Influence of Heat Treatment Mode of Various Magnesia Rocks on their Properties

Investigations of the changes of structure, specific surface and true density of following high-magnesia rocks at heat treatment have been performed: brucite rocks, magnesite, hydromagnesia rocks, amorphous magnesite. It has been revealed that to obtain chemically active magnesium oxide, which is used for synthesis of high-refractory materials and obtaining magnesia binder, it is necessary to burn at low or moderate temperatures in the temperature range of 500-800 °С. Increase of temperature more than 800 °С leads to obtaining densely sintered cubic magnesium oxide with the periclase structure

Path to AWAKE : evolution of the concept

This paper describes the conceptual steps in reaching the design of the AWAKE experiment currently under construction at CERN. We start with an introduction to plasma wakefield acceleration and the motivation for using proton drivers. We then describe the self-modulation instability - a key to an early realization of the concept. This is then followed by the historical development of the experimental design, where the critical issues that arose and their solutions are described. We conclude with the design of the experiment as it is being realized at CERN and some words on the future outlook. A summary of the AWAKE design and construction status as presented in this conference is given in Gschwendtner et al. [1]

Influence of Heat Treatment Mode of Various Magnesia Rocks on their Properties

AbstractInvestigations of the changes of structure, specific surface and true density of following high-magnesia rocks at heat treatment have been performed: brucite rocks, magnesite, hydromagnesia rocks, amorphous magnesite. It has been revealed that to obtain chemically active magnesium oxide, which is used for synthesis of high-refractory materials and obtaining magnesia binder, it is necessary to burn at low or moderate temperatures in the temperature range of 500-800°C. Increase of temperature more than 800°C leads to obtaining densely sintered cubic magnesium oxide with the periclase structure

Witness emittance growth caused by driver density fluctuations in plasma wakefield accelerators

International audienceWe discovered a novel effect that can cause witness emittance growth in plasma wakefield accelerators. The effect appears in linear or moderately nonlinear plasma waves. The witness experiences a time-varying focusing force and loses quality during the time required for the drive beam to reach transverse equilibrium with the plasma wave. The higher the witness charge, the lower the emittance growth rate because of additional focusing of the witness by its own wakefield. However, the witness head always degrades, and the boundary between degraded and intact parts gradually propagates backward along the witness bunch

Evolution of a plasma column measured through modulation of a high-energy proton beam

Plasma wakefield acceleration is a method for accelerating particle beams using electromagnetic fields that are orders of magnitude larger than those found in conventional radio frequency cavities. The core component of a plasma wakefield accelerator is the plasma source, which ranges from millimeter-scale gas jets used in laser-driven experiments, to the ten-meter-long rubidium cell used in the AWAKE experiment. The density of the neutral gas is a controlled input to the experiment, but the density of the plasma after ionization depends on many factors. AWAKE uses a high-energy proton beam to drive the plasma wakefield, and the wakefield acts back on the proton bunch by modulating it at the plasma frequency. We infer the plasma density by measuring the frequency of modulation of the proton bunch, and we measure the evolution of the density versus time by varying the arrival of the proton beam with respect to the ionizing laser pulse. Using this technique, we uncover a microsecond-long period of a stable plasma density followed by a rapid decay in density. The stability of the plasma after ionization has implications for the design of much longer vapor cells that could be used to accelerate particle beams to extremely high energies

Proton beam defocusing in AWAKE: comparison of simulations and measurements

In 2017, AWAKE demonstrated the seeded self-modulation (SSM) of a 400 GeV proton beam from the Super Proton Synchrotron (SPS) at CERN. The angular distribution of the protons deflected due to SSM is a quantitative measure of the process, which agrees with simulations by the two-dimensional (axisymmetric) particle-in-cell code LCODE. Agreement is achieved for beam populations between $10^{11}$ and $3 \times 10^{11}$ particles, various plasma density gradients ($-20 \div 20\%$) and two plasma densities ($2\times 10^{14} \text{cm}^{-3}$ and $7 \times 10^{14} \text{cm}^{-3}$). The agreement is reached only in the case of a wide enough simulation box (at least five plasma wavelengths)