Speaker
Andrei Savel'ev
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.2015.pdf
Structured plasmas for enhanced gamma emission at relativistic laser
intensities
K.Ivanov1,2, A.Lar’kin1, D.Gozhev1,2, A.Brantov2, V.Bychenkov2, A.Savel’ev1
1
Lomonosov Moscow State University, Moscow, Russia
2
Lebedev Physical Institute RAS, Moscow, Russia
We present experimental & numerical studies of interaction of femtosecond laser radiation
with intensity up to 5х1018 W/cm2 with structured plasma created using terawatt femtosecond
laser facility at MSU. Main stress was on the control of plasma parameters (luminosity in
X-ray and gamma ranges, generation of bunches of relativistic electrons) and their
optimization. Two approaches are discussed: (i) target surface/volume structuring on nano-
or microscale before interaction by different techniques and (ii) in situ liquid metal plasma
structuring with short pre-pulse giving rise to microjets.
(i) We employed different techniques for structuring of a target surface such as laser ablation
with additional chemical etching, chemical etching of bulk silicon, germanium and
molybdenum, volume structuring of CH films, etc. We paid special attention to the optical
damage of structures under action of femtosecond radiation prepulse. We found out
irradiation regimes and structures provided for prominent increase both in the fast electron
energy and gamma yield. Numerical simulations using PIC code Mandor allowed to get
insight into the mechanisms of the electron acceleration in structured targets.
(ii) By using a liquid metal as a target, one may significantly enhance the yield of hard x-rays
with a sequence of two intense femtosecond laser pulses. The influence of the time delay
between the two pulses is studied experimentally and interpreted with numerical simulations.
It was suggested that the first arbitrary weak pulse produces microjets from the target surface,
while the second intense pulse provides an efficient electron heating and acceleration along
the jet surface. These energetic electrons are the source of x-ray emission while striking the
target surface.
This work was supported by RSF (grant #17-12-01283, nanostructured targets studies),
RFBR (grant#16-02-00263, gamma & electron detection techniques, 16-02-00302, liquid
metal targets study).
