Stella Torres Müller

The Brazilian time and frequency atomic standards program

Cesium atomic beam clocks have been the workhorse for many demanding applications in science and technology for the past four decades. Tests of the fundamental laws of physics and the search for minute changes in fundamental constants, the synchronization of telecommunication networks, and realization of the satellite-based global positioning system would not be possible without atomic clocks. The adoption of optical cooling and trapping techniques, has produced a major advance in atomic clock precision. Cold-atom fountain and compact cold-atom clocks have also been developed. Measurement precision of a few parts in 10(15) has been demonstrated for a cold-atom fountain clock. We present here an overview of the time and frequency metrology program based on cesium atoms under development at USP São Carlos. This activity consists of construction and characterization of atomic-beam, and several variations of cold-atom clocks. We discuss the basic working principles, construction, evaluation, and important applications of atomic clocks in the Brazilian program.

Comparative short-term stability for a Cs beam and an expanding cold atomic cloud of Cs used as atomic frequency standards

We have compared the stability of two distinct atomic frequency standards. One is based on an atomic cold cloud of 133Cs atoms in free expansion, interrogated by a Rabi resonance. The other standard is based on a thermal Cs beam interrogated by the separated oscillatory field method (Ramsey’s method). The atomic expanding cloud standard shows better stability and technical advances based on its simplicity.

Demonstration and Observation of a Frequency Standard Based on an Expanding Cold Atoms Cloud of Cesium

This work reports the first results obtained in a laboratory system implemented to be a primary standard based on an expanding cloud of cold 133Cs. An atomic sample is prepared through the magneto-optical trapping technique, and after the loading procedure the atomic cloud is left to freely expand. A microwave interrogation signal is applied to the atoms, probing them in the ground state transition 6S1/2(F = 3)- 6S1/2(F = 4). The microwave interrogation was applied either in one or two pulses methods. The system could be also locked in a commercial standard to perform its stability evaluation. The first results showed a stability of 9times10 -11 tau-frac12, promising for such use of simple type of frequency standard

Joint effort to commissioning a thermal cesium beam with optical pumping as primary frequency standard to Brazilian NMI

This paper describes the progress on commissioning a thermal Cesium beam frequency standard developed at IFSC-USP and transferred to the Brazilian NMI in order to be continuously operated as a primary frequency standard. The system is composed of a short Ramsey cavity for electromagnetic excitation and an optical pumping for atom detection and energy-state selection. The uncertainty budget for the measurement technique is under verification to acquire the same performance achieved earlier during the scientific development of the standard. Some aspects of the standard implantation are discussed here according to the technical and metrological requirements for the system.

The Brazilian Atomic Fountain Primary Frequency Standard

From some years our group has been investing efforts to develop a Caesium atomic fountain system to operate as a frequency standard. Our most recent results concern the observation of the first Ramsey resonance and we also performed a characterization of it. We discuss the main characteristics of our system and the improvements on planning

Development of an ultrastable laser at 1550 nm

This work deals with the development of a 1550 nm diode laser stabilized against a high finesse cavity (>250,000). It reports the components, apparatus and some preliminary results for the system under construction.

Progress in Brazilian Cesium atomic fountain-BrCsF

The goal of this work is to present new progress in the Brazilian Cesium fountain Br-CsF, which is currently back to operation after improvements in its optical system. The first result of this new stage is the Ramsey fringe showed in Figure 5. The central oscillation has a FWHM of 1.5 Hz with cycle time of 2 s and with signal noise ratio of 200. This fringe was obtained loading ~109 atoms into a magneto optical trap with loading time of tl = 1.2 s.

Portable compact cold atoms clock topology

The compact frequency standard under development at USP Sao Carlos is a cold atoms system that works with a distributed hardware system principle and temporal configuration of the interrogation method of the atomic sample, in which the different operation steps happen in one place: inside the microwave cavity. This type of operation allows us to design a standard much more compact than a conventional one, where different interactions occur in the same region of the apparatus. In this sense, it is necessary to redefine all the instrumentation associated with the experiment. This work gives an overview of the topology we are adopting for the new system.

Historical overview of Ramsey spectroscopy and its relevance on Time and Frequency Metrology

A brief overview of the historical evolution of the method of successive oscillatory fields developed by Norman Ramsey, and some different implementations of the decurrent methodology are presented. We use time and frequency standards, from Cs atomic beams to optical standards, as examples. The scientific progress and the technological implementation achieved through a partnership between USP-SC and INMETRO are shown on the characterization of each time and frequency standard.

New generation of a mobile primary frequency standard based on cold atoms

We have constructed a mobile primary frequency standard using intra-cavity cold cesium atoms and the results have shown the advantages of using this kind of system compared to cesium beam standards. Based on the first setup with an expanding cloud of atoms, we can plan the construction of a clock more compact since it has no strict size limitations. In order to assemble the new system even smaller, the development of a system containing lasers, microwave source and cavity in a single box has already begun. The mobile atomic standard based on cold atoms is a possible strategic product with a broad range of applications and an important contribution to a primary standard of high relevance.