V. Guidi

White-light laser cooling of ions in a storage ring

We propose the use of a “white laser” for laser cooling of ions in a storage ring. The use of a broad-band laser provides a radiation pressure force with wide velocity capture range and high magnitude, which is promising to improve the performance of both longitudinal and indirect transverse cooling. This wide-range force could also be suitable for direct transverse cooling of low-density beams.

Generation of a frequency comb with a sharp edge of adjustable intensity and frequency

A frequency comb is generated by successive frequency shifts of a single mode laser by an acousto-optic modulator coupled to a passive ring cavity. The cavity design and the laser-cavity coupling have a very high efficiency and allow for a perfect control of both the frequency and the intensity of the sharp edge. A second acousto-optic modulator can be used to double the comb bandwidth. The obtained spectrum is particularly suitable for laser cooling when a large velocity capture range is required as it is the case, for example, of ions confined in a storage ring.

Transverse laser cooling of ions in a storage ring

Abstract We propose a method for a direct transverse laser cooling of ions in a storage ring and we discuss its application to 7Li+ and 24Mg+ ions studied in present storage rings. The key idea consists in the use of a broad-band laser, which, impinging transversely on the ion beam to be cooled, causes phase-space compression through resonance radiation pressure. Our technique, by allowing simultaneous resonant excitation of almost all ions regardless of their velocity, compensates for the short laser-ion interaction time and gives a very large capture range.

The Legnaro francium magneto-optical trap

Laser cooling and trapping of radioactive atoms represent the new frontier in atomic physics and a new powerful tool in nuclear physics. We are setting up at the INFN-Legnaro National Laboratories a laser cooling facility that has as a first goal the realization of a 210Fr magneto-optical trap. The general outline of the experiment and the improvements of the final trap efficiency are discussed. Some preliminary results are presented.

A storage ring for crystalline beam studies

Abstract The possibility of generating crystallized ion beams, i.e. beams whose particles are located at fixed positions, has always excited the interest of most people working on particle accelerators. The reason of this interest has many aspects: knowledge either of a completely new research field or of some of the applicative potentialities, connected with crystalline beams, would justify a careful investigation of this subject. After the successful exploitation of electron cooling in several heavy ion storage rings the possibility of generating crystalline ion beams became more realistic. New cooling methods, like laser cooling, give a further opportunity to reach an ultracold system of particles necessary for the state transition to the crystalline configuration. The conceptual design of a low-energy heavy-ion storage ring, called CRYSTAL, proposed for the experimental demonstration of crystalline beams at Legnaro Laboratories is presented. The physics of crystalline beams as well as the main criteria to design a storage ring suitable to crystallize ion beams are discussed. The effects of instabilities for space charge dominated beams, shear forces in dipole magnets and lattice periodicity breaking are also discussed in detail.

Stroboscopic laser diagnostics for detection of ordering in a one-dimensional ion beam

A diagnostic method for detecting ordering in one-dimensional ion beams is presented. The ions are excited by a pulsed laser at two different positions along the beam, and fluorescence is observed by a group of four photomultipliers. Correlation in fluorescence signals is a firm indication that the ion beam has an ordered structure.

Ultrashort Laser-pulse Diagnostics for Detection of Ordering within an Ion beam.

A novel diagnostic method to detect ordering within one-dimensional ion beams in a storage ring is presented. The ions are simultaneously excited by a ultrashort pulsed laser (≃ 1 ps) at two different locations along the beam and fluorescence is detected by a group of four photomultipliers. Correlation in fluorescence signals is a firm indication that the ion beam has an ordered structure.

EXPLOSIVE EVAPORATION OF Rb OR K CLUSTERS BY LOW POWER LASER RADIATION IN THE PRESENCE OF EXCITED ATOMS

Explosive evaporation of metallic Rb or K clusters in the presence of excited atoms stimulated by resonant CW laser radiation has been observed in a glass cell. Evaporation occurs at low laser-power density. The effect consists of the generation of optically thick and sharply localized alkali vapor clouds propagating in the cell against the laser beam. The clouds are charged and exhibit a strong luminescence of Rb or K spectral lines. The explosive evaporation of metallic clusters is explained by the laser excitation of alkali atoms, which collide onto the surface of the clusters and transfer their internal energy, which thereby causes other atoms to be evaporated and to continue the avalanche process.

Laser cooling and trapping of radioactive atoms

Laser cooling and trapping techniques made possible during the last two decades important achievements in the atomic physics and quantum mechanics fields. These same techniques can be usefully applied to radioactive atoms by opening new fields of investigations. Nuclear processes can be studied with the atomic physics tools. We focused our attention on Francium radioactive atoms. A magneto-optical trap has been set up at the INFN Legnaro laboratories. Preliminary tests with other stable alkali atoms aimed at an improvement of the MOT collection efficiency are reported. Fast and efficient trap loading of rubidium has been obtained through the light-induced atomic desorption from an organic coating. A larger number of sodium atoms, as compared to monochromatic trapping laser, has been trapped by using a broad-band laser.

Development of a broadband laser in the UV region

A frequency comb in the UV region with a bandwidth greater than 100 MHz is generated by successive frequency shifts of a single mode laser by an acousto-optic modulator coupled to a passive ring cavity. The obtained spectrum is particularly suitable for laser cooling when a large velocity capture range is required as in the case, for example, of ions confined in a storage ring.