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
in the band of frequencies from 69-156 Hz, an improvement of some
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