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1.
We present a simple model that uses a novel photon scattering approach to predict the depth profile response obtained when confocal Raman spectroscopy is applied both to silicon and to a number of related polymeric materials of varying optical clarity. This paper first provides an overview of the models proposed to date to demonstrate the evolution in understanding of the confocal Raman response of semi‐transparent materials, based upon geometrical optics. A new model is then described that is based upon the twin notions of a permanent extended Raman illuminated volume and the degree of extinction of the incident and Raman scattered photons from the whole of the illuminated volume as it is gradually moved further into, or defocused above, the sample. The model's predictions are compared with empirical data from previous studies of a range of semi‐crystalline polymers with different scattering properties and, by means of contrast, with that of a silicon sample. We show that, despite its inherent simplicity, the physics this model utilizes is able successfully to predict the form of the depth profile for each material, something that has not been achieved by any model previously proposed, and that the parameters used in the model scale with independent physical measurements. Finally the model is used to account for the fact that useful Raman spectra can be obtained when the laser is focused as much as 40 µm above the sample surface. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
2.
To simulate the intense bunched beam transport, a computer
program LEADS-3D has been developed. The particle trajectories are
analysed with the Lie algebraic method. The third order
approximation of the trajectory solutions is made with space charge
forces off, and the second order approximation is made with space
charge forces on. The particle distribution in the 3D ellipsoid is
uniform or Gaussian. Most of the conventional beam optical elements
are incorporated in the code. The optimization procedures are
provided to fit the beam lines to satisfy the given optical
conditions. 相似文献
3.
A code LEADS based on the Lie algebraic analysis for the continuous beam dynamics with space charge effect in beam transport has been developed.The program is used for the simulations of axial-symmetric and unsymmetricalintense continuous beam in the channels including drift spaces.electrostatic lenses and DC electrostatic accelerating tubes.In order to get the accuracy required,all elements are divided into many small segments,and the electric field in the segments is regarded as uniform field,and the dividing points are treated as thin lenses.Iteration procedures are adopted in the program to obtain self-consistent solutions.The code can be used in the designs of low energy beam transport systems,electrostatic accelerators and ion implantation machines. 相似文献
4.
A code LEADS based on the Lie algebraic analysis for the continuous beam dynamics with space charge effect in beam transport has been developed. The program is used for the simulations of axial-symmetric and unsymmetrical intense continuous beam in the channels including drift spaces, electrostatic lenses and DC electrostatic accelerating tubes. In order to get the accuracy required, all elements are divided into many small segments, and the electric field in the segments is regarded as uniform field, and the dividing points are treated as thin lenses. Iteration procedures are adopted in the program to obtain self-consistent solutions. The code can be used in the designs of low energy beam transport systems, electrostatic accelerators and ion implantation machines. 相似文献
5.
We analyze the coherent transport of a single photon, which propagates in a one-dimensional coupled-resonator waveguide and is scattered by a controllable two-level system located inside one of the resonators of this waveguide. Our approach, which uses discrete coordinates, unifies low and high energy effective theories for single-photon scattering. We show that the controllable two-level system can behave as a quantum switch for the coherent transport of a single photon. This study may inspire new electro-optical single-photon quantum devices. We also suggest an experimental setup based on superconducting transmission line resonators and qubits. 相似文献
6.
Natasha Flyer Erik Lehto Sébastien Blaise Grady B. Wright Amik St-Cyr 《Journal of computational physics》2012,231(11):4078-4095
The current paper establishes the computational efficiency and accuracy of the RBF-FD method for large-scale geoscience modeling with comparisons to state-of-the-art methods as high-order discontinuous Galerkin and spherical harmonics, the latter using expansions with close to 300,000 bases. The test cases are demanding fluid flow problems on the sphere that exhibit numerical challenges, such as Gibbs phenomena, sharp gradients, and complex vortical dynamics with rapid energy transfer from large to small scales over short time periods. The computations were possible as well as very competitive due to the implementation of hyperviscosity on large RBF stencil sizes (corresponding roughly to 6th to 9th order methods) with up to O(105) nodes on the sphere. The RBF-FD method scaled as O(N) per time step, where N is the total number of nodes on the sphere. In Appendix A, guidelines are given on how to chose parameters when using RBF-FD to solve hyperbolic PDEs. 相似文献
7.
Atomic beam guide by a one-dimensional magneto-optical trap 总被引:1,自引:0,他引:1
An atomic beam has been collimated, compressed, and deflected simultaneously by an atomic beam guide based on an inclined
one-dimensional magneto-optical trap (1D-MOT). Isotope-selected rubidium atoms were extracted from the naturally-mixed thermal
atomic beam with this method. We could manipulate the transverse displacement of the deflected beam precisely by adjusting
the current in the copper rods to generate the quadrupole magnetic field. We could extract more than 50% of the incident atoms
as a deflection beam when we combined this deflection technique with the atomic deceleration using a broadband spectral light.
Received: 10 December 1998 / Published online: 24 June 1999 相似文献
8.
9.
P. Cren C.F. Roos A. Aclan J. Dalibard D. Guéry-Odelin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(1):107-116
We demonstrate experimentally the continuous and pulsed loading of a slow and cold atomic beam into a magnetic guide. The
slow beam is produced using a vapor loaded laser trap, which ensures two-dimensional magneto-optical trapping, as well as
cooling by a moving molasses along the third direction. It provides a continuous flux larger than 109 atoms/s with an adjustable mean velocity ranging from 0.3 to 3 m/s, and with longitudinal and transverse temperatures smaller
than 100 μK. Up to 3×108 atoms/s are injected into the magnetic guide and subsequently guided over a distance of 40 cm.
Received 19 February 2002 Published online 28 June 2002 相似文献
10.
Kyoung Won Jang Dong Hyun Cho Sang Hun Shin Wook Jae Yoo Jeong Ki Seo Bongsoo Lee Sin Kim Joo Hyun Moon Young-Ho Cho Byung Gi Park 《Optical Review》2009,16(3):383-386
Abstact A scintillating fiber-optic dosimeter has many advantages such as real-time readout, high-resolution measurement, water-equivalence
and no corrections for temperature, pressure and humidity. Organic scintillator which has water or tissue equivalent characteristics
is very important to measure absorbed dose, dose rate and dose distributions exactly without any corrections and due to its
small size, the sensitive volume enables accurate dose measurements in regions of high dose gradients with high spatial resolution.
In this study, a scintillating fiber-optic dosimeter with an organic scintillator is fabricated to measure high-energy photon
beam from a clinical linear accelerator. And we have measured linear responses of a fiber-optic dosimeter according to dose
rates and monitor units of a clinical linear accelerator. Also, a percent depth dose curve for 6MV photon beam with different
field sizes are obtained. 相似文献
11.
12.
13.
Vanaverbeke S Leroy O Shkerdin G 《The Journal of the Acoustical Society of America》2003,114(2):601-610
A theoretical study of the reflection of a two-dimensional Gaussian ultrasonic beam, incident at a Lamb angle of a plate containing a thin rectangular inclusion at an arbitrary position, is presented on the basis radiation mode theory. The inclusion is parallel to the plate surface and its thickness is assumed to be much smaller than the ultrasonic wavelength. It is shown that the amplitude and phase of the reflected beam profile can be used for accurate inclusion characterization. However, this only holds for certain internal positions of the inclusion and for material combinations that do not strongly perturb the excitation of Lamb waves in the plate. When these conditions are satisfied, it is possible to define the Lamb waves and the associated experimental conditions for which good estimates can be obtained of the position of the beginning point of the inclusion as well as of the length and the thickness of the inclusion. 相似文献
14.
采用无模激光器发射波长为330 nm的激光激发多色激光导星,需要考虑脉冲激光重频率、激光带宽、激光初始光斑直径以及大气透过率对回波光子数的影响.通过数值模拟,计算了高斯光束的脉冲激光和连续激光激发多色激光导星在实际大气中后向辐射330 nm和2207 nm波长的回波光子数.数值计算结果表明,在垂直发射和接收的情况下,当到达大气中间层的激光能量为1 W时,连续激光能够获得更多的回波光子数,并且回波光子数几乎无起伏.对于脉冲激光,提高脉冲激光重频率达到50 kHz以上时,多色激光导星330 nm的回波光子数随脉冲重频率的增加趋于有限值;当大气能见度小于5 km且大气相干长度为12.8 cm时,大约需要34 W以上的激光发射能量,才能获得满足使用自然星全倾斜探测的330 nm回波光子数.对于连续激光,相同情况下,大约需要20 W以上的激光发射能量. 相似文献
15.
A. D. Levin D. M. Gitman R. A. Castro 《The European Physical Journal C - Particles and Fields》2014,74(9):1-7
We show how the photon input parton distribution function (PDF) may be calculated with good accuracy and used in an extended DGLAP global parton analysis in which the photon is treated as an additional point-like parton. The uncertainty of the input photon PDF is relatively small, since the major part of the distribution (which is produced by the coherent emission of the photon from a proton that remains intact) is well known. We present the expected photon PDFs and compare the predictions with ZEUS data for isolated photon electroproduction at negative rapidities. 相似文献
16.
Yu. M. Golubev I. V. Sokolov M. I. Kolobov 《Journal of Experimental and Theoretical Physics》1997,84(5):864-874
Using the optical excitation of a high-Q cavity as an example, it is shown that when light is observed at the output of this
cavity, effective suppression of the photocurrent shot noise below the quantum limit is in general independent of the parameters
of the stationary state of the field oscillator (in particular, it is independent of the rms photon fluctuations) inside the
cavity and can occur not only at any allowed negative value but even at a positive value of the Mandel parameter. It was assumed
in solving the problem that the cavity is optically excited by superimposing the radiation of a sub-Poisson laser and a laser
with excess photon noise. A formal solution was obtained in terms of the kinetic equation for the density matrix of the actual
fields (inside the laser cavities and the empty cavity), which is derived here on the basis of the Heisenberg-Langevin quantum
equations, taking into account directed propagation of the field from the laser cavities inside the empty cavity. The resulting
kinetic equation can also be used to solve other physical problems, since it is applicable to optical systems that contain,
in principle, an arbitrary number of coupled cavities and interference mixers.
Zh. éksp. Teor. Fiz. 111, 1579–1600 (May 1997) 相似文献
17.
L. Mandel 《Physics letters. A》1984,103(9):416-418
It is shown explicitly that when a photon is incident on a beam splitter, one arm of which is followed by a light amplifier, the joint probability of photon detection in both arms is non-zero only because of spontaneous emission from the amplifier. The non-locality of quantum mechanics does not play a significant role in this situation. 相似文献
18.
An ion source based on successive photoionization of trapped ions is now possible using high-brightness X rays from a modern synchrotron storage ring. Calculations based on the design parameters for the National Synchrotron Light Source at Brookhaven indicate that degrees of ionization and beam intensities should be comparable to those achieved with existing EBIS, ECRIS, or recoil-ion sources. 相似文献
19.
The objective of this research is to evaluate the feasibility of the internal patterning in the light guide panel (LGP) by applying laser engraving. LGP fabricated by the internal patterning is proposed as it offers better efficiency than is provided by bottom surface patterning. The patterns fabricated by laser engraving system could improve efficiency by approximately 40%, requiring less energy consumption in average brightness and uniformity than required by bottom surface patterned devices. Internal scatters were fabricated by Q-switched 2nd harmonic Nd:YAG laser engraving system. The performance of the fabricated LGPs was measured and its results analyzed. Modification of the shape of the LGP patterns from the simple geometry has been investigated to control the uniformity. The proposed internal scatter embedded LGP with laser engraving could provide an alternative method to conventional bottom surface scatters type with optimized patterns and geometry. 相似文献
20.
Numerical simulations for sonochemistry are reviewed including single-bubble sonochemistry, influence of ultrasonic frequency and bubble size, acoustic field, and sonochemical synthesis of nanoparticles. The theoretical model of bubble dynamics including the effect of non-equilibrium chemical reactions inside a bubble has been validated from the study of single-bubble sonochemistry. By the numerical simulations, it has been clarified that there is an optimum bubble temperature for the production of oxidants inside an air bubble such as OH radicals and H2O2 because at higher temperature oxidants are strongly consumed inside a bubble by oxidizing nitrogen. Unsolved problems are also discussed. 相似文献