Microwave interrogation cavity for the rubidium space cold atom clock

Abstract

The performance of space cold atom clocks (SCACs) should be improved thanks to the microgravity environment in space. The microwave interrogation cavity is a key element in a SCAC. In this paper, we develop a microwave interrogation cavity especially for the rubidium SCAC. The interrogation cavity has two microwave interaction zones with a single feedin source, which is located at the center of the cavity for symmetric coupling excitation and to ensure that the two interaction zones are in phase. The interrogation cavity has a measured resonance frequency of 6.835056471 GHz with a loaded quality factor of nearly 4200, which shows good agreement with simulation results. We measure the Rabi frequency of the clock transition of the rubidium atom in each microwave interaction zone, and subsequently demonstrate that the distributions of the magnetic field in the two interaction zones are the same and meet all requirements of the rubidium SCAC.

In-orbit operation of an atomic clock based on laser-cooled 87Rb atoms

“…The main part of the physics package is a titanium alloy vacuum tube for which a vacuum is maintained to better than 1 × 10 −7 Pa 30 . A ring cavity inside the vacuum is used for the Ramsey interrogation of the cold atoms 31 . Three layers of Mumetal are used to shield the magnetic field in the interrogation cavity, with only one layer shielding the capture zone.…”

State Preparation in a Cold Atom Clock by Optical Pumping

“…1. The device consists of an MOT chamber, a state selection microwave cavity, an optical pumping chamber, a ring microwave cavity [12] (Ramsey cavity), and a top detection chamber, from bottom to top. Since there is no suitable window for optical pumping at the MOT, our optical pumping chamber is constructed from the pre-vious lower detection chamber and inherits its standing wave condition.…”

Development of a space cold atom clock

“…Different from the fountain clock on ground, the SCAC’s Ramsey cavity must satisfy the conditions to operate in microgravity, in which the launched cold atoms move at constant velocity. To meet this demand, a dual-interaction zone interrogation cavity was developed [ 28 ]. The principle of the cavity is similar to that for cesium atoms in the ACES mission [ 12 ], but with different guidance structure.…”

“…The microwave field is fed in from a hole on the coupled waveguide, and propagates in two opposite directions and finally forms a standing wave field, which was simulated and tested thoroughly, as discussed in Ref. [ 28 ].…”