Purpose: To describe a concept of a compact electron accelerator for external radiation therapy with variable energy in the range of 6 - 20 MeV, based on linotron principle. Methods: Beam dynamics simulation using the CST and MAD-X code. Various optimization methods of multi-parameter problem. Results: Our accelerator differs from the Reflexotron in a number of essential details: a much more compact and more efficient C-band accelerating structure, optimized for the high capture efficiency, narrow energy and phase spectra, and low transverse emittance; magnetic mirror with fixed field based on rare-earth permanent magnets; three-electrode electron gun with off-axis placement of the cathode with a current regulated in the range of two orders of magnitude. These improvements allow the possibility to: adjust the accelerated beam current in a wide range in accordance with the required energy; reduce parasitic losses of the beam current and the associated parasitic radiation; eliminate the risk of setting an erroneous energy value; significantly reduce the dimensions of the accelerator and simplify its operation. Conclusions: We presented the results of calculation of the electron accelerator for external radiation therapy in the energy range of 6 - 20 MeV. The accelerator is based on the principle of double beam acceleration in the same accelerating structure, which allows to control the beam energy in a wide range, reduce RF power consumption and the dimensions of the accelerator, and, therefore, reduce its cost. The results can be used to develop the design of the accelerator on the platform of the KLT-6 complex created by ROSATOM.
A high-intensity continuous wave (CW) radio frequency quadrupole (RFQ) accelerator is designed for boron neutron capture therapy (BNCT). The transmission efficiency of a 20-mA proton beam accelerated from 30 keV to 2.5 MeV can reach 98.7% at an operating frequency of 200 MHz. The beam dynamics has good tolerance to errors. By comparing the high-frequency parameters of quadrilateral and octagonal RFQ cross-sections, the quadrilateral structure of the four-vane cavity is selected owing to its multiple advantages, such as a smaller cross section at the same frequency and easy processing. In addit…
Cancer therapy using protons and heavier ions such as carbon has demonstrated advantages over other radiotherapy treatments. To bring about the next generation of clinical facilities, the requirements are likely to reduce the footprint, obtain beam intensities above 1E10 particles per spill, and achieve faster extraction for more rapid, flexible treatment. This review follows the technical development of ion therapy, discussing how machine parameters have evolved, as well as trends emerging in technologies for novel treatments such as FLASH. To conclude, the future prospects of ion therapy acc…
Novel path towards compact laser ion accelerators for hadron therapy: Tenfold energy increase in laser-driven multi-MeV ion generation using a gas target mixed with submicron clusters
The LIGHT (Linac for Image-Guided Hadron Therapy) project was initiated to develop a modular proton accelerator delivering beam with energies up to 230 MeV for cancer therapy. The machine consists of three different kinds of accelerating structures: RFQ (Radio-Frequency Quadrupole), SCDTL (Side Coupled Drift Tube Linac) and CCL (Coupled Cavity Linac). These accelerating structures operate at 750 MHz (RFQ) and 3 GHz (SCDTL, CCL). The accelerator RF signals are generated, distributed, and controlled by a Low-Level RF (LLRF) system. The LIGHT LLRF system is based on a commercially available solut…
The determination of relative stopping power (RSP) via proton computed tomography (pCT) of a patient is dependent in part on the knowledge of the incoming proton kinetic energies; the uncertainty in these energies is in turn determined by the proton source -- typically a cyclotron. Here we show that reducing the incident proton beam energy spread may significantly improve RSP determination in pCT. We demonstrate that the reduction of beam energy spread from the typical 1.0% (at 70MeV) down to 0.2%, can be achieved at the proton currents needed for imaging at the Paul Scherrer Institut 230MeV c…
In this paper, a novel concept combining a fixed field alternating gradient accelerator with time-varying quadrupoles is presented which solves some of the major problems of conventional fixed field accelerators. This concept combines a stable racetrack fixed field configuration with dispersion free straight sections to enable continuous variable energy extraction. In the long straight sections, a time-varying synchrotron-like alternating gradient focusing structure makes it possible for the first time to correct the beam optics of an FFA accelerator in order to heuristically maximize the beam…
High-frequency linear accelerators are very suitable for carbon ion therapy, thanks to the reduced operational costs and the high beam quality with respect to synchrotrons, which are presently the only available technology for this application. In the framework of the development of a new linac for carbon ion therapy, this article describes the design of a compact 750 MHz Radio Frequency Quadrupole (RFQ) with trapezoidal vanes. A new semi-analytic approach to design the trapezoidal-vane RFQ is introduced together with the relevant beam dynamics properties. The RFQ is split into two decoupled r…
The PIP-II accelerator is a proposed upgrade to the Fermilab accelerator complex that will replace the existing, 400 MeV room temperature LINAC with an 800 MeV superconducting LINAC. Part of this upgrade includes a new injection scheme into the booster that levies tight requirements on the LLRF control system for the cavities. In this paper we discuss the challenges of the PIP-II accelerator and the present status of the LLRF system for this project.
Conventional cancer therapies include surgery, radiation therapy, chemotherapy, and, more recently, immunotherapy. These modalities are often combined to improve the therapeutic index. The general concept of radiation therapy is to increase the therapeutic index by creating a physical dose differential between tumors and normal tissues through precision dose targeting, image guidance, and high radiation beams that deliver radiation dose with high conformality, e.g., protons and ions. However, treatment and cure are still limited by normal tissue radiation toxicity, with many patients experienc…
The Polarized Electrons for Polarized Positrons (PEPPo) experiment has demonstrated the efficient transfer of polarization from electrons to positrons produced by the bremsstrahlung radiation of a polarized electron beam in a high-$Z$ target. Positron polarization up to 82\% has been measured for an initial electron beam momentum of 8.19 MeV/$c$, limited only by the electron beam polarization. Combined with the high intensity and high polarization performances of polarized electron sources, this technique extends efficient polarized positron capabilities from GeV to MeV electron accelerators. …
Ion sources are key components of accelerators devoted to different types of medical applications: hadron-therapy facilities (accelerating protons or carbon ions), high-intensity accelerators for boron-neutron capture therapy (using intense proton beams), and facilities for isotope production (using different ion species). The three types of application present different requirements in terms of ion beam quality, reproducibility, and beam availability. Different characteristics of ion sources will be described, along with the reasons why they are particularly interesting or largely used.
We reconstruct spectra of secondary x-rays generated from a 500 MeV - 2 GeV laser plasma electron accelerator. A compact (7.5 $\times$ 7.5 $\times$ 15 cm), modular x-ray calorimeter made of alternating layers of absorbing materials and imaging plates records the single-shot x-ray depth-energy distribution. X-rays range from few-MeV inverse Compton scattered x-rays to $\sim$100 MeV average bremsstrahlung energies and are characterized individually by the same calorimeter detector. Geant4 simulations of energy deposition from mono-energetic x-rays in the stack generate an energy-vs-depth respons…
Proton beam therapy has been developed to irradiate the tumor with higher precision and dose conformity compared to conventional X-ray irradiation. The dose conformity of this treatment modality may be further improved if narrower proton beams are used. Still, this is limited by multiple Coulomb scattering of protons through tissue. The primary aim of this work was to develop techniques to produce narrow proton beams and investigate the resulting dose profiles. We introduced and assessed three different proton beam shaping techniques: 1) metal collimators (100/150~MeV), 2) focusing of conventi…
The physical and clinical benefits of charged particle therapy (CPT) are well recognised and recent developments have led to the rapid emergence of facilities, resulting in wider adoption worldwide. Nonetheless, the availability of CPT and complete exploitation of dosimetric advantages are still limited by high facility costs and technological challenges. There are extensive ongoing efforts to improve upon these, which will lead to greater accessibility, superior delivery, and therefore better treatment outcomes. Several of these aspects can be addressed by developments to the beam delivery sy…
A compact beam-profile monitor was constructed using a linear contact image sensor attached to a plastic scintillator and tested using a 230 MeV proton beam. The results indicate that the beam distribution can be obtained in real-time, and the beam position with a precision of up to 0.03 mm. The compactness and high precision of the device hold considerable potential for it to be used as a beam-profile monitor and offline, daily quality assurance monitor in hadron therapy.
We report the initial considerations of using linearly polarized optical transition radiation (OTR) to characterize the electron beams of laser plasma accelerators (LPAs) such as at the Univ. of Texas at Austin. The two LPAs operate at 100 MeV and 2-GeV, and they currently have estimated normalized emittances at ~ 1-mm mrad regime with beam divergences less than 1/γ and beam sizes to be determined at the micron level. Analytical modeling results indicate the feasibility of using these OTR techniques for the LPA applications.
In this paper we discuss the possibility to generate and accelerate proton nanobeams in fully dielectric laser-driven accelerators (p-DLAs). High gradient on-chip optical-power dielectric laser accelerators (DLAs) could represent one of the most promising way towards future miniaturized particle accelerator. A primary challenge for DLAs are small beam apertures having a size of the order of the driving laser wavelength where low charge high-repetition (or also CW) ultralow emittance nanobeams have to be transported. For electrons beams generation and acceleration, intense research activities a…
Compact accelerator-based neutron source facilities are garnering attention and play an important and expanding role in material and engineering sciences, as well as in neutron science education and training. Neutrons are produced by bombarding a low-energy proton beam onto a beryllium or lithium target. In such an accelerator-based neutron source, a radio frequency quadrupole (RFQ) is usually utilized to accelerate a high-intensity proton beam to a few MeV. This study mainly covers the high-frequency structure design optimizations of a 4-vane RFQ with pi-mode stabilizer loops (PISLs) and its …
AREAL (Advanced Research Electron Accelerator Laboratory) is an electron linear accelerator with a laser driven RF gun constructed at CANDLE Synchrotron Research Institute. After the successful operation of the gun section at 5 MeV, a program of facility energy growth up to 50 MeV has been launched, which includes the construction of two advanced experimental stations for the generation of middle infrared and THz radiation. This paper presents the design of these stations and gives the characteristics of expected radiation based on numerical and theoretical studies.
MedAustron is a synchrotron-based particle therapy centre located in Wiener Neustadt, Austria. It features three irradiation rooms for particle therapy, where proton beams with energies up to 252.7 MeV and carbon ions of up to 402.8 MeV/u are available for cancer treatment. In addition to the treatment rooms, MedAustron features a unique beamline exclusively for non-clinical research (NCR). This research beamline is also commissioned for proton energies up to 800 MeV, while available carbon ion energies correspond to the ones available in the clinical treatment rooms. Based on the requirements…
The two-temperature relativistic electron spectrum from a low-density ($3\times10^{17}$~cm$^{-3}$) self-modulated laser wakefield accelerator (SM-LWFA) is observed to transition between temperatures of $19\pm0.65$ and $46\pm2.45$ MeV at an electron energy of about 100 MeV. When the electrons are dispersed orthogonally to the laser polarization, their spectrum above 60 MeV shows a forking structure characteristic of direct laser acceleration (DLA). Both the two-temperature distribution and the forking structure are reproduced in a quasi-3D \textsc{Osiris} simulation of the interaction of the 1-…
In this paper, we give some guidelines for the design of linear accelerators, with special emphasis on their use in a hadron therapy facility. We concentrate on two accelerator layouts, based on linacs. The conventional one based on a linac injecting into a synchrotron and a all-linac solution based on high gradient high frequency RF cavities.
