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LIGO Livingston Observatory NewsPower and Network Installed at LLO-TriNet Vault
Installation Continues (Again!) at Livingston
The basic infrastructure installation for the LIGO Livingston Observatory TriNet (LTL) seismic station was finished at the end of June. The contractors did a nice job laying down the optical fiber between the X end-station and the X 3-km point and the vault. They installed a step-down transformer and provided us with two 110V outlets at the X 3-km mark. They also tested and neatly terminated the six fiber connections between the X 3-km mark and the end-station, as well as six additional fibers to the vault. The full electrical and networking layout is shown in detail in the three .pdf diagrams shown here: Figure 1 (schematic), Figure 2 (cross-section), and Figure 3 (top-view).
As soon as the contractor finished the testing and released the installation to the laboratory, we began to set-up our networking equipment and battery backup power system for the vault and beam tube. As it should in an ideal world, our network connection was up and running promptly after the installation of the media converters and network hubs. By Thursday evening we could access the internet from the beam tube as well as from the vault. The battery and charger installation, which provides power to the vault, was also a smooth job. By Friday morning we had a live network and stable DC power available. After a little R&R (rest and rehydration) we moved, installed and rebooted the seismic system at its new place in the vault. Again, this preliminary installation was a straightforward job and we had the station up and running slightly ahead of the usual afternoon thunderstorm. It was a good day's work and an encouraging start, but we still have plenty to do before finishing the installation to our full satisfaction.
The Louisiana Tech and SURF students who worked with me on this project showed great interest in the installation and preliminary commissioning of the vault. And I was quite happy to receive any help I could get, so I decided to involve the students closely in the installation process (see the "photo gallery" below). The students built the test arrangement for the networking setup, using the ethernet to multimode fiber converters. They tested every element of the chain in the lab. They took part in the networking installation. They helped to disassemble and reassemble the seismic equipment, and also assisted in bringing up the system. It was an excellent exchange: LIGO benefited with a speedy installation of its equipment, and the students got a taste of several new fields, learning a great deal along the way.
Acknowledgments: We would like to take this opportunity to thank Rusyl Wooley, Fred Asiri and Gerry Stapfer for their effort, persistence and supervision of the contractors, which made possible the finish of the civil engineering and basic electrical infrastructure; also Shourov Chatterji for his nice drawings and magnetometer system; and finally the students for their enthusiastic help.
Below: Picture gallery of preliminary installation with the students: (Top row) At left, Clay Westbrook of Louisiana Tech is ready to dive into the vault. Right, Hareem Tariq of Florida Tech, Misty Watson of Xavier University and Keisha Williams of Southern University follow the boot process of the Quanterra datalogger.
Above: (Bottom row) Left, Misty and Loniqe Coots of University of Texas enjoying the outdoor work. Center, I am getting well done inside the oven. Right, the students enjoy the breeze outside.
The Livingston four-kilometer interferometer has been undergoing a period of retrofitting since the middle of May. After running the interferometer and shaking down sub-systems for about six months, the list of fixes and upgrades became long enough to warrant venting the vertex and end station vacuum systems. Because any venting of the vacuum system allows water vapor to be absorbed on the inner surfaces of the chamber and within some hygroscopic components, it is best to limit the number of venting periods required (a bit like waiting to take your car in for repair until you have several items you want the mechanic to examine). Of course, the water vapor is again removed once the system is pumped down, but this takes time. And it can be a long time--several weeks or longer if the water vapor has built up extensively. During the vent period, the beam tube modules remain under vacuum, isolated from the vacuum spaces where the test masses are located by gate valves at either end of both 4-km long arms.
At right above: A view of the Laser and Vacuum Equipment Area (LVEA) while undergoing installation. The large vacuum chamber that contains the beamsplitter is covered by a clean room to prevent contamination from room dust. Also note the theodolite in the center-right area--this will be used to check the alignment of the optics.
One of the most important changes to the interferometer has been the swapping out of old OSEMs (an integrated optical position sensor and electromagnetic actuator used in damping the mirror pendulum motion) with an improved version that is less sensitive to scattered light. Also, during our commissioning activities of the last six months, we discovered several in-vacuum wiring problems needing repair and some optics that had to be realigned. This has involved going into the vented vacuum system and replacing components in situ. In some cases, the entire optical assembly had to be removed from the vacuum chamber and reworked in the optics lab facility. This work has been progressing on schedule and should be completed shortly.
Below: At left, graduate student Rana Adhakari works on the HAM1 vacuum chamber. Right, a view of one of the test masses. The cylindrical objects in the upper- and lower-right areas are the OSEM devices now being replaced.
We have also used this period to "re-layout" the optics on the Pre-Stabilized Laser Table. We now have the laser beam follow a shorter path on the table. This makes the laser light less susceptible to disturbance from acoustic noise since flexing of the laser table is one of the major contributors to the acoustic sensitivity.
When this work is completed, we will pump out the vacuum system and wait for the pressure of the newly-absorbed water vapor inside to fall to an acceptable level. We want the level low enough that it doesn't contaminate the beam tubes. This should occur sometime in August. Then, we can again open the gate valves to the 4-km arms and recommence commissioning the full LIGO interferometer.