Plasma-Wakefield Accelerator Group

Abstract:

The European XFEL cw upgrade requires cavities with reduced surface resistance (high Q-values) for high duty cycle while maintaining high accelerating gradient for short-pulse operation. To improve on European XFEL performance, a recently discovered treatment is investigated: the so-called nitrogen infusion. The recent test results of the cavity-based R&D and the progress of the relevant infrastructure is presented. The aim of this approach is to establish a stable, reproducible recipe and to identify all key parameters for the process. Advanced surface analysis is carried out on cut-outs of cavities and samples treated together with cavities. Techniques used include SEM/EDX, TEM, XPS, XRR, GIXRD and TOF-SIMS. The aim of this approach is to establish a stable, reproducible recipe, to identify key parameters in the process and to understand the underlying processes of the material evolution, that result in the improved performance observed.

Abstract:

This introductory article is a synopsis of the status and prospects of particle-beam-driven plasma wakefield acceleration (PWFA). Conceptual and experimental breakthroughs obtained over the last years have initiated a rapid growth of the research field, and increased maturity of underlying technology allows an increasing number of research groups to engage in experimental R&D.; We briefly describe the fundamental mechanisms of PWFA, from which its chief attractions arise. Most importantly, this is the capability of extremely rapid acceleration of electrons and positrons at gradients many orders of magnitude larger than in conventional accelerators. This allows the size of accelerator units to be shrunk from the kilometre to metre scale, and possibly the quality of accelerated electron beam output to be improved by orders of magnitude. In turn, such compact and high-quality accelerators are potentially transformative for applications across natural, material and life sciences.

Abstract:

Charm production in charged current deep inelastic scattering has been measured for the first time in e±p collisions, using data collected with the ZEUS detector at HERA, corresponding to an integrated luminosity of 358 pb−1. Results are presented separately for e+p and e−p scattering at a centre-of-mass energy of s = 318 GeV within a kinematic phase-space region of 200 GeV2 < Q2 < 60000 GeV2 and y < 0.9, where Q2 is the squared four-momentum transfer and y is the inelasticity. The measured cross sections of electroweak charm production are consistent with expectations from the Standard Model within the large statistical uncertainties.