143 research outputs found
Design of plasma shutters for improved heavy ion acceleration by ultra-intense laser pulses
In this work, we investigate the application of the plasma shutters for heavy
ion acceleration driven by a high-intensity laser pulse. We use
particle-in-cell (PIC) and hydrodynamic simulations. The laser pulse,
transmitted through the opaque shutter, gains a steep-rising front and its peak
intensity is locally increased at the cost of losing part of its energy. These
effects have a direct influence on subsequent ion acceleration from the
ultrathin target behind the shutter. In our 3D simulations of silicon nitride
plasma shutter and a silver target, the maximal energy of high-Z ions increases
significantly when the shutter is included for both linearly and circularly
polarized laser pulses. Moreover, application of the plasma shutter for
linearly polarized pulse results in focusing of ions towards the laser axis in
the plane perpendicular to the laser polarization. The generated high energy
ion beam has significantly lower divergence compared to the broad ion cloud,
generated without the shutter. The effects of prepulses are also investigated
assuming a double plasma shutter. The first shutter can withstand the assumed
sub-ns prepulse (treatment of ns and ps prepulses by other techniques is
assumed) and the pulse shaping occursvia interaction with the second shutter.
On the basis of our theoretical findings, we formulated an approach towards
designing a double plasma shutter for high-intensity and high-power laser
pulses and built a prototype.Comment: 30 pages 13 figure
Expanding RIB Capabilities at the Cyclotron Institute: \textsuperscript{3}He-LIG production with an Isobar Separator LSTAR
A new \textsuperscript{3}He-driven IGISOL production station and mass
separator have been designed to produce neutron-deficient low-mass isotopes at
the Cyclotron Institute for the TAMUTRAP facility. The LSTAR design has a mass
resolution to reject contaminants with
efficiency.Comment: Proceeding for EMIS 202
Time evolution of stimulated Raman scattering and two-plasmon decay at laser intensities relevant for shock ignition in a hot plasma
Laser–plasma interaction (LPI) at intensities 1015–1016 W cm2 is dominated by parametric instabilities which can be
responsible for a significant amount of non-collisional absorption and generate large fluxes of high-energy nonthermal
electrons. Such a regime is of paramount importance for inertial confinement fusion (ICF) and in particular for the
shock ignition scheme. In this paper we report on an experiment carried out at the Prague Asterix Laser System (PALS)
facility to investigate the extent and time history of stimulated Raman scattering (SRS) and two-plasmon decay (TPD)
instabilities, driven by the interaction of an infrared laser pulse at an intensity 1:2 1016 W cm2 with a 100 mm
scalelength plasma produced from irradiation of a flat plastic target. The laser pulse duration (300 ps) and the high
value of plasma temperature (4 keV) expected from hydrodynamic simulations make these results interesting for a
deeper understanding of LPI in shock ignition conditions. Experimental results show that absolute TPD/SRS, driven at
a quarter of the critical density, and convective SRS, driven at lower plasma densities, are well separated in time, with
absolute instabilities driven at early times of interaction and convective backward SRS emerging at the laser peak and
persisting all over the tail of the pulse. Side-scattering SRS, driven at low plasma densities, is also clearly observed.
Experimental results are compared to fully kinetic large-scale, two-dimensional simulations. Particle-in-cell results,
beyond reproducing the framework delineated by the experimental measurements, reveal the importance of filamentation
instability in ruling the onset of SRS and stimulated Brillouin scattering instabilities and confirm the crucial role of
collisionless absorption in the LPI energy balance
Evidence of resonant surface wave excitation in the relativistic regime through measurements of proton acceleration from grating targets
The interaction of laser pulses with thin grating targets, having a periodic
groove at the irradiated surface, has been experimentally investigated.
Ultrahigh contrast () pulses allowed to demonstrate an enhanced
laser-target coupling for the first time in the relativistic regime of
ultra-high intensity >10^{19} \mbox{W/cm}^{2}. A maximum increase by a factor
of 2.5 of the cut-off energy of protons produced by Target Normal Sheath
Acceleration has been observed with respect to plane targets, around the
incidence angle expected for resonant excitation of surface waves. A
significant enhancement is also observed for small angles of incidence, out of
resonance.Comment: 5 pages, 5 figures, 2nd version implements final correction
Identification of medium mass (A=60-80) ejectiles from 15 MeV/nucleon peripheral heavy-ion collisions with the MAGNEX large-acceptance spectrometer
An approach to identify medium-mass ejectiles from peripheral heavy-ion
reactions in the energy region of 15 MeV/nucleon is developed for data obtained
with a large acceptance magnetic spectrometer. This spectrometer is equipped
with a focal plane multidetector, providing position, angle, energy loss and
residual energy of the ions along with measurement of the time-of-flight. Ion
trajectory reconstruction is performed at high order and ion mass is obtained
with a resolution of better than 1/150. For the unambiguous particle
identification however, the reconstruction of both the atomic number Z and the
ionic charge q of the ions is critical and it is suggested, within this work,
to be performed prior to mass identification. The new proposed method was
successfully applied to MAGNEX spectrometer data, for identifying neutron-rich
ejectiles related to multinucleon transfer generated in the 70Zn+ 64Ni
collision at 15 MeV/nucleon. This approach opens up the possibility of
employing heavy-ion reactions with medium-mass beams below the Fermi energy
(i.e., in the region 15-25 MeV/nucleon) in conjunction with large acceptance
ray tracing spectrometers, first, to study the mechanism(s) of nucleon transfer
in these reactions and, second, to produce and study very neutron-rich or even
new nuclides in previously unexplored regions of the nuclear landscape.Comment: 6 pages, 6figure
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