|Dr. P. Arora/ Dr Ashish Agarwal|
|Room: 132/128B, Main Building|
|CSIR – NPL, Dr. K. S. Krishnan Marg|
|New Delhi – 110012|
|Ph: +91 4560 9233/8384|
|Fax: +91 4560 9240|
Cesium fountain frequency standards
Cesium fountain clocks provide most precise and accurate measurements of time and frequency. Most of the developed countries have developed such clocks which are already operating as primary standards. CSIR- National Physical Laboratory India (NPLI) started efforts to realize India’s first fountain clock only few years back. The first cesium atomic fountain (India-CsF1) frequency standard is now completely assembled and operational. The CsF1 fountain has a (0, 0, 1) geometry of the magneto-optical trap (MOT) for cooling and launching operations. In this geometry, four out of the six cooling beams are in horizontal plane and other are going up and down, respectively. The atoms are first loaded and cooled in MOT followed by further cooling in optical molasses (OM). They are launched using moving molasses (frequency detuning of vertical beams) and cooled further with polarization gradient cooling. The operational parameters are currently being optimized and the complete frequency evaluation will soon be done.
The division has recently started a project to design and build a second Cs fountain (NOVOCEF) with special design features that enable us to carefully investigate the systematic errors in order to enhance the accuracy of our frequency standard to a few parts in 1016 – which would be at the level of the best in the world. One special feature of the design would be to employ a novel method of optical pumping using two lasers to enhance the number of cold atoms taking part in the microwave interrogation process. It is also planned to use an elaborate design of the microwave cavity in order to reduce “distributed microwave cavity phase shift”.