Abstract
We recently demonstrated a Cryogenic Sapphire Oscillator (CSO) presenting a short term frequency stability better than 3 × 10−15 for 1 s≤ τ < 1000 s and achieving 4.5 × 10−15 for one day integration. This CSO incorporates a pulse-tube cooler instead of a bath cryostat-thus eliminating the need for regular supplies and manual transferring of liquid helium. The advent of reliable and cryocooled CSO open the possibility to implement such an ultra-stable reference not only in metrological laboratories with liquid helium facilities but also in remote sites like base stations for space navigation, VBLI antenna sites, …
Highlights
A growing number of scientific or technical applications requires ultra-high frequency stability signal sources
A Cryogenic Sapphire Oscillators (CSO) incorporates a cryogenic whispering gallery mode resonator made in sapphire which provides a Q-factor as high as 1 × 109 at 4.2 K
We recently validated in the frame of a European Space Agency research contract, an new instrument: ELISA based on a CSO operating in a specially designed cryocooler
Summary
A growing number of scientific or technical applications requires ultra-high frequency stability signal sources. A relative frequency stability better than 1 × 10−14 for integration time between 1 and 104 s is required for metrology, future space programs and some tests of fundamental physics [1, 2, 3]. These new requirements impose to surpass the performances of the state-of-the-art quartz crystal oscillators whose short term frequency stability is limited to around 1 × 10−13. It is planned to implement such oscillators in Deep Space Network ground stations to improve the tracking of space vehicules and in VLBI observatory for better data correlation For these last applications, the use of liquid helium is inconvenient and a change of technology is needed. The aim of this paper is to summarize the design, the fonctionnalities and performances of this CSO as well as the new projects leaded in our laboratory and related to this technology
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