September 13, 2019

F.M. Walter: the Dark Side of the Sun

The Sun, a perfectly ordinary middle-aged intermediate mass star, is absolutely critical for life as we know it on Earth. Essentially all the energy we, and all life, has to work with comes from the Sun. Nothing the Sun has done in the past 4 billion years has wiped out life on Earth. But today human technology threatens to bring us into direct conflict with less-appreciated aspects of Solar behavior.

Solar magnetic activity causes sunspots and heats the chromosphere and corona. Recombining magnetic fields cause solar flares, solar proton events, and coronal mass ejections (CMEs). When these reach the Earth, they cause the spectacle of the aurorae (the Northern and Southern Lights). These phenomena have endangered astronauts and destroyed satellites. CMEs play havoc with the power grid, and there is an uncomfortably-high probability that in the near future a large CME will bring down the North American power grid, with catastrophic consequences.

I will review the spectacle of Solar magnetic activity, what we know of the history of Solar magnetic activity, and lay out the case that modern civilization is inadequately prepared for these new threats.

Prof. Walter, a resident of East Setauket, studies star birth, stellar weather (including stellar coronae), and star death using the Chandra and XMM-Newton X-ray observatories, the Hubble Space Telescope, and telescopes in Arizona, Hawaii and Chile. He has been a professor of Astronomy at Stony Brook since 1989.

October 18,2019

Trevor J. Sears: Molecular Spectroscopy and Fundamental Physics

Precision measurements of the energy levels of small molecules can give insight into the properties of matter that previously had only been investigated by large accelerator-based experiments. The larger number of energy levels possessed by diatomic and even triatomic molecules results in increased chances for near coincidence between levels of different symmetry.

These “near-degeneracies” can result in great sensitivity to weak symmetry-breaking interactions resulting from the breakdown of the standard model of physics. With new experimental techniques and judicious choices of molecules to attack, physicists and chemists are now searching for such effects in small, laboratory-scale, instruments.

Dr. Sears holds a Ph.D. in Chemical Physics from the University of Southampton, UK, 1979. After working as a Postdoctoral Associate at Bell Telephone Laboratories (1979-1980) and for the National Research Council of Canada (1980-1983) he joined Brookhaven National Laboratory in 1983. An appointment he holds since together with a faculty appointment at Stony Brook University since 2006.

November 8, 2019

Navid Vafaei-Najafabadi: Recruiting the 4th state of matter to miniaturize particle accelerators

Particle accelerators have been an invaluable tool for scientific discovery and research. Future discoveries in high energy physics will require significantly more energetic particles than those currently produced. However, simply scaling the current machines to higher energies is a significant challenge because of their cost as well as the required space. A fundamental limitation that dictates the size of these machines is that the peak electric field used for accelerating particles must be below the damage threshold of the accelerating structures. Using a plasma, an ensemble of ionized atoms also known as the fourth state of matter, this limitation can be circumvented. Plasma structures have been shown to sustain accelerating fields that are hundreds of times higher than those currently generated in particle accelerators. In this talk, I will discuss how plasma waves are particularly well suited for accelerating electrons, the milestones already achieved, as well as the challenges that need to be overcome for plasma-based accelerators to form the foundation of next generation particle accelerators.

Navid Vafaei-Najafabadi is an Assistant Professor at Stony Brook University and the Facility Scientist at the Accelerator Test Facility of Brookhaven National Laboratory. He received his PhD from UCLA in 2016, after which he joined the Physics and Astronomy Department at Stony Brook University. He has participated in the plasma-based electron acceleration research for over a decade and has collaborated on experiments based on both laser-driven and particle-beam-driven plasma wakefield accelerators.