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Physics Research TheT HE Plasma P LASMA Science S CIENCE && FusionF USION CenterC EN T ER • MMassachusettsASSACHUSE tt S I NSInstituteT I T U T E O Fof T ECHNOLOGYTechnology PHYSICS RESEARCH Understanding the basic physics of plasmas is necessary not only to advance fusion research, but to increase the physics-based foundations of plasma-related scientific disciplines and applications. embers of the Physics Re- search Division, including theoretical and experimen- Mtal plasma physicists, faculty mem- bers, graduate and undergraduate students and visiting collaborators, work together to better understand plasmas and to extend their uses. Research includes: ■ Laboratory experiments ■ Development of novel plasma diagnostics ■ Theory of magnetically confined fusion plasmas Photo by Paul Rivenberg Dr. Jan Egedal works atop the Versatile Toroidal Facility, a medium-sized tokamak currently ■ Nonlinear wave used to study magetic reconnection, a phenomenon observed in solar flares. propagation, turbulence In addition to basic plasma theory, waves to control pressure and current and chaos topics being pursued at the PSFC profiles in order to control instabilities ■ Space plasma physics include tokamak research on radio and achieve steady state operation in frequency heating and current drive, high pressure plasmas. ■ Plasma astrophysics core and edge transport and turbu- ■ Laser-plasma interactions lence, and magnetohydrodynamic and In the area of inertial confinement kinetic stability. This research sup- fusion (ICF), theorists study the ports the PSFC tokamak, Alcator C- ablation process, during which a Theoretical Plasma Physics Mod, and the Levitated Dipole Experi- plasma is created that causes nonlin- ment (LDX), as well as other such ear scattering of the laser light. This Using the fundamental laws of experiments around the world. scattering not only reduces how physics, theorists at the PSFC are Interaction between MIT research efficiently the target can be heated, but developing improved analytical and staff and scientists at other facilities also generates hot electrons that can numerical models to better describe fosters vital scientific collaborations in preheat the core, inhibiting compres- plasma phenomena both in the the US and abroad. sion. PSFC theorists focus on under- laboratory and in nature. Theoreti- standing experimental observations of cal plasma research is essential not MIT Theorists also investigate concepts scattered light due to laser-plasma only to better understand basic to improve tokamak performance. One interactions, hoping to find ways to plasma physics, but also to sup- promising approach to advanced control the deleterious effects of these port many areas of fusion physics. tokamak operation uses radio frequency phenomena. 1 Experimental Plasma Physics Many theorists work with Experiments are conducted both on- graduate students on site at the PSFC, on small-to-medium- cutting edge research. scale experimental devices, and off- Dr. Peter Catto advises Natalia Krasheninnikova, site, on large-scale national and who is studying plasma international fusion devices. stability. Some of Dr. Catto’s research focuses on how the electric field Experiments include: is established in both the edge and core of toka- ■ exploring new maks like Alcator C-Mod, confinement concepts, MIT’s premier fusion experiment. such as the Levitated Dipole Experiment; ■ developing new diagnostics for measuring plasma parameters; ■ investigating space physics phenomena through laboratory simulations and off-site ionospheric observations; Photos by Paul Rivenberg Nuclear Engineering Professor Jeffrey Freidberg ■ developing novel (above left), Associate Director of the PSFC, diagnostics for inertial teaches plasma physics-related courses and confinement (ICF) supervises student theses. physics experiments; Dr. Abhay Ram combines teaching with research in the areas of plasma heating and ■ exploring novel scientific current generation by radio frequency waves, uses of plasma phenomena. nonlinear plasma dynamics, space plasma Levitated Dipole Experiment physics, and laser-plasma interactions. Physicists at the PSFC are exploring novel magnetic confinement configu- rations that are fundamentally dif- ferent from the tokamak. These may lead to alternate reactor concepts, and provide insights into space and astrophysical processes. One such approach, which uses a levitated cur- rent-carrying superconducting ring, is being pursued as a collaboration with Columbia University. Such a current ring generates a dipole type magnetic field geometry, which in turn confines a torus of hot plasma. Dipole confinement is observed in nature to be robust (e.g., in the magnetosphere around the planet Jupiter). This Levi- tated Dipole Experiment (LDX) will improve our understanding of dipole Photo by MP McNally confinement in a laboratory setting. DOE Office of Fusion Energy Director of Research John Willis and MIT Associate Provost Alice Gast cut the ribbon for the Levitated Dipole Experiment, joined by members of the LDX team. Graduate students working on the project sit atop the vacuum chamber. 2 Phase Contrast Imaging on DIII-D and C-Mod It is now widely believed that micro- turbulence in magnetically confined fusion plasmas results in excessive loss of particles and heat. To better under- stand such turbulence, PSFC research- ers have developed a new diagnostic using CO2 lasers and a special imaging technique widely used in microscopy - phase contrast imaging. This diagnos- tic, which provides detailed measure- ments of the density fluctuations with extraordinary sensitivity and fine spatial and temporal resolution, is being used to study turbulence and RF waves on the DIII-D tokamak in San Diego, and on the Alcator C-Mod tokamak at the PSFC. Recent up- MIT undergraduates work with the All Sky Imaging System (ASIS) designed to diagnose plasma grades will allow tests of some of the turbulence occuring in space and laboratory plasmas. ASIS can record infrared, visible, and ultra- violet emissions to determine the profiles of plasmas and the structures of plasma turbulence. latest theoretical predictions regard- ing the stabilization of microturbu- lence, leading to improved confine- in magnetic fusion devices. VTF has these experiments researchers study ment and RF wave propagation. made it possible to measure the instabilities driven by high-energy plasma response to reconnection with particles, such as radio frequency- Magnetic Reconnection unprecedented accuracy in the driven energetic ions and fusion-gen- laboratory, stimulating the develop- erated alpha-particles. These studies Research staff and students investigate ment of new theoretical models for lead to an improved understanding magnetic reconnection using the reconnection. of plasma stability and transport that Versatile Toroidal Facility (VTF), a will be important in a burning plasma toroidal facility built largely by experiment such as the international graduate and undergraduate students Joint European Torus (JET) collaboration ITER, where the fu- and PSFC staff. Magnetic reconnec- This program conducts collaborative sion process generates a substantial tion is the breaking and reconnecting experiments at the Joint European alpha-particle component. The results of magnetic field lines interacting with Torus (JET) in England, the world's of our research have clarified the plasma. Reconnection controls the largest tokamak and the major relation between these waves and the spatial and temporal evolution of experimental tool of the European plasma to such a point that informa- explosive plasma phenomena such as Fusion Development Agreement. In tion about some of the plasma's most solar flares, coronal important parameters can be ob- mass ejections and tained from the wave measurements. internal disruptions JET, in England, is the largest tokamak in the world, and is improving understanding of plasma stability and transport. 3 T HE P LASMA S CIENCE & F USION C EN T ER • M ASSACHUSE tt S I NS T I T U T E O F T ECHNOLOGY Ionospheric Plasma Research Researchers and students in this program perform field and laboratory experiments to understand plasma turbulence due to radio frequency heating. They travel to Alaska, Puerto Rico and other sites for their investi- gations. Students use the Ionospheric Radar Integrated System (IRIS) at Millstone Hill, Massachusetts, for remote sensing of space plasma turbu- lence, and the All Sky Imaging System (ASIS), to study the spatial structures of this turbulence. Understanding turbulence will aid satellite communi- cations, and will help control plasma turbulence in future fusion devices. ne of the novel Odiagnostics PSFC scientists have developed Photo courtesy of LLE for the National Ignition PSFC Group Leader Richard Petrasso (bottom right) looks on as the MIT-designed charged particle spectrometer (upper right) is installed on the target OMEGA laser at Facility (NIF) would use 31 the University of Rochester Laboratory for Laser Energetics (LLE). MeV protons, generated within the NIF capsule, to products with novel instrumentation. scientists have developed two novel di- help scientists determine Current experiments on the OMEGA agnostics for NIF that could be used in whether NIF has achieved laser facility at LLE have provided addition to many of the charged-par- its goal of producing information about fusion yield, plasma ticle diagnostics they have developed substantial themonuclear temperature and density, implosion for OMEGA. The first new diagnostic symmetry,
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