LIGO Project update

David Shoemaker, LIGO-MIT

The Hanford (Washington) and Livingston (Louisiana) LIGO sites are now really the centers of activity for the LIGO Laboratory. The buildings and infrastructure are complete, and both permanent and visiting staff are rapidly on the rise.

The physical installation of the beam tubes is now complete, with all 8km accepted at Hanford, 4km accepted at Livingston, and only 4km to go. The LIGO Lab has started the Hanford ``bakeout'' in which lengths of the over 1m stainless steel diameter tube is heated by passing current through it ( works!) to drive out residual gas; this is a huge undertaking, with monstrous power supplies, cabling, and power sub-stations which travel from arm to arm and then to Livingston as we bake out the beam tube by 2km sections.

The vacuum equipment which houses the detector itself is now all on-site and in various stages of installation and testing. There are some complications with the large gate valves which segment and separate the beam tube from the vacuum equipment, with research into rubber and bellows and the usual details that make up the whole. This may delay the availability of the entire vacuum system, but there is lots to do that is independent and no significant impact on LIGO's turn-on is anticipated.

Several exciting milestones for the detector have taken place over the last half-year. The seismic isolation stack first article was installed and tested, allowing checks of the fit of the components and a verification of the filtering of seismic noise. Some lessons were learned both in the process of the installation and some manufacturing details which can now be applied to the whole series of isolation systems to follow. The manufacture of the series isolators, and the installation of the structures, is now underway at Hanford.

Another exciting step is the appearance of the Pre-Stabilised Laser equipment (and team!) at the Hanford site. The laser, which has already been built up and tested at Caltech, will be resurrected after shipping over the next few months, and will be turned on this fall.

Many other parts of the detector are turning from dreams into hardware, with optics, suspensions, coupling telescopes, mode-cleaning cavities, and servo systems all deep into fabrication. High-speed computer backbones are running at Hanford. The first integration of multiple subsystems will take place in Fall 98, with light coupled from the Laser into the Input Optics system which the University of Florida is delivering and installing.

The MIT LIGO Lab has moved, in July, from its familiar and favorite quarters in ramshackle Building 20 to a sparkling new space in NW17; it is equipped with a beautiful high-bay space (for a to-be-installed full-scale test interferometer), clean-room air everywhere, and (can you imagine it) carpeting on the office floors. Not so many mice, or much ``charm'', yet, but a very nice space. The Systems Integration effort including the data analysis group at Caltech has moved also into new quarters in the thin air at the top of the Millikan Library.

Research and Development for the initial detector is finishing up. The work on fringe-splitting at MIT concluded with a test of a digital servo-loop, confirming our ability to control and perform diagnostics with the required dynamic range. At Caltech, the 40m interferometer is allowing tests of alignment and acquisition systems and models.

Research for the next phase of LIGO is heating up. The LIGO Science Collaboration (LSC) now has significant momentum, and planning for data analysis of the initial LIGO run and for the hardware improvements slated for some five years from now are well underway. The last meeting of the LSC, in August, was held at JILA in Boulder, Colorado; the next meeting is to be held at the University of Florida in March '99.

Our schedule calls for shakedown of the interferometers starting in mid-'99, and operation in 2001. Additional information about LIGO, including our newsletter and information about the LSC, can be accessed through our WWW home page at

Jorge Pullin
Mon Sep 7 17:37:02 EDT 1998