What's new in LIGO

David Shoemaker, LIGO-MIT dhs-at-ligo.mit.edu
There has been broad progress in LIGO over the last six months. One first note on the Livingston Observatory, which was in the path of Hurricane Katrina. The observatory staff are all safe. The site is sufficiently inland that the worst of the wind and water damage was avoided, although a building panel was ripped off, debris thrown around, and the power lost for a period of time. At the time of writing, it is being brought back to operational condition, and no obvious significant damage was done.

At the time of the last MOG, we were anticipating the fourth science run (S4). It took place as planned, and the bottom line is that the detectors worked very well. They worked with high sensitivity and duty cycle (thanks to the successful implementation of the hydraulic `HEPI' pre-isolation system at Livingston). Diagnostic tools, looking at the state of the instruments and the quality of the data, were running in full force, giving feedback to the operators and science monitors to watch for problems and allow tuning for the highest quality of data.

A handful of papers from earlier science runs have now been submitted. Since the last MOG, such bodice-rippers as ``Search for gravitational waves from galactic and extragalactic binary neutron stars'', ``Search for Gravitational Waves from Primordial Black Hole Binary Coalescences in the Galactic Halo'', ``Upper limits from the LIGO and TAMA detectors on the rate of gravitational-wave bursts'', ``Upper limits on gravitational wave bursts in LIGOs second science run'', and ``Upper Limits on a Stochastic Background of Gravitational Waves'' have hit the gr-qc newstand. The last paper puts the exciting upper limit of $\Omega_{gw}(f)<8.4\times 10^{-4}$ in the band of frequencies from 69-156 Hz, an improvement of some $105$ in the limit at those frequencies. We are still catching up on the data collected, and are working hard on the very nice recent S4 data. Einstein@home, described in the last MOG, has been a resounding success. It is providing roughly 20 Teraflops of computing power and is working away at searches for periodic sources, like pulsars, over broad sections of the sky. Please consider donating your spare cycles to http://einstein.phys.uwm.edu.

Detector commissioning has continued with great success. On all instruments, the core of the progress has been in increasing the laser power. This pushes down the noise in the shot-noise limited region, but equally importantly gives better signal-to-noise in many auxiliary channels. In the case of the Livingston instrument, better alignment control was needed, and achieved, to handle this power. The 4km instrument at Hanford had shown excessive absorption in several optics, and careful sleuthing showed that one of the input optics of a 4km Fabry-Perot cavity was the prime suspect. A foray into the vacuum system was made to switch out that optic, and to clean another. This gave a factor of (at least) ten reduction in absorption, paving the way for useful increases in power for this instrument. The 2km instrument at Hanford also was tuned up, and variety of other optical, mechanical, and controls aspects of the interferometers have been addressed in parallel. The instruments have now all performed effectively at their design sensitivity, and the Collaboration has decided to proceed with the main initial LIGO S5 Science Run, designed to collect a year of integrated data, planned to start late this year.

Advanced LIGO design and prototyping continues apace. A full-size prototype, from Caltech and UK design teams, of the quadruple test mass suspensions has just been assembled. The seismic isolation prototype at Stanford's test facility has demonstrated design performance in many aspects, and we are now moving forward on the prototype for the test mass chambers. Work has been done at MIT on characterizing the seismic interface and at Caltech on alternative designs for the auxiliary optics `HAM' chambers. Along with technical progress on the laser at the Max-Planck Institute in Hannover, funding for supplying the pre-stabilized lasers for Advanced LIGO has now been assured. The good technical progress allows us to be ready for and optimistic about a 2008 start of funding for Advanced LIGO from the National Science Foundation.

One important evolutionary change is underway: The reorganization of the LIGO Laboratory and the LIGO Scientific Collaboration (LSC). The two are becoming one organization - referred to simply as 'LIGO' - as a recognition of the crucial role that the LSC plays in the development and exploitation of the Observatories. Individuals from the LSC are taking on central organizational roles, exemplified by the addition of the LSC spokesperson to the leadership group of the LIGO Director and Deputy Director. The LSC is also participating fully in the search for a new Director, as Barry Barish has been asked to take on the leadership of the global design effort for the international linear collider. We will miss his leadership; fortunately he will remain as an active member of the LSC. We are also moving to bring our close international partners into the organization; re-writing the LSC Charter and Bylaws; and generally adjusting to the reality that we have a set of running detectors, with a mature data analysis process, and an Advanced LIGO upgrade which is starting to take on a life of its own.

Jorge Pullin 2005-10-05