232 research outputs found
Some practical considerations for economical back contact formation on high efficiency solar cells
The back contact can detract from solar cell performance in a number of ways: high recombination, barrier, photovoltaic, minority carrier collection, resistance. These effects may act in a nonuniform fashion over the cell area, and complicate the analysis of photovoltaic performance aimed at a better understanding of the effects of device geometry and material and/or processing parameters. The back contact is tested by reproducing it on both sides of a substrate. The objective is to find a back contact which performs well as a back contact, can be applied cheaply to large area solar cells, fits well into a practical process sequence, does not introduce structural damage or undesirable impurities into the silicon substrate, is compatible with an effective front contact technology, permits low temperature solder contacting, adheres well to silicon, and is reliable
Phase 1 of the automated array assembly task of the low cost silicon solar array project
The state of technology readiness for the automated production of solar cells and modules is reviewed. Individual process steps and process sequences for making solar cells and modules were evaluated both technically and economically. High efficiency with a suggested cell goal of 15% was stressed. It is concluded that the technology exists to manufacture solar cells which will meet program goals
Exploring QCD at small sea quark masses with improved Wilson-type quarks
We explore the region of small sea quark masses below in
two-flavor QCD using a mean-field improved clover quark action and an
RG-improved gauge action at fm on and lattices. We find that instability of the standard BiCGStab
algorithm at small quark masses can be mostly removed by the BiCGStab(DS-)
algorithm, which employs -th minimal residual polynomials with a dynamical
selection of . We also find singular spikes of in the HMC
algorithm at moderate values of . Nature of the spike is studied.
We also study finite-size effects and chiral properties of meson masses.Comment: 3 pages, 4 figures, Lattice2002(spectrum
I=2 pion-pion scattering phase shift in the continuum limit calculated with two-flavor full QCD
We present a calculation of the scattering phase shift for the I=2 S-wave
pion-pion system in the continuum limit with two-flavor full QCD. Calculations
are made at three lattice spacings, using the finite volume method of L\"uscher
in the center of mass frame, and its extension to the laboratory frame.Comment: Lattice2003(spectrum), 3 page
Dynamical fermions on anisotropic lattices
We report on our study of two-flavor full QCD on anisotropic lattices using
-improved Wilson quarks coupled with an RG-improved glue. The bare gauge
and quark anisotropies corresponding to the renormalized anisotropy
are determined as functions of and , using
the Wilson loop and the meson dispersion relation at several lattice cutoffs
and quark masses.Comment: Lattice2002(improve), 3 pages, 3 figure
I=2 Pion Scattering Phase Shift with Wilson Fermions
We present a lattice QCD calculation of the scattering phase shift for the
I=2 -wave two-pion system using the finite size method proposed by
L\"uscher. We work in the quenched approximation employing the standard
plaquette action at for gluons and the Wilson fermion action for
quarks. The phase shift is extracted from the energy eigenvalues of the
two-pion system, which are obtained by a diagonalization of the pion 4-point
function evaluated for a set of relative spatial momenta. In order to change
momentum of the two-pion system, calculations are carried out on , , and lattices. The phase shift is
successfully calculated over the momentum range .Comment: LaTeX, 28 pages, 10 eps figures, uses revtex and epsfi
Two flavors of dynamical quarks on anisotropic lattices
We report on our study of two-flavor full QCD on anisotropic lattices using
-improved Wilson quarks coupled with an RG-improved glue. The bare gauge
and quark anisotropies corresponding to the renormalized anisotropy
are determined as functions of and , which
covers the region of spatial lattice spacings --0.16 fm and
--0.9. The calibrations of the bare anisotropies are
performed with the Wilson loop and the meson dispersion relation at 4 lattice
cutoffs and 5--6 quark masses. Using the calibration results we calculate the
meson mass spectrum and the Sommer scale . We confirm that the values of
calculated for the calibration using pseudo scalar and vector meson
energy momentum dispersion relation coincide in the continuum limit within
errors. This work serves to lay ground toward studies of heavy quark systems
and thermodynamics of QCD including the extraction of the equation of state in
the continuum limit using Wilson-type quark actions.Comment: 16 pages, 23 figures, Version accepted for publication in Physical
Review
Light hadron spectroscopy in two-flavor QCD with small sea quark masses
We extend the study of the light hadron spectrum and the quark mass in
two-flavor QCD to smaller sea quark mass, corresponding to
--0.35. Numerical simulations are carried out using the
RG-improved gauge action and the meanfield-improved clover quark action at
( fm from meson mass). We observe that the light
hadron spectrum for small sea quark mass does not follow the expectation from
chiral extrapolations with quadratic functions made from the region of
--0.55. Whereas fits with either polynomial or continuum
chiral perturbation theory (ChPT) fails, the Wilson ChPT (WChPT) that includes
effects associated with explicit chiral symmetry breaking successfully
fits the whole data: In particular, WChPT correctly predicts the light quark
mass spectrum from simulations for medium heavy quark mass, such as m_{PS}/m_V
\simgt 0.5. Reanalyzing the previous data %at --0.55 with
the use of WChPT, we find the mean up and down quark mass being smaller than
the previous result from quadratic chiral extrapolation by approximately 10%,
[MeV] in the continuum limit.Comment: 33 page
Non-perturbative renormalization for a renormalization group improved gauge action
Renormalization constants of vector () and axial-vector () currents
are determined non-perturbatively in quenched QCD for a renormalization group
improved gauge action and a tadpole improved clover quark action using the
Schr\"odinger functional method. Non-perturbative values of and
turn out to be smaller than the one-loop perturbative values by at
GeV. A sizable scaling violation of meson decay constants
and observed with the one-loop renormalization factors remains
even with non-perturbative renormalization.Comment: Lattice2001(improvement), 3 pages, 7 figure
- …