165 164 Principal Scientist Profiles Matthew Zepf Matthew Zepf Principal Scientist Profiles PROFESSOR FOR HIGH FIELD PHYSICS AND LASER PARTICLE ACCELERATORS Prof. Zepf is a director of the Helmholtz Institute Jena and head of the Research Group for High Field Physics and Laser Acceleration at the University of Jena. He is a member of the Royal Irish Academy and serves on several scientific advisory committees at major international laser facilities. MATTHEW ZEPF RESEARCH AREAS Prof. Zepf’s research focuses on the applications of ultraintense lasers to applications and fundamental science. Particular areas of interest are • The development of laser driven and plasma based particle accelerators • Testing high field QED with ultra-intense lasers • Development and operation of high-power lasers • Ultrafast radiation sources TEACHING FIELDS Professor Zepf teaches High Field Laser Science, Plasma Physics and Specialist courses on Plasma Driven Radiation Sources. Bachelor and Master‘s degree topics are available both experimentally and numerically. RESEARCH METHODS In Prof. Zepf‘s group, research is conducted using a wide range of advanced methods are applied and developed for application in high power laser science. • The development and operation of multi-100TW lasers and their diagnostics • Numerical simulations of plasmas • Ultrafast optical and X-ray probe pulses • Particle detector development RECENT RESEARCH RESULTS Prof. Zepf’s Group has made notable achievements across the areas of high field physics and particle acceleration. Recent successes are important steps to achieving controlled injection in laser driven electron accelerators [1], where femtosecond probing elucidated the role of microscopic turbulence in the gaseous media on so-called self-injection. The ability to generate such electron beams with high power lasers allows the fundamental dynamics of electrons in electromagnetic fields to be tested with first results in the so-called radiation reaction regime demonstrated using the Astra Gemini laser in the UK [2, 3]. This work is currently continuing with collaborations based at the the Stanford Linear Accelerator, XFEL in Hamburg and a DFG consortium including CALA in Munich. Since our seminal work at the outset of laser driven proton and hadron accelerator research [4] we have developed new concepts [5] and continued to advance the field [6]. These particle radiation sources are complemented by research into intense X-ray and XUV sources exploiting the unique physical regimes accessible with ultra intese lasers [7], [8]. CONTROLLING MM-SCALE ELECTRON ACCELERATORS Controlling the parameters of a laser plasma accelerated electron beam is a topic of intense research with a particular focus placed on controlling the injection phase of electrons into the accelerating structure from the background plasma. An essential prerequisite for high-quality beams is controlled acceleration (i.e., no electrons accelerated beyond those deliberately chosen to be accelerated). We show that small-scale density ripplesin the background plasma are sufficient to cause the uncontrolled (self-)injection of electrons. Background free injection with substantially improved beam characteristics is demonstrated in a gas cell designed for a controlled gas flow. The image shows the experimentally and numerically derived regions of operation for laser driven accelerators with the self-injected charge being a function of microscopic turbulence (vertical axis) and laser strength (horizontal axis). [1] Kuschel et al., Phys. REv. Lett. 121, 154801 (2018). [2] Poder et al., Phys. Rev. X 8, 031004 (2018). [3] Cole et al., Phys. Rev. X 8, 011020 (2019). [4] Clarke et al., Phys. Rev. Lett. 84, 670 (1999). [5] Robinson et al., New journal of Physics 10, 013021 (2008). [6] Ma et al., Phys. Rev. Lett. 122, 014803 (2019). [7] Lei et al., Phys. Rev. Lett. 120, 134801 (2019). [8] Dromey et al., Nature Physics 5, 146 (2009). Contact: Phone: + 49 3641 947 616 Email: m.zepf@uni-jena.de
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