mA Proton Research Articles

Rapid fabrication and dissolution of pressed 58Ni/Mg matrix targets for 55Co production

BackgroundBeyond the use of conventional short-lived PET radionuclides, there is a growing interest in tracking larger biomolecules and exploring radiotheranostic applications. One promising option for imaging medium-sized molecules and peptides is ⁵⁵Co (T₁/₂ = 17.5 h, β⁺ = 76%), which enables imaging of new and already established tracers with blood circulation of several hours. Additionally, ⁵⁵Co can be paired with the Auger-Meitner emitter 58mCo (T₁/₂ = 9 h, 100% IC) for radiotheranostic applications. Here we report on 55Co production via the 58Ni(p,α)55Co reaction channel using pressed 58Ni and Mg matrix targets.ResultsThis set up is capable to produce and isolate 240 ± 20 MBq [55Co]Co+ 2 (80% RCY) with 4 ml 0.25 M HEPES at 35 min post End Of Bombardment for 3 h, 25 µA protons irradiation. The RNP of the eluate is 99.98 ± 0.014% as measured 2 h & 17 h post EOB. AMA was determined to 1.5 ± 0.5 GBq/µmol [55Co]Co-DOTA at EOB. Mg dissolves rapidly in the acid mixture, leaving behind a porous, sponge-like Ni matrix increasing the surface area of the Ni and therefore accelerating the dissolution.ConclusionWe present a novel, simple, and rapid method to produce ⁵⁵Co with pressed ⁵⁸Ni/Mg matrix targets enabling faster target fabrication and dissolution. By using a simple hydraulic press, mechanically stable target coins useful for solid target irradiation are fabricated within 5 min and can be dissolved in 10 min at room temperature. The foils remain intact after irradiation and can endure irradiation conditions providing sufficient activity (> 200 MBq) for clinical doses. The method presented here using Mg as a support metal for fixation of the actual target material into target coins is applicable for other target combinations as well. Using Mg as a support metal is suitable due to its thermal conductivity, low activation, minimal impact on purification chemistry, softness, ductility, and rapid dissolution in acid.

Beam dynamics design and error analysis of a high frequency RFQ for medical application

Proton therapy based on the linear accelerator is an advanced radiation treatment technology. Lanzhou University has proposed a linac scheme for proton therapy, which features a 750 MHz Radio Frequency Quadrupole (RFQ) as its first accelerator. The RFQ is capable of accelerating a 1 mA proton beam from 30 keV to 3 MeV. The article systematically introduces the beam dynamics design and error analysis of the RFQ. In the design part, a new strategy that can reduce the outlet longitudinal emittance of the RFQ by adjusting its modulation and synchronous phase was proposed. Subsequently, multi-particle simulations based on different codes consistently demonstrated that the dynamics design achieved a good output beam quality. The longitudinal emittance of the RFQ output beam was successfully controlled to below 0.1 π mm·mrad. In the error analysis part, firstly, all types of errors were analyzed separately to determine their impact patterns and to give preliminary tolerances. Then, the combined errors which considered all types of errors together were analyzed. Finally, the tolerances for input beam errors, cavity voltage errors, and mechanical errors were obtained.

Design of a mixed material moderator in a beam-shaping assembly for proton accelerator-based boron neutron capture therapy

Boron Neutron Capture Therapy is being promoted with the development of accelerator neutron sources, and many new accelerator-based BNCT facilities are being built. In Particle Accelerator Facility project of Sun Yat-sen University, we plan to build a terminal for BNCT research based on an 8 MeV, CW 3 mA proton accelerator. In this paper, we present a beam-shaping assembly for this proton accelerator with such low 24 kW beam power, using composite moderator materials composed of five elements: Mg, Al, F, O, and Li. The calculation result of FLUKA with ENDF/B and JENDL libraries shows that the epithermal neutron beam flux is 1.57×109n/cm2/s with the CW 3 mA proton beam. The fast neutron component and the gamma ray component under free-air condition are 1.49×10−13Gy∙cm2 and 8.12×10−14Gy∙cm2 respectively, in line with IAEA-TECDOC-1223 design recommendations. The thermal analysis shows that the maximum temperature of beryllium target is 706.5 K, and the structure materials of BSA do not melt.

Properties analysis on interlayer within lithium target and its beam uniformity for accelerator-based Boron Neutron Capture Therapy

In order to enhance the performance and lifetime of the lithium target used in accelerator-based neutron sources for Boron Neutron Capture Therapy (BNCT) treatment, an exploration of target design was conducted based on the 2.8 MeV, 20 mA proton beam. A comparison between scanning magnets and octupole magnets was performed for beam uniform, with octupole magnets selected to effectively avoid localized high thermal densities over short durations. Exploration was conducted on the performance of tantalum and vanadium as interlayers within the lithium target, considering aspects such as cooling, hydrogen diffusion, and neutron performances. This study revealed that, as the majority of energy deposition occurs within the interlayer, the presence of an appropriately thick tantalum or vanadium interlayer has minimal impact on cooling effectiveness, ensuring temperatures remain below 144 °C. The addition of an interlayer effectively reduces the maximum hydrogen concentration in copper, thus preventing copper blistering. Within the investigated thickness range, the interlayer does not affect neutron spectrum in the forward direction of the target, mitigating concerns regarding its impact on beam shaping.

The extraction of both positive and negative ions from a volume cusp H− ion source

The TRIUMF licensed H− ion source is known to produce 15 mA of H− ions, but some applications, such as cyclotrons, require the injection of both positive and negative ions. Furthermore, when using a tandem accelerator, there would be a benefit in using an ion source that can directly extract H− and He+. A charge exchange chamber would only have to be used with the He+ beam for the production of He−. In this paper, we present the conversion of the H− ion source to allow for the extraction of both positive (He+, H+, H2+ and H3+ ) and negative (H− and D−) ions. In the modified design, up to 3 mA of protons and 2 mA of He+ can be extracted when using positive extraction power supplies and up to 5 mA of H− can be extracted when the polarity of the power supplies switched to negative extraction. We study how the ion source parameters affect the proton fraction and we look at the influence of the magnetic filter field in the plasma chamber.

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.

Double-layered beam shaping assembly design based on intelligent optimization method coupling neural network and genetic algorithm for BNCT

The beam shaping assembly (BSA) plays a crucial role in the facility of accelerator-based boron neutron capture therapy (AB-BNCT). The quality of the neutron beam utilized for treatment is directly influenced by the design of the BSA. However, conventional step-by-step optimization approaches often encounter challenges in achieving the global optimal solution, as they tend to converge towards local optima. To address this issue, this study proposed an intelligent optimization method that combines neural network and genetic algorithm. The proposed method was applied to optimize a double-layered BSA based on the neutron source resulting from a lithium target bombarding by a 2.8 MeV, 20 mA proton beam. The obtained optimal BSA solution parameters well met the IAEA-TECDOC-1223 report, while also exhibiting significantly higher epithermal neutron flux compared to alternative BSA designs. The performance of the epithermal neutron beam was assessed by calculating the dose distribution and clinical parameters in the Snyder head phantom. The findings suggest that this beam exhibits promising therapeutic potential for treating tumors.

Development of a high current electron beam facility for compact accelerator neutron source target thermal tests

Target thermal capabilities are one of the major key points for CANS (Compact Accelerator-based Neutron Source) developments. Indeed, high energy (few MeV) and high average current (few tens of mA) proton or deuteron beams are required to produce high thermal neutron flux of 101³ n.cm⁻2.s⁻1 or greater. The targets must therefore absorb and dissipate a high thermal power. In order to make progress on their designs without deuteron or proton beams, we developed a compact electron beamline based on an Electron Cyclotron Resonance (ECR) source that permits testing of targets under relevant thermal conditions at power densities up 3 kW. cm⁻2.

Beam physics design of a superconducting linac

The China initiative Accelerator-Driven subcritical System (CiADS) project aims to design and build the world’s first accelerator-driven subcritical system demonstration facility. The facility will attain 2.5 MW thermal power in 2026 to realize accelerator-target-reactor coupling experiments. As the first approved accelerator-driven subcritical system facility, the CiADS driver linac will adopt cutting-edge accelerator technologies to achieve the challenging goals of high beam power and high reliability. The accelerator will operate in cw mode to produce a 500 MeV, 5 mA proton beam. To meet the extremely high demands on beam availability, the linac design lays strong emphasis on beam loss control and increased fault tolerance via a novel fault-compensation method. The accelerator complex consists of a room temperature front-end section, a main linac that employs superconducting accelerator technologies, and a high-energy beam transport line. The beam-loss-oriented beam dynamics design of the driver linac complex is presented in the paper. Published by the American Physical Society 2024

Beam Dynamics Studies for the Target Beamlines of the High Brilliance Neutron Source

The High Brilliance Neutron Source (HBS) belongs to the class of High Current Accelerator based Neutron Sources (Hi-CANS). The driver Linac for the HBS must be able to reliably accelerate a 100 mA proton beam to an energy of 70 MeV [2, 1, 3]. The beam is sent pulse-by-pulse to three different targets via a multiplexer in the High Energy Beam Transfer (HEBT) section. Each individual proton pulse behind the multiplexer has a specific time structure in order to optimally serve the different instruments grouped around one target station. The main development steps of the HEBT are the development of a three-field septum magnet, which is an essential part of the multiplexer magnet system, the beam dynamics integration of the multiplexer magnet system into the beamline, and the ion-optical layout of the individual target beamlines.

Analyzing beam-gas interactions in an cyclotron beam

For the Isotope Decay At Rest (IsoDAR) experiment in neutrino physics (searching for sterile neutrinos), we have developed a novel compact isochronous cyclotron with direct injection through an axially embedded RFQ. For IsoDAR to be decisive within five years of running, 10 mA of protons, cw at 80% duty factor are needed on a neutrino production target. To alleviate space charge in the cyclotron driver, we accelerate 5 mA of , to be broken up into 10 mA of protons after extraction from the cyclotron. An open question that we are answering with this paper is whether the beam losses from gas-stripping (the removal of electrons from through the interaction of the beam ions with the residual gas in the accelerator) are going to be a significant challenge. Using a newly added feature to the well-established Object-Oriented Parallel Accelerator Library code, we calculate gas-stripping losses in the IsoDAR cyclotron using realistic beam distributions, magnetic fields, gas composition, and pressure. We show that to maintain losses due to dissociation below 1% over the entire acceleration region, a vacuum of at least 6 × 10−7 mbar is required.

Study and design of the coupled cavity with ladder RFQ and IH DTL structure for transportable neutron source

A transportable accelerator-driven neutron source is under development in Xi'an Jiaotong University (X-TANS), aiming at realizing various outdoor applications, such as on-site degradation diagnosis of concrete infrastructures and analysis of raw materials. To downsize the accelerator cavity for X-TANS, we coupled the Ladder RFQ and an Interdigital H-type Drift tube linac (IH-DTL) into a single cavity to combine the strength of the RFQ's efficient bunching efficiency and DTL's high accelerating gradient and to distantly reduce the weight and size of the linac. To achieve electromagnetic resonance between two structures and a high coupling factor, a novel coupled structure was adopted by adjusting the last supporting plate at the exit of RFQ. The mode separation between 0-mode and π-mode was expanded to 7.96 MHz. Consequently, the 15 mA proton beam can be accelerated to 2.5 MeV with a length of 1.73 m and the effective transmission of above 90%. The dissipated cavity power was 96.87 kW with an operation frequency of 200 MHz and a duty factor of 3%. The design concept of the coupled structure and the results of the beam dynamics design, electromagnetic simulation and multi-physics will be comprehensively presented in this paper.

Analytical study of low energy proton interactions in the SORGENTINA’s fusion ion source-part I: beam-dump

An analytical study, corroborated by Monte Carlo simulations, is presented which describes the interaction of a 300 keV–830 mA proton beam with a Cu and Al dumping system. The analytical calculations rely on the theoretical framework of the Particle Induced X-ray Emission, while the Monte Carlo simulations are performed by means of the GEANT4 toolkit. The case study is related to the project SORGENTINA-RF fusion neutron source and in particular to the tests devoted to assess the performance of the ion source of the plant. The results provide a detailed physical insight of the main processes occurring in the beam dump material, and are also important to give some realistic figures of the radiation emission expected during operation.

Physical design of a compact injector for synchrotron-based proton therapy

A compact room-temperature linear injector has been purposed to accelerate an 18.0 mA proton beam to 7.0 MeV for synchrotron-based proton therapy. The total length is appropriately 5 m. It mainly consists of a 3.01 m radio frequency quadrupole (RFQ) and a 0.82 m compact interdigital H-mode drift tube linac (IH-DTL) structure. Based on a fast-bunching strategy, the RFQ, operated at 325 MHz, accelerates protons to 3.0 MeV. The phase advances have been taken into consideration, and parametric resonance has been carefully avoided by adjusting the vane parameters. After the modulation of the transverse and longitudinal phase advances and a compact external quadrupole triplet, the proton beam is injected into the subsequent IH-DTL. Based on modified Kombinierte Null Grad Strukter (KONUS) beam dynamics, it accelerates protons up to 7.0 MeV, which is composed of a re-bunching section and an accelerating section. The accelerating gradient reaches 4.88 MV/m. The overall dynamic simulation results show that the whole accelerating gradient reaches up to 1.62 MV/m with a transmission efficiency above 95%. The transverse and longitudinal normalized RMS emittances at the exit of the DTL are 0.23 π mm·mrad and 2.216 π keV/u·ns, which meet the synchrotron injection requirements. The details of the specific design of this injector are presented in this paper.

Simulations on the thermal and mechanical performance of the rotating target system of accelerator-driven neutron source for Boron Neutron Capture Therapy(BNCT)

The development of an accelerator-based BNCT facility, X-BNCT, at Xi’an Jiaotong University was introduced. The 30 mA protons were accelerated to 2.8 MeV by a linear RFQ accelerator, then the lithium target was bombarded to produce neutrons required for treatment through 7Li(p, n)7Be reaction, and a large amount of energy was deposited on the target. To remove the heat on the target, the design and analysis of the rotating target system was discussed in this paper. The channels with a small size in the target flap were studied and an interlayer was added to avoid the problem of hydrogen embrittlement. The heat transfer simulation was carried out with Gaussian beam or uniform beam in the rotating target system by the CFD method. The maximum temperatures of lithium were lower than the melting point, indicating the advancement of the rotating target structure in cooling. And it was concluded that the uniform scheme should be considered even for the rotating target system. Finally, the stress analysis of each component of the rotating target in the process of rotation was simulated, and the results showed that the design met the material requirements.

Physical design and multi-physics analysis of a 200 MHz continuous wave radio frequency quadrupole accelerator for a proton accelerator facility

Based on the platform of a proton accelerator facility, a 200 MHz high intensity continuous wave (CW) radio frequency quadrupole (RFQ) accelerator has been designed at the Sino-French Institute of Nuclear Engineering and Technology of Sun Yat-Sen University, China. Employing the conventional four-vane structure, the RFQ can accelerate 20 mA proton beam from 20 keV to 2.5 MeV. In the beam dynamics design, the simulated transmission efficiency reaches 99.5% and the vane length is less than 4 m. In the electromagnetic design, for the long-term stable operation, Pi-mode Stabilizer Loops (PISLs) are utilized to achieve more than 10 MHz mode frequency separation and to decrease the effects of dipole modes. The 48 tuners are optimized to provide a range of ± 2 MHz frequency tuning. Additionally, the undercuts are optimized to ensure a good field flatness along the longitudinal direction. Based on the coolant channel design, the multi-physics analysis is performed to investigate the deformation and stress resulting from the dissipation of RF power within the cavity, as well as determine the temperature tuning coefficients of the coolants within the vane and wall. The entire design and analysis of PAFA-RFQ has been completed, and the scheme of the design can also be applied to the design of other RFQ cavities.

Physics design, fabrication, RF measurement and beam commissioning of a dual beam drift tube linac

A novel type dual-beam drift tube linac (DB-DTL) prototype was firstly designed to prove the feasibility of the multi-beam type DTL at the institute of modern physics. The physics design, cavity fabrication, low-power RF measurement, RF conditioning and beam commissioning of the DB-DTL cavity were completed and presented in this paper. Operating at 81.25 MHz, the DB-DTL was designed to accelerate 10 mA proton from 0.56 MeV to 2.5 MeV. The field distribution of the DB-DTL cavity were measured at low RF power level and particle tracing using measured field were done, which both agree well with the physics design. The measured Q 0 value and the shunt impedance are 11606 and 172 MΩ/m, respectively. The RF conditioning and the first beam commissioning of the DB-DTL cavity were completed. The beam experiment platform was built at the Lanzhou university due to the academy research cooperation between the institute of modern physics, Sun Yat-sen university and Lanzhou university. Based on the existing experiment condition, 2.5 MeV proton acceleration and measurement were successfully achieved at 42 kW (0.85*Q 0)) RF power of the DB-DTL cavity, which match the physics design very well.

Beam dynamics and cavity design of an 8 MeV CW IH-DTL for SYSU-PAFA

As a part of the Particle Accelerator Facility at Sun Yat-sen University (SYSU-PAFA), a 200 MHz drift tube linac (DTL), operating under continuous wave (CW) mode, has been designed. PAFA-DTL is expected to accelerate a 10 mA proton beam from 2.5 MeV to 8 MeV. Using the alternative phase focusing (APF) beam dynamics scheme, a compact cell array has been designed and optimized in order to limit the cavity length to 2.4 m with high acceleration efficiency. As a result, PAFA-DTL contains 31 acceleration cells with beam transmission efficiency reaches 100%, and better output beam quality is obtained by optimizing the input beam parameters. Interdigital H-mode (IH) structure is utilized in the PAFA-DTL cavity, which has achieved a high unloaded quality factor of 13987. Additionally, to ensure the stability of PAFA-DTL under CW operation, a low Kilpatrick factor (Kp) of 1.42 is obtained by adjusting the blending radius of the drift tubes (DTs) to reduce the risk of RF breakdown. The gap voltage distribution through RF design is compared with that from the beam dynamics, and the maximum absolute value of deviation is only 0.73%. In this paper, the detailed design and results of PAFA-DTL, including beam dynamics and RF design, are presented.

Beam shaping assembly design of Li(p,n) neutron source with a rotating target for boron neutron capture therapy

With rapid development in recent years, the accelerator-based boron neutron capture therapy (AB-BNCT) has been paid more and more attention. Our team designed a set of AB-BNCT facility based on the Li(p,n) reaction. We suppose to use a radio frequency quadrupole field accelerator with a 2.8 MeV, 20 mA proton beam to bombard a rotating lithium target. The generated neutrons were moderated by a beam shaping assembly (BSA) to get an epithermal neutron beam for tumor treatment. This paper introduced the parameter calculation and analysis of back reflector, rotating gap and moderator in BSA, discussed the influence of the density of magnesium fluoride block as a moderator on the outgoing neutron beam in detail, and evaluated epithermal neutron beam with a water and Snyder phantom. Finally, it is concluded that a 20 cm lead as the back reflector, the rotation gap of 6 cm, and the density of magnesium fluoride blocks of above 2.5 g/cm3 could make the neutron beam meet the treatment needs. And the density of 2.8 g/cm3 as a compromise choice could obtain an epithermal neutron beam with good therapeutic potential with consideration of the processing difficulty and cost.

Development of experimental and computational frameworks to predict subcooled flow boiling in the LANL Isotope Production Facility

Cooling is crucial to maintain the integrity of target systems in isotope production facilities. At Los Alamos National Laboratory (LANL)’s Isotope Production Facility (IPF), multiple encapsulated targets are stacked and irradiated in tandem with a 100 MeV, ∼250 µA proton beam. To facilitate effective heat removal, these stacked targets are separated and cooled via a series of water channels. At these beam currents, this high-energy proton beam heats the target system, likely initiating subcooled flow boiling in the cooling channels. However, in-beam monitoring of the IPF target system is not possible due to the extreme radiation environment, and the necessarily significant shielding. To better understand high-power target performance, we developed ex-situ experimental and computational frameworks to predict the behavior of subcooled flow boiling at IPF. Subcooled flow boiling experiments on Inconel 625 samples under IPF conditions (2 bar pressure, 10 GPM flow rate (i.e., 2249 kg/m2/s), 85 K subcooling) revealed that IPF's average operating power is at the early stage of boiling with a heat transfer coefficient of 48,000 W/m2/s. The proposed modeling framework enables us to predict a complete boiling curve, i.e., single-phase heat transfer, onset of nucleate boiling, two-phase heat transfer, and critical heat flux (CHF), with specification of input boiling parameters up to intermediate heat flux levels. The estimated CHF under IPF conditions is 5.2 MW/m2. Experimental data under reduced conditions (2 bar pressure, 1.5 GPM flow rate (i.e., 337 kg/m2/s), 45 K subcooling) served as validation cases for the computational modeling. This computational model can be further extended to more complicated systems replicating the real IPF configuration, for instance, to study void distribution as a function of the incident proton beam profile and coolant velocity profile of multiple cooling channels. The proposed experimental and computational frameworks provide a means to better understand cooling systems in the isotope production facilities at different accelerators, where in-beam monitoring of the cooling process is not available.