No Arabic abstract
MESA (Mainz Energy recovery Superconducting Accelerator) is an energy recovery linac (ERL) which is under construction at Johannes Gutenberg University in Mainz. It will be operated in external beam (EB) mode with 150 $mu$A electron beam at 155 MeV and energy recovery (ER) mode with 1 mA (first stage) and later 10 mA (second stage) electron beam at 105 MeV. An important factor which may limit performance of the machine is a beam breakup (BBU) instability which may occur due to excitation of higher-order modes (HOMs) in superconducting RF cavities. This effect occurs only when the injected beam current exceeds a threshold value. The aim of the present work is to develop a software for reliable determination of the threshold current in MESA, find main factors which may change its value and finally make a decision concerning capability of MESA operation at 10 mA and need for additional measures for suppressing BBU instability.
The maximum beam current can be accelerated in an Energy Recovery Linac (ERL) can be severely limited by the transverse multi-pass beam breakup instability (BBU), especially in future ERL light sources with multi-GeV high energy beam energy and more than 100 mA average current. In this paper, the multi-pass BBU of such a high energy ERL is studied based on the simulation on a 3-GeV ERL light source proposed by KEK. It is expected to provide a reference to the future high energy ERL projects by this work.
Moderate ion mobility provides a source of damping in the plasma wakefield acceleration, which may serve as an effective remedy against the transverse instability of the trailing bunch. Ion mobility in the fields of the driving and trailing bunches is taken into account; the related effects are estimated for the FACET-II parameters.
The Long Baseline Neutrino Experiment (LBNE) will utilize a neutrino beamline facility located at Fermilab. The facility is designed to aim a beam of neutrinos toward a detector placed in South Dakota. The neutrinos are produced in a three-step process. First, protons from the Main Injector hit a solid target and produce mesons. Then, the charged mesons are focused by a set of focusing horns into the decay pipe, towards the far detector. Finally, the mesons that enter the decay pipe decay into neutrinos. The parameters of the facility were determined by an amalgam of the physics goals, the Monte Carlo modeling of the facility, and the experience gained by operating the NuMI facility at Fermilab. The initial beam power is expected to be ~700 kW, however some of the parameters were chosen to be able to deal with a beam power of 2.3 MW. The LBNE Neutrino Beam has made significant changes to the initial design through consideration of numerous Value Engineering proposals and the current design is described.
The fast beam-ion instability (FII) is caused by the interaction of an electron bunch train with the residual gas ions. The ion oscillations in the potential well of the electron beam have an inherent frequency spread due to the nonlinear profile of the potential. However, this frequency spread and associated with it Landau damping typically is not strong enough to suppress the instability. In this work, we develop a model of FII which takes into account the frequency spread in the electron beam due to the beam-beam interaction in an electron-ion collider. We show that with a large enough beam-beam parameter the fast ion instability can be suppressed. We estimate the strength of this effect for the parameters of the eRHIC electron-ion collider.
The machine described in this document is an advanced Source of up to 20 MeV Gamma Rays based on Compton back-scattering, i.e. collision of an intense high power laser beam and a high brightness electron beam with maximum kinetic energy of about 720 MeV. Fully equipped with collimation and characterization systems, in order to generate, form and fully measure the physical characteristics of the produced Gamma Ray beam. The quality, i.e. phase space density, of the two colliding beams will be such that the emitted Gamma ray beam is characterized by energy tunability, spectral density, bandwidth, polarization, divergence and brilliance compatible with the requested performances of the ELI-NP user facility, to be built in Romania as the Nuclear Physics oriented Pillar of the European Extreme Light Infrastructure. This document illustrates the Technical Design finally produced by the EuroGammaS Collaboration, after a thorough investigation of the machine expected performances within the constraints imposed by the ELI-NP tender for the Gamma Beam System (ELI-NP-GBS), in terms of available budget, deadlines for machine completion and performance achievement, compatibility with lay-out and characteristics of the planned civil engineering.