12 research outputs found
TERA high gradient test program of RF cavities for medical linear accelerators
The scientific community and the medical industries are putting a considerable effort into the design of compact, reliable and cheap accelerators for hadrontherapy. Up to now only circular accelerators are used to deliver beams with energies suitable for the treatment of deep seated tumors. The TERA Foundation has proposed and designed a hadrontherapy facility based on the cyclinac concept: a high gradient linear accelerator placed downstream of a cyclotron used as an injector. The overall length of the linac, and therefore its final cost, is almost inversely proportional to the average accelerating gradient achieved in the linac
behaviour of advanced materials impacted by high energy particle beams
Beam Intercepting Devices (BID) are designed to operate in a harsh radioactive environment and are highly loaded from a thermo-structural point of view. Moreover, modern particle accelerators, storing unprecedented energy, may be exposed to severe accidental events triggered by direct beam impacts. In this context, impulse has been given to the development of novel materials for advanced thermal management with high thermal shock resistance like metal-diamond and metal-graphite composites on top of refractory metals such as molybdenum, tungsten and copper alloys. This paper presents the results of a first-of-its-kind experiment which exploited 440 GeV proton beams at different intensities to impact samples of the aforementioned materials. Effects of thermally induced shockwaves were acquired via high speed acquisition system including strain gauges, laser Doppler vibrometer and high speed camera. Preliminary information of beam induced damages on materials were also collected. State-of-the-art hydrodynamic codes (like Autodyn®), relying on complex material models including equation of state (EOS), strength and failure models, have been used for the simulation of the experiment. Preliminary results confirm the effectiveness and reliability of these numerical methods when material constitutive models are completely available (W and Cu alloys). For novel composite materials a reverse engineering approach will be used to build appropriate constitutive models, thus allowing a realistic representation of these complex phenomena. These results are of paramount importance for understanding and predicting the response of novel advanced composites to beam impacts in modern particle accelerators
Cyclinac Medical Accelerators Using Pulsed C 6+ /H 2 + Ion Sources
ABSTRACT: Charged particle therapy, or so-called hadrontherapy, is developing very rapidly. There is large pressure on the scientific community to deliver dedicated accelerators, providing the best possible treatment modalities at the lowest cost. In this context, the Italian research Foundation TERA is developing fast-cycling accelerators, dubbed 'cyclinacs'. These are a combination of a cyclotron (accelerating ions to a fixed initial energy) followed by a high gradient linac boosting the ions energy up to the maximum needed for medical therapy. The linac is powered by many independently controlled klystrons to vary the beam energy from one pulse to the next. This accelerator is best suited to treat moving organs with a 4D multi-painting spot scanning technique. A dual proton/carbon ion cyclinac is here presented. It consists of an Electron Beam Ion Source, a superconducting isochronous cyclotron and a high-gradient linac. All these machines are pulsed at high repetition rate (100-400 Hz). The source should deliver both C 6+ and H 2 + ions in short pulses (1.5 μs flat-top) and with sufficient intensity (at least 10 8 fully stripped carbon ions at 300 Hz). The cyclotron accelerates the ions to 120 MeV/u. It features a compact design (with superconducting coils) and a low power consumption. The linac has a novel C-band high gradient structure and accelerates the ions to variable energies up to 400 MeV/u. High RF frequencies lead to power consumptions which are much lower than the ones of synchrotrons for the same ion extraction energy. This work is part of a collaboration with the CLIC group, which is working at CERN on highgradient electron-positron colliders
High gradient test of a 3 GHz single-cell cavity
Proton and carbon ion beams present advantageous depth-dose distributions with respect to X-rays. Carbon ions allow a better control of "radioresistant" tumours due to their higher biological response. For deep-seated tumours proton and carbon ion beams of some nA and energies of about 200 MeV and 400 MeV/u respectively are needed. For these applications TERA proposed the "cyclinac": a high-frequency linac which boosts the hadrons accelerated by a cyclotron. The dimensions of the complex can be reduced if higher accelerating gradients are achieved in the linac. To test the maximum achievable fields, a 3 GHz cavity has been built by TERA. The 19 mm-long cell is foreseen to be excited at 200 Hz by 3 us RF pulses and should reach a 40 MV/m accelerating gradient, which corresponds to a peak surface electric field Es of 260 MV/m. In a first high-power test performed at CTF3 the cell was operated at 50 Hz with a maximum peak power of 1 MW. The maximum Es achieved was above 350 MV/m. The breakdown rate at these field values was around 10-1 bpp/m. The maximum value of the modified Poynting vector is close to the best values achieved by high gradient structures at 12 and 30 GHz