arXiv subjects

John Miller

Publications and source records attributed to John Miller.

43 records · Page 3Linked to original sources

arXiv2015

Thermal noise of gram-scale cantilever flexures

We present measurements of thermal noise in niobium and aluminium flexures. Our measurements cover the audio frequency band from 10Hz to 10kHz, which is of particular relevance to ground-based interferometric gravitational wave detectors, and span up to an order of magnitude above and below the fundamental flexure resonances at 50Hz - 300Hz. Our results are well-explained by a simple model in which both structural and thermoelastic loss play a role. The ability of such a model to explain this interplay is important for investigations of quantum-radiation-pressure noise and the standard quantum limit.

physics.ins-det↗

arXiv2015

Observation of Parametric Instability in Advanced LIGO

Parametric instabilities have long been studied as a potentially limiting effect in high-power interferometric gravitational wave detectors. Until now, however, these instabilities have never been observed in a kilometer-scale interferometer. In this work we describe the first observation of parametric instability in an Advanced LIGO detector, and the means by which it has been removed as a barrier to progress.

astro-ph.IM↗

arXiv2014

Prospects for doubling the range of Advanced LIGO

In the coming years, the gravitational wave community will be optimizing detector performance for a variety of astrophysical sources that make competing demands on the detector sensitivity in different frequency bands. In this paper we describe a number of technologies that are being developed as anticipated upgrades to the Advanced LIGO detector, and quantify the potential sensitivity improvement they offer. Specifically, we consider squeezed light injection for reduction of quantum noise, detector design and materials changes which reduce thermal noise, and mirrors with significantly increased mass. We explore how each of these technologies impacts the detection of the most promising gravitational wave sources, and suggest an effective progression of upgrades which culminate in a factor of two broadband sensitivity improvement.

gr-qc↗

arXiv2014

Length control of an optical resonator using second-order transverse modes

We present the analysis of an unorthodox technique for locking a laser to a resonant optical cavity. Error signals are derived from the interference between the fundamental cavity mode and higher-order spatial modes of order two excited by mode mismatch. This scheme is simple, inexpensive and, in contrast to similar techniques, first-order-insensitive to beam jitter. After mitigating sources of technical noise, performance is fundamentally limited by quantum shot-noise.

physics.optics↗

arXiv2013

Magnetic fields in Accretion Discs around Neutron Stars - Consequences for the change of spin

Accretion disks are ubiquitous in the universe and it is generally accepted that magnetic fields play a pivotal role in accretion-disk physics. The spin history of millisecond pulsars, which are usually classified as magnetized neutron stars spun up by an accretion disk, depends sensitively on the magnetic field structure, and yet highly idealized models from the 80s are still being used for calculating the magnetic field components. We present a possible way of improving the currently used models with a semi-analytic approach. The resulting magnetic field profile of both the poloidal and the toroidal component can be very different from the one suggested previously. This might dramatically change our picture of which parts of the disk tend to spin the star up or down.

astro-ph.SR↗

arXiv2013

Constructing a Multiple-Choice Assessment For Upper-Division Quantum Physics From An Open-Ended Tool

As part of an ongoing investigation of student learning in upper-division quantum mechanics, we needed a high-quality conceptual assessment instrument for comparing outcomes of different curricular approaches. The 14 item open-ended Quantum Mechanics Assessment Tool (QMAT) was previously developed for this purpose. However, open-ended tests require complex scoring rubrics, are difficult to score consistently, and demand substantial investment of faculty time to grade. Here, we present the process of converting open-ended questions to multiple-choice (MC) format. We highlight the construction of effective distractors and the use of student interviews to revise and validate questions and distractors. We examine other elements of the process, including results of a preliminary implementation of the MC assessment given at Cal Poly Pomona and CU Boulder.

physics.ed-ph↗

arXiv2011

Arm-length stabilisation for interferometric gravitational-wave detectors using frequency-doubled auxiliary lasers

Residual motion of the arm cavity mirrors is expected to prove one of the principal impediments to systematic lock acquisition in advanced gravitational-wave interferometers. We present a technique which overcomes this problem by employing auxiliary lasers at twice the fundamental measurement frequency to pre-stabilise the arm cavities' lengths. Applying this approach, we reduce the apparent length noise of a 1.3 m long, independently suspended Fabry-Perot cavity to 30 pm rms and successfully transfer longitudinal control of the system from the auxiliary laser to the measurement laser.

physics.ins-det↗