Explore the vast range of titles available.

The experiment described in this paper is the first study of the response of a static tungsten powder sample to an impinging high energy proton beam pulse. The experiment was carried out at the HiRadMat facility at CERN. Observations include high speed videos of a proton beam induced perturbation of the powder sample as well as data from a laser Doppler vibrometer measuring the oscillations of the powder container. A comparison with a previous analogous experiment which studied a proton beam interaction with mercury is made.

This paper reports the results from single-pulse experiments of a440GeV/cproton beam interacting with granular tungsten samples in both vacuum and helium environments. Remote high-speed photography and laser Doppler vibrometry were used to observe the effect of the beam on the sample grains. The majority of the results were derived from a trough containing∼45μmdiameter spheres (not compacted) reset between experiments to maintain the same initial conditions. Experiments were also carried out on other open and contained samples for the purposes of comparison both with the45μmgrain results and with a previous experiment carried out with sub-250μm mixed crystalline tungsten powder in helium [Phys. Rev. ST Accel. Beams 17, 101005 (2014)]. The experiments demonstrate that a greater dynamic response is produced in a vacuum than in a helium environment and in smaller grains compared with larger grains. The examination of the dynamics of the grains after a beam impact leads to the hypothesis that the grain response is primarily the result of a charge interaction of the proton beam with the granular medium.

The Long Baseline Neutrino Facility (LBNF, formerly the Long Baseline Neutrino Experiment) is under design as a next generation neutrino oscillation experiment, with primary objectives to search for CP violation in the leptonic sector, to determine the neutrino mass hierarchy and to provide a precise measurement of θ23 . The facility will generate a neutrino beam at Fermilab by the interaction of a proton beam with a target material. At the ultimate anticipated proton beam power of 2.3 MW the target material must dissipate a heat load of between 10 and 25 kW depending on the target size. This paper presents a target concept based on an array of spheres and compares it to a cylindrical monolithic target such as that which currently operates at the T2K facility. Simulation results show that the proposed technology offers efficient cooling and lower stresses whilst delivering a neutrino production comparable with that of a conventional solid cylindrical target.

Fluidized tungsten powder has been proposed as a potential target technology for particle accelerator applications with very high power highly focused pulsed beams. This has motivated a series of experiments carried out at the HiRadMat facility at CERN to study the response of a tungsten powder sample to an impinging high energy proton beam pulse. The main observation was that of beam induced lifting of the powder sample which was recorded by high speed video. In this paper we consider three mechanisms to explain the observed powder lift including aerodynamic, thermal expansion and induced charge effects. Simulations of the aerodynamic effect revealed that this could not explain the magnitude of the observed eruptions especially during tests carried out with the powder in a vacuum. Thermal expansion of tungsten particles giving rise to the eruption seems implausible due to the propensity for the powder to absorb perturbations. We show that the observations can be explained by a Coulombic eruption of the tungsten particles. The high energy beam leaves a pattern of charge distributed in the poorly conducting powder sample, which creates an electric field that consequently results in a force acting on the individual charged particles. We calculate the charge deposited, the electric field and the resulting acceleration and show that this is a plausible mechanism for causing the observed eruptions. We believe the response of a granular conductive sample to an incident proton beam has not previously been explained.

The charge-conjugation and parity-reversal (CP) symmetry of fundamental particles is a symmetry between matter and antimatter. Violation of this CP symmetry was first observed in 1964 1 , and CP violation in the weak interactions of quarks was soon established 2 . Sakharov proposed 3 that CP violation is necessary to explain the observed imbalance of matter and antimatter abundance in the Universe. However, CP violation in quarks is too small to support this explanation. So far, CP violation has not been observed in non-quark elementary particle systems. It has been shown that CP violation in leptons could generate the matter–antimatter disparity through a process called leptogenesis 4 . Leptonic mixing, which appears in the standard model’s charged current interactions 5 , 6 , provides a potential source of CP violation through a complex phase δ CP , which is required by some theoretical models of leptogenesis 7 – 9 . This CP violation can be measured in muon neutrino to electron neutrino oscillations and the corresponding antineutrino oscillations, which are experimentally accessible using accelerator-produced beams as established by the Tokai-to-Kamioka (T2K) and NOvA experiments 10 , 11 . Until now, the value of δ CP has not been substantially constrained by neutrino oscillation experiments. Here we report a measurement using long-baseline neutrino and antineutrino oscillations observed by the T2K experiment that shows a large increase in the neutrino oscillation probability, excluding values of δ CP that result in a large increase in the observed antineutrino oscillation probability at three standard deviations (3 σ ). The 3 σ confidence interval for δ CP , which is cyclic and repeats every 2π, is [−3.41, −0.03] for the so-called normal mass ordering and [−2.54, −0.32] for the inverted mass ordering. Our results indicate CP violation in leptons and our method enables sensitive searches for matter–antimatter asymmetry in neutrino oscillations using accelerator-produced neutrino beams. Future measurements with larger datasets will test whether leptonic CP violation is larger than the CP violation in quarks. The T2K experiment constrains CP symmetry in neutrino oscillations, excluding 46% of possible values of the CP violating parameter at a significance of three standard deviations; this is an important milestone to test CP symmetry conservation in leptons and whether the Universe’s matter–antimatter imbalance originates from leptons.

We present a new design study of the neutrino Super Beam based on the Superconducting Proton Linac at CERN. This beam is aimed at megaton mass physics, a large water Cherenkov detector, proposed for the Laboratoire Souterrain de Modane in France, with a baseline of 130 km. The aim of this proposed facility is to study CP violation in the neutrino sector. In the study reported here, we have developed the conceptual design of the neutrino beam, especially the target and the magnetic focusing device. Indeed, this beam presents several unprecedented challenges, related to the high primary proton beam power (4 MW), the high repetition rate (50 Hz), and the low kinetic energy of the protons (4.5 GeV). The design is completed by a study of all the main components of the system, starting from the transport system to guide the beam to the target up to the beam dump. This is the first complete study of a neutrino beam based on a pebble-bed target capable of standing the large heat deposition of MW class proton beams.

The properties of the neutrino provide a unique window on physics beyond that described by the standard model. The study of subleading effects in neutrino oscillations, and the race to discover CP-invariance violation in the lepton sector, has begun with the recent discovery that θ13>0 . The measured value of θ13 is large, emphasizing the need for a facility at which the systematic uncertainties can be reduced to the percent level. The neutrino factory, in which intense neutrino beams are produced from the decay of muons, has been shown to outperform all realistic alternatives and to be capable of making measurements of the requisite precision. Its unique discovery potential arises from the fact that only at the neutrino factory is it practical to produce high-energy electron (anti)neutrino beams of the required intensity. This paper presents the conceptual design of the neutrino factory accelerator facility developed by the European Commission Framework Programme 7 EUROν Design Study consortium. EUROν coordinated the European contributions to the International Design Study for the Neutrino Factory (the IDS-NF) collaboration. The EUROν baseline accelerator facility will provide 1021 muon decays per year from 12.6 GeV stored muon beams serving a single neutrino detector situated at a source-detector distance of between 1 500 km and 2 500 km. A suite of near detectors will allow definitive neutrino-scattering experiments to be performed.

Beryllium is a material extensively used in various particle accelerator beam lines and target facilities, as beam windows and, to a lesser extent, as secondary particle production targets. With increasing beam intensities of future multimegawatt accelerator facilities, these components will have to withstand even greater thermal and mechanical loads during operation. As a result, it is critical to understand the beam-induced thermal shock limit of beryllium to help reliably operate these components without having to compromise particle production efficiency by limiting beam parameters. As part of the RaDIATE (radiation damage in accelerator target environments) Collaboration, an exploratory experiment to probe and investigate the thermomechanical response of several candidate beryllium grades was carried out at CERN’s HiRadMat facility, a user facility capable of delivering very-high-intensity proton beams to test accelerator components. Multiple arrays of thin beryllium disks of varying thicknesses and grades, as well as thicker cylinders, were exposed to increasing beam intensities to help identify any thermal shock failure threshold. Real-time experimental measurements and postirradiation examination studies provided data to compare the response of the various beryllium grades, as well as benchmark a recently developed beryllium Johnson-Cook strength model.

The Technical Design for the COMET Phase-I experiment is presented in this paper. COMET is an experiment at J-PARC, Japan, which will search for neutrinoless conversion of muons into electrons in the field of an aluminum nucleus ($\\mu$–$e$ conversion, $\\mu^{-}N \\rightarrow e^{-}N$); a lepton flavor-violating process. The experimental sensitivity goal for this process in the Phase-I experiment is $3.1\\times10^{-15}$, or 90% upper limit of a branching ratio of $7\\times 10^{-15}$, which is a factor of 100 improvement over the existing limit. The expected number of background events is 0.032. To achieve the target sensitivity and background level, the 3.2 kW 8 GeV proton beam from J-PARC will be used. Two types of detectors, CyDet and StrECAL, will be used for detecting the $\\mu$–$e$ conversion events, and for measuring the beam-related background events in view of the Phase-II experiment, respectively. Results from simulation on signal and background estimations are also described.

Hyper-Kamiokande consists of two identical water-Cherenkov detectors of total 520 kt, with the first one in Japan at 295 km from the J-PARC neutrino beam with 2.5$^\\circ$ off-axis angles (OAAs), and the second one possibly in Korea at a later stage. Having the second detector in Korea would benefit almost all areas of neutrino oscillation physics, mainly due to longer baselines. There are several candidate sites in Korea with baselines of 1000–1300 km and OAAs of 1$^\\circ$–3$^\\circ$. We conducted sensitivity studies on neutrino oscillation physics for a second detector, either in Japan (JD $\\times$ 2) or Korea (JD + KD), and compared the results with a single detector in Japan. Leptonic charge–parity (CP) symmetry violation sensitivity is improved, especially when the CP is non-maximally violated. The larger matter effect at Korean candidate sites significantly enhances sensitivities to non-standard interactions of neutrinos and mass ordering determination. Current studies indicate the best sensitivity is obtained at Mt. Bisul (1088 km baseline, $1.3^\\circ$ OAA). Thanks to a larger (1000 m) overburden than the first detector site, clear improvements to sensitivities for solar and supernova relic neutrino searches are expected.