| The LIGO
LIGO Livingston Observatory NewsShort Michelson Lock Achieved
Light in the Arms!
LIGO Educates INTECH Teachers
Hungarian Ambassador to the United States Visits LIGO
The LIGO Livingston Observatory has achieved another important milestone in the progression of tasks leading to a fully functioning interferometer. On Friday, January 19, we operated the laser, beam splitter, and input test masses (the suspended mirrors closest to the beam splitter along the arms) as a Michelson interferometer. We used the RF length sensing from the anti-symmetric (or "dark") port and demonstrated that we could lock on either a bright or a dark fringe. By using the RF length sensing, we were able to exercise the digital servo control of the mirror positions in order to maintain lock. We were pleased to see just how much contrast was obtained when we locked on a dark fringe, indicating that the mirrors are very well aligned.
The two images above show a video camera on which the anti-symmetric port beam profile is displayed. The view at left shows the beam profile with the locking servo enabled, while the right-side view shows the port beam profile with the servo disabled.
Repeated disconnection and reconnection of the servo resulted in repeated locks. Also, gradual decrease in the servo gain resulted in gradual degradation of the lock quality (more fluctuations in the light level at the AS port).
We are now busily attempting to lock a 4-km long arm as a Fabry-Perot cavity. Our first efforts are along the east-west direction (the "X-axis" of the interferometer) followed by similar studies to be done along the Y-axis.
On January third and fourth, light from LIGO's prestabilized laser was for the first time shone down the length of each four-kilometer long arm of the interferometer. The beam tubes, which contain the vacuum along the arms, had been isolated by large gate valves from the laser and optics since undergoing bake out last year. With all the optics now installed and aligned, and with the vacuum chambers at either end of the beam tubes now evacuated, the gate valves were at last opened so that light could travel the length of the apparatus. The mirrors which guide the light had been carefully installed and aligned inside the vacuum chambers to within about 30 micro-radians of their design values. When the arms were illuminated with this laser light, the laser beam was clearly visible to within about ten centimeters of its target on the mirror center without any additional adjustment of the mirror pointing. After centering the beams on the end mirrors, the reflected beam from the "Y" end mirror was easily visible on the Y input mirror and, after some adjustments, the "X" end reflected beam was also brought into alignment, making a spot on the X input mirror.
At left above is an image of the "X" end mirror. The optic can be seen in the center of the picture. It is dimly illuminated by the light sources within the position actuators (the "OSEM's") along its periphery. The laser beam is the bright spot centered in the top half of the image. It has been deliberately steered onto the ETM telescope support tube so as to be easily seen.
Then, at right, is an image of ITMx, the input mirror of the Fabry-Perot cavity along the "X" arm. The camera view is looking in the direction of the input laser beam. The input optic can be seen in the bottom half of the picture dimly illuminated by the positioning actuators. The return beam reflected from the end mirror is the bright spot centered in the top half of the image where it has been deliberately projected onto the optic's support structure, just above and to the left of the optic. (The vertical object to the right of ITMx is the beam splitter suspension structure.)
All in all it was a great way to start the New Year!
During the week of November 13 17, 2000, twenty-one teachers from Livingston Parish schools participated in an INTECH training program. INTECH instructs teachers on ways to incorporate technology in the classroom using a variety of methods.
As part of the training, the teachers were involved in a field trip to the LIGO facility in Livingston, Louisiana. Their purpose was to study gravity and understand how it shapes the universe. The LIGO facility in Livingston is the largest ground-based science observatory in the U.S., and is one of a duo of such installations, the other is located in Hanford, Washington. Funding for this gravity wave search comes strictly from grants provided by the National Science Foundation and is conducted in partnership with Caltech and MIT.
One of the goals of LIGO is to be a resource center for educators, students, parents, and the community. Dr. Mark Coles, head of the LIGO Livingston Observatory, says that a science museum is in the future construction plans. There is also a grant that will permit funding of a twenty-inch telescope which will be accessible to the public over the web, offering the ability to take pictures of stars and solar activity.
Also in the plans for the future is a 175-seat auditorium to house large groups for touring. LIGO is currently conducting tours for small groups and you can access that information from any of their websites, Livingston, Hanford, Caltech, or MIT.
There are many activities for small group involvement. Groups can experience first-hand what many have come from around the world to see. Several scientific models are on display for examining and hands-on manipulation. Also available is an observation deck so you can see the unique layout of the observatory. Groups can also paint murals on the outside of the long beam tube to leave their mark on LIGO.
Last October, the LIGO Livingston Observatory was host to four very eager visitors. The period of mid- to late-October is the time for harvest festivals in Hungary, a perfect occasion for people to get together and celebrate the abundant harvest of the year. This is the time for unspoiled fun and games, traditional dances, and of course an affluence of meals! The Hungarian settlers in Louisiana have preserved the ancient tradition of harvest gatherings for more than a century. The ancestors of this community found their new farms between present day Albany and Springfield, Louisiana (only about 15 miles from the Livingston site). The Harvest Festival serves as a way to preserve the traditional foods, dresses and values, and it is definitely fun!
Pictured at left: Dr. Géza Jeszenszky (in white shirt), his wife Edit Jeszenszky (white jacket), Dr. Stephen Gergatz (in dark suit), his wife Juli Bika (with red scarf) and myself in front of the laboratory after the tour.
The celebration usually takes place at multiple locations including the local Hungarian church, the dance room and of course the winery. The leaders of the local Hungarian community of "Árpádhon" always put great emphasis on the perfect organization, and it is customary to invite prominent Hungarian personalities and artists from Hungary, from other parts of the U.S., as well as people with Hungarian heritage from neighboring regions. This year the leader of the delegates from Hungary was Dr. Géza Jeszenszky, the present Hungarian Ambassador to the U.S. and former Minister of Foreign Affairs of the Republic of Hungary. Dr. Jeszenszky was a prominent member of the first freely elected Hungarian government (1990-94) after WWII.
Above: At left, the tour group enjoys the breathtaking view from the roof of the corner station. At right, a final view of us all before leaving the observatory.
My mention of LIGO to people at the festival roused a considerable amount of curiosity, and so I was induced to give a tour right away (Saturday evening before the dance). After learning about LIGO, the ambassador and his wife Edit modified their Sunday program to be able to visit the observatory. Dr. Stephen Gergatz, the Hungarian Consul to Louisiana, and his wife Juli Bika were also enthusiastic participants on the tour. During the close to three-hour long tour everyone expressed great interest and were quite inquisitive about our endeavors. They were also very impressed and pleased with the installations of the observatory and the physics goals of the enterprise. After the tour everyone specifically asked for literature about LIGO. Professor Jeszenszky, a teacher and scientist himself, was very interested and left the laboratory with a copy of Kip Thorne's book, Black Holes and Time Warps: Einstein's Outrageous Legacy. I received positive feedback from them after they returned to their posts, it seems they had a very enjoyable experience and will send more visitors to LIGO!