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LASTI Installation Accelerating as Equipment and Visitors Descend on MIT Lab

LASTI Installation Accelerating as Equipment and Visitors Descend on MIT Lab

- Contributed by Mike Zucker

The LIGO Advanced System Test Interferometer (LASTI) at MIT was conceived as a testbed for advanced LIGO systems, complementing our other facilities like the 40-meter interferometer at Caltech. LASTI's forte is testing full-scale (i.e., really really big) mechanical systems, like the seismic isolation and test mass suspensions that will isolate advanced LIGO optics from sound and vibration. LASTI can also exercise full-sized optical systems like the advanced LIGO laser and mode cleaner cavity, an important check to ensure we have no surprises in the advanced LIGO upgrade.

To accomplish this, the LASTI vacuum envelope is made of the same types of chambers installed at the LIGO Livingston and Hanford Observatories (except for beam tube length, of course!). A custom high-bay laboratory with dual-hoist bridge cranes and cleanroom air conditioning was carved out of MIT's Building NW-17 to house the system back in 1997.

LASTI vacuum envelope.

Above: The LASTI vacuum envelope shortly after installation in the MIT high bay lab. One of the arms with its two Horizontal Access Module-type chambers is shown; the second arm extends 16 meters left of the vertical Beam Splitter-type (BSC) chamber shown in the background. For scale, this chamber stands about 18 feet high and is 9 feet across.

Last fall we successfully commissioned the vacuum envelope, certifying the machine was leak-free and clean to ultrahigh vacuum standards. This winter we installed softwall cleanrooms over two of the chambers and (with help from LIGO Hanford experts Hugh Radkins and Corey Gray) installed the basic seismic isolation support systems, which are identical to those at the observatories and will be shared by the Advanced LIGO retrofit. We also installed a current-LIGO model isolation stack in one of the chambers to support a test cavity, which will be used to commission our laser system this summer.

Below: Hanford's Corey Gray gloats over successful installation of the HAM seismic isolation stack in the midpoint chamber on LASTI's south arm.

Corey Gray.

Our next step will be to mount the seismic supports and isolation bellows in the remaining BSC-type chamber at the vertex. Experts from LIGO Livingston will fly up to help us with this phase of the installation later this month. We're also awaiting arrival of a custom cleanroom for the BSC designed by LASTI chief engineer Ken Mason. This cleanroom is designed to fit our lab (which is of course much tighter than the observatory vacuum equipment areas) and will have an integrated work platform on its roof, rather than the separate bolt-on work platforms used at the observatories. It's also designed to support the new "cartridge installation" concept for the advanced isolation and suspension systems. This concept allows rapid and contamination-free replacement of the entire chamber contents with minimal personnel access required inside the chamber (could this mean the end of the bunnysuit photo op?).

Gregg Harry.

Above: Physicist Gregg Harry wades in a sea of parts and tooling prestaged for installation of the seismic support structure in the LASTI BSC chamber (background).

We have received small optics suspensions for steering and initial laser characterization from Janeen Romie Hazel's suspension factory. We're also receiving mountains of prestabilized laser components, VME instrumentation and data acquisition electronics prepared by Peter King, Rich Abbott, Rick Karwoski, Jay Heefner, Rolf Bork, Ben Abbott and others at Caltech and shipped to us in kit form for integration at MIT. With the imminent arrival of the laser itself any day now, things are really starting to get interesting!