P. Juncar

The BNM Watt balance project

A new watt balance project is now developed by the BNM: the general configuration and the main parts of the experimental set-up in development are presented. Its aim is to contribute to the international effort in monitoring the kilogram towards a new definition of the mass unit with an accuracy of 10-8 or better

Hyperfine structures and isotope shifts of 207–213,220–228Fr; Possible evidence of octupolar deformation

Abstract Hyperfine structures and isotope shifts of 207–213,220–228 Fr have been measured by high-resolution laser spectroscopy. Nuclear moments and changes in the mean-square charge radii are deduced. They are compared with analogous data for radium and discussed in terms of the octupole deformation mode.

Isotope shifts, spins and hyperfine structures of 118,146Cs and of some francium isotopes

Abstract High-resolution laser spectroscopy using thermal atomic beams has been performed on-line with the ISOLDE facility at CERN. It allowed the measurement of the spins, isotope shifts and hyperfine structures of the D2 line of 118,146Cs, and that of the hyperfine factors of the first P 1 2 level of 133,135,137,139,141,143Cs and 210,212,213,221Fr. Previous data concerning 207–213,220–228Fr have also been reanalysed. All results are discussed in terms of deformations with special attention to the possible occurrence of octupole deformations.

Heterodyne interferometric technique for displacement control at the nanometric scale

We propose a method of displacement control that addresses the measurement requirements of the nanotechnology community and provide a traceability to the definition of the meter at the nanometric scale. The method is based on the use of both a heterodyne Michelson’s interferometer and a homemade high frequency electronic circuit. The system so established allows us to control the displacement of a translation stage with a known step of 4.945 nm. Intrinsic relative uncertainty on the step value is 1.6×10−9. Controls of the period of repetition of these steps with a high-stability quartz oscillator permits to impose an uniform speed to the translation stage with the same accuracy. This property will be used for the watt balance project of the Bureau National de Metrologie of France.

Refractometer for tracking changes in the refractive index of air near 780 nm.

A new system, consisting of a double-channel Fabry-Perot etalon and laser diodes emitting around 780 nm, is described and proposed for use for measuring air-refractive index. The principle of this refractometer is based on frequency measurements between optical laser sources. It permits quasi-instantaneous measurement with a resolution of better than 10(-9) and uncertainty in the 10(-8) range. Some preliminary results on the stability of this system and the measurements of the refractive index of air with this apparatus are presented. The first measurements of the index of air at 780 nm are, within an experimental uncertainty of the order of 2 x 10(-8), in agreement with the predicted values by the so-called revised Edlén equations. This result is, to the best of our knowledge, the first to extend to the near IR the validity of the revised Edlén equation derived for the wavelength range of 350-650 nm.

A 2D nano-positioning system with sub-nanometric repeatability over the millimetre displacement range

We propose a 2D displacement control system with sub-nanometric repeatability on position over the millimetre travel range on both axes. It could be useful for nanofabrication processes or other applications related to the nanotechnology community. In our case, the apparatus is planned to be used in atomic force microscopes and lithography systems as a sample-holding device. The method is based on a heterodyne interferometric sensor and a home-made high frequency phase-shifting electronic board. This paper presents the complete mechanical system and gives experimental results showing a repeatability of 0.5 nm over a moving range of 5 mm.

Efficient cw operation of diode-pumped Nd:YLF lasers at 1312.0 and 1322.6 nm for a silver atom optical clock

Abstract We describe the efficient cw operation of two Nd:YLF lasers at 1312.0 and 1322.6 nm for the development of a silver atom optical clock. For a simple linear cavity laser configuration investigated at these wavelengths, we have obtained an output power of 3.6 W at 1312.0 nm for 13.8 W of absorbed pump power ( λ =806 nm) and 4.8 W output at 1322.6 nm with 16.3 W pump. At 1312.0 nm, using a twisted-mode cavity, a single-frequency output power of 750 mW has been obtained. Single-frequency operation (450 mW) at 1322.6 nm was achieved using an intra-cavity solid etalon.

Highly accurate positioning control method for piezoelectric actuators based on phase-shifting optoelectronics

We propose a sub-nanometric positioning control method for piezoelectric actuators based on a home-made high frequency phase shifting electronic circuit and a heterodyne interferometer. The method has been set up. Using a readily available piezoelectric actuator, we demonstrate that our method allows back and forth displacement without nonlinearities. Repeatability of 0.053 nm has been obtained over 1 µm displacement range. Displacement steps as low as 260 pm are presented. Such a method could be very useful for the nanotechnology and nanometrology communities for nano-scale manipulations or nano-assembly applications.

First determination of the Planck constant using the LNE watt balance

After separate developments of the different elements with continuous characterizations and improvements, the LNE watt balance has been assembled. This paper describes the system in detail and gives its first measurements of the Plancks constant h. The value determined in air is h = 6.626 068 8(20) × 10−34 Js which differs in relative terms by −0.05 × 10−7 from the h90 value and by −1.1 × 10−7 from that of the 2010 CODATA adjustment of h. The relative standard uncertainty associated is 3.1 × 10−7.

Hyperfine Structure Analysis of the 33P (6-3) Line of 127I2 at 633 nm Using a Continuous-wave Tunable Dye Laser

A spectroscopic study of the 33P (6-3) line in the B-X system of 127I2 iodine molecule at 633 nm was undertaken using a continuous-wave tunable dye laser. The uncertainty in the frequency interval measurements between the hyperfine components, of a few kilohertz, allows determination of the differences between the constants of the four principal hyperfine interactions.