High-energy Beam Research Articles

National pilot-study on verification of calculated absorbed dose distribution to be delivered in advanced radiotherapy treatment

Dosimetry audits in radiation oncology are indicated in the Council Directive 2013/59/EURATOM as one of several measures to ensure high quality of absorbed dose delivery in radiation therapy. Therefore, a national pilot-study was prepared and conducted for an on-site dosimetry audit on the 2D pre-treatment verification methodology. The aim was to explore the possibility of introducing such audits at the national level and examine the feasibility of extending such a concept.The main activities performed were developing and verifying methodology to be applied elsewhere, assembling a survey related to the application of advanced radiotherapy techniques, point and 2D absorbed dose measurements, and acquiring data for on-site and off-site data validation. The measurements of 2D absorbed dose distributions of different complexities were performed using local and auditor's (reference) equipment. The beam output, dose linearity, and field output factors were determined using a reference set of equipment only.Eight high-energy photon beams were evaluated. The participating centres fulfilled the recommended criterion of ±2% for beam output. Seven beams fulfilled the dose linearity criterion. Comparison of field output factors exhibited out-of-tolerance discrepancies only for the smallest field size of 2 × 2 cm2.For the evaluation of 2D absorbed dose distributions, the results obtained with local equipment showed that all absorbed dose distributions had gamma (γ) passing rate ≥95% for the 3%/2 mm tolerance criterion. However, the γ passing rates obtained with the reference equipment were lower for most verified beams. Some of the analysed absorbed dose distributions did not fulfil the recommended γ passing rate acceptance criterion. γ passing rates have shown a statistically significant difference for 3%/2 mm and 2%/2 mm criteria with p = 0.0117 and p = 0.0212, respectively, comparing the results obtained by reference and local equipment.External audits related to the 2D dosimetrical pre-treatment verification of calculated dose distributions provide the advantage of being independent of the equipment and methodology used locally. Such audits can be a valuable tool for the evaluation and improvement of local practices in the application of advanced radiotherapy techniques.

Installation, commissioning, and testing of the HB650 CM at PIP2IT

The Proton Improvement Plan-II (PIP-II) is a major upgrade to the Fermilab accelerator complex, featuring a new 800-MeV Superconducting Radio-Frequency (SRF) linear accelerator (LINAC) powering the accelerator complex to provide the world’s most intense high-energy neutrino beam. This paper describes the conversion of the PIP-II Injector Test Facility (PIP2IT) cryogenic system into a test stand for PIP-II High-Beta 650 MHz (HB650) cryomodules at Fermilab’s Cryomodule Test Facility (CMTF). A description of the associated mechanical, electrical, and controls modifications necessary for testing HB650 cryomodules are provided. The cooldown and warmup requirements, procedures and associated controls logic is described.

Overview and status of the PIP-II cryogenic system

The Proton Improvement Plan-II (PIP-II) is a major upgrade to the Fermilab accelerator complex, featuring a new 800-MeV Superconducting Radio-Frequency (SRF) linear accelerator (Linac) powering the accelerator complex to provide the world’s most intense high-energy neutrino beam. The PIP-II Linac consists of 23 SRF cryomodules operating at 2 K, 5 K, and 40 K temperature levels supplied by a single helium cryoplant providing 2.5 kW of cooling capacity at 2.0 K. The PIP-II cryogenic system consists of two major systems: a helium cryogenic plant and a cryogenic distribution system. The cryogenic plant includes a refrigerator cold box, a warm compressor system, and helium storage, recovery, and purification systems. The cryogenic distribution system includes a distribution box, intermediate transfer line, and a tunnel transfer line consisting of modular bayonet cans which supply and return cryogens to the cryomodules. A turnaround can is located at the end of the Linac to turnaround cryogenic flows. This paper describes the layout, design, and current status of the PIP-II cryogenic system.

Design and beam dynamics simulation of an 8 MeV compact accelerator-driven neutron source

A compact accelerator-driven neutron source is proposed at Sino-French Institute of Nuclear Engineering and Technology, Sun Yat-Sen University, called Sun Yat-Sen University Proton Accelerator Facility (SYSU-PAFA). The proton accelerator is composed of a proton electron cyclotron resonance source, a four-vane radio frequency quadrupole (RFQ), and an alternative phase focusing drift tube linac (APF-DTL). It can accelerate 10 mA proton beam to 8 MeV. Due to the high current, beam matching is particularly important. In order to achieve beam matching between various components, beam transport sections are needed. The beam transport line is divided into three segments. The Low Energy Beam Transport (LEBT) ensures that the beam parameters are matched before entering the RFQ. The Medium Energy Beam Transport (MEBT) segment efficiently transfers the beam between the RFQ and DTL. The High Energy Beam Transport (HEBT) focuses on transporting the beam to the targets. The design goal of beam transport line is as short as possible while ensuring high efficiency of beam transportation. SYSU-PAFA has an overall transmission efficiency of 99%, with optimal transverse matching conditions between beam transport and RFQ or DTL accelerators. The efficient use of solenoids and magnets allows for a compact transmission section, resulting in a total length of 13.6 meters, shorter than most accelerators at the same beam energy. This paper will provide the detailed beam dynamics of the compact accelerator.

Driving Inertial Confinement Fusion With Strong Pulsed Magnetic Field

Regarding inertial confinement fusion (ICF), the current proposed driving energy sources are mainly laser beams or high-energy particle beams. This paper proposes a new method: Adopting a strong pulsed magnetic field as the driving energy source, explored its action principle, derived all relevant formulas, calculated an example and compared it with existing driving methods.The conclusion drawn is that this method can achieve high energy gain, the required equipment is relatively simple and without the disadvantages of other methods, making it a feasible method.

Proton and neutron density distributions at supranormal density in low- and medium-energy heavy-ion collisions. II. Central Pb + Pb collisions

This paper represents a continuation of our investigation into the limitations on total, proton, and neutron particle number densities, as well as the asymmetry of proton and neutron density distributions achievable in central heavy-ion collisions. We explore these aspects at low and medium energies within the framework of the Boltzmann-Uhlenbeck-Uehling (pBUU) transport and time-dependent Hartree-Fock (TDHF) models. Previous studies, focusing on symmetric and asymmetric collisions of Ca and Sn nuclei [1], and initial results on Pb-nuclei collisions [2], emphasized the role of the Coulomb interaction in these events. Our findings indicated that: (i) the highest total densities predicted at Ebeam=800 MeV/nucleon were on the order of ≈2.5ρ0 (ρ0=0.16fm−3), (ii) the proton-neutron asymmetry for maximal densities, δ=(ρnmax−ρpmax)/(ρnmax+ρpmax), did not generally exceed the asymmetry in the initial state of the collision at all beam energies and tended to decrease during the reaction, and (iii) a significant portion of this asymmetry had its microscopic origin in Coulomb forces, masking the pure nuclear contribution. These new findings, particularly relevant in the astrophysical context, are further examined in this work, focusing on the heaviest target-projectile combination Pb212,208 accessible in an experiment. We introduce the SkT3 Skyrme force model, not previously used for the Pb system, and compare it to the SV-bas and SV-sym34 models to explore the symmetry-energy dependence of the results. Contour plots of nucleonic densities are presented, contrasting the time evolution of the density distributions in low (TDHF) and high (pBUU) models. We also present the evolution of normalized maximal proton, neutron, and total nucleon number density with increasing beam energy in the full pBUU model and the Vlasov approximation, aiming to explore the impact of correlations in the reaction. The time evolution of the proton and neutron density distributions in the plane transverse to the beam direction is illustrated at both low and high beam energy. In conclusion, our detailed examination of the Pb system in this work provides further essential evidence that the aforementioned findings (i)–(iii) are only weakly dependent on system size and a symmetry-energy model, and thus, they are of more general importance. Published by the American Physical Society 2024

Proton spectroscopy for 11B(p,α)2α fusion reaction with RCF films: calibration and unfolding procedure

The reaction occurring between protons and 11B isotope (p+11B → 3α+8.7 MeV) has recently attracted attention as a possible candidate to overcome the generation of high-energy neutrons via the more studied Deuterium-Tritium fusion reaction. Since the early 2000s, several experiments have been carried out to investigate the viability of triggering this aneutronic reaction in laser-target interaction schemes. During these experiments, the total number of escaping α particles is measured to infer fusion reaction efficiency. However, the accurate detection of α particles in such experiments poses a real challenge.In this scenario, RadioChromic Films(RCFs) arranged in a stack configuration can be used for the fluence and energy spectra reconstruction of generated protons, being this mandatory information in both “pitcher-catcher” and “in plasma” p-11B irradiation schemes. Nevertheless, RCF response exhibits a dependence on Linear Energy Transfer (LET), which leads to an underestimation of the response in high-LET conditions. This can result in dosimetric errors if not properly taken into account.In this work, an analytical procedure able to reconstruct the incident energy spectra in an RCF stack was developed and validated thanks to a calibration procedure that was established for high and low proton energy (4–60 MeV) beams to properly reconstruct the incident spectra in the “pitcher-catcher” irradiation scheme.

Status of dual-readout calorimetry for future high-energy physics experiments

Future experiments at high energy e + e - colliders will focus on extremely precise Standard Model measurements. Among the most important physics benchmarks, there is the capability to resolve the Higgs decays into W or Z pairs, in their completely hadronic decay modes (4 jets in the final state), only based on the invariant mass of the jet pair coming from decay of the on-shell boson. This translates into a relative energy resolution target of 30%/√E, well beyond current detector performances. Dual-readout calorimetry is a technique which aims to improve the energy resolution, for single hadrons and hadronic jets, exploiting the information produced by two different physical processes, namely scintillation and Čerenkov light emission. The IDEA detector, whose concept has been included in both the FCC and CEPC Conceptual Design Reports, is based on a dual-readout fibre calorimeter with independent fibre readout exploiting Silicon PhotoMultipliers (SiPMs). The individual SiPM information will be beneficial for a highly granular calorimeter design, opening up to advanced reconstruction techniques such as Particle Flow and a variety of neural network algorithms.In this paper the status of calorimeter prototypes that have been developed to demonstrate the feasibility of the dual-readout method in association with the high granularity feature is illustrated. The specific choice for the design of each prototype is presented, together with the performances achieved at high-energy test beams or through simulations.

Grid/lattice therapy: consideration of small field dosimetry.

Small-field dosimetry used in special procedures such as gamma knife, Cyberknife, Tomotherapy, IMRT, and VMAT has been in evolution after several radiation incidences with very significant (70%) errors due to poor understanding of the dosimetry. IAEA-TRS-483 and AAPM-TG-155 have provided comprehensive information on small-fields dosimetry in terms of code of practice and relative dosimetry. Data for various detectors and conditions have been elaborated. It turns out that with a suitable detectors dose measurement accuracy can be reasonably (±3%) achieved for 6 MV beams for fields >1×1cm2. For grid therapy, even though the treatment is performed with small fields created by either customized blocks, multileaf collimator (MLC), or specialized devices, it is multiple small fields that creates combined treatment. Hence understanding the dosimetry in collection of holes of small field is a separate challenge that needs to be addressed. It is more critical to understand the scattering conditions from multiple holes that form the treatment grid fields. Scattering changes the beam energy (softer) and hence dosimetry protocol needs to be properly examined for having suitable dosimetric parameters. In lieu of beam parameter unavailability in physical grid devices, MLC-based forward and inverse planning is an alternative path for bulky tumours. Selection of detectors in small field measurement is critical and it is more critical in mixed beams created by scattering condition. Ramification of small field concept used in grid therapy along with major consideration of scattering condition is explored. Even though this review article is focussed mainly for dosimetry for low-energy megavoltage photon beam (6 MV) but similar procedures could be adopted for high energy beams. To eliminate small field issues, lattice therapy with the help of MLC is a preferrable choice.

A few-degree calorimeter for the future electron-ion collider

Measuring the region 0.1<Q2<1.0 GeV2 is essential to support searches for gluon saturation at the future Electron-Ion Collider. Recent studies have revealed that covering this region at the highest beam energies is not feasible with current detector designs, resulting in the so-called Q2 gap. In this work, we present a design for the Few-Degree Calorimeter (FDC), which addresses this issue. The FDC uses SiPM-on-tile technology with tungsten absorber and covers the range of −4.6<η<−3.6. It offers fine transverse and longitudinal granularity, along with excellent time resolution, enabling standalone electron tagging. Our design represents the first concrete solution to bridge the Q2 gap at the EIC.

Simulating chemical mixing and molten pool shape in dissimilar welds using thermal fluid dynamics

Estimating the properties of dissimilar metal welded joints made using modern high-energy beam techniques presents significant challenges due to the complex nature of the process. These complexities arise from the different thermal and mechanical properties of the materials involved. The properties of a welded joint are primarily determined by the element mixing and final chemical composition when two dissimilar metals are fused together, or when a dissimilar filler material is used. Hence, a representative model capable of tracking elemental distribution and temperature is essential for accurately estimating the micro-scale and macro-scale mechanical properties of the joint, thus optimising the joining process. In this work, a high-fidelity thermal fluid flow model in the multiComponentlaserbeamFoam computational fluid dynamics (CFD) solver is used to simulate the process of laser beam welding. For this purpose, the joining process of AISI 304 stainless steel with a low alloy steel filler material (G3Si1) is simulated. This framework is rigorously validated with experimental results showing the capabilities of such modelling approach. Different strategies to model the filler and material properties are explored: a stationary filler model, applied through the parent material's thickness, was found to accurately mirror experimental results. This model is then used to study the flow properties, thermocapillary effect, and diffusion on the intermixing of composition, aspects that have not been previously examined in depth. The thermocapillary forces were concluded to be the most significant, dictating the peak composition value, the shape and topology of the molten pool. Diffusion fluxes were found to be negligible and not responsible for the majority of the mixing.

Nickel-hexagonal phase induced in Ni3Si-monoclinic intermetallic phase by ion beam irradiation

A hypereutectic Ni alloy with 22 at. % Si was irradiated with a high-energy nickel ion beam and high ion fluence at 650°C to induce the formation of intrinsic and extrinsic point defects. Under these irradiation conditions, high concentrations of point defects were formed in the irradiated region. The recovery process initiated due to the damage induced by irradiation led to the formation of a nanoparticle population in the irradiated region. The irradiated region was characterized by high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The experimental evidence obtained permitted the establishment of an event sequence that culminated in nanoparticle population formation. The event sequence had the following stages: (a) Ni atom population implantation within a specific zone of the irradiated region; (b) nucleation and growth of a Nickel-hexagonal phase due to ordering of the implanted nickel atoms; and (c) Ni-hexagonal phase nanoparticle growth within a specific region of the irradiated region. The HRTEM analysis yielded crucial insights into the mechanisms underlying nanoparticle formation. The two most important aspects are as follows: firstly, the nucleation of Nickel-hexagonal phase into an amorphous region, and secondly, the non-equilibrium nature of the Nickel-hexagonal phase of the Nickel metallic system. These experimental findings are important for implantation technology; implanting atomic species into certain materials to create composite materials can lead to the formation of non-equilibrium phases and amorphous regions. Both of these outcomes have the potential to adversely affect the properties of the composite material.

Shielding optimization to reduce the radiation field in the accelerator systems of IFMIF-DONES

In IFMIF-DONES, a deuteron beam will impinge on a flowing liquid lithium target, resulting in an intense neutron source. Other radiation sources will also arise due to the interactions between deuterons and the beam facing accelerator components. These radiation fields may cause some negative effects, such as damage to equipment or the generation of residual radiation sources. The characterization and mitigation of all the radiation sources are crucial for a safe operation and maintenance of the facility. In this study, the optimization and/or implementation of some radiation shields located in critical areas is considered to reduce the doses during operation and shutdown. Three scenarios are assessed: (i) shielding optimization of the High-Power Beam Dump for the accelerator commissioning, (ii) shielding optimization for the scraper of the High Energy Beam Transport line and the Fast Safety Isolation Valves, and (iii) shielding implementation to reduce the radiation transmission through Heating, Ventilation, and Air Conditioning wall penetrations. Radiation maps of the biological dose and the dose to silicon are computed, showing the impact of such shielding elements.

Enhanced positron acceleration driven by femto-second laser pulses irradiating structured targets

We have proposed a compact scheme for generating high-density and high-energy positrons by irradiating different shaped targets with an ultra-intense laser pulse, using 2D particle-in-cell simulations and numerical analysis. Our simulations show that the Breit–Wheeler process dominates positron production during laser-target interaction when a laser with an intensity of 4×1023 Wcm−2 is used. We obtain a positron beam with an energy of 2.5 GeV and a total number exceeding 109, which is an improvement by two orders of magnitude compared to previous work with the same laser intensity. By using different shaped targets, we are able to generate a high-energy positron beam with low divergence. The yield of positron pairs depends on both the target and the laser parameters, and we have investigated how the shape of the target can enhance pair production and reduce divergence. Both of our analytical and simulation results demonstrate that this high-flux and low-divergence positron beam has direct applications in the field of medical and astro-physics that can be explored in the upcoming high intensity laser facilities.

Simulation-guided design of a target-cooling system for cyclotron-based isotope production

Isotopes are an important aspect of modern medical and scientific research and cyclotron-based isotope production is of particular interest. Cooling devices are required to manage the heat generated by high-energy particle beams to ensure that they can be delivered securely. However, there is considerable scope for further advancements in the design of cooling systems. Therefore, this study uses simulations to investigate the design of innovative cooling systems. Various designs and materials are considered using a variable four-sector collimator and various particle-beam conditions. Thus, new design principles and material and structural optimization strategies are proposed, which can be used to improve the stability and efficiency of isotope production. The results provide insight into technical challenges and may contribute toward advances in medical diagnostics, radiotherapy, and fundamental scientific research. In particular, they can guide the development of isotope-based technologies in nuclear medicine.

Engineering design status of IFMIF-DONES High Energy Beam Transport line and Beam Dump system inside the TIR and RIZ

IFMIF-DONES (International Fusion Materials Irradiation Facility – DEMO Oriented Neutron Source) is a fusion materials testing facility that is currently being designed under the framework of a work package of the EUROfusion Consortium. It will use a 125mA at 40MeV deuteron beam to generate a high neutron flux through Li(d,xn) stripping nuclear reactions in a liquid lithium target. The High Energy Beam Transport line (HEBT), the most upstream system of the IFMIF-DONES accelerator, is responsible for the guidance and shaping of the beam towards the target. Additionally, during commissioning periods, the HEBT is also responsible for diverting the beam, through the Beam Dump Transport Line, to the Beam Dump for testing purposes. The HEBT is spread along different rooms and zones: the Accelerator Vault, the Radiation Interface Zone (RIZ), and Target Interface Room (TIR). The engineering design of the HEBT components situated within the TIR and RIZ has been updated to satisfy new requirements, with a focus on ensuring the protecting of the Fast Isolation Valve (FIV) from the backscattered radiation from the target. These modifications include relocating the FIV from the TIR to the RIZ, adjusting the building layout to accommodate the new FIV module, configuring an enclosure cabinet for the RIZ, and adding local shielding to extend the lifetime of the FIV seal actuators. This work describes the current status of these TIR and RIZ engineering design, including radioprotection, commissioning and maintenance plan, beam diagnostics devices, beam dynamics and new remote handling approaches, as well as the layout and integration of the required components along the beamline. The TIR and RIZ are critical areas for IFMIF-DONES, and their design and operation must be compliant with functional, reliability and safety requirements. The updated design addresses potential issues and enhances the facility’s overall functionality.

Methodology for measuring photonuclear reaction cross sections with an electron accelerator based on Bayesian analysis

Accurate measurements of photonuclear reaction cross sections are crucial for a number of applications, including radiation shielding design, absorbed dose calculations, reactor physics and engineering, nuclear safeguard and inspection, astrophysics, and nuclear medicine. Primarily motivated by the study of the production of selected radionuclides with high-energy photon beams (mainly 225Ac, 47Sc, and 67Cu), we have established a methodology for the measurement of photonuclear reaction cross sections with the microtron accelerator available at the Swiss Federal Institute of Metrology (METAS). The proposed methodology is based on the measurement of the produced activity with a High Purity Germanium (HPGe) spectrometer and on the knowledge of the photon fluence spectrum through Monte Carlo simulations. The data analysis is performed by applying a Bayesian fitting procedure to the experimental data and by assuming a functional trend of the cross section, in our case a Breit-Wigner function. We validated the entire methodology by measuring a well-established photonuclear cross section, namely the 197Au(γ, n)196Au reaction. The results are consistent with those reported in the literature.

Characterization of the deformation behavior and microstructure evolution in laser bending of TC4 titanium alloy heavy plate

A new plastic processing method for laser bending of TC4 titanium alloy heavy plates was developed in this work. Different from previous studies, the thickness of the plates in this work reached 6 and 12 mm. High-energy laser beam was applied on the surface of the TC4 titanium alloy heavy plate, resulting in thermal stress on the surface of the plate and causing bending deformation. The microstructure and mechanical properties of the bended plates were investigated. A finite element model was also developed to simulate the laser-assisted bending process of the TC4 titanium alloy heavy plate. The microstructure observation indicates that the original α + β worm-like microstructure changed to basket-weave microstructure composed of α′ phase of acicular martensite after laser bending. This microstructure with high densities of dislocation and twinning played an important role in grain boundary strengthening. Therefore, the hardness of the center of the heat-affected zone &amp;gt; the hardness of the base metal &amp;gt; the hardness of the edge of the heat-affected zone after bending. The tensile strength of the heat-affected zone is not significantly different from that of the base metal, but the tensile elongation is slightly lower than that of the base metal and its plasticity is lower. The simulation implies that temperature gradients in the normal direction caused by laser scanning can stimulate a horizontal partial stress σx. The variation of σx causes the plate form a bending angle after laser scanning.

Improving the potential of BDF@SPS to search for new physics with liquid argon time projection chambers

Beam dump experiments proposed at the SPS are perfectly suited to explore the parameter space of models with long-lived particles, thanks to the combination of a large intensity with a high proton beam energy. In this paper, we study how the exploration power may be augmented further by installing a detector based on liquid argon time projection chamber technology. In particular, we consider several signatures of new physics particles that may be uniquely searched for with such a detector, including double bang events with heavy neutral leptons, inelastic light dark matter, and millicharged particles.

Commissioning of a gantry beamline with rotator at a synchrotron-based ion therapy center

This paper provides an overview of the worldwide first commissioning of a gantry beamline with a rotator at the MedAustron synchrotron-based proton/ion cancer therapy facility in Wiener Neustadt, Austria. The gantry beamline consists of the high energy beam transfer (HEBT) line and the gantry beam transport system. It transports the beam from the synchrotron to the gantry-room isocenter. The HEBT transports the beam from the synchrotron to the gantry entrance, which is the coupling point between the HEBT and the gantry. The rotator is one of the HEBT modules, thus it is an integral part of the gantry beamline. The MedAustron rotator is the worldwide first rotator system used to match slowly extracted asymmetric beams from the synchrotron to the rotating gantry. In this paper, main attention is paid to ion-optical and beam-alignment aspects of the beamline commissioning. A novel orbit-correction and beam-alignment technique has been developed specifically for the beamline with the rotator. While the theoretical concept of the rotator has existed for almost two decades, the MedAustron rotator is the first hardware implementation of this concept all over the world. The presented overview of the beamline commissioning includes a description of the principal technical solutions and main results of the first beam-transport measurements. Since the measured beam size and beam position agree well with theoretical predictions, one can conclude that the proof-of-concept of the rotator-matching has been successfully accomplished. Published by the American Physical Society 2024