LIGO diary--report #8 (final)

by Wm. Robert Johnston
last updated 1 August 2001

Saturday, 28 July 2001: This will wrap-up my reports from LIGO. I am back in Brownsville now, and will soon have pictures from my trip uploaded to my web site. At Johnston's Archive go to the section on Relativistic physics. The LIGO diary section compiles these periodic reports with corrections and will include some pictures.

I was unfortunately unable to further the data entry mentioned earlier. It turned out, due to an error on my behalf, the computer declined to accept my entries. (As HAL-9000 once said, "These things have happened before, and they have always been attributable to human error.") Additionally, we discovered some additional bugs in the system so the data entry effort was put on hold.

Regarding the seismic noise issues I mentioned previously: the mirrors are isolated from the ground by a series of multiple levels of springs and suspensions. This combination greatly minimizes the effects of seismic ground shaking for the frequencies where LIGO is looking for gravitational waves. It does somewhat increase shaking for some much lower frequencies (such as 2 Hertz, or 2 cycles per second). Unfortunately, human activity in the neighborhood of LIGO-Livingston is producing 2 Hertz seismic noise at sufficient levels to cause "loss of lock." In other words, it indirectly causes a problem by shaking the mirrors enough that the automatic adjustment system loses track of where the mirrors are, and thus can't maintain their positions. A principal part of the current plan will increase the ability of the system to overcome larger shaking.

Friday night I had dinner with someone I met in Hammond who works for the Louisiana Department of Environmental Quality in its radiation control section.

Saturday we came back to Brownsville, passing through some rain between Louisiana and Houston. Vickey and I were glad to see each other.

© 2001 by Wm. Robert Johnston.
Last modified 1 August 2001.
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