题目：Advances in laser driven ion acceleration studies:- efficiency and spectral control
报告人：Professor David Neely（Central Laser Facility, Rutherford Appleton Laboratory, STFC, Didcot, Oxon, UK; SUPA, Department of Physics, University of Strathclyde, Glasgow, UK）
摘要：
As the physical processes controlling the transfer of energy between the driving laser, the intermediate electrons and the ions becomes more fully understood, new methods for controlling the accelerated ion beam become accessible. Here, optically based techniques will be examined which have the ability to enhance the production efficiency and modify the spectral content of the beam. Using optically based methods will give greater flexibility and freedom when utilising the next generation of driving lasers which will operate at much higher repetition rates than current systems.
In experiments conducted using ps duration Nd:glass laser pulses, multi MeV ion beam generation from thin foils was investigated. The spectral content of the ion beam produced from the targets was monitored as the laser focal spot size volume on target was increased. As the spot size is increased the intensity reduces and it is possible to use thinner targets. Generally, the flux of ions increases as the foil thickness decreases until a critical minimum thickness is reached for a given irradiance. This result gives a clear demonstration of the effect of recirculation on the ion beam spectrum and information on the expansion dynamics of the electron sheath field.
In a second experiment, the coupling and transport of the high electron currents is investigated and the technique of dual pulse drive was used to modify the spectral content of the ion beam. Results showing the sensitivity of this technique to the relative ratio and timing between the two drive pulses will be presented as well as data on a plasma half cavity enhancement.
简介：
David Neely undertook his PhD studies in the field of collisional excitation soft X-ray lasers at the Queens University of Belfast before moving to the Central Laser Facility, STFC, Oxfordshire, UK in 1992. Using the Vulcan laser which provided combined ns and ps pulses he worked on experiments exploring electron acceleration, high harmonic production, shocks and plasma diagnostics. The short pulse laser power was steadily increased through a number of facility upgrades, attaining PW performance in 2003 which enabled the first experiments in the relativistic interaction regime to be undertaken. He interest in pre-plasma free interactions led to utilising plasma mirrors in 2005 to enhance the laser contrast to investigate ion acceleration from ultra-thin (20nm) foils. He took up a visiting Professorship at the University of Strathclyde in 2007 and the Mitsuyaki Abe Chair, PMRC, Japan in 2008 and continues to collaborate closely with international researchers in China, India, Europe and America. As well as his facility related development activities, his grant funded research interests are in laser driven ion acceleration, fusion studies, high power industrial laser applications and plasma diagnostics. He currently holds an STFC individual merit fellowship, obtained in 2010 which has enabled a greater concentration on his science interests. Recent research work has utilised multiple short pulses spaced on the order of ps apart to provide a greater degree of control on the ion acceleration process. This opens up the possibility of shaping the spectral content of the ion beams and also obtaining greater efficiency, a necessity for the wider development of the field. Understanding the generation and transport of the hot electrons is also an area of interest to both the fundamental underlying physics and applications. He is currently supervising two research assistants and two PhD students (registered at the University of Strathclyde) and conducts his research both in the UK and utilising international laser facilities.
时间：2013年10月31日（星期四）下午14：30
地点：中科院物理研究所M楼249会议室
联系人：李玉同 研究员 （Tel:82648014）
金奎娟 研究员（Tel：82648099）
主办单位：中国科学院光物理重点实验室
