Proton Beam Current Research Articles

Исследование влияния пространственного заряда на транспортировку 2 MeV пучка протонов в ускорительном источнике эпитепловых нейтронов

A neutron source comprised of a vacuum insulated tandem accelerator and a solid lithium target is in operation for development of boron neutron capture therapy and other applications. The size of the proton beam on the target surface depending on the proton beam current was measured using an infrared camera and thermocouples inserted inside the target. The absence of a noticeable influence of the space charge on the transportation of the proton beam from the accelerator to the target at a distance of 5 m has been established, which simplifies the operation of the neutron source.

Neutronics design for molten salt accelerator-driven system as TRU burner

Treatment of plutonium separated from spent fuel has been one of the most important issues in the utilization of nuclear power in Japan. This study investigates a molten salt accelerator-driven system (ADS) to transmute transuranic (TRU) nuclides to address the issue. This study proposes the MARDS (Molten salt AcceleratoR Driven System) concept which has four features: employment of chloride, no dedicated spallation target, non-contact between beam window and fuel salt and modularized core. Neutronics calculation for the MARDS concept was performed for a condition of 400 MW thermal power with 800 MeV proton beam. The calculation results showed that the maximum proton beam current was about 7 mA and about 100–120 kg plutonium could be transmuted during one-year operation. The result indicates that the MARDS concept can employ a circular accelerator instead of LINAC and transmute TRU effectively.

Proton beam position measurement in air using a BPM

A Beam Position Monitor (BPM) is potentially useful to measure the position and phase of the beam in air in a non-destructive way. An air-gap BPM in experiments, such as beam-induced radioactive waste management and dynamic radiography applications, where a so-called air gap is needed, can be utilized to measure the beam position and phase. In this study, a stripline BPM was used in the air-gap of an 800 MeV proton beam transport line. The downstream end of the primary beamline exit window was made of a thin aluminum plate and allowed the beam to travel 1.2 m in ambient air before re-entering into a vacuum drift section. Such a configuration was arranged to examine the BPM effectiveness in atmospheric temperature and pressure where ionization of air occurs. In this study, a high energy (800 MeV), high current (0.6 A beam peak current/pulse) proton beam of 5 mm radius was transported in the air. The beam position relative to the axis was measured by detecting the signature of the beam in a nanosecond scale. This nanosecond scale detection ability was useful to identify other signals such as plasma effects. The BPM signals were processed at a frequency of 201 MHz; thus, one gets a stronger response in a stripline pattern as it was used in this study instead of a dot-type BPM. Experimental data show that the BPM works well in air, but ionization of air or plasma formation could not be measured over the BPM signal. The design, construction, and performance of a BPM in air environment are presented.

Experimental study of an initially pressurized water target irradiated by a proton beam

This experimental visualization study was conducted to investigate and define the phenomena of an initially pressurized liquid water target that can prevent the boiling of water when the target is irradiated with a 30-MeV proton beam produced using the MC-50 Cyclotron at Korea Institute of Radiological and Medical Sciences. At various initial pressures and proton beam currents, the behavior of the target water was investigated using a complementary metal–oxide–semiconductor camera. We confirmed that an appropriate initial pressure could indeed prevent local bulk boiling, and be determined by solving Rayleigh's equation and the Clausius–Clapeyron equation for homogeneous bubble growth using the measured bubble size generated at the Bragg-peak region. The saturation temperature of the initial pressure must be higher than the calculated local water temperature at the Bragg-peak region. The final pressure of the water target increased proportionally with the initial pressure and proton beam current. The penetration depth of the beam varied with beam current and slightly with the final pressure, as evidenced by the emission of blue light in all experimental cases.

Radiation shielding design requirement in the proton energy measurement facility at DECY-13 cyclotron

The DECY-13 cyclotron is expected to produce a maximum energy of protons beam of 13 MeV. For testing the proton energy, a device for measuring photon energy using a stacked copper foil activation technique is currently being constructed. The activation caused the collision of a proton with copper foils and reactions of 63Cu(p,n)63Zn and 65Cu(p,n)65Zn have happened. These nuclear reactions produce neutron and gamma radiations; therefore, a study of radiation safety aspects is required to protect the hazard in the experiment of proton energy measurement. The study consists of designing for shielding construction based on radiation safety criteria and mainly determining the thickness of the shielding. The shielding material was portland cement concrete of K500 with a density of 2.3 gr/cm3. By setting a safe maximum dose rate of 50 mSv/year in the position of 350 cm from the neutron radiation source and the proton beam current was taken 1 μA, the required minimum thickness of concrete shielding was 110 cm.

FLUKA Simulation of Ac-225 Production with a Medical Cyclotron

Alpha-emitting Ac-225 is a radionuclide being developed and used in the treatment of some cancers [1]. Currently, the Department of Energy (DOE) isotope program’s Tri-Lab Effort (Brookhaven National Laboratory, Oak Ridge National Laboratory, Los Alamos National Laboratory) effort provides Ac-225 from a Thorium target irradiated with a high energy proton beam [2]. We have a plan to make Ac-225 from Ra-226 target using the relatively low energy proton beam from a medical cyclotron. FLUKA is a general-purpose Monte Carlo simulation code used to model the interaction and transport of particles from a few KeV to thousands of TeV in arbitrary materials. It is built and maintained with the aim of including the best possible physical models in terms of completeness and precision [3]. In this study, we are using the RESNUCLEi card to score the residual isotopes and activities from the Ra-226 target irradiated in the EBCO TR19 cyclotron. For the simulation, we used 300 mg of Ra-226 (5.0 g/cm3) which is 8.0E+20 atoms. These atoms can be deposited as a 0.0086 cm thick layer on a 1.58 X 4.45 X 0.234 cm aluminum plate. The Ra-226 target geometry is specially designed to fit the solid target holder for the EBCO TR19 cyclotron. The EBCO TR19 cyclotron proton beam energy range is from 13 to 19 MeV and the beam current is 200 μA (1.248E+15 protons/s). At 19 MeV, the highest proton beam energy, protons can penetrate 0.198 cm of Ra-226 (13 MeV, 0.106 cm) and 0.192 cm of aluminum. Thus, the proton beam penetrates the radium layer and is completely stopped in the aluminum plate. Ra-226 target irradiations were simulated using a 40 hours irradiation time using a varied particle energy from 13 to 19 MeV and 200 μA proton beam currents to find the best conditions for Ac-225 production in the EBCO TR19 cyclotron. The maximum yield for the Ac-225 production was obtained at the beam energy 14.5 MeV. The amount of the produced Ac-225 from Ra-226 target is about 340 mCi at EOB. [1]David A. Scheinberg and Michael R. McDevit. Actinium-225 in targeted alpha-particle therapeutic applications. Curr Radiopharm. 2011 Oct; 4(4): 306–320.[2]The Journey of Actinium-225: How Scientists Discovered a New Way to Produce a Rare Medical Radioisotope. DOE News. https://science.energy.gov/news/featured-articles/2018/06-20-18/[3]Giuseppe Battistoni et al. Overview of the FLULA code. Annals of Nuclear Energy. 2015 Aug. Vol 82, Pages 10-18. This research supported by the Department of Energy Office of Science’s Isotope Program.

Proton Beam Production of Curie Scale Ac-225 at 100 MeV and Below

The DOE National Isotope Program for radionuclide production operates two intermediate energy, high intensity accelerator-based production facilities: The 100 MeV Isotope Production Facility (IPF) at Los Alamos National Laboratory and the 200 MeV Brookhaven Linac Isotope Producer (BLIP). They are two of only eight intermediate energy production facilities worldwide and often operate with record breaking beam intensities on target. These two facilities will be used for year-round Ci-scale batch production of Ac-225 via proton bombardment of thorium targets. High power targetry for this purpose is being developed as part of the US DOE Tri-Lab production development effort. Production cross sections measured in recent years dictate that Ci-scale production at a 100 MeV facility such as IPF requires much higher beam currents than at higher energy facilities such as BLIP. As a result, targets used for production at these lower energies must withstand power levels that are higher by a factor that approaches an order of magnitude. While existing target designs have been used to successfully produce up to ∼200 mCi at end-of-bombardment, improvements are needed to achieve Ci-scale production. As part of the US DOE Tri-Lab effort, ultra-high power thorium targets are being developed to withstand 100 MeV proton beam currents up to 450 μA. Based on thermal model predictions, a major emphasis is placed on the enhancement of thermal contact between the thorium target and its containment. Several enhancement approaches and techniques are being explored with the goal to down select and integrate the most appropriate technique into a procedure for the routine fabrication of IPF targets. This presentation will provide a status update on the ongoing targetry R&D effort to achieve Ci-scale production. In the context of recent upgrades at IPF, updated Ac-225 production projections will also be presented based on expected target thermal performance at ultra-high beam currents and yields obtained from recent pilot Ac-225 production campaigns.

Fluorine determination in biological and environmental samples with INAA using fast neutrons from a p(19 MeV) + Be neutron generator

We present a new activation method based on the 19F(n,2n)18F reaction using fast neutrons produced by a p(19 MeV) + Be accelerator-driven fast neutron source providing continuous neutron spectrum up to 17 MeV with a neutron fluence rate of approximately 9 × 1010 cm−2 s−1 at a 12-µA proton beam current. We describe elimination of interferences in measurement of 18F, a pure positron emitter with T1/2 = 1.83 h. We present results of fluorine determination for several biological and environmental reference materials with the new procedure and compare them with those achieved by other methods in terms of limits of detection, accuracy and precision, where available.

Isotope production by the high current proton beam of CYCIAE-100

CYCIAE-100, a 100 MeV high current compact cyclotron has been constructed and first beams were extracted in 2014. The machine has 5 beam lines for multi-application purposes. N1, one of the beam lines, is designed for high current beam transportation, for beam dump tests and isotope production. In 2016, a mA proton beam was tested on the internal target. In 2017 and 2018, 200 μA and 520 μA proton beams were extracted and transported to the beam dump respectively. In addition to increasing the cw beam power of 52 kW extracted from the machine and transported to the beam dump, this paper will also present the simultaneous dual-beam extraction from CYCIAE-100 and the improvement of the uniformity of the beam spot on the target, which will benefit isotope production.

Experimental demonstration of a laser proton accelerator with accurate beam control through image-relaying transport

A compact laser plasma accelerator (CLAPA) that can stably produce and transport proton ions with different energies less than 10 MeV, $l1%$ energy spread, several to tens of pC charge, is demonstrated. The high current proton beam with continuous energy spectrum and a large divergence angle is generated by using a high contrast laser and micron thickness targets, which later is collected, analyzed and refocused by an image-relaying beam line using a combination of quadrupole and bending electromagnets. It eliminates the inherent defects of the laser-driven beams, realizes precise manipulation of the proton beams with reliability, availability, maintainability and inspectability (RAMI), and takes the first step towards applications of this new generation of accelerator. With the development of high-rep rate Petawatt (PW) laser technology, we can now envision a new generation of accelerator for many applications in the near future soon.

Proton Beam Production of Curie Scale Ac-225 at 100 MeV and Below

The DOE National Isotope Program for radionuclide production operates two intermediate energy, high intensity accelerator-based production facilities: The 100 MeV Isotope Production Facility (IPF) at Los Alamos National Laboratory and the 200 MeV Brookhaven Linac Isotope Producer (BLIP). They are two of only eight intermediate energy production facilities worldwide and often operate with record breaking beam intensities on target. These two facilities will be used for year-round Ci-scale batch production of Ac-225 via proton bombardment of thorium targets. High power targetry for this purpose is being developed as part of the US DOE Tri-Lab production development effort. Production cross sections measured in recent years dictate that Ci-scale production at a 100 MeV facility such as IPF requires much higher beam currents than at higher energy facilities such as BLIP. As a result, targets used for production at these lower energies must withstand power levels that are higher by a factor that approaches an order of magnitude. While existing target designs have been used to successfully produce up to ∼200 mCi at end-of-bombardment, improvements are needed to achieve Ci-scale production. As part of the US DOE Tri-Lab effort, ultra-high power thorium targets are being developed to withstand 100 MeV proton beam currents up to 450 μA. Based on thermal model predictions, a major emphasis is placed on the enhancement of thermal contact between the thorium target and its containment. Several enhancement approaches and techniques are being explored with the goal to down select and integrate the most appropriate technique into a procedure for the routine fabrication of IPF targets. This presentation will provide a status update on the ongoing targetry R&D effort to achieve Ci-scale production. In the context of recent upgrades at IPF, updated Ac-225 production projections will also be presented based on expected target thermal performance at ultra-high beam currents and yields obtained from recent pilot Ac-225 production campaigns.

Innovative Target for Production of Technetium-99m by Biomedical Cyclotron.

Technetium-99m (99mTc) is the most used radionuclide worldwide in nuclear medicine for diagnostic imaging procedures. 99mTc is typically extracted from portable generators containing 99Mo, which is produced normally in nuclear reactors as a fission product of highly enriched Uranium material. Due to unexpected outages or planned and unplanned reactor shutdown, significant 99mTc shortages appeared as a problem since 2008 The alternative cyclotron-based approach through the 100Mo(p,2n)99mTc reaction is considered one of the most promising routes for direct 99mTc production in order to mitigate potential 99Mo shortages. The design and manufacturing of appropriate cyclotron targets for the production of significant amounts of a radiopharmaceutical for medical use is a technological challenge. In this work, a novel solid target preparation method was developed, including sputter deposition of a dense, adherent, and non-oxidized Mo target material onto a complex backing plate. The latter included either chemically resistant sapphire or synthetic diamond brazed in vacuum conditions to copper. The target thermo-mechanical stability tests were performed under 15.6 MeV proton energy and different beam intensities, up to the maximum provided by the available GE Healthcare (Chicago, IL, USA) PET trace medical cyclotron. The targets resisted proton beam currents up to 60 µA (corresponding to a heat power density of about 1 kW/cm2) without damage or Mo deposited layer delamination. The chemical stability of the proposed backing materials was proven by gamma-spectroscopy analysis of the solution obtained after the standard dissolution procedure of irradiated targets in H2O2.

Dielectric-Filled Reentrant Cavity Resonator as a Low-Intensity Proton Beam Diagnostic

Measurement of the proton beam current (0.1–40 nA) at the medical treatment facility PROSCAN at the Paul Scherrer Institut (PSI) is performed with ionization chambers. To mitigate the scattering issues and to preserve the quality of the beam delivered to the patients, a non-interceptive monitor based on the principle of a reentrant cavity resonator has been built. The resonator with a fundamental resonance frequency of 145.7 MHz was matched to the second harmonic of the pulse repetition rate (72.85 MHz) of the beam extracted from the cyclotron. This was realized with the help of ANSYS HFSS (High Frequency Structural Simulator) for network analysis. Both, the pickup position and dielectric thickness were optimized. The prototype was characterized with a stand-alone test bench. There is good agreement between the simulated and measured parameters. The observed deviation in the resonance frequency is attributed to the frequency dependent dielectric loss tangent. Hence, the dielectric had to be resized to tune the resonator to the design resonance frequency. The measured sensitivity performances were in agreement with the expectations. We conclude that the dielectric reentrant cavity resonator is a promising candidate for measuring low proton beam currents in a non-destructive manner.

Investigation of production of medical 82Sr and 68Ge for 82Sr/82Rb and 68Ge/68Ga generators via proton accelerator

How to operate 82Sr/82Rb and 68Ge/68Ga generators used in the positron emission tomography scan process is explained, and the importance of 82Sr and 68Ge radionuclides for these generators is revealed. To produce medical 82Sr and 68Ge by means of a proton accelerator in an irradiation time of 24 h, a proton beam current of 250 µA, and an energy range Eproton = 100 → 5 MeV, the cross sections and the neutron emission spectrum curves of (p,xn) reaction processes on Rb-85, Ga-69 and Ga-71 targets were calculated, and the activities and yields of the product were simulated for the reaction processes. Additionally, the integral yields of the reaction processes were determined via the calculated cross-sectional curves and the mass stopping power obtained from the X-PMSP program. Furthermore, based on the obtained results, the appropriate reaction processes for the production of 82Sr and 68Ge isotopes on Rb-85, Ga-69, and Ga-71 targets are discussed.

Transverse profile tomography of a high current proton beam with a multi-wire scanner

This paper describes the measurement of the transverse, two-dimensional profile of the high current proton beam in the linac at the Tsinghua University, by tomography mapping using a rotatable multi-wire scanner. The experiment is conducted at a beam energy of 3 MeV, a peak current of up to 32 mA, a repetition frequency of 20 Hz, and a beam pulse width of $50\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$. The transverse density distribution is reconstructed utilizing the algebraic reconstruction technique (ART), by using the beam profiles measured at different rotation angles. The beam profile, measured at a fixed rotation angle, is obtained by 19 parallel carbon wires mounted on one board of the wire scanner monitor (WSM) moving along a straight line with a step increment of 0.1 mm. The results gathered from the computer tomography (CT) method could be verified by an independent profile measurement downstream of a multiple-slit aperture. This paper presents first measurement results of the high current proton beam during normal operation of the linac at the Tsinghua University. A dynamic range of $1{0}^{2}$ for the two-dimensional distribution was achieved.

Research and development activities for accelerator-driven system in JAEA

The Japan Atomic Energy Agency (JAEA) has investigated an accelerator-driven system (ADS) to transmute minor actinides which will be partitioned from the high level waste. There are various inherent issues for the research and development on the ADS. The recent two activities to realize a feasible and reliable ADS concept are introduced in this paper.For the feasibility, the design of a beam window which is a boundary of the accelerator and the subcritical core, is one of the most important issues. To mitigate the design condition of the beam window, namely to reduce the necessary proton beam current, the subcritical core concept with subcriticality adjustment rods was investigated. Through the coupled analysis of neutronics, particle transport, thermal-hydraulics and structure, a feasible beam window concept was presented.For the reliability, a beam-trip is the inherent and serious issue for the ADS design because it induces a rapid temperature change in structures in the subcritical core. In the previous study, the beam-trip frequency of the ADS accelerator was estimated based on the operation data of the existing accelerators. To minimize the beam-trip frequencies, a double-accelerator concept was proposed and its beam-trip frequency was estimated. The results indicated that the double-accelerator concept was useful to realize reliable accelerator operation for the ADS although the cost of the accelerators and those buildings would be double.

Conceptual design study of beam window for accelerator-driven system with subcriticality adjustment rod

The design of the beam window of the spallation target is one of the critical issues in the accelerator-driven system (ADS) design. This study aims to perform the coupled analysis for the feasible beam window concept. To mitigate the design condition, namely to reduce the necessary proton beam current, subcriticality adjustment rod (SAR) was installed to the ADS core. The burnup analysis was performed for the ADS core with SAR and the results indicated that the maximum proton beam current during the burnup cycle was reduced from 20 to 13.5 mA.Based on the burnup analysis result, the coupled analysis; particle transport, thermal hydraulics and structural analyses, was performed. As the final result, the most robust beam window design; the hemisphere shape, the outer radius = 235 mm, the thickness at the top of the beam window = 3.5 mm and the factor of safety for the buckling = 9.0, was presented. The buckling pressure was 2.2 times larger than the previous one and more feasible beam window concept was presented through this study.

Simulated production rates of exotic nuclei from the ion guide for neutron-induced fission at IGISOL

.An investigation of the stopping efficiency of fission products, in the new ion guide designed for ion production through neutron-induced fission at IGISOL in Jyväskylä, Finland, has been conducted. Our simulations take into account the new neutron converter, enabling measurements of neutron-induced fission yields, and thereby provide estimates of the obtained yields as a function of primary proton beam current. Different geometries, targets, and pressures, as well as models for the effective charge of the stopped ions were tested, and optimisations to the setup for higher yields are suggested. The predicted number of ions stopped in the gas lets us estimate the survival probability of the ions reaching the downstream measurements stations.

Effect of high-energy neutron source on predicting the proton beam current in the ADS design

Abstract The accelerator-driven subcritical system (ADS) is driven by a neutron source from spallation reactions introduced by the injected proton beam. Part of the neutron source has energy as high as a few hundred MeV to a few GeV. The effects of high-energy source neutrons (E n > 20 MeV) are usually approximated by energy cut-off treatment in practical core calculations, which can overestimate the predicted proton beam current in the ADS design. This article intends to quantize this effect and propose a way to solve this problem. To evaluate the effects of high-energy neutrons in the subcritical core, two models are established aiming to cover the features of current experimental facilities and industrial-scale ADS in the future. The results show that high-energy neutrons with E n > 20 MeV are of small fraction (2.6%) in the neutron source, but their contribution to the source efficiency is about 23% for the large scale ADS. Based on this, a neutron source efficiency correction factor is proposed. Tests show that the new correction method works well in the ADS calculation. This method can effectively improve the accuracy of the prediction of the proton beam current.

Impact of impurity in transmutation cycle on neutronics design of revised accelerator-driven system

Partitioning and transmutation technology will be a promising technology to reduce the burden of the geological disposal of the high-level radioactive waste. The Japan Atomic Energy Agency has investigated a lead-bismuth eutectic cooled accelerator-driven system (ADS) to transmute minor actinides (MAs) in the transmutation cycle. This study aims to revise the ADS design and to investigate the impact of impurities in the transmutation cycle on the ADS neutronics design.The impact of impurities in the transmutation cycle is investigated for the revised design. For the uranium from the partitioning, the accompaniment of 20wt% U against the Pu weight is acceptable although the MA transmutation amount will be decreased slightly. For the rare earth (RE) from the partitioning, the accompaniment of 5wt% RE against the MA weight is allowable. In the reprocessing, the decontamination factor, DF=10 for RE is enough from the viewpoint of the neutronics design. The impact of the fuel composition accuracy is also investigated. The uncertainty of the ZrN ratio against the MA fuel should be less than 0.2% to minimize a surplus proton beam current due to the uncertainty.Through these investigations, the required conditions for the impurities in the partitioning, the MA fuel fabrication and the reprocessing processes were clarified from the viewpoint of the ADS neutronics design.