Research on design of a quasi-monoenergetic neutron beamline in the range of 30 ∼ 50 MeV

Energy loss of protons in SrTiO3 studied by medium energy ion scattering

The energy loss of keV protons, in thin films of C, Al and Ag is determined by a method in which the strong energy dependence of the cross section for X-ray excitation by protons, in a material, on which the films are evaporated, is used as an indicator of the proton energy.

Differences in the energy loss of protons and positive muons in solids

Energy loss of channeled protons in Al single crystal

The Fudan nuclear microprobe set-up and performance

Titanium oxide films are promising as a blood-contacting biomedical material. In this paper, titanium oxide films are deposited on a Si (1 0 0) substrate by high-power pulsed magnetron sputtering (HPPMS) at different oxygen flow rates. The microstructure and surface morphology are investigated for a variety of oxygen flow rates mixed with argon gas. The blood compatibility of the films is evaluated using a platelet adhesion experiment, and the quantity and morphology of the adhered platelets are investigated through optical microscopy. The oxygen flow rate is varied from 2 to 10 sccm with a fixed argon flow rate of 60 sccm. The composition of the deposited films was TiO and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm Ti}_{2}{\rm O}$</tex></formula> mixtures at an oxygen flow rate of 2 sccm. An anatase and rutile mixed phase is found at an oxygen flow rate of 4 sccm. The titanium oxide film is in the rutile phase with an increasing oxygen flow rate up to 6 sccm or higher. This suggests that the rutile-structured titanium oxide films could be synthesized by HPPMS without heating the substrate. The titanium oxide films with a rutile structure had a very smooth surface with a minimum surface roughness of 0.3 nm. The result of a platelet adhesion experiment indicates that the rutile phase titanium oxide film showed better blood compatibility. From this point of view, the films synthesized by HPPMS are promising to be as biomaterials showing excellent corrosion resistance and a smoothed surface.

The parameters affecting the production of11C-methane, in situ, in small volume, high-pressure gas targets include target chamber size and material. The results are based on experiments that varied the target gas composition, the target material and geometry. Methane production yields were typically 65% of the yields of11CO2in the same target chamber.

The construction of the National Ignition Facility (NIF) building and laser beampaths at the Lawrence Livermore National Laboratory has been completed. This 8-year design/construction effort has successfully erected a 450,000 sq ft building and filled its interior with a complex of large-scale optical benches. These benches support all of the largeaperture optic elements of the NIF and the environmentally controlled enclosures that protect each of the 192 laser beamlines as they propagate from the injection laser system, through large aperture amplification stages, and into the target chamber. Even though this facility is very large, nearly 200 m long, 100 m wide, and 30 m tall, stringent mechanical performance requirements have been achieved throughout including temperature control <0.3&deg;C, laserbeam pointing stability on target <50 &mu;rms, and level 100 surface cleanliness on internal components. This presentation will provide an historical perspective explaining the basis of the design, technical details describing the techniques of construction and a chronological progression of the construction activities from ground breaking to beampath completion.

For obtaining radiation less damageable laser mirrors, a preliminary optimization of film fabrication suitable for the analysis of laser damage mechanism has been done as the first step. Here, the optimization requires not only the stable fabrication process but also the ideal film structure i.e., the amorphous and smooth film structure simultaneously, eliminating latently unwanted secondary effects such as light scattering during laser damage test. For this purpose, we adopted the ion assisted deposition method and modified the deposition conditions for titanium and tantalum oxide films, both of which compose typical high index layers, and where SiO2 layers are also chosen as low index layers because of their amorphous and smooth nature, in alternative multilayer laser mirrors. Surface and cross sectional film structures and film crystallinity are compared and characterized, using a high resolution SEM and a x-ray diffractometer, respectively. The fabrication process and the film structures obtained even by IAD method for tantalum pentaoxide lack stability similar to those films by a conventional EB method. The fabrication process for titanium oxide films are stable even by a conventional EB method, but it produces the columnar film morphology and rough film surface and layer boundary simultaneously. Therefore, further optimization of titanium films, has been done by IAD method to improve the film morphology, introducing new fabrication parameters such as the determination of the best starting materials among various titanium oxides, adopting the new mixed gases of Ar and oxygen, suitable input power for ion gun, and arrival ratio of the ionized vapor ions. Then the structure of titanium oxides, adopting the new mixed gases of Ar and oxygen, suitable input power for ion gun, and arrival ratio of the ionized vapor ions. Then the structure of titanium oxide films deposition conditions of the ratios of oxygen and argon gases from 1:1 to 1:2 and ion power of 500 to 750 V during the titanium oxide deposition at the substrate temperature of 100 to 150 degrees C. Otherwise, the conventional EB and IAD methods with)2 gas only produce the columnar film structures and rougher boundaries than those by IAD with the mixed Ar + O2 gases. Related crystallinity and optical properties, such as refractive index, absorption, and index inhomogeneity, are also reported.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Various types of ionizing radiation can be produced by petawatt lasers including high energy x-rays, neutrons, and gamma radiation. The radiation production depends greatly on the target materials being used. The ionizing radiation production was estimated by calculation based on the information available during the facility design. The petawatt laser system has an output energy of 640 joules and pulse duration of 400 femtosecond. Prompt radiation, such as x-ray and neutrons, are instantaneous and cease when the laser beam is terminated; however, some materials will become radioactive through neutron activation and will emit radiation after termination of the laser beam. The amount of induced radioactivity by neutron activation depends on many factors which will be discussed. Ionizing radiation exposure to researchers, workers, or the general public depends on a number of factors, such as: emitted radiation types, radioactive half-lives, presence of shielding material, general working environment and occupancy factors, etc. The potential radiation hazards may be minimized by evaluating the induced radioactivity in materials and avoiding materials that produce long-lived radioisotopes and radiation that are difficult to shield.Instrument component materials for this laser facility are considered based on evaluation of then neutron activation potential. Radioisotope production in an aluminum alloy 6061 and steel alloy 1040 target chamber were determined. A deuterium (D) and tritium (T) mixture for the target is assumed and associated with 14.1 MeV neutrons produced from the D-T fusion reaction. The atom populations, induced radioactivity from neutron activation, and gamma radiation exposures were calculated. The results of this evaluation are considered in the selection of target chamber structural material. In this case, steel alloy 1040 presented the least radiological hazard to workers.Various types of ionizing radiation can be produced by petawatt lasers including high energy x-rays, neutrons, and gamma radiation. The radiation production depends greatly on the target materials being used. The ionizing radiation production was estimated by calculation based on the information available during the facility design. The petawatt laser system has an output energy of 640 joules and pulse duration of 400 femtosecond. Prompt radiation, such as x-ray and neutrons, are instantaneous and cease when the laser beam is terminated; however, some materials will become radioactive through neutron activation and will emit radiation after termination of the laser beam. The amount of induced radioactivity by neutron activation depends on many factors which will be discussed. Ionizing radiation exposure to researchers, workers, or the general public depends on a number of factors, such as: emitted radiation types, radioactive half-lives, presence of shielding material, general working environment and occu...

특정 광 파장 영역대역에서 광 반사율을 갖는 다층 박막을 DC펄스 스퍼터링 공정으로 제작하기 위하여 공정변수가 다층 박막의 광학 특성에 미치는 영향이 연구되었다. 다층 박막 필름을 제작하기위한 시뮬레이션이 이루어졌으며, DC펄스 스퍼터링 공정을 이용한 저 굴절률의 <TEX>$SiO_2$</TEX>와 고 굴절률의 <TEX>$TiO_2$</TEX> 박막의 광학 특성에 미치는 공정 변수 파라미터가 연구되었다. DC펄스 스퍼터링 파워 2kW, 아르곤 가스 200sccm(standard cubic centimeter per minute)기준조건에서 산소가스 비율 12% 범위에서 제작한 <TEX>$SiO_2$</TEX>박막은 굴절률 1.46이었고 산소가스 1% 비율에서 제작한 <TEX>$TiO_2$</TEX>박막은 굴절률 2.27이었다. 이들 박막으로 구성된 고 굴절률 박막/저 굴절률 박막/고 굴절률 박막의 3층 다층 박막 구조의 광학설계 시뮬레이션 결과와 측정된 광 반사율 특성결과는 파장 대역에 걸쳐 유사한 경향이 있는 것으로 측정되었다. 근적외선 780nm에서 1200nm파장 대역 영역에서 광 반사율 45%이상의 성능을 갖는 다층 박막 필름을 제작할 수 있었고 근적외선 차단 기능 박막으로 사용될 것으로 기대된다. The process parameters of DC pulsed sputtering to produce a multi-layer thin film with light reflectance at a specific wavelength region were studied. The optical simulation of multi-layer thin films of the silicon dioxide (<TEX>$SiO_2$</TEX>) films with a low refractive index and the titanium dioxide (<TEX>$TiO_2$</TEX>) films with a high refractive index was done. Under a DC pulsed sputtering power of 2kW and 200 sccm(standard cubic centimeter per minute) argon gas, the silicon dioxide films with a refractive index of 1.46 in the range of oxygen gas ratios of 12% and a titanium dioxide film with a refractive index of 2.27 in the range of oxygen gas ratios of 1% were produced. The multi-layer structure of high refractive index/low refractive index/high refractive index was designed and fabricated. The characteristics of the fabricated multi-layer thin film structure showed a reflectance of more than 45% in the range, 780 to 1200nm. This multi-layer structure is expected to be used to block the near infrared wavelength light.

Energy loss of protons in rare earth oxides and reduced transition probabilities for 2 +→0 + transitions in even rotational nuclei

Authors

Recent experimental determinations [J. E. Vald\'es, G. Mart\'{\i}nez-Tamayo, G. H. Lantschner, J. C. Eckardt, and N. R. Arista, Nucl. Instrum. Methods B 73, 313 (1993)] of the energy loss of low-energy protons in Ag and Au show a departure from the velocity proportionality predicted by theory, while data for other metallic elements, such as Al, Sb, and Bi, are in agreement with this dependence. In this work we present measurements in Cu foils which show a similar behavior to that in Ag and Au. We give an interpretation of the differences between these cases due to the existence of small binding energies for the d electrons in Cu, Ag, and Au. We present a model based on transport cross section and density-functional theory, which introduces threshold effects in the calculation of the transport cross section of nonfree electrons, and explains the deviations from the velocity-proportional dependence.

The methods due to Bloch and Pines have been used to calculate the energy loss of channeled protons. The contribution from the various atomic shells to the stopping power is assumed to be additive. The collective effects in a solid plasma produced by the valence electrons are calculated disregarding the band structure. The nonuniform distribution of valence electrons across the channel is taken into account. In contrast to Robinson and Dettmann, a detailed summation is performed over the spectrum of oscillator strengths when calculating the energy loss due to inner-shell electrons. It has been found that, contrary to the common belief, the energy loss due to inner-shell electrons is considerable even for wide channels, whereas the energy loss due to the valence electrons turns out to be lower. The numerical calculations for silicon and germanium have yielded results that agree well with experiment. The energy loss at relativistic velocities has also been calculated. The obtained results may be used for quantitative predictions of energy loss in channeling experiments.