Search

In a medical accelerator, real-time monitoring systems of the beam and dose delivered to the patient are mandatory. In this work, we present a compact current profile detector that has been designed and tested in the framework of the TOP-IMPLART (Intensity Modulated Proton Linear Accelerator for RadioTerapy) project. This project foresees the realization of a proton linear accelerator, currently under construction at ENEA Frascati, for proton therapy applications. The linac produces a pulsed proton beam with 3 µs duration at 50 Hz repetition rate with a pulse current between 0.5 and 50 μA. A large dynamic range and spatial constraints make the use of usual noninterceptive beam diagnostics unfeasible. Therefore, the use of a beam current monitor based on a passive RF cavity working in the TM010 mode has been proposed. This paper reports the electromagnetic design of the device guided by a simplified analytical model. A prototype of such a device has been realized, characterized, and tested on the linac with a 35 MeV beam varying the beam current. The test results in air and in vacuum, together with the signal detection systems used, are presented.

Solid-state radiation detectors based on the visible photoluminescence of radiation-induced F2 and F3+ color centers in lithium fluoride crystals have been used for advanced diagnostics of 18 and 27 MeV proton beams, produced by the TOP-IMPLART linear accelerator, which is under development for protontherapy applications at ENEA C.R. Frascati, Italy. Visible fluorescence microscopy was successfully used to read the latent proton beam images stored in the lithium fluoride crystals, thanks to high emission efficiency of the F2 and F3+ color centers obtained by simultaneous optical excitation in the blue spectral range. High intrinsic spatial resolution and wide dynamic range of these novel LiF detectors allow obtaining two-dimensional images of both the beam transverse intensity distribution and of the Bragg curve. By using a simple defect formation model that takes into account the energy released in the material and the saturation of defect concentration, not only the two-dimensional dose map was obtained from the beam transverse intensity distribution image, but also the full Bragg curve was reconstructed, allowing the thorough characterization of proton beams produced by the accelerator.

An analytical model that approximates Bragg curves due to protons in water is extended to lithium fluoride (LiF), both in bulk and lower-density homogeneous thin film form. To that purpose, Monte Carlo simulations of proton range for energies from 5 to 65 MeV are best fitted so that optimal values of the model parameters are deduced for LiF. Tests are performed by comparing analytically computed Bragg curves with corresponding ones simulated by Monte Carlo software in LiF, bulk and lower density, at two example proton energies and energy-straggling widths. The model is then applied to the reconstruction of the energy spectra of proton beams by best fitting experimental Bragg profiles due to visible photoluminescence of optically-active F2 and F 3 + color centers created in LiF crystals by the ionizing interaction of protons with the material.

Lithium fluoride (LiF) crystals were irradiated with a proton beam. With nominal beam energies of 3 and 7 MeV, several irradiations were performed which delivered doses ranging from 103 to 107 Gy. The ionisation produced by the protons in the LiF samples induced the stable formation in the crystalline lattice of colour centres, two types of which, the F2 and F 3 + ones, possess broad photoluminescence bands in the red and green, respectively, when optically pumped in the blue at wavelengths close to 450 nm. At both proton energies, measurements of the distinct F2 and F 3 + contributions to the emission spectra showed a decrease of the F 3 + integrated photoluminescence intensity at large doses, say from ∼106−107 Gy on. We try to explain such a behaviour by assuming the formation of absorption and/or quenching centres, and compare the predictions of an ad hoc developed model with experimental data.

In recent years, lithium fluoride (LiF) detectors based on the optical reading of photoluminescence emitted by radiation-induced F2 and F3+ colour centres have been successfully used for advanced diagnostics of proton beams. In this work, the visible photoluminescence response of LiF film-based radiation detectors of three different thicknesses, grown by thermal evaporation on glass and Si(100) substrates and irradiated with 27 MeV proton beams at doses in the range between 4.2 × 103 and 1.7 × 105 Gy, was carefully investigated by fluorescence optical microscopy. Before irradiation, the structural and morphological properties of LiF films were investigated by atomic force microscopy and X-ray diffraction techniques. Substrate-enhanced photoluminescence response up to 48% was observed in LiF film-based detectors grown on Si(100) substrates with respect to those deposited on glass in the same deposition run and irradiated in the same conditions. This photoluminescence enhancement can be mainly ascribed to the reflective properties of the Si substrate in the visible spectral range, where the emission bands of F2 and F3+ colour centres are located, combined with the proper choice of the film thickness. Other complex effects related to the polycrystalline nature of the LiF films cannot be excluded.

This contribution describes the methods developed for the characterization in air of the proton beam at the TOP-IMPLART linear accelerator of ENEA Frascati Research Centre. Beam energy and spectrum, transverse homogeneity, fluence and flux are assessed both experimentally and by numerical calculations. Here we present an application of these methods for the characterization of set-ups relevant for electronic and space components testing.

To demonstrate the large potential of proton minibeam radiotherapy (pMBRT) as a new method to treat tumor diseases, a preclinical proton minibeam radiation facility was designed. It is based on a tandem Van-de-Graaff accelerator providing a 16 MeV proton beam and a 3 GHz linac post-accelerator (designs: AVO-ADAM S.A, Geneva, Switzerland and ENEA, Frascati, Italy). To enhance the transmission of the tandem beam through the post-accelerator by a factor of 3, two drift tube buncher units were designed and constructed: A brazed 5-gap structure (adapted SCDTL tank of the TOP-IMPLART project (ENEA)) and a non-brazed low budget 4-gap structure. Both are made of copper. The performance of the two differently manufactured units was evaluated using a 16 MeV tandem accelerator beam and a Q3D magnetic spectrograph. Both buncher units achieve the required summed voltage amplitude of 42 kV and amplitude stability at a power feed of less than 800 W.

We present the first results of a novel collaboration activity between ENEA Frascati Particle Accelerator Laboratory and University La Sapienza Guidance and Navigation Laboratory in the field of Radiation Hardness Assurance (RHA) for space applications. The aim of this research is twofold: (a) demonstrating the possibility to use the TOP-IMPLART proton accelerator for radiation hardness assurance testing, developing ad hoc dosimetric and operational procedures for RHA irradiations; (b) investigating system level radiation testing strategies for Commercial Off The Shelf (COTS) components of interest for SmallSats space missions, with focus on devices and sensors of interest for guidance, navigation and control, through simultaneous exploration of Total Ionizing Dose (TID), Displacement Damage (DD) dose and Single-Event Effects (SEE) with proton beams. A commercial 6-axis integrated Micro Electro-Mechanical Systems (MEMS) inertial navigation system (accelerometer, gyroscope) was selected as first Device Under Test (DUT). The results of experimental tests aimed to define an operational procedure and the characterization of radiation effects on the component are reported, highlighting the consequence of the device performance degradation in terms of the overall navigation system accuracy. Doses up to 50 krad(Si) were probed and cross sections for Single-Event Functional Interrupt (SEFI) evaluated at a proton energy of 30 MeV.

This paper presents the experimental results on the Terapia Oncologica con Protoni-Intensity Modulated Proton Linear Accelerator (TOP-IMPLART) beam that is currently accelerated up to 35 MeV, with a final target of 150 MeV. The TOP-IMPLART project, funded by the Innovation Department of Regione Lazio (Italy), is led by Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA) in collaboration with the Italian Institute of Health and the Oncological Hospital Regina Elena-IFO. The accelerator, under construction and test at ENEA-Frascati laboratories, employs a commercial 425 MHz, 7 MeV injector followed by a sequence of 3 GHz accelerating modules consisting of side coupled drift tube linac (SCDTL) structures up to 71 MeV and coupled cavity linac structures for higher energies. The section from 7 to 35 MeV, consisting on four SCDTL modules, is powered by a single 10 MW klystron and has been successfully commissioned. This result demonstrates the feasibility of a ``fully linear'' proton therapy accelerator operating at a high frequency and paves the way to a new class of machines in the field of cancer treatment.

The Intensity Modulated Proton Linear Accelerator for Cancer Therapy (TOP-IMPLART) is under development and construction by ENEA in collaboration with the Italian Institute of Health (ISS) and the Oncological Hospital Regina Elena-IFO with financial support of Regione Lazio. Its peculiar time structure (few microseconds pulse width) and very high peak intensity (≍ 109 proton/pulse) demand for ad hoc dose delivery monitors (DDM). The TOP-IMPLART DDM is based on ionization gas chambers. One segmented chamber prototype uses Micro Pattern Gaseous Detector technology for the 2-dimensional simultaneous x/y readout; the charge collected from each active segment (strips with pad-like shape) is readout by a dedicated gain-adaptable electronics. Two small, highly sensitive, integral ionization chambers, using the same electronics, complement the 2D chamber for the monitor of the single pulse beam charge, down to 1 pC/pulse. While under development and deployment of its accelerating modular cavities, the linear TOP-IMPLART beam is improved thanks also to the continuous monitoring and characterization by these devices, whose responses are periodically compared to calibrated dosimetric detectors such as real-time active microDiamond sensor, passive Alanine pellets, intrinsically stable integral Faraday Cup. Different calibration campaigns have been recently conducted to measure the recombination and dose-rate effects on the above ionization chambers. The outcome of these measurements shows clear electron-ion recombination in the chamber active volume, largely related to the high beam intensity and its small transverse cross section. Those effects can be taken into account and used to correct the actual measurement of the DDM. In this paper, the TOP-IMPLART project and the DDM devices are shortly presented and details of the above experimental studies are discussed.

Passive solid-state radiation detectors, based on the radiophotoluminescence of stable color centers in nominally pure lithium fluoride (LiF) crystals, have been used for advanced diagnostics of the segment up to 35 MeV of the TOP-IMPLART proton linear accelerator for protontherapy applications, under development at ENEA Frascati. In LiF, proton beams generate a spatial distribution of F2 and F3+ aggregate color centers, which efficiently emit radiophotoluminescence in the red-green spectral range under optical pumping around 450 nm. LiF crystals were irradiated with 35 MeV nominal energy protons at several doses of interest for protontherapy (from 0.5 to 50 Gy). For the first time is shown here the possibility of measuring the radiophotoluminescence spectra of proton irradiated LiF even at such low doses and how the signal showed a linear behavior with dose with a good signal-to-noise ratio. A Bragg-curve image, stored as color-center distribution in a LiF crystal after a 50 Gy-dose irradiation in a particular geometry, was acquired in a conventional fluorescence microscope. After appropriate image processing, the signal intensity resulted to be proportional to the linear energy transfer along the whole Bragg curve. By best-fitting it with an ad-hoc analytical formula, the depth-dose distribution was reconstructed and the proton beam energy and energy spread were estimated.

Intensity Modulated Proton Therapy (IMPT) can take great advantage of fast tools based on analytical or semianalytical approaches providing dose evaluation in a target. Here, a semianalytical method is described that has been developed for the TOP-IMPLART (Intensity Modulated Proton Linear Accelerator for RadioTherapy) accelerator, consisting of a pulsed full linear accelerator for proton therapy being developed at ENEA Frascati, where preliminary tests of active beam energy and intensity modulation are undergoing. The method relies on a two-step procedure that provides the main accelerator parameters and optimizes the number and the weights of the energetic components needed to obtain a uniform Spread-Out Bragg Peak (SOBP) in the target region. In the present paper, the theoretical basis of the method is described in detail together with two practical example applications.

In the last few years, the peculiar photoluminescence properties of radiation-induced color centers in lithium fluoride (LiF) films have been successfully used for advanced diagnostics of low-energy proton beams produced by the TOP-IMPLART linear accelerator for protontheraphy under development at ENEA C.R. Frascati. The two-dimensional spatial dose map of the transversal section of proton beams was fully reconstructed in a wide interval of doses. In this work the optical emission properties of LiF thin films, grown by thermal evaporation on glass and Si(100) substrates and subsequently irradiated by proton beams of nominal energy 3 MeV at doses higher than 105 Gy, were carefully investigated. Their structural and morphological analyses were performed by X-ray diffraction and atomic force microscopy. A careful comparison of the photoluminescence and photoluminescence-excitation spectra of F2 and F3+ electronic defects was performed. Substrate-enhanced photoluminescence intensity increase up to 100% was observed in colored LiF films grown on Si substrates with respect to glass ones. This behavior can be substantially ascribed to the reflective properties of the Si substrate at the emission wavelengths of F2 and F3+ CCs, although other complex effects due to the polycrystalline nature of the films cannot be excluded.

In a recent paper, an analytical expression for proton Bragg curves was introduced and utilized to best fit photoluminescent depth distributions of optically active F 2 and F 3 + color centers in lithium fluoride, with the purpose of evaluating the energy spectrum of a proton beam, assumed to consist of the superposition of Gaussian components. Here, an original alternative method is introduced by means of which the same energy spectrum analysis can be performed by iteratively applying a suitable mathematical operator to the photoluminescent depth distribution, no best fitting operation being needed.

In the framework of the Italian TOP-IMPLART project (Regione Lazio), ENEA-Frascati, ISS and IFO are developing and constructing the first proton linear accelerator based on an actively scanned beam for tumor radiotherapy with final energy of 150 MeV. An important feature of this accelerator is modularity: an exploitable beam can be delivered at any stage of its construction, which allows for immediate characterization and virtually continuous improvement of its performance. Currently, a sequence of 3 GHz accelerating modules combined with a commercial injector operating at 425 MHz delivers protons up to 35 MeV. Several dosimetry systems were used to obtain preliminary characteristics of the 35-MeV beam in terms of stability and homogeneity. Short-term stability and homogeneity better than 3% and 2.6%, respectively, were demonstrated; for stability an improvement with respect to the respective value obtained for the previous 27 MeV beam.

Purpose: To study EBT3 GafChromic film in low-energy protons, and for comparison purposes, in a reference 60Co beam in order to use it as a calibrated dosimetry system in the proton irradiation facility under construction within the framework of the Oncological Therapy with Protons (TOP)-Intensity Modulated Proton Linear Accelerator for RadioTherapy (IMPLART) Project at ENEA-Frascati, Italy. Methods: EBT3 film samples were irradiated at the Istituto Nazionale di Fisica Nucleare—Laboratori Nazionali di Legnaro, Italy, with a 5 MeV proton beam generated by a 7 MV Van de Graaff CN accelerator. The nominal dose rates used were 2.1 Gy/min and 40 Gy/min. The delivered dose was determined by measuring the particle fluence and the energy spectrum in air with silicon surface barrier detector monitors. A preliminary study of the EBT3 film beam quality dependence in low-energy protons was conducted by passively degrading the beam energy. EBT3 films were also irradiated at ENEA-National Institute of Ionizing Radiation Metrology with gamma radiation produced by a 60Co source characterized by an absorbed dose to water rate of 0.26 Gy/min as measured by a calibrated Farmer type ionization chamber. EBT3 film calibration curves were determined by means of a set of 40 film pieces irradiated to various doses ranging from 0.5 Gy to 30 Gy absorbed dose to water. An EPSON Expression 11000XL color scanner in transmission mode was used for film analysis. Scanner response stability, intrafilm uniformity, and interfilm reproducibility were verified. Optical absorption spectra measurements were performed on unirradiated and irradiated EBT3 films to choose the most sensitive color channel to the dose range used. Results: EBT3 GafChromic films show an under response up to about 33% for low-energy protons with respect to 60Co gamma radiation, which is consistent with the linear energy transfer dependence already observed with higher energy protons, and a negligible dose-rate dependence in the 2–40 Gy/min range. Short- and long-term scanner stabilities were 0.5% and 1.5%, respectively; film uniformity and reproducibility were better than 0.5%. Conclusions: The main purpose of this study was to implement EBT3 dosimetry in the proton low-energy radiobiology line of the TOP-IMPLART accelerator, having a maximum energy of 7 MeV. Low-energy proton and 60Co calibrated sources were used to investigate the behavior of film response vs to be written in italicum dose. The calibration in 5 MeV protons is currently used for dose assessment in the radiobiological experiments at the TOP-IMPLART accelerator carried out at that energy value.

The first proton linear accelerator for tumor therapy based on an actively scanned beam up to the energy of 150 MeV, is under development and construction by ENEA-Frascati, ISS and IFO, under the Italian TOP-IMPLART project. Protons up to the energy of 7 MeV are generated by a customized commercial injector operating at 425 MHz; currently three accelerating modules allow proton delivery with energy up to 27 MeV. Beam homogeneity and reproducibility were studied using a 2D ionizing chamber, EBT3 films, a silicon diode, MOSFETs, LiF crystals and alanine dosimetry systems. Measurements were taken in air with the detectors at ~1 m from the beam line exit window. The maximum energy impinging on the detectors surface was 24.1 MeV, an energy suitable for radiobiological studies. Results showed beam reproducibility within 5% and homogeneity within 4%, on a circular surface of 16mm in diameter. © The Author(s) 2018.

In the last few years, the visible photoluminescence (PL) of radiation-induced laser-active F2 and F3+ aggregate color centers (CCs) in lithium fluoride, LiF, has been successfully used for advanced diagnostics of low-energy proton beams. A systematic study of the optical properties of LiF crystals and thin films exposed in different irradiation geometries to a proton beam of nominal energy 7 MeV is under way. The ionization induces the stable formation of primary and aggregate CCs in the crystalline lattice, among which the F2 and F3+ defects possess broad emission bands in the red and green spectral ranges, respectively, when optically pumped at wavelengths close to 450 nm. Their PL intensity has been found to be linearly proportional to the dose absorbed by the host material over at least three orders of magnitude, so that LiF solid-state dosimeters based on spectrally-integrated PL reading can be envisaged. A simple defect formation model that takes into account the energy released in the material, crystals and films, together with the saturation of CC concentration at high doses, allows obtaining both the full Bragg curve reconstruction with its dose distribution with depth and the accumulated bi-dimensional transversal dose-mapping from the visible fluorescence images latently stored in LiF crystals and thin films, respectively. Results obtained by using a fluorescence microscope are presented and discussed with the aim of highlighting some quantitative aspects of the PL behavior of CCs both in LiF crystals and films, which are relevant for low-energy proton-beam Bragg curve imaging and dose mapping in a wide interval of doses up to the ones at which strong CC saturation occurs.

Solid-state radiation detectors based on the photoluminescence of stable point defects in lithium fluoride crystals have been used for advanced diagnostics during the commissioning of the segment up to 27 MeV of the TOP-IMPLART proton linear accelerator for proton therapy applications, under development at ENEA C.R. Frascati, Italy. The LiF detectors high intrinsic spatial resolution and wide dynamic range allow obtaining two-dimensional images of the beam transverse intensity distribution and also identifying the Bragg peak position with micrometric precision by using a conventional optical fluorescence microscope. Results of the proton beam characterization, among which, the estimation of beam energy components and dynamics, are reported and discussed for different operating conditions of the accelerator. © 2017 Elsevier B.V.

A sensitivity study is presented here on a compact hybrid postacceleration scheme coupling laser-generated protons to a high frequency Linac based on the use of a SCDTL (Side Coupled Drift Tube Linac) structure. The study analyzes the main laser-generated beam characteristics and the most important parameters linked to the accelerating structure. We show that the required tolerances regarding alignment and field uniformity, although challenging, are within the reach of actual technology. Regarding the laser-generated proton beam parameters (spot size and divergence), we show that they have only a little influence on the final emittance that is mainly determined by the capturing and accelerating structure. However, these parameters can sensitively affect the final transmission of the proton beam current.

ENEA and ISS (Italian National Institute of Health), are collaborating to develop a dedicated proton medical accelerator, TOP (Oncological Therapy with Protons) linac, consisting of a sequence of three pulsed linear accelerators. The 7 MeV injector can be used in three operating modes: Protontherapy and Radiobiology Mode—injecting low current proton beam into the TOP linac accelerating sections; Radioisotope Mode—generating an intense proton beam (8–10 mA, 50–100 μs, 30–100 Hz) to produce the positron-emitting radionuclide F18 for PET analyses. In the high current mode, at the exit of the injector the beam is guided through a magnetic quadrupoles channel to a target composed by a thin chamber (0.5 mm thick and 1 in. diameter) containing water enriched with O18. Production yield as well as total activity similar to these achieved with higher energy cyclotrons have been obtained. Environmental doses measured give indications on the shielding required for operation under current radioprotection regulations. Improvements are foreseen to optimize the production yield, the useful beam current and to better characterize gamma and neutron dose rates in the different operational modes.

LiF films grown on glass and Si(100) substrates by thermal evaporation were used as radiation imaging detectors to evaluate the Bragg peak position of a 3 MeV proton beam produced by a linear accelerator. The proton irradiation of LiF films induces the formation of stable color centers, mainly the primary F centers and the aggregate F2 and F3 + defects, whose local concentrations are proportional to the deposited energy. Under optical pumping in the blue spectral region, F2 and F3 + color centers emit broad photoluminescence bands located at 678 and 541 nm, respectively, which can be detected by conventional fluorescence microscopy. Photoluminescence images of the top surface of the exposed LiF films allowed obtaining the Bragg peak position of the proton beam, whose evaluation is in satisfactory agreement with software simulations.

We report the first experiment aimed at the demonstration of low-energy protons acceleration by a high-efficiency S-band RF linear accelerator. The proton beam has been accelerated from 7 to 11.6 MeV by a 1 meter long SCDTL (Side Coupled Drift Tube Linac) module powered with 1.3 MW. The experiment has been done in the framework of the Italian TOP-IMPLART (Oncological Therapy with Protons-Intensity Modulated Proton Therapy Linear Accelerator for Radio-Therapy) project devoted to the realization of a proton therapy centre based on a proton linear accelerator for intensity modulated cancer treatments to be installed at IRE-IFO, the largest oncological hospital in Rome. It is the first proton therapy facility employing a full linear accelerator scheme based on high-frequency technology. © CopyrightEPLA, 2015.

A lithium fluoride crystal slab was irradiated in air with a proton beam of nominal 7 MeV energy at a linear accelerator that is under development at ENEA C.R. Frascati. The irradiation generated a spatial distribution of stable colour centres in the crystal that could be detected as a luminescent image under blue-light excitation in a fluorescence microscope. The reconstruction of the whole Bragg curve from the luminescent image is here demonstrated for the first time by taking into account finite proton-energy bandwidth and saturation of defect concentration due to high absorbed dose. The obtained results confirm lithium fluoride detectors based on visible photoluminescence of radiation-induced aggregate colour centres as reliable candidate devices for advanced proton-beam diagnostics. © CopyrightEPLA, 2018.

The Side Coupled Drift Tube Linac (SCDTL) is an attractive 3 GHz accelerating structure composed of short DTL tanks coupled together by side coupling cavities, in the course of development of the 200 MeV proton linear accelerator for proton therapy planned for the Terapia Oncologica con Protoni (TOP) program of the Italian National Institute of Health (Istituto Superiore di Sanita, ISS). The TOP Linac will be used to boost to 70 MeV the 7 MeV proton beam from a linac injector. Our main concern is to investigate in detail the characteristics of the structure in terms of RF properties of the accelerating mode, like longitudinal and transverse shunt impedance and quality factor, and of the other modes that cause the origin of the tank dispersion curve, in order to stabilize the behaviour under operating conditions. Calculations performed with the computer three-dimensional (3D) codes MAFIA and SOPRANO on the smallest unit of the system (a single DTL tank without coupling cavities) and experimental measurements made on a prototype have shown good agreement. Two possible supporting stem configurations (single stem and two stems 180° apart for each drift tube) were examined and a comparison of the results in both cases are discussed.

Proton beams of energy 3 and 7 MeV, produced by a linear accelerator for protontherapy under development at ENEA Frascati, were used to irradiate lithium fluoride (LiF) crystals and 1 μm thick LiF films grown by thermal evaporation on glass substrates, in a fluence range from 10 11 to 10 15 protons/cm 2 . The irradiation of LiF induced the stable formation of aggregate visible-emitting F 2 and F 3 + color centers, which possess almost overlapping absorption bands around 450 nm and, under optical pumping in this spectral region, they simultaneously emit broad photoluminescence bands, peaked at 678 nm and 541 nm, respectively. Their laser excited emission spectra were acquired and the integrated photoluminescence signal was measured using a fluorescence optical microscope equipped with a cooled s-CMOS camera. The photoluminescence of proton irradiated LiF crystals and films shows an interesting linear response as a function of the irradiation fluence. By optical fluorescence microscopy, it was possible to record the transversal proton beam intensity profile by acquiring the photoluminescence image of irradiated LiF. Moreover, using cleaved LiF films grown on silicon substrates irradiated in a particular geometry allowed one to measure the colour centres photoluminescence distribution with proton penetration depth and provided a direct imaging of the Bragg peak.

Proton beams of 3 MeV energy, produced by the injector of a linear accelerator for proton therapy, were used to irradiate at room temperature lithium fluoride crystals and polycrystalline thin films grown by thermal evaporation. The irradiation fluence range was 1011-1015 protons/cm2. The proton irradiation induced the stable formation of primary and aggregate color centers. Their formation was investigated by optical absorption and photoluminescence spectroscopy. The F2 and F3 + photoluminescence intensities, carefully measured in LiF crystals and thin films, show linear behaviours up to different maximum values of the irradiation fluence, after which a quenching is observed, depending on the nature of the samples (crystals and films). The Principal Component Analysis, applied to the absorption spectra of colored crystals, allowed to clearly identify the formation of more complex aggregate defects in samples irradiated at highest fluences. © Published under licence by IOP Publishing Ltd.

Optically transparent LiF thin films thermally evaporated on glass and Si(100) substrates were used for advanced diagnostics of proton beams of energies from 1.4 to 7 MeV produced by a linear accelerator for protontheraphy under development at ENEA C.R. Frascati. The proton irradiation induces the formation of stable colour centres, among them the aggregate F2 and F3 + optically active defects. After exposure of LiF films grown on glass perpendicularly to the proton beams, their accumulated transversal spatial distributions were carefully measured by reading the latent two-dimensional (2-D) fluorescence images stored in the LiF thin layers by local formation of these broad-band visible light-emitting defects with an optical microscope under blue lamp excitation. Taking advantage from the low thickness of LiF thin films and from the linear behaviour of the integrated F2 and F3 + photoluminescence intensities up to the irradiation fluence of ∼5x1015 p/cm2, placing a cleaved LiF film grown on Si substrate with the cutted edge perpendicular to the proton beam, the 2-D fluorescence image of the film surface could allow to obtain the depth profile of the energy released by protons, which mainly lose their energy at the end of the path. © Published under licence by IOP Publishing Ltd.

Protons generated by irradiating a thin metal foil with a high-intensitylaser have shown to posses interesting characteristics in terms of energy, emittance, current, and pulse duration. Therefore, in the near future, they might become a competitive source with respect to conventional proton sources. Previous theoretical, numerical, and experimental studies have already demonstrated efficient coupling between laser-accelerated proton beams with traditional radio frequency (RF)-based particle accelerators. These hybrid proton accelerators benefit from both the excellent properties of the laser-based source and the flexibility, reliability, and know-how of beam handling as provided by RF-based accelerator structures. In this paper, state of the art experimental results of laser-accelerated proton beams are used as input for a numerical study using compact and innovative conventional accelerator structures designed for medical applications. Results show that this compact hybrid accelerator allows even more efficient capture and acceleration of the laser-generated proton beam.

Systematic irradiation of thermally evaporated 0.8 μm thick polycrystalline lithium fluoride films on glass was performed by proton beams of 3 and 7 MeV energies, produced by a linear accelerator, in a fluence range from 1011to1015protonscm2. The visible photoluminescence spectra of radiation-induced F2 and F3+laser active color centers, which possess almost overlapping absorption bands at about 450 nm, were measured under laser pumping at 458 nm. On the basis of simulations of the linear energy transfer with proton penetration depth in LiF, it was possible to obtain the behavior of the measured integrated photoluminescence intensity of proton irradiated LiF films as a function of the deposited dose. The photoluminescence signal is linearly dependent on the deposited dose in the interval from 103 to about 106Gy, independently from the used proton energies. This behavior is very encouraging for the development of advanced solid state radiation detectors based on optically transparent LiF thin films for proton beam diagnostics and two-dimensional dose mapping. © 2015 AIP Publishing LLC.

ENEA, in collaboration with ISS (Italian National Institute of Health), is developing a dedicated proton medical accelerator. The TOP (Oncological Therapy with Protons) linac is to be installed at the IFO Oncological Hospital in Rome. It will be a sequence of three pulsed (5 psec, 300 Hz) linear accelerators: a 7 MeV, 425 MHz RFQ+DTL (AccSys Model PL-7), a 7-65 MeV, 2998 MHz Side Coupled Drift Tube Linac (SCDTL) and a 65-200 MeV, variable energy 2998 MHz Side Coupled Linac (SCL). The 7 MeV injector output will also be used in high current mode for F-18 radioisotope production. The SCDTL output will be used for proton treatment of ocular melanoma and for radiobiology studies, with the SCL output dedicated to proton treatment of deep seated tumours. The 7 MeV injector has been completed by AccSys and shipped to ENEA in Frascati and the first SCDTL module (to boost the beam from 7 to 13.4 MeV) has been constructed. The low energy (7 MeV) beam lines for F-18 production and injection in the SCDTL are under construction. The characteristics of the various accelerator components and the status of the project are presented.