MeV Accelerator Research Articles

Irradiation-Assisted Microstructure Evolution and Mechanical Properties Loss of 310S Welded Joints

In order to reveal the effect of irradiation damage caused by high-level liquid radioactive wastes on the welded joint of the container, the irradiation-induced microstructure evolution and mechanical properties degradation of the 310S stainless steel welded joints were investigated in this study. For this purpose, the 1.3 MeV 60Co and 2 MeV accelerators were used to simulate irradiation experiments on 310S welded joints. The uniaxial tensile tests characterized the specimens' mechanical properties and fracture morphology. The results revealed that elongation was reduced by about 5% of irradiation damage by 60Co, and the fracture morphology shows a large number of secondary cracks. In contrast, the elongation was recovered irradiated by the accelerator, and the fracture morphology showed a large number of dimples. Following the interrupted creep deformation, creep fracture tests were conducted for irradiation specimens. The 60Co irradiation damage significantly decreases the creep resistance, leading to deformation of creep, which is increased to 1.5 times that of those unirradiated specimens. At the same time, the ductility is seriously degraded for the irradiated creep fracture specimens. As a result, the creep fracture strain of 60Co specimens is reduced to 70% of that of unirradiated specimens. Further, ductility reduction was related to the irradiated hardening by 60Co, while Nano-indenter hardness was 5.9 GPa, higher by 44% than the unirradiated specimens. The results are shown in an enrichment of Cr, C and P elements at phase boundaries for 60Co irradiation specimens, while the magnitude of element segregation increased by the accelerator combination irradiation. Finally, the creep cracking analysis results show intergranular cracking was observed on the surfaces of the irradiated specimens, while the M23C6 has a primary relationship with the intergranular cracks. The synergic effect of irradiation promoted damage, and element segregation was the primary cause of the intergranular cracking of the 310S welded joints.

Heat Transfer Simulation and Analysis of Electron Collector Based on Real-time Uniformity Detection Device of Irradiation Accelerator

Beam scanning uniformity is an important parameter of electron irradiation accelerators, which affects the quality of irradiated products. Accurate measurements of beam scanning uniformity are required to evaluate accelerator performance. Currently, a set of devices is being developed to measure beam scanning uniformity under full beam conditions. However, the measurement device faces serious heating problems when the beam power is large. In this paper, the cooling structure of the electron collector is designed for the developed measurement device. The temperature distribution of the electron collector is simulated by ANSYS. The appropriate cooling flow rates are selected to ensure the thermal stability of the device when the total beam powers are 30 kW and 50 kW, respectively. The electron collector with a cooling structure is fabricated according to design parameters, and the experiment is carried out under a 1.5 MeV accelerator. The temperature is monitored by an infrared thermometer. The results show that the measured temperature is below the limit. The designed cooling parameters effectively solve the heating problem.

Activation of medical accelerator components and radioactive waste classification based on low beam energy model Clinac 2300

The medical linear accelerator, used in Nicolaus Copernicus Hospital in Lodz is integrated system used for photonuclear therapy. The accelerator shows presence of radioactive impurities produced by activation process, by the beam interactions take place and result in residual radioactivity that lasts even after operation and dismantling of the accelerator. The radioactive material management, after disposing or replacing components of the medical accelerator, presents some technical challenges, due to the lack of the clear standards for radioactive waste management in Poland. In practice, most radioactive wastes were stored within the institution or by the manufacturer. After 10 years of operating the medical linear accelerator, the majority of the resulting radioactive waste has been dismantled and each eliminated part has been controlled by verifying the contact dose rates for the pilot analysis with the objective to establish a radioactive waste classification procedure for low beam energy below 35 MeV accelerators. Six accelerator structural elements with elevated surface dose rate values were submitted to radiometric analysis for proper analysis of materials as radioactive wastes. Identification of radionuclide impurities in the construction of an accelerator is the only possible method of proper classification of activated materials, due to the safety assessment of the storage facility.

Two Design Options for Compact Linear Accelerators for High Flux Neutron Source

We describe and compare two optimized design options of RF linear accelerators with different resonant frequencies at 162.5 MHz (f0) and 325 MHz (2∙f0). The RFQ + DTL linacs have been designed to provide 13 MeV acceleration to a proton beam for achieving a fast neutron yield of not lower than 1013 n/s via 9Be(p, n)9B reaction in pulsed-mode operation. Our design studies show that none of the two options is better than the other, but that the choice of operating frequency will mainly be determined by the accelerator length and RF cost consideration. This study can serve as a basis for the design of an initial stage of a new high brilliance Compact Accelerator-driven Neutron Source (CANS), aiming to use neutron scattering techniques for studying material properties in fundamental physics, materials science, nuclear energy, as well as for industries and societal challenges.

New 3 MeV and 7 MeV Accelerators for Cargo Screening and NDT

New 3 MeV and 7 MeV Accelerators for Cargo Screening and NDT

Compact X-Band electron linac for radiotherapy and security applications

RadiaBeam has developed a 6 MeV accelerator that is compact and light enough to be placed on a robotic arm or light truck. The main drivers of size and weight in conventional accelerators are the power source and the shielding. Small dimensions are enabled by operation at 9.3 GHz frequency (X-band), which allows reducing the size and weight of all accelerator components. Thanks to the robust design of the accelerating structure, the accelerator can be used as a source for novel cargo inspection and radiotherapy techniques. In this paper, we present the linac design and its components, as well the results of the experimental demonstration of beam acceleration.

Appied Nuclear Physics-Advanced Ion Beam Materials Analysis at small Accelerators

The ossendorf Ion Beam Laboratory has been developed to an international large scale user facility in the field of ion beam physics and ion beam materials research. The laboratory operates a large number of modern experimental equipment at three MeV accelerators, three implanters, an ECR source and a FIB which together pro- vide almost all ions species in a wide energy range from a few hundred eV to a few ten MeV. Also IBAD and PHI devices were installed for various purposes. The re- search stations at the accelerators are supplemented by complementary techniques like TEM, SEM, AUGER, AFM etc., all contributing useful information to thin film investigations. In this paper a short overview of the laboratory is given and a few recent experiments and their results are shown. Rutherford Backscattering Spec- trometry ( RBS) and Elastic Recoil Detection Analysis (ERDA) are well established techniques for quantitative thin film. The advantage of these methods consists in the simple physics they are basing on, namely the stopping of energetic ions in matter and the binary scattering of at the Coulomb potential of atomic nuclei. The increasing importance of ultra-thin layers for novel technologies demands quantita- tive analysis techniques with a depth resolution of atomic monolayers, which can be obtained for RBS and ERDA by magnetic spectrometers only. The magnetic spec- trometers we have installed at the 3 MV Tandetron and at the 5 MV tandem are described , recent applications are shown and a few problems to achieve high depth resolution will be discussed. Heavy ion detectors as Bragg IC, dE-Erest-telescopes and ToF spectrometers, developed for nuclear physics experiments, are now applied for ERDA, providing an efficient analysis of thin films containing light elements. The lateral position resolution of such detectors enables kinematic corrections and allows large solid angles. Thus by ERDA in situ studies during surface modification processes are possible like in the case of the nitridation of aluminum and stainless steel. At the external beam mainly objects of fine arts or of historical value are analysed. It will be shown, how the complementary application of PIXE, RBS and PIGE can help to detect the beginning corrosion of mediaeval glass objects.

Design of compact accelerator system for high flux accelerator based neutron source.

Accelerator Based Neutron Sources (ABNS) have been studied for their utility in materials research as well as for boron neutron captured therapy. By making significant efforts to study the (p,n) and (d,n) nuclear reactions, the specifications of the accelerator system have been determined. In this paper, we compare the design results for two types of radio frequency quadrupole (RFQ) accelerators to provide proton and deuteron beams, respectively. Both systems consist of an electron cyclotron resonance (ECR) ion source, a low-energy beam transport system, an RFQ accelerator, a medium-energy beam transport system, a Be target, and a moderator system. In order to achieve a compact accelerator system at a reasonable cost, different requirements must be applied to the design of RFQ accelerators. The proton RFQ has been designed with an operation frequency of 352 MHz, up to 4 MeV acceleration, 10 mA beam intensity, and a continuous-wave (CW) operation mode to achieve 0.84 × 109 n/(s/cm2) of neutron production. However, the deuteron RFQ has been designed with an operation frequency of 200 MHz, up to 2.5 MeV acceleration, 15 mA of beam intensity, and a CW operation mode to achieve 1.02 × 109 n/(s/cm2) of neutron production. In this paper, we describe the merit of the deuteron based neutron source by comparing two types of the RFQ accelerators for proton and deuteron beams including the common system of the ECR ion source and Be target in detail.

A polystyrene film dosimeter containing dithizone dye for high dose applications of gamma-ray source

A dosimeters made up of polystyrene (PS) binder containing different concentrations of dithizone (Dz) dye are investigated for high dose applications. Dyed PS film dosimeters were irradiated by 60Co gamma-ray source with dose rate of 8.4 kGy/h. The optical properties of unirradiated as well as irradiated films were investigated by UV/VIS spectrophotometer. The dose response in terms of change in absorbance of Dz-PS film was measured at wavelength of 630 nm. The bleaching in color (green) of irradiated films with higher concentration of Dz dye increases linearly with increasing absorbed dose up to 100 kGy.60Co gamma-ray source of 1.25 MeV and electron beam accelerator of 10 MeV were used study the effect of radiation energy on the irradiated dyed PS film. 60Co gamma-ray source of 8.4 kGy/h and electron beam accelerator of 3600 kGy/h were used study the effect of dose rate on the dose response of dyed PS film. The effect of relative humidity on irradiated Dz-PS film dosimeters was investigated in the range 12–75%. The effects of dose rate, radiation energy and relative humidity on the dose response of Dz-PS film were about 2%. The film shows a perfect post-irradiation stability (about ±2%; 1σ) for one month after irradiation.

Economic evaluation of radiopharmaceutical Mo-99 production in reactor and accelerators in Iran

Introduction: Radioisotope 𝑇𝑐-99m is one of the most important in the field for thyroid imaging, intestinal or bladder appendages, blood vessel imaging, detecting blood clots, bone imaging, etc. This necessary radioisotope is the daughter of a nuclear-radioactive molybdenum-99 that is manufacturing in accelerators or research reactors. Our world now needs 12000 Ci. Given the growing trend in nuclear medicine imaging, the economic issue of producing the radioisotopes required for these images is going to be important. In this paper, using the TALYS code and the software SRIM, TRIM and MATLAB, we compared the accelerator gain with the reactor and provided an optimized method for Iran. Materials and Methods: Using the TALYS code, we find the dependence of the cross-sectional energy on energy and then, using the SRIM code, we consider the energy dependence of the protons in depth penetration. Using MATLAB, we obtain the mean value of the cross section using the equations from TALYS, and obtain yield for protons we guess demand Iran’s need. Results: So if we have two 30 Mev (and 300µA) accelerators in the two three-day sets in week with a one-day rest having irradiate, then Iran needs about 70-80 Ci will be satisfy, and the rest of the demand for Tehran will be from in direct way of Tc-99m production. In this case, for each accelerator per week, we need about 2 grams per week and for direct production of Tc, 40 mg of enriched molybdenum 100 per day is needed, which costs are calculated. Conclusion: Even without considering the cost of electricity and waste disposal and separation, and only by comparing the annual uranium cost with the total accelerator cost, we will find that the accelerator method is much more convenient and reasonable. In the accelerator method, regardless of the initial cost of the devices, we annually had the cost of electricity and enriched molybdenum and other costs that are shared with the reactor (employee salaries and separation, etc.). Perhaps these costs are higher in the reactor. In addition, we have a lot of problems with the acquisition of enriched uranium and we buy it at a great price from Argentina or Russia. Or the cost of molybdenum 99 at an annual price of $ 4 million from Russia, which can be produced at a lower cost at home and, in addition to economic optimization, also leads to entrepreneurship.

The discovery of chemically produced mass independent isotope effects: The physical chemistry basis and applications to the early solar system, planetary atmospheres, and the origin of life

The discovery of chemically produced mass independent isotope effects: The physical chemistry basis and applications to the early solar system, planetary atmospheres, and the origin of life

Requirements for the Cryogenic Refrigerator and the He Distribution System for the MYRRHA 100 Mev Accelerator

Requirements for the Cryogenic Refrigerator and the He Distribution System for the MYRRHA 100 Mev Accelerator

Characterization of a 6 MeV Accelerator Driven Mixed Neutron/Photon Source

There are many applications which require high yield radiation sources with mixed fluxes of photons and neutrons. In particular, such sources are necessary to test radiation detectors and materials. This study was concerned with the determination of photon and neutron fluxes generated by the interaction of a 6 MeV linear electron accelerator driven photon beam with a beryllium photoneutron converter. The double step procedure of an (e,γ) reaction followed by an (γ,n) emission results in a mixed radiation environment. The optimal converter geometry was determined by comparison of the computed neutron fluxes for each converter position. Computational results have shown that photon fluxes up to 1011 photons/cm2/s and neutron fluxes up to 107 neutrons/cm2/s are achievable with the optimal setup. This paper is focused on the results of the MCNPX modeling and experiments and discussion of the converter orientation which leads to the largest radiation fluxes.

Electron sheath dynamic in the laser–foil interaction

AbstractIn the interaction of ultra-short and ultra-intense high contrast laser pulse with a dense foil, accelerating electron sheath is formed. The dynamic of this sheath is obtained according to the ponderomotive force of the laser pulse and restoring electrostatic force of the stationary heavy ions. In the transient dynamics, maximum electron sheath displacement is obtained for different interaction parameters. This maximum displacement has an important effect in the explanation of the electron blow out condition. It is shown numerically that the electron sheath maximum displacement increases with increasing laser pulse amplitude or decreasing its rise time, or by decreasing plasma electron density. Recently, backward MeV acceleration of electrons in the interaction of intense laser pulse with solid targets was observed. The ponderomotive force of the compressed reflected laser pulse includes in our formalism and is used for explanation of the electron's backward acceleration. The threshold values of the interaction parameters for the occurrence of this phenomenon are considered. The electron blow out condition and backward acceleration are accompanied with numerical modeling and 1D3V, particle-in-cell simulation code.

Brightness measurement of an electron impact gas ion source for proton beam writing applications.

We are developing a high brightness nano-aperture electron impact gas ion source, which can create ion beams from a miniature ionization chamber with relatively small virtual source sizes, typically around 100 nm. A prototype source of this kind was designed and successively micro-fabricated using integrated circuit technology. Experiments to measure source brightness were performed inside a field emission scanning electron microscope. The total output current was measured to be between 200 and 300 pA. The highest estimated reduced brightness was found to be comparable to the injecting focused electron beam reduced brightness. This translates into an ion reduced brightness that is significantly better than that of conventional radio frequency ion sources, currently used in single-ended MeV accelerators.

Progress in long-pulse production of powerful negative ion beams for JT-60SA and ITER

Significant progress in the extension of pulse durations of powerful negative ion beams has been made to realize the neutral beam injectors for JT-60SA and ITER. In order to overcome common issues of the long-pulse production/acceleration of negative ion beams in JT-60SA and ITER, new technologies have been developed in the JT-60SA ion source and the MeV accelerator in Japan Atomic Energy Agency.As for the long-pulse production of high-current negative ions for the JT-60SA ion source, the pulse durations have been successfully increased from 30 s at 13 A on JT-60U to 100 s at 15 A by modifying the JT-60SA ion source, which satisfies the required pulse duration of 100 s and 70% of the rated beam current for JT-60SA. This progress was based on the R&D efforts for the temperature control of the plasma grid and uniform negative ion productions with the modified tent-shaped filter field configuration. Moreover, each parameter of the required beam energy, current and pulse has been achieved individually by these R&D efforts. The developed techniques are useful to design the ITER ion source because the sustainment of the caesium coverage in the large extraction area is one of the common issues between JT-60SA and ITER.As for the long-pulse acceleration of high power density beams in the MeV accelerator for ITER, the pulse duration of MeV-class negative ion beams has been extended by more than 2 orders of magnitude by modifying the extraction grid with a high cooling capability and a high transmission of negative ions. A long-pulse acceleration of 60 s has been achieved at 70 MW m−2 (683 keV, 100 A m−2) which has reached the power density of JT-60SA level of 65 MW m−2. No degradations of the voltage holding capability of the acceleration voltage and the beam optics due to the distortion of the acceleration grids have been observed in this power density level.These results are the longest pulse durations of high-current and high-power-density negative ion beams in the world.

Trends and applications for MeV electrostatic ion beam accelerators

The 1970s into the 1980s saw a major broadening of applications for electrostatic accelerators. Prior to this time, all accelerators were used primarily for nuclear structure research. In the 70s there was a significant move into production ion implantation with the necessary MeV ion beam analysis techniques such as RBS and ERD. Accelerators are still being built for these materials analysis techniques today. However, there is still a great ongoing expansion of applications for these machines. At the present time, the demand for electrostatic accelerators is near an all time high. The number of applications continues to grow. This paper will touch on some of the current applications which are as diverse as nuclear fission reactor developments and pharmacokinetics. In the field of nuclear engineering, MeV ion beams from electrostatic accelerators are being used in material damage studies and for iodine and actinide accelerator mass spectrometry (AMS). In the field of pharmacokinetics, electrostatic MeV accelerators are being used to detect extremely small amounts of above background 14C. This has significantly reduced the time required to reach first in human studies. These and other applications will be discussed.

Long-pulse beam acceleration of MeV-class H− ion beams for ITER NB accelerator

In order to realize neutral beam systems in International Thermonuclear Experimental Reactor whose target is to produce a 1 MeV, 200 A/m(2) during 3600 s D(-) ion beam, the electrostatic five-stages negative ion accelerator so-called "MeV accelerator" has been developed at Japan Atomic Energy Agency. To extend pulse length, heat load of the acceleration grids was reduced by controlling the ion beam trajectory. Namely, the beam deflection due to the residual magnetic field of filter magnet was suppressed with the newly developed extractor with a 0.5 mm off-set aperture displacement. The new extractor improved the deflection angle from 6 mrad to 1 mrad, resulting in the reduction of direct interception of negative ions from 23% to 15% of the total acceleration power, respectively. As a result, the pulse length of 130 A/m(2), 881 keV H(-) ion beam has been successfully extended from a previous value of 0.4 s to 8.7 s. This is the first long pulse negative ion beam acceleration over 100 MW/m(2).

Prototyping Control and Data Acquisition for the ITER Neutral Beam Test Facility

The ITER Neutral Beam Test Facility will be the project's R&D facility for heating neutral beam injectors (HNB) for fusion research operating with H/D negative ions. Its mission is to develop technology to build the HNB prototype injector meeting the stringent HNB requirements (16.5 MW injection power, -1 MeV acceleration energy, 40 A ion current and one hour continuous operation). Two test-beds will be built in sequence in the facility: first SPIDER, the ion source test-bed, to optimize the negative ion source performance, second MITICA, the actual prototype injector, to optimize ion beam acceleration and neutralization. The SPIDER control and data acquisition system is under design. To validate the main architectural choices, a system prototype has been assembled and performance tests have been executed to assess the prototype's capability to meet the control and data acquisition system requirements. The prototype is based on open-source software frameworks running under Linux. EPICS is the slow control engine, MDSplus is the data handler and MARTe is the fast control manager. The prototype addresses low and high-frequency data acquisition, 10 kS/s and 10 MS/s respectively, camera image acquisition, data archiving, data streaming, data retrieval and visualization, real time fast control with 100 μs control cycle and supervisory control.

Vacuum Insulation and Achievement of 980 keV, 185 A/m2 H− Ion Beam Acceleration at JAEA for the ITER Neutral Beam Injector

Vacuum insulation of −1 MV is a common issue for the HV bushing and the accelerator for the ITER neutral beam injector (NBI). The HV bushing as an insulating feedthrough has a five-stage structure and each stage consists of double-layered insulators. To sustain −1 MV in vacuum, reduction of electric field at several triple points existing around the double-layered insulators is a critical issue. To reduce electric field simultaneously at these points, three types of stress ring have been developed. In a voltage holding test of a full-scale mockup equipped with these stress rings, 120% of rated voltage was sustained and the voltage holding capability required in ITER was verified. In the MeV accelerator, whose target is the acceleration of a H− ion beam of 1 MeV, 200 A/m2, the gap between the grid support was extended to suppress breakdowns triggered by electric field concentration at the edge and corner of the grid support. This modification improved the voltage holding capability in vacuum, and the MeV accelerator succeeded in sustaining −1 MV stably. Furthermore, it appeared that the H− ions beam was deflected and a part of the beam was intercepted at the acceleration grid. This causes high heat load on the grids and breakdowns during beam acceleration. To suppress the direct interception, a new grid was designed with proper aperture displacement based on a three dimensional beam trajectory analysis. As a result, 980 keV, 185 A/m2 H− ion beam acceleration has been demonstrated, which is close to the ITER requirement.