High-energy Proton Beam Research Articles

A new data transfer scheme for the HL-LHC upgrade of the ATLAS Tile Hadronic Calorimeter

The Large Hadron Collider (LHC) is undergoing a series of upgrades towards a High Luminosity LHC (HL-LHC) that will deliver five times the LHC nominal instantaneous luminosity. The ATLAS experiment is one of the experiments at the LHC that investigates elementary particle interactions in collisions of high-energy proton beams. To prepare for data taking in high-luminosity conditions, the ATLAS Tile Hadronic Calorimeter (TileCal) will replace completely on- and off-detector electronics using a new read-out architecture. The TileCal detector signals will be digitized by on-detector electronics and transferred to the TileCal PreProcessors (TilePPr), which comprise the main component of the off-detector electronics. In the TilePPr, the digitized data will be stored in pipeline buffers and be packed and read out to the Front-End LInk eXchange (FELIX) system upon the reception of a trigger decision. FELIX is a new detector readout component being developed as part of the ATLAS upgrade effort. FELIX is designed to act as a data router between the data acquisition detector control and TTC (Timing, Trigger and Control) systems and the new or updated trigger and detector front-end electronics. Whereas previous detector readout implementations relied on diverse custom hardware platforms, the idea behind FELIX is to unify all readout across one well supported and flexible platform.

Conceptual Design of the HL-LHC Hollow Electron Lens Superconducting Magnet System

The Hollow Electron Lens (HEL) units are part of the upgrade baseline of the High-Luminosity LHC accelerator (HL-LHC) and will be installed in the machine ring at point P4 on each counter-rotating LHC proton beamline during a long shutdown in 2025-2027 at CERN. The main goal is to improve the collimation system performance by controlling beam energy loss in the beam halo. The magnet system consists of two 1.6 m long, 5 T superconducting solenoids operating at constant current equipped with steering dipole correctors and fringe field coils which compress the annular low energy e-beam (15 keV) generated from the e^− gun cathode and provide a stable interaction region with the high energy proton beam (7 TeV). Other sets of superconducting solenoids up to 4 T are used for fine-tuning and guiding the electron beam at the extremities of the interaction region on both the gun and the collector side. A standalone dipole compensator is part of the system to correct the net transverse field components up to 0.5 T.m. In this paper, the design progress of the HEL magnet system is presented and discussed.

Fabrication and Test of a 1:4 Scaled HTS Coil for the Defocusing Magnet of 2 GeV FFAG Accelerator

The basic design of a 2 GeV fixed field alternating gradient (FFAG) accelerator was proposed by China Institute of Atomic Energy (CIAE) in 2019. A preliminary study of high temperature superconducting (HTS) magnet for the 2 GeV FFAG accelerator lattice scheme was carried out, considering the beam loss of high energy proton beams and energy efficiency of the main machine. In order to demonstrate the feasibility of manufacturing a spiral-shaped HTS magnet with concave edges based on ReBCO tapes, a 1:4 scaled HTS model magnet is being developed in CIAE. First, the design and fabrication of the 1:4 scaled prototype HTS magnet with concave edges will be described in detail. Then, each double pancake (DP) was tested by liquid nitrogen (LN) immersion. The terminal voltage and magnetic field variation were measured and simulated. Finally, the whole assembled HTS magnet was cooled down to 23 K using helium gas pipeline contact cooling and operated on 300 A for over 24 hours. The central magnetic field reached 719.5 mT, without iron. More detailed electromagnetic characteristics of the magnet during the excitation will be illustrated, which is much helpful for the fabrication of the final full-size HTS magnets.

Acceleration of 60 MeV proton beams in the commissioning experiment of SULF-10 PW laser

We report the experimental results of the commissioning phase in the 10 PW laser beamline of the Shanghai Superintense Ultrafast Laser Facility (SULF). The peak power reaches 2.4 PW on target without the last amplifying during the experiment. The laser energy of 72 ± 9 J is directed to a focal spot of approximately 6 μm diameter (full width at half maximum) in 30 fs pulse duration, yielding a focused peak intensity around 2.0 × 1021 W/cm2. The first laser-proton acceleration experiment is performed using plain copper and plastic targets. High-energy proton beams with maximum cut-off energy up to 62.5 MeV are achieved using copper foils at the optimum target thickness of 4 μm via target normal sheath acceleration. For plastic targets of tens of nanometers thick, the proton cut-off energy is approximately 20 MeV, showing ring-like or filamented density distributions. These experimental results reflect the capabilities of the SULF-10 PW beamline, for example, both ultrahigh intensity and relatively good beam contrast. Further optimization for these key parameters is underway, where peak laser intensities of 1022–1023 W/cm2 are anticipated to support various experiments on extreme field physics.

Radiation shielding assessment of high‐energy proton imaging at a proton therapy facility

BackgroundProton imaging makes use of high‐energy, low‐intensity proton beams that fully traverse the patient and has been suggested to reduce range uncertainty in proton therapy. Upright patient positioning with proton imaging is being considered for a fixed beam room of a new proton therapy facility currently under construction. Considering that the yield and energy spectrum of secondary radiation from high‐energy proton beams is proton beam energy dependent, an assessment of radiation shielding at the energies required for proton imaging should be performed prior to use. Furthermore, NCRP 144 recommends that pion production be considered for proton energies greater than 300 MeV, which are not typically utilized for proton therapy but may be required for proton imaging.PurposeThe purpose of this work was to determine whether proton treatment and imaging with an upright patient positioning system on a fixed beamline were acceptable from a radiation shielding perspective. This is the first report on radiation shielding assessment of proton imaging applications and includes consideration of pion production at the proton beam energy of 330 MeV.MethodsThe Geant4 Monte Carlo toolkit was used for the radiation shielding assessment. The calculations consisted of the generation of secondary particle phase‐space files by simulating the passage of high‐energy proton beams in two target materials, and subsequent simulation of the secondary particles in the proton therapy facility geometry. Particle fluence was converted to operational and protection radiation safety quantities with a custom python script for assessment of instantaneous and annual doses, respectively.ResultsThe total yields of pions from a 330‐MeV proton beam were many orders of magnitude less than that of neutrons and photons. Three‐dimensional maps of ambient dose rate for a 330‐MeV proton beam showed doses arising from secondary neutrons and photons far exceed those arising from pion production. Incorporating representative annual workloads into the calculation demonstrated that proton imaging doses outside the shielded area were negligible compared to those arising from proton therapy.ConclusionsPion production has a negligible impact on the radiation shielding of proton imaging at 330 MeV relative to neutron and photon production. Radiation shielding designed for proton therapy is adequate for high‐energy proton imaging applications.

Determination of Integral Depth Dose in Proton Pencil Beam Using Plane-parallel Ionization Chambers.

PurposeThis study aimed to determine the integral depth-dose curves and assess the geometric collection efficiency of different detector diameters in proton pencil beam scanning.Materials and MethodsThe Varian ProBeam Compact spot scanning system was used for this study. The integral depth-dose curves with a proton energy range of 130 to 220 MeV were acquired with 2 types of Bragg peak chambers: 34070 with 8-cm diameter and 34089 with 15-cm diameter (PTW), multi-layer ionization chamber with 12-cm diameter (Giraffe, IBA Dosimetry), and PeakFinder with 8-cm diameter (PTW). To assess geometric collection efficiency, the integral depth-dose curves of 8- and 12-cm chamber diameters were compared to a 15-cm chamber diameter as the largest detector.ResultsAt intermediate depths of 130, 150, 190, and 220 MeV, PTW Bragg peak chamber type 34089 provided the highest integral depth-dose curves followed by IBA Giraffe, PTW Bragg peak chamber type 34070, and PTW PeakFinder. Moreover, PTW Bragg peak chamber type 34089 had increased geometric collection efficiency up to 3.8%, 6.1%, and 3.1% when compared to PTW Bragg peak chamber type 34070, PTW PeakFinder, and IBA Giraffe, respectively.ConclusionA larger plane-parallel ionization chamber could increase the geometric collection efficiency of the detector, especially at intermediate depths and high-energy proton beams.

Proton acceleration in vacuum using frequency-chirped laser pulses

Recent investigations demonstrate the achievement of protons with energies of several hundred MeV via vacuum laser acceleration mechanisms. However, the symmetric electric field from an unchirped laser pulse is not efficient in generating a high energy proton beam. It is known that a proton can gain energy from a chirped laser pulse through the optimal phase synchronization between the proton and the laser field. In this study, we investigate the proton acceleration by different frequency-chirped laser pulses in vacuum both analytically and numerically. We consider four different situations constituting the unchirped, linear, quadratic, and sinusoidal chirped laser pulses. For the unchirped laser case, the pulse symmetry results in no net energy gain for the proton from the laser field. Conversely, using frequency-chirped laser pulses renders high energy to the proton compared with the unchirped laser pulse. We compared three different chirped cases, and found that a sinusoidal chirped laser pulse renders maximum acceleration to the protons compared to the linear and quadratic chirped situations. There exists an optimal chirp parameter for each type of chirped laser pulse.

High-energy proton beam acceleration driven by an intense ultrarelativistic electron beam in plasma

We report a generation of energetic protons by the interaction of a high-energy electron driving beam with an underdense plasma slab. After an interaction period of approximately 4000 fs, a proton beam with maximum energy greater than 250 MeV can be achieved by applying a driving beam with energy 1.0 GeV to a 200 $\mathrm {\mu }$ m plasma slab. Our two-dimensional particle-in-cell simulations also show that the proton acceleration process can be divided into two stages. In the first stage, a strong positive longitudinal electric field appears near the rear boundary of the plasma slab after the driving beam has passed through it. This acceleration process is similar to the target normal sheath acceleration scheme by the interaction between intense pulsed laser with overdense plasma targets. In the second stage, the accelerated protons experience a long-range acceleration process with a two-stream instability between the high-energy driving beam and the proton beam. Further analyses show that this accelerated proton beam is equipped with the property of good collimation and high energy. This scheme presents a new way for proton or ion acceleration on some special occasions.

Numerical Modeling of Shockwaves Driven by High-Energy Particle Beam Radiation in Tungsten-Made Structures

The investigation of wave propagation in solids requires the development of reliable methods for the prediction of such dynamic events in which the involved materials cover wide ranges of different possible states, governed by plasticity, equation of state, and failure. In the present study, the wave propagation in metals generated by the interaction of high-energy proton beams with solids was considered. In this condition, axisymmetric waves were generated, and, depending on the amount of the delivered energy, different regimes (elastic, plastic, or shock) can be reached. Nonlinear numerical analyses were performed to investigate the material response. The starting point was the energy map delivered into the component as the consequence of the beam impact. The evolution of both hydrodynamic and mechanical quantities was followed starting from the impact and the effects induced on the hit component were investigated. The results showed the portion of the component close to the beam experiences pressure and temperature increase during the deposition phase. The remaining part of the component is traversed by the generated shockwave, which induces high values of strain in a short time or even the failure of the component.

High energy ion beams from the plasma focus

Instability development in the pinch induces a locally enhanced electric field that accelerates the charged particles to extraordinary high energies. Rapid discharge is the singular state of the ion source confirming high plasma impedance. High energy ion beam is correlated to the electrical discharge parameters and consequently the ion acceleration potential is directly related to the mean ion energy. Multi−MeV ions have been measured by magnetic spectrometry and nuclear activation yield-ratio to obtain the ion energy spectra and critically analyze the ion spectrum. A set of magnetic lens arranged in an optimized coil configuration results in medical grade radioactivity of 0.5GBq for a low energy plasma focus. High energy proton beams enables evaluating the sensitivity of link-board components and the error structure identification, with a significant probability of 0.1perproton.

Energy Dependence of Atmospheric Neutron-Induced Failures in Silicon Carbide Power Devices

A time-of-flight measurement technique is used to determine energy-dependent neutron cross sections of silicon carbide power devices exposed to a beam that approximates atmospheric neutrons up to 600 MeV. The Irradiation of Chip Electronics (ICE)-II neutron beam at the Los Alamos Neutron Science Center (LANSCE) is used during these experiments. The measurements show that a wide range of neutron energies are likely to cause device failures close to the rated voltage, from neutron interactions with lattice atoms within the active device volume. The data indicate that the energy-dependent cross sections are relatively large, revealing a high probability for a few percent of the neutron–lattice atom interactions to give rise to a failure when the device is biased close to its rated voltage. Additionally, knowledge of the neutron energies and associated cross sections giving rise to failures within these devices provide insights regarding the critical charges and the sensitive volumes of these devices as a function of neutron energy for single-event burnouts. Lastly, the energy-dependent cross sections provide a preliminary set of data to calculate a correlation factor between failure rates obtained using a broad energy neutron source, and the commonly used mono-energetic high-energy proton beams, utilized due to their wider availability for determining bias dependent failure-in-time curves.

Estimating the percentage of patients who might benefit from proton beam therapy instead of X-ray radiotherapy.

High-energy Proton Beam Therapy (PBT) commenced in England in 2018 and NHS England commissions PBT for 1.5% of patients receiving radical radiotherapy. We sought expert opinion on the level of provision. Invitations were sent to 41 colleagues working in PBT, most at one UK centre, to contribute by completing a spreadsheet. 39 responded: 23 (59%) completed the spreadsheet; 16 (41%) declined, arguing that clinical outcome data are lacking, but joined six additional site-specialist oncologists for two consensus meetings. The spreadsheet was pre-populated with incidence data from Cancer Research UK and radiotherapy use data from the National Cancer Registration and Analysis Service. 'Mechanisms of Benefit' of reduced growth impairment, reduced toxicity, dose escalation and reduced second cancer risk were examined. The most reliable figure for percentage of radical radiotherapy patients likely to benefit from PBT was that agreed by 95% of the 23 respondents at 4.3%, slightly larger than current provision. The median was 15% (range 4-92%) and consensus median 13%. The biggest estimated potential benefit was from reducing toxicity, median benefit to 15% (range 4-92%), followed by dose escalation median 3% (range 0 to 47%); consensus values were 12 and 3%. Reduced growth impairment and reduced second cancer risk were calculated to benefit 0.5% and 0.1%. The most secure estimate of percentage benefit was 4.3% but insufficient clinical outcome data exist for confident estimates. The study supports the NHS approach of using the evidence base and developing it through randomised trials, non-randomised studies and outcomes tracking. Less is known about the percentage of patients who may benefit from PBT than is generally acknowledged. Expert opinion varies widely. Insufficient clinical outcome data exist to provide robust estimates. Considerable further work is needed to address this, including international collaboration; much is already underway but will take time to provide mature data.

Quasimonoenergetic Proton Acceleration via Quantum Radiative Compression

Dense high-energy monoenergetic proton beams are vital for wide applications, thus modern laser-plasma-based ion-acceleration methods are aiming to obtain high-energy proton beams with energy spread as low as possible. In this work, we put forward a quantum radiative compression method to postcompress a highly accelerated proton beam and convert it to a dense quasimonoenergetic one. We find that when the relativistic plasma produced by radiation-pressure acceleration collides head on with an ultraintense laser beam, large-amplitude plasma oscillations are excited due to quantum radiation reaction and the ponderomotive force, which induce compression of the phase space of protons located in its acceleration phase with negative gradient. Our three-dimensional spin-resolved quantum electrodynamics (QED) particle-in-cell simulations show that hollow-structure proton beams with a peak energy approximately $\mathrm{GeV}$, relative energy spread of few percents, and number ${N}_{p}\ensuremath{\sim}{10}^{10}$ (or ${N}_{p}\ensuremath{\sim}{10}^{9}$ with a $1\mathrm{%}$ energy spread) can be produced in near-future laser facilities, which may fulfill the requirements of alternative applications, such as, for radiography of ultrathick dense materials, or as injectors of hadron colliders.

Imaging and reconstruction of high-energy proton beam spot before target based on secondary gamma rays.

The distribution and stability of the incident proton beam spot are critical for the stable operation of a high-power spallation target. This study proposes a method to capture images of the incident proton beam spot based on secondary gamma rays. The distribution of the backward secondary gamma rays irradiated by the primary proton beam on the incident surface of the target is close to the distribution of the protons and can be measured at a low-radiation position far from the target area. A relation of distributions between the incident protons and the secondary gammas is constructed by using the point response function of this pinhole imaging system. The proposed method of imaging is suitable for monitoring the distribution of the proton beam on the target in facilities that use a beam power of several megawatts or tens of megawatts, such as spallation neutron sources or accelerator-driven subcritical systems.

Incidence of Phage Capsid Organization on the Resistance to High Energy Proton Beams

The helical geometry of virus capsid allows simple self-assembly of identical protein subunits with a low request of free energy and a similar spiral path to virus nucleic acid. Consequently, small variations in protein subunits can affect the stability of the entire phage particle. Previously, we observed that rearrangement in the capsid structure of M13 engineered phages affected the resistance to UV-C exposure, while that to H2O2 was mainly ascribable to the amino acids’ sequence of the foreign peptide. Based on these findings, in this work, the resistance to accelerated proton beam exposure (5.0 MeV energy) of the same phage clones was determined at different absorbed doses and dose rates. Then, the number of viral particles able to infect and replicate in the natural host, Escherichia coli F+, was evaluated. By comparing the results with the M13 wild-type vector (pC89), we observed that 12III1 phage clones, with the foreign peptide containing amino acids favorable to carbonylation, exhibited the highest reduction in phage titer associated with a radiation damage (RD) of 35 × 10−3/Gy at 50 dose Gy. On the other hand, P9b phage clones, containing amino acids unfavorable to carbonylation, showed the lowest reduction with an RD of 4.83 × 10−3/Gy at 500 dose Gy. These findings could improve the understanding of the molecular mechanisms underlying the radiation resistance of viruses

High intensity proton beam impact at 440 GeV/c on Mo and Cu coated CfC/graphite and SiC/SiC absorbers for beam intercepting devices

Beam Intercepting Devices (BIDs) are essential protection elements for the operation of the Large Hadron Collider (LHC) complex. The LHC internal beam dump (LHC Target Dump Injection or LHC TDI) is the main protection BID of the LHC injection system; its main function is to protect LHC equipment in the event of a malfunction of the injection kicker magnets during beam transfer from the SPS to the LHC. Several issues with the TDI were encountered during LHC operation, most of them due to outgassing from its core components induced by electron cloud effects, which led to limitations of the injector intensity and hence had an impact on LHC availability. The absorbing cores of the TDIs, and of beam intercepting devices in general, need to deal with high thermo-mechanical loads induced by the high intensity particle beams. In addition, devices such as the TDI — where the absorbing materials are installed close to the beam, are important contributors to the accelerator impedance budget. To reduce impedance, the absorbing materials that make up the core must be typically coated with high electrical conductivity metals. Beam impact testing of the coated absorbers is a crucial element of development work to ensure their correct operation.In the work covered by this paper, the behaviour of several metal-coated absorber materials was investigated when exposed to high intensity and high energy proton beams in the HiRadMat facility at CERN. Different coating configurations based on copper and molybdenum, and absorbing materials such as isostatic graphite, Carbon Fibre Composite (CfC) and Silicon Carbide reinforced with Silicon Carbide fibres (SiC-SiC), were tested in the facility to assess the TDI's performance and to extract information for other BIDs using these materials. In addition to beam impact tests and an extensive Post Irradiation Examination (PIE) campaign to assess the performance of the coatings and the structural integrity of the substrates, extensive numerical simulations were carried out.

Measurement of medium-energy proton flux

<sec>Proton is the main particle component in the space radiation environment. The proton single event effect cannot be ignored with the continuous development of semiconductor technology. Accelerator simulation is the most important method to evaluate the single event effect caused by proton radiation, and the accurate measurement of proton flux is the most critical aspect in the device evaluation process. The research is based on the 100 MeV proton single-event irradiation device of the Atomic Energy Institute, which breaks through the wide-range mid-energy proton fluence rate measurement technology. The detection tools are developed such as Faraday cup, plastic scintillator detectors and secondary electron emission monitors, which can be used for measuring the proton beam current in a wide range. Faraday cup and plastic scintillator detector can be used for measuring the high flux proton and the low flux proton, respectively. Secondary electron emission monitor can be used for conducting the online real-time measurement. The proton fluxes in a range of 10<sup>6</sup>– 10<sup>7</sup> p·cm<sup>–2</sup>·s<sup>–1</sup> are measured by using two separate detectors.</sec><sec>The analysis of the fluence rate uncertainty is carried out. The uncertainty of measurement results mainly include three aspects: measurement method, measuring instrument and equipment, and repeatability of multiple measurement results. Here in this work, the Faraday cup is taken for example to analyze the uncertainty sources in the proton flux measurement. The measurement methods include the calculation of the collection efficiency of the Faraday cup (collection efficiency + escape rate = 1) and the calculation method of flux (flux = current/collection area). For the measuring instruments and equipment, mainly including 6517A and other electronic devices, their errors are determined by the accuracies of the instruments themselves. Repeatability of multiple measurement results mainly from the error caused by the instability of the accelerator beam output, the error caused by randomness of multiple measurement results, and the error given by the statistical method. The analysis shows that the uncertainty of flux measurement by Faraday cup is 7.26%, and the uncertainty of flux measurement by plastic scintillator detector is 1.64%.</sec><sec>The flux measurement of the proton fluence rate has reached the level of similar devices in the world, filling the gap in this field in China. It has a certain reference and guiding significance for the follow-up study of medium- and high-energy proton beam measurement in China. The mid-energy proton flux measurement system and uncertainty analysis method established in this study lay the foundation for accurately evaluating the component radiation effects.</sec>

New method for production of 155Tb via 155Dy by irradiation of natGd by medium energy alpha particles

Introduction155Tb (T1/2 = 5.32 d) is considered both as a promising Auger electron emitter and as a diagnostic pair for other therapeutic terbium radionuclides. Despite several methods for its production proposed, it remains scarcely available. Most of the methods using low-energy protons and deuterons beams result in a high content of radionuclidic impurities. High purity 155Tb can be obtained using high-energy proton beams combined with online mass separation of products, but the method remains inaccessible to most potential consumers. We have proposed an indirect method for the production of 155Tb via formation of 155Dy (T1/2 = 9.9 h), which can be implemented using medium energy alpha particles beam. MethodsGadolinium oxide targets of natural isotopic composition were irradiated by 60 MeV alpha particles beam on a U-150 cyclotron of the National Research Center “Kurchatov Institute”. The cross sections of nuclear reactions were measured by the stack foil technique, detecting the gamma radiation of the activation products. Gd, Tb, and Dy were separated by extraction chromatography using the LN Resin sorbent in nitric media. The isolated dysprosium fraction was stored for a day, and the formed 155Tb was isolated by the same method. ResultsThe cross sections for the formation of 159Gd, 153-156Tb, and 155,157Dy under irradiation by alpha particles of a gadolinium target of natural isotopic composition in the energy range 20–60 MeV have been measured. The 155Dy yield on a thick target at 60 MeV was 35 MBq/μAh, which makes it possible to obtain 1 GBq 155Tb as a result of 12-hour irradiation with a beam current of 50 μA. Extraction chromatography on LN Resin sorbent in nitric enabled quick and efficient separation of Gd, Tb, and Dy. The radiochemical yield of Dy was 95%, for Tb > 95%. The main radionuclidic impurity is 153Tb (T1/2 = 2.34 d; <5.4% of 155Tb activity). ConclusionsThe developed method allows the production of therapeutic amounts of 155Tb with acceptable radionuclidic purity without the need for isotopically enriched materials.The amount of 155Tb is sufficient for its use in Auger therapy, as well as for preclinical studies of the suitability of SPECT preparations in laboratory animals. Nevertheless, to obtain higher activities, a longer irradiation time and a higher projectile current are proposed.The 153Tb radionuclide present in the final preparation has a shorter half-life than the target radionuclide, and its hard γ-lines have a probability of emission of less than 1%, from which it can be concluded that the negative effect will not be significant. However, a product of this purity and type of contamination requires additional testing for toxicity in living organisms. The final sample also includes a certain amount of 157Tb (T1/2 = 71 a, the only γ-line 54.5 keV Iγ = 0.0084%), which will complicate the labeling conditions. Thus, more research is needed in the labeling area.It should be noted that the use of gadolinium enriched in the 155Gd or 156Gd nuclide as a target will help not only reduce the amount of impurities but also increase the yield of 155Tb.

A New Low-Energy Proton Irradiation Facility to Unveil the Mechanistic Basis of the Proton-Boron Capture Therapy Approach

Protontherapy (PT) is a fast-growing cancer therapy modality thanks to much-improved normal tissue sparing granted by the charged particles’ inverted dose-depth profile. Protons, however, exhibit a low biological effectiveness at clinically relevant energies. To enhance PT efficacy and counteract cancer radioresistance, Proton–Boron Capture Therapy (PBCT) was recently proposed. PBCT exploits the highly DNA-damaging α-particles generated by the p + 11B→3α (pB) nuclear reaction, whose cross-section peaks for proton energies of 675 keV. Although a significant enhancement of proton biological effectiveness by PBCT has been demonstrated for high-energy proton beams, validation of the PBCT rationale using monochromatic proton beams having energy close to the reaction cross-section maximum is still lacking. To this end, we implemented a novel setup for radiobiology experiments at a 3-MV tandem accelerator; using a scattering chamber equipped with an Au foil scatterer for beam diffusion on the biological sample, uniformity in energy and fluence with uncertainties of 2% and 5%, respectively, was achieved. Human cancer cells were irradiated at this beamline for the first time with 685-keV protons. The measured enhancement in cancer cell killing due to the 11B carrier BSH was the highest among those thus far observed, thereby corroborating the mechanistic bases of PBCT.

On fusion chain reactions in 11B targets for laser driven aneutronic fusion

The work presented in this letter suggests that it is possible to enhance the yield in laser driven aneutronic fusion devices by fusion chain reactions. This mechanism will be described using the example of aneutronic fusion between an incoming high-energy proton beam and a 11B target. Such fusion reactions create alphas that can again fuse with a 11B particle in a dense solid state target. An improved target design will be shown that enhances the recycling of fast alpha particles that are created from fusion reactions. It will also be argued that such alpha recycling may have already been observed in experiments, although it was attributed to another, more complex physical mechanism.