GeNS Mechanical Loss Measurement
Faculty Mentor Name
Andri Gretarsson, Ellie Gretarsson
Format Preference
Poster
Abstract
Gravitation waves are being observed at the Laser Interferometer Gravitational- Wave Observatory (LIGO). The sources from which LIGO detects gravitational waves are all fairly nearby compared to the size of the universe because instrument noise masks the faint signals from sources further away. Some of that instrument noise is due to the fact that the interferometer mirrors vibrate randomly--so-called Brownian motion. The characteristic that is most important in the evaluation of Brownian noise from mirrors is internal friction, also known as mechanical loss. If one causes the glass disk to vibrate, the vibration will eventually die out. By measuring the rate at which test mirrors "ring-down" we can estimate their mechanical loss and thereby predict how far out into the universe LIGO would be able to detect sources of gravitational waves if equipped with such mirrors. The apparatus required for such ring-down measurements consists of a small hemi-sphere of sapphire, silicon, or fused silica upon which the test mirror is balanced known as a Gentle Nodal Suspension or GeNS apparatus. Unfortunately, the mechanical loss measured by this apparatus is quite sensitive to the precise placement of the disk on the hemi-spherical balance point and we don't really know how far out of balance the disk can be before the measurement is biased. So, how does the mechanical loss in the samples depend on the placement of the samples on the support? We are investigating this issue by re-commissioning an existing GeNS apparatus and then intentionally moving the balance point of the sample on its suspension. We are setting up a system for careful measurement of the balance point location in order to do a systematic study of mechanical loss as a function of the balance point location. The results of this will give insight into how far out of balance the mirror can be before the results of the experiment the apparatus is used in are biased. This will help improve the understanding of the GeNS system under vacuum conditions and potentially improve methods of Brownian Noise reduction in various systems including the ones within LIGO.
GeNS Mechanical Loss Measurement
Gravitation waves are being observed at the Laser Interferometer Gravitational- Wave Observatory (LIGO). The sources from which LIGO detects gravitational waves are all fairly nearby compared to the size of the universe because instrument noise masks the faint signals from sources further away. Some of that instrument noise is due to the fact that the interferometer mirrors vibrate randomly--so-called Brownian motion. The characteristic that is most important in the evaluation of Brownian noise from mirrors is internal friction, also known as mechanical loss. If one causes the glass disk to vibrate, the vibration will eventually die out. By measuring the rate at which test mirrors "ring-down" we can estimate their mechanical loss and thereby predict how far out into the universe LIGO would be able to detect sources of gravitational waves if equipped with such mirrors. The apparatus required for such ring-down measurements consists of a small hemi-sphere of sapphire, silicon, or fused silica upon which the test mirror is balanced known as a Gentle Nodal Suspension or GeNS apparatus. Unfortunately, the mechanical loss measured by this apparatus is quite sensitive to the precise placement of the disk on the hemi-spherical balance point and we don't really know how far out of balance the disk can be before the measurement is biased. So, how does the mechanical loss in the samples depend on the placement of the samples on the support? We are investigating this issue by re-commissioning an existing GeNS apparatus and then intentionally moving the balance point of the sample on its suspension. We are setting up a system for careful measurement of the balance point location in order to do a systematic study of mechanical loss as a function of the balance point location. The results of this will give insight into how far out of balance the mirror can be before the results of the experiment the apparatus is used in are biased. This will help improve the understanding of the GeNS system under vacuum conditions and potentially improve methods of Brownian Noise reduction in various systems including the ones within LIGO.