Search results for "accelerator"
showing 10 items of 1507 documents
"Table 1" of "The spin-dependent structure function g1(x) of the proton from polarized deep-inelastic muon scattering."
1998
The virtual photon proton asymmetries. Only statistical errors are given.
PERIPHERAL SURFACE DOSE FROM A LINEAR ACCELERATOR: RADIOCHROMIC FILM EXPERIMENTAL MEASUREMENTS OF FLATTENING FILTER FREE VERSUS FLATTENED BEAMS
2020
Abstract There is a growing interest in the use of flattening filter free (FFF) beams due to the shorter treatment times. The reduction of head scatter suggests a better radiation protection to radiotherapy patients, considering the expected decrease in peripheral surface dose (PSD). In this work, PSD of flattened (FF) and FFF-photon beams was compared. A radiochromic film calibration method to reduce energy dependence was used. PSD was measured at distances from 2 to 50 cm to the field border for different square field sizes, modifying relevant clinical parameters. Also, clinical breast and prostate stereotactic body radiotherapy (SBRT) plans were studied. For square beams, FFF PSD is lowe…
Mass Measurements with the CSS2 and CIME cyclotrons at GANIL
2005
Commune avec ACEN; This paper presents two original direct mass-measurement techniques developed at GANIL using the CSS2 and CIME cyclotrons as high-resolution mass spectrometers. The mass measurement with the CSS2 cyclotron is based on a time-of-flight method along the spiral trajectory of the ions inside the cyclotron. The atomic mass excesses of 68Se and 80Y recently measured with this technique are -53.958(246) MeV and -60.971(180) MeV, respectively. The new mass-measurement technique with the CIME cyclotron is based on the sweep of the acceleration radio-frequency of the cyclotron. Tests with stable beams have been performed in order to study the accuracy of this new mass-measurement m…
High-Precision Multiphoton Ionization of Accelerated Laser-Ablated Species
2018
We demonstrate that the pulsed-time structure and high-peak ion intensity provided by the laser-ablation process can be directly combined with the high resolution, high efficiency, and low background offered by collinear resonance ionization spectroscopy. This simple, versatile, and powerful method offers new and unique opportunities for high-precision studies of atomic and molecular structures, impacting fundamental and applied physics research. We show that even for ion beams possessing a relatively large energy spread, high-resolution hyperfine-structure measurements can be achieved by correcting the observed line shapes with the time-of-flight information of the resonantly ionized ions.…
On the coupling dynamics between thermally stressed beams and granular chains
2015
The in-situ measurement of thermal stress in slender beams, or long continuous welded rails, may prevent structural anomalies. With this aim, we investigated the coupling dynamics between a beam and the highly nonlinear solitary waves propagating along a straight granular chain in contact with the beam. We hypothesized that these waves can be used to measure the stress of thermally loaded structures, or to infer the neutral temperature, i.e., the temperature at which this stress is null. We studied numerically and experimentally the mechanical interaction of one and two straight chains of spherical particles in contact with a prismatic beam that is subjected to heat. The results show that c…
Ein kalorimeter für hochenergetische elektronenstrahlen
1968
Abstract Construction details and experimental data are given for a total absorption calorimeter used for electron beams of several hundred MeV and for beam power up to 15 kW. In order to obtain high precision, precautions were taken to obtain very high heat insulation, specially by using a temperature controlled radiation shield. The heat loss of the 700 kg copper block corresponds to less than 10 −3 °C/h. Due to design calculations and confirmed by preliminary comparison tests with other beam monitors we consider the absolute accuracy to be 1% or probably better.
High-Resolution Spectroscopy in Fast Atomic Beams
1977
Narrow optical resonances have been observed in fast beams of Na and Cs atoms, obtained from ion beams by charge-transfer collisions with Na, K, or Cs. Corresponding to the narrowing of the velocity distribution, occurring by acceleration, the Doppler width along the beam direction is considerably reduced [1, 2].
Shear strength of steel fiber reinforced concrete beams with stirrups
2006
The present paper proposes a semi-empirical analytical expression that is capable of determining the shear strength of reinforced concrete beams with longitudinal bars, in the presence of reinforcing fibers and transverse stirrups. The expression is based on an evaluation of the strength contribution of beam and arch actions and it makes it possible to take their interaction with the fibers into account. For the strength contribution of stirrups, the effective stress reached at beam failure was considered by introducing an effectiveness function. This function shows the share of beam action strength contribution on the global strength of the beam calculated including the effect of fibers. T…
Study of Gasdynamic Electron Cyclotron Resonance Plasma Vacuum Ultraviolet Emission to Optimize Negative Hydrogen Ion Production Efficiency
2019
Negative hydrogen ion sources are used as injectors into accelerators and drive the neutral beam heating in ITER. Certain processes in low-temperature hydrogen plasmas are accompanied by the emission of vacuum ultraviolet (VUV) emission. Studying the VUV radiation therefore provides volumetric rates of plasma-chemical processes and plasma parameters. In the past we have used gasdynamic ECR discharge for volumetric negative ion production and investigated the dependencies between the extracted H$^-$ current density and various ion source parameters. It was shown that it is possible to reach up to 80 mA/cm$^2$ of negative ion current density with a two electrode extraction. We report experime…
Resolution performance of programmable proximity aperture MeV ion beam lithography system
2007
AbstractAn ion beam lithography system for light and heavy ions has been developed at the University of Jyväskylä's Accelerator Laboratory. The system employs a programmable proximity aperture to define the beam. The proximity aperture is made up of four Ta blades with precise straight edges that cut the beam in the horizontal and vertical directions. The blade positions and dimensions are controlled by a pair of high-precision linear-motion positioners. The sample is mounted on a X-Y-Z stage capable of moving with 100 nm precision steps under computer control. The resolution performance of the system is primarily governed by the proximity aperture. Pattern edge sharpness is set by the beam…