Principal Research Scientist
M.Sc. Engineering Physics, Uppsala University, Sweden (2003)
Ph.D. Applied Nuclear Physics, Uppsala University, Sweden (2010)
Postdoctoral Associate MIT Plasma Science and Fusion Center (2010-2013)
Nuclear diagnostics; neutron spectrometry; inertial confinement fusion; magnetic confinement fusion; applied nuclear physics.
Dr. Gatu Johnson has been a member of the PSFC High Energy Density Physics (HEDP) group since 2010. Her current primary responsibilities include acting as a responsible scientist involved in maintaining and analyzing data from two large magnetic neutron spectrometers [the Magnetic Recoil neutron Spectrometers (MRS)] installed at the OMEGA laser and the National Ignition Facility (NIF), and managing the HEDP group's Accelerator Facility for diagnostic development. She is also deeply involved in running and supporting experiments at the OMEGA laser facility, with a particular focus on plasma nuclear science, and is the principal investigator for a Discovery Science experiment on Stellar- and Big Bang Nucleosynthesis on the NIF. Dr. Gatu Johnson has uniquely used the MRS on the NIF to probe collective fuel motion in various implosions. Her findings seem to suggest that fuel kinetic energy in ignition implosions remains during burn, which has a significant impact on the implosion performance. Remaining fuel kinetic energy at burn may also impact measurements of plasma ion temperatures on the NIF, which is a topic Dr. Gatu Johnson is currently investigating, both through analysis of existing NIF data and design and execution of new OMEGA experiments to shed light on this issue.
M. Gatu Johnson, J.A. Frenje, C.K. Li, F.H. Séguin, R.D. Petrasso, R.M. Bionta, D.T. Casey, J.A. Caggiano, R. Hatarik, H. Y. Khater, D.B. Sayre, J.P. Knauer, T.C. Sangster, H.W. Herrmann, and J.D. Kilkenny, “Measurements of fuel and ablator ρR in Symmetry-Capsule implosions with the Magnetic Recoil neutron Spectrometer (MRS) on the National Ignition Facility”, Rev. Sci. Instrum. 85, 11E104 (2014)
M. Gatu Johnson, D.T. Casey, J.A. Frenje, C.-K. Li, F.H. Séguin, R.D. Petrasso, R. Ashabranner, R. Bionta, S. LePape, M. McKernan, A. Mackinnon, J.D. Kilkenny, J. Knauer and T.C. Sangster, “Measurements of collective fuel velocities in DT exploding pusher and cryogenically layered DT implosions on the NIF”, Phys. Plasmas 20, 042707 (2013)
M. Gatu Johnson, J.A. Frenje, D.T. Casey, C.K. Li, F.H. Séguin, R. Petrasso, R. Ashabranner, R.M. Bionta, D.L. Bleuel, E.J. Bond, J.A. Caggiano, A. Carpenter, C.J. Cerjan, T.J. Clancy, T. Doeppner, M.J. Eckart, M.J. Edwards, S. Friedrich, S.H. Glenzer, S.W. Haan, E.P. Hartouni, R. Hatarik, S.P. Hatchett, O.S. Jones, G. Kyrala, S. Le Pape, R.A. Lerche, O.L. Landen, T. Ma, A.J. MacKinnon, M.A. McKernan, M.J. Moran, E. Moses, D.H. Munro, J. McNaney, H.S. Park, J. Ralph, B. Remington, J.R. Rygg, S.M. Sepke, V. Smalyuk, B. Spears, P.T. Springer, C.B. Yeamans, M. Farrell, D. Jasion, J.D. Kilkenny, A. Nikroo, R. Paguio, J.P. Knauer, V. Yu Glebov, T.C. Sangster, R. Betti, C. Stoeckl, J. Magoon, M.J. Shoup III, G.P. Grim, J. Kline, G.L. Morgan, T.J. Murphy, R.J. Leeper, C.L. Ruiz, G. W. Cooper and A. J. Nelson, “Neutron spectrometry - An essential tool for diagnosing implosions at the National Ignition Facility (invited)”, Rev. Sci. Instrum. 83, 10D308 (2012)
M. Gatu Johnson, S. Conroy, E. Andersson Sundén, G. Ericsson, C. Hellesen, A. Murari, S. Popovichev, E. Ronchi, H. Sjöstrand, M. Weiszflog, V.L. Zoita and JET-EFDA Contributors, “Modeling and TOFOR measurements of scattered neutrons at JET”, Plasma Phys. Contr. Fusion 52, 085013 (2010)
M Gatu Johnson, C Hellesen, E Andersson Sundén, M Cecconello, S Conroy, G Ericsson, G Gorini, V Kiptily, M Nocente, S Pinches, E Ronchi, S Sharapov, H Sjöstrand, M Tardocchi, M Weiszflog1 and JET EFDA contributors, “Neutron emission from beryllium reactions in JET deuterium plasmas with 3He minority”, Nuclear Fusion 50, 045005 (2010)
M. Gatu Johnson, C. Hellesen, E. Andersson Sundén, M. Cecconello, S. Conroy, G. Ericsson, G. Gorini, M. Nocente, E. Ronchi, M. Tardocchi, M. Weiszflog and JET EFDA contributors, “Neutron emission levels during the ITER zero-activation phase”, Nucl. Fusion 50, 084020 (2010)
M. Gatu Johnson, L. Giacomelli, A. Hjalmarsson, J. Källne, M. Weiszflog, E. Andersson Sundén, S. Conroy, G. Ericsson, C. Hellesen, E. Ronchi, H. Sjöstrand, G. Gorini, M. Tardocchi, A. Combo, N. Cruz, J. Sousa, S. Popovichev and JET-EFDA contributors, “The 2.5-MeV neutron time-of-flight spectrometer TOFOR for experiments at JET”, Nuclear Instruments and Methods in Physics Research A 591 (2008) 417–430
“Signatures of non-thermal fuel motion in the DT-neutron spectrum measured at the National Ignition Facility (Invited)”, Inertial Fusion Sciences & Applications, Sep 2015
“Plasma Nuclear Science for exploring Nuclear Physics relevant to Stellar Nucleosynthesis (Invited)”, Frontiers of Plasma Science Town Meeting, Bethesda, MD, June 30, 2015
“A Discovery Science Experiment: Studies of Stellar and Big Bang Nucleosynthesis at uncharted conditions on the NIF (Invited)”, NIF User Group Meeting, Livermore, CA, Feb 2015