209 research outputs found
Enhancing parameters of silicon varactors using laser gettering
The authors investigate how and why defects influence the inverse characteristics of varactors. The paper presents experimental results on the effect laser gettering has on the electrical parameters of varactors. The mechanisms of the laser gettering effect on the parameters of varactors are analyzed.Варикапи широко використовуються в радіоелектроніці як змінна ємність, величина якої управляється напругою. Основними параметрами варикапа є його добротність, номінальна ємність, зворотний струм і коефіцієнт перекриття по ємності, який визначає частотний діапазон використання варикапа. Розробка варикапів зі зворотним градієнтом концентрації домішки в базі дала можливість значно збільшити коефіцієнт перекриття по ємності. При цьому, однак, виникла проблема, пов'язана з низьким виходом придатних приладів через розкид значень номінальної ємності структур по площі пластини, а також високого рівня їх зворотних струмів. Робота присвячена дослідженню впливу структурних дефектів на параметри кремнієвого варикапа зі зворотним градієнтом концентрації домішки в базі і можливості застосування лазерного гетерування для поліпшення його параметрів і підвищення виходу придатних приладів. Встановлено, що головною причиною низького відсотка виходу придатних досліджуваних варикапів є окислювальні дефекти упакування (ОДУ), що утворюються в активних областях структур в процесах проведення високотемпературних операцій. Детально розглянута запропонована технологія виготовлення структур варикапів з лазерним гетеруванням, а також особливості створення області гетера на зворотному боці пластин. Приведено експериментальні результати досліджень впливу лазерного гетерування на електричні параметри варикапів. Показано, що застосування розробленої технології дозволяє запобігти або істотно зменшити щільність ОДУ в активних областях структур, що дає можливість знизити рівень зворотних струмів і зменшити розкид значень номінальної ємності варикапів по площі пластини і, як наслідок, підвищити вихід придатних приладів.Работа посвящена исследованию влияния структурных дефектов на параметры кремниевого варикапа с обратным градиентом концентрации примеси в базе и возможности применения лазерного геттерирования для улучшения его параметров и повышения выхода годных приборов. Установлено, что главной причиной низкого процента выхода годных исследуемых варикапов являются окислительные дефекты упаковки (ОДУ), образующиеся в активных областях структур в процессах проведения высокотемпературных операций. Подробно рассмотрена предложенная технология изготовления структур варикапов с лазерным геттерированием, а также особенности создания области геттера на обратной стороне пластин. Приведены экспериментальные результаты исследований влияния лазерного геттерирования на электрические параметры варикапов. Показано, что применение разработанной технологии позволяет предотвратить или существенно уменьшить плотность ОДУ в активных областях структур, дает возможность снизить уровень обратных токов и уменьшить разброс значений номинальной емкости варикапов по площади пластины и, как следствие, повысить выход годных приборов
Particle interactions with single or multiple 3D solar reconnecting current sheets
The acceleration of charged particles (electrons and protons) in flaring
solar active regions is analyzed by numerical experiments. The acceleration is
modelled as a stochastic process taking place by the interaction of the
particles with local magnetic reconnection sites via multiple steps. Two types
of local reconnecting topologies are studied: the Harris-type and the X-point.
A formula for the maximum kinetic energy gain in a Harris-type current sheet,
found in a previous work of ours, fits well the numerical data for a single
step of the process. A generalization is then given approximating the kinetic
energy gain through an X-point. In the case of the multiple step process, in
both topologies the particles' kinetic energy distribution is found to acquire
a practically invariant form after a small number of steps. This tendency is
interpreted theoretically. Other characteristics of the acceleration process
are given, such as the mean acceleration time and the pitch angle distributions
of the particles.Comment: 18 pages, 9 figures, Solar Physics, in pres
Recent Advances in Understanding Particle Acceleration Processes in Solar Flares
We review basic theoretical concepts in particle acceleration, with
particular emphasis on processes likely to occur in regions of magnetic
reconnection. Several new developments are discussed, including detailed
studies of reconnection in three-dimensional magnetic field configurations
(e.g., current sheets, collapsing traps, separatrix regions) and stochastic
acceleration in a turbulent environment. Fluid, test-particle, and
particle-in-cell approaches are used and results compared. While these studies
show considerable promise in accounting for the various observational
manifestations of solar flares, they are limited by a number of factors, mostly
relating to available computational power. Not the least of these issues is the
need to explicitly incorporate the electrodynamic feedback of the accelerated
particles themselves on the environment in which they are accelerated. A brief
prognosis for future advancement is offered.Comment: This is a chapter in a monograph on the physics of solar flares,
inspired by RHESSI observations. The individual articles are to appear in
Space Science Reviews (2011
Heavy Quarks and Heavy Quarkonia as Tests of Thermalization
We present here a brief summary of new results on heavy quarks and heavy
quarkonia from the PHENIX experiment as presented at the "Quark Gluon Plasma
Thermalization" Workshop in Vienna, Austria in August 2005, directly following
the International Quark Matter Conference in Hungary.Comment: 8 pages, 5 figures, Quark Gluon Plasma Thermalization Workshop
(Vienna August 2005) Proceeding
Single Electrons from Heavy Flavor Decays in p+p Collisions at sqrt(s) = 200 GeV
The invariant differential cross section for inclusive electron production in
p+p collisions at sqrt(s) = 200 GeV has been measured by the PHENIX experiment
at the Relativistic Heavy Ion Collider over the transverse momentum range $0.4
<= p_T <= 5.0 GeV/c at midrapidity (eta <= 0.35). The contribution to the
inclusive electron spectrum from semileptonic decays of hadrons carrying heavy
flavor, i.e. charm quarks or, at high p_T, bottom quarks, is determined via
three independent methods. The resulting electron spectrum from heavy flavor
decays is compared to recent leading and next-to-leading order perturbative QCD
calculations. The total cross section of charm quark-antiquark pair production
is determined as sigma_(c c^bar) = 0.92 +/- 0.15 (stat.) +- 0.54 (sys.) mb.Comment: 329 authors, 6 pages text, 3 figures. Submitted to Phys. Rev. Lett.
Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
Nuclear Modification of Electron Spectra and Implications for Heavy Quark Energy Loss in Au+Au Collisions at sqrt(s_NN)=200 GeV
The PHENIX experiment has measured mid-rapidity transverse momentum spectra
(0.4 < p_T < 5.0 GeV/c) of electrons as a function of centrality in Au+Au
collisions at sqrt(s_NN)=200 GeV. Contributions from photon conversions and
from light hadron decays, mainly Dalitz decays of pi^0 and eta mesons, were
removed. The resulting non-photonic electron spectra are primarily due to the
semi-leptonic decays of hadrons carrying heavy quarks. Nuclear modification
factors were determined by comparison to non-photonic electrons in p+p
collisions. A significant suppression of electrons at high p_T is observed in
central Au+Au collisions, indicating substantial energy loss of heavy quarks.Comment: 330 authors, 6 pages text, 3 figures. Submitted to Phys. Rev. Lett.
Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
Dilepton mass spectra in p+p collisions at sqrt(s)= 200 GeV and the contribution from open charm
The PHENIX experiement has measured the electron-positron pair mass spectrum
from 0 to 8 GeV/c^2 in p+p collisions at sqrt(s)=200 GeV. The contributions
from light meson decays to e^+e^- pairs have been determined based on
measurements of hadron production cross sections by PHENIX. They account for
nearly all e^+e^- pairs in the mass region below 1 GeV/c^2. The e^+e^- pair
yield remaining after subtracting these contributions is dominated by
semileptonic decays of charmed hadrons correlated through flavor conservation.
Using the spectral shape predicted by PYTHIA, we estimate the charm production
cross section to be 544 +/- 39(stat) +/- 142(syst) +/- 200(model) \mu b, which
is consistent with QCD calculations and measurements of single leptons by
PHENIX.Comment: 375 authors from 57 institutions, 18 pages, 4 figures, 2 tables.
Submitted to Physics Letters B. v2 fixes technical errors in matching authors
to institutions. Plain text data tables for the points plotted in figures for
this and previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
Inclusive cross section and double helicity asymmetry for \pi^0 production in p+p collisions at sqrt(s)=200 GeV: Implications for the polarized gluon distribution in the proton
The PHENIX experiment presents results from the RHIC 2005 run with polarized
proton collisions at sqrt(s)=200 GeV, for inclusive \pi^0 production at
mid-rapidity. Unpolarized cross section results are given for transverse
momenta p_T=0.5 to 20 GeV/c, extending the range of published data to both
lower and higher p_T. The cross section is described well for p_T < 1 GeV/c by
an exponential in p_T, and, for p_T > 2 GeV/c, by perturbative QCD. Double
helicity asymmetries A_LL are presented based on a factor of five improvement
in uncertainties as compared to previously published results, due to both an
improved beam polarization of 50%, and to higher integrated luminosity. These
measurements are sensitive to the gluon polarization in the proton, and exclude
maximal values for the gluon polarization.Comment: 375 authors, 7 pages, 3 figures. Submitted to Phys. Rev. D, Rapid
Communications. Plain text data tables for the points plotted in figures for
this and previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
System Size and Energy Dependence of Jet-Induced Hadron Pair Correlation Shapes in Cu+Cu and Au+Au Collisions at sqrt(s_NN) = 200 and 62.4 GeV
We present azimuthal angle correlations of intermediate transverse momentum
(1-4 GeV/c) hadrons from {dijets} in Cu+Cu and Au+Au collisions at sqrt(s_NN) =
62.4 and 200 GeV. The away-side dijet induced azimuthal correlation is
broadened, non-Gaussian, and peaked away from \Delta\phi=\pi in central and
semi-central collisions in all the systems. The broadening and peak location
are found to depend upon the number of participants in the collision, but not
on the collision energy or beam nuclei. These results are consistent with sound
or shock wave models, but pose challenges to Cherenkov gluon radiation models.Comment: 464 authors from 60 institutions, 6 pages, 3 figures, 2 tables.
Submitted to Physical Review Letters. Plain text data tables for the points
plotted in figures for this and previous PHENIX publications are (or will be)
publicly available at http://www.phenix.bnl.gov/papers.htm
Measurement of Transverse Single-Spin Asymmetries for Mid-rapidity Production of Neutral Pions and Charged Hadrons in Polarized p+p Collisions at sqrt(s) = 200 GeV
The transverse single-spin asymmetries of neutral pions and non-identified
charged hadrons have been measured at mid-rapidity in polarized proton-proton
collisions at sqrt(s) = 200 GeV. The data cover a transverse momentum (p_T)
range 0.5-5.0 GeV/c for charged hadrons and 1.0-5.0 GeV/c for neutral pions, at
a Feynman-x (x_F) value of approximately zero. The asymmetries seen in this
previously unexplored kinematic region are consistent with zero within
statistical errors of a few percent. In addition, the inclusive charged hadron
cross section at mid-rapidity from 0.5 < p_T < 7.0 GeV/c is presented and
compared to NLO pQCD calculations. Successful description of the unpolarized
cross section above ~2 GeV/c using NLO pQCD suggests that pQCD is applicable in
the interpretation of the asymmetry results in the relevant kinematic range.Comment: 331 authors, 6 pages text, 2 figures, 3 tables. Submitted to Phys.
Rev. Lett. Plain text data tables for the points plotted in figures for this
and previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
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