Light desorption from an yttrium neutralizer for Rb and Fr magneto-optical trap loading

We present here the first evidence of photodesorption induced by low-intensity non-resonant light from an yttrium thin foil, which works as a neutralizer for Rb and Fr ions beam. Neutral atoms are suddenly ejected from the metal surface in a pulsed regime upon illumination with a broadband flash light and then released in the free volume of a pyrex cells. Here atoms are captured by a Magneto-Optical Trap (MOT), which is effectively loaded by the photodesorption. Loading times of the order of the flash rise time are measured. Desorption is also obtained in the continuous regime, by exploiting CW visible illumination of the metallic neutralizer surface. We demonstrate that at lower CW light intensities vacuum conditions are not perturbed by the photodesorption and hence the MOT dynamics remains unaffected, while the trap population increases thanks to the incoming desorbed atoms flux. Even with the Y foil at room temperature and hence with no trapped atoms, upon visible illumination, the number of trapped atoms reaches 10(5). The experimental data are then analyzed by means of an analytical rate equation model, which allows the analysis of this phenomenon and its dynamics and allows the determination of critical experimental parameters and the test of the procedure in the framework of radioactive Francium trapping. In this view, together with an extensive investigation of the phenomenon with Rb-85, the first demonstration of the photodesorption-aided loading of a Fr-210 MOT is shown. (C) 2014 AIP Publishing LLC

Light desorption from an Yttrium neutralizer for Rb and Fr MOT loading

We present here the first evidence of photodesorption induced by low-intensity non-resonant light from an yttrium thin foil, which works as a neutralizer for Rb and Fr ions beam. Neutral atoms are suddenly ejected from the metal surface in a pulsed regime upon illumination with a broadband flash light and then released in the free volume of a pyrex cells. Here atoms are captured by a Magneto-Optical Trap (MOT), which is effectively loaded by the photodesorption. Loading times of the order of the flash rise time are measured. Desorption is also obtained in the continuous regime, by exploiting CW visible illumination of the metallic neutralizer surface. We demonstrate that at lower CW light intensities vacuum conditions are not perturbed by the photodesorption and hence the MOT dynamics remains unaffected, while the trap population increases thanks to the incoming desorbed atoms flux. Even with the Y foil at room temperature and hence with no trapped atoms, upon visible illumination, the number of trapped atoms reaches 10(5). The experimental data are then analyzed by means of an analytical rate equation model, which allows the analysis of this phenomenon and its dynamics and allows the determination of critical experimental parameters and the test of the procedure in the framework of radioactive Francium trapping. In this view, together with an extensive investigation of the phenomenon with Rb-85, the first demonstration of the photodesorption-aided loading of a Fr-210 MOT is shown

La Grande Nation and Agriculture: The Power of French Farmers Demystified

Contains fulltext : 111782.pdf (publisher's version ) (Closed access)France is considered a strong state, but French governments have always fiercely defended the interests of French farmers in European and global negotiations. Why would a ‘strong state’ be unable to resist farm lobby pressure? Is agriculture an exception to the French ‘strong state’ rule? This article offers a structural model of varying state sensitivity to interest group pressure, and argues that farm lobby pressure cannot fully explain French foreign policy on agriculture, as governments often go against farmers' preferences and as the level of pressure varies more than the continuity of governmental preferences. From an analysis of the negotiations on the CAP and the GATT in the 1960s and in the 1990s it emerges that ideational constraints played a major role in French obstinacy. The defence of French identity as La Grande Nation, necessitating a presence in world agricultural markets, and the defence of a strong Europe under French leadership as a counterweight to the United States, have guided French preferences without regard to the farmers' positions.20 p