Physics Colloquium with Michael Downer

Abstract:  Tabletop lepton accelerators in which particles surf on light-speed plasma waves driven by powerful laser pulses have accelerated electron and positron bunches to ~10 GeV,¹ driven XUV free-electron lasers,² and produced femtosecond X-ray pulses for many research and clinical applications.³  Their particle energy frontier is poised to reach tens of GeV (equivalent to SLAC) soon. Equally important, plasma accelerators can now produce electron bunches of femtosecond, even attosecond, duration that can micro-bunch internally at least down to XUV wavelengths. These unique capabilities can potentially enable a new 21st century nonlinear X-ray spectroscopy capable of elucidating Nature's fastest electronic processes.   I will review the physics, history, and state-of-the-art of these laser-plasma accelerators.  I will then discuss current research in diagnostic and control strategies⁴ that will be vital for making them widely useful to science and society. 

1. Gonsalves et al., Phys. Rev. Lett. 122, 084801 (2019); Aniculaesi et al., Matter Rad. Extremes 9, 014001 (2024); Shrock et al., Phys. Rev. Lett. 133, 045002 (2024); Picksley et al., Phys. Rev. Lett. 133, 255001 (2024).  

2. Wang et al., Nature595, 516 (2021).

3. Albert et al., Plasma Phys. Control. Fusion 56, 064015 (2014). 

4. Downer et al., Rev. Mod. Phys. 90, 035002 (2018); LaBerge et al., Nature Photonics 18, 952  (2024). 

Bio

Prof. Downer has supervised 50 doctoral dissertations since joining the UT Physics Department in 1985, and published widely (h-50) in the fields of ultrafast optics, plasma physics, accelerator physics, and surface science.  He is a Fellow of the American Physical Society and of Optica (formerly the Optical Society of America), winner of a 2016 Humboldt Research Prize "in recognition of career-long accomplishments in research and teaching", and a University Distinguished Teaching Professor.  Prof. Downer's research team is pioneering a new generation of electron accelerators, driven by powerful femtosecond lasers, that are thousands of times smaller and cheaper than conventional accelerators and have spawned applications in areas ranging from materials science to medicine.  He enjoys training students by challenging them to design and build experiments that fit on a tabletop, that they can get their arms and head around and call their own. When not teaching or supervising experiments, he enjoys teaching and leading the Hill Country Highland Dancers, an Austin-based Scottish Highland dance group.