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

Commissioning of the electron injector for the AWAKE experiment

The advanced wakefield experiment (AWAKE) at CERN is the first proton beam-driven plasma wakefield acceleration experiment. The main goal of AWAKE RUN 1 was to demonstrate seeded self-modulation (SSM) of the proton beam and electron witness beam acceleration in the plasma wakefield. For the AWAKE experiment, a 10-meter-long Rubidium-vapor cell together with a high-power laser for ionization was used to generate the plasma. The plasma wakefield is driven by a 400 GeV/c proton beam extracted from the super proton synchrotron (SPS), which undergoes a seeded self-modulation process in the plasma. The electron witness beam used to probe the wakefields is generated from an S-band RF photo-cathode gun and then accelerated by a booster structure up to energies between 16 and 20 MeV. The first run of the AWAKE experiment revealed that the maximum energy gain after the plasma cell is 2 GeV, and the SSM mechanism of the proton beam was verified. In this paper, we will present the details of the AWAKE electron injector. A comparison of the measured electron beam parameters, such as beam size, energy, and normalized emittance, with the simulation results was performed

High quality electron beam generation in a proton-driven hollow plasma wakefield accelerator

Simulations of proton-driven plasma wakefield accelerators have demonstrated substantially higher accelerating gradients compared to conventional accelerators and the viability of accelerating electrons to the energy frontier in a single plasma stage. However, due to the strong intrinsic transverse fields varying both radially and in time, the witness beam quality is still far from suitable for practical application in future colliders. Here we demonstrate efficient acceleration of electrons in proton-driven wakefields in a hollow plasma channel. In this regime, the witness bunch is positioned in the region with a strong accelerating field, free from plasma electrons and ions. We show that the electron beam carrying the charge of about 10% of 1 TeV proton driver charge can be accelerated to 0.6 TeV with preserved normalized emittance in a single channel of 700 m. This high quality and high charge beam may pave the way for the development of future plasma-based energy frontier colliders.Comment: 10 pages, 7 figure

Interregional Air Pollutant Transport: The Linearity Question

This report contains extended abstracts from an international meeting held in Budapest, Hungary. Its main subject is the question of proportionality and linearity between emissions and deposition/airborne concentration of air pollutants including sulfur, nitrogen, oxidants, and acidity. Session topics (which serve here as section headings) included analysis of measurements, ammonia and its implications for linearity, modeling with emphasis on chemistry, simplified approaches to the linearity issue, and results from long-range transport models. Linearity was found to be strongly dependent on the distance between emitters and receptors, the averaging time of pollutants, and the form of deposition

Implications of beam filling patterns on the design of recirculating Energy Recovery Linacs

Recirculating energy recovery linacs are a promising technology for being able to deliver high power particle beams (~GW) while only requiring low power (~kW) RF sources. This is achieved by decelerating the used bunches and using the energy they deposit in the accelerating structures to accelerate new bunches. We present studies of the impact of the bunch train filling pattern on the performance of the accelerating RF system. We perform RF beam loading simulations under various noise levels and beam loading phases with different linac topologies. We also present a mathematical description of the RF system during the beam loading, which can identify optimal beam filling patterns under different conditions. The results of these studies have major implications for design constraints for future energy recovery linacs, by providing a quantitative metric for different machine designs and topologies

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

Jet and hadron production in photon-photon collisions

Di-jet and inclusive charged hadron production cross-sections measured in photon-photon collisions by OPAL are compared to NLO pQCD calculations. Jet shapes measured in photon-photon scattering by OPAL, in deep-inelastic ep scattering by H1 and in photon-proton scattering by ZEUS are shown to be consistent in similar kinematic ranges. New results from TOPAZ on prompt photon production in photon-photon interactions are presented.Comment: 4 pages, submitted to Proceedings of DIS99, DESY-Zeuthen, Germany, April 199

A MAPS based readout for Tera: Pixel electromagnetic calorimeter at the ILC

A Monolithic Active Pixel Sensors (MAPS) based - option for the ILC ECAL will be presented. This novel design provides extremely fine granularity with integrated binary readout. This leads to a Tera-Pixel electromagnetic calorimeter system. An overview of the MAPS proposed solution will be given along with the advantages of this approach. A novel CMOS process used for the fabrication of the first MAPS prototype will be introduced and described. Device simulation results showing the expected detector performance will be shown. Initial preliminary reports from basic tests of the prototype will be given

Active lower order mode damping for the four rod LHC crab cavity

The high luminosity upgrade planned for the LHC requires crab cavities to rotate bunches into alignment at the interaction points. They compensate for a crossing angle near to 500~$\mu$Rad. It is anticipated that four crab cavities in succession will be utilized to achieve this rotation either side of each IP in a local crossing scheme. A crab cavity operates in a dipole mode but always has an accelerating mode that may be above or below the frequency of the operating mode. Crab cavities are given couplers to ensure that unwanted acceleration modes are strongly damped however employing standard practice these unwanted modes will always have some level of excitation. Where this excitation has a random phase it might promote bunch growth and limit beam lifetime. This paper sets out a method for active control of the phase and amplitude of the unwanted lowest accelerating mode in the crab cavities. The paper investigates the level of suppression that can be achieved as a function cavity quality factor and proximity to resonance