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This conceptual design report provides a detailed account of the European Spallation Source neutrino Super Beam (ESS$\nu$SB) feasibility study. This facility has been proposed after the measurements reported in 2012 of a relatively large value of the neutrino mixing angle $\theta_{13}$, which raised the possibility of observing potential CP violation in the leptonic sector with conventional neutrino beams. The measured value of $\theta_{13}$ also privileges the $2^{nd}$ oscillation maximum for the discovery of CP violation instead of the more typically studied $1^{st}$ maximum. The sensitivity at this $2^{nd}$ oscillation maximum is about three times higher than at the $1^{st}$ one, which implies a reduced influence of systematic errors. Working at the $2^{nd}$ oscillation maximum requires a very intense neutrino beam with an appropriate energy. The world's most intense pulsed spallation neutron source, the European Spallation Source (ESS), will have a proton linac operating at 5\,MW power, 2\,GeV kinetic energy and 14~Hz repetition rate (3~ms pulse duration, 4\% duty cycle) for neutron production. In this design study it is proposed to double the repetition rate and compress the beam pulses to the level of microseconds in order to provide an additional 5~MW proton beam for neutrino production. The physics performance has been evaluated for such a neutrino super beam, in conjunction with a megaton-scale underground water Cherenkov neutrino detector installed at a distance of 360--550\,km from ESS. The ESS proton linac upgrades, the accumulator ring required for proton-pulse compression, the target station design and optimisation, the near and far detector complexes, and the physics potential of the facility are all described in this report. The ESS linac will be operational by 2025, at which point the implementation of upgrades for the neutrino facility could begin., Comment: 216 pages

The European Spallation Source (ESS), currently under construction in Lund, Sweden, will be the world’s brightest neutron source, driven by a linear accelerator (LINAC) with an average beam power of 5 MW at 2.0 GeV beam energy. The LINAC accelerates a proton beam of 62.5 mA peak current at 4% duty cycle (2.86 ms at 14 Hz). The accelerator uses a normal conducting front-end bringing the beam energy to 90 MeV, beyond that the acceleration up to 2 GeV is performed using superconducting structures. The first protons were extracted at the ESS site during the commissioning of the ion source and low energy beam transport that started earlier this year and will continue to the next stage of the commissioning up to 21 MeV early next year. This paper gives an overview of the status of the ESS accelerator and the commissioning of the ion source and the low energy beam transport.

The proton linac of the European Spallation Source, under construction in Lund, Sweden, had beam commissioning of its ion source (IS) and the following low energy beam transport (LEBT) at their final locations from September 2018 to July 2019. This was first of several beam commissioning stages for the linac of ESS, towards the start of the user program in 2023. This paper presents highlights of characterizations of the IS and LEBT from the aforementioned beam commissioning period, including behavioral change of the IS against its parameters, error source identifications of the beam trajectory in the LEBT, and preliminary characterization of the LEBT output beam against solenoid strengths in LEBT.

This paper presents a brief summary of the contributions to Working Group 5 (WG5): Beam Sources, Monitoring, and Control. This working group was part of the 2018 Advanced Accelerator Concepts Workshop held at Breckenridge, Colorado, from August 12–17, 2018. There was wide-range of topics covered by this working group ranging from facility updates, new diagnostics and instrumentation schemes, new characterization methods and demonstrations (for both plasma and beam) as well as several advanced concepts that fall outside the scope of the other working groups.

Physical review / X 8(2), 021039 (2018). doi:10.1103/PhysRevX.8.021039, Similarly to laser or x-ray beams, the interaction of sufficiently intense particle beams with neutral gases will result in the creation of plasma. In contrast to photon-based ionization, the strong unipolar field of a particle beam can generate a plasma where the electron population receives a large initial momentum kick and escapes, leaving behind unshielded ions. Measuring the properties of the ensuing Coulomb exploding ions—such as their kinetic energy distribution, yield, and spatial distribution—can provide information about the peak electric fields that are achieved in the electron beams. Particle-in-cell simulations and analytical models are presented for high-brightness electron beams of a few femtoseconds or even hundreds of attoseconds, and transverse beam sizes on the micron scale, as generated by today’s free electron lasers. Different density regimes for the utilization as a potential diagnostics are explored, and the fundamental differences in plasma dynamical behavior for e-beam or photon-based ionization are highlighted. By measuring the dynamics of field-induced ions for different gas and beam densities, a lower bound on the beam charge density can be obtained in a single shot and in a noninvasive way. The exponential dependency of the ionization yield on the beam properties can provide unprecedented spatial and temporal resolution, at the submicrometer and subfemtosecond scales, respectively, offering a practical and powerful approach to characterizing beams from accelerators at the frontiers of performance., Published by APS, College Park, Md.

Using frequency mixing, a modulated light pulse of ns duration is created. We show that, with a ps-resolution streak camera that is usually used for single short pulse measurements, we can detect via an FFT detection approach up to 450 GHz modulation in a pulse in a single measurement. This work is performed in the context of the AWAKE plasma wakefield experiment where modulation frequencies in the range of 80–280 GHz are expected.

In this paper, we present a comparative study for estimating plasma column displacement using multipole moments and discrete magnetic probes methods. It is shown that multipole moments method gives a better performance in the real time determination of the plasma column displacement in IR-T1 tokamak.

Initiating the gain process in a free-electron laser (FEL) from an external highly coherent source of radiation is a promising way to improve the pulse properties such as temporal coherence and synchronization performance in time-resolved pump-probe experiments at FEL facilities, but this so-called "seeding" suffers from the lack of adequate sources at short wavelengths. We report on the first successful seeding at a wavelength as short as 38.2 nm, resulting in GW-level, coherent FEL radiation pulses at this wavelength as well as significant second harmonic emission at 19.1 nm. The external seed pulses are about 1 order of magnitude shorter compared to previous experiments allowing an ultimate time resolution for the investigation of dynamic processes enabling breakthroughs in ultrafast science with FELs. The seeding pulse is the 21st harmonic of an 800-nm, 15-fs (rms) laser pulse generated in an argon medium. Methods for finding the overlap of seed pulses with electron bunches in spatial, longitudinal, and spectral dimensions are discussed and results are presented. The experiment was conducted at FLASH, the FEL user facility at DESY in Hamburg, Germany. (Less)

Recently a proton-bunch-driven plasma wakefield acceleration experiment using the CERN-SPS beam was proposed. Different types of plasma cells are under study, especially laser ionization, plasma discharge, and helicon sources. One of the key parameters is the spatial uniformity of the plasma density profile along the cell that has to be within < 1% of the nominal density (6 × 1014 cm−3). Here a setup based on a photomixing concept is proposed to measure the plasma cut-off frequency and determine the plasma density.

The measurement of current-carrying plasma column displacement is very important for plasma position control. Two methods for this purpose are introduced. In this paper, calculation and construction of these coils is explained. Multiple moment method has been used and derived for construction of sensing coils Also Fourier Transform has been used and derived for continuous coils. The comparison of their advantages are investigated. For IR-T1 Tokamak, Two Cosine coils & two Saddle Sine coils were designed and constructed, which have been placed diametrically around minor radius of torus. Then an electronic circuit was designed for adding and integrating the Cosine and Saddle Sine coils output with proper gain. The contribution of each coils in final output is calculated. For compensation of unwanted pickups voltage from the time varying fields each signal with adjustable gain is added to main signal, until removing the additional field effects. The final output holds good proportionality to H.D.

Since displacement is very important for plasma position control, in IR‐T1 tokamak a combination of two cosine coils and two saddle sine coils is used for horizontal displacement measurement. According to the multiple moment theory, the output of these coils linearly depends to radial displacement of plasma column. A new circuit for adding these signals to feedback system designed and unwanted effects of other fields in final output compensated. After compensation and calibration of the system, the output of horizontal displacement circuits applied to feedback control system. By considers the required auxiliary vertical field, a proportional amplifier and driver circuit are constructed to drive power transistors these power transistors switch the feedback bank capacitors. In the experiment, a good linear proportionality between displacement and output observed by applying an appropriate feedback field, the linger confinement time in IR‐T1 tokamak obtained, applying this system to discharge increased the plasma duration and realizes repetitive discharges.

New acceleration technology is mandatory for the future elucidation of fundamental particles and their interactions. A promising approach is to exploit the properties of plasmas. Past research has focused on creating large-amplitude plasma waves by injecting an intense laser pulse or an electron bunch into the plasma. However, the maximum energy gain of electrons accelerated in a single plasma stage is limited by the energy of the driver. Proton bunches are the most promising drivers of wakefields to accelerate electrons to the TeV energy scale in a single stage. An experimental program at CERN -- the AWAKE experiment -- has been launched to study in detail the important physical processes and to demonstrate the power of proton-driven plasma wakefield acceleration. Here we review the physical principles and some experimental considerations for a future proton-driven plasma wakefield accelerator., 12 pages, 5 figures, submitted to Plasma Phys. Control. Fusion special edition for LPAW 2013. Small updates after comments from Journal referees