The Superconducting Ion Gantry (SIG) project is the contribution from INFN (the Italian National Institute for Nuclear Physics) to the international SIGRUM project with the aim of exploring new ...technological solutions for the critical elements of a 430 MeV/u carbon ion gantry. The project includes the design and construction of a cos<inline-formula><tex-math notation="LaTeX">\theta</tex-math></inline-formula> 4 T superconducting dipole demonstrator magnet whose main scope is to prove the feasibility of winding and assembling an accelerator magnet type with a relatively small radius of curvature (1.65 m). In addition to the complexity due to the curvature, the target field ramp rate is 0.4 T/s and the cooling system must not adopt liquid helium. This paper discusses the design activities carried out in the last year on the electromagnetic and thermal domains and reports on the present concepts and infrastructure for the first winding trials.
A collaboration between CERN, CNAO, INFN, and MedAustron has been formed aiming at designing a light rotating gantry suitable for hadron therapy based on 430 MeV/n carbon ion beams. After a first ...design for a 3 T dipole field, as the backbone of the gantry magnetic system, now the collaboration is looking at an alternative design, for at least 4 T field with a faster ramp rate. The magnet is designed according to the cosθ layout to be wound with Nb-Ti superconducting Rutherford cable. One of the main challenges is the very small curvature radius of 1.65 m with a relatively large aperture, of 70-90 mm. Another challenge is the use of indirect cooling despite the cycling operation of 0.4 T/s. The paper reports the preliminary investigation for a 4.5 T dipole. The design will be followed by the construction of a 1 m long demonstrator to be manufactured and tested at INFN (LASA laboratory) in about three years. The conductor is a Rutherford cable of 2.6 µm Nb-Ti filament size, embedded in a Cu-Mn alloy matrix. The resulting gantry is very compact: the collaboration is working on integration between gantry structure and magnets to allow reducing the rotating weight in the range 50-80 tons, which is a factor 4 to 5 less than the present state-of-the-art.
In the framework of the euro SIG project and within an international collaboration between CNAO, CERN, INFN, and MedAustron, the design of a novel gantry for hadron therapy based on superconducting ...magnets and a downstream scanning system has been undertaken. The choice of placing the scanning system downstream of the last superconducting dipole plays a crucial role in the overall layout of the gantry, having a direct impact on its radius, weight, and cost. The proposed design for the scanning system considers two separate normal-conducting scanning magnets with a central field in the order of 1 T, three times higher than the current state-of-the-art scanning magnets for hadron therapy. Such a magnetic field value for a fast-pulsed magnet poses interesting questions regarding non-linearities due to the yoke saturation, hysteretic effects, and eddy currents. In this context, it is important to develop reliable models to study the behavior of the magnet at various levels of current and magnetic field. For this reason, we implemented two and three-dimensional simulations of a short dipole with FeCo yoke and we validated them against experimental measurements. In this paper, we focus on the modelization of the hysteretic behavior of this magnet, providing insight into the feasibility of proposed scanning magnets.
As part of major European collaborations focused on the study of newly developed superconducting magnets for ion therapy, Istituto Nazionale di Fisica Nucleare (INFN) is directly involved through the ...Superconducting Ion Gantry (SIG) project. In ion therapy, rotating gantry systems are critical to better preserve healthy tissues during treatments, but they are typically huge and heavy structures: a superconducting version of them would lead to lighter and more viable solutions. SIG aims to design, in collaboration with Centro Nazionale di Adroterapia Oncologica (CNAO) and Conseil Européen pour la recherché Nucléaire (CERN), the main superconducting magnets for a 430 MeV/u carbon ion gantry. The main purpose of the project is to study the bending dipoles of this system: they are expected to have a curvature of 1.65 m, aperture of 80 mm, magnetic field of 4 T, ramp rates up to 0.4 T/s and Nb-Ti coils. Among the goal of SIG is the construction of a 30-degree demonstrator to prove the feasibility of these magnets. The plan is to design cos <inline-formula><tex-math notation="LaTeX">\theta</tex-math></inline-formula> magnets, but we are currently working on an alternative strategy with cross section in block coil configuration. These parameters are very challenging and this solution could make it easier to achieve the required goals. In this work the optimized cross section and a novel winding technique for high curvature block coil magnets are presented.
Abstract
The design of smaller and less costly gantries for carbon ion particle therapy represents a major challenge to the diffusion of this treatment. Here we present the work done on the linear ...beam optics of possible gantry layouts, differing for geometry, momentum acceptance, and magnet technology, which share the use of combined function superconducting magnets with a bending field of 4 T. We performed parallel– to–point and point–to–point optics matching at different magnification factors to provide two different beam sizes at the isocenter. Moreover, we considered the orbit distortion generated by magnet errors and we introduced beam position monitors and correctors. The study, together with considerations on the criteria for comparison, is the basis for the design of a novel and compact gantry for hadrontherapy.
Positron emission tomography is one of the most mature techniques for monitoring the particles range in hadron therapy, aiming to reduce treatment uncertainties and therefore the extent of safety ...margins in the treatment plan. In-beam PET monitoring has been already performed using inter-spill and post-irradiation data, i.e. while the particle beam is off or paused. The full beam acquisition procedure is commonly discarded because the particle spills abruptly increase the random coincidence rates and therefore the image noise. This is because random coincidences cannot be separated by annihilation photons originating from radioactive decays and cannot be corrected with standard random coincidence techniques due to the time correlation of the beam-induced background with the ion beam microstructure. The aim of this paper is to provide a new method to recover in-spill data to improve the images obtained with full-beam PET acquisitions. This is done by estimating the temporal microstructure of the beam and thus selecting input PET events that are less likely to be random ones. The PET detector we used was the one developed within the INSIDE project and tested at the CNAO synchrotron-based facility. The data were taken on a PMMA phantom irradiated with 72 MeV proton pencil beams. The obtained results confirm the possibility of improving the acquired PET data without any external signal coming from the synchrotron or ad hoc detectors.
Next generation ion therapy magnets both for gantry and for accelerator (synchrotron) are under investigation in a recently launched European collaboration that, in the frame of the European H2020 ...HITRI plus and I.FAST programmes, has obtained some funding for work packages on superconducting magnets. Design and technology of superconducting magnets will be developed for ion therapy synchrotron and -especially- gantry, taking as reference beams of 430 MeV/nucleon ions (C-ions) with 10 10 ions/pulse. The magnets are about 60-90 mm diameter, 4 to 5 T peak field with a field change of about 0.3 T/s and good field quality. The paper will illustrate the organization of the collaboration and the technical program. Various superconductor options (LTS, MgB 2 or HTS) and different magnet shapes, like classical CosTheta or innovative Canted CosTheta (CCT), with curved multifunction (dipole and quadrupole), are under evaluation, CCT being the baseline. These studies should provide design inputs for a new superconducting gantry design for existing facilities and, on a longer time scale, for a brand-new hadron therapy centre to be placed in the South East Europe (SEEIIST project).
The Superconducting Ion Gantry (SIG) project aims to design, construct, and test a curved superconducting dipole demonstrator magnet for an ion gantry (up to a rigidity of 6.6 Tm). The main ...demonstrator magnet parameters are a dipolar field of 4 T generated into a toroidal aperture with an 80 mm diameter, 1.65 m curvature radius, and 30° angular sector. The project is inserted in the framework of the EuroSIG collaboration among CNAO, CERN, INFN, and MedAustron. Within this collaboration, the main goal of SIG is to perform a feasibility study of winding and assembling cos-<inline-formula><tex-math notation="LaTeX">\theta</tex-math></inline-formula> coils with a small curvature radius. In addition, a parallel program at CERN is dedicated to the study of the indirect cooling problem through the construction of a straight thermal demonstrator magnet sharing the SIG cross-section. The basic idea behind these programs is to check whether the vast experience of the community on superconducting accelerator magnets design can lead to a breakthrough in the gantry magnets domain. This article shows the main elements of the conceptual design of the SIG magnet and reports on the first winding trial performed at the LASA laboratory, in Milan, with a copper dummy cable. Moreover, possible solutions for the winding, curing, and impregnation of highly curved cos<inline-formula><tex-math notation="LaTeX">\theta</tex-math></inline-formula> coils are discussed.
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