Dr. Jeff Kissel gave updates on progress made with LIGO sites
On Nov. 14, 2019, Dr. Jeff Kissel, the Controls Engineer of the Laser Interferometer Gravitational-Wave Observatory (LIGO) at the Hanford Site in Washington State, spoke to the Embry-Riddle family about what had occurred at the various LIGO sites across the world and other similar observational detectors. LIGO had a massive role in the Embry-Riddle Physics Department as many professors and students did research alongside prestigious and well-regarded staff like Kissel.
The LIGO sites are observatories that use laser interferometry to detect cosmic gravitational waves of binary systems colliding which requires months and months of recording “noise” out in the depths of space. The “noise” that the detectors record is the ripple in space-time of gravitational waves propagating after massive astronomical bodies merge.
Kissel mentioned that the sensitivity of the detectors was poor in the early stages the observational runs. After each run or when they had a break in the observing process, funds would be allocated between the Hanford Site in Washington and the Livingston Site in Louisiana to optimize any sensors, test masses, mirrors, and numerous other finely tuned instruments that they could afford to fix in such a time crunch and their limited money supply.
According to Kissel, just by “improving the sensitivity by a factor of two, the volume of the detectable sources increases by a factor of eight causing the event rate to skyrocket” which justified the blood, sweat and tears he and his colleagues put into the betterment of the knowledge of what lies beyond this solar system. He proved that with seemingly minor adjustments to the systems to refine the sensitivity, improvements in the recorded data occurred everytime without fail.
Kissel described the four most crucial areas that were adjusted as the effects of a cooling system that interrupted data, replacement of half of the tested masses that were from the first observational run, use of developments in quantum mechanics to modify the noise of the laser light emission, and prevention of stray light from entering the interferometer.
The cooling system was for a 180-watt system that created too much noise while running that it interfered with data collection. The fix was to “downgrade to a cooling system for a smaller wattage capacity which was not dramatic to the retrieving data process because they only really inject 20-50 watts finto the interferometer,” claimed Kissel. The test masses were replaced between observational run two and observational run three because the optics had been improved. The improvements in quantum mechanics allowed for the increase of noise in amplitude yet a decrease of noise in phase of the wave properties by modifying the light as it exited the system. As for stray light, the interior was covered in a dark black material with minimal holes for the intended light to pass through and “to prevent light from scattering or bouncing off less seismically isolated things,” said Kissel.
These enhancements made data on astronomical events exponentially rise and Kissel confirmed that refinement during a break in October 2019 produced better sensitivity along with more events that could become visible. The LIGO team has projections into what their fifth observational run of what the data would be like if these trends keep because they are confident in their findings and the National Science Foundation is pressuring them to keep up the good results. For LIGO, their research is only beginning, but it is already fruitful and very noisy.