Beam-target Interaction Research Articles

4D Track Reconstruction on Free-Streaming Data with PANDA at FAIR

A new generation of accelerator-based experiments in subatomic physics is being developed, where the challenge of separating rare signal processes from background at high intensities requires a change of trigger paradigm. At the future PANDA experiment at FAIR, hardware triggers will be abandoned and instead a purely software-based system will be used. This requires novel reconstruction methods with the ability to process data from many beam–target interactions simultaneously. A 4D tracking algorithm, based on the cellular automaton, has been developed which will utilize the timing information from detector signals. Simulation studies have been performed to test its performance on the foreseen free-streaming, i.e., continuous readout from the PANDA detector, where all processing is on the software level. For this purpose, a novel quality assurance method, tailored for tracking on free-streaming data has been developed and implemented. Benchmark studies on PANDA software show that at higher interaction rates, 4D tracking performs better than the 3D algorithm in terms of efficiency, 84%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\%$$\\end{document} compared to 77%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\%$$\\end{document}. In addition, the fake track suppression is greatly improved, reducing the rate of fake tracks of “ghosts” by about 50%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\%$$\\end{document}.

Functional characterization of modules for the Silicon Tracking System of the CBM experiment

The CBM experiment is a fixed-target heavy-ion physics experiment at the future FAIR facility, designed to explore the QCD phase diagram at high baryon-net densities and moderate temperatures. To address its complex physics program, the experiment is conceived to operate at beam–target interaction rates up to 10 MHz with self-triggered front-end electronics and free-streaming readout architecture. The Silicon Tracking System (STS) of CBM is the main charged-particle tracker, capable of delivering time-stamped hits for online tracking and event building, and momentum measurement inside a superconducting dipole magnet. The functional unit of the STS is the detector module, a device assembled from a double-sided silicon microstrip sensor connected via a stack of microcables to a pair of front-end boards carrying the readout electronics. The assembly and successful operation of STS modules, produced with close-to-final components, was an important milestone achieved in recent years. The systematic study of the modules’ performance is also necessary for optimizing the assembly procedure and ensuring high production yield. This work reports a series of tests, which aim to evaluate the module’s operation and establish the basic criteria for quality control. It summarizes the procedures and results of different measurements performed with the modules, starting with noise estimation and charge amplitude calibration, resulting in the linearization of the channel’s ADC and a homogeneous threshold distribution. Those results were verified using a radioactive source. Additionally, first conclusions concerning the assembly yield in terms of number of functional channels were obtained. These studies represent a fundamental step towards the series production readiness for the final STS detector.

Efficient generation of collimated multi-GeV gamma-rays along solid surfaces

Bright γ -ray sources are of great significance for fundamental research, medicine, and industry. However, γ -ray production by bremsstrahlung, Compton scattering, and synchrotron radiation is often subjected to large divergence, wide size, and/or low efficiency, making it difficult to achieve high-brightness γ -ray sources. Here, we have found an efficient mechanism to generate γ -rays with, to our knowledge, unprecedented brilliance by use of an ultrarelativistic electron beam with nC charge incident onto a solid surface at grazing incidence. With this interaction configuration, extreme high quasistatic magnetic fields up to the gigagauss level or effective electric fields up to 10 14 V / m are induced by the background electron backflows at the target surface. Subsequently, the electron beam is strongly focused by such fields by over an order of magnitude to submicrometer diameter, and its density is increased beyond the solid density; the induced effective fields are high enough to trigger quantum electrodynamics (QED) effects. These result in the production of extremely brilliant dense γ -ray beams with photon energy reaching multi-GeV, where the electron-to-photon energy conversion efficiency can exceed 60%. This offers a promising route to push the beam–target interaction to the QED regime, leading to ultrabright γ -ray sources for various applications.

Detection and discrimination of neutron capture events for NCEPT dose quantification

Neutron Capture Enhanced Particle Therapy (NCEPT) boosts the effectiveness of particle therapy by capturing thermal neutrons produced by beam-target nuclear interactions in and around the treatment site, using tumour-specific ^{10}B or ^{157}Gd-based neutron capture agents. Neutron captures release high-LET secondary particles together with gamma photons with energies of 478 keV or one of several energies up to 7.94 MeV, for ^{10}B and ^{157}Gd, respectively. A key requirement for NCEPT’s translation is the development of in vivo dosimetry techniques which can measure both the direct ion dose and the dose due to neutron capture. In this work, we report signatures which can be used to discriminate between photons resulting from neutron capture and those originating from other processes. A Geant4 Monte Carlo simulation study into timing and energy thresholds for discrimination of prompt gamma photons resulting from thermal neutron capture during NCEPT was conducted. Three simulated 300times 300times 300 mm^3 cubic PMMA targets were irradiated by ^4He or ^{12}C ion beams with a spread out Bragg peak (SOBP) depth range of 60 mm; one target is homogeneous while the others include 10times 10times 10 mm^3 neutron capture inserts (NCIs) of pure ^{10}B or ^{157}Gd located at the distal edge of the SOBP. The arrival times of photons and neutrons entering a simulated 50times 50times 50 mm^3 ideal detector were recorded. A temporal mask of 50–60 ns was found to be optimal for maximising the discrimination of the photons resulting from the neutron capture by boron and gadolinium. A range of candidate detector and thermal neutron shielding materials were simulated, and detections meeting the proposed acceptance criteria (i.e. falling within the target energy window and arriving 60 ns post beam-off) were classified as true or false positives, depending on their origin. The ratio of true/false positives (R_{TF}) was calculated; for targets with ^{10}B and ^{157}Gd NCIs, the detector materials which resulted in the highest R_{TF} were cadmium-shielded CdTe and boron-shielded LSO, respectively. The optimal irradiation period for both carbon and helium ions was 1 µs for the ^{10}B NCI and 1 ms for the ^{157}Gd NCI.

Effects of Cs+ and Arn+ ion bombardment on the damage of graphite crystals

Intercalation mechanisms and diffusion or segregation phenomena in graphitic materials play a crucial role in different applied science fields. The investigation of such phenomena is usually accomplished through depth profiling experiments. Ar-GCIBs (Argon- Gas Cluster Ion Beams) are commonly adopted for in-depth concentration profiling of organic or soft materials; on the other hand, cesium ions are in general more suitable for the sputtering of inorganics. During such experiments, the beam-target interaction could alter chemistry and structure of the material. In this work, we define the optimal conditions in terms of both sputtering ion source and energy to preserve the crystal features. HOPG was used as a model system to compare morphological, physical, and chemical effects induced by different Arn+ clusters, and ultra-low energy Cs+ beam during ToF-SIMS (Time of Flight Secondary Ion Mass Spectrometry) depth profiling experiments. We demonstrated, through in-situ AFM (Atomic Force Microscopy) analysis, that the monoatomic Cs+ beam alters to a lower extent the HOPG structure. On the contrary, Ar-GCIBs strongly modify the graphite surface basal plane and underlying layers. However, HOPG crystals treated with the cesium monoatomic source undergo a chemistry modification leading to the formation of graphite oxide (GOx) together with the presence of hydrogen, and cesium adducts.

Ultrafast high energy electron lens radiography suitable for transient electromagnetic field diagnosis

Transient electromagnetic fields — during or after laser/particle beam-target interaction — are a significant and hardly explored parameter. This paper proposes a new method for measuring transient electromagnetic fields, based on ultrafast high-energy electron lens radiography, that has a high tolerance for matter in the diagnosed region. With this method, a continuous point strength diagnosis helps to obtain delicate. Furthermore, dual-band diagnosis can be used to determine the field direction. To verify its feasibility, a 50 MeV electron lens radiography beamline was designed and optimized and a preliminary simulation for diagnosing circular magnetic fields ranging from 170 T·μm to 680 T·μm was performed. For a number density of 2000/pixel and ±10% non-uniformity, ±15% diagnostic field strength accuracy has been obtained. The direction diagnosis also works well. Combined with the advantages of high-energy electron beams, ultrafast high-energy electron lens radiography is suitable for transient electromagnetic field diagnosis.

The FOOT experiment: current status and future perspective for nuclear fragmentation studies in particle therapy and space radiation protection

Nuclear fragmentation processes occurring in the beam-target interaction represent a potential source of hazard for humans’ health both in particle therapy and space exploration. The FragmentatiOn Of Target (FOOT) experiment aims to characterize both beam and target fragments, and to measure with great accuracy nuclear fragmentation cross sections interesting in cancer therapy and in long-lasting interplanetary missions. In this paper, the fragments reconstruction capabilities of the FOOT experimental setup is reported. FOOT future perspective of providing useful data to improve the modelling of neutron interactions is also discussed.

Diagnosing the DARHT Electron Beam-Target Interaction and Hydrodynamic Expansion

Diagnosing the DARHT Electron Beam-Target Interaction and Hydrodynamic Expansion

Estimation of neutron and γ-rays flux at the MAGNEX facility via FLUKA simulations

Simulations for estimating the neutron and γ-rays radiation background in the forthcoming NUMEN experiments at the upgraded MAGNEX facility were performed with the simulation package FLUKA. Three main radiation sources were considered in our simulations namely, the beam-target interaction, the moderation of the beam particles inside the beam dump and a hypothetical 10W loss in the beam intensity during the beam transport. In the present contribution, the results of this preliminary analysis are presented and discussed.

Production of pulsed high-energy neutron bursts from beam–target interaction using a 15 MeV HERMES III ion beam

Intense pulsed neutron fluences are generated by a high-energy (>10 MeV) proton beam using the beam-target method on the HERMES III facility at Sandia National Laboratories [J. J. Ramirez et al., in Proceedings of the 7th International Conference on High Power Particle Beams (Kernforschungszentrum, Karlsruhe GmbH, Karlsruhe, Germany, 1988), p. 148]. In order to generate the high-energy proton beam, a radial ion diode previously developed and fielded at the 6-MeV level in negative polarity was extended in performance to the 15-MeV level. This performance increase is described along with the development of a more durable hardware set to withstand the much more potent 15-MeV proton beam. An extensive series of simulations is developed to characterize the neutrons produced by the proton–target interaction. Particle-in-cell simulations describe the electron and ion dynamics, while Monte Carlo simulations characterize the neutron output. Due to differing estimates of proton beam voltage and current between the respective simulations, we make an approximate estimate of 13.5-MeV to 15-MeV and 120-kA ion beams at peak power in a 40 ns FWHM pulse. Simulations indicate that a total of 1.7 × 1013 neutrons are generated into 4π. Comparison of the neutron output predictions with a limited set of neutron flux measurements suggests a flux level of ∼1 × 1010 neutrons/cm2 to 10 × 1010 neutrons/cm2 over an approximately few tens of cm2 area at the relevant application location. This effort also contributes to physics understanding of the use of inductive voltage adder platforms to drive ion-beam diode loads.

Towards the construction of the inner zone of the CBM-TOF wall

The Time-of-Flight (TOF) subsystem, one of the core detectors of the CBM experiment, is dedicated to the identification of all charged hadrons produced in beam-target interaction. The targeted system time resolution of 80 ps and an efficiency above 90% should be maintained at a particle flux up to 30 kHz/cm2 in the region of low polar angles. In order to cope with these challenging requirements, CBM-TOF wall will be equipped with Multi-Gap Resistive Plate Counters with Multi-Strip readout (MSMGRPC).Our R&D activity has been focused on the development of a MSMGRPC prototype for the most demanding region of the CBM-TOF wall, the region of low polar angles (from 2.5° to ∼12° around the beam pipe). The results obtained in heavy ion in-beam tests have demonstrated the performances of the developed prototypes in conditions of exposure of the whole active area to high flux and high multiplicity reaction products. The latest developed prototypes have an optimized design which fulfills simultaneously two important requirements for MSMGRPCs, the granularity for the inner zone of the CBM-TOF subdetector and the impedance matching to the front-end electronics. Based on the obtained in-beam test results and the architecture of the developed prototypes, a modular structure of 12 units called modules is proposed. A total number of 470 MSMGRPCs (~30000 readout channels) assures an uniform coverage of the active area.

Stopping Power and Partial Stopping Power Effective Charge in The Plasma

The energy losses of ions moving in an electron gas can be studied through the stopping power of the medium. A large number of calculations of the stopping power of ions and electrons in plasmas have been carried out using the random phase approximation (RPA) in the dielectric formalism, for low and high energies. Then we calculated the partial stopping power effective charge (PSPEC) from the energy loss of an incident proton, Ar-ion, and He-ion in target plasma. The Brandt-Kitagawa (BK) model is used to describe the projectile charge fraction (q) and calculate the stopping power and PSPEC, which depends on temperature and electron density ρ(k) of the plasma. This is a topic of relevance to understanding the beam-target interaction in the contexts of particle driven fusion. The presented study is formulated in terms of classical dielectric functions. The programming language Fortran - 90 was used for a required calculation. In the present work, three systems of plasma (Z-pinch, Tokamak, ICF) for different temperatures and densities were covered. Additionally, a comparison has been done with the previous work of plasma.

The CLAS12 Forward Time-of-Flight system

The Forward Time-of-Flight system for the large-acceptance CLAS12 spectrometer in Hall B at the Thomas Jefferson National Accelerator Facility is described. The system is positioned at distances in the range from 6.2 m to 7.2 m from the beam–target interaction point and spans laboratory polar angles from 5∘→45∘ and nearly the full azimuth. The system consists of 540 individual scintillation counters with double-ended readout that range in length from 17 cm to 426 cm of discrete widths of 6 cm, 15 cm, and 22 cm, and of discrete thicknesses of 5 cm and 6 cm. The effective counter time resolution for passing charged particles varies from 50 ps for the shortest counters at small angles to 200 ps for the longest counters at large angles. The detectors are part of the forward-angle particle identification system for CLAS12 during offline event reconstruction and are a component of the online data acquisition trigger to select final state event topologies with forward-going charged particles.

Simultaneous Ultra-Fast Imaging and Neutron Emission from a Compact Dense Plasma Focus Fusion Device

Recently, there has been intense interest in small dense plasma focus (DPF) devices for use as pulsed neutron and X-ray sources. Although DPFs have been studied for decades and scaling laws for neutron yield versus system discharge current and energy have been established (Milanese, M. et al., Eur. Phys. J. D 2003, 27, 77–81), there are notable deviations at low energies due to contributions from both thermonuclear and beam-target interactions (Schmidt, A. et al., Phys. Rev. Lett. 2012, 109, 1–4). For low energy DPFs (100 s of Joules), other empirical scaling laws have been found (Bures, B.L. et al., Phys. Plasmas 2012, 112702, 1–9). Although theoretical mechanisms to explain this change have been proposed, the cause of this reduced efficiency is not well understood. A new apparatus with advanced diagnostic capabilities allows us to probe this regime, including variants in which a piston gas is employed. Several complementary diagnostics of the pinch dynamics and resulting X-ray neutron production are employed to understand the underlying mechanisms involved. This apparatus is unique in its employment of a 50 fs laser-based shadowgraphy system that possesses unprecedented spatio-temporal resolution.

Quantifying spot size reduction of a 1.8 kA electron beam for flash radiography

The spot size of Axis-I at the Dual Axis Radiographic Hydrodynamic Test facility was reduced by 15.5% by including a small diameter drift tube that acts to aperture the outer diameter of the electron beam. Comparing the measured values to both analytic calculations and results from a particle-in-cell model shows that one-third to one-half of the spot size reduction is due to a drop in beam emittance. We infer that one-half to two-thirds of the spot-size reduction is due to a reduction in beam-target interactions. Sources of emittance growth and the scaling of the final focal spot size with emittance and solenoid aberrations are also presented.

The Silicon Tracking System of the CBM experiment at FAIR

The Silicon Tracking System (STS) is the central detector in the Compressed Baryonic Matter (CBM) experiment at FAIR. Operating in the 1Tm dipole magnetic field, the STS will enable pile-up free detection and momentum measurement of the charged particles originating from beam-target nuclear interactions at rates up to 10 MHz. The STS consists of 8 tracking stations based on double-sided silicon micro-strip sensors equipped with fast, self-triggering read-out electronics. With about two million read-out channels, the STS will deliver a high-rate stream of time-stamped data that is transferred to a computing farm for on-line event determination and analysis. The functional building block is a detector module consisting of a sensor, micro-cables and two front-end electronics boards. In this contribution, the development status of the STS components and the system integration is discussed and an outlook on the detector construction is given.

Toward high-efficiency and detailed Monte Carlo simulation study of the granular flow spallation target

The dense granular flow spallation target is a new target concept chosen for the Accelerator-Driven Subcritical (ADS) project in China. For the R&D of this kind of target concept, a dedicated Monte Carlo (MC) program named GMT was developed to perform the simulation study of the beam-target interaction. Owing to the complexities of the target geometry, the computational cost of the MC simulation of particle tracks is highly expensive. Thus, improvement of computational efficiency will be essential for the detailed MC simulation studies of the dense granular target. Here we present the special design of the GMT program and its high efficiency performance. In addition, the speedup potential of the GPU-accelerated spallation models is discussed.

High efficiency focus neutron generator

In the present paper, the new idea to increase the neutron yield of plasma focus devices is investigated and the results are presented. Based on many studies, more than 90% of neutrons in plasma focus devices were produced by beam target interactions and only 10% of them were due to thermonuclear reactions. While propounding the new idea, the number of collisions between deuteron ions and deuterium gas atoms were increased remarkably well. The COMSOL Multiphysics 5.2 was used to study the given idea in the known 28 plasma focus devices. In this circumstance, the neutron yield of this system was also obtained and reported. Finally, it was found that in the ENEA device with 1 Hz working frequency, 1.1 × 109 and 1.1 × 1011 neutrons per second were produced by D–D and D–T reactions, respectively. In addition, in the NX2 device with 16 Hz working frequency, 1.34 × 1010 and 1.34 × 1012 neutrons per second were produced by D–D and D–T reactions, respectively. The results show that with regards to the sizes and energy of these devices, they can be used as the efficient neutron generators.

A novel method to survey parameters of an ion beam and its interaction with a target

Beam profile and composition of the pulsed ion beam from a vacuum arc source are valuable information for designing a high-intensity deuterium-tritium neutron generator. Traditional methods are notoriously difficult to obtain the information at the same time. A novel off-line diagnostic method is presented, which can obtain thetransverse beam profile with high resolution as well as species of the ions in the beam. The method is using a silicon target with high purity to interact with the ion beam, and then use secondary ion mass spectrometry (SIMS) to analyze the interaction zone of the target to get the beam information. More information on beam-target interaction could get simultaneously. Proof-of-principle simulation and experimental works have demonstrated this method is practical.

New target solution for a muon collider or a muon-decay neutrino beam facility: The granular waterfall target

A new target solution, the granular waterfall target, is proposed here for a muon collider or a muon-decay neutrino beam facility, especially for the moment which adopts a 15 MW continuous-wave (cw) superconducting linac. Compared to the mercury jet target, the granular waterfall target works by a much simpler mechanism which can operate with a much more powerful beam, which are indicated by the detailed investigations into the heat depositions and the evaluations of the temperature increases for different target concepts. By varying proton beam kinetic energy and the geometrical parameters of the waterfall target, an overall understanding of the figure of merit concerning muon production for this target concept as the target solutions of the long-baseline neutrino factory and the medium-baseline moment is obtained. With 8 GeV beam energy and the optimal geometrical parameters, the influence on muon yield by adopting different beam-target interaction parameters is explored. Studies and discussions of the design details concerning beam dumping are also presented.