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2 PhD positions

Position 1: Magnetized relativistic laboratory astrophysics

The proposed PhD project lies in the frame of the young field of "laboratory astrophysics", aiming at answering some of the most fundamental questions in astrophysics as, e.g. the nature of the cosmic rays that are thought to be generated from violent shocks following the supernova or hypernova explosion of star (in the so-called "gamma-ray burst" or GRB). Shocks of low-density plasmas have been started to be studied in this frame, however only using high-power laser, low-velocity plasmas, which moreover lack of any large-scale magnetic field which exists in such astrophysical environment. The ambition of the project would be to solve these two issues by exploiting high-velocity shocks, and performing them in a dynamically important magnetic field. Through simulations (in partnership with CELIA-Bordeaux), the production of energetic particles and radiation by collisionless shocks or magnetic reconnection events will be tackled. For this, the project will take advantage of newly available experimental capabilities (high-power lasers coupled to pulsed strong magnetic fields, see ) and exploit the results using 2D and 3D hydrodynamic, MHD and kinetic numerical simulations to get a complete picture of the phenomena. This would also allow planning for performing experiments on the large-scale PETAL at the horizon of 2016. By allowing to study all these effects in the laboratory, the project is a great opportunity to bring significant new results to compare with existing observations (e.g. the production of high-energy particles in GRBs) and to simulations of these phenomena.

Position 2: Ion beam interactions with matter

The characteristics of charged particles interacting with other materials have been studied since the discovery of their existence and vast amounts of experimental data has been accumulated on this topic. However, ion interactions with dense plasmas are still untouched. The main reason is that the bunch length of existing particle sources produced by conventional accelerator (typically ns) are too long to probe such dense plasmas before they disassemble. However, many theories exist for ion interaction in warm plasmas, although unchecked. To overcome this difficulty, we have developed for several years (see http://tel.archives-ouvertes.fr/docs/00/87/78/75/PDF/M._Gauthier_these_2013.pdf) a new, compact, low-cost, experimental platform that utilizes short pulse laser produced ion beams which have different, but complementary, characteristics compared to conventional accelerators. Such laser-based platform, by producing very short ion bunches, presents the potential to finally breakthrough in studying the temporal dynamics and interactions with plasmas. The project will focus on performing measurements of the energy loss of protons and alpha particles after passing through several types of un-heated and heated low-Z, dense gases. This study sits within the applicative goals of the IZEST http://www.izest.polytechnique.edu/] project where the use of such beams is envisoned, with the help of high-repetition rate lasers, to help recycling spent nuclear fuel: an intense proton beam is accelerated, then converted into neutrons which induce the spallation of the radioactive fuel. However, when the high fluxes of ion irradiate the neutron converter, target heating will take place and will modify the slowing down of the ions within and thus impact the rate of nuclear reactions. This, of fundamental importance, has however never been evaluated, and is the goal of the project.

 More details :

The positions will be based at Ecole Polytechnique (France). It is mandatory that the candidate has completed a master degree from its home institution before starting the PhD program, however candidates can apply while they are in the process of completing their master. The candidate should have some experience in experimental physics and preferably experience with lasers and plasma. The candidate will benefit from the strong international context of the initiative, and is also expected to be ready to perform experiments in various countries, in the EU, the USA or Asia. Due to restriction of some participating labs, candidates should be citizens from the EU, the US, Japan or Korea.

The salary will be around 1500 € net per month, with a duration of 3 years.

It is requested to people interested by the position to send a CV to Julien Fuchs.

Nous contacter

Laboratoire LULI - Bât 403
Ecole Polytechnique
91128 Palaiseau Cedex
France
tel : +33 (0) 1 69 33 54 07