Intense Proton Beam Research Articles

Search by the SENSEI Experiment for Millicharged Particles Produced in the NuMI Beam.

Millicharged particles appear in several extensions of the standard model, but have not yet been detected. These hypothetical particles could be produced by an intense proton beam striking a fixed target. We use data collected in 2020 by the SENSEI experiment in the MINOS cavern at the Fermi National Accelerator Laboratory to search for ultrarelativistic millicharged particles produced in collisions of protons in the NuMI beam with a fixed graphite target. The absence of any ionization events with 3 to 6 electrons in the SENSEI data allow us to place world-leading constraints on millicharged particles for masses between 30 to 380MeV. This work also demonstrates the potential of utilizing low-threshold detectors to investigate new particles in beam-dump experiments, and motivates a future experiment designed specifically for this purpose.

For intense proton beam production with compact ion sources: the ALISES ion source family developed at CEA Saclay

The production of intense proton beams in CEA Saclay started in the 90’s with the development of the SILHI source to inject the IPHI accelerator. This ECR ion source is still in operation nowadays. ECR plasma is a well-known heating process and plasma chamber internal dimensions were investigated in order to reduce size and maintenance time. In 2012 R&D investigations on those simple plasma chamber parameters were started with the design of the first ALISES ion source that will give birth to a new source family still in progress today. This paper will summarize the different steps of this development.

LHC Upgrades in preparation of Run 3

The Large Hadron Collider (LHC) Long Shutdown 2 (2019–2021), following LHC Run 2, was primarily dedicated to the upgrade of the LHC Injectors but it included also a significant amount of activities aimed at consolidation of the LHC machine components, removal of known limitations and initial upgrades in view of the High-Luminosity LHC (HL-LHC) to favour the intensity ramp-up during Run 3 (2022–2025). An overview of the major modifications to the accelerator and its systems is followed by a summary of the results of the superconducting magnet training campaign to increase the LHC operation energy beyond the maximum value of 6.5 TeV reached during Run 2. The LHC configuration and the scenarios for proton and ion operation for Run 3 are presented considering the expected performance of the upgraded LHC Injectors and the proton beam intensity limitations resulting from the heat load on the cryogenic system due to beam-induced electron cloud and impedance.

Laser-to-proton conversion efficiency studies for proton fast ignition

We assess the conversion efficiency from intense picosecond laser pulses to multi-MeV ion beams for a wide range of laser and target parameters, using 2D kinetic particle-in-cell simulations. Scalings are addressed in a quasi-one-dimensional geometry, leaving out beam divergence. Then, we study the conversion efficiency into a narrow spatial band along the laser axis for flat and hemispherical targets in large-scale 2D simulations. Combining these findings allows us to calculate the energy requirements for ignition of a compressed ICF target with an intense proton beam in a fast-ignition scenario.

Study of the 20Ne(p,γ)21Na reaction at LUNA

The NeNa-MgAl cycles are involved in the synthesis of Ne, Na, Mg, and Al isotopes. The 20Ne(p,γ)21Na (Q = 2431.68 keV) reaction is the first and slowest reaction of the NeNa cycle and it controls the speed at which the entire cycle proceeds. At the state of the art, the uncertainty on the 20Ne(p,γ)21Na reaction rate affects the production of the elements in the NeNa cycle. In particular, in the temperature range from 0.1 GK to 1 GK, the rate is dominated by the 366 keV resonance corresponding to the excited state of EX = 2797.5 keV and by the direct capture component. The present study focus on the study of the 366 keV resonance and the direct capture below 400 keV. At LUNA (Laboratory for Underground Nuclear Astrophysics) the 20Ne(p,γ)21Na reaction has been measured using the intense proton beam delivered by the LUNA 400 kV accelerator and a windowless differential-pumping gas target. The products of the reaction are detected with two high-purity germanium detectors. The experimental details and preliminary results on the 366 keV resonance and on the direct capture component at very low energies will be shown, together with their possible impact on the 20Ne(p,γ)21Na reaction rate.

Resistive field generation in intense proton beam interaction with solid targets

The Brown–Preston–Singleton (BPS) stopping power model is added to our previously developed hybrid code to model ion beam–plasma interaction. Hybrid simulations show that both resistive field and ion scattering effects are important for proton beam transport in a solid target, in which they compete with each other. When the target is not completely ionized, the self-generated resistive field effect dominates over the ion scattering effect. However, when the target is completely ionized, this situation is reversed. Moreover, it is found that Ohmic heating is important for higher current densities and materials with high resistivity. The energy fraction deposited as Ohmic heating can be as high as 20%–30%. Typical ion divergences with half-angles of about 5°–10° will modify the proton energy deposition substantially and should be taken into account.

Gas sheet beam induced fluorescence based beam profile measurement for high intensity proton accelerators

The paper describes the design simulations, developmental details and characterization results of a dual gas sheet generator system for non-invasive beam profile measurement of high-intensity proton beams. The system is being developed for the Low Energy High Intensity Proton Accelerator facility at Bhabha Atomic Research Centre, India. To our knowledge, this is the first time an intense low energy proton beam was used to directly view the beam induced fluorescence of a gas sheet. The system works by generating two thin nitrogen gas sheets which produces fluorescence when a charged particle beam passes through them, thereby providing a visual representation of the beam's intensity profile. The gas sheets are generated at 45° to the beam axis, which allows the fluorescence created by the interaction to be viewed directly through a viewport or camera capture. The beam profile measurements were carried out with a typically 20 keV, 10 mA pulsed proton beam from an ECR ion source under different operating parameters like gas sheet pressure, beam current, beam energy and focusing magnetic field. The Geant4 simulation has been performed to study the scintillation process and optical transport. It may become useful to study methods of reconstructing the beam profile from image obtained.

Comorbidities and Their Impact on Treatment Tolerance and Outcome in Elderly NSCLC Patients Treated with Concurrent Chemoradiation Using Proton or Photon Followed by Immunotherapy

To investigate comorbidities and their impact on treatment tolerance and survival for elderly NSCLC patients treated with concurrent chemoradiation using proton beam therapy (PBT) or intensity modulated radiation therapy (IMRT) followed by immunotherapy (IO). This is a retrospective study in senior patients (≥ 65 years) with inoperable locally advanced- NSCLC (LA-NSCLC) who received concurrent chemoradiation (CRT) therapy followed by adjuvant IO. Comorbidities are listed in table 1 and scored according to hazard ratios (HRs) of death. Treatment tolerance and comorbidities were compared between modalities using Fisher's exact test. Association between comorbidities and treatment tolerance was analyzed using logistic regression; association between comorbidities and survival was analyzed by Cox proportional hazards regression. Total 218 patients were included with median age of 72 (range 65-86) years. Fifty-three (24.3%) were PBT and 165 (75.7%) were IMRT. Majority patients were white ethnics, had stage III adenocarcinoma disease and good performance score, and received RT dose 60-66 Gy. The median follow-up time for the whole group was 23 months. A 97% of patients had ≥1, and 62% had ≥4 comorbidities. The combined comorbidity scores ranged from 0 to 25. No significant difference in comorbidities between modalities except IMRT had more patients with COPD (36% vs. 51%, p = 0.047). Rates of hospitalization and ER visit during CRT+IO were 28% and 5%, respectively. Rates of IO discontinuation and interruption were 55% and 8%, respectively. Patients received >6 months IO had significantly lower risk of death (HR: 0.25, p<0.001). No significant difference in treatment tolerance between modalities. In multivariable analysis, atrial fibrillation, pulmonary disease, and depression were the comorbidities associated with hospitalization during CRT+IO (p<0.05); dementia was the comorbidity associated with IO interruption (p = 0.042); heart failure, COPD, asthma, osteoporosis and HIV were the comorbidities associated with poor OS (p<0.05). Combined comorbidity score was associated with OS with HR of 1.13 (p<0.001) with adjustment of race, GTV and induction chemotherapy. Comorbidities were associated with hospitalization and IO interruption during the whole course of CRT and IO therapy, with increased IO discontinuation which negatively impacted survival. Evaluating and scoring comorbidities at diagnosis could be a useful method to predict risk of death before treatment start.

Correlated characterization of 20Ne-implanted targets using nuclear reaction analysis, Rutherford backscattering spectrometry, and ion transport modeling

We present the preparation and characterization of a large sample of implanted noble gas targets for use in precision nuclear astrophysics measurements with intense proton beams. Tantalum and titanium backings were prepared using wet-acid etching, outgassed via resistive heating, and implanted with 20Ne+ beams from differing ion sources. These experimental targets were investigated using both nuclear reaction analysis techniques on the 1169-keV resonance in 20Ne(p, γ)21Na and Rutherford backscattering spectrometry analysis with 2-MeV α-particle beams. Results from these analyses reveal small target-to-target variations in stoichiometry, while exhibiting excellent agreement independent of ion-beam analysis method. We also present a self-consistent validation of the nuclear reaction analysis results using ion transport simulations in TRIM-2013 that rely on input parameters from SIMNRA scattering-yield fits to Rutherford backscattering spectra. In addition to a complete description of the implantation profile, this analysis method provides an alternate solution for characterizing a large sample of implanted targets when no suitable resonances are available for nuclear reaction analysis.

Physics at the Legnaro National Laboratories: present activities and future challenges

The Legnaro National Laboratories are one of the four INFN laboratories and they are mainly dedicated to experimental nuclear physics and astrophysics, within the field of nuclear structure and dynamics, where heavy ion induced reactions at medium-low energies are involved. Moreover, high level technologies for the construction of particle accelerators and experimental instruments and apparatuses are studied and developed. The laboratory is at present involved in the construction of the SPES facility, which concerns the development of a new research infrastructure devoted to the production of exotic beams for nuclear physics study and new radioisotopes for nuclear medical applications. The heart of SPES is an innovative cyclotron, B70, capable of providing high intensity proton beams (up to 750 μA) in the energy range between 35 and 70 MeV. A description of the present and future challenges at the Legnaro National Laboratory will be given.

Reliability analysis of core power optimization control using Kalman filter for accelerator driven system based on reconfigurable computing

Accelerator Driven System (ADS) is a promising nuclear facility for the transmutation of minor actinides and long-lived fission products, which is constructed by proton accelerator, spallation target and sub-critical reactor. For the industrial implementation, the reliability of core power control system in the operation process has to be analyzed and verified in considering the dynamic characteristics and real time response for the safety operation strategy. Therefore, a digitalization of Instrumentation and Control (I&C) system for ADS that can predict the changing value of proton beam intensity has been suggested in this research to get the appropriate variation of reactor core power without arousing the unexpected impulse to the main structures. In order to accurately analyze the random behavior of the precursor concentrations and the neutron density in sub-critical reactor, the stochastic differential equation model has been developed, and the closed-loop control system in describing the mapping relationship between the proton beam intensity and the corresponding core power has been established. The Kalman filter has been adopted for the optimal design of proposed analysis method to achieve the competitive predicting performance in operation process, and all the algorithms have been implemented on the XILINX ZYNQ System-on-Chip (SoC) using reconfigurable computing technology to meet the real time design requirements for embedded applications. Finally, the reliability of core power control model has been tested against Monte Carlo calculations and all the results demonstrate the good performance in predicting the core power with acceptable efficiency.

Excitation functions of the 197Au(p,pxn) and 197Au(p,xn) reactions

Abstract The cross-sections for the 197Au(p,pxn)196-193Au and 197Au(p,xn)197,195,193Hg reactions within the proton energy range of 49.8–65.5 MeV were measured at the high-intensity proton linac facility (KOMAC) in Korea using the stacked-foil activation and off-line γ-ray spectrometric technique The proton beam intensity was determined based on the natCu(p,x)62Zn monitor reaction with the recommended cross-section accessed from the IAEA database library. The data gathered in the present work are compared with the available data from the literature, which agreed well with each other. In this study, the 197Au(p,p5n)193Au reaction cross-section was measured for the first time. The data from the present work and existing literature were compared with the TALYS-1.9-based data taken from the TENDL-2019 library, which generally agreed well.

Cross-Section Measurements of the 11B(p,α)2α Reaction near the First Resonant Energy

In preparation for an experiment with a laser-generated intense proton beam at the Laser Fusion Research Center at Mianyang to investigate the 11B(p,α)2α reaction, we performed a measurement at very low proton energy between 140 keV and 172 keV using the high-voltage platform at the Institute of Modern Physics, Lanzhou. The aim of the experiment was to test the ability to use CR-39 track detectors for cross-section measurements and to remeasure the cross-section of this reaction close to the first resonance using the thick target approach. We obtained the cross-section σ = 45.6 ± 12.5 mb near 156 keV. Our result confirms the feasibility of CR-39 type track detector for nuclear reaction measurement also in low-energy regions.

Design studies on a high-power wide-band RF combiner for consolidation of the driver amplifier of the J-PARC RCS

A power upgrade of the existing 8-kW solid-state driver amplifier is required for the acceleration of high intensity proton beams on the J-PARC 3-GeV Rapid Cycling Synchrotron. The development of a 25-kW amplifier with gallium nitride (GaN) HEMTs, based on 6.4-kW modules is ongoing. The combiner is a key component to achieve such a high output power over the wide bandwidth required for multi-harmonic RF operation. This paper presents the preliminary design of the combiner. The circuit simulation setup and results, including the realistic magnetic core characteristics and frequency response of the cable, are reported.

Status of the COMET experiment

The COMET (COherent Muon to Electron Transition) experiment, currently being built in Tokai, Japan, will search for the coherent neutrinoless transition of muons to electrons in the coulomb field of atomic nuclei. The process is highly suppressed in the Standard Model and therefore provides a promising channel to probe new physics. The experiment will be carried out in a staged approach. Phase-I of COMET aims to search for the process with a single event sensitivity of 𝒪(10−15). Additionally, precise measurements of muon beam dynamics and detector prototyping for Phase-II will be conducted. Utilizing a much higher intensity proton beam, a more complex and longer muon/electron transport system, and gained experience from Phase-I, an improvement of at least four orders of magnitude over the current best branching ratio limit up to 𝒪(10−17) is envisioned for Phase-II. This article will give a status report for Phase-I of COMET.

3-D Protoacoustic Imaging Through a Planar Ultrasound Array: A Simulation Workflow.

Bragg peak range uncertainties are a persistent constraint in proton therapy. Pulsed proton beams generate protoacoustic emissions proportional to absorbed proton energy, thereby encoding dosimetry information in a detectable acoustic wave. Here, we seek to derive and model 3D protoacoustic imaging with an ultrasound array and examine the frequency characteristics of protoacoustic emissions. A formalism is presented through which protoacoustic signals can be characterized considering transducer bandwidth as well as pulse duration of the incident beam. We have also collected an experimental proton beam intensity signal from a Mevion S250 clinical machine to analyze our formalism. We also show that proton-acoustic image reconstruction is possible even when the noise amplitude is larger than the signal amplitude on individual transducers. We find that a 4μ s Gaussian proton pulse can generate a signal in the range of MHz as long as the spatial heating function has sufficiently high temperature gradients.

The reduction of the leakage field of the injection septum magnet in main ring of J-PARC

A new injection septum magnet 1 (Inj-SM1) was installed in the Main Ring (MR) of J-PARC in 2016 as an upgrade. We confirmed that the leakage field upstream from the circulating duct of Inj-SM1 was sufficiently smaller than that for the previous Inj-SM1. Nevertheless, we attempted to further reduce the leakage field by using a new magnetic shield to achieve a higher proton beam intensity. In 2017, the first version of the new magnetic shield was produced and installed. The strength of the leakage field with the shield was ≈30% of that without the shield; however, the magnetic field of a quadrupole magnet (QM) upstream of Inj-SM1 was reduced to below the permissible limit, ≈0.1% of the total field integral of the QM, from the point of view of beam optics. Consequently, the first version failed. A second shield, for which the defects of the first version were fixed, was produced in 2018. The strength of the leakage field of Inj-SM1 with the second shield was reduced to ≈30% of that without the shield, while that of the QM was maintained. Thus, we decided to use the second shield for beam operation starting in November 2019. We confirmed that the impact of the leakage field on the circulating beam was 1/20 of that of the previous Inj-SM1.

Investigation of resistive magnetic field generation by intense proton beams in dense plasmas

Current and future applications of intense proton sources abound, including radiography, cancer therapy, warm dense matter generation, and inertial confinement fusion. With increasingly efficient acceleration and focusing mechanisms, proton current densities may soon approach and exceed 1010 A/cm2, e.g., via intense laser drivers. Simulations have previously shown that in this current density regime, beam-induced field generation plays a significant role in beam transport through dense plasmas. Here, we present a theoretical model for the generation of resistive magnetic fields by intense proton beam transport through solid density plasmas. The theoretical evolution of the magnetic field profile is calculated using an analytic model for aluminum resistivity, heat capacity, and stopping power, applicable from cold matter to hot plasma. The effects of various beam and material parameters on the field are investigated and explained for both monoenergetic and Maxwellian proton beams. For a proton beam with Maxwellian temperature 5 MeV and total energy 10 J, the model calculates resistive magnetic fields up to 150 T in aluminum. The calculated field profiles from several beam cases are compared with 2D hybrid particle-in-cell simulations, with good agreement found in magnitude and time scale.

Patient Reported Quality of Life after Moderately Hypofractionated Proton Beam Therapy or Intensity Modulated Radiation Therapy for Prostate Cancer

<h3>Purpose/Objective(s)</h3> We aim to quantify and compare changes in patient reported quality of life (PRQOL) after moderately hypofractionated (MHF) Proton Beam Therapy (PBT) or Intensity Modulated Radiation Therapy (IMRT) for prostate cancer (PC). <h3>Materials/Methods</h3> This multi-institutional analysis included patients with NCCN low or intermediate risk PC treated at 4 tertiary cancer centers with MHF PBT or IMRT with prospective PRQOL collection. Patients completed International Prostate Symptom Score (IPSS) and Expanded Prostate Cancer Index Composite for Clinical Practice (EPIC) pre-treatment and at 3-to-6-month intervals starting at the end of treatment. EPIC is a questionnaire measuring health related quality of life (HRQOL) domains of genitourinary (GU), gastrointestinal (GI), sexual, and hormonal function. Questions are scored from 0 (no problem) to 4 (big problem). EPIC score of 3 or more was considered a meaningful QOL decrement. IPSS measures GU HRQOL; each question is measured from a score of 0 to 5 with a maximum score of 35. Baseline characteristics were compared with Chi squared and t test for IPSS. Models were limited to long term data, at 12 and 36 months. Generalized linear regression models testing effects of time, treatment, and their interaction were fit via Generalized Estimating Equations, controlling for age, race, and NCCN risk group. <h3>Results</h3> 287 IMRT and 485 PBT patients were included. Intermediate NCCN risk group (81.2 vs. 68.2%; p < 0.001), median age at diagnosis (70 vs 66.9 years; p < 0.001) were higher in the IMRT group. Mean IPSS was slightly worse at baseline in the PBT arm (+0.22; CI, -1.54 – 1.10; p=0.74) and slightly better at 3 years (-0.09; CI, -1.48 – 1.65; p=0.91). On Poisson regression controlling for age, race, and NCCN risk group, PBT IPSS trended worse at 12 months (OR, 1.19; CI, 0.98 - 1.44; p=0.077) without any difference at 36 months (OR, 1.08; CI, 0.80 - 1.26; p=0.94). Similarly, EPIC questionnaire for overall GI function trended worse with PBT at 12 months (CI, 0.83 - 16.27; p=0.085) without difference at 36 months (CI, 0.49 - 12.27, p=0.27). 4.9% and 4.8% patients in the PBT and IMRT arms, respectively, rated their overall GI function at 12 months as a severe problem. Among PBT and IMRT patients combined, severe GU concerns were unlikely at 12 months (GU frequency: 17.5; GU pain: 3.6; stream problem: 11.2%). <h3>Conclusion</h3> PRQOL showed a non-significant trend toward worse 1-year overall GI function and IPSS for PBT; this effect was not present at 3 years. In this multi-institutional, prospective study of PC, long-term GU and GI function was not significantly different between PBT or IMRT arms.

Characterization of Stray Radiation Produced by a Proton Beam in an Anthropomorphic Phantom with Dental Implants Using a Pixel Detector

<h3>Purpose/Objective(s)</h3> We investigated the scattered radiation produced by a collimated proton beam in the case of head and neck cancer using an anthropomorphic head phantom with human-like anatomy, with two dental implants inserted. Using high-resolution semiconductor pixel detectors, we measured and analyzed the backscatter radiation with particle identification resolving power. This research is focused on giving quantitative information about the radiation field components. <h3>Materials/Methods</h3> A treatment plan was designed on a standard X-ray CT which contained the implants at the center of the tumor. Two irradiations of an anthropomorphic head phantom were performed with clinical proton beams: one without metallic implants (plastic inserts) and one with dental implants. Two titanium cylindrical inserts of 1 cm length and 0.33 cm diameter were placed in the phantom's upper jaw like the molar's replacements. The planning target volume (PTV) is shaped so that the dental inserts are centered in the target volume. A scattered fixed proton beam with a nominal energy of 170 MeV was delivered to the phantom using collimators and boluses designed to shape and stop the beam according to the treatment plan. Scattered primary and secondary radiation was detected with hybrid semiconductor pixel detectors, placed at 4 cm behind the PTV. Detailed description of the mixed-radiation field was performed with spectral (energy loss) and tracking (direction) sensitivity. <h3>Results</h3> Measurements included a low intensity proton beam to assess the particle tracking response and identification resolving power in both situations (with and without implants). In this manner, the components of the radiation field were observed and analyzed. Based on their characteristic directional-sensitive spectral-track signal in the detector, both primary and secondary protons can be distinguished from light charged particles. This was done by analyzing single particle pixelated clusters morphology, spectral and directional sensitive parameters. Directional fluxes and linear energy transfer (LET) spectra of charged particle groups provide information about the scattered radiation field. <h3>Conclusion</h3> We present novel information about dental metallic implants' influences in a proton-based treatment. Preliminary results show differences in the LET distributions of the scattered radiation when the implants are in place, respectively, when they are missing. Further analyses will be done to provide a detailed dissemination of contribution for every type of particle.