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Irradiations Rooms

Multidisciplinary irradiation beamlines: CATANA and 0°

Multidisciplinary applications represent today a growing part of beam time requests by external (and internal) Users aiming to perform experiments with proton and ion beams accelerated at several tens of MeV/n. Such kind of beams are delivered by the Superconducting Cyclotron (SC) installed at LNS, that is able to accelerate ion beams up to 80 MeV/n. Multidisciplinary applications involve a great variety of fields, including medical applications, radiation damage and space applications. Therefore, irradiation beam lines developed for such purposes have to provide a set of devices for precise beam transport and shaping and for accurate control of the main beam parameters, in order to offer the User the possibility to perform different kind of experiments: dosimetric measurements, radiobiology experiments, test and characterization of detectors for dosimetry, imaging and diagnostics. According to these requirements, a multidisciplinary beam line has to be as much as possible versatile and must be equipped with all the necessary detectors and experimental setups that shall be easily mounted and dismounted between different experiments. At LNS two irradiation beam lines are dedicated to multidisciplinary activities and they, in a complementary way, meet most of the mentioned requirements: the CATANA (Centro di AdroTerapia e Applicazioni Nucleari Avanzate) beam line and the 0° beam line.
The CATANA facility has been realized with the aim of treating ocular melanomas with 62 MeV proton beams accelerated by the SC (Figure 1). Thanks to the experience acquired so far, concerning beam transport/shaping and precise dosimetric measurements, the facility is being used also for multidisciplinary experimental activities. Only in-air proton beams can be transported and shaped with a fixed passive system, and the most precise and advanced dosimetric techniques are currently employed for the beam calibration in terms of absolute dose.
The 0° beam line is much more versatile, indeed ion beams can be also transported along this beam line, and the possibility to perform measurements both in vacuum and in air is provided (Figure 2).
Most of the in-air beam transport elements, diagnostics/dosimetry detectors together with the data acquisition system are shared by the two beam lines. In particular, in both cases the beam exits in air through a 50 μm kapton window. Just before the exit window, a first scattering foil made of 15 μm tantalum is placed, with the tasks of spreading the beam and on-line monitoring the beam current. The CATANA and 0° transport beam lines are very similar except for the in-air length, respectively 2.8 m and 1.8 m (the second one can be modified). Actually, the box hosting energy range shifters and energy modulators is present only in the CATANA beam line: range shifters and modulators are plastic passive elements adopted in the proton clinical practice to adjust the maximum proton energy and/or its distribution, according to the patient specific tumour location and thickness. Along the in air transport, in both of the two beam lines, particles pass through a set of plastic collimators and the 50 cm long brass tube ending with an easy to change final collimator of different apertures (between 1 and 30 mm in diameter). The plastic collimators eliminate the particles with large scattering angle and provide the shield from the produced secondary neutrons. The brass tube enables the final beam collimation and creates beams with negligible divergence. At the irradiation point, the beams have circular spot size and flat fluence distribution. A set of two transmission free-air ionization chambers, placed along the beam transport lines, upstream the final brass collimator, provide full control of proton/ion beam doses during irradiations. The two chambers are independently calibrated with respect to the absolute dose measure performed with a Markus type ionization chamber, following the recommended procedures of the International Atomic Energy Agency (IAEA) TRS-398 (IAEA 2000). Moreover, different detectors for beam profile measurements are provided, in order to guarantee a beam flatness within 3% and 15%, respectively, in the CATANA and 0° beam line. Proton and ion fluence/dose can be measured with high level of accuracy and reproducibility, thanks to a precise calibration procedure and to a remote system able to deliver a specific amount of dose per sample. Beam monitor detectors are also installed with the aim of on-line monitoring the beam intensity, with an interlock system able to automatically stop the beam in case of high intensity fluctuations.
Beam currents up to about 10 nA can be used in both the beam lines and also very low intensity beams can be transported. Moreover, the 0° beam line has been recently upgraded in order to transport beams up to 100 nA and perform high-intensity irradiations for radiation damage measurements and characterization of detectors to be used in high luminosity facilities.
Special care has been devoted in recent years for radiobiology experiments: cell sample irradiations with proton and light ion beams can be carried out with high level of dosimetric precision and at different dose rates (between 0.01 and 50 Gy/min). Moreover, a remotely controlled position system is provided to the Users in order to irradiate several cell samples in a single experimental session, sensibly reducing the irradiation time. The system can be easily handled and it is versatile so that different sample shapes and sizes can be irradiated with a sub-millimetric precision. A cell biology laboratory is also present at LNS and at disposal of the Users for cell growth and preliminary irradiation procedures. It is equipped with all the typical devices necessary to perform such a kind of experiments, like centrifuge, incubator, sterilizer and microscope. Recently, a laboratory dedicated to in-vivo preclinical studies with mice has been also realized and it will be soon in operation.
Both the CATANA and 0° beam lines have been simulated in details with the Monte Carlo code Geant4, so that all the information on the main beam parameters (energy, fluence, spatial distribution, dose, LET) at different points can be preliminary provided to the Users (upon request) to better set-up the experiment. Moreover, support for the subsequent data analysis can be also provided in collaboration with the LNS group who is in charge of the Monte Carlo simulation.
Some of the mentioned procedures, especially the ones related to precise dosimetric measurements, can be preliminary requested and discussed in collaboration with the LNS dosimetry group.

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