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Quantum Electronics and Laser Science Conference

Trapping of francium for parity violation experiments

S. Aubin, E. Gómez, Joshua M. Grossman, L.A. Orozco, Gene D. Sprouse

Published Jun 25, 2003• 0 citations
Publisher

Abstract

Summary form only given. We have constructed a new apparatus for producing and on-line trapping of francium for parity non-conservation experiments. At present, we have produced and delivered 15 /spl times/ 10/sup 6/ Fr/sec to the trapping area with better than 90% efficiency. The electrostatic optics of our beamline ensure mass independent transport of all francium isotopes and even other alkalis, such as rubidium, which we use for testing most of our apparatus. After accumulation in this first MOT, we transfer the atoms to a second MOT in a separate vacuum chamber one meter below, where they are transferred to a far off-resonance optical dipole trap for PNC experiments. At present, we are constructing the apparatus for a measurement of the PNC anapole moment by probing the microwave E1 transition between the ground state hyperfine levels of francium.

DOI
10.1109/qels.2002.1031085

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Sviluppo di nuove tecniche per lo studio di atomi di Francio in una Trappola Magneto-Ottica

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The cooling and trapping of atoms , meaning the reduction of their average speed through the use of \nlaser techniques and their confinement in a region of a few mm3 space represents a new frontier for \nthe physics at low energies. The use of Magneto ‐ Optical Trap (MOT) for radioactive atoms allows \nthe realization of unique experiments for the study of fundamental interactions, in particular the \nstudies of Atomic Parity Non‐Conservation (APNC). This thesis presents the experimental apparatus \nused at the National Laboratories of Legnaro (LNL) of the INFN for the production and the on‐line \ntrapping of francium atoms (Fr) in a MOT. The Fr has no stable isotopes and is produced by a nuclear \nreaction, which is obtained by using Electrostatic Tandem‐XTU accelerator at LNL. The purpose of this \nline of research is the development of new techniques for trapping and detection of atoms of \nfrancium, specifically aimed at increasing the number of trapped atoms, in order to be able to make \nfuture relevant APNC measurements as a test of the Standard Model of elementary particles. The \nexperimental results achieved in the last three years (2011‐2013) will be described throughout the \nthesis, with a focus on the development of a new technique for detection of weak atomic transitions. \nThis is a direct method of investigation, based on the excitation of atoms in the MOT through a probe \nlaser beam, resonant with the transition being studied, and the detection of the transition through \nthe variations of the atomic population of the trap. Several hyperfine levels of the isotope of \nrubidium 85 have been excited by the probe beam, showing progressively lines of weaker intensity. \nThe application of this technique to radioactive atoms will allow to detect very weak transitions, such \nas those that indicate a transfer of the atoms trapped at energy levels that have not been \ninvestigated yet. The first evidence of Light‐Induced Atomic Desorption (LIAD effect) on a foil of \nyttrium, used as a neutralizer for the ionic beam of rubidium, will be presented in the thesis. It has \nbeen observed, both in the pulsed and in the continuous regimes, an increase of the MOT atomic \npopulation as a result of the desorption of the illuminated foil or the formation of the MOT when the \nyttrium foil is at room temperature and no trap is initially present. Subsequently, preliminary results \nobtained on the atomic desorption in a trap of 210Fr through a pulsed light will be shown. This \ntechnique seems to be promising to increase the atomic population of radioactive atoms traps.

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Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Dec 22, 2008•5 citations
Summary form only given. We have constructed a new apparatus for producing and on-line trapping of francium for parity non-conservation experiments. At present, we have produced and delivered 15 /spl times/ 10/sup 6/ Fr/sec to the trapping area with better than 90% efficiency. The electrostatic optics of our beamline ensure mass independent transport of all francium isotopes and even other alkalis, such as rubidium, which we use for testing most of our apparatus. After accumulation in this first MOT, we transfer the atoms to a second MOT in a separate vacuum chamber one meter below, where they are transferred to a far off-resonance optical dipole trap for PNC experiments. At present, we are constructing the apparatus for a measurement of the PNC anapole moment by probing the microwave E1 transition between the ground state hyperfine levels of francium.
Summary form only given. We have constructed a new apparatus for on-line magneto-optical trapping of radioactive francium atoms at the Stony Brook Superconducting LINAC. An ion beam with an energy of /spl sim/100 MeV from the accelerator strikes a target of gold or isotopically enriched platinum mounted on the end of a tungsten rod. A heavy-ion fusion reaction [/sup 16,18/O(/sup 197/Au,xn) or /sup 19/F(/sup 198/Pt,xn)] selectively produces the isotopes /sup 208-212/Fr in the target room of the accelerator. The beam power and an auxiliary heater heat the target, allowing the francium to diffuse rapidly to the surface. The target ionizes the francium as it diffuses out. We then transport the francium as ions to a different room for subsequent neutralization and capture in a magneto-optical trap (MOT). Since the transport system is electrostatic, it is mass independent, allowing us to transport any isotope of Fr or even other alkalis. We have delivered over 3/spl times/10/sup 6/ Fr/sec to a Faraday cup in front of the trap, and tests show greater than 90% transport efficiency from the target. A small constriction in the vacuum system separates the target and transport region from the trap, permitting differential pumping of the trap.
Francium, the heaviest alkali, is the ideal candidate for the next generation of experiments that study atomic parity non-conversion(PNC) effects or search for a CP-violating permanent atomic electric dipole moment(EDM). Since all francium isotopes are radioactive and have half-lives of 22 minutes or less, a highly efficient atom trap is needed to provide a sufficient sample for PNC or EDM experiments. Using an improved vapor cell magneto-optical trap, we have demonstrated an efficient trap of {sup 221}Fr(t{sub {1/2}}=5m) atoms. The 4cm cube cell has a geometry optimized for a high trap loading rate and its walls are coated with dryfilm to slow the loss of francium atoms to the walls. Produced from the decay of {sup 225}Ac(t{sub {1/2}}=10d), the francium atoms are efficiently transferred into the cell using a novel orthotropic oven. We have also measured the atomic hyperfine structure of the excited 7P{sub 3/2} and 7P{sub {1/2}} levels of {sup 221}Fr.
The cooling and trapping of atoms , meaning the reduction of their average speed through the use of \nlaser techniques and their confinement in a region of a few mm3 space represents a new frontier for \nthe physics at low energies. The use of Magneto ‐ Optical Trap (MOT) for radioactive atoms allows \nthe realization of unique experiments for the study of fundamental interactions, in particular the \nstudies of Atomic Parity Non‐Conservation (APNC). This thesis presents the experimental apparatus \nused at the National Laboratories of Legnaro (LNL) of the INFN for the production and the on‐line \ntrapping of francium atoms (Fr) in a MOT. The Fr has no stable isotopes and is produced by a nuclear \nreaction, which is obtained by using Electrostatic Tandem‐XTU accelerator at LNL. The purpose of this \nline of research is the development of new techniques for trapping and detection of atoms of \nfrancium, specifically aimed at increasing the number of trapped atoms, in order to be able to make \nfuture relevant APNC measurements as a test of the Standard Model of elementary particles. The \nexperimental results achieved in the last three years (2011‐2013) will be described throughout the \nthesis, with a focus on the development of a new technique for detection of weak atomic transitions. \nThis is a direct method of investigation, based on the excitation of atoms in the MOT through a probe \nlaser beam, resonant with the transition being studied, and the detection of the transition through \nthe variations of the atomic population of the trap. Several hyperfine levels of the isotope of \nrubidium 85 have been excited by the probe beam, showing progressively lines of weaker intensity. \nThe application of this technique to radioactive atoms will allow to detect very weak transitions, such \nas those that indicate a transfer of the atoms trapped at energy levels that have not been \ninvestigated yet. The first evidence of Light‐Induced Atomic Desorption (LIAD effect) on a foil of \nyttrium, used as a neutralizer for the ionic beam of rubidium, will be presented in the thesis. It has \nbeen observed, both in the pulsed and in the continuous regimes, an increase of the MOT atomic \npopulation as a result of the desorption of the illuminated foil or the formation of the MOT when the \nyttrium foil is at room temperature and no trap is initially present. Subsequently, preliminary results \nobtained on the atomic desorption in a trap of 210Fr through a pulsed light will be shown. This \ntechnique seems to be promising to increase the atomic population of radioactive atoms traps.