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We report the high-gradient tests results of a novel traveling wave accelerating structure for $\beta =0.3$ based on a novel approach of operating at the first negative spatial harmonic. Accelerating gradients of 50 MV/m and peak electric fields of 160 MV/m were achieved in a single structure consisting of 15 coupled cells during tests at the advanced photon source. This work was performed by RadiaBeam, in collaboration with the Argonne National Laboratory, as a part of a Research and Development Program for the development of an ultrahigh-gradient linear accelerator, the Advanced Compact Carbon Ion Linac, for hadron therapy.

In this article, we propose the conceptual design, with supporting beam dynamics results, of a normal conducting, separated-sector cyclotron with a strong-focusing field gradient designed to accelerate light ions with a charge-to-mass ratio of 1/2 up to 15–20 MeV/u. The design can support a host of applications for therapy, radiobiology, material science, and instrumentation development. The light-ion species, which can include a mixed ion beam, can be dynamically chosen to provide a range of characteristic signals appropriate for specific material identification such as special nuclear materials. A conservative baseline concept is presented which has been optimized for radioisotope production of alpha emitters and theranostic radiopharmaceuticals. The modular design is also demonstrated to be scalable in gross physical parameters by a factor of 2–3, thereby reducing the size, weight, and power requirements (SWaP) and enabling near-term security applications.

The development of ultracompact particle accelerators and accelerator-based high-power THz generators are some of the top priorities for research and development programs around the world. These tools require the development of accelerating structures, operating in the mm-Wave and THz range, where diagnostics are not available or are insufficient. This article presents the design of a pulse-to-pulse THz spectrometer, primarily developed for diagnostics of accelerating structures and THz radiation sources. In particular, this spectrometer can be used to detect RF pulse shortening caused by vacuum breakdown and beam misalignment in THz accelerators, as well as for bunch length monitoring and radiation source diagnostics. The spectrometer is based on a diffraction grating and is capable of covering a frequency range where RF-based breakdown measurements are not possible. We have built and tested the first prototype with different sources in a frequency range of 0.1–1.0 THz. In this article, we present the physical design, supported numerical simulations, electronics development, and test results.

The capability to produce high current, low loss, and extracted external ion beams presents an enabling technology for nuclear security, isotope production, and medical applications. We report on a novel, continuous-wave cyclotron for accelerating light ions with a charge-to-mass ratio of 1/2, which is designed for 1 mA maximum and 15 MeV/u energy. This article details the conceptual electromagnetic (EM) and engineering design including the 1.1 T sector magnets and 45 MHz, 200 kV radio frequency (RF) cavities. We discuss the cyclotron beam parameters with respect to potential commercial and industrial applications. The general concept and the accelerator’s layout are followed by a detailed EM design of magnets and RF cavities. Finally, practical engineering design considerations will be provided.

The Facility for Rare Isotope Beams (FRIB) will be a new scientific user facility that produces rare-isotope beams for experiments from the fragmentation of heavy ions at energies of 100–200 MeV/u. During the projectile fragmentation, the rare isotope of interest is produced along with many contaminants that need to be removed before the beam reaches detectors. At FRIB, this is accomplished with a magnetic projectile fragment separator. However, to achieve higher beam purity, in particular for proton-rich rare isotopes, additional purification is necessary. RadiaBeam in collaboration with Michigan State University (MSU) has designed a 20.125 MHz radiofrequency (RF) fragment separator capable of producing a 4 MV kick with 18 cm aperture in order to remove contaminant isotopes based on their time of flight. In this paper, we will discuss the RF and engineering design considerations of this separator cavity.

Present superconducting accelerators require a central refrigeration system and piping to distribute liquid helium and nitrogen. Stand-alone cryocooler-based systems are of significant interest both to scientific and industrial customers, as they allow applications at facilities where no cryogenic equipment and expertise exists, where it is undesirable to develop additional cryogenic systems, or where a mobile system that can be transported between beamlines or facilities is required. The technical challenge of this approach is to minimize the heat losses to the liquid helium so that commercially available, self-contained cryocoolers are able to handle the thermal load. This article presents an improved design for a stand-alone quarter-wave resonator (QWR) cryomodule based on commercially available cryocoolers. This cryomodule has a particular application in the Argonne Tandem Linac Accelerator System intensity upgrade project, where it will house a 72.75 MHz QWR for beam energy adjustments to experimental areas, where no helium cryogenic systems exist. The described cryomodule may also be the critical part of a turnkey system with application to material processing, semiconductor manufacturing, food irradiation, and homeland security. The development of low-heat loss peripheral components reduces the cost and widens applicability of the system. We will discuss the cryomodule and RF coupler designs, including numerical thermal and structural analyses.

Ionization scattering of electron beams with residual gas molecules causes ion trapping in electron rings, both in a collider and electron cooling system. These trapped ions may cause emittance growth, tune shift, halo formation, and coherent coupled bunch instabilities. In order to clear the ions and prevent them from accumulating turn after turn, the gaps in a temporal structure of the beam are typically used. Typically, the gap in the bunch train has a length of a few percent of the ring circumference. In those regions, the extraction electrodes with high pulsed voltages are introduced. In this paper, we present the design consideration and initial test results of the high-voltage pulsed kicker hardware that includes vacuum device and pulsed voltage driver, capable of achieving over 3 kV of deflecting voltage amplitude, rise and fall times of less than 10 ns, 100 ns flat-top duration at 1.4 MHz repetition rate.

The development of novel high-gradient accelerating structures operating at THz frequencies is critical for future free-electron lasers and TeV scale linear colliders. To reach high energies with reasonable length requires high accelerating gradients of ~100 MV/m. The main limitation to reaching these high-energy gradients is the vacuum RF breakdown phenomenon, which disrupts normal accelerator operations. For stable operations and to understand the breakdown microscopic dynamics, a new device capable of detecting the breakdown occurrences is required. In this paper, we provide the design of a pulse length monitor based on an analog to digital converter for fast signal digitization without the need to use high-speed digitizers to be used in a commercial mm-wave heterodyne spectrometer.

The three most popular radiation oncology technologies are based on using beams of photons, electrons, and hadrons (protons and heavy ions). Photon radiotherapy is currently a quite mature and advanced technology. However, it continues to evolve toward improvement of its medical effectiveness and set new requirements for the radiation source, which is typically an electron linear accelerator (linac). For example, novel techniques that involve tumor irradiation from 4π angle or FLASH ultrafast delivery of large doses cannot be efficiently realized with the existing accelerators. At the same time, hadron radiotherapy promises improved treatment outcomes in certain cases. Efforts are underway to develop more compact hadron linac technologies with the ability to change the beam energy in millisecond time scales for efficient spot scanning. In this paper we will overview the current trends in linac technologies for electron, photon and hadron therapy, and provide examples of such developments at RadiaBeam.

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.

Conventional thermionic microwave and radio frequency (RF) guns can offer high average beam current, which is important for synchrotron light and terahertz (THz) radiation source facilities, as well as for industrial applications. For example, the Advanced Photon Source at Argonne National Laboratory is a national synchrotron-radiation light source research facility that utilizes thermionic RF guns. However, these existing thermionic guns are bulky, difficult to handle and install, easily detuned, very sensitive to thermal expansion, and due for a major upgrade and replacement. In this paper, we present the design of a new, more stable, and reliable gun with optimized electromagnetic performance, improved thermal engineering, and a more robust cathode mounting technique, which is a critical step to improve the performance of existing and future light sources, industrial accelerators, and electron beam-driven THz sources. We will also present a fabricated gun prototype and show results of high-power and beam tests.

Quantum computers (QC), if realized, could disrupt many computationally intense fields of science. The building block element of a QC is a quantum bit (qubit). Qubits enable the use of quantum superposition and multi-state entanglement in QC calculations, allowing a QC to simultaneously perform millions of computations at once. However, quantum states stored in a qubit degrade with decreased quality factors and interactions with the environment. One technical solution to improve qubit lifetimes and network interactions is a circuit comprised of a Josephson junction-based qubit located inside of a high Q-factor superconducting 3D cavity.It is known that niobium resonators can reach $Q_{0}>10^{11}$Q0>1011. However, existing cavity geometries are optimized for particle acceleration rather than hosting qubits. RadiaBeam Technologies, in collaboration with Argonne National Laboratory and The University of Chicago, has developed a niobium superconducting radio frequency quarter-wave resonant cavity (QWR) for quantum computation. A 6 GHz QWR was optimized to include tapering of the inner and outer conductors, a toroidal shape for the resonator shorting plane, and an inner conductor tip to reduce parasitic capacitance. In this paper, we present the results of the resonator design optimization, fabrication, processing, and testing.

Although linear accelerators are used in many security, industrial and medical applications, the existing technologies are too large and expensive for several critical applications such as radioactive source replacement, field radiography and mobile cargo scanners. One of the main requirements for these sources is to be highly portable to allow field operation. In response to this problem, RadiaBeam has designed a hand-portable 1 MeV X-ray source, scalable to higher energies, based on Ku-band split electron linac, that can be used for Ir-192 radioisotope replacement. In this paper, we present its multiphysics and engineering design studies, as well as an accelerating structure prototype along with RF measurements.

Beam dynamics simulations in traveling wave (TW) accelerating structures with significant beam loading is a challenging problem. Some codes are capable of calculating the TW electromagnetic fields , and some can track particles through such fields, but most cannot treat both self-consistently. A few commercial codes can model the physics correctly at the expense of many processor-hour computations to obtain converged self-consistent solutions. However, simple, accurate equations of motion for intensive beam dynamics in TW accelerating structure analysis have been previously obtained by Masunov and subsequently implemented in the Hellweg code, which was developed at the Moscow Engineering-Physics Institute. Hellweg is based on equations that allow fast simulations of beam dynamics while taking into account such effects as beam loading, space charge, and external magnetic fields . In this paper, we describe in detail some recent improvements to the Hellweg physics kernel. We have generalized the Masunov results into a 3D set of equations of motion, which include all spatial components of the radiofrequency (RF) and external magnetic fields. We have also improved the Lapostolle space charge model to the general 3D ellipsoid form for any dimensions’ ratio, consideration for the particles outside the beam core, and the fields from the neighboring bunches that can exist in the real machine. These modifications allow approaching the Hellweg accuracy to the self-consistent commercial codes while keeping the simulation time short, which is essential during the linac design and optimization stage. The implementation of these new capabilities in Hellweg is carefully benchmarked against other codes and analytical calculations. The code is freely available with an open source license.

The Argonne Tandem Linac Accelerator System (ATLAS) is planning an upgrade to a multi-user facility to simultaneously accelerate both stable beams from an ECR ion source and radioactive beams from an Electron Beam Ion Source charge breeder. The ATLAS Multi-User Upgrade will need to provide high transmission of ion beams with a mass-to-charge ratio up to 7 as it enables more options to alternate radioactive and stable beams. Currently, the bunching is provided with a lumped circuit multi-harmonic buncher, which cannot effectively operate at the required amplitude of the saw-tooth voltage for ions with mass-to-charge ratio of 7 due to thermal issues. RadiaBeam Systems in collaboration with Argonne National Laboratory has designed a four-harmonic coaxial resonator buncher with the ATLAS fundamental frequency of 12.125 MHz, and a compact, less than 2-m-long, footprint, capable of providing the required voltage of 6.2 kV. This device allows fast and reliable pre-bunching of DC ion beams with the capability of fast switching of heavy-ion radioactive and stable beams for delivery to multiple users. In this paper, we will discuss the RF and engineering design considerations of this buncher.

Measurements of longitudinal beam profile in non-relativistic hadron accelerators are usually performed with Bunch Shape Monitors that utilize secondary electron emission to reproduce the shape of a primary ion beam . The existing devices, however, have poor electron collection efficiency from the wire and are limited to one dimensional measurements of the phase coordinate. In this paper we present the performance improvements for a bunch shape monitor for proton beams used in the Spallation Neutron Source accelerator. These improvements were achieved by adding focusing optics between the wire and the entrance slit, which will also allow measurements over a much higher dynamic range. Here we present the design, simulation and experimental test results of the developed new electron beam guidance system for the existing SNS bunch shape monitor that allowed significant improvement in the collection efficiency.

A novel, low-dose Mobile Intelligent X-ray Inspection (MIXI) concept is being developed at RadiaBeam Technologies. The MIXI concept relies on a linac-based, adaptive, ramped energy source of short X-ray packets of pulses, a new type of fast X-ray detector, rapid processing of detector signals for intelligent control of the linac, and advanced radiography image processing. The key parameters for this system include: better than 3 mm line pair resolution; penetration greater than 320 mm of steel equivalent; scan speed with 100% image sampling rate of up to 15 km/h; and material discrimination over a range of thicknesses up to 200 mm of steel equivalent. Its minimal radiation dose, size and weight allow MIXI to be placed on a lightweight truck chassis.

This paper provides a brief overview of new screening methods that employ Modulated-Energy X-ray Pulses (MEXP) to provide a number of near-simultaneous multi-energy measurements in transmission-, backscatter-, and Computed Tomography (CT) security systems. In transmission X-ray cargo screening, these multi-energy measurements improve material discrimination, maximize penetration, and enhance contrast resolution while simultaneously reducing inspection time and dose to the environment, thus resulting in a smaller exclusion zone. In backscatter systems, the use of this method will increase penetration and improve image quality of concealed objects located deeper below the surface. Specifically, different depths within an object can be probed simultaneously. In CT, our MEXP approach mitigates the main disadvantages of the conventional dual-energy technique: a) distortion of image of the boundaries between regions with large difference in density; b) limited range of object thickness where material decomposition is valid; c) ambiguity and artifacts caused by sampling different regions due to motion of the object between interlaced pulses with distinct energies. Results of testing of the prototype of high speed Adaptive, Multi-Energy Cargo Inspection System (AMEXIS) will be presented. Progress in the development of MEXP-based backscatter inspection system, and systems for cargo screening with Adaptive CT will also be shown.

X-ray multi-energy adaptive security radiography and computed tomography inspection techniques have superior performance compared to conventional dual-energy methods where two image slices are acquired by alternating energies. This new technique allows improving the quality of radiographic and CT images, expanding the range of areal densities of the interrogated objects over which effective discrimination of materials by atomic number is possible, eliminating artifacts in the image of boundaries of different densities, and reducing the time of inspection and the required dose. For this new inspection technology, RadiaBeam Technologies is developing several new types of x-ray sources that are based on linear electron accelerators. To provide an adaptive mode of operation of inspection systems, such accelerators use fast feedback from the detector array. Depending on the application, the range of the electron energy can vary from 180 keV up to 9 MeV. In this paper, we discuss the requirements for such linear accelerators, some details about their designs, and present the results of high-power and beam testing of the S- and X- band accelerators.

This paper presents the design for a switching magnet capable of deflecting 6.5 MeV/u heavy-ion beams with mass-to-charge ratio of 7 by 10 degrees. This magnet can produce variable flat-top pulses from 1 to 30 ms with rise and fall times of less than 0.5 ms at a variable duty cycle of 3–91% into a heavily inductive load. The magnet has a laminated, iron dominated, H-shaped core. Directly-cooled copper pancake coils energize the magnet. We present the magnet design considerations, including the results of extensive computer modeling. We also present the conceptual engineering design and the studies of magnet yoke fabrication.

RadiaBeam has developed a novel, flexible linac for electrons and X-rays (FLEX) capable of energy variation from 2 to 9 MeV within a single RF pulse. This accelerator employs a robust traveling wave accelerating structure with a large energy and power acceptance that allows the unique features of deep energy and current variation required for novel adaptive cargo inspection techniques and Computed Tomography. Robust RF and water-cooling systems allow average beam powers up to 15 kW, upgradable to 57 kW, at 6 MeV, potentially making this accelerator useful for electron beam irradiation applications. The high peak currents of the electron beam produced by FLEX enable novel FLASH radiotherapy methods with fast dose delivery. In this paper, we present the linac design and its components, as well the results of the experimental demonstration of beam acceleration with energy variation.

Reciprocity is a fundamental physical principle that roots in the time‐reversal symmetry of physical laws. It allows making predictions on any arbitrary complex system's response and operation and hence simplifies the analysis. However, there are many practical situations in which it is advantageous to break reciprocity, e.g., isolators preventing wave scattering back to lasers and generators, full‐duplex systems for multiplexing transmission and receiving in the same channel, nonreciprocal cavity excitation, and protection of fragile states of superconductor quantum computers from thermal noise. The most widespread approach to time‐reversal symmetry breaking and nonreciprocity based on magnetic field biasing suffers from bulkiness, cost ineffectiveness, and loss, motivating researchers and engineers to search for more practical approaches. Herein, the up‐and‐coming advances in optical nonreciprocity, including new materials (Weyl semimetals, topological insulators, metasurfaces), active structures, time‐modulation, parity‐time (PT)‐symmetry breaking, nonlinearity combined with a structural asymmetry, quantum nonlinearity, unidirectional gain and loss, chiral quantum states and valley polarization are overviewed. A general description of nonreciprocal systems is provided and the pros and cons of the mentioned approaches to nonreciprocity are discussed.

A tubular disk-and-ring, tapered accelerating structure for small electron linacs and MicroLinacs is considered. It consists of metal and dielectric elements inserted into a metallic tube to eliminate multi-cell, multi-step brazing. The structure enables a wide range of phase velocities (including non-relativistic), a wide bandwidth allowing large number of cells (for standing wave mode) or short filling time (for traveling wave mode), combination of compensated and purely π-mode cells, alternative periodic focusing built-in to the RF structure (the disks), and combining of RF and vacuum windows. RF and accelerating performance of such a long structure having up to four dozens cells is analyzed. Some of beam dynamics, thermal, and vacuum aspects of the structure and MicroLinac performance are considered as well.

The development of high-gradient accelerating structures for low-$\ensuremath{\beta}$ particles is the key for compact hadron linear accelerators. A particular example of such a machine is a hadron therapy linac, which is a promising alternative to cyclic machines, traditionally used for cancer treatment. Currently, the practical utilization of linear accelerators in radiation therapy is limited by the requirement to be under 50 m in length. A usable device for cancer therapy should produce 200--250 MeV protons and/or $400--450\text{ }\text{ }\mathrm{MeV}/\mathrm{u}$ carbon ions, which sets the requirement of having $35\text{ }\text{ }\mathrm{MV}/\mathrm{m}$ average ``real-estate gradient'' or gradient per unit of actual accelerator length, including different accelerating sections, focusing elements and beam transport lines, and at least $50\text{ }\text{ }\mathrm{MV}/\mathrm{m}$ accelerating gradients in the high-energy section of the linac. Such high accelerating gradients for ion linacs have recently become feasible for operations at S-band frequencies. However, the reasonable application of traditional S-band structures is practically limited to $\ensuremath{\beta}=\mathrm{v}/\mathrm{c}g0.4$. However, the simulations show that for lower phase velocities, these structures have either high surface fields ($g200\text{ }\text{ }\mathrm{MV}/\mathrm{m}$) or low shunt impedances ($l35\text{ }\text{ }\mathrm{M}\mathrm{\ensuremath{\Omega}}/\mathrm{m}$). At the same time, a significant ($\ensuremath{\sim}10%$) reduction in the linac length can be achieved by using the $50\text{ }\text{ }\mathrm{MV}/\mathrm{m}$ structures starting from $\ensuremath{\beta}\ensuremath{\sim}0.3$. To address this issue, we have designed a novel radio frequency structure where the beam is synchronous with the higher spatial harmonic of the electromagnetic field. In this paper, we discuss the principles of this approach, the related beam dynamics and especially the electromagnetic and thermomechanical designs of this novel structure. Besides the application to ion therapy, the technology described in this paper can be applied to future high gradient normal conducting ion linacs and high energy physics machines, such as a compact hadron collider. This approach preserves linac compactness in settings with limited space availability.

X-ray Computed Tomography (CT) is a widely used tool for security and industrial non-destructive testing (NDT). Scanned objects in these uses typically contain multiple materials with different atomic numbers. In these cases, Dual-Energy CT (DECT) has numerous advantages over conventional single-energy CT, including improved image quality, reduction of effect of scatter and other artefacts, and better material decomposition. Therefore, DECT has become the standard for inspection of objects containing multiple materials [1–2]. In this paper, we present a new CT technology: Adaptive Computed Tomography with Modulated-energy X-ray pulses (ACTM) [3]. ACTM is based on adaptive cargo radiography techniques [4–6] that have been developed over the last few years. To perform CT imaging, we propose to utilize the exact and fast Katsevich image reconstruction algorithm [7–12].Key enabling ACTM techniques are:•Linear accelerator with deep energy control.•Multi-energy spectrum in each slice provided by packets of short X-ray pulses with end-point energy ramp up (> 1 MHz rate of energy switching).•Fast detectors with reduced sensitivity to scatter radiation.•Detector readout with silicon photomultipliers (SiPM) provides time-resolved measurement of short X-ray pulses.•Electronics and an algorithm for automatic, dynamic adjustment of SiPM responsivity in detector channels provides increased dynamic range of X-ray imaging.•Real-time algorithm for X-ray pulse-by-pulse selection of high and low energy windows for dual-energy material decomposition.•Filtered Backprojection (FBP) helical image reconstruction based on the theoretically exact Katsevich algorithm.The ACTM method for dual- (or, multi-) energy CT mitigates the main disadvantages of the conventional interlaced approach:•Ambiguity and artifacts caused by sampling different regions due to motion of the object between interlaced pulses with distinct energies.•Distortion of CT image of the boundaries between regions with large difference in Z.•Small range of object thicknesses where material decomposition is valid.

The security market requirements for state-of-the-art mobile and portal radiography inspection systems include high imaging resolution (better than 5 mm line pair), penetration beyond 300 mm steel equivalent, material discrimination (three groups of Z) at speeds up to 16 km/h with 100% image sampling, low dose and small radiation exclusion zone. New research into radiography methods and systems has been actively pursued in order to achieve these challenging requirements. Recently, a significant portion of the R&D effort has been devoted to re-examining betatron based X-ray inspection systems. The advantages of the betatron-based inspection systems over conventional linac-based designs include small focal spot (which improves resolution), low weight and form-factor, a simpler control system and relatively low cost. A novel, low-dose Multi-Energy Betatron-based Cargo Inspection System, MEBCIS, presented in this paper relies on an innovative technique of extracting two X-ray pulses with lower-and higher-energies within a single betatron acceleration cycle (in contrast to conventional dual-energy betatrons with one X-ray pulse produced during separate betatron acceleration cycles). In addition to the new betatron, new types of fast X-ray Scintillation-Cherenkov detectors, rapid processing of detector signals, an adaptive detector feedback algorithm for control of the betatron, and algorithms for intelligent material discrimination are parts of the overall MEBCIS system. The key advantage of the MEBCIS concept is that the material discrimination data is acquired in a single scan line rather than two. Thus, for the same betatron pulse rate, the scan rate can be twice as fast (better throughput) or can be done with a lower dose, even without adaptive dynamic pulse adjustment. Application of these techniques will maximize material discrimination, penetration, and contrast resolution while simultaneously reducing dose to the environment, resulting in a smaller exclusion zone. Its minimal size and weight will allow MEBCIS to be placed on a lightweight truck chassis.

A disk-loaded waveguide (DLW) is the most common structure for compact linear accelerators working in a traveling wave (TW) regime. Among its advantages are high shunt impedance and manufacturing simplicity. The other popular structure is an on-axis coupled bi-periodical accelerating structure (BAS) that works in standing wave (SW) regime. Both the standing and the traveling wave regimes have their own advantages and disadvantages. The design of the hybrid accelerator with SW buncher and TW accelerating section presented in this paper unites the advantages of both regimes. For example, the buncher in the hybrid accelerator is shorter than in a pure TW accelerator, and it requires no solenoid; this structure is more technologically convenient as it does not require a circulator. The other way to combine the advantages of DLW and BAS is to design a magnetic coupled disk-loaded waveguide (DLW-M). This paper also presents the results of a survey study that analyzed the electrodynamical parameters of such a structure and compared them with those of DLW. The experimental data is also presented. Higher order modes, multipacting discharge and thermal simulations show that DLW-M structure is more preferable to classical DLW.

X-ray inspection systems for cargo containers, capable of performing Z analysis, are an actively evolving type of equipment for cargo inspections [1–3]. A linear electron accelerator with fast energy tuning, operating in the mode of interlacing low- and high-energy electron pulses, has been developed for use in such a system. The output electron energy in this accelerator can vary in the range of 3–15 MeV under software control. An X-ray radiographic image of a container is obtained in a monoenergetic mode with a beam energy of 9 MeV. Pulses with energies of 4 and 9 MeV are used to recognize materials inside a container (i.e., perform Z analysis). The standing-wave linear electron accelerator operates at a frequency of 2856 MHz, its pulse repetition frequency with different energies is 240 Hz, the pulse duration is 10 μs, and the beam energy in each pulse is >10 J.

In this paper Hellweg 2D code is introduced. It is a special tool for electron dynamics simulation in waveguide travelling wave accelerating structure. The underlying theory of this software is based on the differential equations of motion. The effects considered in this code include beam loading, space charge forces and external magnetic field. Hellweg 2D is capable of dealing with multisectional accelerators. Along with the analysis of electron linacs, this program is able to synthesize accelerating structures. This paper provides the comparison of the PARMELA, Hellweg 2D and experimental data of the existing facilities. The results of beam dynamics simulation in a hybrid accelerator with a standing wave (SW) buncher and travelling wave (TW) regular section are presented.

A new computer code for 3D simulation of multipacting phenomenon in axisymmetric and non-axisymmetric radio frequency (RF) structures is presented. The goal of the simulation is to determine resonant electron trajectories and electron multiplication in RF structure. Both SW and TW structures of normal and superconductivity have been studied. Simulation results are compared with theoretical calculations and experimental measurements.

The security market requirements for high throughput rail cargo radiography inspection systems include better than 5 mm line pair imaging resolution, penetration beyond 400 mm steel equivalent, scan speeds of up to 60 km/h, material discrimination (four groups of Z) in 100 % of cargo at speeds reaching 45 km/h, low dose and small radiation exclusioi zone. In order to achieve these requirements, which cannot be met t conventional dual energy radiography systems, a team lead by RadiaBeam Technologies, LLC (RBT) has initiated a research into new radiography methods and imaging detector materials with the goal of developing an Adaptive Railroad Cargo Inspection System (ARCIS). The ARCIS technical concept relies on linac-based, adaptive, ramped energy source of packets of short X-ray pulses sampled by a new type of fast X-ray detectors with rapid hardware processing for intelligent linac control, and advanced radiography image processing and material discrimination analysis. The following ARCIS key enabling technologies overcome the limitations of the conventional dual energy interlaced cargo inspection systems: • Multi-energy material discrimination in a single scan line provided by packets of short pulses from an X-ray source with end-point energy ramp up (> 1 MHz rate of energy switching); • Real-time intelligent setting of packet's maximum energy depend on X-ray attenuation in cargo; • Fast Scintillation-Cherenkov detectors with reduced sensitivity to scatter radiation; • Detector readout with Silicon Photomultiplier (SiPM) provides time-resolving of short X-ray pulses; • Self-control adaptive dynamic adjustment of SiPM responsivity in detector channel for increased dynamic range.

A novel high speed Adaptive Railroad Cargo Inspection System (ARCIS) is being developed at RadiaBeam Technologies. The ARCIS concept relies on linac-based, adaptive, ramped energy source of short X-ray packets of pulses, a new type of fast X-ray detectors, rapid processing of detector signals for intelligent control of the linac, and advanced radiography image processing. The requirements for this system include better than 5 mm line pair resolution, penetration greater than 400 mm of steel equivalent, scan speeds up to 60 km/h, material discrimination within 100% of image and minimal average dose. To meet these requirements a new S-band travelling wave linac with deep energy control has been designed. This paper discusses the linac design approach and its principal components, as well as engineering and manufacturing aspects.

A new eXtreme MATerial (XMAT) research facility is being proposed at Argonne National Laboratory to enable rapid in situ mesoscale bulk analysis of ion radiation damage in advanced materials and nuclear fuels. This facility combines a new heavy-ion accelerator with the existing high-energy X-ray analysis capability of the Argonne Advanced Photon Source. The heavy-ion accelerator and target complex will enable experimenters to emulate the environment of a nuclear reactor making possible the study of fission fragment damage in materials. Material scientists will be able to use the measured material parameters to validate computer simulation codes and extrapolate the response of the material in a nuclear reactor environment. Utilizing a new heavy-ion accelerator will provide the appropriate energies and intensities to study these effects with beam intensities which allow experiments to run over hours or days instead of years. The XMAT facility will use a CW heavy-ion accelerator capable of providing beams of any stable isotope with adjustable energy up to 1.2 MeV/u for 238U50+ and 1.7 MeV for protons. This energy is crucial to the design since it well mimics fission fragments that provide the major portion of the damage in nuclear fuels. The energy also allows damage to be created far from the surface of the material allowing bulk radiation damage effects to be investigated. The XMAT ion linac includes an electron cyclotron resonance ion source, a normal-conducting radio-frequency quadrupole and four normal-conducting multi-gap quarter-wave resonators operating at 60.625 MHz. This paper presents the 3D multi-physics design and analysis of the accelerating structures and beam dynamics studies of the linac.

We have developed a new design for a 176 MHz cw radio-frequency quadrupole (RFQ) for the SARAF upgrade project. At this frequency, the proposed design is a conventional four-vane structure. The main design goals are to provide the highest possible shunt impedance while limiting the required rf power to about 120 kW for reliable cw operation, and the length to about 4 meters. If built as designed, the proposed RFQ will be the first four-vane cw RFQ built as a single cavity (no resonant coupling required) that does not require π -mode stabilizing loops or dipole rods. For this, we rely on very detailed 3D simulations of all aspects of the structure and the level of machining precision achieved on the recently developed ATLAS upgrade RFQ. A full 3D model of the structure including vane modulation was developed. The design was optimized using electromagnetic and multiphysics simulations. Following the choice of the vane type and geometry, the vane undercuts were optimized to produce a flat field along the structure. The final design has good mode separation and should not need dipole rods if built as designed, but their effect was studied in the case of manufacturing errors. The tuners were also designed and optimized to tune the main mode without affecting the field flatness. Following the electromagnetic (EM) design optimization, a multiphysics engineering analysis of the structure was performed. The multiphysics analysis is a coupled electromagnetic, thermal and mechanical analysis. The cooling channels, including their paths and sizes, were optimized based on the limiting temperature and deformation requirements. The frequency sensitivity to the RFQ body and vane cooling water temperatures was carefully studied in order to use it for frequency fine-tuning. Finally, an inductive rf power coupler design based on the ATLAS RFQ coupler was developed and simulated. The EM design optimization was performed using cst Microwave Studio and the results were verified using both hfss and ansys . The engineering analysis was performed using hfss and ansys and most of the results were verified using the newly developed cst Multiphysics package.

The Californium Rare Isotope Breeder Upgrade is a new radioactive beam facility for the Argonne Tandem Linac Accelerator System (ATLAS). The facility utilizes a (252)Cf fission source coupled with an electron cyclotron resonance ion source to provide radioactive beam species for the ATLAS experimental program. The californium fission fragment distribution provides nuclei in the mid-mass range which are difficult to extract from production targets using the isotope separation on line technique and are not well populated by low-energy fission of uranium. To date the charge breeding program has focused on optimizing these mid-mass beams, achieving high charge breeding efficiencies of both gaseous and solid species including 14.7% for the radioactive species (143)Ba(27+). In an effort to better understand the charge breeding mechanism, we have recently focused on the low-mass species sodium and potassium which up to present have been difficult to charge breed efficiently. Unprecedented charge breeding efficiencies of 10.1% for (23)Na(7+) and 17.9% for (39)K(10+) were obtained injecting stable Na(+) and K(+) beams from a surface ionization source.

A new power coupler has been designed and is being prototyped by Argonne National Laboratory (ANL) for use with any of the ANL proposed superconducting (SC) half- or quarter-wave cavities for SARAF [1] and Project-X [2]. The 50 Ohm coaxial capacitive coupler is required to operate in the CW regime with up to 15 kW of forward power and under any condition for the reflected power. A key feature is a moveable copper plated stainless steel bellows which will permit up to 3 cm of axial stroke and adjustment of the external quality factor by roughly one order of magnitude in the range of 105 to 106. The mechanical and vacuum design includes two ceramic windows, one operating at room temperature and another at 70 Kelvin. The two window design allows the portion of the coupler assembled onto the SC cavity in the clean room to be compact and readily cleanable. Other design features include thermal intercepts to provide a large margin for RF heating and a mechanical guide assembly to operate cold and under vacuum with high reliability.