Multi frequency evaporative cooling to BEC in a high magnetic field

We demonstrate a way to circumvent the interruption of evaporative cooling observed at high bias field for $^{87}$Rb atoms trapped in the (F=2, m=+2) ground state. Our scheme uses a 3-frequencies-RF-knife achieved by mixing two RF frequencies. This compensates part of the non linearity of the Zeeman effect, allowing us to achieve BEC where standard 1-frequency-RF-knife evaporation method did not work. We are able to get efficient evaporative cooling, provided that the residual detuning between the transition and the RF frequencies in our scheme is smaller than the power broadening of the RF transitions at the end of the evaporation ramp.Comment: 12 pages, 2 figure

Atomic dynamics in evaporative cooling of trapped alkali atoms in strong magnetic fields

We investigate how the nonlinearity of the Zeeman shift for strong magnetic fields affects the dynamics of rf field induced evaporative cooling in magnetic traps. We demonstrate for the 87-Rb and 23-Na F=2 trapping states with wave packet simulations how the cooling stops when the rf field frequency goes below a certain limit (for the 85-Rb F=2 trapping state the problem does not appear). We examine the applicability of semiclassical models for the strong field case as an extension of our previous work [Phys. Rev. A 58, 3983 (1998)]. Our results verify many of the aspects observed in a recent $^{87}$Rb experiment [Phys. Rev. A 60, R1759 (1999)].Comment: 9 pages, RevTex, eps figures embedde

Double-well magnetic trap for Bose-Einstein condensates

We present a magnetic trapping scheme for neutral atoms based on a hybrid of Ioffe-Pritchard and Time-averaged Orbiting Potential traps. The resulting double-well magnetic potential has readily controllable barrier height and well separation. This offers a new tool for studying the behavior of Bose condensates in double-well potentials, including atom interferometry and Josephson tunneling. We formulate a description for the potential of this magnetic trap and discuss practical issues such as loading with atoms, evaporative cooling and manipulating the potential.Comment: 7 pages, 6 figures, Revtex

Coherent matter wave inertial sensors for precision measurements in space

We analyze the advantages of using ultra-cold coherent sources of atoms for matter-wave interferometry in space. We present a proof-of-principle experiment that is based on an analysis of the results previously published in [Richard et al., Phys. Rev. Lett., 91, 010405 (2003)] from which we extract the ratio h/m for 87Rb. This measurement shows that a limitation in accuracy arises due to atomic interactions within the Bose-Einstein condensate

GRADIOMÈTRE GRAVIFIQUE À ATOMES FROIDS

La présente invention concerne un système de gradiomètre gravifique à atomes froids comprenant une source de laser qui produit un faisceau laser qui se propage le long d'une direction de propagation. Le système comprend en outre un réflecteur qui réfléchit une partie du faisceau laser et transmet une autre partie du faisceau laser (la partie transmise). Un second réflecteur spatialement séparé su premier réflecteur le long de la direction de propagation réfléchit la partie transmise du faisceau laser

Spontaneous light scattering from propagating density fluctuations in an optical lattice

We report the observation of resonances in the intensity correlation spectra of a 3D rubidium optical lattice, which we attribute to light scattering from propagating atomic density fluctuations in the lattice. This process is the spontaneous analog of the stimulated scattering mechanism recently described by Courtois et al. [CITE]. We investigate the dependence of the new resonances on the lattice angle and show that they disappear for large angles, thus resolving previous discrepancies on the subject

Complications of laparoscopic treatment of esophageal achalasia in children

Background/Purpose: The aim of this study was to evaluate the incidence and management of the complications that occurred in some children who underwent laparoscopic Heller’s esophagocardiomyotomy in the authors’ institutions. Methods: Between March 1993 and October 1998, the files of all the children with achalasia who underwent laparoscopic Heller’s esophagocardiomyotomy in a community hospital in Naples, Italy, and a private hospital in Paris, France, were reviewed. A 5-port technique was used associating Heller’s esophagocardiomyotomy to an antireflux surgical mechanism (Dor’s or Toupet’s) in all cases. Intra- and postoperative complications, as well as the postoperative outcome, were evaluated. Results: Ten laparoscopic Heller’s esophagocardiomyotomies were performed in 5 girls and 5 boys with achalasia. Age ranged between 2 and 13 years. Mean operating time was 120 minutes. Hospital stay ranged between 3 and 41 days. Complications were recorded in 3 patients: in 2 an esophageal mucosal perforation and in 1 a prolonged dysphagia. Two of these complications occurred in the last patients operated on. Follow-up varied from 6 months to 6 years. All children were free of symptoms. Conclusions: The results show that laparoscopic Heller’s esophagocardiomyotomy in children is a feasible procedure. Assessment of mucosal integrity immediately after the myotomy must be performed. Complications can happen even if the operation is performed by expert laparoscopic surgeons

Laparoscopic esophagomyotomy for the treatment of achalasia in children: a preliminary report of eight cases

Background: Albeit rare in children, achalasia is a disorder with severe symptoms that causes growth impairment. The treatment of choice in children is the esophagomyotomy, although there are variations in the surgical approaches available and differences of opinion regarding the inclusion of an adjunctive antireflux procedure. The recent advent of the laparoscopic approach has had a profound impact on the treatment of achalasia in both adults and children. Methods: In this report, we describe eight patients with severe achalasia who were treated by laparoscopic Heller’s operation associated with a fundoplication according to either Dor’s or Toupet’s technique. The patients’ ages ranged between 2 and 13 years. A five-port technique was used: a 10-mm port placed infraumbilically for the optics and four 5-mm ports. One was placed in the right abdominal quadrant for retraction of the left hepatic lobe, one in the left abdominal quadrant for the first operative instrument, one below the xyphoid appendix for the second operative instrument, and the last one to introduce a 5-mm cannula laterally to the umbilicus to retract the stomach below. A 7–8-cm laparoscopic Heller esophagomyotomy was completed, followed by an anterior Dor fundoplication in six cases and a Toupet in two. The longitudinal division of the anterior esophageal musculature was performed with a scalpel or scissors. The myotomy was made along the stomach, extending for $2–3 cm. Results: Mean operating time was 120 mins. Three complications were recorded. There were two perforations of the gastroesophageal mucosa; the first was sutured in laparoscopy and the second required a second operation. The third complication was a case of dysphagia resolved by dismounting a fundoplication that was too tight. At follow-up, which lasted from 6 months to 5 years, the children were all free of symptoms. Conclusions: Laparoscopic Heller esophagomyotomy appears to be a complex and difficult operation, but it is as safe and effective as laparotomy in children with achalasia. However, complications can be numerous and severe at the beginning of a surgeon’s experience