Simulation of nonlinear behavior in an electron cyclotron resonance plasma

1.IntroductionDuringthepastseveralyears,microwaveelectroncyclotronresonance(ECR)plasmasourceshavebeensuccessfullyusedinareasofmicroelectronicfabrica-tionsuchassurfacemodification,etchinganddepo-sitionofthinfilms[l,2].Intheseindustrialapplica-tions,theoperatingstabilityisofparticularconcern.ItiswellknownthatECRplasmasasadieledtricarehighlynonlinear,andthus,arepronetoinstabili-tiesthatcanmakehavocofmanufacturingprocesses.Theusualsolutiontothisproblemistocautiouslychoosesomeregionsofoperatingp…     

Mutual screening of blocks of resonance neutron absorber in a “tight” lattice

This paper deals with the evaluation of the effect of mutual screening of blocks and layers of resonance absorber which arises when the thickness of the moderator separating the absorber blocks is comparable with or less than the mean free path of neutrons in the moderator. In the calculations it is assumed that the blocks are small and that the absorption cross section is described by the Breit-Wigner formula.From the calculations carried out for a system of parallel plates it is possible to evaluate the accuracy of the results obtained in [1] and also to obtain an equation for a system which is nearly homogeneous. It is shown that the approximate substitution of an equivalent circular cell for the true cell in a lattice consisting of cylindrical blocks, which is usually justified, in the case of problems of the type considered leads to appreciable errors. In addition, a resonance-absorption formula is obtained in the case of an annular geometry of the absorber.In conclusion the author thanks G. I. Marchuk and T. Kh. Sedel'nikov for useful discussions and comments.     

Neural Network for mass reconstruction of resonance particle with missing energy

Neural Network can be designed to reconstruct the mass of resonance particle with large missing energy.Taking the Higgs particle search through decaying channel H^0→T^ T^-→eμx and H^0→W^ W^-(ZZ)→llvv at LHC collider(√s=16TeV)as examples,neural network correctly reconstructs its mass with right peak position and better width than conventional method.The network also possesses the capability of suppressing background events.This kind of neural network can be widely used in new particle searc and precise mass measurent of resonance particle.     

Extension of rational approximation method to p-wave collision amplitudes in Reich–Moore resonance formalism

Rational approximation method developed to calculate s-wave collision matrix for non-fissile nuclides in Reich–Moore (RM) resonance formalism is extended to the p-wave part of the RM collision amplitudes.     

Correlation of Ⅲ/Ⅴ semiconductor etch results with physical parameters of high-density reactive plasmas excited by electron cyclotron resonance

Reactive ion etching is the interaction of reactive plasmas with surfaces. To obtain a detailed understanding of this process, significant properties of reactive composite low-pressure plasmas driven by electron cyclotron resonance(ECR) were investigated and compared with the radial uniformity of the etch rate. The determination of the electronic properties of chlorine-and hydrogen-containing plasmas enabled the understanding of the pressure-dependent behavior of the plasma density and provided better insights into the electronic parameters of reactive etch gases. From the electrical evaluation of I(V) characteristics obtained using a Langmuir probe,plasmas of different compositions were investigated. The standard method of Druyvesteyn to derive the electron energy distribution functions by the second derivative of the I(V)characteristics was replaced by a mathematical model which has been evolved to be more robust against noise, mainly, because the first derivative of the I(V) characteristics is used. Special attention was given to the power of the energy dependence in the exponent. In particular, for plasmas that are generated by ECR with EM modes, the existence of Maxwellian distribution functions is not to be taken as a self-evident fact, but the bi-Maxwellian distribution was proven for Ar-and Kr-stabilized plasmas. In addition to the electron temperature, the global uniform discharge model has been shown to be useful for calculating the neutral gas temperature. To what extent the invasive method of using a Langmuir probe could be replaced with the noninvasive optical method of emission spectroscopy, particularly actinometry, was investigated,and the resulting data exhibited the same relative behavior as the Langmuir data. The correlation with etchrate data reveals the large chemical part of the removal process—most striking when the data is compared with etching in pure argon. Although the relative amount of the radial variation of plasma density and etch rate is approximately ?5%, the etch rate shows a slightly concave shape in contrast to the plasma density.     

Thermal neutron cross-section and resonance integral of the Mo(n,γ)Mo reaction

We measured the thermal neutron cross-section and the resonance integral of the ⁹⁸Mo(n,γ)⁹⁹ Mo reaction by the activation method using a ¹⁹⁷Au(n,γ)¹⁹⁸ Au monitor reaction as a single comparator. The high-purity natural Mo and Au metallic foils with and without a cadmium shield case of 0.5 mm thickness were irradiated in a neutron field of the Pohang neutron facility. The induced activities in the activated foils were measured with a calibrated p-type high-purity Ge detector. The necessary correction factors for the γ-ray attenuation (F_g), the thermal neutron self-shielding (G_th) and the resonance neutron self-shielding (G_epi) effects, and the epithermal neutron spectrum shape factor (α) were taken into account. In addition, for the ⁹⁹Mo activity measurements, the correction for true coincidence summing effects was also taken into account. The thermal neutron cross-section for the ⁹⁸Mo(n,γ)⁹⁹Mo reaction has been determined to be 0.136 ± 0.007 barn, relative to the reference value of 98.65 ± 0.09 barn for the ¹⁹⁷Au(n,γ)¹⁹⁸ Au reaction. The present result is, in general, in good agreement with most of the experimental data and the recently evaluated values of ENDF/B-VII.0, JENDL-3.3, and JEF-2.2 by 5.1% (1σ). By assuming the cadmium cut-off energy of 0.55 eV, the resonance integral for the ⁹⁸Mo(n,γ)⁹⁹Mo reaction is 7.02 ± 0.62 barn, which is determined relative to the reference values of 1550 ± 28 barn for the ¹⁹⁷Au(n,γ)¹⁹⁸Au reaction. The present resonance integral value is in general good agreement with the previously reported data by 8.8% (1σ).     

Production of intense highly charged ion beams by IMP 14.5GHz electron cyclotron resonance ion source

A new 14.5GHz Electron Cyclotron Resonance(ECR) ion source has been constructed over the last two years.The source was designed and tested by making use of the latest results from ECR ion source development ,such as high mirror magnetic filed,large plasma volume,and biased probe.140μA of O^7 ,185μA of Ar^11 and 50 μA of Xe^26 could be produced with a RF power of 800W, The intense beams of highly charged metallic ions are produced by means of the method of a metal evaporation oven and volatile compound throuth axial access,The test results are 130μA of Ca^11 ,70μA of Ca^12 and 65 μA of Fe^10 ,The ion source has been put into operation for the cyclotron at the Institute of Moderm Physics(IMP).     

Effect of parallel resonance on the electron energy distribution function in a 60 MHz capacitively coupled plasma

In general, as the radio frequency(RF) power increases in a capacitively coupled plasma(CCP), the power transfer efficiency decreases because the resistance of the CCP decreases. In this work, a parallel resonance circuit is applied to improve the power transfer efficiency at high RF power, and the effect of the parallel resonance on the electron energy distribution function(EEDF) is investigated in a 60 MHz CCP. The CCP consists of a power feed line, the electrodes, and plasma. The reactance of...     

Design and experimental results of a 28 GHz,400 kW gyrotron for electron cyclotron resonance heating

A high-power 28 GHz gyrotron has been successfully developed at the Institute of Applied Electronics, China Academy of Engineering Physics. This gyrotron was designed for electron cyclotron resonance heating(ECRH) in the spherical tokamak XL-50. A diode magnetron injection gun was designed to produce the required gyrating electron beam. The gyrotron operates in the TE8,3mode in a cylindrical open cavity. An internal quasi-optical mode converter was designed to convert the operating mode into a f...     

Depth profiling of Mg by 2010 keV resonance of Mg(p,p′γ)Mg nuclear reaction

Studies on the characteristics of 2010 keV resonance in ²⁴Mg(p,p′γ)²⁴Mg nuclear reaction for depth profiling Mg in thin films are reported. The resonance reaction, based on the detection of characteristic 1368 keV γ-rays, enables interference free measurement of Mg down to 2 × 10²⁰ atoms/cm³ and has a probing depth of about 20 μm. The width of the resonance extracted from excitation curves for thick (>180 nm) thermally grown elemental Mg films, by SPACES is about 350 ± 50 eV. The reaction has been used to depth profile Mg in a Mg/Ti/Mg/Si film which provides interesting information on interfacial mixing involving Ti layer and the underlying Mg layer.     

Methodology and application of the nuclear resonance reaction 16O(α, α)16O for the profiling of titanium oxide

A method is presented for the application of the ¹⁶O(α,α)¹⁶O resonance at 3.045 MeV to the depth profiling of oxide films. The resonance yield is translated into oxygen to metal stoichiometry as a function of the depth probed. The method is applied to anodic titanium oxide films grown in the absence and presence of tungsten anions. The oxygen depth profile is then utilized to obtain the profile of the dopants (W) incorporated in the oxide. A depth resolution of 6 μg/cm is achieved. The incorporation of tungsten anions of the order of 2 at.%, evaluated from the RBS yields, precludes the establishment of a constant oxygen to metal stoichiometry in the doped film. The tungsten atomic fractions have an estimated error of 5%.     

Measurement of the average number νeff of neutrons emitted per single capture event for samples of Pu239 with impurities of the isotope Pu240 and the effective resonance capture integral of Pu240

In this article we present the results of measurement of _eff in Fermi spectra with lower bounds of 0.15 ev (gadolinium filter) and 0.4 ev (cadmium filter) for samples of Pu²³⁹ with various concentrations of impurities of the isotope Pu²⁴⁰ (0% 1.6%, 2.5%, 6.5%, 16%) and the effective resonance absorption integral of Pu²⁴⁰.The present work was carried out on the suggestion of academician I. V. Kurchatov. The authors take this opportunity again to express their gratitude to him for his constant interest in the work.We also express our indebtedness to P. E. Spivak for directing ther work.     

Electron paramagnetic resonance study of proton implantation induced defects in monocrystalline 4H– and 6H–SiC

Ion implantation is frequently employed in SiC for doping, electrical isolation or in the SiC on isolator technology. The ion implantation process is accompanied by the formation of intrinsic defects, which introduce deep electron and hole traps. They are believed to be mainly multivacancy complexes but the exact microscopic nature of these defects and their distribution versus the ion penetration depth is not well established. We have analyzed by electron paramagnetic resonance spectroscopy the defects introduced by high energy (MeV) proton implantation. In this study we extend the previous investigations on n-type SiC to the case of p-type Al doped bulk samples. Both silicon monovacancy and carbon vacancy related defects are observed. Their nature and introduction rate have been determined. The results obtained will be compared to the published electrical studies in order to correlate the vacancy defects with the known electron and hole traps.     

Effect of absorbed dose and storage length on electron paramagnetic resonance （EPR） signal strength in irradiated alfalfa seeds

1 Introduction Human salmonellosis associated with the con- sumption of alfalfa seed sprouts has been documented in several countries and people have applied several techniques to kill microorganisms in the alfalfa seeds[1]. Gamma irradiation can effectively kill the microorganisms in the seeds over a certain range of absorbed dose[2]. As a prerequisite, a suitable detection method for distinguishing whether or not a kind of food has been irradiated lies not only in whether some differences be…     

Oxygen depth profiling in Kr-implanted polycrystalline alpha titanium by means of O(α,α)O resonance scattering

The ¹⁶O(α,α)¹⁶O resonance scattering was applied to study the effects of ion implantation on the oxygen distribution in the near surface region of polycrystalline titanium implanted with 180 keV krypton ions at fluences, ranging between 1 × 10¹⁴ and 5 × 10¹⁵ Kr⁺/cm². Two sample sets were chosen: as-received polycrystalline titanium discs rolled and annealed in half-hard condition which had a thick oxygen layer and similar samples in which this surface layer was removed by polishing. An increase of the mean oxygen concentration observed in both unpolished and polished samples at low fluence suggests a knock-on implantation of surface oxygen atoms. At high fluence, an overall decrease in the mean oxygen concentration and mean oxygen depth suggests an out-diffusion of near-surface oxygen atoms.     

Thermal neutron cross-section and resonance integral of the W(n, γ)W reaction

We measured the thermal neutron cross-section and the resonance integral of the reaction ¹⁸⁶W(n, γ)¹⁸⁷W by the activation method using a ¹⁹⁷Au(n, γ)¹⁹⁸Au monitor reaction as single comparator. The high-purity natural W and Au metallic foils with and without a cadmium shield case of 0.5 mm thickness were irradiated in a neutron field of the Pohang neutron facility. The induced activities in the samples were measured by high-resolution γ-ray spectrometry with a calibrated p-type high-purity Ge detector. The necessary correction factors for γ-ray attenuation (F_g), thermal neutron self-shielding (G_th), and resonance neutron self-shielding (G_epi) effects, and the epithermal neutron spectrum shape factor (α) were taken into account. The thermal neutron cross-section for the ¹⁸⁶W(n, γ)¹⁸⁷W reaction has been determined to be 37.2 ± 2.1 barn, relative to the reference value of 98.65 ± 0.09 barn for the ¹⁹⁷Au(n, γ)¹⁹⁸Au reaction. The present result is, in general, in good agreement with most of the experimental data and the recently evaluated value of ENDF/B-VII.0 by 5.7%. By assuming the cadmium cut-off energy of 0.55 eV, the resonance integral obtained is 461 ± 39 barn, which is determined relative to the reference values of 1550 ± 28 barn for the ¹⁹⁷Au(n, γ)¹⁹⁸Au reaction. The present resonance integral value is in general good agreement with the recently measured values by 9%. The present result is lower than the evaluated ones by 10-13%.     

Picosecond time-resolved X-ray ferromagnetic resonance measurements at Shanghai synchrotron radiation facility

An experimental picosecond time-resolved X-ray ferromagnetic resonance(TR-XFMR) apparatus with a time resolution of 13 ps(RMS) or 31 ps(FWHM)was constructed and demonstrated in the 07U and 08U1A soft X-ray beamlines at the Shanghai Synchrotron Radiation Facility(SSRF) using pump-probe detection and X-ray magnetic circular dichroism(XMCD) spectroscopy. Element and time-resolved ferromagnetic resonance was excited by continuous microwave phase-locking of the bunch clock within the photon beam duri...