Search results for "Cathode ray"
showing 10 items of 96 documents
Dosimetric characteristics of backscattered electrons in lead.
2000
In electron beam therapy, tissue overdose due to electrons backscattered from lead has been profusely studied. To quantify this dose enhancement effect, an electron backscatter factor (EBF) was defined as the ratio of dose at the tissue-inhomogeneity interface with and without the scatterer present. The dependence of the EBF on energy at the scatterer surface is not well known for energies lower than 3 MeV which is the most frequent clinical situation. In this work, we have done Monte Carlo calculations with the GEANT code to study EBF in lead at this energy range. The applicability of this code and the developed procedure for dose estimation has been experimentally verified. The dependence…
Laser Compton polarimetry at JLab and MAMI
2007
For modern parity violation experiments it is crucial to measure and monitor the electron beam polarization continuously. In the recent years different high-luminosity concepts, for precision Compton backscattering polarimetry, have been developed, to be used at modern CW electron beam accelerator facilities. As Compton backscattering polarimetry is free of intrinsic systematic uncertainties, it can be a superior alternative to other polarimetry techniques such as Moller and Mott scattering. State-of-the-art high-luminosity Compton backscattering designs currently in use and under development at JLab and Mainz are compared to each other. The latest results from the Mainz A4 Compton polarime…
SU-E-T-237: Monte Carlo Dosimetric Characterization of the Mobetron Mobile Linac
2014
Purpose: The aim of this work is to characterize dosimetrically a clinical intraoperative electron beam accelerator, Mobetron (IntraOp Medical, Inc.) in clinical use in our Hospital. Once this first step is completed our purpose is to evaluate shielding requirements for such a device by preparing adequate phase space files. Methods: It is known that electron beam simulation parameters required for state-of-the-art Monte Carlo codes to obtain a good match with measured data, like the mean energy or the FWHM, may not be code-independent due to the different set of process simulated and formalisms involved. Then, to cross-check our results against any issue in the simulation we have compared e…
Enhancement of Bremsstrahlung Radiation Generated by Electron Beam Interaction in an Axially-Oriented Scintillator Crystal (Poster)
2019
Since their discovery, scintillator materials have played an important role in nuclear and particle physics, as well as in medical and industrial imaging. [...]
Transient optical absorption in KNbO3 crystals irradiated with pulsed electron beam
1997
Abstract Transient optical absorption spectra as well as absorption decay kinetics in pure, Mg- and Rb-doped KNbO 3 have been measured at RT after pulsed (10 ns, 0.27 MeV) electron beam irradiation. Three types of short-lived radiation defects are observed with bands peaking at ∼460 nm, ∼780 nm and > 1000nm. The relevant radiation-induced decay processes are discussed.
Time-resolved optical absorption in YAlO3 crystals
2004
Abstract The present work is devoted to the investigation of transient absorption (TA) induced by a pulsed electron beam (E=250 keV ) in pure and doped YAlO3 (YAP) single crystals. The nature of centers responsible for TA is discussed.
Electronic effects in the production of smali dianionic gold clusters by electron attachment on to stored Au-n, n = 12-28
1999
Abstract Single charged gold clusters Au n -, 12 n 28, are stored in a Penning trap, size selected and transformed into dianions, Au2- n by the application of an electron beam. At the onset of dianion production, that is that range of cluster sizes n where the smallest doubly charged clusters are observed, the measured intensity ratio of the dianions to their precursors is not a continuous function of cluster size. Instead, there is a strong odd-even effect and a comparatively intense signal of Au2-18 The observed structures are very reminiscent of similar phenomena in the abundance spectra of metal clusters as observed by Knight et al. (1984, Phys. Rev. Lett., 52, 2141), which gave ris…
Transient color centers in complex oxide crystals
2005
The present work is devoted to investigation of induced by a pulsed electron beam (E = 0.25 MeV, τ = 10 ns) transient color centers in pure Gd3Ga5O12, YAlO3 and LiNbO3 single crystals. The relaxation of induced absorption of the crystals was studied within 0-5000 ns range. The origin and nature of transient color centers responsible for induced absorption was discussed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
First Observation of Doubly Charged Negative Gold Cluster Ions
1999
Singly charged gold cluster anions in the size range n = 16–30 have been captured, stored and size selected in a Penning trap. After application of an electron beam doubly charged gold cluster anions have been observed for 20 ≤ n ≤ 30. To our knowledge this is the first observation of metal cluster dianions. The threshold appearance size is in good agreement with a simple charged sphere model. The application of argon gas pulses simultaneously with the electron beam is found to increase the production rate by an order of magnitude.
The response behaviour of LiF:Mg,Cu,P thermoluminescence dosimeters to high-energy electron beams used in radiotherapy
1995
To ensure the effectiveness of radiation-therapy treatments, both in-phantom and in-patient reliable dose measurements are required. Thermoluminescence dosimeters are used commonly for both applications. Among the various available materials, the relatively new LiF:Mg,Cu,P phosphor is a suitable candidate for quality control of in vivo dosimetry in electron-beam therapy. The response behaviour of LiF:Mg,Cu,P chips to 6-21 MeV electron beams used in radiotherapy was studied. Batch homogeneity, dose linearity, sensitivity change after use, dose and dose-rate response, energy dependence and fading characteristics were investigated. The contribution from each factor to the overall uncertainty i…