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Dr Bernhard Ersfeld

Research Fellow



Towards attosecond high-energy electron bunches : controlling self-injection in laser wakefield accelerators through plasma density modulation
Tooley M. P., Ersfeld B., Yoffe S. R., Noble A., Brunetti E., Sheng Z. M., Islam M. R., Jaroszynski D. A.
Phys. Rev. Lett. Vol 119, (2017)
An ultra-high gain and efficient amplifier based on Raman amplification in plasma
Vieux G., Cipiccia S., Grant D. W., Lemos N., Grant P., Ciocarlan C., Ersfeld B., Hur M. S., Lepipas P., Manahan G. G., Raj G., Reboredo Gil D., Subiel A., Welsh G. H., Wiggins S. M., Yoffe S. R., Farmer J. P., Aniculaesei C., Brunetti E., Yang X., Heathcote R., Nersisyan G., Lewis C. L. S., Pukhov A., Dias J. M., Jaroszynski D. A.
Scientific Reports Vol 7, pp. 1-10, (2017)
Observations on the ponderomotive force
Burton D. A., Cairns R. A., Ersfeld B., Noble A., Yoffe S., Jaroszynski D. A.
Relativistic Plasma Waves and Particle Beams as Coherent and Incoherent Radiation Sources IIProceedings of SPIE Vol 10234, (2017)
Wide-angle electron beams from laser-wakefield accelerators
Brunetti E., Yang X., Li F.Y., Reboredo Gil D., Welsh G.H., Cipiccia S., Ersfeld B., Grant D.W., Grant P.A., Islam M.R., Shahzad M., Tooley M.P., Vieux G., Wiggins S.M., Sheng Z.M., Jaroszynski D.A.
Proceedings of SPIE 7982, Smart Sensor Phenomena, Technology, Networks, and Systems 2011 Vol 10240, pp. 102400P-102400P-12, (2017)
Three electron beams from a laser-plasma wakefield accelerator and the energy apportioning question
Yang X., Brunetti E., Reboredo Gil D., Welsh G.H., Li F.Y., Cipiccia S., Ersfeld B., Grant D.W., Grant P.A., Islam M.R., Tooley M.P., Vieux G., Wiggins S.M., Sheng Z.M., Jaroszynski D.A.
Scientific Reports Vol 7, (2017)
Increased impedance near cut-off in plasma-like media leading to emission of high-power, narrow-bandwidth radiation
Hur M. S., Ersfeld B., Noble A., Suk H., Jaroszynski D. A.
Scientific Reports Vol 7, pp. 1-9, (2017)

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Jaroszynski, Dino (Principal Investigator) Ersfeld, Bernhard (Co-investigator) Burgess, Ronan Timothy Liam (Research Co-investigator)
Period 01-Oct-2009 - 01-Oct-2010
EPSRC Doctoral Training Grant | Farmer, John Patrick
Jaroszynski, Dino (Principal Investigator) Ersfeld, Bernhard (Co-investigator) Farmer, John Patrick (Research Co-investigator)
Period 01-Oct-2007 - 14-Oct-2013
Jaroszynski, Dino (Principal Investigator) Ersfeld, Bernhard (Co-investigator) Lepipas, Panagiotis (Research Co-investigator)
Period 01-Oct-2011 - 01-Oct-2015
Lab in a bubble
Jaroszynski, Dino (Principal Investigator) Boyd, Marie (Co-investigator) Brunetti, Enrico (Co-investigator) Ersfeld, Bernhard (Co-investigator) Hidding, Bernhard (Co-investigator) McKenna, Paul (Co-investigator) Noble, Adam (Co-investigator) Sheng, Zheng-Ming (Co-investigator) Vieux, Gregory (Co-investigator) Welsh, Gregor (Co-investigator) Wiggins, Samuel (Co-investigator)
"The lab in a bubble project is a timely investigation of the interaction of charged particles with radiation inside and in the vicinity of relativistic plasma bubbles created by intense ultra-short laser pulses propagating in plasma. It builds on recent studies carried out by the ALPHA-X team of coherent X-ray radiation from the laser-plasma wakefield accelerator and high field effects where radiation reaction becomes important. The experimental programme will be carried out using high power lasers and investigate new areas of physics where single-particle and collective radiation reaction and quantum effects become important, and where non-linear coupling and instabilities between beams, laser, plasma and induced fields develop, which result in radiation and particle beams with unique properties. Laser-plasma interactions are central to all problems studied and understanding their complex and often highly non-linear interactions gives a way of controlling the bubble and beams therein. To investigate the rich range of physical processes, advanced theoretical and experimental methods will be applied and advantage will be taken of know-how and techniques developed by the teams. New analytical and numerical methods will be developed to enable planning and interpreting results from experiments. Advanced experimental methods and diagnostics will be developed to probe the bubble and characterise the beams and radiation. An important objective will be to apply the radiation and beams in selected proof-of-concept applications to the benefit of society.
The project is involves a large group of Collaborators and Partners, who will contribute to both theoretical and experimental work. The diverse programme is managed through a synergistic approach where there is strong linkage between work-packages, and both theoretical and experiential methodologies are applied bilaterally: experiments are informed by theory at planning and data interpretation stages, and theory is steered by the outcome of experimental studies, which results in a virtuous circle that advances understanding of the physics inside and outside the lab in a bubble. We also expect to make major advances in high field physics and the development of a new generation of compact coherent X-ray sources."
Period 01-Apr-2016 - 31-Mar-2020
Theoretical studies of Raman Scattering and Chirped Pulse Amplification in Plasma
Jaroszynski, Dino (Principal Investigator) Bingham, Robert (Co-investigator) Ersfeld, Bernhard (Researcher)
The proposal is to explore the potential of using a fully ionised gas or plasma as an efficient short pulse amplifier. By exciting a plasma wave by two colliding (seed and pump respectively) pulses in plasma, it is possible to amplify the short seed pulse efficiently. The bandwidth of the plasma amplifier medium is enhanced when a chirped pump pulse is utilised. In the linear regime, before saturation of the amplifying process takes over, the long chirped pump laser pulse provides distributed amplification where different spectral components of the seed are amplified at different longitudinal positions in the plasma through the creation of a chirped plasma density echelon, much like a diffraction grating. This behaves as a long chirped mirror which simultaneously backscatters and compresses the chirped pump pulse and effectively broadens the gain bandwidth to that of the pump. The gain and the bandwidth of the amplifier depend on the natural oscillation frequency of the plasma (the plasma frequency) and the chirp rate (the rate at which the frequency changes along the pump pulse) and spectral bandwidth of the pump. This contrasts with conventional chirped pulse amplifiers (CPAs) and optical parametric chirped pulse amplifiers (OPCPAs) where the probe is chirped while the pump is usually monochromatic (un-chirped). The chirped pulse Raman amplifier has potential use either as a high fidelity ultra-short pulse high power linear amplifier or as a compressor of high energy chirped pulses from a conventional CPA amplifier. It also avoids the requirement for extremely large and expensive optical elements and compressors in vast vacuum chambers. Furthermore, because chirped pulse Raman amplification is a three wave parametric interaction it provides a means of eliminating pre-pulses and pedestals which usually limit the usefulness of conventional solid state CPA amplifiers. This research proposal will investigate the linear and non-linear stages of Raman amplification with a view to develop extremely high power lasers which have the potential of opening up new frontiers of physics such as using lasers to create particles from vacuum or create astrophysical conditions in the laboratory.
Period 01-Jan-2006 - 30-Jun-2009

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