Investigations into the effects of electrostatic charge on the Q factor of a prototype fused silica suspension for use in gravitational wave detectors

Abstract

This paper describes some investigations into the construction of a monolithic fused silica test mass suspension for use in interferometric gravitational wave detectors. We summarize results showing that the material Q factor of standard fused quartz in the form of ribbons is of a level which makes it suitable for use as a suspension material for the test masses of long baseline gravitational wave detectors and then present measurements of the Q factor of the pendulum mode of a non-conducting mass suspended on cylindrical fibres of fused quartz. Our results show that electrostatic charging of the mass can result in a significant decrease in the pendulum mode Q factor.

Discharging fused silica test masses with ultraviolet light

“…Charging is a potentially limiting noise source for both gravitational-wave interferometers [1][2][3] and other precision measurements of gravitational effects [4,5]. At the Laser Interferometer Gravitational-Wave Observatory (LIGO) [6], charge may build up on the surface of suspended fused silica test masses.…”

Challenges in thermal noise for 3rd generation of gravitational wave detectors

“…Thermoelastic damping [37] in the context of thin flexing fibres is an important factor in considering the design of suspension elements, and this will be discussed later [38][39][40]. In 1999, Braginsky et al [27] have pointed out that temperature fluctuations near the laser beam spot result in random fluctuations of the mirror surface.…”

Charge measurement and mitigation for the main test masses of the GEO 600 gravitational wave observatory

“…Having charged-up test masses is not only bad from the point of view of noise [5][6][7][8], but it also has a strong effect on the actuation strength of electrostatic actuators which, in the case of GEO 600, means a change in the gain of the Michelson longitudinal servo, and, perhaps more importantly, a change to the absolute calibration of the main GW output which assumes constancy of the ESD actuation strength over periods of several months (after initial calibration to another reference [9]). …”