Residual Dispersion in a Combiner Ring

In this paper we present a proof to show that there exists no system of linear or nonlinear optics which can simultaneously close multiple local orbit bumps and dispersion through a single beam transport region. The second combiner ring in the CLIC drive beam recombination system, CR2, is used as an example of where such conditions are necessary. We determine the properties of a lattice which is capable of closing the local orbit bumps and dispersion and show that all resulting solutions are either unphysical or trivial.Comment: Submitted to PRST-AB on 04/18/201

Dispersion in closed, off-axis orbit bumps

In this paper we present a proof to show that there exists no system of linear or nonlinear optics which can simultaneously close multiple local orbit bumps and dispersion through a single beam transport region. The second combiner ring in the CLIC drive beam recombination system, CR2, is used as an example of where such conditions are necessary. We determine the properties of a lattice which is capable of closing the local orbit bumps and dispersion and show that all resulting solutions are either unphysical or trivial

The general fault in our fault lines

Pervading global narratives suggest that political polarization is increasing, yet the accuracy of such group meta-perceptions has been drawn into question. A recent US study suggests that these beliefs are inaccurate and drive polarized beliefs about out-groups. However, it also found that informing people of inaccuracies reduces those negative beliefs. In this work, we explore whether these results generalize to other countries. To achieve this, we replicate two of the original experiments with 10,207 participants across 26 countries. We focus on local group divisions, which we refer to as fault lines. We find broad generalizability for both inaccurate meta-perceptions and reduced negative motive attribution through a simple disclosure intervention. We conclude that inaccurate and negative group meta-perceptions are exhibited in myriad contexts and that informing individuals of their misperceptions can yield positive benefits for intergroup relations. Such generalizability highlights a robust phenomenon with implications for political discourse worldwide

Proof of the nonexistence of a linear solution for the CR2 injection region of the CLIC drive beam

In this paper we present a mathematical proof to show that there exists no linear system of optics which can simultaneously close an orbit bump and correct the dispersion in the CR2 injection region. Due to the requirements of the CR2 injection region, several different trajectories will exist through the injection region which are off-axis; therefore the orbit and dispersion functions need to be corrected. In this paper, we determine the properties of a hypothetical linear lattice which is capable of closing the orbit and dispersion functions and then show that the resulting solutions are either unphysical or trivial. Geneva

Design specifications for the extraction elements of the CLIC drive beam combiners rings

In this paper we present updated design specifications for the combiner ring extraction kickers and preliminary design specifications for the extraction septum magnet

Bunch Compressor Design for CLIC Drive Beam

The drive-beam linac which is required for generation RF power at Compact Linear Collider (CLIC) has to accelerate an electron beam with 8.4 nC per bunch up to 2.4 GeV in almost fully loaded structures. The required beam stability in both transverse and longitudinal directions are of concern for such a high bunch charge. We present different bunch compressor designs for the Drive Beam and compare their performance including the effects beam energy and phase jitters

CLIC Decelerator - Machine Protection

The Compact Linear Collider CLIC is based on a four beam scheme, two colliding beams (main beams) and two drive beams, which are used to accelerate the main beams. The intended drive beam parameters exceed the "safe beam" threshold by a factor of 100. Hence, in case of a beam impact serious structural damages of the accelerator equipment are expected. In order to avoid structural damages caused by the drive beam detailed studies of its beam dynamics are on-going. In this paper the major characteristics of the drive-beam beam-dynamics and preliminary machine protection results are summarised

Energy and Beam-Offset dependence of the Luminosity weighted depolarization for CLIC

We report on simulations of e+e- depolarization due to beam-beam effects. These effects are studied for CLIC at 3 TeV, using GUINEA PIG++. We find a strong energy dependence of the luminosity weighted depolarization. In the luminosity peak at CLIC the total luminosity weighted depolarization remains below the one per-mil level. The effect of a vertical offset on the energy dependent depolarization is investigated. The depolarization in the luminosity peak remains below per-cent level even for 5sy offsets

Direct measurement of the formation length of photons

We report the first observation of a shoulder in the radiation spectrum from GeV electrons in a structured target consisting of two thin and closely spaced foils. The position of the shoulder depends on the target spacing and is directly connected to the finite formation length of a low-energy photon emitted by an ultrarelativistic electron.With the present setup it is possible to control the separation of the foils on a m scale and hence measure interference effects caused by the macroscopic dimensions of the formation length. Several theoretical groups have predicted this effect using different methods. Our observations have a preference for the modified theory by Blankenbecler but disagree with the results of Baier and Katkov