PhD Position in Accelerator Physics : Gif-sur-Yvette, France Space charge compensation in low energy beam lines of high intensity light ion accelerators Project Summary One of the current challenges of high intensity accelerators (beam power in the Mega-Watt range) is the beam dynamics in the low energy beam transport (LEBT) lines. This dynamic is dominated by space charge field (electromagnetic field self-induced by the beam) that is generally non-linear and can create halo phenomena, emittance growth and beam losses. However, a beam propagating in a low energy beam line induces ionization of the residual gas present in the vacuum chamber. The secondary particles produced by ionization (i.e.\ electrons or ions), which have an opposite polarity to the particles of the beam, are trapped by the beam potential ; the particles with the same polarity are repelled from the beam. Thus, the low-energy beam can be considered as a plasma creating a focusing effect that counteracts the space charge electric field. This phenomena is called space charge compensation. Nevertheless, space charge compensation is incomplete, not homogeneous in space and is time dependent (transitory regime before a steady state is reached). In order to describe correctly the dynamics of a beam propagating in a LEBT, it is necessary to know the degree of space charge compensation, its longitudinal, transverse and time dependency. These values can be qualitatively estimated by using simple analytical models but it is now necessary to obtain predictive and quantitatively accurate results. The goal of the proposed thesis is to reach a better understanding of the space charge compensation of intense ion beams at low energy. Numerical simulations will be performed using dedicated computer codes. New models will also be implemented to reach a better description of the physical phenomena involved in LEBTs when space charge compensation occurs. Finally, an experimental program is also planned in order to perform measurements on IFMIF/LIPAc injector (Rokkasho, Japon), FAIR proton linac injector (CEA/GSI collaboration) or on a dedicated test bench at CEA-Saclay. The experimental results will be compared to simulations. Degree requirement Candidates should hold a Master of Science in physics or an engineer degree (with good academic records) with a specialty either in simulations and numerical methods or experimental/applied physics. Strong speaking & writing communication skills, either in French or in English, are mandatory. Funding This PhD has been elected as a sujet phare (important subject) of CEA in 2014. Consequently, the position will be fully funded by a CFR/CEA grant on a priority basis. Application Applicants should send their curriculum vitae along with a motivation letter and contact information of at least one reference to: [email protected]… nature/naturejobs/science/jobs/383957-phd-position-in-accelerator-physics
Posted on: Sat, 08 Mar 2014 04:15:44 +0000
Trending Topics
Recently Viewed Topics
© 2015