Recent LISA studies at the University of Colorado

We report on LISA experimental projects being pursued at JILA. Our focus is on the design and testing of a flight-compatible laser stabilization reference cavity. This is a dual cylinder ULE cavity, designed to provide high thermal and thermo-mechanical isolation in the millihertz frequency regime of interest to LISA. A modification of this hard-mounted design may allow for use in space without the need for clamping during launch. Progress so far consists of initial design, performance estimates, and construction. Simple thermal model calculations on the design indicate a thermal attenuation of 106 at 1 mHz, corresponding to a cavity strain of 3*10-16 /rtHz for a 0.01 K/rtHz stability of the mounting surface. Finite element analysis indicates cavity strain attenuation of 5*107 or better due to thermo-mechanical effects in the surrounding environment, and low sensitivity to vibration along the cavity axis. Setup and testing of two identical cavities and a laser-locking test system is ongoing. Another project was recently concluded, testing the low-frequency stability of commercial voltage references. Voltage reference performance is relevant to the stability of electrically applied forces on the LISA proof masses, and commercial references do not have well characterized noise in the sub-Hz regime. Our measurements confirmed that the best commercial reference was the AD587LN, with a typical noise of 2.1±0.6 ppm/rtHz at 0.1 mHz, in a temperature-stabilized environment of ∼10mK/rtHz. This agrees closely with prior work by other groups.