Novel parameter-based flexure bearing design method

A parameter study was carried out on the design variables of a flexure bearing to be used in a Stirling engine with a fixed axial displacement and a fixed outer diameter. A design method was developed in order to assist identification of the optimum bearing configuration. This was achieved through a parameter study of the bearing carried out with ANSYS®. The parameters varied were the number and the width of the arms, the thickness of the bearing, the eccentricity, the size of the starting and ending holes, and the turn angle of the spiral. Comparison was made between the different designs in terms of axial and radial stiffness, the natural frequency, and the maximum induced stresses. Moreover, the Finite Element Analysis (FEA) was compared to theoretical results for a given design. The results led to a graphical design method which assists the selection of flexure bearing geometrical parameters based on pre-determined geometric and material constraints

Expected signal for the TBID and the ionization chambers downstream of the CNGS target station

Downstream of the carbon graphite target of the CNGS (CERN Neutrinos to Gran Sasso) facility at CERN a secondary emission monitor called TBID (Target Beam Instrumentation Downstream) is installed to measure the multiplicities and the left/right as well as up/down asymmetries of secondary particles from the target. Calculations show that the titanium windows used to close off the TBID vacuum tank might not withstand the highest beam intensities with small spot sizes expected at CNGS, in case the proton beam accidentally misses the 4-5 mm diameter target rods. Therefore it has been suggested to place two ionisation chambers as a backup for the TBID, located left and right of the TBID monitor. Monte Carlo simulations with the particle transport code FLUKA were performed firstly to obtain the fluence of charged particles in the region of interest and secondly to estimate the induced radioactivity (background signal) in this area. This allows to assess the actual signal/noise situation and thus to determine the optimal position of the ionisation chambers. This paper presents the results of these calculations

Indirect Self-Modulation Instability Measurement Concept for the AWAKE Proton Beam

AWAKE, the Advanced Proton-Driven Plasma Wakefield Acceleration Experiment, is a proof-of-principle R&D experiment at CERN using a 400 GeV/c proton beam from the CERN SPS (longitudinal beam size sigma_z = 12 cm) which will be sent into a 10 m long plasma section with a nominal density of approx. 7x10^14 atoms/cm3 (plasma wavelength lambda_p = 1.2mm). In this paper we show that by measuring the time integrated transverse profile of the proton bunch at two locations downstream of the AWAKE plasma, information about the occurrence of the self-modulation instability (SMI) can be inferred. In particular we show that measuring defocused protons with an angle of 1 mrad corresponds to having electric fields in the order of GV/m and fully developed self-modulation of the proton bunch. Additionally, by measuring the defocused beam edge of the self-modulated bunch, information about the growth rate of the instability can be extracted. If hosing instability occurs, it could be detected by measuring a non-uniform defocused beam shape with changing radius. Using a 1 mm thick Chromox scintillation screen for imaging of the self-modulated proton bunch, an edge resolution of 0.6 mm and hence a SMI saturation point resolution of 1.2 m can be achieved.Comment: 4 pages, 4 figures, EAAC conference proceeding

High Intensity Commissioning of the SPS LSS4 extraction for CNGS

The SPS LSS4 fast extraction system will serve both the anti-clockwise ring of the LHC and the CERN Gran Sasso Neutrino project (CNGS). CNGS requires 2 fast extractions of 10.5 microsecond long batches, 50 milliseconds apart. Each batch will consist of 2.4 × 1013 protons at 400 GeV. These intensities are factor of 10 above the equipment damage limit in case of beam loss. Active (interlock system) and passive protection systems have to be in place to guarantee safe operation and to respect the radiation limits in zones close to the extraction region. In summer 2006 CNGS was commissioned including extraction with high intensity. A thorough setting-up of the CNGS extraction was carried out as part of the CNGS commissioning, including aperture and beam loss measurements, and defining and checking of interlock thresholds for extraction trajectory, beam loss monitors and radiation monitors. The relevant systems and risks are introduced in this paper, the commissioning results are summarised and comparisons with simulation predictions are presented

Design and Performance of the CNGS Secondary Beam Line

An intense muon-neutrino beam (1017nm /day) is generated at CERN and directed towards the Gran Sasso National Laboratory, LNGS, in Italy, 732 km away from CERN. In the presently approved physics programme, it is foreseen to run the CNGS facility with 4.5.1019 protons per year for five years. During a nominal CNGS cycle, i.e. every 6s, two nominal SPS extractions of 2.4.1013 protons each at 400GeV/c are sent down the proton beam line to the target. The CNGS secondary beam line, starting with the target, has to cope with this situation, which pushes the beam line equipment and instrumentation to the limits of radiation hardness and mechanical stresses during the CNGS operation. An overview of the CNGS secondary beam line is given. Emphasis is on the target, the magnetic focusing lenses (horn and reflector) and the muon monitors. The performance of the secondary beam line during beam commissioning and physics operation is discussed and measurements are compared with simulations

Particle physics applications of the AWAKE acceleration scheme

The AWAKE experiment had a very successful Run 1 (2016-8), demonstrating proton-driven plasma wakefield acceleration for the first time, through the observation of the modulation of a long proton bunch into micro-bunches and the acceleration of electrons up to 2 GeV in 10 m of plasma. The aims of AWAKE Run 2 (2021-4) are to have high-charge bunches of electrons accelerated to high energy, about 10 GeV, maintaining beam quality through the plasma and showing that the process is scalable. The AWAKE scheme is therefore a promising method to accelerate electrons to high energy over short distances and so develop a useable technology for particle physics experiments. Using proton bunches from the SPS, the acceleration of electron bunches up to about 50 GeV should be possible. Using the LHC proton bunches to drive wakefields could lead to multi-TeV electron bunches, e.g. with 3 TeV acceleration achieved in 4 km of plasma. This document outlines some of the applications of the AWAKE scheme to particle physics and shows that the AWAKE technology could lead to unique facilities and experiments that would otherwise not be possible. In particular, experiments are proposed to search for dark photons, measure strong field QED and investigate new physics in electron-proton collisions. The community is also invited to consider applications for electron beams up to the TeV scale.Comment: 12 pages, 8 figures, submitted to the European Particle Physics Strategy Update process. arXiv admin note: substantial text overlap with arXiv:1810.1225

Studying the case in Violation of democratic agreed principles

近年来，涉及村民委员会违反民主议定原则的农业、林业承包合同或林木转让合同群体性纠纷频发，成为人民法院涉农审判的热点和难点。笔者从审判实践的角度，以违反民主议定原则案件受理、事实认定、合同效力认定的过程中存在的争议问题为主要逻辑线索，进行分析、论证，并从宏观上对这类案件在审判实践中遇到的障碍进行总结、分析，尝试为有利于妥善处理此类案件提供纠纷化解的替代途径。 本文除了引言和结语外共分为五章： 第一章违反民主议定原则案件的概述。主要介绍民主议定原则的概念、法律规定，以及违反民主议定原则案件的概念、特点、类型。 第二章违反民主议定原则案件的受理。对《最高人民法院关于审理农业承包合同纠纷案件若干...In recent years, the disputes happened frequently that the villagers committee violates the democracy agreed principles in agriculture, forestry contract or trees transfered contract, which becomes the hot and difficulty for the trial of the People's Count. The author is to be from the trial standpoint to analyse and proof the process of the case acceptance, truth identification, the identificatio...学位：法律硕士院系专业：法学院法律系_法律硕士(JM)学号：X200812013

Measurement and application of electron stripping of ultrarelativistic 208Pb81+^{208}\textrm{Pb}^{81+}

New measurements of the stripping cross-section for ultrarelativistic hydrogen-like lead ions passing through aluminium and silicon have been performed at the Advanced Wakefield experiment at CERN. Agreement with existing measurements and theory has been obtained. Improvements in terms of electron beam quality and ion beam diagnostic capability, as well as further applications of such an electron beam, are discussed

Controlled growth of the self-modulation of a relativistic proton bunch in plasma

A long, narrow, relativistic charged particle bunch propagating in plasma is subject to the self-modulation (SM) instability. We show that SM of a proton bunch can be seeded by the wakefields driven by a preceding electron bunch. SM timing reproducibility and control are at the level of a small fraction of the modulation period. With this seeding method, we independently control the amplitude of the seed wakefields with the charge of the electron bunch and the growth rate of SM with the charge of the proton bunch. Seeding leads to larger growth of the wakefields than in the instability case.info:eu-repo/semantics/publishedVersio