Charged Beams Research Articles

Attosecond Pulses from Ionization Injection Wakefield Accelerators

High-quality ionization injection methods for wakefield acceleration driven by lasers or charged beams (LWFA/PWFA) can be optimized so as to generate high-brightness electron beams with tuneable duration in the attosecond range. We present a model of the minimum bunch duration obtainable with low-emittance ionization injection schemes by spotting the roles of the ionization pulse duration, of the wakefield longitudinal shape and of the delay of the ionization pulse position with respect to the node of the accelerating field. The model is tested for the resonant multi-pulse ionization injection (ReMPI) scheme, showing that bunches having a length of about 300 as can be obtained with an ionization pulse having a duration of 30 fs FWHM.

Monitoring beam charge during FLASH irradiations

In recent years, FLASH irradiation has attracted significant interest in radiation research. Studies have shown that irradiation at ultra-high dose rates (FLASH) reduces the severity of toxicities in normal tissues compared to irradiation at conventional dose rates (CONV), as currently used in clinical practice. Most pre-clinical work is currently carried out using charged particle beams and the beam charge monitor described here is relevant to such beams. Any biological effect comparisons between FLASH and CONV irradiations rely on measurement of tissue dose. While well-established approaches can be used to monitor, in real time, the dose delivered during CONV irradiations, monitoring FLASH doses is not so straightforward. Recently the use of non-intercepting beam current transformers (BCTs) has been proposed for FLASH work. Such BCTs have been used for decades in numerous accelerator installations to monitor temporal and intensity beam profiles. In order to serve as monitoring dosimeters, the BCT output current must be integrated, using electronic circuitry or using software integration following signal digitisation. While sensitive enough for FLASH irradiation, where few intense pulses deliver the requisite dose, the inherent insensitivity of BCTs and the need for a wide detection bandwidth makes them less suitable for use during CONV “reference” irradiations. The purpose of this article is to remind the FLASH community of a different mode of BCT operation: direct monitoring of charge, rather than current, achieved by loading the BCT capacitively rather than resistively. The resulting resonant operation achieves very high sensitivities, enabling straightforward monitoring of output during both CONV and FLASH regimes. Historically, such inductive charge monitors have been used for single pulse work; however, a straightforward circuit modification allows selective resonance damping when repetitive pulsing is used, as during FLASH and CONV irradiations. Practical means of achieving this are presented, as are construction and signal processing details. Finally, results are presented showing the beneficial behaviour of the BCT versus an (Advanced Markus) ionisation chamber for measurements over a dose rate range, from <0.1 Gys−1 to >3 kGys−1.

Laser Plasma‐Accelerated Ultra‐Intense Electron Beam for Efficiently Exciting Nuclear Isomers

AbstractUtilizing a laser plasma wakefield to accelerate ultrahigh charge and current electron beams is critical for many pioneering applications, for example, to efficiently produce nuclear isomers with short lifetimes that may be widely used. However, because of the beam loading effect, the electron charge in a single plasma bubble is limited to hundreds of picocoulombs. Herein, via a tightly focused intense laser pulse self‐guiding in dense gas, a twenty‐nanocoulomb, tens‐of‐MeV, hundred‐kiloampere collimated electron beam is produced from a chain of plasma bubbles in the saturated injection regime. This intense electron beam is utilized to excite indium nuclear isomers with an ultrahigh peak rate of particles·s‐1 via photonuclear reaction. This efficient isomer production method can be widely used for pumping isotopes with excited state lifetimes on the picosecond scale, which is beneficial for deeply understanding nuclear transition mechanisms or stimulating γ‐ray lasers.

Status and future plans for C3 R&D

C3 is an opportunity to realize an e + e - collider for the study of the Higgs boson at √s = 250 GeV, with a well defined upgrade path to 550 GeV while staying on the same short facility footprint [2,3]. C3 is based on a fundamentally new approach to normal conducting linear accelerators that achieves both high gradient and high efficiency at relatively low cost. Given the advanced state of linear collider designs, the key system that requires technical maturation for C3 is the main linac. This paper presents the staged approach towards a facility to demonstrate C3 technology with both Direct (source and main linac) and Parallel (beam delivery, damping ring, ancillary component) R&D.The primary goal of the C3 Demonstration R&D Plan is to reduce technical and cost risk by building and operating the key components of C3 at an adequate scale. This R&D plan starts with the engineering design, and demonstration of one cryomodule and will culminate in the construction of a 3 cryomodule linac with pre-production prototypes. This R&D program would also demonstrate the linac rf fundamentals including achievable gradient and gradient stability over a full electron bunch train and breakdown rates. It will also investigate beam dynamics including energy spread, wakefields, and emittance growth. This work will be critical to confirm the suitability of the C3 beam parameters for the physics reach and detector performance in preparation for a Conceptual Design Report (CDR), as well as for follow-on technology development and industrialization.The C3 Demonstration R&D Plan will open up significant new scientific and technical opportunities based on development of high-gradient and high-efficiency accelerator technology. It will push this technology to operate both at the GeV scale and mature the technology to be reliable and provide high-brightness electron beams.The timeline for progressing with C3 technology development will be governed by practical limitations on both the technical progress and resource availability. It consists of four stages: Stage 0) Ongoing fundamental R&D on structure prototypes, damping and vibrations. Stage 1) Advancing the engineering maturity of the design and developing start-to-end simulations including space-charge and wakefield effects. This stage will include testing of strucutres operating at cryogenic temperatures. Beam tests would be performed with high beam current to test full beam loading. Stage 2) Production and testing of the first cryomodule at cryogenic temperatures. This would provide sufficient experimental data to compile a CDR and it is anticipated for Stage 2 to last 3 years and to culminate with the transport of photo-electrons through the first cryomodule. Stage 3) Updates to the engineering design of the cryomodules, production of the second and third cryomodule and their installation. Lower charge and lower emittance beams will be used to investigate emittance growth. The successful full demonstration of the 3 cryomodules to deliver up to a 3 GeV beam and achieve the C3five gradient will allow a comprehensive and robust evaluation of the technical design of C3 as well as mitigate technical, schedule, and cost risks required to proceed with a Technical Design Report (TDR).

Influence of gas pressure and gas type on pseudospark electron beam

Pseudospark discharge is a discharge that occurs in the left band of the Paschen curve. According to previous studies, an electron beam will be generated in the initial stage of pseudospark discharge. This electron beam has the advantages of high energy, high current and self-confinement. It has a promising application in high-power microwave sources, surface treatment of metal materials, etc. To investigate the characteristics of this electron beam, a pseudospark discharge experimental platform is established in this paper. A pseudospark chamber is designed for pseudospark discharge. To trigger the discharge, a high voltage pulse trigger signal is generated by an avalanche transistor Marx circuit and a trigger unit is designed to generate trigger electrons. Faraday Cup is utilized to collect the electron beam and measure the electron waveform. In order to quantitatively characterize the electron beam, we define six electron beam characteristics, including trigger delay, peak current, electron beam charge, electron beam width, electron beam loop current ratio and electron beam loop charge ratio. To investigate the influence of gas pressure and gas type on electron beam characteristics, we experimentally obtained results of electron beam characteristics for different gas pressures and gas type. We mainly investigated the change rule of the electron beam characteristics when the gas pressure changes between 6 Pa and 20 Pa and the similarities and differences of the electron beams under the two gas environments, argon and nitrogen. We find that gas pressure can be used for the modulation of electron beam time delay. The width of the electron beam in the case of nitrogen has a very stable relationship with the gas pressure. Gas pressure and gas type are two important means of controlling the characteristics of pseudospark electron beams.

High-defined and size-selective deposition of nanoparticles by their manipulation in an electrostatic field

This study combines numerical simulation with an experimental investigation of high-level designed nanostructured surfaces built from metal nanoparticles (NPs). The ultimate goal of this research is to prepare highly designed isotropic surfaces with high purity, defined size, homogeneous surface coverage, and high deposition rate, i.e., the properties appreciated e.g., in precise nanoengineering of microsensors and/or nanoelectronics, etc. The approach is based on manipulation of electrically charged nanoparticles, produced by a gas aggregation cluster source (GAS), in the electrostatic field propagated by two parallel electrodes mounted at the GAS output orifice. The model derived by numerical simulation enables prediction of the distribution and properties of the NPs across the (x, y) substrate plane as a function of the electrical potential superimposed by the charged NPs in the volume and the external electrical field. A good qualitative agreement was found between the model and the properties of GAS-deposited NPs onto the Si substrate (the deposited surface was analyzed by the atomic force microscopy (AFM) imaging), which reveals the electrostatic manipulation of the charged NPs beam as a promising tool for deposition of highly tailored nanostructures.

Performance of the CMS High Granularity Calorimeter prototype to charged pion beams of 20–300 GeV/c

The upgrade of the CMS experiment for the high luminosity operation of the LHC comprises the replacement of the current endcap calorimeter by a high granularity sampling calorimeter (HGCAL). The electromagnetic section of the HGCAL is based on silicon sensors interspersed between lead and copper (or copper tungsten) absorbers. The hadronic section uses layers of stainless steel as an absorbing medium and silicon sensors as an active medium in the regions of high radiation exposure, and scintillator tiles directly read out by silicon photomultipliers in the remaining regions. As part of the development of the detector and its readout electronic components, a section of a silicon-based HGCAL prototype detector along with a section of the CALICE AHCAL prototype was exposed to muons, electrons and charged pions in beam test experiments at the H2 beamline at the CERN SPS in October 2018. The AHCAL uses the same technology as foreseen for the HGCAL but with much finer longitudinal segmentation. The performance of the calorimeters in terms of energy response and resolution, longitudinal and transverse shower profiles is studied using negatively charged pions, and is compared to GEANT4 predictions. This is the first report summarizing results of hadronic showers measured by the HGCAL prototype using beam test data.

The (1+1)-dimensional nonlinear ion acoustic waves in multicomponent plasma containing kappa electrons

Large amplitude (1+1)-dimensional nonlinear ion acoustic waves are theoretically studied in multicomponent plasma consisting of positively charged ions and negatively charged ions, ion beam, kappa-distributed electrons, and dust grains, respectively. By using the Sagdeev potential method, the dynamical system and the Sagdeev potential function are obtained. The important influences of system parameters on the phase diagram of this system are investigated. It is found that the linear waves, the nonlinear waves and the solitary waves are coexistent in the multicomponent plasma system. Meanwhile, the variations of Sagdeev potential with parameter can also be obtained. Finally, it seems that the propagating characteristics of (1+1)-dimensional nonlinear ion acoustic solitary waves and ion acoustic nonlinear shock wave can be influenced by different parameters of this system.

Single-shot emittance measurement and optimization of a hybrid photo-cathode gun beam

A unique hybrid photo-cathode S-band gun accelerator is in operation at Ariel University. The accelerator produces an ultra-fast relativistic electron beam with beam characteristics of 6 MeV kinetic energy, 30 pC charge, and 150 fs pulse duration. In this paper, we present a compact transverse emittance measurement system using the multi-slit mask technique. The system is calibrated using a fully automatic calibration routine, and the results are obtained instantaneously. To find the optimal parameters required to obtain the lowest transverse emittance value, we scan the currents in the focusing coils surrounding the gun including a bucking coil current scan to minimize the magnetic field upon the photo-cathode. In the last step, we verify the relation between transverse emittance and electron beam charge in RF guns emitted from a photo-cathode. The verification is done by a beam charge scan.

Experimental characterization of gaseous ion beams produced with the advanced ion source for hadrontherapy (AISHa) at 18 GHz

Experimental characterization of gaseous ion beams produced with the advanced ion source for hadrontherapy (AISHa) at 18 GHz

Recent progress of ISOL facility at RAON

The RAON (Rare Isotope Accelerator complex for ON-line experiments) is currently in the stage of commissioning under the Rare Isotope Science Project (RISP) launched in 2011. RAON will utilize an advanced rare isotope beams produced with a high power target by the Isotope Separation On-Line (ISOL) facility, aiming to deliver high purity and intense, neutron-rich rare isotope beams to the post-accelerator and experimental facilities. The RAON ISOL facility consists of a target/ion source module surrounded by movable shielding blocks in a bunker, remote handling facilities for the target operation, a pre-mass separator, a RFQ cooler buncher, an EBIS charge breeder, and an A/q separator. The installation and alignment of the ISOL facility were completed in June 2021. The target/ion source module allows us to bombard a thick target with a 70 MeV proton beam of RAON, producing a variety of rare isotope beams. Rare isotope beams extracted from the target/ion source can be transported to a pre-mass separator at energies of up to 60 keV, and will be cooled in a RFQ-CB. Cooled ion beams can be sent to two different experimental facilities, such as a Mass Measurement System and a Collinear Laser Spectroscopy in ISOL experimental hall. Alternatively, for post-acceleration of ion beams, the singly charged ion beam of interest can be bunched to 108 ions in RFQ-CB and then delivered to the EBIS charge breeder through the EBIS branch system. The preparation of multi charged ion beams for the post-acceleration using the superconducting LINAC of SCL3 will be carried out through the EBIS charge breeder and A/q separator to match the energy of 10 keV/u with A/q < 6 with the requirement of RAON Injector.The first commissioning experiment of the ISOL system started in March 2021 using the 133Cs and 120Sn stable beams produced from the target container combined with the surface ion source and laser Ion source. The stable beam experiments have demonstrated the overall functioning of the RAON ISOL system, and we are planning to carry out the first RI beam test using the SiC target with 70 MeV proton of cyclotron in the coming months.

Transmission electron microscopy studies of organic–inorganic hybrid perovskites: Advances, challenges, and prospects

In the last few years, organic–inorganic hybrid perovskites (OIHPs) have attracted immense research and industry attention for their application as light absorbers in solar cells and light-emitting diodes. Characterizing OIHP materials and optoelectronic devices using transmission electron microscopy (TEM)-based techniques has played a large role in understanding their structural, compositional, and electronic properties. However, the highly energetic and electrically charged electron beam radiation used in TEM can result in damage to the pristine structure, as OIHPs are unstable and highly sensitive to electron beams. This damage potentially obscures intrinsic information and leads to a serious misunderstanding of the microscopic structure–property–performance relationship for OIHP optoelectronic devices. To address this issue, we first review the electron and ion beam-induced degradation mechanism of OIHPs, followed by a review of the development of ultra-low-dose TEM techniques that can able to minimize this damage, thus can able to obtain reliable, intrinsic structural information about OIHPs from the atomic to micrometer length scales. Finally, we suggest a protocol for appropriate TEM specimen preparation and characterization techniques. This protocol can help ensure that future TEM studies of OIHPs give reliable information, thereby enabling a deeper understanding and optimization of the performance and long-term stability of OIHP optoelectronic devices.

Comparison among possible design solutions for the Stray Field Shielding System of the DTT Neutral Beam Injector

Within the effort on the conceptual design of the Divertor Test Tokamak (DTT) Neutral Beam Injector (NBI), the design of the Stray Field Shielding System (SFSS) for DTT NBI is under development, to suppress the potentially harmful effects of the stray poloidal field from the tokamak on the accelerated charged beam. Various possible design solutions to solve this problem are presented and compared, with a particular focus on the stray field minimization procedure and particle tracing simulations, used during the design validation phase with the objective of maximizing beamline performances.

Identification and reconstruction of low-energy electrons in the ProtoDUNE-SP detector

Measurements of electrons from νe interactions are crucial for the Deep Underground Neutrino Experiment (DUNE) neutrino oscillation program, as well as searches for physics beyond the standard model, supernova neutrino detection, and solar neutrino measurements. This article describes the selection and reconstruction of low-energy (Michel) electrons in the ProtoDUNE-SP detector. ProtoDUNE-SP is one of the prototypes for the DUNE far detector, built and operated at CERN as a charged particle test beam experiment. A sample of low-energy electrons produced by the decay of cosmic muons is selected with a purity of 95%. This sample is used to calibrate the low-energy electron energy scale with two techniques. An electron energy calibration based on a cosmic ray muon sample uses calibration constants derived from measured and simulated cosmic ray muon events. Another calibration technique makes use of the theoretically well-understood Michel electron energy spectrum to convert reconstructed charge to electron energy. In addition, the effects of detector response to low-energy electron energy scale and its resolution including readout electronics threshold effects are quantified. Finally, the relation between the theoretical and reconstructed low-energy electron energy spectra is derived, and the energy resolution is characterized. The low-energy electron selection presented here accounts for about 75% of the total electron deposited energy. After the addition of lost energy using a Monte Carlo simulation, the energy resolution improves from about 40% to 25% at 50 MeV. These results are used to validate the expected capabilities of the DUNE far detector to reconstruct low-energy electrons.3 MoreReceived 3 November 2022Accepted 27 April 2023DOI:https://doi.org/10.1103/PhysRevD.107.092012Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasParticle interactionsPhysical SystemsElectronsLeptonsMuonsNeutrinosPositronsTechniquesMonte Carlo methodsNeutrino detectorsParticle acceleratorsParticle data analysisParticle decaysParticle detectorsParticles & Fields

Generation of a Chirp-Controlled Terahertz Pulse by a Tapered Corrugated Wakefield Structure

Terahertz pulses with controlled spectral-temporal waveform have great potential in expanding the scope of state-of-the-art terahertz researches, such as terahertz-driven resonant and nonresonant control over matter and light, ultrafast terahertz spectroscopy, and terahertz-driven acceleration. Here, we propose and demonstrate a method to generate a prescribed terahertz chirped waveform with a well-designed tapered corrugated wakefield structure. We develop a deterministic procedure to derive the parameters of the corrugated structure that generates the desired spectral-temporal waveform with certain shape of chirp, central frequency, bandwidth, and pulse duration. The experimental results from ultrashort electron bunches passing through a well-designed tapered corrugated structure are demonstrated. Time-frequency analysis of the terahertz electric field measured by electro-optical sampling shows clear chirp from 0.38 to 0.6 THz. Calibrated measurements of the radiated energy indicate 10 \textmu{}J per pulse for an incident beam charge of 300 pC.

Swelling modification by electron beam at chalcopyrite copper indium gallium diselenium thin-film controlled optical features

Electron beam effect on swelling at the sol-gel derived thin film has been examined for chalcopyrite copper indium gallium diselenium thin-film semiconductor nanolayers with optical pransparent features. The copper indium gallium diselenium layers with the optical transparent features were irradiated by negatively charged electron beam which was emmited from Sr-90 radioisotope with 2.86 mCi activity. The swelling was the important parameters to use this thin film at the optoelectronic layers that have affected the safety and operating life of the equipments and systems in nuclear applications.

Adaptive Wireless Power Transfer via Resonant Laser Beam Over Large Dynamic Range

Wireless power transfer (WPT) via resonant laser beam from a spatially-distributed laser resonator not only benefits the instinct safety, but also has important potential of adaptive operation without positioning and aiming when retroreflectors are used to enable the alignment-free operation of the laser. Despite the intense theoretical modeling and experimental efforts with different laser schemes, the adaptive resonant beam WPT across large dynamic range -including both working distance and field of view (FoV) -has never been demonstrated, due to the absence of true alignment-free laser. In this work, we summarized the requirements on the dynamic range and discussed the optimization criteria of dynamic range and laser safety, including the telescope in the laser resonator, the resonator stability, coupled-resonator scheme, and influences of the optical aberrations. The analysis indicated that loss induced by optical aberrations is the main issue limits the dynamic range. In the experiment, alignment-free laser with large dynamic range for WPT application was demonstrated with improved resonator design and optical design to compensate the aberrations. Efficient multiwatt optical output was obtained across a working distance of 1-5 m, a receiver FoV of ±30∘, and a transmitter FoV of 4.6∘; and over 1.3 W electrical output was obtained via an InGaAs photovoltaic cell, with DC-DC WPT efficiency being 4%. Our work proved the feasibility of large-dynamic-range alignment-free laser with distributed-resonator, which paves the way for practical resonant beam charging and communication applications based on it for the internet of things devices.

Deflected beam method for absolute current density determination

We present a broadly applicable in situ method for profiling ion beams using electrostatic deflectors and a Faraday cup. By deconvolving the detector geometry from the resulting current profiles, spatially resolved absolute current density profiles are obtained. We demonstrate this method’s efficacy with low-density highly charged ion beams (specifically, Ne8+). Details on experimental design are provided as well as the link to the deconvolution routine on GitHub.

Unraveling Li growth kinetics in solid electrolytes due to electron beam charging.

Revealing the local structure of solid electrolytes (SEs) with electron microscopy is critical for the fundamental understanding of the performance of solid-state batteries (SSBs). However, the intrinsic structural information in the SSB can be misleading if the sample's interactions with the electron beams are not fully understood. In this work, we systematically investigate the effect of electron beams on Al-doped lithium lanthanum zirconium oxide (LLZO) under different imaging conditions. Li metal is observed to grow directly on the clean surface of LLZO. The Li metal growth kinetics and the morphology obtained are found to be heavily influenced by the temperature, accelerating voltage, and electron beam intensity. We prove that the lithium growth is due to the LLZO delithiation activated by a positive charging effect under electron beam emission. Our results deepen the understanding of the electron beam impact on SEs and provide guidance for battery material characterization using electron microscopy.

3D beam-envelope approach for an asymmetric beam in a high intensity linac with a solenoid channel

Presented here is a theory model based on the beam-envelope approach to determine the global behavior of a charged beam propagating through a high intensity linac with a solenoid channel, namely, the orbital evolution of the root-mean-square beam size in the transverse and longitudinal direction. The model is applied to the Gaussian particle distribution, where the motion of an individual particle is governed by linear focusing/defocusing forces in the solenoid channel and RF fields, except for space-charge forces. In this model, highly nonlinear effects that originated from space-charge forces disappear by averaging over the harmonic motions such as the betatron motion and phase motion in the moving direction and the Gaussian distribution. All particles making up a 3D Gaussian bunch obey the same linear equations of motion where all information of nonlinearity in the space-charge forces and the particle distribution are carried in. The theory is validated using Gaussian macro-particle simulation and one of the widely used photonic integrated circuit codes, TraceWin. As an example, the model is applied to the case of an international fusion materials irradiation facility superconducting linac with solenoid guiding and half wave RF acceleration. The results are compared with results obtained by this model and other two approaches.