NICOP - Studies related to cold atoms frequency standards

Compact and portable primary frequency standards are highly important for various civil andmilitary applications including marine vessels operations (e.g.: GPS-denied/spoofed navigation,encrypt communication, etc.). While laboratory-based frequency standards can reach relativeuncertainties (Allan deviation) down to 10-18, the devices that typically operate in the field maybe a rubidium vapor frequency standard, a rubidium frequency standard disciplined by the globalpositioning system (GPS), or the more accurate cesium beam frequency standards (CBFS).Based on the manufacturer specification, the ???High Performance??? CBFS guarantied stability(Allan deviation) is 10-14 at 30 days.Typical time error of the low-cost rubidium vapor frequency standard can reach 1???s/day, whileseveral military and civil applications require time error in the range of 5-10 ns/day. A GPSdisciplined rubidium frequency standard can meet this requirement. However, the GPS systemmay be unavailable in a given geographical area because of jamming or spoofing attacks, orRadio Frequency Interference (RFI). The effect of RFI is to create a GPS-stressed or GPS-deniedenvironment. A spoofing attack is one where a malicious transmitter broadcasts a GPS-likesignal with the intent to deceive GPS users.The CBFS family, which can provide the smaller time error, is in the market for more than 50years and is still the ???working horse??? of the laboratories contributing to the International AtomicTime (TAI) and other applications. However, although this technology is mature and reliable, itseems that it reached its limit.Lab-based frequency standards that use ultra-cold atoms reach stabilities (Allen deviation) downto few parts of 10-18, and time error well below 1ns/day. However, those standards are too bulkyand sensitive for field use. Recently several groups started the development of small-sizefrequency standards based on ultra-cold atoms, targeting better performances compared to theexisting CBFS.The Atom chip group in Ben-Gurion University of the Negev, in collaboration with AccuBeatLtd. (an Israeli producer of vapor-based frequency standards), is engaged in the development ofsuch a frequency standard. The developed frequency standard will have an Allan deviation below10-13 at 105s and a time drift below10 ns/day. A technological demonstrator is now operational,and we are now working to improve its performance and upgrade some of its subsystems.However, the performance of such an accurate device depends on the fine details of severalphysical processes. Understanding those details is the aim of this project, which will cover twoareas: The first one is a detailed study of the processes that involve ultra-cold atoms, taking intoaccount the fact that the device will operate outside of the laboratory. The aim of this multiparameterstudy is to investigate the combined influence of these parameters on the accuracy andstability of the frequency standard. The second area is the detailed examination of the noisebudget of the frequency standard (broadening, shifts and drifts) and tracing their sources.