Stan Whitcomb, Caltech
Construction continues to move forward rapidly at both LIGO sites (Hanford, Washington and Livingston, Louisiana). At the Hanford site, the civil construction at the site (buildings, roads, power) is nearing completion. At the Livingston site, the main activities are the construction of the buildings and the forming of the concrete foundation along the two arms on which the beam tubes will be installed.
The vacuum system is also moving forward. Chicago Bridge and Iron, the company building the LIGO beam tubes (which connect the vertex and ends of the two arms), has completed the fabrication and installation of all 8 km of beam tube at the Hanford site. The first two 2 km sections have been evacuated and are already at a pressure below torr. They have now moved their fabrication equipment to a facility near the Livingston site, and are starting to prepare for full production. Our contractor for the fabrication of the vacuum chambers and associated equipment which will be in the located in the buildings, Process Systems International, is nearing completion of all the large chambers and associated hardware for the Hanford site. Installation is expected to start in September.
The staffing of the sites is also starting; approximately 15 LIGO staff are located at the two sites, including Hanford Site Head Fred Raab, who recently moved there from Caltech.
The design of the LIGO detectors is accelerating, with the various detector subsystems split approximately 50-50 between the preliminary and final design phases. Fabrication has started for long-lead items including the test masses and other large optics. Approximately half of the fused silica blanks have been received with the remainder expected before the end of the year; General Optics and the Commonwealth Scientific and Industrial Research Organization are polishing these blanks in preparation for coating. Procurements are underway for a complete first article Seismic Isolation Stack to be built this fall with testing to start in the beginning of 1998.
Lightwave Electronics Corporation, under contract to develop a 10 watt single frequency Nd:YAG laser for LIGO, has completed the design and are starting fabrication of the first unit. An experimental unit used to test the performance of this new design met the key requirements for power, beam quality, frequency and intensity noise.
At MIT, a 5 m long suspended interferometer is being used to investigate the limits of optical phase measurements. This recycled Michelson interferometer operated initially with an Argon ion laser at 514 nm, and demonstrated a sensitivity of rad Hz. It has now has now been converted to operate with a Nd:YAG laser at 1064 nm. A detailed characterization of the noise in this new configuration will begin soon.
The initial meeting of the LIGO Scientific Collaboration (LSC) was held in Baton Rouge, Louisiana in August. The purpose of this meeting was to form a broader scientific effort to both develop the initial detectors and to pursue research leading to more sensitive future detectors. Twenty groups from five countries, representing a total of 201 collaborators were represented. The most important agenda items were to discuss a charter for the LSC and to form working groups on specific technical topics to coordinate the research efforts of different groups. Rai Weiss (MIT) was appointed as the first spokesperson for the collaboration. The next meeting of the LSC is scheduled for March 12-13 at the LIGO Hanford site.
Additional information about LIGO, including our monthly newsletter and information about the LSC, can be accessed through our WWW home page at http://www.ligo.caltech.edu.