arXiv subjects

R. Bork

Publications and source records attributed to R. Bork.

77 records · Page 5Linked to original sources

arXiv2008

Beating the spin-down limit on gravitational wave emission from the Crab pulsar

We present direct upper limits on gravitational wave emission from the Crab pulsar using data from the first nine months of the fifth science run of the Laser Interferometer Gravitational-wave Observatory (LIGO). These limits are based on two searches. In the first we assume that the gravitational wave emission follows the observed radio timing, giving an upper limit on gravitational wave emission that beats indirect limits inferred from the spin-down and braking index of the pulsar and the energetics of the nebula. In the second we allow for a small mismatch between the gravitational and radio signal frequencies and interpret our results in the context of two possible gravitational wave emission mechanisms.

astro-ph↗

arXiv2001

Readout and Control of a Power-recycled Interferometric Gravitational-wave Antenna

Interferometric gravitational wave antennas are based on Michelson interferometers whose sensitivity to small differential length changes has been enhanced by adding multiple coupled optical resonators. The use of optical cavities is essential for reaching the required sensitivity, but sets challenges for the control system which must maintain the cavities near resonance. The goal for the strain sensitivity of the Laser Interferometer Gravitational-wave Observatory (LIGO) is 10^-21 rms, integrated over a 100 Hz bandwidth centered at 150 Hz. We present the major design features of the LIGO length and frequency sensing and control system which will hold the differential length to within 5 10^-14 m of the operating point. We also highlight the restrictions imposed by couplings of noise into the gravitational wave readout signal and the required immunity against them.

physics.ins-det↗

arXiv2001

An Overview of the LIGO Control and Data Acquisition System

The LIGO Control and Data system (CDS) features a tightly coupled and highly integrated control and data acquisition system. Control of the interferometers requires many Multiple Input Multiple Output (MIMO) control loops closed both locally and across the 4-kilometer interferometer arm lengths. In addition to providing the closed loop control, the control systems front end processors act as Data Collection Units (DCU) for the data acquisition system. Data collected by these front ends and the data acquisition system must be collected and time stamped to an accuracy of 1 microsecond and made available to on-line analysis tools such as the Global Diagnostics System (GDS)[1]. Data is also sent to the LIGO Data Analysis System (LDAS)[2] for long-term storage and off-line analysis. Data rates exceed 5 Mbytes per second per interferometer continuous. Connection between the various front end processors and the data acquisition system is achieved using fiber optic reflective memory networks. Both controls and data acquisition systems use VME hardware and VxWorks operating systems. This paper will present an overview of the LIGO CDS and discuss key aspects of its design.

physics.ins-det↗

arXiv2001

The LIGO Interferometer Sensing and Control System

The LIGO Interferometer Sensing and Control System (ISC) is a large and highly distributed Multiple Input Multiple Output (MIMO) control system that is used to control the length and alignment degrees of freedom of the interferometers. The 4 kilometer Fabry-Perot cavity lengths are controlled to better than 10-13 meters (rms) and the angular degrees of freedom are controlled to better than 10-8 radians. This paper will describe the real-time digital servo control systems that have been designed, developed and implemented for the LIGO Length Sensing and Control (LSC) [1] and Alignment Sensing and Control (ASC) [2] systems. In addition, the paper will describe how these controls, along with the suspended optic controls [3], have been integrated into the overall LIGO control and data acquisition system [4].

physics.ins-det↗

arXiv2001

The LIGO Suspended Optic Digital Control System

The original LIGO suspension control system [1] used analog circuitry to implement the closed loop damping required for local control of each the suspended optics. Recent developments in analog to digital converters (ADC), digital to analog converters (DAC), increased processor speed and performance, and the use of reflective memory have made a digital alternative possible. Such a control system would provide additional performance and flexibility that will be required for operation of the interferometers. This paper will describe the real-time digital servo control systems that have been designed, developed and implemented for the LIGO suspended optics. In addition, the paper will describe how the suspension controls have been integrated into the overall LIGO control and data acquisition systems [2].

physics.optics↗