The 111-120th REM talks

The 113nd REM: Febrary 28th, 2023, Tuseday

Time: 17:00-18:00

Speaker: Kohei Yamamoto (AEI)

Title: "LISA metrology system: Clocks, ranging, and communication"

Abstract:

The Laser Interferometer Space Antenna (LISA) aims to observe gravitational waves in the mHz regime over its 10-year mission time. LISA will operate laser interferometers between three spacecraft. Each spacecraft will utilize independent clocks, which determine the sampling times of onboard devices called phasemeter to extract the interferometric phases and, ultimately, gravitational wave signals. To suppress limiting laser frequency noise due to time-varying unequal arm lengths, phase signals sampled by each phasemeter must be combined in postprocessing to synthesize virtual equal-arm interferometers with the technique called time-delay interferometry (TDI). The synthesis, in turn, requires a synchronization of the independent clocks in postprocessing. For such on-ground data analysis, additional onboard measurements will be introduced on top of primary phase extractions: intersatellite clock-tone transfer and absolute ranging. The ranging technique also enables intersatellite data communication to ease communication between a ground station and LISA. This talk introduces recent experimental studies of these technologies using a hexagonal optical testbed at AEI Hannover.

The 111th REM: January 26th, 2023, Thursday

Time: 11:00-12:00

Speaker: Hiroki Fujimoto (UTokyo)

Title: "Axion dark matter search with laser interferometry"

Abstract:

Researches on cosmology and astrophysics have revealed that more than 80% of the matter in the universe consists of an unknown substance, or dark matter. The nature of dark matter is still unknown and many searches have been conducted for various dark matter candidates. Axion-like particles (ALPs) are undiscovered particles that are well-motivated candidates for ultralight dark matter. The interaction between ALPs and photons slightly causes the rotational oscillation of linearly polarized light, and therefore ALP dark matter can be detected by the measurement of the polarization rotation of a laser beam.
Recently, some ALP dark matter search experiments using the laser interferometer have been proposed. The basic idea is to use an optical cavity, which can enhance the effective light path and also the duration of the interaction with the ALP dark matter. With this technique, the polarization rotation can be amplified and high-sensitive ALP dark matter search can be conducted.
In this talk, I will introduce our interferometric ALP dark matter search experiment: DANCE and the search using the gravitational wave detectors.