Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

URSI General Assembly and Scientific Symposium

The progress of the NIM6 fountain clock in NIM

Fang Fang, Weiliang Chen, Kun Liu, Nianfeng Liu, Shaoyang Dai, Lei Han, Tianchu Li

Published Aug 1, 2017• 2 citations
Publisher

Abstract

A new fountain clock NIM6 is under construction. Besides some improvements on the vacuum system, a new Ramsey cavity and a microwave synthesizer are made to reduce the Type B uncertainty. Another feature of NIM6 is collecting atoms from a MOT loading optical molasses to get more atoms with a more uniform density distribution. With a new ultra-stable microwave frequency synthesizer based on cryogenic sapphire oscillator (CSO) or ultra-stable laser, NIM6 is aiming to reach the quantum projection noise, thus leading to a reduced Type A uncertainty.

DOI
10.23919/ursigass.2017.8105340

Related papers

Design of the new NIM6 fountain with collecting atoms from a 3D MOT loading optical molasses

Fang Fang, Weiliang Chen, Kun Liu +3 more

We report the design of a new cesium fountain clock NIM6, which is under construction in NIM. Besides some improvements on the vacuum system, Ramsey cavity and microwave synthesizer to reduce the Type B uncertainty. Another major improvement on NIM6 is to collect more atoms from a MOT loading optical molasses and optical pumping to get a better signal to noise ratio at the detection. The atom distribution will be more uniform compared with a 2D MOT loading optical molasses, and the diameter of the cloud can be adjusted by the intensity and detuning of lights during the post cooling to keep the collisional-induced frequency shift low. The atom numbers can be further increased by a new de-pumping - optical pumping procedure to pump atoms to the |F=3, mF=0> clock state directly. With a new cryogenic sapphire oscillator (CSO) based frequency synthesizer, NIM6 is aiming to reach the quantum projection noise, thus leading to a reduced Type A uncertainty compared with NIM5.

Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS)•Apr 1, 2015•7 citations

The preliminary evaluation of the new fountain clock NIM6

Fang Fang, Weiliang Chen, Kun Liu +3 more

In this paper, we introduce the design of our new fountain clock NIM6. Besides some improvements on the vacuum system, Ramsey cavity to reduce the Type B uncertainty, NIM6 collects atoms from a MOT loading optical molasses to get a better signal to noise ratio. The atom density will be more uniform compared to a 2D MOT loading optical molasses, and the diameter of the cloud can be adjusted by the intensity and detuning of lights during the post cooling after MOT to keep the collisional shift low. Cs atoms are collected in the lower MOT chamber for 0.5 second, and then the MOT magnetic field is turned down. Atoms are accelerated for 1 ms in a moving molasses, and further cooled for another 1.5 ms by adiabatically reducing the cooling beam intensities and red offsetting the frequencies.

URSI Asia-Pacific Radio Science Conference•Mar 1, 2019•4 citations

Design of the new NIM6 fountain with collecting atoms from a 3D MOT loading optical molasses

房芳

•Jan 1, 2015•0 citations

Reaching the quantum limit in a fountain clock using a microwave oscillator phase locked to an ultrastable laser

S. Weyers, B. Lipphardt, H. Schnatz

A cesium fountain clock is operated utilizing a microwave oscillator that derives its frequency stability from a stable laser by means of a fiber-laser femtosecond frequency comb. This oscillator is based on the technology developed for optical clocks and replaces the quartz-based microwave oscillator commonly used in fountain clocks. As a result, a significant decrease in the frequency instability of the fountain clock is obtained, reaching $7.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}14}{[\ensuremath{\tau}\text{ }(\text{s})]}^{\ensuremath{-}1/2}$. We could demonstrate that for a significant range of detected atom numbers the instability is limited by quantum projection noise only, and that for the current status of this fountain clock the microwave source poses no limit on the achievable frequency instability.

arXiv:0901.2788•Physical Review A•Mar 11, 2009•86 citations

Progress on the construction of an atomic cesium fountain at NIM

Tianchu Li, Mingshou Li, Huang Bingying +2 more

An atomic cesium fountain has been designed for a new primary standard of frequency in China. Cold atomic clouds collected in the magneto-optical trap (MOT) were previously reported (1995). To further improve the performance of the MOT we have optimized the laser-optical system and operation of the MOT. Some optical elements were replaced with new ones with better quality; frequency stabilization of lasers and arrangement of the optical system was modified; and polarization maintaining (PM) optical fibers were adopted to transfer lights from the optical system to MOT. We also installed the fluorescence detecting - amplifying assembles to take the time of flight (TOF) measurement of the cold atoms.

Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS)•Nov 13, 2002•1 citation

Progress towards a 133Cs fountain as frequency standard in Brazil

Daniel Varela Magalhães, Mafalda S. Santos, Aida Bebeachibuli +2 more

The well-known MOT technique is used to trap and cool 133 Cs atoms to reproduce the SI second in an atomic fountain. About 10 8 cesium atoms are caught in a magnetooptical trap from a vapor cell at room temperature. The fountain has a (1,1,1)-geometry for the laser cooling and launching operation. The three upper beams have the same polarization, opposite to the three lower ones. The interrogation and preparation cavities have also been constructed, as well as characterized, concerning the temperature tunability in vacuum. The microwave synthesizer has been constructed in collaboration with BNM-SYRTE, time-and-frequency group. The synthesizer has been compared to a very stable oscillator at BNM-SYRTE resulting in a short-term stability of 9.7 × 10 -14 τ -1/2 .

Laser Physics•Jan 1, 2004•5 citations
A new fountain clock NIM6 is under construction. Besides some improvements on the vacuum system, a new Ramsey cavity and a microwave synthesizer are made to reduce the Type B uncertainty. Another feature of NIM6 is collecting atoms from a MOT loading optical molasses to get more atoms with a more uniform density distribution. With a new ultra-stable microwave frequency synthesizer based on cryogenic sapphire oscillator (CSO) or ultra-stable laser, NIM6 is aiming to reach the quantum projection noise, thus leading to a reduced Type A uncertainty.
We report the design of a new cesium fountain clock NIM6, which is under construction in NIM. Besides some improvements on the vacuum system, Ramsey cavity and microwave synthesizer to reduce the Type B uncertainty. Another major improvement on NIM6 is to collect more atoms from a MOT loading optical molasses and optical pumping to get a better signal to noise ratio at the detection. The atom distribution will be more uniform compared with a 2D MOT loading optical molasses, and the diameter of the cloud can be adjusted by the intensity and detuning of lights during the post cooling to keep the collisional-induced frequency shift low. The atom numbers can be further increased by a new de-pumping - optical pumping procedure to pump atoms to the |F=3, mF=0> clock state directly. With a new cryogenic sapphire oscillator (CSO) based frequency synthesizer, NIM6 is aiming to reach the quantum projection noise, thus leading to a reduced Type A uncertainty compared with NIM5.
In this paper, we introduce the design of our new fountain clock NIM6. Besides some improvements on the vacuum system, Ramsey cavity to reduce the Type B uncertainty, NIM6 collects atoms from a MOT loading optical molasses to get a better signal to noise ratio. The atom density will be more uniform compared to a 2D MOT loading optical molasses, and the diameter of the cloud can be adjusted by the intensity and detuning of lights during the post cooling after MOT to keep the collisional shift low. Cs atoms are collected in the lower MOT chamber for 0.5 second, and then the MOT magnetic field is turned down. Atoms are accelerated for 1 ms in a moving molasses, and further cooled for another 1.5 ms by adiabatically reducing the cooling beam intensities and red offsetting the frequencies.
A cesium fountain clock is operated utilizing a microwave oscillator that derives its frequency stability from a stable laser by means of a fiber-laser femtosecond frequency comb. This oscillator is based on the technology developed for optical clocks and replaces the quartz-based microwave oscillator commonly used in fountain clocks. As a result, a significant decrease in the frequency instability of the fountain clock is obtained, reaching $7.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}14}{[\ensuremath{\tau}\text{ }(\text{s})]}^{\ensuremath{-}1/2}$. We could demonstrate that for a significant range of detected atom numbers the instability is limited by quantum projection noise only, and that for the current status of this fountain clock the microwave source poses no limit on the achievable frequency instability.
An atomic cesium fountain has been designed for a new primary standard of frequency in China. Cold atomic clouds collected in the magneto-optical trap (MOT) were previously reported (1995). To further improve the performance of the MOT we have optimized the laser-optical system and operation of the MOT. Some optical elements were replaced with new ones with better quality; frequency stabilization of lasers and arrangement of the optical system was modified; and polarization maintaining (PM) optical fibers were adopted to transfer lights from the optical system to MOT. We also installed the fluorescence detecting - amplifying assembles to take the time of flight (TOF) measurement of the cold atoms.
The well-known MOT technique is used to trap and cool 133 Cs atoms to reproduce the SI second in an atomic fountain. About 10 8 cesium atoms are caught in a magnetooptical trap from a vapor cell at room temperature. The fountain has a (1,1,1)-geometry for the laser cooling and launching operation. The three upper beams have the same polarization, opposite to the three lower ones. The interrogation and preparation cavities have also been constructed, as well as characterized, concerning the temperature tunability in vacuum. The microwave synthesizer has been constructed in collaboration with BNM-SYRTE, time-and-frequency group. The synthesizer has been compared to a very stable oscillator at BNM-SYRTE resulting in a short-term stability of 9.7 × 10 -14 τ -1/2 .