Thesis presented March 04, 2019

Abstract:
The interaction between a high-energy laser and a thin hydrogen target can generate an electrostatic field accelerating protons up to a few tens of MeV. This scientific field is called "laser/plasma acceleration". In this context, the Low Temperature Laboratory (CEA, France) has designed in 2014 a prototype extruding thin solid-hydrogen ribbon-shaped targets of onemillimeter in width and a few tens of micrometers in thickness.
This Ph.D. thesis studies the geometry, the stability and the velocity of these ribbons, which are critical in the laser/matter interaction. Experimental campaigns led with this prototype in different laser facilities are described as well. The second and main objective of this Ph.D. thesis is to charaterize and measure the rheological properties of solid Hydrogen, in order to model its flow through a submillimeter-wide extrusion nozzle. This characterisation has been made possible through the design of an innovative cryogenic rheometer generating a continuous shear deformation in solid hydrogen at controled temperature, below 14 kelvins. Shear deformationof solid Hydrogen is studied and detailled, and its apparent viscosity near its melting point is measured. A deformation law is stated, then tested by numerical simulation.

Keywords:
Cryogenics, Rheology, Solid Hydrogen, Laser-Matter interaction targets

On-line thesis.