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2000 IEEUEIA International Frequency Control Symposium and Exhibition Characterization of a Cold Cesium Source for PARCS: Primary Atomic Reference Clock in Space

Leo W. Hollberg, John E. Kitching

Published Jan 1, 2000• 0 citations
OpenAlex

Abstract

The PARCS (Primary Atomic Reference Clock in Space) project is a joint NIST-JPL-University of Colorado venture aimed at placing a cesium (CS) atomic clock aboard the International Space Station (ISS). This orbiting clock will achieve high accuracy, in part due to the long Ramsey times afforded by the microgravity environment, and allow for precision tests of fundamental physics including relativity theory. As part of this effort, we are evaluating the characteristics of a prototype cold CS source based on launching atoms from an optical molasses. The apparatus described here will be used to develop other PARCS components such as the microwave cavity structure and detection systems, and to investigate two-dimensional cooling schemes for future CS fountains and space clocks.

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Characterization of a cold cesium source for PARCS: primary atomic reference clock in space

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The PARCS (Primary Atomic Reference Clock in Space) project is a joint NIST-JPL-University of Colorado venture aimed at placing a cesium (Cs) atomic clock aboard the International Space Station (ISS). This orbiting clock will achieve high accuracy, in part due to the long Ramsey times afforded by the microgravity environment, and allow for precision tests of fundamental physics including relativity theory. As part of this effort, we are evaluating the characteristics of a prototype cold Cs source based on launching atoms from an optical molasses. The apparatus described will be used to develop other PARCS components such as the microwave cavity structure and detection systems, and to investigate two-dimensional cooling schemes for future Cs fountains and space clocks.

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Article

Marie-Claude Gagné, J.-S. Boulanger, R J W Douglas

The accelerated development of laser methods for manipulating the internal state and motion of atoms, and the recent primary evaluation in France of a cesium frequency standard using cold atoms in an atomic fountain configuration, allow the frontiers of time metrology, accuracy, and stability to be pushed near parts in the 1016 level, a factor of 100 over the present primary laboratory clocks. These positive results revived the development of more accurate cesium atomic clocks, and the Institute of National Measurement Standards (INMS), of the National Research Council of Canada (NRC) is undertaking a cesium-fountain project aimed at reaching these new levels of accuracy and stability. This paper reviews its present status. To appreciate the considerable impact of cold atoms in time and frequency metrology, we begin by recalling the background principles of traditional cesium frequency standards, their typical performance and main limitations. After introducing the important theoretical results essential to understanding the techniques of laser cooling and magneto-optical trapping, we focus on describing the characterization and control of our magneto-optical trap (MOT) and report the parameters that allow us to fill the trap with a few million atoms in less than a second and cool them to a temperature lower than 5 muK using optical molasses. We will describe the specifics of our cesium-fountain prototype, which operates with a 2-dimensional moving molasses. This special configuration is applicable for multipulse operation of the fountain, which can greatly relax the local oscillator requirements for time keeping. Finally, progress toward our objective of launching cooled atoms, at a rate of one ensemble per second, at speeds of 7 m/s, for a fountain with an interrogation time of about 1 s, will be analysed.PACS Nos.: 06.20, 06.30, and 32.80P

Canadian Journal of Physics•Aug 1, 1998•0 citations

Design Concept for the Microwave Interrogation Structure in PARCS

G.J. Dick, William M. Klipstein, Thomas P. Heavner +1 more

In this paper we describe key aspects of the conceptual design of the microwave interrogation structure in the laser-cooled cesium frequency standard that is part of the primary atomic reference clock in space (PARCS) experiment. The PARCS standard uses balls of cold atoms launched in a pulsed beam configuration. The microwave interrogation will take place in two independent high-Q (/spl sim/20,000) cavities operated in the TE/sub 011/ mode. The cavities will be operated off resonance by several linewidths, with a resonant coupling structure delivering the microwave to the two cavities. One persistent problem related to the end-to-end phase shift has been the extreme temperature sensitivity of the phase of inside the cavities to that just outside the cavities. The end-to-end phase shift must ultimately be known to around 3 microradians, and stable long enough to allow measurement of the shift as well as to allow normal clock operation. Operating the cavities off resonance reduces this sensitivity more strongly than reducing the cavity Q.

•Dec 5, 2002•0 citations
The PARCS (Primary Atomic Reference Clock in Space) project is a joint NIST-JPL-University of Colorado venture aimed at placing a cesium (CS) atomic clock aboard the International Space Station (ISS). This orbiting clock will achieve high accuracy, in part due to the long Ramsey times afforded by the microgravity environment, and allow for precision tests of fundamental physics including relativity theory. As part of this effort, we are evaluating the characteristics of a prototype cold CS source based on launching atoms from an optical molasses. The apparatus described here will be used to develop other PARCS components such as the microwave cavity structure and detection systems, and to investigate two-dimensional cooling schemes for future CS fountains and space clocks.
The PARCS (Primary Atomic Reference Clock in Space) project is a joint NIST-JPL-University of Colorado venture aimed at placing a cesium (Cs) atomic clock aboard the International Space Station (ISS). This orbiting clock will achieve high accuracy, in part due to the long Ramsey times afforded by the microgravity environment, and allow for precision tests of fundamental physics including relativity theory. As part of this effort, we are evaluating the characteristics of a prototype cold Cs source based on launching atoms from an optical molasses. The apparatus described will be used to develop other PARCS components such as the microwave cavity structure and detection systems, and to investigate two-dimensional cooling schemes for future Cs fountains and space clocks.
The Primary Atomic Reference Clock in Space (PARCS) project is a joint NIST-JPL-University of Colorado venture aimed at placing a Cs atomic clock aboard the International Space Station (ISS). This orbiting clock will achieve high accuracy, in part due to the long Ramsey times afforded by the microgravity environment, and allow for precision tests of fundamental physics including relativity theory. As part of this effort, we are evaluating the characteristics of a prototype cold Cs source based on launching atoms from an optical molasses. Experimental results, in conjunction with theoretical modeling of atom flux requirements, will be applied to the design and construction of a robust, space-qualified device. The apparatus described here will be used to develop other PARCS components such as the microwave cavity structure and detection systems, and to investigate two-dimensional cooling schemes for future Cs fountains and space clocks.
The PARCS (Primary Atomic Reference Clock in Space) project is a joint NIST JPL venture aimed at placing a Cs atomic clock aboard the International Space Station. This orbiting clock will achieve high accuracies in part due to the long Ramsey times afforded by the microgravity environment. The clock will allow a wide range of precision tests of fundamental physics including relativity theory. Our group at NIST is performing experimental studies of a "prototype" cold Cs source based on launching atoms from optical molasses. The results of our work will be applied to the design and construction of a robust, space qualified device. Additionally, this work is important for the development of future Cs fountains. We describe our apparatus, the present state of our experimental work, and planned improvements.
The primary atomic reference clock in space (PARCS) is a collaboration between the National Institute of Standards and Technology (NIST), the Jet Propulsion Laboratory (JPL) and the University of Colorado to build a laser-cooled cesium-beam atomic clock as a science payload for the International Space Station (ISS). The three primary goals of the PARCS experiment are: (1) to demonstrate laser cooling of atoms in space; (2) to use laser cooling to build the most accurate space clock; (3) to use the clock to test fundamental assumptions and predictions of relativity theory. We discuss aspects of the PARCS cesium physics package subsystem design addressing magnetic, microwave and vacuum requirements as well as operational scenarios.
The accelerated development of laser methods for manipulating the internal state and motion of atoms, and the recent primary evaluation in France of a cesium frequency standard using cold atoms in an atomic fountain configuration, allow the frontiers of time metrology, accuracy, and stability to be pushed near parts in the 1016 level, a factor of 100 over the present primary laboratory clocks. These positive results revived the development of more accurate cesium atomic clocks, and the Institute of National Measurement Standards (INMS), of the National Research Council of Canada (NRC) is undertaking a cesium-fountain project aimed at reaching these new levels of accuracy and stability. This paper reviews its present status. To appreciate the considerable impact of cold atoms in time and frequency metrology, we begin by recalling the background principles of traditional cesium frequency standards, their typical performance and main limitations. After introducing the important theoretical results essential to understanding the techniques of laser cooling and magneto-optical trapping, we focus on describing the characterization and control of our magneto-optical trap (MOT) and report the parameters that allow us to fill the trap with a few million atoms in less than a second and cool them to a temperature lower than 5 muK using optical molasses. We will describe the specifics of our cesium-fountain prototype, which operates with a 2-dimensional moving molasses. This special configuration is applicable for multipulse operation of the fountain, which can greatly relax the local oscillator requirements for time keeping. Finally, progress toward our objective of launching cooled atoms, at a rate of one ensemble per second, at speeds of 7 m/s, for a fountain with an interrogation time of about 1 s, will be analysed.PACS Nos.: 06.20, 06.30, and 32.80P
In this paper we describe key aspects of the conceptual design of the microwave interrogation structure in the laser-cooled cesium frequency standard that is part of the primary atomic reference clock in space (PARCS) experiment. The PARCS standard uses balls of cold atoms launched in a pulsed beam configuration. The microwave interrogation will take place in two independent high-Q (/spl sim/20,000) cavities operated in the TE/sub 011/ mode. The cavities will be operated off resonance by several linewidths, with a resonant coupling structure delivering the microwave to the two cavities. One persistent problem related to the end-to-end phase shift has been the extreme temperature sensitivity of the phase of inside the cavities to that just outside the cavities. The end-to-end phase shift must ultimately be known to around 3 microradians, and stable long enough to allow measurement of the shift as well as to allow normal clock operation. Operating the cavities off resonance reduces this sensitivity more strongly than reducing the cavity Q.