bluuebunny/crossref_metadata_2025 huggingface dataset:
Laser Plasma Physics: Forces and the Nonlinearity Principle
Authors: Phipps Claude
Published: November 2002

This is a Landau/Lifschitz-class book. It is a critically
important reference work for the whole field of high intensity
and/or high plasma density laser-plasma interactions for years
to come. It covers everything from single particles to dense
fluids, from computational physics to the practical results
in fusion, accelerators, you name it. It contains excellent
and crystal-clear treatments of the theory of electrodynamics,
laser-driven hydrodynamics, the Lorentz force, complex refractive
index, and relativistic effects in plasmas. Although “the
swamp of plasma physics” is mostly a classical place,
Hora clearly indicates where quantum effects must be considered.
Relativistic laser interactions with preformed plasma channels
and gamma-ray measurements
Authors: GIZZI L.A. , GALIMBERTI M. , GIULIETTI A. , GIULIETTI D. , TOMASSINI P. , BORGHESI M. , CAMPBELL D.H. , SCHIAVI A. , WILLI O.
Published: November 2002

The propagation of a 1-ps laser pulse at intensities exceeding
1019 Wcm−2 in a low-density plasma
channel was experimentally tested. The channel was produced by a
lower intensity preceding pulse of the same duration. Plasma electrons
were accelerated during the propagation of the main pulse, and high
energy γ-ray detectors were used to detect their bremsstrahlung
emission. The γ-ray yield was studied for different channel
conditions, by varying the delay between the channel forming pulse
and the high intensity pulse. These results are correlated with the
interferograms of the propagation region into the plasma.
Angular distributions of fragment ions arising from tetrahedral
CH3I and isomer identification using intense laser fields
Authors: GRAHAM P. , LEDINGHAM K.W.D. , SINGHAL R.P. , HANKIN S.M. , MCCANNY T. , FANG X. , TADAY P.F. , LANGLEY A.J. , KOSMIDIS C.
Published: November 2002

Utilizing an ultraintense (1016 W cm−2)
fs laser, the laser/matter interaction of the tetrahedral CH3I
molecule is investigated. A mass spectrum and the angular distributions
of fragment ions arising from Coulomb explosion of molecular ions,
obtained with linearly polarized light, are presented. The distributions
for In+ (n ≤ 7),
CHm+ (m ≤ 3),
Cp+ (p ≤ 4) and H+ ions
are all anisotropic and maximal when the polarization lies along the
spectrometer axis. The molecule hence seems to behave as a diatomic,
with the fragment ions being ejected along the field direction. Also
presented are mass spectra of the isomers 1- and 2-nitropropane, which
are explosive species, taken for horizontal and vertical polarizations
at both 375 and 750 nm. It is shown that femtosecond laser mass
spectrometry (FLMS) can be used to distinguish between these two isomers
through their differing dissociation patterns. Isomer identification
is important for many different applications and FLMS may provide
a means of achieving this for a wide range of molecules.
Surface modification of W-Ti coatings induced by TEA
CO2 laser beam
Authors: PETROVIĆ SUZANA , GAKOVIĆ B. , TRTICA M. , NENADOVIĆ T.
Published: November 2002

In this work, the interaction of a transversely excited
atmospheric (TEA) CO2 laser with tungsten–titanium
(W-Ti) alloy deposited on austenitic stainless steel is considered.
The W-Ti alloy as a refractory material possesses very good
physicochemical characteristics such as thermochemical stability
and high melting temperature. Studying of interactions of different
energetic particles or laser beams with W-Ti coatings has both
application and fundamental importance.

The morphological features of the W-Ti coating, deposited on
austenitic stainless steel AISI 316, induced by a TEA
CO2 laser after multipulse cumulative laser action,
have been considered. The laser pulses with tail (FWHM = 120
ns, tail = 2 μs) and free-tail pulses (FWHM = 80 ns) have
been employed. Laser pulses used in the experiment had equal
peak power density I = 120 MWcm−2.
For the given peak power density, excessive surface changes
on the coating were registered. From direct observation on a
microscopic scale (OM, SEM), it can be concluded that W-Ti coatings
show different behavior under laser irradiation with various
temporal pulse shapes.
Advanced instrumentation for spectral and spatial investigations
of high-order laser harmonics
Authors: POLETTO LUCA , TONDELLO GIUSEPPE , VILLORESI PAOLO
Published: November 2002

We report on the design and characterization of a
grazing-incidence flat-field spectrograph that allows
simultaneously the measurement of spectrum, beam divergence,
and absolute flux of EUV and soft X-ray radiation for a beam
of high-order laser harmonics generated by the interaction between
an ultrashort femtosecond laser pulse and a gas jet. The instrument
seems a very powerful tool for the understanding of the generation
process.
Ultrafast laser analysis of nitro-PAHs using laser
desorption/femtosecond ionization mass spectrometry
Authors: TASKER A.D. , ROBSON L. , HANKIN S.M. , LEDINGHAM K.W.D. , SINGHAL R.P. , FANG X. , MCCANNY T. , KOSMIDIS C. , TZALLAS P. , LANGLEY A.J. , TADAY P.F. , DIVALL E.J.
Published: November 2002

Analytical interest in nitrated polycyclic aromatic hydrocarbons
(nitro-PAHs) is related to their high mutagenicity and potential
presence in a variety of environmental media such as diesel
exhaust and urban air particulate matter. Furthermore, fundamental
interest in these molecular systems stems from the photophysics
of the labile NO2 functional group, which has been
investigated using mass spectrometry. The nitro-PAHs,
1-nitronaphthalene, 9-nitroanthracene, and 1-nitropyrene, have
been studied using both femtosecond (λ = 395 and 790 nm)
and nanosecond (λ = 266 nm) lasers coupled to a reflectron
time of flight mass spectrometer. Analysis of mass spectra taken
over a range of intensities (1014–1015
W/cm2) has demonstrated that structurally specific ions
can be observed for each molecule, with little or no fragmentation
at lower intensities. It has also been found that an intact parent
ion can be detected using femtosecond ionization at 395 nm in each
case. This work demonstrates the potential use of laser
desorption/femtosecond laser mass spectrometry (LD/FLMS) as an
analytical technique for the detection of nitro-PAHs and other
environmental pollutants and as a means of studying the photodynamics
of labile molecular systems.
Observation of thermonuclear neutrons emitted from dense
femtosecond plasma at moderate intensities
Authors: CHUTKO O.V. , GOLISHNIKOV D.M. , GORDIENKO V.M. , MIKHEEV P.M. , SAVEL'EV A.B. , VOLKOV R.V. , SEVAST'YANOV V.D.
Published: November 2002

We report on the observation of neutrons resulting from a
thermonuclear reaction D + D = 3He(0.82 MeV) +
n(2.45 MeV), taking place in plasma created on the
surface of a modified solid-state target. The plasma was produced
by a 200-fs laser pulse with intensity in excess of 1016
W/cm2 and energy of only 0.3 mJ.
A single-shot third-order autocorrelator for pulse contrast
and pulse shape measurements
Authors: COLLIER J. , HERNANDEZ-GOMEZ C. , ALLOTT R. , DANSON C. , HALL A.
Published: November 2002

We present the design of a single-shot third-order autocorrelator
that can be used to measure optical pulse lengths of ultrashort
pulses within a fixed time window on a single-shot basis. It
has a number of advantages over traditional second-order
autocorrelation devices, namely a more direct and accurate
measurement of pulse shape, the ability to differentiate temporal
activity ahead and behind the pulse, and an increased dynamic
range. The design is linear and is, in principle, no more difficult
to construct and operate than a second-order autocorrelator.
A compact laser-driven accelerator of macroparticles
Authors: POZWOLSKI ALEXANDRE
Published: November 2002

Charged transparent macroparticles of silicium carbide of radius
r = 0.5 μm are submitted to the repeated radiation pressure
of a laser beam which follows the sides of a square 3.5 × 3.5 m,
using total reflection on three prisms. The macroparticles follow a closed
path since they are deflected by a strong electric field, using magnetic
insulation. After 4650 revolutions, velocities up to 106 km/s can be
reached.
Effects of various parameters on numerical simulations of
inertial confinement fusion hohlraum and radiation hydrodynamics
Authors: GUPTA N.K. , GODWAL B.K.
Published: November 2002

In this article, we study the effect of various parameters
on the estimation of radiation temperature inside an indirect
drive ICF hohlraum and also study the hydrodynamics of aluminum
and gold foils driven by the hohlraum radiation. A multigroup
one-dimensional, radiation hydrodynamic code is used for this
study. Opacities are calculated using a screened hydrogenic
average atom model. We also investigate the opacities of Au-Sm
and Au-Gd mixtures. It is shown that the mixing of two high
Z materials can lead to an enhancement in the Rosseland
means, which is of direct interest in indirect-drive inertial
confinement fusion. The radiation temperature inside a cylindrical
hohlraum is seen to be strongly dependent on the number of
frequency groups used. One group radiation transport underpredicts
the radiation temperature. It is shown that erroneous results
can be obtained if the space mesh in the hohlraum wall is not
fine enough. The spectrum of the radiation inside the hohlraum
is seen to be different from Planck, especially in the high-energy
range. This may lead to preheating of the target. Hydrodynamics
of an aluminum foil driven by the hohlraum radiation is also
presented in this article. A scaling law for the radiation-driven
shock-wave speed in the gold foil is obtained.
Implosion experiments of gas-filled plastic-shell targets
with [ell ] = 1 drive nonuniformity at the Gekko-XII glass laser
Authors: HEYA MANABU , SHIRAGA HIROYUKI , SUNAHARA ATSUSHI , NAKASUJI MIKIO , NISHIKINO MASAHARU , HONDA HIROSHI , FUJITA KAZUHISA , IZUMI NOBUHIKO , MIYANAGA NORIAKI , NISHIMURA HIROAKI , AZECHI HIROSHI , NARUO SHUJI , TAKABE HIDEAKI , YAMANAKA TATSUHIKO , MIMA KUNIOKI
Published: November 2002

Effects of an implosion nonuniformity with [ell ] = 1 ([ell ]:
Legendre polynomial mode number) on the hot spark formation
were investigated in a series of direct-drive implosion experiments
at the Gekko-Xll glass laser (Yamanaka et al., 1987).
The implosion dynamics and the performance from the early to
final stage of the implosion were observed with a variety of
X-ray imaging and neutron diagnostics. A drive nonuniformity
in the implosion with [ell ] = 1 was observed in the shape of
the accelerated target at the early stage of the implosion.
At the final stage of the implosion, the resultant nonuniformity
with [ell ] = 1 was also observed as a geometrical shift of core
plasmas from the center of the chamber. The observed neutron
yield and X-ray emission properties at the final stage of the
implosion were significantly degraded with an increase of the
implosion nonuniformity with [ell ] = 1. The experimental results
were compared with one-dimensional (1-D) and two-dimensional
(2-D) hydrodynamic simulations. As a result, it was found that
the implosion nonuniformity with [ell ] = 1 shifts the whole
implosion dynamics towards its direction and prevents the
confinement of the gas fuel considerably. However, the
experimentally observed degradation in the hot spark formation,
such as reductions in neutron yield and features in X-ray emission,
can be reproduced in 2-D simulations not with an asymmetric
perturbation of [ell ] = 1 only but with multimode nonuniformities
such as [ell ] = 1 coupled with some additional middle-mode ones
(e.g., [ell ] = 6). Such a complex spike structure caused by
the multimode nonuniformities was found to be essential for
the experimentally observed rapid cooling of the hot spark.
Wire number breakthrough for high-power annular z
pinches and some characteristics at high wire number
Authors: SANFORD T.W.L.
Published: November 2002

Characteristics of annular wire array z pinches as
a function of wire number and at high wire number are reviewed.
The data, taken primarily using aluminum wires on Saturn, are
comprehensive. The experiments have provided important insights
into the features of wire-array dynamics critical for high X-ray
power generation, and have initiated a renaissance in z
pinches when high numbers of wires are used. In this regime,
for example, radiation environments characteristic of those
encountered during the early pulses required for indirect-drive
ICF ignition on the NIF have been produced in hohlraums driven
by X rays from a z pinch, and are commented on here.
Atomic physics and non-LTE effects
Authors: DAVIS J. , CLARK R. , BLAHA M. , GIULIANI J.L.
Published: November 2002

Pulsed-power-driven z-pinch plasmas are an intense
source of soft X-ray radiation producing, on the Z facility,
about 2 MJ of total radiation for a number of tungsten loads
and in the case of a multiwire titanium array over 1 MJ total
radiation and about 100 kJ from the titanium K-shell.
The production and transport of radiation in these non-LTE plasmas
are often modeled assuming some variation of Local Thermodynamic
Equilibrium (LTE) in conjunction with radiation diffusion. Since
these plasmas are neither in LTE or entirely opaque or transparent
these models do not properly predict the emitted radiation spectra
and yield. Also, application of these models overestimates the
radiation cooling to the extent that the evolving hydrodynamic
profiles are significantly different from those that would obtain
using the appropriate non-LTE model with a more realistic treatment
of the radiation transport. In this investigation, we discuss
the production and transport of radiation from the viewpoint
of the microscopic collisional and radiative processes and then
apply it to z-pinch plasmas. Through the use of examples
and illustrations, it is shown that for identical initial load
conditions, atomic level structure, and rate coefficients, the
models predict different results that affect the dynamic evolution
and hydrodynamic history of the plasma. As an example, the emission
spectrum is generated using a 1-D radiation MHD model
self-consistently coupled to a circuit representing the Sandia
Z facility. A comparison is then made between several standard
models of ionization dynamics for a multiwire titanium array.
Finally, we address some of the issues regarding how the dense
plasma environment influences isolated atom structure and
processes. These include, for example, atomic level shifts,
ionization lowering, collision cross sections, and collision
widths. Transition from the isolated-atom to the dressed-particle
picture can modify the ionization physics and emission spectra
to such an extent that it may challenge our precepts on how
best to design loads for the next generation machine.
Pulse interaction in nonlinear vacuum electrodynamics
Authors: IGNATOV A.M. , POPONIN V.P.
Published: November 2002

The energy-momentum conservation law is used to investigate
the interaction of pulses in the framework of nonlinear
electrodynamics with Lorentz-invariant constitutive relations.
It is shown that for the pulses of the arbitrary shape, the
interaction results in phase shift only.
Transport of electron beams and stability of optical windows
in high-power e-beam-pumped krypton fluoride lasers
Authors: ZVORYKIN V.D. , ARLANTSEV S.V. , BAKAEV V.G. , RANTSEV O.V. , SERGEEV P.B. , SYCHUGOV G.V. , TSERKOVNIKOV A.Yu.
Published: November 2002

Two of the key issues of a krypton fluoride (KrF) laser driver
for inertial fusion energy are the development of long life,
high transparency pressure foils (to isolate vacuum in the electron
beam diode from a working gas in the laser chamber), and the
development of durable, stable, optical windows. Both of these
problems have been studied on the single-pulse e-beam-pumped
KrF laser installation GARPUN. We have measured the transport
of electron beams (300 keV, 50 kA, 100 ns, 10 × 100 cm)
through aluminum-beryllium and titanium foils and compared them
with Monte Carlo numerical calculations. It was shown that
50-μm thickness Al-Be and 20-μm Ti foils had equal
transmittance. However, in contrast to Ti foil, whose surface
was strongly etched by fluorine, no surface modification nor
fatal damages were observed for Al-Be foils after ∼1000
laser shots and protracted fluorine exposure. We also measured
the 8% reduction in the transmission of CaF2 windows
under irradiation by scattered electrons when they were set
at 8.5 cm apart from the e-beam-pumped region. However an applied
magnetic field of ∼0.1 T significantly reduced electron
scattering both across and along the laser cell at typical pumping
conditions with 1.5 atm pressure working gas. Thus the
e-beam-induced absorption of laser radiation in optical windows
might be fully eliminated in an e-beam-pumping scheme with magnetic
field guiding.
A cellular automaton model of laser–plasma interactions
Authors: BATANI DIMITRI , BIAVA SABRINA , BITTANTI SERGIO , PREVIDI FABIO
Published: November 2002

This paper deals with the realization of a CA model of the
physical interactions occurring when high-power laser pulses
are focused on plasma targets. The low-level and microscopic
physical laws of interactions among the plasma and the photons
in the pulse are described. In particular, electron–electron
interaction via the Coulomb force and photon–electron
interaction due to ponderomotive forces are considered. Moreover,
the dependence on time and space of the index of refraction
is taken into account, as a consequence of electron motion in
the plasma. Ions are considered as a fixed background. Simulations
of these interactions are provided in different conditions and
the macroscopic dynamics of the system, in agreement with the
experimental behavior, are evidenced.
Thermonuclear fusion in a multicascade liner staged pinch
Authors: AHMAD ZAHOOR , MIRZA ARSHAD M. , KHATTAK N.A.D. , MURTAZA G.
Published: November 2002

A theoretical model for a multicascade liner system is proposed
with a view to reduce the growth rate of Rayleigh-Taylor (R-T)
instability and to calculate the fusion parameters of a dense
θ-pinch plasma. The dynamics of such plasma has been described
using the modified snow-plow model for sinusoidal and t1/3
types of discharge current profiles. Numerical results demonstrate that
the thermonuclear fusion parameters can be achieved for a dense θ-pinch
deuterium-tritium (D-T) fiber plasma for an optimum choice of
shell thickness. The relevance of this kind of study is possible
use of gas-liner and staged pinches as an alternative source
of thermonuclear fusion.
Editorial
Authors: Hoffmann Dieter H.H.
Published: November 2002

As an important part of my duty and as a first step as incoming
editor to this journal it is a great pleasure for me to thank
Professor George H. Miley for his work that he did for over
a decade as the editor-in-chief of Laser and Particle
Beams. During a period of over 20 years, the field, which
this journal has set out to address, has experienced enormous
progress. George H. Miley steered the journal safely through
uncharted waters and always found a way to keep the delicate
balance between the needs of readers, authors, and the publisher
as well. The journal is now regarded to be highly prestigious
and it is listed among the top ranking scientific journals with
peer review systems. When we compare this journal to others,
we have to keep in mind that it is not made by professional
journalists but rather by fellow scientists for scientists.
During all these years George Miley managed to have this journal
serve the needs of the scientific community and he was very
successful in this difficult enterprise. Thank you George!
State of the development of X-ray lasers and applications at LSAI
Authors: ROS D. , JAMELOT G. , CARILLON A. , JAEGLÉ P. , KLISNICK A. , ZEITOUN P. , RUS B. , JOYEUX D. , PHALIPPOU D. , BOUSSOUKAYA M. , ZEITOUN-FAKIRIS A. , ALBERT F. , FOURCADE P. , HUBERT S. , SEBBAN S. , LAGRON J.-C. , VANBOSTAL L.
Published: November 2002

Obtaining an X-ray laser emission from plasmas, created and
driven by an intense IR laser, has been pursued at the Laboratoire
de Spectroscopie Atomique et Ionique (LSAI) for several years.
At present, we operate various types of X-ray lasers driven
by IR laser pulses of different durations (600 ps, 100 ps, and
600 ps/1 ps). A review of different techniques used at the LSAI
to produce a strongly amplified emission using the collisional
excitation pumping is presented. In the second part of this
paper, to illustrate the potential of the X-ray lasers for
applications, we present the main results obtained with an X-ray
laser emitting at 21.2 nm in a study of surface defects of a
niobium cathode, induced by strong electrical fields. We also
describe a novel imaging interferometry device using an X-ray
laser as a source and designed as a tool for high-resolution
diagnostic of dense plasmas.
Coherent short wavelength radiation via picosecond Nd:glass lasers
Authors: KURODA H. , OZAKI T. , ISHIZAWA A. , KANAI T. , YAMAMOTO K. , LI R. , ZHANG J.
Published: November 2002

The generation of coherent soft X rays is studied using a terawatt
picosecond Nd:glass laser system. Two different methods are
investigated as candidates for efficient generation of such
radiation, namely, longitudinally pumped transient collisional
excitation nickel-like molybdenum X-ray laser, and high-harmonic
generation from solid–vacuum interfaces. In the course
of experiments on longitudinally pumped X-ray lasers, unexpected
jetlike structures are observed in the visible emission of the
molybdenum plasma, extending over a length of several millimeters.
An interesting characteristic of this phenomena is that clear jets
are observed only for longitudinal pump intensities between 5 ×
1014 and 7 × 1014 W/cm2. The
effects of a finite scale length density gradient on surface harmonics
is also investigated. The efficiency of harmonic generation from
near-solid density plasma is found to increase by a factor of 2 to 3
when using prepulses. The scale length of the preplasma is simulated
using a one-dimensional hydrodynamic code, and the increase in efficiency
is verified to be in accordance with particle-in-cell simulation results.
Laser-generated pair production and Hawking–Unruh radiation
Authors: HORA HEINRICH , OSMAN FREDERICK , CASTILLO REYNALDO , COLLINS MATTHEW , STAIT-GARDENER TIMOTHY , CHAN WAI-KIM , HÖLSS MANUEL , SCHEID WERNER , WANG JIA-XIANG , HO YU-KUN
Published: November 2002

Laser-produced electron–positron pair production has
been under discussion in the literature since 1969. Large numbers
of positrons have been generated by lasers for a few years in
studies which are also related to the studies of the physics
of the fast ignitor laser fusion concept. For
electron–positron pair production in vacuum due to vacuum
polarization as predicted by Heisenberg (1934) with electrostatic
fields, high-frequency laser fields with intensities around
1028 W/cm2 are necessary and may be available
within a number of years. A similar electron acceleration by
gravitation near black holes denoted as Hawking–Unruh
radiation was discussed in 1985 by McDonald. The conditions
are considered in view of the earlier work on pair production,
change of statistics for electrons in relativistic black body
radiation, and an Einstein recoil mechanism with a consequence
of a physical foundation of the fine structure constant.
Laser-induced tension to measure the ultimate strength of
metals related to the equation of state
Authors: ELIEZER SHALOM , MOSHE ELLA , ELIEZER DAN
Published: November 2002

The approach to the ultimate strength of metals is determined
experimentally. The strength of the materials and the strain
rate were determined from the free surface velocity time history,
which was measured with an optically recording velocity
interferometer system. The dynamic strength was measured at
strain rates in the domain of 5·106 to 5·108 s−1. The necessary
tension to break the metal (spall) and the very high strain
rates were achieved using high-powered lasers in nanosecond
and picosecond regimes. The measurements at strain rates larger
than 108 s−1 were achieved for the
first time. The ultimate strength of metals was calculated using
a realistic wide-range equation of state. Our experiments indicate
that under very fast tension processes, the dynamic strength of materials
is determined not by the macroscopic defects but by atomic quantum
mechanical processes described by the equation of state of the
material. The rate of the process is described by the strain
rate, and at strain rates higher than 5·107
s−1, the atomic forces are dominating the dynamic
strength of materials.
Anomalous skin effect for linearly and circularly polarized
intense laser light
Authors: NAKAMURA TATSUFUMI , KATO SUSUMU , KATO TOMOKAZU
Published: November 2002

Anomalous absorption of an intense short laser pulse in overdense
plasmas is analyzed with a stochastic theory. A diffusion equation
describing a time evolution of the electron distribution function
is derived. From the equation it is shown that the electron
distribution function becomes anisotropic in the momentum space,
which gives rise to the absorption of the energy. The diffusion
is not dominant in the pz direction,
which is longitudinal to the vacuum-plasma boundary, rather it is
dominant in the px direction, which is
transverse to the boundary. However, the diffusion in
pz enhances the absorption. Analytical
expressions of the absorption coefficient and skin depth are obtained
for the anomalous skin effect regime (ω02c2 <<
ωp2ve2),
which evolves in time as the electron distribution becomes
anisotropic. The asymptotic value of the absorption coefficient is
proportional to [square root]I. The temperature and density
dependence of the absorption coefficient is also discussed.
Expansion of tungsten ions emitted from laser-produced plasma
in axial magnetic and electric fields
Authors: WOŁOWSKI J. , CELONA L. , CIAVOLA G. , GAMMINO S. , KRÁSA J. , LÁSKA L. , PARYS P. , ROHLENA K. , TORRISI L. , WORYNA E.
Published: November 2002

The experimental results of the investigations on the influence
of external magnetic and electric fields on the characteristics
of a tungsten ion stream emitted from a plasma produced by the
Nd:glass laser (1 J, 1 ns) performed at IPPLM, Warsaw are
presented. A negatively biased target up to −15 kV and
a magnetic field up to 0.45 T were used in the experiment. A
set of ion collectors and an electrostatic cylindrical ion energy
analyzer located at small angles with respect to the laser beam
axis and at large distances from the target were applied for
ion measurements. The effect of an external magnetic field is
essential to plasma expansion, but the effect of the retarding
potential of the target is very weak in our experimental
conditions. The aim of the studies was to prove the possibility
of the optimization of ion beam parameters from laser-produced
plasma for the particular application as a laser ion source
coupled with the electron cyclotron resonance ion source for
particle accelerators.
Activities of developing high-power KrF lasers and studying
laser plasmas interaction physics at CIAE
Authors: WANG NAIYAN , SHAN YUSHENG , MA WEIYI , YANG DAWEI , KUN GONG , WANG XIAOJUN , TANG XIUZHANG , TAO YEZHENG , MA JINGLONG , JIANG XINGDONG
Published: November 2002

This report reviews the scientific activities on high power
laser and laser plasma physics at CIAE. A 6-beam KrF excimer
laser system (100 J/23 ns/248 nm/1013 W/cm2, 15
min/shot) has been built, the Raman technologies used to upgrade
it to 1014 W/cm2 has been studied. A UV femtosecond
Ti:sapphire/KrF hybrid laser (50 mJ/220 fs/248 nm/1017 W/cm2) has been developed also, hot electron generation
research has been carried out in the fs laser. In the near future,
the fs laser will be amplified in six-beam laser system to produce
ultra-high intensity to do fundamental researches on Fast Ignition
of ICF.
A six-beam high-power KrF excimer laser system with energy
of 100 J/23 ns
Authors: SHAN YUSHENG , WANG NAIYAN , MA JINGLONG , MA WEIYI , YANG DAWEI , GONG KUN , TANG XIUZHANG , WANG XIAOJUN , JANG XINGDONG , TAO YEZHENG
Published: November 2002

A six-beam multiplexing master-oscillator-power-amplifier (MOPA)
high power KrF excimer laser system has been built at CIAE for
fundamental research on laser–plasma interaction. The
MOPA system consists of front-end, two-stage KrF amplifiers
(preamplifier and main amplifier) pumped by two-side electron
beams, an optical angular multiplexing system, a synchronization
trigger system, and a controlling-data acquisition system and
some diagnostic systems. The total energy of the six-beam output
from main amplifier on the target is 100 J/23 ns, the divergence
of one beam is 0.2 mrad, the focal spot diameter is 220 μm, and
the focal intensity on the target is 1013 W/cm2.
Express method of estimating laser-induced surface damage
threshold for optical components
Authors: SIRAZETDINOV V.S. , ALEKSEEV V.N. , DMITRIEV D.I. , CHARUKHCHEV A.V. , CHERNOV V.N. , KOTILEV V.N. , LIBER V.I. , RUKAVISHNIKOV N.N.
Published: November 2002

The present measurements of the components' surface
resistance to laser-induced damage has been completed to facilitate
development and construction of the “Luch” laser
system, a four-channel Nd-phosphate glass laser with a full
output energy of E = 14–16 kJ. The study describes
a method that, with a series of experimental data obtained from
a single sample, allows us not only to estimate the threshold
fluences, but to take into account the statistical nature of
the surface damage. In a number of experimental situations this
method makes it possible to estimate damaging fluences even
from the result of a single exposure of the studied surface.
Estimated threshold fluences for various optical elements are
presented: K8 glass, experimental phosphate laser glass KGSS-0180,
high-reflecting and antireflecting thin-film coating of elements.
The 1.054-μm radiation pulse with half-height duration of
4 ns and the irradiation spot of ∼4 mm in diameter were
used in the experiment.
COMPARISONS BETWEEN CERTAIN QUEUING SYSTEMS
Authors: Lindvall Torgny
Published: November 2002

We use a Poisson imbedding technique to investigate the
possibilities of generalizing some pathwise and stochastic
monotonicity results from the M/M/k
queues to systems with monotone failure rate service time
distribution. A dichotomy between the decreasing failure rate
(DFR) and the increasing failure rate (IFR) cases is revealed:
In the DFR case, we achieve that the number of customers in
the systems is stochastically increasing if it is idle at time
0, whereas in the IFR case, there is an alternating character
that renders a bound between two identical systems that have
different initial conditions. We also explore how our methods
work in a comparison between systems with different numbers
of stations but the same maximal capacity.
AN IDENTITY OF THE GI/G/1 TRANSIENT DELAY
AND ITS APPLICATIONS
Authors: Wang Chia-Li
Published: November 2002

We consider a single-server queue that is initially empty and
operates under the first-in–first-out service discipline.
In this system, delays (waiting times in queue) experienced
by subsequent arriving customers form a transient process. We
investigate its transient behavior by constructing a sample-path
coupling of the transient and a general (delayed) processes.
From the coupling, we obtain an identity that relates the sample
paths of these two processes. This identity helps us to better
understand the queue's approach to the stationary limit
and to derive upper and lower bounds on the expected transient
delay. In addition, we use a Brownian-motion model to approximate
the identity. This produces an approximation of the expected
transient delay. The approximation turns out to be identical
to the corresponding first moment of a reflected Brownian motion.
Thus, it is easy to compute and its accuracy is supported by
numerical experiments.
CLASSIFICATION OF MULTIVARIATE LIFE DISTRIBUTIONS BASED ON
PARTIAL ORDERING
Authors: Roy Dilip
Published: November 2002

Barlow and Proschan presented some interesting connections
between univariate classifications of life distributions and
partial orderings where equivalent definitions for increasing
failure rate (IFR), increasing failure rate average (IFRA),
and new better than used (NBU) classes were given in terms of
convex, star-shaped, and superadditive orderings. Some related
results are given by Ross and Shaked and Shanthikumar. The
introduction of a multivariate generalization of partial orderings
is the object of the present article. Based on that concept
of multivariate partial orderings, we also propose multivariate
classifications of life distributions and present a study on
more IFR-ness.
A MARKOV RENEWAL APPROACH TO THE ASYMPTOTIC DECAY OF THE
TAIL PROBABILITIES IN RISK AND QUEUING PROCESSES
Authors: Miyazawa Masakiyo
Published: November 2002

It is well known that various characteristics in risk and queuing
processes can be formulated as Markov renewal functions, which
are determined by Markov renewal equations. However, those
functions have not been utilized as they are expected. In this
article, we show that they are useful for studying asymptotic
decay in risk and queuing processes under a Markovian environment.
In particular, a matrix version of the Cramér–Lundberg
approximation is obtained for the risk process. The corresponding
result for the MAP/G/1 queue is presented
as well. Emphasis is placed on a straightforward derivation
using the Markov renewal structure.
HITTING TIME IN AN ERLANG LOSS SYSTEM
Authors: Ross Sheldon M. , Seshadri Sridhar
Published: November 2002

In this article, we develop methods for estimating the expected
time to the first loss in an Erlang loss system. We are primarily
interested in estimating this quantity under light traffic
conditions. We propose and compare three simulation techniques
as well as two Markov chain approximations. We show that the
Markov chain approximations proposed by us are asymptotically
exact when the load offered to the system goes to zero. The
article also serves to highlight the fact that efficient estimation
of transient quantities of stochastic systems often requires
the use of techniques that combine analytical results with simulation.
ON PARALLEL QUEUING WITH RANDOM SERVER CONNECTIVITY AND ROUTING
CONSTRAINTS
Authors: Bambos Nicholas , Michailidis George
Published: November 2002

We study systems of parallel queues with finite buffers, a
single server with random connectivity to each queue,
and arriving job flows with random or class-dependent
accessibility to the queues. Only currently connected queues
may receive (preemptive) service at any given time, whereas
an arriving job can only join one of its accessible queues.
Using the coupling method, we study three key models,
progressively building from simpler to more complicated structures.

In the first model, there are only random server connectivities.
It is shown that allocating the server to the Connected queue
with the Fewest Empty Spaces (C-FES) stochastically minimizes
the number of lost jobs due to buffer overflows, under conditions
of independence and symmetry.

In the second model, we additionally consider random accessibility
of queues by arriving jobs. It is shown that allocating the
server to the C-FES and routing each arriving job to the currently
Accessible queue with the Most Empty Spaces (C-FES/A-MES) minimizes
the loss flow stochastically, under similar assumptions.

In the third model (addressing a target application), we consider
multiple classes of arriving job flows, each allowed
access to a deterministic subset of the queues. Under analogous
assumptions, it is again shown that the C-FES/A-MES policy
minimizes the loss flow stochastically.

The random connectivity/accessibility aspect enhances
significantly the structure and application scope of the classical
parallel queuing model. On the other hand, it introduces essential
additional dynamics and considerable complications. It is
interesting that a simple policy like FES/MES, known to be optimal
for the classical model, extends to the C-FES/A-MES in our case.
DISCRETE TIME RISK MODELS UNDER RATES OF INTEREST
Authors: Cai Jun
Published: November 2002

Two discrete time risk models under rates of interest are
introduced. Ruin probabilities in the two risk models are
discussed. Stochastic inequalities for the ruin probabilities
are derived by martingales and renewal recursive techniques.
The inequalities can be used to evaluate the ruin probabilities
as upper bounds. Numerical illustrations for these results are
given.
PRODUCTION-INVENTORY MODELS WITH AN UNRELIABLE FACILITY
OPERATING IN A TWO-STATE RANDOM ENVIRONMENT
Authors: Perry David , Posner M.J.M.
Published: November 2002

We consider two model variants of a production-inventory system.
The system is characterized by a producing machine which is
susceptible to failure following which it must be repaired to
make it operative again. The machine's production can also
be stopped deliberately because of stocking capacity limitations.
During ON periods the input into the buffer is continuous and
uniform (until a threshold is reached), whereas during OFF periods
the output from the buffer is a compound Poisson process. We
are interested in computing the equilibrium content level process
under the assumption that full backlogging is allowed. In the
first model, variant OFF periods are independent of the demand
process, and in the second variant, they are determined and
controlled in accordance with a certain level crossing stopping
rule.
OPTIMAL CONTROL OF A TWO-STAGE TANDEM QUEUING SYSTEM WITH
FLEXIBLE SERVERS
Authors: Ahn Hyun-soo , Duenyas Izak , Lewis Mark E.
Published: November 2002

We consider the optimal control of two parallel servers in
a two-stage tandem queuing system with two flexible servers.
New jobs arrive at station 1, after which a series of two
operations must be performed before they leave the system. Holding
costs are incurred at rate h1 per unit time
for each job at station 1 and at rate h2 per
unit time for each job at station 2.

The system is considered under two scenarios; the collaborative
case and the noncollaborative case. In the prior, the servers
can collaborate to work on the same job, whereas in the latter,
each server can work on a unique job although they can work
on separate jobs at the same station. We provide simple conditions
under which it is optimal to allocate both servers to station
1 or 2 in the collaborative case. In the noncollaborative case,
we show that the same condition as in the collaborative case
guarantees the existence of an optimal policy that is exhaustive
at station 1. However, the condition for exhaustive service
at station 2 to be optimal does not carry over. This case is
examined via a numerical study.
STOCHASTIC ORDERINGS BETWEEN SPACINGS OF GENERALIZED ORDER
STATISTICS
Authors: Franco Manuel , Ruiz José M. , Ruiz M. Carmen
Published: November 2002

In this article, we establish stochastic comparisons between
normalized spacings of generalized order statistics. These
comparisons allow us to extend and unify some results obtained
by other authors for ordinary order statistics and record values.
Furthermore, we can compare spacings of different models (i.e.,
between ordinary order statistics and sequential order statistics,
record values and Pfeifer's record values, and so forth).
WHAT IS A UNIT OF CAPACITY WORTH?
Authors: Chiera B.A. , Taylor P.G.
Published: November 2002

Consider a finite-capacity telecommunications link to which
connection requests arrive in a Poisson process. Each connection
carried on the link earns a certain amount of revenue for the
link's manager. Now, assume that the manager is offered
the opportunity to buy or sell a unit of the link's allocated
capacity. Assuming that the manager has a knowledge of the current
number of connections on the link, we demonstrate a method of
calculating the buying and selling prices.
A multilocality study of a sound change in progress: The
case of /l/ vocalization in New Zealand and Australian English
Authors: Horvath Barbara M. , Horvath Ronald J.
Published: November 2002

It is usual to study a number of linguistic variables in a
single speech community. The present study, however, focuses
on a single phonological variable in a number of speech
communities—the vocalization of /l/ in nine Australian
and New Zealand cities—in order to (1) strengthen and
extend the quick and anonymous field method by designing an
instrument to include all relevant phonological environments;
(2) demonstrate the strategic potential of moving from a
unilocality to a multilocality sociolinguistics; (3) conceptualize
a variationist isogloss that extends rather than displaces the
core methodology of sociolinguistics; and (4) propose a conception
of geography that offers mechanisms (space and place effects)
to help distinguish language change processes that are universal
from those that are not. Place and space represent a system
of contrasts within geography. Place effects refer to the ensemble
of sociolinguistic conditions within a speech locality, whereas
space effects refer to the relationship between speech localities.
Place effects provide a potential explanation for why spatial
models fail to account adequately for the facts: that is, why
some places resist the spread of innovation while other places
welcome innovation.
Phrase-level parallelism effect on noun phrase number agreement
Authors: Scherre Maria Marta Pereira
Published: November 2002

Linguistic parallelism (i.e., the tendency of similar forms
to occur together within a stretch of discourse) has been shown
to be very strong in many linguistic phenomena and in a vast
number of languages. Examining the role of phrase-level parallelism
on noun phrase number agreement, this article demonstrates that
Puerto Rican Spanish and Brazilian Portuguese exhibit more
similarities than differences with regard to this constraint.
A detailed analysis of Brazilian Portuguese data is presented,
and the results are compared with those found by Poplack (1980a)
for Puerto Rican Spanish. Guy's (1981a) and Labov's
(1994) hypothesis about missing zeroes in Brazilian Portuguese
is also discussed. In conclusion, it is claimed that the
phrase-level parallelism effect on noun phrase number agreement
is embedded in a universal principle of linguistic use: parallel
processing.
Yod deletion in Fiji English: Phonological shibboleth or
L2 English?
Authors: Tent Jan
Published: November 2002

It is not difficult to find grammatical and lexical markers
of Fiji English. But are there any phonological features that
identify an individual as a speaker of this regional variety
of English? For the vast majority of Fiji Islanders, English
is their second (or third) language, and their accents clearly
identify their linguistic background (e.g., indigenous Fijian
or Indo-Fijian). However, one pronunciation feature seems to
be shared by a vast majority of speakers of English in Fiji:
the deletion of yod in non-primary stressed /Cju/ syllables.
This article considers variation in yod pronunciation according
to ethnicity, age, gender, and education and examines whether
yod deletion is a phonological shibboleth of Fiji English or
merely a feature of L2 English.
RISK SENSITIVITY, A STRANGELY PERVASIVE CONCEPT
Authors: Whittle Peter
Published: November 2002

The theme of this paper is that the simple concept of risk sensitivity raises ideas, shows associations, and forces clarification of issues that one would have thought quite unrelated.
DOES MODEL UNCERTAINTY JUSTIFY CAUTION? ROBUST OPTIMAL MONETARY POLICY IN A FORWARD-LOOKING MODEL
Authors: Giannoni Marc P.
Published: November 2002

This paper proposes a general method based on a property of zero-sum two-player games to derive robust optimal monetary policy rules—the best rules among those that yield an acceptable performance in a specified range of models—when the true model is unknown and model uncertainty is viewed as uncertainty about parameters of the structural model. The method is applied to characterize robust optimal Taylor rules in a simple forward-looking macroeconomic model that can be derived from first principles. Although it is commonly believed that monetary policy should be less responsive when there is parameter uncertainty, we show that robust optimal Taylor rules prescribe in general a stronger response of the interest rate to fluctuations in inflation and the output gap than is the case in the absence of uncertainty. Thus model uncertainty does not necessarily justify a relatively small response of actual monetary policy.
MODEL UNCERTAINTY, ROBUST POLICIES, AND THE VALUE OF COMMITMENT
Authors: Kasa Kenneth
Published: November 2002

Using results from the literature on H∞ control, this paper incorporates model uncertainty into a frequency-domain approach to stabilization policy. The derived policies guarantee a minimum performance level even in the worst of (a bounded set of) circumstances. Robust H∞ policies are shown to be more “activist” than H2 policies in the sense that their impulse responses are larger. Robust policies also tend to be more autocorrelated. Consequently, the premium associated with being able to commit is greater under model uncertainty. Without commitment, the policymaker is not able to (credibly) smooth his response to the degree that he would like. A contribution of this paper is its analysis of robust control in a model featuring a forward-looking state transition equation, which arises from the fact that the private sector bases its decisions on expectations of future government policy. Existing applications of H∞ control in economics follow the engineering literature, and only consider backward-looking state transition equations.
THE SHARPE RATIO AND PREFERENCES: A PARAMETRIC APPROACH
Authors: Lettau Martin , Uhlig Harald
Published: November 2002

We use a log-normal framework to examine the effect of preferences on the market price for risk, that is, the Sharpe ratio. In our framework, the Sharpe ratio can be calculated directly from the elasticity of the stochastic discount factor with respect to consumption innovations as well as the volatility of consumption innovations. This can be understood as an analytical shortcut to the calculation of the Hansen–Jagannathan volatility bounds, and therefore provides a convenient tool for theorists searching for models capable of explaining asset-pricing facts. To illustrate the usefulness of our approach, we examine several popular preference specifications, such as CRRA, various types of habit formation, and the recursive preferences of Epstein–Zin–Weil. Furthermore, we show how the models with idiosyncratic consumption shocks can be studied.
STRUCTURAL INFERENCE WITH LONG-RUN RECURSIVE EMPIRICAL MODELS
Authors: Keating John W.
Published: November 2002

This paper investigates conditions under which a long-run recursive model can be used to identify a structure. Economists frequently employ this type of empirical model. I define the class of long-run partially recursive structures. If an economic system is a member of this class, then certain long-run recursive empirical models will obtain some of the structural impulse response functions. This sufficient condition for a structure is first shown in a vector autoregression. A well-known example from the literature is used to illustrate this particular class of structures and to present some useful applications of the result. Then the result is shown in models of cointegrated time series. Necessary conditions for a long-run recursive model to identify structure are addressed in the conclusion.