Yuri B. Ovchinnikov

Development of a strontium optical lattice clock for the SOC mission on the ISS

The ESA mission “Space Optical Clock” project aims at operating an optical lattice clock on the ISS in approximately 2023. The scientific goals of the mission are to perform tests of fundamental physics, to enable space-assisted relativistic geodesy and to intercompare optical clocks on the ground using microwave and optical links. The performance goal of the space clock is less than 1 × 10-17 uncertainty and 1 × 10-15 τ-1/2 instability. Within an EU-FP7-funded project, a strontium optical lattice clock demonstrator has been developed. Goal performances are instability below 1 × 10-15 τ-1/2 and fractional inaccuracy 5 × 10-17. For the design of the clock, techniques and approaches suitable for later space application are used, such as modular design, diode lasers, low power consumption subunits, and compact dimensions. The Sr clock apparatus is fully operational, and the clock transition in 88Sr was observed with linewidth as small as 9 Hz.

Accurate rubidium atomic fountain frequency standard

The design, operating parameters and the accuracy evaluation of the NPL Rb atomic fountain are described. The atomic fountain employs a double magneto-optical arrangement that allows a large number of 87Rb atoms to be trapped, a water-cooled temperature-stabilized interrogation region and a high quality factor interrogation cavity. From the uncertainties of measured and calculated systematic frequency shifts, the fractional frequency accuracy is estimated to be 3.7 ? 10?16. The fractional frequency stability, limited predominantly by noise in the local oscillator, is measured to be 7 ? 10?16 after one day of averaging. Based on the proposed quasi-continuous regime of operation of the fountain, the accuracy of the Rb standard of 5 ? 10?17 reachable in two days of averaging is predicted.

The space optical clocks project: Development of high-performance transportable and breadboard optical clocks and advanced subsystems

The use of ultra-precise optical clocks in space (“master clocks”) will allow for a range of new applications in the fields of fundamental physics (tests of Einsteins theory of General Relativity, time and frequency metrology by means of the comparison of distant terrestrial clocks), geophysics (mapping of the gravitational potential of Earth), and astronomy (providing local oscillators for radio ranging and interferometry in space). Within the ELIPS-3 program of ESA, the “Space Optical Clocks” (SOC) project aims to install and to operate an optical lattice clock on the ISS towards the end of this decade, as a natural follow-on to the ACES mission, improving its performance by at least one order of magnitude. The payload is planned to include an optical lattice clock, as well as a frequency comb, a microwave link, and an optical link for comparisons of the ISS clock with ground clocks located in several countries and continents. Undertaking a necessary step towards optical clocks in space, the EU-FP7-SPACE-2010-1 project no. 263500 (SOC2) (2011–2015) aims at two “engineering confidence“, accurate transportable lattice optical clock demonstrators having relative frequency instability below 1×10−15 at 1 s integration time and relative inaccuracy below 5×10−17. This goal performance is about 2 and 1 orders better in instability and inaccuracy, respectively, than todays best transportable clocks. The devices will be based on trapped neutral ytterbium and strontium atoms. One device will be a breadboard. The two systems will be validated in laboratory environments and their performance will be established by comparison with laboratory optical clocks and primary frequency standards. In order to achieve the goals, SOC2 will develop the necessary laser systems - adapted in terms of power, linewidth, frequency stability, long-term reliability, and accuracy. Novel solutions with reduced space, power and mass requirements will be implemented. Some of the laser systems will be developed towards particularly high compactness and robustness levels. Also, the project will validate crucial laser components in relevant environments. In this paper we present the project and the results achieved during the first year.

Zeeman slower based on magnetic dipoles

In this paper it is proposed to use a periodic array of very strong and compact neodymium magnets to create the desired magnetic field of the Zeeman slower. A model of the slower based on point-like magnetic dipoles has been introduced, which is a key element in designing of such type of a slower. The high precision of that simple model is confirmed with exact numerical calculations of the magnetic field for finite-size magnets. The two basic configurations of the magnetic dipole Zeeman slower, with longitudinal and transverse direction of magnetic dipoles, have been investigated.

Zeeman slowers for strontium based on permanent magnets

We present the design, construction, and characterization of longitudinal- and transverse-field Zeeman slowers, based on arrays of permanent magnets, for slowing thermal beams of atomic Sr. The slowers are optimized for operation with deceleration related to the local laser intensity (by the parameter ), which uses more effectively the available laser power, in contrast to the usual constant deceleration mode. Slowing efficiencies of up to ≈18% are realized and compared to those predicted by modelling. We highlight the transverse-field slower, which is compact, highly tunable, light-weight, and requires no electrical power, as a simple solution to slowing Sr, well-suited to space-borne application. For 88Sr we achieve a slow-atom flux of around 6 × 109 atoms s−1 at 30 ms−1, loading approximately 5 × 108 atoms in to a magneto-optical-trap, and capture all isotopes in approximate relative natural abundances.

Coherent manipulation of atoms by copropagating laser beams

Optical dipole traps and fractional Talbot optical lattices based on the interference between multiple copropagating laser beams are proposed. The variation of relative amplitudes and phases of the interfering light beams of these traps makes it possible to manipulate the spatial position of trapped atoms. Examples of spatial translation and splitting of atoms between a set of the interference traps are considered. The prospect of constructing all-light atom chips based on the proposed technique is presented.

Longitudinal Zeeman slowers based on permanent magnetic dipoles

Abstract Longitudinal Zeeman slowers composed of arrays of compact discrete neodymium magnets are proposed. The general properties of these slowers, as well as specific designs of short spin-flip Zeeman slowers for Sr and Rb atoms are described. The advantages of these slowers are their simplicity, low cost and absence of consumed electrical power and corresponding water cooling. The smoothness of the magnetic field together with ease of adjustability makes it possible to operate these slowers near the theoretical limits of deceleration, making them more compact and efficient.

Towards Neutral-atom Space Optical Clocks (SOC2): Development of high-performance transportable and breadboard optical clocks and advanced subsystems

The use of ultra-precise optical clocks in space (“master clocks”) will allow for a range of new applications covering the fields of fundamental physics (tests of Einsteins theory of General Relativity, time and frequency metrology by means of the comparison of distant terrestrial clocks), geophysics (mapping of the gravitational potential of Earth), and astronomy (providing local oscillators for radio ranging and interferometry in space). Within the ELIPS-3 program of ESA, the “Space Optical Clocks” (SOC) project aims to install and to operate an optical lattice clock on the ISS towards the end of this decade, as a natural follow-on to the ACES mission (which is based on a cesium microwave clock), improving its performance by at least one order of magnitude. The payload is planned to include an optical lattice clock, as well as a frequency comb, a microwave link, and an optical link for comparisons of the ISS clock with ground clocks located in several countries and continents. Undertaking a necessary step towards optical clocks in space, the EU-FP7-SPACE2010-1 project no. 263500 (SOC2) (2011-2015) will develop two “engineering confidence“, accurate transportable lattice optical clock demonstrators having relative frequency instability below 1×10 -15 at 1s integration time and relative inaccuracy below 5×10 -17 . This goal performance is about 2 and 1 orders better in instability and inaccuracy, respectively, than today’s best transportable clocks. The devices will be based on trapped neutral ytterbium and strontium atoms. One device will be a breadboard. The two systems will be validated in laboratory environments and their performance will be established by comparison with laboratory optical clocks and primary frequency standards. In order to achieve the goals, SOC2 will develop the necessary laser systems adapted in terms of power, linewidth, frequency stability, long-term reliability, and accuracy. Novel solutions with reduced space, power and mass requirements will be implemented. Some of the laser systems will be developed towards particularly high compactness and robustness levels. Also, the project will validate crucial laser components in relevant environments. This paper will give an overview of the project and of the results achieved during theProject ReCover aims at developing beyond state-of-the-art service capabilities to support fighting deforestation and forest degradation in the tropical region. The service capabilities mean provision of a monitoring system of forest cover, forest cover changes, and biomass including a robust accuracy assessment. This paper presents the forest monitoring concept and the first results on Recover study sites. ReCover contributes to the efforts to reduce the errors in the estimates of the terrestrial carbon balance that result from uncertain rates of tropical deforestation. It develops methods for the REDD (Reducing Emissions from Deforestation and Forest Degradation) process by developing and implementing satellite image based methods for the monitoring of tropical forests. The REDD will be a major driver for the development of more effective and more reliable procedures for the monitoring of tropical forests. Many developing countries lack human resources and funding for detailed forest inventories. This paper reports the achievements of the first year of ReCover and the results of services in Mexico, Guyana, Democratic Republic of Congo, and Fiji. Altogether 42 products were delivered to the users of Recover. The accuracy in forest and non-forest classification was from 85 % to 91 % with one exception (76 %).

Operation of the caesium fountain frequency standard NPL-CsF2 at the collisional shift cancellation point

We report on characterisation of a caesium fountain primary frequency standard NPL-CsF2 operating in a regime where the collisional frequency shift is nearly cancelled by controlling the clock state population ratio and other fountain parameters. We describe in detail the operation protocols possible in this case and their limitations and report on a long-term study of the stability of the parameters defining the cancellation point. Finally, we report on the frequency measurements where NPL-CsF2 was used as a reference, namely, a new measurement of the 87Rb clock transition and several evaluations of the TAI step interval.

Measurement of rubidium ground-state hyperfine transition frequency using atomic fountains

The results of precision measurements of the 87Rb ground-state hyperfine transition frequency, which were conducted at NPL from 2009 to 2013, are reported. The resulting frequency, measured using NPLs Cs and Rb atomic frequency standards, demonstrates reasonable agreement with the most recent measurements reported by LNE-SYRTE.