Transmission and reflection of electrons by foils

Advances in Monte-Carlo code TRIPOLI-4®’s treatment of the electromagnetic cascade

TRIPOLI-4® is a Monte-Carlo particle-transport code developed at CEA-Saclay (France) that is employed in the domains of nuclear-reactor physics, criticality-safety, shielding/radiation protection and nuclear instrumentation. The goal of this paper is to report on current developments, validation and verification made in TRIPOLI-4 in the electron/positron/photon sector. The new capabilities and improvements concern refinements to the electron transport algorithm, the introduction of a charge-deposition score, the new thick-target bremsstrahlung option, the upgrade of the bremsstrahlung model and the improvement of electron angular straggling at low energy. The importance of each of the developments above is illustrated by comparisons with calculations performed with other codes and with experimental data.

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Observation of the diphoton decay of the Higgs boson and measurement of its properties

Observation of the diphoton decay mode of the recently discovered Higgs boson and measurement of some of its properties are reported. The analysis uses the entire dataset collected by the CMS experiment in proton-proton collisions during the 2011 and 2012 LHC running periods. The data samples correspond to integrated luminosities of 5.1[Formula: see text]at [Formula: see text] and 19.7[Formula: see text]at 8[Formula: see text] . A clear signal is observed in the diphoton channel at a mass close to 125[Formula: see text] with a local significance of [Formula: see text], where a significance of [Formula: see text] is expected for the standard model Higgs boson. The mass is measured to be [Formula: see text] , and the best-fit signal strength relative to the standard model prediction is [Formula: see text][Formula: see text][Formula: see text]. Additional measurements include the signal strength modifiers associated with different production mechanisms, and hypothesis tests between spin-0 and spin-2 models.

Improved modeling of multiple scattering in the Voxel Monte Carlo model

The implementation of an improved model for multiple scattering into the-Voxel Monte Carlo (VMC) algorithm for fast electron dose calculation in radiation therapy is presented. The model takes into account path-length corrections (PLC) and lateral displacement in the individual electron steps. The extraction of the scattering power from the available computed-tomography images is discussed. It is shown that with the improved modeling of multiple electron scattering, the VMC algorithm is comparable in accuracy with PRESTA, the electron transport algorithm of EGS4. The problem of double counting of contributions from atomic electrons to the scattering power is considered and a simple solution is found.

Fixation for biological ultrastructure. II. Cross-linking of bovine serum albumin by nanosecond pulses of ionizing radiation

Very large doses of ionizing radiation were delivered quickly to concentrated albumin solutions by pulses of 500 keV in air. The electrons penetrated the aluminium foil bottom of the test cell and into the solution. A dose of 4.6 Mrad (4.6 x 10(4) Gy) produced a gel in the albumin solution comparable to the long-term effect of 0.36% glutaraldehyde in the same albumin solution. The cross-links created by the radiation leading to gel formation are probably irreversible and quite different from those leading to gelation in the glutaraldehyde-albumin reaction. Single large pulses of ionizing radiation may be useful for fast fixation of cells and tissues for microscopy.

Electron dosimetry with thermally stimulated exoelectron emission (TSEE)

The dependence of exoelectron emission from BeO and Al2O3 on primary electron energy has been measured over the 200 keV to 1.2 MeV range. Two types of measurements are made, firstly with the isotopes 90Sr + 90Y, 147Pm, 204Tl, and secondly for BeO with monoenergetic electrons from an accelerator. The TSEE response of covered BeO-dosemeters (cover of 7 mg cm-2 polyethylene) is independent from electron energies in the 200 to 700 keV range for constant equivalent doses (ICRP 21). The experimental results for uncovered TSEE-dosemeters and electron fluences are in agreement with calculations performed using a Monte Carlo program developed by Seltzer and Berger. The TSEE responses for electrons and photons in equivalent dose units are very similar. A lower detection limit of 20 mu Gy (absorbed dose in air) is found for this dosemeter.

Accuracy of megavolt radiation dosimetry using thermoluminescent lithium fluoride

The relative light output per Gy in polystyrene for roentgen beams of 6 and 42 MV and electrons between 2.2 and 34.5 MeV relative to 60Co gamma radiation is reported for different kinds of LiF dosemeters. The distribution of the absorbed dose inside a 0.25 and 0.4 mm thick LiF-teflon disc surrounded by polystyrene and irradiated with 60Co, 42 MV roentgen radiation and 39 MeV electrons was measured using 0.01 and 0.02 mm thick Lif-teflon discs. The measurements show that the absorbed dose distribution in the dosemeter depends on the energy of the radiation. When flat dosemeters were used, differences between the signals measured at the two orientations possible during read-out could easily amount to several per cent, and for this reason 0.4 mm and 0.5 mm LiF-Teflon discs were not trusted when the highest accuracy was required. The cavity theory by Burlin does not account for the phenomena caused by differences in electron scattering properties of the dosemeter and the phantom material. Some suggestions are presented for a different cavity theory for flat dosemeters dealing also with these phenomena. It describes the results to about the same degree of approximation as the Burlin theory, and fails to explain the observed energy dependence for electrons.