Lab Astrophysics and High Energy Densities
Pulsed power driven shock waves in magnetized plasmas
The PhD studentship will be focused on the study of shock waves driven by dense plasma flows (jets) on the 1.4MA MAGPIE pulsed power facility at Imperial College. The student will work on a modification for this purpose of the already existing set-ups which allow generation of high Mach number jets, on the development of appropriate targets allowing quantitative characterisation of the shocks driven by the jets, and on designing and testing of new configurations. The project will also involve the development and implementation of advanced plasma diagnostics, such as Thomson scattering, interferometry, optical and x-ray imaging and spectroscopy and X-ray radiography.
Funding: First Light Fusion
Supervisor: Sergey Lebedev
The Chimera high-power mid-IR OPCPA laser system.
Title: The Chimera high-power mid-IR OPCPA laser system.
Type: Experimental 80%, computational 20%
Funding: EPSRC DTA with DSTL top-up (UK nationality required).
Supervisors: Dr Stuart Mangles and Professor Roland Smith
Description: We are developing a new and unique type of mid infrared laser system based on "Optical Parametric Chirped Pulse Amplification" (OPCPA) as part of a large UK-US collaboration funded by DSTL, EPSRC and the US AFOSR. CPA is an elegant temporal stretch-compression technique that allows short pulses to be amplified to high energy without destroying the laser system, while optical parametric amplification (OPA) involves instantaneous transfer of energy from one laser beam to another. OPA has the advantage of very high gain, low noise and huge bandwidth compared to "traditional" laser amplifiers. It also allows access to laser wavelengths from 2-10 microns where it is very difficult to find a "traditional" laser material.
Our new Chimera laser combines the CPA and OPA techniques and will deliver multiple ultra-short light pulses to experiments including laser particle acceleration systems. Here moving to longer wavelengths offers some very attractive benefits as there is a strong l2 scaling of the energy an electron can acquire from the light field. The PhD will involve a combination of innovative laser development, characterisation of ultra-short light pulses (including the development of new instruments) and use of mid-IR light pulses in experiments. Laser acceleration work will likely include campaigns at both Imperial and at some of our US collaborators laboratories.
Time resolved x-ray absorption studies of Matter in Extreme Conditions
Much of the visible universe exists in extreme conditions, for example at high pressures and temperatures inside stars and gas giant planets or in the presence of intense xray fluxes (eg the low density gas near black holes). Much of our understanding of these systems comes from detailed atomic physics calculations. However testing these models experimentally is very challenging -- such extreme conditions can now be created in the lab but only for very short periods of time (~ 1ps).
One of the ideal ways to study the atomic physics of these highly transient lab systems under extreme conditions is to use X-ray absorption spectroscopy, and the ideal X-ray source would have a broad spectrum (to allow absorption features to be observed) and femtosecond duration (to freeze the transient behaviour). Our group has pioneered the development of X-ray radiation from laser wakefield accelerators which uniquely has both these properties. As part of the TeX-MEx project, funded by the ERC, we have have a fully funded PhD position available in 2017.
We are recruiting a student to join our experimental team. You will be involved in developing our X-ray absorption spectroscopy program, designing, running and analysing experiments at national and international facilities such as the Astra Gemini laser at the Rutherford laboratory and X-ray free electron lasers. These experiments will use the unique properties of betatron radiation to probe the ultrafast dynamics of some of the most extreme conditions in the universe.
For more information please contact Stuart Mangles.
Ultra-high contrast multi-terawatt laser systems.
Title: Ultra-high contrast multi-terawatt laser systems.
Type: Experimental 80%, computational 20%
Funding: EPSRC industrial CASE with AWE (UK nationality required).
Supervisor: Professor Roland Smith
Description: Current generation short-pulse, high-power laser systems can deliver peak powers in the terawatt (1012W) to petawatt (1015W) range and are used to probe and drive a very broad range of exotic processes including laser particle acceleration and laboratory simulations of supernova explosions and astrophysical jet formation. These lasers use a technique called Chirped Pulse Amplification (CPA) to stretch, amplify and compress a light pulse in time to avoid destroying the system. However this temporal manipulation also introduces subtle and unwanted effects that result in "low power" light a million or more times or less bright than the "main" pulse arriving on target early in time. This can cause catastrophic changes to experiments, for example destroying a fragile target before the "real" experiment can begin.
This project will identify sources of optical scatter, optical noise and temporal distortion in large CPA laser systems (particularly from diffraction gratings), characterise laser pre-pulse over ~11 orders of magnitude in intensity, and develop new methods of reducing pre-pulse. Experimental work will be based around "Cerberus" at Imperial, the UK's largest University based laser system. Cerberus is used for both development and testing of advanced laser concepts, and drives a broad range of experimental plasma physics campaigns. These include both stand-alone laser-plasma interaction and X-ray generation experiments and work in conjunction with the world's largest open access Z-Pinch MAGPIE. Cerberus is a "hybrid" multi-beam system that utilises large aperture flashlamp pumped Nd:Glass based power amplifiers. To extract the best performance from these very powerful amplifiers we couple them to an advanced "optical parametric chirped pulse amplification" (OPCPA) front end.
The project will involve collaborations with laser physicists from the UK's National Facilities, the Rutherford Appleton laboratory and AWE Aldermaston. Working as a multi-institute consortium we will have a much more leverage when persuading major grating manufacturers to create new types of low-scatter optics.