Yves Jongen

MYRRHA: A multipurpose accelerator driven system for research & development

SCK CEN, the Belgian Nuclear Research Centre, in partnership with IBA s.a., Ion Beam Applications, is designing an ADS prototype, MYRRHA, and is conducting an associated R&D programme. The project focuses primarily on research on structural materials, nuclear fuel, liquid metals and associated aspects, on subcritical reactor physics and subsequently on applications such as nuclear waste transmutation, radioisotope production and safety research on subcritical systems The MYRRHA system is intended to be a multipurpose R&D facility and is expected to become a new major research infrastructure for the European partners presently involved in the ADS Demo development. Ion Beam Applications is performing the accelerator development. Currently the preliminary conceptual design of the MYRRHA system is under way and an intensive R&D programme is assessing the points of greatest risk in the present design. This work will define the final choice of characteristics of the Facility. In this paper, we will report on the status of the predesign study as of June 2000 as well as on the methods and results of the R&D programme

Progress Report On the Iba Shi Small Cyclotron for Cancer-therapy

A proton therapy facility using a compact, high-field nonsuperconducting cyclotron was first presented by lon Beam Applications (IBA) at the PTCOG meeting in June 1990. In December 1990, funding was secured to start the design of a prototype at IBA. In October 1991 a collaboration agreement was signed between IBA and Sumitomo Heavy Industries (SHI). The main features of this accelerator were presented elsewhere [W. Beeckman et al., Nucl. Instr. and Meth. B56/57 (1991) 1201]. The induction profile in the vicinity of the extraction radius was improved by the introduction of a magnetic shunt resulting in a completely closed gap at the median plane. The extraction system is also described. First calculations on the central region were performed using a simplified 2-D model with stacking factors in order to describe its actual 3-D geometry. Two types of isocentric gantries, namely a scanning gantry as initially proposed and a scattering gantry, are currently designed. Their status is presented in this paper.

An electron cyclotron resonance ion source for efficient production of radioactive ion beams

A single stage electron cyclotron resonance (ECR) ion source has been developed for the radioactive ion beam facility in Louvain-la-Neuve. The source was first tested with an off-line test separator using calibrated leaks of neon, nitrogen and carbon dioxide. The lingering time in the source, due to atoms sticking to the walls of the ion source, has been studied. The maximum efficiencies obtained are 52% for Ne-20(1+), 20% for N-15(1+) and 15% for C-12(1+). A N-13(1+) (T1/2 = 9.96 m) efficiency of 8% has been measured on-line.

X-ray treatment at 5 MeV and above

Abstract There is agreement in the scientific community that X-ray treatment of food at 7.5 MeV can be safe. Possible process improvements for treating at higher than 5 MeV X-rays have been re-visited. Monte Carlo methods have been applied to simulate the X-ray conversion process and to calculate dose distributions in homogeneous phantoms. Experimental data obtained using X-rays produced with a Rhodotron TT200 at 5 and 10 MeV verifies a representative set of data which is calculated with the presented method. With this qualified Monte Carlo tool, calculations at 7.5 MeV incident electron energy were performed. The analysis gives special attention to higher photon yield, improved product penetration, as well as surface and edge effects.

The Rhodotron, a New 10-mev, 100-kw, Cw Metric Wave Electron-accelerator

New applications for high energy, high current electron beam processing are continually expanding. Today, however, 10 MeV rf electron linacs are frequently limited to an average beam power of only 20 or 30 kW. To achieve higher beam power, CW operation and the use of lower frequencies are necessary. In the last years, the principle for a new kind of electron accelerator was developed by the Atomic Energy Agency (CEA) in France. This accelerator is based on the principle of recirculating a beam throughout a single coaxial cavity resonating in metric waves. A 3.3 MeV, 4 mA prototype has been built and successfully tested. The industrial accelerator developed by IBA in collaboration with the CEA is a 10 MeV, 100 kW beam power unit with an additional beam exit at 5 MeV. The cavity, made of copper-plated steel, will resonate at 107.5 MHz. A rf power of 100 kW is needed to produce an electric field allowing an energy gain of 1 MeV per crossing. In addition, 100 kW of power is needed for acceleration. The 200 kW output amplifier uses a 100 kW plate dissipation tetrode (TH 681 from Thomson-CSF) in a grounded grid configuration. In this paper, the design of the new model as well as the prototype manufacturing schedule are presented in more detail.

THE SELF-EXTRACTING CYCLOTRON

At IBA a compact 14 MeV H+ cyclotron has been constructed. A special feature of this cyclotron is that there is no electrical deflector installed, i.e. the beam is self-extracted. The goal is to obtain high beam currents with good extraction efficiency without the need of single turn extraction. This is achieved with two ingredients: i) a special shaping of the magnetic field, showing a very steep fall-off near the outer radius of the pole and ii) the creation of a large turn-separation on the last turn. The pole gap has a quasi-elliptical shape, allowing for the steep fall-off of the magnetic field by the machining of a groove in one of the poles at a radius where the gap is small. The large turn separation is obtained by either the use of harmonic coils or by permanent magnet field bumps placed in two opposite valleys. Both methods have been tested and give good results with an extraction efficiency of 80%. The concept and layout of the machine is explained. The status of the project is outlined. First ...

PROGRESS TOWARD AN EXPERIMENT TO STUDY THE EFFECT OF RF GROUNDING IN AN INTERNAL ION SOURCE ON AXIAL OSCILLATIONS OF THE BEAM IN A CYCLOTRON

For practical reasons, the chimney of a cyclotron’s internal ion source often has RF grounds at only one end, despite the desire for an axially symmetric electric field throughout the cyclotron. It is generally impractical or impossible to measure the shape of the electric fields around the chimney, but one of the authors (H. Blosser of Michigan State University) has observed that in three cyclotrons of similar design built at the National Superconducting Cyclotron Laboratory, the machine with the least axial oscillation of the beam was the only one designed with median plane symmetry in its RF grounding. Based on this he suggests that RF currents in an asymmetrically grounded chimney give the beam an initial vertical kick which starts a coherent oscillation about the median plane. This hypothesis is being tested in the Ion Beam Applications C235 proton therapy cyclotron which uses an internal hot-cathode PIG ion source that is normally grounded only at the bottom. The test uses an insert which can be temporarily installed in the upper yoke hole of the cyclotron in order to make an RF grounding connection to the top of the chimney. A scintillation probe is then used to study the axial beam position on successive turns with and without the symmetric RF grounding.

The proton therapy system for the NPTC: Equipment description and progress report

At the beginning of 1994, the Massachusetts General Hospital (MGH) of the Harvard Medical School in Boston (MA, USA) a pioneer in proton therapy since 1959, selected a team led by Ion Beam Applications SA (IBA) to supply the proton therapy equipment of its new Northeast Proton Therapy Centre (NPTC). The IBA integrated system includes a compact 235 MeV isochronous cyclotron, a short energy selection system transforming the fixed energy beam extracted from the cyclotron into a variable energy beam, one or more isocentric gantries fitted with a nozzle, a system consisting of one or more horizontal beam lines, a global control system including an accelerator control unit and several independent but networked therapy control stations, a global safety management system, and a robotic patient positioning system. The present paper presents the equipment being built for the NPTC.

Overview of the IBA accelerator-based BNCT system

During the last few years, IBA started the development of an accelerator-based BNCT system. The accelerator is a Dynamitron built by RDI in USA and will produce a 20 mA proton beam at 2.8 MeV. Neutrons will be produced by the (7)Li(p,n)(7)Be nuclear reaction using a thin lithium target. The neutron energy spectrum will be tailored using a beam shaping assembly. This overview presents the current status of the system: after a description of every component, some design issues, solutions and experimental tests will be discussed.

The IBA state-of-the-art proton therapy system, performances and recent results

In recent years IBA has continued its development of state-of-the-art systems for Proton Therapy. While the machine performance at the NPTC is such that all clinical specifications are met, IBA has continued to improve the proposed equipment to set even higher standards. Improvements in the ion source control, gantries, and patient alignment systems will be addressed in the oral presentation and the first results obtained with the Pencil Beam Scanning algorithm will be presented.