42 research outputs found
Experimental discrimination of ion stopping models near the Bragg peak in highly ionized matter
The energy deposition of ions in dense plasmas is a key process in inertial confinement fusion that determines the α-particle heating expected to trigger a burn wave in the hydrogen pellet and resulting in high thermonuclear gain. However, measurements of ion stopping in plasmas are scarce and mostly restricted to high ion velocities where theory agrees with the data. Here, we report experimental data at low projectile velocities near the Bragg peak, where the stopping force reaches its maximum. This parameter range features the largest theoretical uncertainties and conclusive data are missing until today. The precision of our measurements, combined with a reliable knowledge of the plasma parameters, allows to disprove several standard models for the stopping power for beam velocities typically encountered in inertial fusion. On the other hand, our data support theories that include a detailed treatment of strong ion-electron collisions
Proton stopping measurements at low velocity in warm dense carbon
: Ion stopping in warm dense matter is a process of fundamental importance for the understanding of the properties of dense plasmas, the realization and the interpretation of experiments involving ion-beam-heated warm dense matter samples, and for inertial confinement fusion research. The theoretical description of the ion stopping power in warm dense matter is difficult notably due to electron coupling and degeneracy, and measurements are still largely missing. In particular, the low-velocity stopping range, that features the largest modelling uncertainties, remains virtually unexplored. Here, we report proton energy-loss measurements in warm dense plasma at unprecedented low projectile velocities. Our energy-loss data, combined with a precise target characterization based on plasma-emission measurements using two independent spectroscopy diagnostics, demonstrate a significant deviation of the stopping power from classical models in this regime. In particular, we show that our results are in closest agreement with recent first-principles simulations based on time-dependent density functional theory
The Future of Warheads, Armour and Ballistics / 23rd International Symposium on Ballistics
23rd International Symposium on Ballistics, Tarragona, Spain, 16-20 April 2007In 1983 a â Grand Old Manâ of Ballistic Science, Dr. Robert J. Eichelberger, wrote1:
â Ballistic technology is generally considered a mature technology â as it should be after
centuries of intensive attention of some of the finest scientific minds of the world.â He
predicted that increased understanding of relevant physics and chemistry and development
of mathematical techniques and computer models would be key elements in the future of
ballistics and weapon system design. These predictions were very accurate!
But to-dayâ s developments and those of the foreseeable future go beyond this. Warheads
and ballistics â interior, exterior and terminal â are very dependent on the use and
properties of energetic materials â propellants and explosives â for their functioning. New,
potentially very powerful substances such as the N5+ and N5â ions and metallic hydrogen
were created in labs. Air-breathing propulsion â ramjets etc. - and efficient use of the high
combustion energy of some metals adds to the performance increase potential.
Increased use of intelligence, computers, sensors and fuzing in weapons, munitions and
armours has added another dimension to the efficiency achievable. New high-performance
materials have also meant great increases in effects and protection potential.
Developments possible in the next 20 years may have similar effect on warfare as the
revolution in weapons, munitions and armour that occurred in the late 19th century. The
statement that â Ballistic technology is generally considered a mature technologyâ is no
longer true. Any nation that will abstain from following the developments closely and
exploiting their advances will run the risk both of having weapons, munitions and
protection that prove inadequate and of making grave mis-investments