Linear particle accelerator

About: Linear particle accelerator is a research topic. Over the lifetime, 6937 publications have been published within this topic receiving 56366 citations. The topic is also known as: Linac & linear accelerator.

Dosimetry for the MRI accelerator:the impact of a magnetic field on the response of a Farmer NE2571 ionization chamber

Abstract: The UMC Utrecht is constructing a 1.5 T MRI scanner integrated with a linear accelerator (Lagendijk et al 2008 Radiother. Oncol. 86 25-9). The goal of this device is to facilitate soft-tissue contrast based image-guided radiotherapy, in order to escalate the dose to the tumour while sparing surrounding normal tissues. Dosimetry for the MRI accelerator has to be performed in the presence of a magnetic field. This paper investigates the feasibility of using a Farmer NE2571 ionization chamber for absolute dosimetry. The impact of the mcagnetic field on the response of this ionization chamber has been measured and simulated using GEANT4 Monte Carlo simulations. Two orientations of the ionization chamber with respect to the incident beam and the magnetic field which are feasible in the MRI accelerator configuration are taken into account. Measurements are performed using a laboratory magnet ranging from 0 to 1.2 T. In the simulations a range from 0 to 2 T is used. For both orientations, the measurements and simulations agreed within the uncertainty of the measurements and simulations. In conclusion, the response of the ionization chamber as a function of the magnetic field is understood and can be simulated using GEANT4 Monte Carlo simulations.

Ionization measurements at very high intensities. Pulsed radiation beams.

Abstract: In pulsed radiation beams the high ion density produced by each pulse encourages recombination between ions of opposite signs. Formulae are derived for the proportion of ions escaping recombination in plane parallel, cylindrical and spherical ionization chambers under a variety of different conditions. The screening effect of space charge is shown to be small in the case of plane geometry. The effect of an exponential fall in collecting voltage, as in condenser chambers, is considered and the appropriate collecting efficiency is derived. Some experimental measurements on a 4 MeV linear accelerator are described.

Low Emittance, High Brilliance Relativistic Electron Beams from a Laser-Plasma Accelerator

Abstract: Progress in laser wakefield accelerators indicates their suitability as a driver of compact free-electron lasers (FELs). High brightness is defined by the normalized transverse emittance, which should be less than 1π mm mrad for an x-ray FEL. We report high-resolution measurements of the emittance of 125 MeV, monoenergetic beams from a wakefield accelerator. An emittance as low as 1.1±0.1π mm mrad is measured using a pepper-pot mask. This sets an upper limit on the emittance, which is comparable with conventional linear accelerators. A peak transverse brightness of 5×10¹⁵ A m⁻¹ rad⁻¹ makes it suitable for compact XUV FELs.

The 1.5 GeV harmonic double-sided microtron at Mainz University

Abstract: At the Institut fur Kernphysik of Mainz University a harmonic double-sided microtron (HDSM) has been built to extend the experimental capabilities for nuclear and particle physics experiments to higher excitation energies. This novel microtron variant accelerates the 0.855 GeV continuous wave (cw) electron beam of the established three-staged race track microtron (RTM) cascade MAMI B up to 1.5 GeV. It consists of two normal conducting linear accelerators (linacs) through which the electrons are guided up to 43 times by a pair of 90°-bending magnets at each end. For beam dynamical reasons the linacs operate at the harmonic frequencies of 4.90 and 2.45 GHz. The extended facility is called MAMI C. The relatively strong vertical defocussing due to the 45°-pole face rotations (Fig. 1) at both the entrance and exit of the segment-shaped bending magnets is compensated for all recirculations by a suitable field decay in the magnets towards higher orbits. As a consequence, the energy gain of the electrons has to decrease with increasing turn number to maintain coherent acceleration. This occurs by an appropriate phase slip of the electron bunches downwards the rf-waves during the acceleration process. In this paper the functional principle and the beam dynamical concept of the double-sided microtron (DSM) as well as the design and development of its main components are described. Finally, the results of first beam measurements taken after starting up in December 2006 are discussed.

Standing Wave High Energy Linear Accelerator Structures

Abstract: The design and operation of resonant linear accelerator tanks suitable for use in high energy proton and electron linacs is described. It is shown that construction of these tanks to operate in the π/2 mode yields systems with extraordinary field stability. Theoretical expressions and corresponding experimental observations are obtained for the behavior of cavity chains operating in the π/2 mode. The synthesis of the side coupled cavity chain, a biperiodic chain which combines high acceleration efficiency with π/2 mode field stability, is described. Extensions of π/2 mode operation to nonperiodic chains is also demonstrated.