278 research outputs found
The FLASHForward Facility at DESY
The FLASHForward project at DESY is a pioneering plasma-wakefield
acceleration experiment that aims to produce, in a few centimetres of ionised
hydrogen, beams with energy of order GeV that are of quality sufficient to be
used in a free-electron laser. The plasma wave will be driven by high-current
density electron beams from the FLASH linear accelerator and will explore both
external and internal witness-beam injection techniques. The plasma is created
by ionising a gas in a gas cell with a multi-TW laser system, which can also be
used to provide optical diagnostics of the plasma and electron beams due to the
<30 fs synchronisation between the laser and the driving electron beam. The
operation parameters of the experiment are discussed, as well as the scientific
program.Comment: 19 pages, 9 figure
Energy-Spread Preservation and High Efficiency in a Plasma-Wakefield Accelerator
Energy-efficient plasma-wakefield acceleration of particle bunches with low energy spread is a promising path to realizing compact free-electron lasers and particle colliders. High efficiency and low energy spread can be achieved simultaneously by strong beam loading of plasma wakefields when accelerating bunches with carefully tailored current profiles [M. Tzoufras et al., Phys. Rev. Lett. 101, 145002 (2008)PRLTAO0031-900710.1103/PhysRevLett.101.145002]. We experimentally demonstrate such optimal beam loading in a nonlinear electron-driven plasma accelerator. Bunches with an initial energy of 1 GeV were accelerated by 45 MeV with an energy-transfer efficiency of (42±4)% at a gradient of 1.3 GV/m while preserving per-mille energy spreads with full charge coupling, demonstrating wakefield flattening at the few-percent level
Tunable and precise two-bunch generation at FLASHForward
Beam-driven plasma-wakefield acceleration based on external injection has the
potential to significantly reduce the size of future accelerators. Stability
and quality of the acceleration process substantially depends on the incoming
bunch parameters. Precise control of the current profile is essential for
optimising energy-transfer efficiency and preserving energy spread. At the
FLASHForward facility, driver--witness bunch pairs of adjustable bunch length
and separation are generated by a set of collimators in a dispersive section,
which enables fs-level control of the longitudinal bunch profile. The design of
the collimator apparatus and its commissioning is presented.Comment: 7 pages, 5 figures, to be published in the proceedings of the 4th
European Advanced Accelerator Concepts Workshop, 15-21 September 2019, La
Biodola Bay, Isola d'Elba, Ital
Measurement of neutral current e+/-p cross sections at high Bjorken x with the ZEUS detector
The neutral current e+/-p cross section has been measured up to values of
Bjorken x of approximately 1 with the ZEUS detector at HERA using an integrated
luminosity of 187 inv. pb of e-p and 142 inv. pb of e+p collisions at sqrt(s) =
318GeV. Differential cross sections in x and Q2, the exchanged boson
virtuality, are presented for Q2 geq 725GeV2. An improved reconstruction method
and greatly increased amount of data allows a finer binning in the high-x
region of the neutral current cross section and leads to a measurement with
much improved precision compared to a similar earlier analysis. The
measurements are compared to Standard Model expectations based on a variety of
recent parton distribution functions.Comment: 39 pages, 9 figure
Infrastructure for Detector Research and Development towards the International Linear Collider
The EUDET-project was launched to create an infrastructure for developing and
testing new and advanced detector technologies to be used at a future linear
collider. The aim was to make possible experimentation and analysis of data for
institutes, which otherwise could not be realized due to lack of resources. The
infrastructure comprised an analysis and software network, and instrumentation
infrastructures for tracking detectors as well as for calorimetry.Comment: 54 pages, 48 picture
Measurement of the cross-section ratio sigma_{psi(2S)}/sigma_{J/psi(1S)} in deep inelastic exclusive ep scattering at HERA
The exclusive deep inelastic electroproduction of and
at an centre-of-mass energy of 317 GeV has been studied with the ZEUS
detector at HERA in the kinematic range GeV,
GeV and GeV, where is the photon virtuality, is the
photon-proton centre-of-mass energy and is the squared four-momentum
transfer at the proton vertex. The data for GeV were taken in
the HERA I running period and correspond to an integrated luminosity of 114
pb. The data for GeV are from both HERA I and HERA II
periods and correspond to an integrated luminosity of 468 pb. The decay
modes analysed were and for the
and for the . The cross-section ratio
has been measured as a function of
and . The results are compared to predictions of QCD-inspired
models of exclusive vector-meson production.Comment: 24 pages, 8 figure
Eupraxia, a step toward a plasma-wakefield based accelerator with high beam quality
The EuPRAXIA project aims at designing the world's first accelerator based on advanced plasma-wakefield techniques to deliver 5 GeV electron beams that simultaneously have high charge, low emittance and low energy spread, which are required for applications by future user communities. Meeting this challenging objective will only be possible through dedicated effort. Many injection/acceleration schemes and techniques have been explored by means of thorough simulations in more than ten European research institutes. This enables selection of the most appropriate methods for solving each particular problem. The specific challenge of generating, extracting and transporting high charge beams, while maintaining the high quality needed for user applications, are being tackled using innovative approaches. This article highlights preliminary results obtained by the EuPRAXIA collaboration, which also exhibit the required laser and plasma parameters
Improved functionalization of oleic acid-coated iron oxide nanoparticles for biomedical applications
Superparamagnetic iron oxide nanoparticles
can providemultiple benefits for biomedical applications
in aqueous environments such asmagnetic separation or
magnetic resonance imaging. To increase the colloidal
stability and allow subsequent reactions, the introduction
of hydrophilic functional groups onto the particles’
surface is essential. During this process, the original
coating is exchanged by preferably covalently bonded
ligands such as trialkoxysilanes. The duration of the
silane exchange reaction, which commonly takes more
than 24 h, is an important drawback for this approach. In
this paper, we present a novel method, which introduces
ultrasonication as an energy source to dramatically
accelerate this process, resulting in high-quality waterdispersible nanoparticles around 10 nmin size. To prove
the generic character, different functional groups were
introduced on the surface including polyethylene glycol
chains, carboxylic acid, amine, and thiol groups. Their
colloidal stability in various aqueous buffer solutions as
well as human plasma and serum was investigated to
allow implementation in biomedical and sensing
applications.status: publishe
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