In order to fully exploit the ballistic potential of particle therapy, we propose an online range monitoring concept based on time-of-flight (TOF)-resolved prompt gamma (PG) detection in a single ...proton counting regime. In a proof of principle experiment, different types of monolithic scintillating gamma detectors are read in time coincidence with a diamond-based beam hodoscope, in order to build TOF spectra of PG generated in a target presenting an air cavity of variable thickness. Since the measurement was carried out at low beam currents (< 1 proton/bunch) it was possible to reach excellent coincidence time resolutions, of the order of 100 ps (σ). Our goal is to detect possible deviations of the proton range with respect to treatment planning within a few intense irradiation spots at the beginning of the session and then carry on the treatment at standard beam currents. The measurements were limited to 10 mm proton range shift. A Monte Carlo simulation study reproducing the experiment has shown that a 3 mm shift can be detected at 2σ by a single detector of ∼1.4 × 10
absolute detection efficiency within a single irradiation spot (∼10
protons) and an optimised experimental set-up.
The intrinsic electronic properties of diamond make it suitable for radiation-hard and very fast detector development with good signal to noise ratios. With the advent of new generations of ion ...accelerators either for physics (nuclear and high energy physics) or medical applications (hadrontherapy and synchrotron radiation radiotherapy) there is a need for a very accurate beam monitoring in high radiation environments. Diamond is particularly suited to these applications. Fast pulse detection mode for time stamp, and current integration mode for operation as beam monitors at high particle rates are targeted. Commercial single-crystal, polycrystalline and heteroepitaxial diamonds produced by Chemical Vapor Deposited (CVD) method are analyzed and compared by means of X-ray Beam Induced Current (XBIC). Their performance as particle detectors is investigated using a 8.5 keV X-ray photon micro-bunch beam at ESRF (European Synchrotron Radiation Facility). This facility provides a focused (~1 μm) pulsed beam (100 ps bunch duration), producing an almost uniform energy deposit along the beam irradiated volume in the detector, therefore closely mimicking the interaction of single charged particles. The XBIC set-up of the ID21 beamline enabled us to draw 2D response maps of detectors with disk- and strip metal contact patterns. Using the pulse-synchronized XBIC measurements, a time resolution of 150 ps RMS and bunch detection efficiency of ~100% were evaluated at the contact strip crossing points of a first prototype polycrystalline beam monitor.
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•Diamond double stripped beam monitor prototypes for hadrontherapy monitoring.•Chemical Vapor Deposited diamond detector performance evaluated under X-rays.•2D current maps evaluated on diamond metallized surface using X-rays micro beams.•Time resolution and bunch detection efficiency at contact strip crossing points.
The MoniDiam project is part of the French national collaboration CLaRyS (Contrôle en Ligne de l’hAdronthérapie par RaYonnements Secondaires) for on-line monitoring of hadron therapy. It relies on ...the imaging of nuclear reaction products that is related to the ion range. The goal here is to provide large area beam detectors with a high detection efficiency for carbon or proton beams giving time and position measurement at 100 MHz count rates (beam tagging hodoscope). High radiation hardness and intrinsic electronic properties make diamonds reliable and very fast detectors with a good signal to noise ratio. Commercial Chemical Vapor Deposited (CVD) poly-crystalline, heteroepitaxial and monocrystalline diamonds were studied. Their applicability as a particle detector was investigated using α and β radioactive sources, 95 MeV/u carbon ion beams at GANIL and 8.5 keV X-ray photon bunches from ESRF. This facility offers the unique capability of providing a focused (~1 μm) beam in bunches of 100 ps duration, with an almost uniform energy deposition in the irradiated detector volume, therefore mimicking the interaction of single ions. A signal rise time resolution ranging from 20 to 90 ps rms and an energy resolution of 7 to 9% were measured using diamonds with aluminum disk shaped surface metallization. This enabled us to conclude that polycrystalline CVD diamond detectors are good candidates for our beam tagging hodoscope development. Recently, double-side stripped metallized diamonds were tested using the XBIC (X Rays Beam Induced Current) set-up of the ID21 beamline at ESRF which permits us to evaluate the capability of diamond to be used as position sensitive detector. The final detector will consist in a mosaic arrangement of double-side stripped diamond sensors read out by a dedicated fast-integrated electronics of several hundreds of channels.
Experimental fission studies for reaction physics or nuclear spectroscopy can profit from fast, efficient, and radiation-resistant fission fragment (FF) detectors. When such experiments are performed ...in-beam in intense thermal neutron beams, additional constraints arise in terms of target-detector interface, beam-induced background, etc. Therefore, wide gap semi-conductor detectors were tested with the aim of developing innovative instrumentation for such applications. The detector characterization was performed with mass- and energy-separated fission fragment beams at the ILL (Institut Laue Langevin) LOHENGRIN spectrometer. Two single crystal diamonds, three polycrystalline and one diamond-on-iridium as well as a silicon carbide detector were characterized as solid state ionization chamber for FF detection. Timing measurements were performed with a 500-µm thick single crystal diamond detector read out by a broadband amplifier. A timing resolution of ∼10.2 ps RMS was obtained for FF with mass A = 98 at 90 MeV kinetic energy. Using a spectroscopic preamplifier developed at INFN-Milano, the energy resolution measured for the same FF was found to be slightly better for a ∼50-µm thin single crystal diamond detector (∼1.4% RMS) than for the 500-µm thick one (∼1.6% RMS), while a value of 3.4% RMS was obtained with the 400-µm silicon carbide detector. The Pulse Height Defect (PHD), which is significant in silicon detectors, was also investigated with the two single crystal diamond detectors. The comparison with results from α and triton measurements enabled us to conclude that PHD leads to ∼50% loss of the initial generated charge carriers for FF. In view of these results, a possible detector configuration and integration for in-beam experiments has been discussed.
In the context of online ion range verification in particle therapy, the CLaRyS collaboration is developing Prompt-Gamma (PG) detection systems. The originality in the CLaRyS approach is to use a ...beam-tagging hodoscope in coincidence with the gamma detectors to provide both temporal and spatial information of the incoming ions. The ion range sensitivity of such PG detection systems could be improved by detecting single ions with a 100ps (σ) time resolution, through a quality assurance procedure at low beam intensity at the beginning of the treatment session. This work presents the investigations that led to assessment of the Chemical Vapor Deposition (CVD) diamond detectors performance to fulfill these requirements. A 90Sr beta source, 68MeV protons, 95 MeV/u carbon ions and a synchrotron X-ray pulsed beam were used to measure the time resolution, single ion detection efficiency and proton counting capability of various CVD diamond samples. An offline technique, based on double-sided readout with fast current preamplifiers used to improve the signal-to-noise ratio, is also presented. The different tests highlighted Time-Of-Flight resolutions ranging from 13ps (σ) to 250ps (σ), depending on the diamond crystal quality and the particle type and energy. The single 68MeV proton detection efficiency of various large area polycrystalline (pCVD) samples was measured to be >96% using coincidence measurements with a single-crystal reference detector. Single-crystal CVD (sCVD) diamond proved to be able to count a discrete number of simultaneous protons while it was not achievable with a polycrystalline sample. Considering the results of the present study, two diamond hodoscope demonstrators are under development: one based on sCVD, and one of larger size based on pCVD. They will be used for the purpose of single ion as well as ion bunches detection, either at reduced or clinical beam intensities.
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