共查询到20条相似文献,搜索用时 15 毫秒
1.
R. G. C. Oldeman M. Meloni B. Saitta 《The European Physical Journal C - Particles and Fields》2010,65(1-2):81-87
Antineutrino induced electron capture is a resonant process that can have a large cross-section for beams of monochromatic antineutrinos. We calculate the cross-section of this process and investigate an experimental setup where monochromatic antineutrinos are produced from the bound-beta decay of fully ionized radioactive atoms in a storage ring. If the energy between the source and the target is well matched, the cross-sections can be significantly larger than the cross-sections of commonly used non-resonant processes. The rate that can be achieved at a small distance between the source and two targets of 103?kg is up to one interaction per 8.3?1018 decaying atoms. For a source-target distance corresponding to the first atmospheric neutrino oscillation maximum, the largest rate is one interaction per 3.2?1021 decaying atoms, provided that extremely stringent monochromaticity conditions (10?7 or better) are achieved in future ion beams. 相似文献
2.
N. G. C. Astrath F. B. G. Astrath J. Shen J. Zhou C. E. Gu L. C. Malacarne P. R. B. Pedreira A. C. Bento M. L. Baesso 《Applied physics. B, Lasers and optics》2009,94(3):473-481
A complete theoretical model is presented for the thermal mirror technique under top-hat laser excitation. Considering the
attenuation of the top-hat excitation laser intensity along the thickness of a sample due to its optical absorption coefficient,
we calculate the laser-induced temperature and surface deformation profiles. A simplified theoretical model for a high absorption
sample is also developed. The center intensity of a probe beam reflected from the thermal mirror at a detector plane is derived.
Numerical simulation shows that the thermal mirror under the top-hat laser excitation is as sensitive as that under Gaussian
laser excitation. With top-hat laser excitation, the experimental results of thermo-physical properties of opaque samples
are found to be well consistent with literature values, validating the theory. 相似文献
3.
Jobin K. Antony Gurneesh Singh Jatana Nilesh J. Vasa V. L. N. Sridhar?Raja A. S. Laxmiprasad 《Applied Physics A: Materials Science & Processing》2010,101(1):161-165
Laser Induced Breakdown Spectroscopy (LIBS) can be considered as a prominent technology for compositional analysis of materials
in low-pressure space applications. In space applications, usually LIBS is conducted in a low-pressure environment and proper
understanding of the plasma parameters is significant for any improvement in the system. A model is developed to describe
the heating and subsequent melting, vaporization and ionization of a target material during LIBS process. A numerical model
based on one-dimensional thermal conductivity equation is being used to simulate the target evaporation and a hydrodynamic
model is used to simulate plume expansion. Further, an experimental approach of measuring spectral emission from the ablation
plume using emission spectroscopy and estimating the plasma state, such as the ionization species, and average plasma temperature,
is investigated. An important result of this work is that for different ambient conditions, laser ablation plume dynamics
can be estimated. 相似文献
4.
Anne Sickles 《The European Physical Journal C - Particles and Fields》2009,61(4):583-588
These proceedings review recent results from two and three particle correlations in heavy ion collisions. In particular we
discuss the modified structure of the away side jet correlations. Under the assumption that the away side can be decomposed
into a punch through component at Δ
φ=π and a shoulder component with a peak displaced from π many similar properties are observed between the ridge and shoulder. The particle ratios, yields and p
T
spectra are in near agreement. We also highlight important future measurements, including investigating if the decomposition
of the away side jet correlations remains reasonable with high p
T
triggers and technical improvements to the extraction of jet induced correlations. 相似文献
5.
E. Takahashi S. Kato Y. Matsumoto I. Okuda 《Applied physics. B, Lasers and optics》2010,98(2-3):501-505
External-laser-induced preionization of excimer lasers was investigated. A discharge XeF laser was preionized by two different UV lasers [a KrF laser (λ=249 nm) and an ArF laser (λ=193 nm)], and the improvements in performance of the XeF laser were compared. The XeF laser beam profiles were measured by an intensified CCD (ICCD) camera with temporal resolution of 10 ns. Striated XeF laser profiles were obtained with 249 nm laser preionization, whereas there was no striation in the profiles for 193 nm laser preionization. These striations originated from discharge in the XeF laser induced by laser preionization. The influence of excited rare-gas atoms on the discharge instability was examined. 相似文献
6.
V. Kudriašov E. Gaižauskas V. Sirutkaitis 《Applied Physics A: Materials Science & Processing》2008,93(2):571-576
We present a study of the refractive index modifications spontaneously induced by infrared femtosecond filaments propagating
in the bulk of transparent solids. It was found that extended modified refractive index channels up to several mm in length
can be formed under loose focusing conditions in fused silica. The observed birefringence zone at the beginning of these channels
is attributed to the anisotropic stress induced via nonlinear losses in the high intensity region of the filament. 相似文献
7.
G. Cléon T. Amodeo A. Faccinetto P. Desgroux 《Applied physics. B, Lasers and optics》2011,104(2):297-305
In this work, the two-excitation wavelength laser induced incandescence (LII) method has been applied in a low-pressure premixed
methane/oxygen/nitrogen flame (equivalence ratio 2.32) to determine the variation of the ratio of the soot absorption functions
at 532 nm and 1064 nm E(m,532 nm)/E(m,1064 nm) along the flame. This method relies on the comparison of LII signals measured upon two different excitation wavelengths
(here 532 nm and 1064 nm) and with laser fluences selected in such a way that the soot particles are equally laser-heated.
The comparison of the laser fluences at 532 nm and 1064 nm leads to an easy determination of E(m,532 nm)/E(m,1064 nm). The reliability of the method is demonstrated for the first time in a low pressure flame in which the soot nucleation
zone can be spatially resolved and which contains soot particles acting differently with the laser fluence according to their
residence time in the flame. The method is then applied to determine the profile of E(m,532 nm)/E(m,1064 nm) along the flame. A very important decrease of this ratio is observed in the region of nascent soot, while the ratio
remains constant at high distance above the burner. Implication on temperature determination from spectrally resolved measurement
of flame emission is studied. 相似文献
8.
Lingling Ran Zhongyi Guo Shiliang Qu 《Applied Physics A: Materials Science & Processing》2010,100(2):517-521
Self-organized periodic surface structures on ZnO have been observed after multiple linearly polarized femtosecond laser pulse
irradiation. The observed self-organized structures are attributed to the second harmonics in the sample surface excited by
the incident laser. The grating orientation could be adjusted by the laser polarization direction. We also find that fluences
play an important role in the formation of self-organized nanostructures. 相似文献
9.
Dominik Maxein Stephan Kratz Peter Reckenthaeler Johanna Bückers Daniel Haertle Theo Woike Karsten Buse 《Applied physics. B, Lasers and optics》2008,92(4):543-547
Strong light-induced absorption has been observed in lithium niobate crystals doped with magnesium after application of femtosecond
illumination. In this material there are no Nb-on-Li-site defects and hence no antisite polarons occur, but small free polarons
close to the conduction band can be generated. The light-induced absorption observed is attributed to these polarons. For
LiNbO3:Mg, their decay times are about two orders of magnitude smaller than those of the Nb-on-Li-site polarons in undoped material.
The results are relevant for a better understanding of the suppression of the so-called optical damage in these crystals and
for their use in femtosecond applications. 相似文献
10.
Solid-state reactions, induced by ion-beam mixing (IBM)
and thermal annealing, in Ni/Si multilayered films (MLF) with an
overall stoichiometry of Ni2Si, NiSi and NiSi2, while
keeping the nominal thickness of Ni sublayer constant (3.0 nm),
were studied by using spectroscopic ellipsometry as well as X-ray
diffraction (XRD). The mixing was performed with Ar+ ions of
an energy of 80 keV and a dose of 1.5×
1016 Ar+/cm2. Unlike the results of our previous
study on Fe/Si MLF [Y.V. Kudryavtsev et al., Phys. Rev. B
65, 104417 (2002)], it was shown that an amorphous phase of
NiSi in the B20 phase was formed during deposition independent
of the overall stoichiometry of MLF, i.e., the nominal
thickness of Si sublayer. IBM leads to some structural changes in
the Ni/Si MLF, which cannot be detected by XRD but are confidently
recognized by optical tools. A thermal annealing at 673 K of the
Ni/Si MLF with an overall stoichiometry of NiSi and NiSi2 causes formation of the -NiSi phase. The first trace of
NiSi2 phase on the background of the -NiSi phase was
detected by XRD after an annealing at 1073 K, while, according to
the optical results, NiSi2 turned out to be the dominant phase
for the annealed Ni/Si MLF with an overall stoichiometry of NiSi2. 相似文献
11.
P. Haro-González I. R. Martín S. González-Pérez L. L. Martin F. Lahoz D. Puerto J. Solís 《Applied Physics A: Materials Science & Processing》2010,98(4):879-884
Localized modification of the optical properties of erbium doped strontium barium niobate (SBN) glass has been performed using
femtosecond laser irradiation. The samples, with composition SrO–BaO–Nb2O5–B2O5 and doped with 5%mol of Er3+, were fabricated using a melt-quenching method. The samples were irradiated with different number of pulses per spot (1–50
pulses) at two different laser fluences (2.6 and 5.6 J/cm2) by using an fs laser amplifier operating at 800 nm and generating pulses with a duration of 120 fs.
Micro-luminescent microscopy, using an Ar+ laser as excitation source, has been used to analyze the modifications of the luminescent properties of the sample upon fs
laser exposure. The emissions of the Er3+: 4I11/2→4I15/2 and 4I13/2→4I15/2 transitions allow appreciating the structural modifications caused by femtosecond laser exposure. The lifetimes of the levels
involved in these transitions were measured inside and outside the laser irradiated region. These measurements have been compared
with those obtained in bulk glass ceramic sample, which is obtained from the glass precursor by a thermal treatment in order
to estimate the optimal conditions to produce nanocrystals in a localized region by ultrafast laser irradiation. 相似文献
12.
We report on a new physical aspect of random lasing, an extremely selective modal oscillation by using a two-dimensional calculation
model. The developed model consists of two theoretical subsystems, two-dimensional scattering model for describing multiple
scattering process and rate equation model for describing lasing process. Using this model, we show how emission spectrum
behaves as the scattering state of photons inside the system changes. It is shown that specific and strong modal oscillation
takes place in a closed loop path of emitted photons, efficiently supported by the background multiple scattering. With the
increase of multiple scattering events around the closed loop path, the system starts to oscillate with an extremely strong
mode without any ASE (amplified spontaneous emission) noise. 相似文献
13.
Premixed laminar flat ethylene flames were investigated for nascent nanoparticles through photoionization mass spectrometry
(PIMS). Using an atmospheric McKenna burner and ethylene air flames coupled to an atmospheric sampling system, within a relatively
narrow C/O range two modes of these particles were found, which can be clearly distinguished with regard to their temperature
dependence, their reactivity, and their ionization behaviour. Behind a diesel engine the same particles were observed. 相似文献
14.
Huiying Lao Haisheng Zhu Xianfeng Chen 《Applied Physics A: Materials Science & Processing》2010,101(2):313-317
Fabricating domain reversal directly induced by femtosecond laser is a novel and promising method to induce micron-period
or even submicron-period inverted domain structure for it averts the domain spreading and mergence which is hard to avoid
by traditional electric-field poling method. In this paper, the domain reversal process in lithium niobate crystal by irradiation
of femtosecond pulses whose spatial and temporal distributions are taken into consideration is numerically simulated in the
framework of Fahy’s model. The simulation results manifest the domain inversion window theory and predict the threshold reversal
fluence. The experiment to form domain reversal via direct illumination with femtosecond laser in Y-cut lithium niobate samples was conducted at room temperature. The multi-ring-like structures on the processed samples tally
with the inversion window theory and the calculated threshold reversal fluence is well within the scope obtained by simulation,
which serves as a corroborative evidence to prove the domain reversals can be formed by direct irradiation with femtosecond
laser in lithium niobate. 相似文献
15.
D. Madi P. Prathap A. Focsa A. Slaoui B. Birouk 《Applied Physics A: Materials Science & Processing》2010,99(4):729-734
This work reports the investigations on the effects of the hydrogenation process of thin film polycrystalline n+pp+ mesa silicon cells using MW-ECR plasma in a conventional PECVD system. Different operating parameters such as MW-ECR power,
annealing temperature and the doping level of the emitter region were varied. The n+-type emitter regions were obtained by phosphorus diffusion in a conventional furnace using an oxide doping source containing
phosphorus (P507 or P509 solutions, from Filmtronics Inc.). The MW hydrogenation was carried out at a sample temperature of
400°C for 60 min. Both types of emitters formed from P507 and P509 showed V
oc of 155 mV and 206 mV, which increased linearly to 305 mV and 331 mV, respectively, after hydrogenation when the MW power
varied from 200 to 650 W. However, the sheet resistances of the n+ emitter region showed a slight increase depending upon hydrogenation power because of its etching. In a further study, hydrogenated
samples were annealed in neutral or forming gas (FG) and we observed interesting results on V
oc in the presence of FG. The FG annealing temperature study revealed a strong dependence of V
oc on MW power, which affected the etching level of emitter and emitter dopant concentration, which controls the diffusion of
hydrogen ions during post-hydrogenation step. The results were explained in detail by combining the effects of MW power and
dopant level of the emitter. 相似文献
16.
The transient microbending loss and refractive index changes in a double-coated optical fiber subjected to thermal loading
with stress-dependent interlayer thermal contact resistance is investigated. The effects of interlayer thermal resistance
on the transient microbending loss and refractive index changes of the optical fiber are analyzed and discussed. The results
show that the stress-dependent interlayer thermal contact resistance will increase the lateral pressure induced by the transient
thermal loading in the double-coated optical fiber and, thus, the microbending loss. Similarly, the interlayer thermal contact
resistance will increase the transient thermal loading induced refractive index changes in the beginning of loading. 相似文献
17.
Woei-Shyan Lee Tao-Hsing Chen Chi-Feng Lin Jyun-Ming Chen 《Applied Physics A: Materials Science & Processing》2010,100(4):1089-1096
Thin Ni/Si films are prepared by depositing a Ni layer with a thickness of 100 nm on a Si (100) substrate. The as-deposited
thin-film specimens are indented to a maximum depth of 500 nm using a nanoindentation technique and are then annealed at temperatures
of 200°C, 300°C, 500°C and 800°C for 2 min. The microstructural changes and phases induced in the various specimens are observed
using transmission electron microscopy (TEM) and micro-Raman scattering spectroscopy (RSS). Based on the load-displacement
data obtained in the nanoindentation tests, the hardness and Young’s modulus of the as-deposited specimens are found to be
13 GPa and 177 GPa, respectively. The microstructural observations reveal that the nanoindentation process prompts the transformation
of the indentation-affected zone of the silicon substrate from a diamond cubic structure to a mixed structure comprising amorphous
phase and metastable Si III and Si XII phases. Following annealing at temperatures of 200∼500°C, the indented zone contains
either a mixture of amorphous phase and Si III and Si XII phases, or Si III and Si XII phases only, depending on the annealing
temperature. In addition, the annealing process prompts the formation of nickel silicide phases at the Ni/Si interface or
within the indentation zone. The composition of these phases depends on the annealing temperature. Specifically, Ni2Si is formed at a temperature of 200°C, NiSi is formed at a temperature of 300°C and 500°C, and NiSi2 is formed at 800°C. 相似文献
18.
Yu Qian Ye Jian Qi Shen Yi Jin 《Applied Physics A: Materials Science & Processing》2008,93(2):505-509
The band structures and equifrequency contours of one-dimensional photonic crystals (PCs), which consist of an electromagnetically
induced transparency (EIT) medium and a common dielectric medium, can be dramatically changed by tuning the coupling field
intensity (or coupling Rabi frequency, CRF) of the EIT medium. It is found that for a probe light at a fixed frequency, either
positive or negative refraction in the EIT PC can be realized with a proper CRF. The behavior of a Gaussian beam (probe light)
obliquely incident on such an EIT PC slab is simulated numerically. The probe light beam transmitted from the slab can be
shifted transversely in a large range, and negative refraction enhances this effect. The present scenario can be applied in
some areas such as quantum optical and photonic device designs. 相似文献
19.
Sukanta Dutta Ashok Goyal Mamta 《The European Physical Journal C - Particles and Fields》2009,63(2):305-315
We study the one-loop new physics effects to the CP even triple neutral gauge boson vertices γ
⋆
γ
Z, γ
⋆
Z
Z, Z
⋆
Z
γ and Z
⋆
ZZ in the context of Little Higgs models. We compute the contribution of the additional fermions in Little Higgs models in the
framework of direct product groups where [SU(2)×U(1)]2 gauge symmetry is embedded in SU(5) global symmetry and also in the framework of the simple group where SU(N)×U(1) gauge symmetry breaks down to SU(2)
L
×U(1). We calculate the contribution of the fermions to these couplings when T parity is invoked. In addition, we re-examine the MSSM contribution at the chosen point of SPS1a′ and compare with the SM
and Little Higgs models. 相似文献
20.
M. Miyabe M. Oba H. Iimura K. Akaoka Y. Maruyama I. Wakaida 《Applied Physics A: Materials Science & Processing》2010,101(1):65-70
A cerium oxide sample was ablated by 2nd harmonic radiation of Nd:YAG laser at a power density of 0.1 GW/cm2. Time evolution of the ablation plume was investigated by laser absorption time-of-flight (TOF) measurement. It was found
that the ablated ionic plume in vacuum consisted of two components having different velocities whereas the ablated neutral
atoms had mainly a single component. The flow velocity perpendicular to the sample surface in vacuum was determined to be
3.5 km/s for neutral atoms, and 4.7 km/s and 9.3 km/s for singly charged ions. From the detailed plume evolution in ambient
atmosphere with several pressures we obtained some experimental conditions suitable for isotope analysis of atomic cerium. 相似文献