bluuebunny/crossref_metadata_2025 huggingface dataset:
XUV interferometry using high-order harmonics: Application
to plasma diagnostics
Authors: HERGOTT J.-F. , SALIÈRES P. , MERDJI H. , LE DÉROFF L. , CARRÉ B. , AUGUSTE T. , MONOT P. , D'OLIVEIRA P. , DESCAMPS D. , NORIN J. , LYNGÅ C. , L'HUILLIER A. , WAHLSTRÖM C.-G. , BELLINI M. , HULLER S.
Published: December 2002

In this paper, we present and compare the two different
XUV interferometric techniques using high-order harmonics
that have been developed so far. The first scheme is based
on the interference between two spatially separated phase-locked
harmonic sources while the second uses two temporally separated
harmonic sources. These techniques have been applied to plasma
diagnostics in feasibility experiments where electron densities up
to a few 1020 e−/cm3 have
been measured with a temporal resolution of 200 fs. We present the
main characteristics of each technique and discuss their respective
potentials and limitations.
Study of few-optical-cycles generation of high-order harmonics
Authors: VILLORESI P. , BARBIERO P. , POLETTO L. , NISOLI M. , CERULLO G. , PRIORI E. , STAGIRA S. , DE LISIO C. , BRUZZESE R. , ALTUCCI C.
Published: December 2002

The high-order harmonic generation process was studied
using laser pump pulses of different duration, down to
7 fs. The time profile of this kind of pulse corresponds
to a few optical cycles at the fundamental frequency, and
therefore a cycle-to-cycle variation of the maximum amplitude
occurs. These facts violate the adiabatic approximation
of the generation process, giving rise to new aspects of
the physical process. The comparison of results with pulses
in the two regimes are reported and discussed. The modeling
of the complete generation and propagation process in three
dimensions is also presented.
Measurement of XUV sources' wavefronts
Authors: LE PAPE S. , ZEITOUN PH. , DHEZ P. , FRANÇOIS M. , IDIR M. , ROS D. , CARILLON A.
Published: December 2002

New fields of X-ray source applications (X-ray laser
and high order harmonic generation) could appear if an
intensity higher than 1012 Wcm−2
is reached. Following this goal, we have started a complete
investigation of the X-ray beam wavefront both numerically
and experimentally. The first XUV wavefront sensor has
been developed and tested on different XUV sources. For
a better comprehension of the experimental results, a numerical
work (ray-trace code) has been performed. We present and
discuss the first results obtained on the X-ray laser at
21.2 nm.
Effects of self-generated electric and magnetic fields
in laser-generated fast electron propagation in solid materials:
Electric inhibition and beam pinching
Authors: BERNARDINELLO A. , BATANI D. , ANTONICCI A. , PISANI F. , KOENIG M. , GREMILLET L. , AMIRANOFF F. , BATON S. , MARTINOLLI E. , ROUSSEAUX C. , HALL T.A. , NORREYS P. , DJAOUI A.
Published: December 2002

We present some experimental results which demonstrate
the presence of electric inhibition in the propagation
of relativistic electrons generated by intense laser pulses,
depending on target conductivity. The use of transparent
targets and shadowgraphic techniques has made it possible
to evidence electron jets moving at the speed of light,
an indication of the presence of self-generated strong
magnetic fields.
Ionization and absorption effects in high-order harmonic
generation in gas-filled hollow fibers
Authors: NAUMOV A.N. , ZHELTIKOV A.M. , FEDOTOV A.B. , SIDOROV-BIRYUKOV D.A. , TARASEVITCH A.P. , ZHOU PING , VON DER LINDE D.
Published: December 2002

The influence of absorption and ionization on high-order
harmonic generation in a gas-filled hollow fiber is analyzed
within the framework of slowly varying envelope approximation.
Harmonic spectra and pressure dependencies are calculated
for high-order harmonic generation in hollow fibers filled
with different rare gases. Ionization of the gas filling
the fiber gives rise to self-phase modulation of the pump
pulse, changing the phase mismatch within the pump pulse
and shifting the maxima in pressure dependencies of high-order
harmonics.
Monte Carlo simulation of harmonic generation in InP
Authors: ADORNO D. PERSANO , ZARCONE M. , FERRANTE G.
Published: December 2002

Harmonics spectra in an n-type InP bulk semiconductor
showing up to the 13th harmonic are reported. The external
field is linearly polarized with the frequency ν = 100 GHz.
Calculations are based on a Monte Carlo simulation for the
electron motion in the conducting band and on an electrodynamics
equation for the harmonics generation. The effect of a significant
reduction of efficiency in the generation of particular
harmonics is found, and is traced back to a sort of alternating
field Gunn effect. A short analysis of the different physical
mechanisms giving rise to harmonics generation is presented.
A numerical ab initio study of harmonic generation
from a ring-shaped model molecule in laser fields
Authors: BAUER D. , CECCHERINI F.
Published: December 2002

When a laser pulse impinges on a molecule which is invariant
under certain symmetry operations selection rules for harmonic
generation (HG) arise. In other words, symmetry controls
which channels are open for the deposition and emission
of laser energy—with the possible application of
filtering or amplification. We review the derivation of
HG selection rules and study numerically the interaction
of laser pulses with an effectively one-dimensional ring-shaped
model molecule. The harmonic yields obtained from that
model and their dependence on laser frequency and intensity
are discussed. In a real experiment obvious candidates
for such molecules are benzene, other aromatic compounds,
or even nanotubes.
Characterization of electron beam propagation through
foils by innershell X-ray spectroscopy
Authors: PRETZLER G. , SCHLEGEL TH. , FILL E.
Published: December 2002

Characteristic X-rays generated by high-intensity laser
interaction with solids were investigated and used for
determining the resulting hot electron populations. Spectrally
as well as spatially resolved data are evaluated for this
purpose. The experimental data were compared with Monte
Carlo simulations to determine the electron energy distribution
and geometric features of the electron beam. These results
are in good agreement with PIC simulations. The self-generated
low-resistivity channel of the electron beam results in
a distinct difference in the generated rear-side X-ray
spot when the electron beam propagates in an insulator
rather than a metal. Self-generated electric fields prevent
electron propagation into the vacuum. This fact is used
for demonstrating photopumping of cobalt with copper
Kα radiation, an experiment relevant
to innershell X-ray laser schemes. The emission of cobalt
is compared with that of nickel, which is not photopumped
by copper Kα, and is found to be
enhanced by a factor of 2.5.
Charge-exchange collisions in interpenetrating laser-produced
magnesium plasmas
Authors: HARILAL S.S. , BINDHU C.V. , SHEVELKO V.P. , KUNZE H.-J.
Published: December 2002

Charge-exchange collisions are one of the effective pumping
methods for soft X-ray lasers. Experiments are performed
to investigate charge-exchange collisions between highly
charged Mg ions in colliding laser-produced magnesium plasmas.
Pinhole photography and XUV spectroscopy are used as diagnostic
tools. Spectroscopic studies show selective population
of n = 3 levels of Mg IX ions, which results in
enhancement of respective line intensities. Theoretical
calculations also give a large cross section as high as
10−15 cm2 for these charge-exchange
collisions when the relative velocities of the colliding ions
are of the order of 107 cm s−1.
XUV pinhole pictures are taken in early stages, which give
more insight into the expansion dynamics of the colliding
magnesium plasmas.
Status of a radio-frequency-based streak camera with
subpicosecond time resolution
Authors: BAK P.A. , CALABRESE R. , CHERNOUSOV YU.D. , GUIDI V. , GUIDI L. , GUROV S.M. , LOGATCHOV P.V. , PYATA E.E. , TECCHIO L. , TSYGUNOV A.S.
Published: December 2002

Usage of a cavity with a high quality factor in a streak
camera (SC) allows us to increase the energy of electrons
up to 100 keV and therefore to reduce the influence of
some of the effects that limit the SC time resolution. Time
resolution up to 1.4 ps on a prototype of a radio-frequency-based
SC (RFC) with circular scanning was demonstrated earlier.
Following this, the new RFC was produced. The possibility
of achieving a time resolution of 0.6 ps for a 350-ps single
light signal is demonstrated. Preparation for experiments
with spiral scanning (sub-ps time resolution for 10-ns
process duration) is in progress.
Equation of state of water in the megabar range
Authors: HENRY E. , BATANI D. , KOENIG M. , BENUZZI A. , MASCLET I. , MARCHET B. , REBEC M. , REVERDIN CH. , CELLIERS P. , DA SILVA L. , CAUBLE R. , COLLINS G. , HALL T. , CAVAZZONI C.
Published: December 2002

We present some preliminary results on the equation of
state (EOS) of water in a pressure regime of astrophysical
interest. In the experiments, structured targets made of
an aluminum step followed by a water layer are irradiated
by the laser at an intensity up to 4·1014
W·cm−2 to generate a shock wave.
Velocities are measured in the two materials using a VISAR
interferometric diagnostic for water, and a streak camera
to measure target self-emission for Al. EOS points for water
are obtained with the impedance mismatch method using Al EOS
as a reference. Water reflectivity was also measured.
Line spectroscopy with spatial resolution of laser–plasma
X-ray emission
Authors: LABATE L. , GALIMBERTI M. , GIULIETTI A. , GIULIETTI D. , GIZZI L.A. , NUMICO R. , SALVETTI A.
Published: December 2002

High dynamic range, space-resolved X-ray spectra of an
aluminum laser–plasma in the 5.5–8 Å
range were obtained using a TlAP crystal and a cooled CCD
camera as a detector. This technique was used to investigate
the emission region in the longitudinal direction over
a distance of approximately 350 μm from the solid target
surface. These data show that the electron density profile
varies by two orders of magnitude with the temperature
ranging from about 180 eV in the overdense region to about
650 eV in the underdense region. Accordingly, different
equilibria take place across the explored region which
can be identified with this experimental technique. Detailed
studies on highly ionized atomic species in different plasma
conditions can therefore be performed simultaneously under
controlled conditions.
Time-resolved X-ray diffraction at NERL
Authors: KINOSHITA KENICHI , HARANO HIDEKI , YOSHII KOJI , OHKUBO TAKERU , FUKASAWA ATSUSHI , NAKAMURA KEI , UESAKA MITSURU
Published: December 2002

For ultrafast material analyses, we constructed the time-resolved
X-ray diffraction system utilizing ultrashort X-rays from
laser-produced plasma generated by the 12-TW–50-fs laser
at the Nuclear Engineering Research Laboratory. Ultrafast transient
changes in laser-irradiated GaAs crystals were observed as X-ray
diffraction patterns. Experimental results were compared with
numerical analyses.
Inverse Faraday effect in a relativistic laser channel
Authors: KOSTYUKOV I. , SHVETS G. , FISCH N.J. , RAX J.M.
Published: December 2002

Interaction between energetic electrons and a circularly
polarized laser pulse in a relativistic plasma channel
is studied. Laser radiation can be resonantly absorbed
by electrons executing betatron oscillations in the channel
and absorbing angular momentum from the laser. The absorbed
angular momentum manifests itself as a strong axial magnetic
field (inverse Faraday effect). The magnitude of this magnetic
field is calculated and related to the amount of the absorbed
energy.
Modeling of the double pass X-ray laser: Effects on
its focalization
Authors: LE PAPE S. , ZEITOUN PH.
Published: December 2002

In this article we describe a new ray-trace code. This
code is a three-dimensional description of the beam propagation,
including the half cavity mirror. It is based on the integration
of the ray equation and on the calculation of the intensity along
the plasma. It works as a postprocessor of the hydrodynamic/atomic
code “EHYBRID,” which calculates the time evolution
of the gain, emissivity, electronic density, and the width
of the plasma. We present results obtained on different
schemes of X-ray laser generation.
Design of a time-compensated EUV and soft X-ray monochromator
with multilayer mirrors for high-order harmonics
Authors: POLETTO LUCA , TONDELLO GIUSEPPE
Published: December 2002

A time-compensated monochromator for ultrashort high-order
harmonics in the EUV and soft X-ray regions is presented.
The system consists of two grazing-incidence toroidal mirrors
used, respectively, as collimating and refocusing elements
and of two multilayer normal-incidence plane mirrors illuminated
in parallel light that rotate along a vertical axis to
select the operative wavelength, but remain parallel to
guarantee the constant direction of the exit beam. This
is performed by simultaneously rotating and translating
one of the two mirrors along an axis parallel to the exit
direction. The pulse time duration is not altered up to
few femtoseconds.
Numerical studies on the properties of femtosecond
laser plasma Kα sources
Authors: REICH CH. , GIBBON P. , USCHMANN I. , FÖRSTER E.
Published: December 2002

One of the features of ultra high intensity (UHI) short
pulse laser–matter interactions is the prospect of
creating a cheap, compact source of hard X rays
with femtosecond pulse duration. The properties of such
Kα sources are studied using analytical and
numerical models of hot electron generation and subsequent
transport in a range of materials (Reich et al., 2000).
First, we find that there is an optimum laser intensity for
Kα generation from bulk targets, which scales as
Z4.4. Second, we show that efficient hard
X-ray pulses with durations below 100 fs can be generated at
intensities of ∼1016 W/cm2.
Generation and applications of phase-locked white-light
continuum pulses
Authors: BELLINI MARCO , HÄNSCH THEODOR W.
Published: December 2002

We report on an experiment demonstrating the high degree
of mutual phase coherence between two white-light continuum
pulses independently generated by phase-locked ultrashort
laser pulses. We show that these secondary pulses are locked
in phase and exhibit surprisingly clear and stable Young's
interference fringes when overlapped on a screen in the
far field. We discuss the use of such phase-locked continuum
pulses in the realization of a new kind of ultrabroad frequency
comb for absolute frequency measurements throughout the
visible spectrum.
High power laser interaction with clusters
Authors: DESAI TARA
Published: December 2002

Response of clusters to laser radiation depends on the
laser parameters like wavelength, pulse duration, field,
and so forth. At moderate laser intensities, I ∼
1012 W/cm2, using a laser beam of
wavelength 1.06 μm and 10-ns pulse duration, we have studied
X-ray emission spectra from aluminum clusters of diameter
0.4 μm and gold clusters of 1.25 μm. Aluminum clusters
show a different spectra compared to bulk material whereas
gold clusters evolve towards bulk gold. Results are analyzed
on the basis of cluster dimension, laser wavelength, and pulse
duration. At higher laser intensities ≥1018
W/cm2, clusters undergo Coulomb explosion, giving
rise to energetic electrons and ions. Here we discuss the
possibility of harnessing these energetic particles for
heating a small volume of the precompressed DT fuel to
ignition condition relevant to fast ignition. Preliminary
results are discussed.
ICF target ignition studies in planar, cylindrical, and spherical
geometries
Authors: DJAOUI A.
Published: December 2002

A model for nonlocal α particle transport is implemented
in a one-dimensional radiation hydrodynamics code and applied for
typical directly and indirectly driven ICF target simulations.
Ignition criteria are compared for four configurations; spherical,
cylindrical, planar with a central hot spot, and another planar
configuration with a hot spot on one side. This last planar configuration
is then used for fast ignitor studies, since it is able to simulate
hot spot formation by direct laser heating and free expansion
towards the incoming beam. Ignition requirements as a function
of laser intensity and pulse length, taking into account the
relationship between intensity, hot electron temperature, and
range, are then determined.
Guest Editor's Preface: ULIA-2 Special Issue
Authors: Gizzi Leonida A. , Galimberti Marco
Published: December 2002

As early as 1997, we decided to promote a short series
of conferences devoted to a field that was showing dramatic
progress and in which an increasing number of young researchers
were participating. The Euroconference format of the “TMR
Programme of the Commission of the European Union” was
the most appropriate to fulfill the two objectives of a quasi
real-time presentation and discussion of novel results and a
tutorial support of young scientists from eminent lecturers
active in the field. The success of the two meetings, held in
two authentic capitals of the European cultural heritage, went
well beyond any optimistic expectation. More than 200 enthusiastic
participants, including approximately 100 young scientists,
made those events a unique experience of scientific progress
and debate. I wish to express my gratitude to Dimitris
Charalambidis, who divided with me this experience, to the
Scientific Advisory Committee, who guaranteed the high scientific
level of the meetings, and to the Local Organizers, who made
all this possible. The ULIA participants strongly appreciated
the initiative of Laser and Particle Beams to edit
two special issues with a collection of selected works presented
at the ULIA meetings. Antonio Giulietti was the Scientific Promoter
of the ULIA Conferences
Editor's Preface
Authors: Miley George H.
Published: December 2002

By this time, we trust that you have received issues
from Volume 18 of Laser and Particle Beams which used
the new, large-page size, double-column format. As I indicated
in an earlier preface, this format provides additional type-space,
which will hopefully allow us to speed up publication of articles
in LPB.
The prospect of laser fusion in the 21st century
Authors: YAMANAKA CHIYOE
Published: December 2002

The Publisher is very sorry for not listing this article on
the Table of Contents for Volume 20, Number 1, 2002.
Guest Editor's Preface: The S. Feliu Conference
Authors: Batani D.
Published: December 2002

This issue of Laser and Particle Beams contains 25
papers that were presented at the conference on “Matter
in Super-Intense Laser Fields: Short Pulse, Superstrong
Laser-Plasma Interactions,” held in S. Feliu de Guixols,
Spain, from 29 September to 4 October 2001. Almost 100 scientists
and young researchers (Ph.D. students and Post Docs) took part
in this successful event, despite the terrible terrorist acts
of September 11, 2001 in New York, which prevented many speakers
from taking part, especially those coming from the United States.
Influence of excited crystalline medium on interaction processes
of ultrarelativistic electrons
Authors: AGANYANTS A.
Published: December 2002

New experimental results of investigations of the interactions
of an intense 4.3-GeV electron beam with an aligned single crystal
are given in the case when the electrons travel close to the
crystalline planes (110). The growth of low energy radiation
yields with the intensity of the electron beam and the peculiar
properties of the produced γ-quanta at their passage through
a small collimator aperture were observed. Large angular asymmetry
at the scattering of low energy γ-quanta, which is evidence
of high polarization of the radiation, was also detected. These
unexpected phenomena may be stimulated by strong correlations
of atomic excitations in crystals. The obtained results will
be of use for understanding of the properties of both the excited
crystalline medium and the mechanism of intense radiation under
these conditions and also for practical applications of the
radiation.
Pressure amplification in thermal X-ray irradiated foam layered
gold targets
Authors: BATANI D. , DESAI T. , LUCCHINI G. , LÖWER TH. , HALL T.A. , NAZAROV W. , KOENIG M. , BENUZZI-MOUNAIX A.
Published: December 2002

We have studied the interaction of soft X-ray thermal radiation
with foam-layered metal targets. The X-radiation was produced
by focusing a high energy laser inside a small size hohlraum.
An increment in shock pressure was observed with the foam layer
as compared to bare metal targets.
Fast electron transport and heating in solid-density matter
Authors: MARTINOLLI E. , BATANI D. , PERELLI-CIPPO E. , SCIANITTI F. , KOENIG M. , SANTOS J.J. , AMIRANOFF F. , BATON S.D. , HALL T. , KEY M. , MACKINNON A. , SNAVELY R. , FREEMAN R. , ANDERSEN C. , KING J. , STEPHENS R. , LE GLOAHEC M. RABEC , ROUSSEAUX C. , COWAN T.E.
Published: December 2002

Two experiments have been performed to investigate heating
by high-intensity laser-generated electrons, in the context of
studies of the fast ignitor approach to inertial confinement fusion
(ICF). A new spectrometer and layered targets have been used to detect
Kα emission from aluminum heated by a fast electron beam.
Results show that a temperature of about 40 eV is reached in solid
density aluminum up to a depth of about 100 μm.
Electron–ion collision-induced harmonics generation
in a plasma with an isotropic bi-Maxwellian distribution
Authors: FERRANTE G. , URYUPIN S.A. , ZARCONE M.
Published: December 2002

A treatment is given of harmonics generation resulting from
nonlinear inverse bremsstrahlung in a plasma with an anisotropic
bi-Maxwellian electron velocity distribution function. A complete
characterization of the process is reported. In particular,
analytically and numerically we established how the efficiency
of the odd harmonics generation and their polarization depend
on such process parameters as: (1) the degree of effective
temperature anisotropy, (2) the frequency and the intensity
of the fundamental wave, and (3) the angle between the fundamental
wave field direction and the symmetry axis of the electron
distribution function.
Magnetic field effects in strong field ionization of
single-electron atoms: Three-dimensional numerical simulations
Authors: DE ALDANA J.R. VÁZQUEZ , ROSO LUIS
Published: December 2002

Based on realistic numerical simulations of the three-dimensional
time-dependent Schrödinger equation describing a hydrogen
atom interacting with a strong electromagnetic field, the influence
of the magnetic component is studied. The same computational
techniques can be applied to the case of strong field
photoionization as well as to the case of ionization by an incident
relativistic heavy ion. One of the main consequences, in the
strong-laser-field case, is the presence of true even harmonics
of the incoming field. In the heavy ion impact, the asymmetry
of the wave function reveals the importance of the nondipole
nature of the interaction.
Application of novel techniques for interferogram analysis
to laser–plasma femtosecond probing
Authors: TOMASSINI P. , GIULIETTI A. , GIZZI L.A. , NUMICO R. , GALIMBERTI M. , GIULIETTI D. , BORGHESI M.
Published: December 2002

Recently, two novel techniques for the extraction of the
phase-shift map (Tomassini et al. (2001). Applied
Optics40, 35) and the electronic density map estimation
(Tomassini P. & Giulietti A. (2001). Optics Communication199, 143–148) have been proposed. In this article,
we apply both methods to a sample laser–plasma interferogram
obtained with femtoseconds probe pulse, in an experimental setup
devoted to laser particle acceleration studies.
A review of X-ray laser development at Rutherford Appleton
Laboratory
Authors: TALLENTS G.J. , ABOU-ALI Y. , EDWARDS M. , KING R. , PERT G.J. , PESTEHE S.J. , STRATI F. , LEWIS C.L.S. , KEENAN R. , TOPPING S. , KLISNICK A. , GUILBAUD O. , ROS D. , CLARKE R. , NOTLEY M. , NEELY D.
Published: December 2002

Recent experiments undertaken at the Rutherford Appleton
Laboratory to produce X-ray lasing over the 5–30 nm
wavelength range are reviewed. The efficiency of lasing is
optimized when the main pumping pulse interacts with a preformed
plasma. Experiments using double 75-ps pulses and picosecond
pulses superimposed on 300-ps background pulses are described.
The use of travelling wave pumping with the approximately
picosecond pulse experiments is necessary as the gain duration
becomes comparable to the time for the X-ray laser pulse to
propagate along the target length. Results from a model taking
account of laser saturation and deviations from the speed of
light c of the travelling wave and X-ray laser group velocity
are presented. We show that X-ray laser pulses as short as
2–3 ps can be produced with optical pumping pulses of
≈1-ps.
New approach to dense plasma thermodynamics in the
superconfiguration approximation
Authors: PAIN J.-CH. , BLENSKI T.
Published: December 2002

We propose a new approach to the calculation of ion populations
in the LTE dense plasmas in the superconfiguration approximation.
The screening of plasma ions is obtained using the same
free-electron chemical potential for each ion charge. This chemical
potential is determined by iteration keeping the total density
constant and varying the volume of each ion. In such a way our
approach not only gives the charge neutrality of the plasma,
but also assures that the free-electron density is equal in
the vicinity of each ion. The resulting ion charge distribution
is different with respect to the one obtained without imposing
the constraint of equal chemical potential. For instance, the
effective charge is a little bit higher, which can change the
shape of the absorption spectra, especially at higher densities.
Examples of absorption spectra of medium-Z plasmas
in a temperature and density range close to the present opacity
measurements are shown.
Charged particle source produced by laser–plasma
interaction in the relativistic regime
Authors: MALKA V.
Published: December 2002

Plasmas irradiated by an intense laser beam have recently been
demonstrated to be sources for particles (electrons, ions,
positrons). During this interaction, it has been found that
these charged particles can be efficiently accelerated. An overview
of these results as well as some perspectives are presented
here.
Analysis of space-resolved X-ray spectra from laser plasmas
Authors: LABATE L. , GALIMBERTI M. , GIULIETTI A. , GIULIETTI D. , GIZZI L.A. , NUMICO R.
Published: December 2002

High dynamic range, space-resolved X-ray spectra, obtained
using a TlAP crystal and a cooled CCD camera as a detector,
were used to investigate the electron density and temperature
profiles of an aluminum laser plasma with micrometer resolution.
The electron density profile retrieved from the measurements
is compared with numerical predictions from the two hydrodynamics
codes MEDUSA (1D) and POLLUX (2D). It is shown that 2D density
profiles can be successfully reproduced by 1D simulations using
a spherical geometry with an ad hoc initial radius, leading
to similar electron temperature profiles.
An approach to the ejection mechanisms of Li atoms from pulsed
excimer laser ablation of a LiNbO3 target
Authors: GORDILLO-VÁZQUEZ F.J.
Published: December 2002

A nonequilibrium kinetic model is used for predicting the time
evolution of the Li atom concentrations (ground and excited
states) in the plasma produced by excimer laser ablation of
a LiNbO3 target. The model predicts a very high
ionization degree (∼0.97) that agrees well with the one
obtained experimentally (∼1). These results together with
the prediction of high (and close to local thermodynamic
equilibrium) population densities of the electronically excited
Li upper energy levels provide an indirect support for an
electronic rather than thermal ablation mechanism of Li atoms.
Pair production via crossed lasers
Authors: FRIED H.M.
Published: December 2002

The intrinsically nonperturbative “vacuum persistence
probability” P for e + e−
production in the overlap region of a pair of high-intensity lasers
is estimated in the context of three models, each of which adapt and
simplify the exact Fradkin representation for the logarithm of the
fermion determinant in the fields of the crossed lasers. In each case,
one finds for P an expression resembling Schwinger's
1951 result for the probability of pair production in a constant
electric field, proportional to an exponential factor which contains
an essential singularity and hence does not admit a perturbative expansion
about zero coupling. Qualitative estimates of these models suggest
that realistic yields for this form of e + e−
production must await lasers of intensity 1029 W/m2.
The possibility of producing a quark–antiquark pair in this way is
noted, in particular, with temporary, but large separations of the
qq.
Proton acceleration by fast electrons in laser–solid
interactions
Authors: DAVIES J.R.
Published: December 2002

The emission of high-energy protons in laser–solid
interactions and the theories that have been used to explain
it are briefly reviewed. To these theories we add a further
possibility: the acceleration of protons inside the target by
the electric field generated by fast electrons. This is considered
using a simple one-dimensional model. It is found that for
relativistic laser intensities and sufficiently long pulse
durations, the proton energy gain is typically several times
the fast electron temperature. The results are very similar
to those obtained for proton acceleration by electron expansion
into vacuum.
Modeling of supersonic jet formation in conical wire array
Z-pinches
Authors: CIARDI A. , LEBEDEV S.V. , CHITTENDEN J.P. , BLAND S.N.
Published: December 2002

Supersonic jet production in conical wire array Z-pinches
is modeled using a two-dimensional (2D) resistive
magneto-hydrodynamic (MHD) code. In conical wire arrays, the
converging plasma ablated from the wires stagnates on axis,
forming a standing conical shock which redirects and collimates
the flow into a jet. As the jet exits the collimator shock,
it is radiatively cooled and accelerated by the steep thermal
gradients present. Purely hydrodynamic simulations using conditions
relevant to the MAGPIE facility show good agreement with the
experiments (Lebedev et al., 2002), indicating that
narrow, high Mach number (M ∼ 20), radiatively cooled
tungsten jets of astrophysical relevance can be obtained. To
investigate the effects of lower radiative cooling on jet collimation,
we modeled an aluminum conical wire array. When radiative losses are
less significant, lower Mach number (M ∼ 10), less collimated
jets are obtained. MHD simulations relevant to the “Z”
facility were carried out to investigate the scaling of jet parameters.
The resulting hypersonic (M ∼ 40), high density jets should
allow the investigation of a wider range of astrophysical jet conditions.
Laser-produced protons and their application as a particle probe
Authors: BORGHESI M. , CAMPBELL D.H. , SCHIAVI A. , WILLI O. , MACKINNON A.J. , HICKS D. , PATEL P. , GIZZI L.A. , GALIMBERTI M. , CLARKE R.J.
Published: December 2002

One of the most exciting results recently obtained in the
ultraintense interaction research area is the observation of
beams of protons with energies up to several tens of megaelectron
volts, generated during the interaction of ultraintense picosecond
pulses with solid targets. The particular properties of these
beams (high brilliance, small source size, high degree of
collimation, short duration) make them of exceptional interest
in view of diagnostic applications. In a series of experiments
carried out at the Rutherford Appleton Laboratory (RAL) and
at the Lawrence Livermore National Laboratory (LLNL), the
laser-produced proton beams have been characterized in view
of their application as a particle probe for high-density matter,
and applied to diagnose ultraintense laser–plasma
interactions. In general, the intensity cross section of a proton
beam traversing matter will be modified both by collisional
stopping/scattering, and deflections caused by electric/magnetic
fields. With a suitable choice of irradiation geometry and target
parameters, the proton probe can be made mainly sensitive to
the electric field distribution in the object probed. Therefore,
point projection proton imaging appears as a powerful and unique
technique for electric field detection in laser-irradiated targets
and plasmas. The first measurements of transient electric fields
in high-intensity laser-plasma interactions have been obtained
with this technique.
Nonequilibrium electron energy distribution in Au under
subpicosecond laser irradiation: A kinetic study
Authors: LONGO S. , PIETANZA L.D. , TASSIELLI F.A. , CAPITELLI M.
Published: December 2002

We have performed a kinetic study of the electron dynamic
relaxation inside a Au film subjected to a subpicosecond laser
pulse. For this purpose, we have developed a time-dependent
numerical solution of the Boltzmann equation for the electrons
inside the film considering the collision integrals due to
electron–electron and electron–phonon collisions
and a perturbation term due to the laser pulse. Our results
show that, after the pulse excitation, electron distributions
are very far from equilibrium. Therefore it is not possible,
especially in the first part of the temporal evolution, to describe
the relaxation of the electron distribution through a
two-temperature model.
Astrophysics in laboratory: Opacity measurements
Authors: CHENAIS-POPOVICS C.
Published: December 2002

Recent measurements of the absorption coefficients of L
transitions in iron and nickel hot plasmas are reported following
a brief review of the published experiments on opacities and
absorption coefficients which have been performed until now
in laser-heated cavities and Z-pinches. Emphasis is
put on the impact of these measurements in astrophysics.
Chromatin structure modification in an excimer laser field
Authors: RADU LILIANA , MIHAILESCU I. , GAZDARU DOINA
Published: December 2002

Chromatin is the complex of deoxyribonucleic acid (DNA) with
proteins that exists in eukaryotic cell nuclei. Chromatin was
extracted from livers of Wistar rats and subjected to a 248-nm
excimer laser radiation, in doses of 0.5–3 MJ/m2.
An UV excimer laser Iofan 1701, with 40-mJ dose/pulse and frequency
of 30 Hz was used. The radiolysis of chromatin was analyzed by (1)
1H-NMR spectroscopy, (2) steady-state fluorescence, (3)
time-resolved fluorescence, and (4) fluorescence resonance energy
transfer (FRET) methods. The laser action on chromatin determines
bigger values of the transverse relaxation time (T2),
which indicates less bound water in the chromatin structure, therefore
a more injured one. The chromatin intrinsic fluorescence decreases
on laser action, proving the destruction of the chromatin protein
structure. By the time-resolved fluorescence we established
that the relative contribution of the excited state lifetime
of bound ethidium bromide to chromatin DNA diminishes with the
laser dose. This denotes single- and double-strand breaks produced
in DNA structure. By the FRET method, the energy transfer
efficiency and the distance between dansyl chloride and acridine
orange coupled at chromatin were determined. The distance increases
with laser action. The determination of the chromatin structure
modification in an excimer laser field can be of real interest
in medical applications.
The spall strength limit of matter at ultrahigh strain rates
induced by laser shock waves
Authors: FORTOV V.E. , BATANI D. , KILPIO A.V. , KRASYUK I.K. , LOMONOSOV I.V. , PASHININ P.P. , SHASHKOV E.V. , SEMENOV A.YU. , VOVCHENKO V.I.
Published: December 2002

New results concerning the process of dynamic fracture of
materials (spallation) by laser-induced shock waves are presented.
The Nd-glass laser installations SIRIUS and KAMERTON were used
for generation of shock waves with pressure up to 1 Mbar in
plane Al alloy targets. The wavelengths of laser radiation were
1.06 and 0.53 μm, the target thickness was changed from
180 to 460 μm, and the laser radiation was focused in a
spot with a 1-mm diameter on the surface of AMg6M aluminum alloy
targets. Experimental results were compared to predictions of
a numerical code which employed a real semiempirical wide-range
equation of state. Strain rates in experiments were changed
from 106 to 5 × 107 s−1.
Two regimes of spallation were evidenced: the already known
dynamic regime and a new quasi-stationary regime. An ultimate
dynamic strength of 80 kbar was measured. Finally, experiments
on targets with artificial spall layers were performed showing
material hardening due to shock-wave compression.
Transport in dense matter of relativistic electrons produced
in ultra-high-intensity laser interactions
Authors: BATANI DIMITRI
Published: December 2002

The paper reviews and analyses the experiments devoted to the
propagation in dense matter of fast electrons produced in the
interaction of short-pulse ultra-high-intensity laser pulses
with solid density targets.
Parametric generation of surface deformations in laser
interaction with overdense plasmas
Authors: MACCHI A. , BATTAGLINI M. , CORNOLTI F. , LISSEIKINA T.V. , PEGORARO F. , RUHL H. , VSHIVKOV V.A.
Published: December 2002

By analytical modeling and numerical simulation, we show that
surface modes in moderately overdense plasmas may be excited
parametrically by an intense, ultrashort laser pulse. This process
has a feedback effect on fast electron generation and may seed
a fast distortion of plasma “moving mirrors.”
A simplistic plasma dust removal model employing radiation pressure
Authors: SCHILL ROBERT A.
Published: December 2002

A simple heuristic model is developed to examine the feasibility
of using radiation pressure as a means to transport plasma dust
out of the path of the forthcoming electron or photon beam.
A slow electromagnetic surface wave coupled to a planar target
or substrate exerts the required pressure in the removal process.
The model is examined using data and parameters from single-shot
radiography experiments. Optimal source requirements are identified
for a typical radiography experiment. Source energies and powers
are a minimum over an optimum band of frequencies where both
conduction and plasma oscillation effects are mutually significant.
Above the band of frequencies, dissipative losses in the surface
supporting the surface wave increases exponentially with frequency.
Below the optimal band, the energy concentration over the plume
at the surface structure decreases significantly with frequency,
thereby requiring higher source energies/powers for plasma removal.
EGALITARIANISM AND WELFARE-STATE REDISTRIBUTION
Authors: Shapiro Daniel
Published: December 2002

A central idea of contemporary philosophical egalitarianism's
theory of justice is that involuntary inequalities or
disadvantages—those that arise through no choice or fault
of one's own—should be minimized or rectified in
some way. Egalitarians believe that the preferred institutional
vehicle for fulfilling these obligations of justice is some
form of a welfare state. Of course, contemporary egalitarians
disagree about the best way to interpret or understand their
theory of justice and institutions: Which inequalities are chosen
and which are unchosen? What form of a welfare state will best
serve justice? However, no contemporary egalitarian denies that
egalitarian justice requires a welfare state that will redistribute
income and wealth to aid the involuntarily disadvantaged.
DOES THE WELFARE STATE HELP THE POOR?
Authors: Cowen Tyler
Published: December 2002

Does the welfare state help the poor? This surprisingly simple
question often generates more heat than light. By the welfare
state, I mean transfer programs aimed at helping the poor through
the direct redistribution of income. (This excludes general
economic policy, antitrust, the volunteer military, and many
other policies that affect the well-being of the poor.) Defenders
of the welfare state often assume that the poor benefit from
it, while critics suggest that the losses outweigh the gains.
The most notable of such criticisms is Charles Murray's
Losing Ground, which suggests that the welfare state
has failed to achieve its stated ends.
THE STAGNATING FORTUNES OF THE MIDDLE CLASS
Authors: Wolff Edward N.
Published: December 2002

The media is aglow with reports of the booming economy and
rising prosperity in the United States since the early 1990s.
Indeed, the run-up in stock prices between 1995 and the end
of 1999 has created the impression that all families are doing
well in terms of income and wealth. This, however, is certainly
not the case. As I shall demonstrate, most American families
have seen their level of well-being stagnate over the last
quarter-century.
INEQUALITY, INCENTIVES, AND OPPORTUNITY
Authors: Deere Donald R. , Welch Finis
Published: December 2002

Measured inequality has increased tremendously between the
1960s and 1990s, not only in the United States but throughout
the majority of industrial nations. Wages among people of the
same race and gender have become less equal. The hours worked
by men have fallen, and the drop has been more pronounced among
those who earn lower wages—as a result, inequality in
labor income, which is the product of the wage rate and hours
worked, has increased relative to inequality in wage rates.
Moreover, among married couples, employment of the
wives of high-income men has increased until these wives are
approximately as likely to be employed outside the home as are
the wives of low-income men, who have always worked for wages.
In addition, due to assortative mating, wage rates of husbands
and wives are positively correlated, and it is clear that the
growth in inequality of labor incomes among families has
outstripped the growth in inequality in individual labor
income. Finally, only the highest-income families have savings
in excess of home equity and company-sponsored pensions, which
implies that inequality in wealth among families has been exacerbated
by the growth in stock prices.
MISUNDERSTANDING DISTRIBUTION
Authors: Choi Young Back
Published: December 2002

Inequality in income and wealth distribution in society is
said to be a great concern to many social critics. Rarely is
the issue of inequality in income or wealth distribution, as
such, a concern for the majority of Americans as individuals,
however.
CAN ANYONE BEAT THE FLAT TAX?
Authors: Epstein Richard A.
Published: December 2002

The inequalities of wealth and fortune form a central part
of the human condition, and these over time have been a constant
source of social unease. Whether they should be praised and
preserved or endured or corrected is an issue that produces
uniform discord. One source of this difficulty in analysis stems
from the possible ways in which these persistent inequalities
arise. It is easy to condemn any differences in wealth created
by the victor's expropriation of the vanquished's
honest toil. It is far more difficult to condemn those identical
differences when they are attributable to the thrift and foresight
of the successful relative to the laziness or self-destructiveness
of the impoverished. Furthermore, most find it morally ambiguous
how best to respond to differences between persons that are
the result of luck or chance, such that they do not reflect
positively or negatively on either the character of those who
have done well or those who have done poorly.
WHY JUSTICE REQUIRES TRANSFERS TO OFFSET INCOME AND WEALTH
INEQUALITIES
Authors: Arneson Richard J.
Published: December 2002

If an array of goods is for sale on a market, one's wealth,
the tradable resources one owns, determines what one can purchase
from this array. One's income is the increment in wealth
one acquires over a given period of time. In any society, we
observe some people having more wealth and income, and some
having less. At any given time, some societies have a greater
average wealth than others. Across time, we can observe societies
becoming richer or poorer and showing more or less equal
distributions of wealth among their members. Does it matter
from an ethical standpoint whether some people have more income
and wealth than others? Does securing a more equal distribution
of income and wealth either constitute the achievement of something
that is intrinsically morally desirable or serve as a reliable
means to the achievement of some intrinsic moral value? If we
suppose that justice demands, in many circumstances, the
equalization of the income or wealth of persons, what principles
of justice generate this demand?
THE IMPORTANCE OF BEING SUFFICIENTLY EQUAL
Authors: Galbraith James K.
Published: December 2002

Neither income nor wealth should be too highly unequal. But
there is a fundamental distinction between pay for work and
the ownership of capital assets. The reasons to moderate these
inequalities therefore differ, and the arguments are best
considered separately.
DOES INEQUALITY MATTER—FOR ITS OWN SAKE?
Authors: Ryan Alan
Published: December 2002

This is a simple essay. It raises a familiar question about
equality, adduces a very small amount of empirical evidence
about the social consequences of equality as distinct
from prosperity, and broods on the difficulty of providing
a really persuasive answer to the question raised. I begin with
the view that there simply cannot be anything intrinsically
wrong with inequality, move on to the view that there are extrinsic
reasons for anxiety, dividing these into conceptual and empirical
reasons, though without any great commitment to the clarity
of that distinction in this context, and end with some reflections
on recent social and political theory. The essay thus begins
with what I hope are clear and (what I am sure are) very simple
thoughts, before muddying the water pretty thoroughly thereafter.
EQUAL RESPECT AND EQUAL SHARES
Authors: Schmidtz David
Published: December 2002

We are all equal, sort of. We are not equal in terms of our
physical or mental capacities. Morally speaking, we are not
all equally good. Evidently, if we are equal, it is not in virtue
of our actual characteristics, but despite them. Our equality
is of a political rather than metaphysical nature. We do not
expect people to be the same, but we expect differences to have
no bearing on how people ought to be treated as citizens. Or
when differences do matter, we expect that they will not matter
in the sense of being a basis for class distinction. We admire
tenacity, talent, and so on, but do not take such features to
entitle their bearers to be treated as “upper class.”
Neither are people who are relatively lacking in these features
obliged to tolerate being treated as “lower class.”
As a society, we have made moral progress. Such progress consists
in part of progress toward political and cultural equality.
TOO MUCH INEQUALITY
Authors: Miller Richard W.
Published: December 2002

It used to seem so simple. In the old days (the seventies and eighties
of the last century), most political philosophers who were inclined to
call themselves “egalitarian” thought that one or another
version of this argument established at least the approximate truth about
economic justice.