MHz and 1.5 mm, respectively, for the most efficient cooling of 40 keV |

^{24}

|Mg|

^+

| beams in S-LSR. Under the optimum conditions, the use of the resonant coupling method followed by radio-frequency field ramping enables us to reach an extremely low beam temperature on the order of 0.1 K in the transverse degrees of freedom. The longitudinal degree of freedom can be cooled to close to the Doppler limit; i.e., to the mK range. We also numerically demonstrate that it is possible to establish a stable, long one-dimensionally ordered state of ions.

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

beam with an initial longitudinal temperature of 2700 K, the main characteristics of laser cooling in a storage ring are discussed. When undamped, the transverse betatron oscillations of the coasting ions limit the longitudinal temperature after laser cooling to typically 1 K. After damping the transverse motion by precooling the ions with an electron cooler, longitudinal temperatures of below 30 mK have been obtained in the subsequent laser cooling. In this case, the longitudinal ion-beam temperature can be understood as an equilibrium of the laser cooling rate with the heating rate due to intrabeam scattering. Moreover, single binary Coulomb collisions between the (still transversely hot) ions can cause such longitudinal velocity changes that ions are lost out of the critical capture range of the laser cooling force. In these two ways, intrabeam scattering imposes a substantial limit on the temperature or number of laser cooled ions in a storage ring. In our experiments, this process presently limits the ratio between the density-dependent Coulomb energy and the longitudinal thermal energy spread to a value on the order of 1, where liquid rather than gaseous behavior of the ion beam is expected to set in.

We observed phase transitions and ordered structures of laser-cooled

{\mathrm{Mg}}^{+}

ions stored in a radio-frequency quadrupole storage ring with a diameter of 115 mm. The ions are confined two dimensionally by a quadrupole field and can move freely along the ring circumference. By cooling the ions with tangentially intersecting laser beams, we observed a linear string of ions aligned along the center line of the quadrupole field. For higher ion densities the linear structure changes into a helical structure. The dynamics of the stored ions was studied.

The interaction of laser-induced and intrabeam forces has been studied in a dense stored beam of 100-keV

^{7}\mathrm{Li}^{+}

ions. A fraction of the ions (\ensuremath{\sim}${10}^{\mathrm{\ensuremath{-}}4}$) exist in the metastable 1s2s

^{3}

S state. Using this state as a laser spectroscopic probe, we observe fast longitudinal heating in the injected, nonequilibrium distribution due to Coulomb scattering. Laser cooling of the metastable ions is ineffective during this heating period. The metastable fraction of the equilibrated beam is subsequently laser cooled to a longitudinal temperature of \ensuremath{\sim}1 mK, the lowest temperature ever reported in a stored ion beam.