TeV/m catapult acceleration of electrons in graphene layers (vol 13, 1330, 2023)

The original version of this Article contained an error in the legend of Figure 1. “Overview of the catapult electron acceleration scheme in graphene layers. Moving from left to right, as indicated by the blue arrows, a single 3 fs-long laser pulse of 100 nm wavelength and 1021 W/cm2 peak intensity, ionizes a 1.5 μm-long (y) and 1.2 μm-thick (x) stack of graphene layers. The interaction results in self-injected electrons being accelerated to ≃ 7 MeV. The image is at scale, with a 150 nm bar drawn, and for better visibility, only 15 out of 60 graphene layers are shown. The simulated normalized transverse electric field (Ex) is shown as a surface colour plot for the same laser pulse before entering the target (left) and after leaving the target (right). This work contains 2D PIC simulations carried out in the yx-plane indicated in the image.” now reads: “Overview of the catapult electron acceleration scheme in graphene layers. Moving from left to right, as indicated by the blue arrows, a single 3 fs-long laser pulse of 100 nm wavelength and 1021 W/cm2 peak intensity, ionizes a 1.5 μm-long (y) and 1.2 μm-thick (x) stack of graphene layers. The interaction results in self-injected electrons being accelerated to ≃ 7 MeV. The image is at scale, and for better visibility, only 15 out of 60 graphene layers are shown. The simulated normalized transverse electric field (Ex) is shown as a surface colour plot for the same laser pulse before entering the target (left) and after leaving the target (right). This work contains 2D PIC simulations carried out in the yx-plane indicated in the image.” The original Article has been corrected

Noninvasive 3D Field Mapping of Complex Static Electric Fields

Many upcoming experiments in antimatter research require low-energy antiproton beams. With a kinetic energy in the order of 100 keV, the standard magnetic components to control and focus the beams become less effective. Therefore, electrostatic components are being developed and installed in transfer lines and storage rings. However, there is no equipment available to precisely map and check the electric field generated by these elements. Instead, one has to trust in simulations and, therefore, depend on tight fabrication tolerances. Here we present, for the first time, a noninvasive way to experimentally probe the electrostatic field in a 3D volume with a microsensor. Using the example of an electrostatic quadrupole focusing component, we find excellent agreement between a simulated and real field. Furthermore, it is shown that the spatial resolution of the probe is limited by the electric field curvature which is almost zero for the quadrupole. With a sensor resolution of 61V/m/√Hz, the field deviation due to a noncompliance with the tolerances can be resolved. We anticipate that this compact and practical field strength probe will be relevant also for other scientific and technological disciplines such as atmospheric electricity or safeguarding near power infrastructure

Measurement of the muon flux from 400 GeV/c protons interacting in a thick molybdenum/tungsten target

The SHiP experiment is proposed to search for very weakly interacting particles beyond the Standard Model which are produced in a 400 GeV/c proton beam dump at the CERN SPS. About 1011 muons per spill will be produced in the dump. To design the experiment such that the muon-induced background is minimized, a precise knowledge of the muon spectrum is required. To validate the muon flux generated by our Pythia and GEANT4 based Monte Carlo simulation (FairShip), we have measured the muon flux emanating from a SHiP-like target at the SPS. This target, consisting of 13 interaction lengths of slabs of molybdenum and tungsten, followed by a 2.4 m iron hadron absorber was placed in the H4 400 GeV/c proton beam line. To identify muons and to measure the momentum spectrum, a spectrometer instrumented with drift tubes and a muon tagger were used. During a 3-week period a dataset for analysis corresponding to (3.27±0.07) × 1011 protons on target was recorded. This amounts to approximatively 1% of a SHiP spill

Track reconstruction and matching between emulsion and silicon pixel detectors for the SHiP-charm experiment

In July 2018 an optimization run for the proposed charm cross section measurement for SHiP was performed at the CERN SPS. A heavy, moving target instrumented with nuclear emulsion films followed by a silicon pixel tracker was installed in front of the Goliath magnet at the H4 proton beam-line. Behind the magnet, scintillating-fibre, drift-tube and RPC detectors were placed. The purpose of this run was to validate the measurement's feasibility, to develop the required analysis tools and fine-tune the detector layout. In this paper, we present the track reconstruction in the pixel tracker and the track matching with the moving emulsion detector. The pixel detector performed as expected and it is shown that, after proper alignment, a vertex matching rate of 87% is achieved

Design and Beam Dynamics Studies of a Novel Compact Recoil Separator Ring for Nuclear Research with Radioactive Beams

The recent development of radioactive beam facilities has significantly expanded the capabilities for investigating the structure of the atomic nucleus and the nuclear interaction. For instance, the HIE-ISOLDE facility at CERN delivers presently the largest range of low-energy radioactive beam available worldwide. This energy range is ideal for the study of nuclear structure, low-energy dynamics and astrophysics by using nucleon transfer, Coulomb excitation and deep inelastic reactions. All these studies require an efficient and high-resolution recoil separator for the clear identification of medium and large mass reaction fragments. To meet these needs, we propose a versatile recoil separator for radioisotopes based on a compact storage ring, the Isolde Superconducting Recoil Separator (ISRS) formed of superconducting combined-function nested magnets with both, bending and focusing/defocusing functions. The ISRS is designed to operate in high momentum acceptance and isochronous modes. In this paper, we present the optics design and detailed beam dynamics studies for the performance characterisation

3D Tracking Methods in a GEANT4 Environment Through Electrostatic Beamlines

Due to the relatively infrequent use of electrostatic beamline elements compared with their magnetic counterparts, there are few particle tracking codes which allow for the straightforward implementation of such beamlines. In this contribution, we present 3D tracking methods for beamlines containing electrostatic elements utilising a modified version of the Geant4 based tracking code 'G4beamline'. In 2020 transfer lines will begin transporting extremely low energy (100 keV) antiproton beams from the Extra Low Energy Antiproton (ELENA) ring to the antimatter experiments at CERN. Electrostatic bending and focusing elements have been chosen for the beamlines due to their mass independence and focusing efficiency in the low energy regime. These beamlines form the basis of our model which is benchmarked against simplified tracking simulations. Realistic beam distributions obtained via tracking around ELENA in the presence of collective effects and electron cooling will be propagated along the optimised 3D transfer model to achieve the best beam quality possible for the experiments

Beam Tracking Studies of Electron Cooling in ELENA

The Extra Low ENergy Antiproton storage ring (ELENA), which is currently being commissioned at CERN, will further decelerate antiprotons extracted from the Antiproton Decelerator (AD) from 5.3 MeV to energies as low as 100 keV. It will provide high quality beams for the antimatter experiments located within the AD hall. At such low energies, it is important to correctly evaluate the long term beam stability. To provide a consistent explanation of the different physical phenomena affecting the beam, tracking simulations have been performed and the results will be presented in this contribution. These include electron cooling and various scattering effects under realistic conditions. The effects of several imperfections in the electron cooling process will also be discussed. In addition, analytical approximations of the temporal variation of emittance under these conditions will be presented, and compared with numerical simulation results

Low-Energy Negative Ion Injection Beamline for Experiments with Antiprotonic Atoms at AEgIS

Interaction of low-energy antiprotons with nuclear targets provided fundamental knowledge about proton and neutron densities of many nuclei through the capture process, cascade on lower electron orbits, and annihilation with the nucleon. The expelled electrons produce X-rays and with the recoil particles after annihilation, thus, a sufficient amount of information can be obtained about this interaction. However, all previous experiments were done via formation of antiprotonic atoms in solid or gaseous targets. Therefore, annihilation occurs prior reaching the S or P orbital levels and precise measurements are missing. Recently, AEgIS collaboration proposed a conceptually new experimental scheme. The creation of cold antiprotonic atoms in a vacuum guarantees the absence of the Stark effect. And with the sub-ns timing and synchronization, the previous experimental obstacles would be resolved. This will allow studying atomic properties, evolution, and fragmentation process with improved precision and extended lifetimes. In this contribution, we present an overview of the experimental scheme as well as various aspects of negative ion injection beamline into the AEgIS experiment

Driver-witness configuration in CNT array-based acceleration

Solid-state plasma wakefield acceleration might be an alternative to accelerate particles with ultra-high accelerating gradients, in the order of TV/m.In addition, due to their thermodynamic properties, 2D carbon-based materials, such as graphene layers and/or carbon nanotubes (CNT) are good candidates to be used as the media to sustain such ultra-high gradients. In particular, due to their cylindrical symmetry, multi-nm-aperture targets, made of CNT bundles or arrays may facilitate particle channelling through the crystalline structure.In this work, a two-bunch, driver-and-witness configuration is proposed to demonstrate the potential to achieve particle acceleration as the bunches propagate along a CNT-array structure.Particle-in-cell simulations have been performed using the VSIM code in a 2D Cartesian geometry to study the acceleration of the second (witness) bunch caused by the wakefield driven by the first (driver) bunch.The effective plasma-density approach was adopted to estimate the wakefield wavelength, which was used to identify the ideal separation between the two bunches, aiming to optimize the witness-bunch acceleration and focusing.Simulation results show the high acceleration gradient obtained, and the energy transfer from the driver to the witness bunch