The foot (Fragmentation Of Target) experiment

Particle therapy uses proton or 12C beams for the treatment of deep-seated solid tumors. Due to the features of energy deposition of charged particles a small amount of dose is released to the healthy tissue in the beam entrance region, while the maximum of the dose is released to the tumor at the end of the beam range, in the Bragg peak region. However nuclear interactions between beam and patient tissues induce fragmentation both of projectile and target and must be carefully taken into account. In 12C treatments the main concern are long range fragments due to projectile fragmentation that release dose in the healthy tissue after the tumor, while in proton treatment the target fragmentation produces low energy, short range fragments along all the beam range. The FOOT experiment (FragmentatiOn Of Target) is designed to study these processes. Target nuclei (16O,12C) fragmentation induced by 150-250 AMeV proton beam will be studied via inverse kinematic approach. 16O,12C therapeutic beams, with the quoted kinetic energy, collide on graphite and hydrocarbons target to provide the cross section on Hydrogen. This configuration explores also the projectile fragmentation of these 16O,12C beams. The detector includes a magnetic spectrometer based on silicon pixel detectors and drift chamber, a scintillating crystal calorimeter with TOF capabilities, able to stop the heavier fragments produced, and a \u394E detector to achieve the needed energy resolution and particle identification. An alternative setup of the experiment will exploit the emulsion chamber capabilities. A specific emulsion chambers will be coupled with the interaction region of the FOOT setup to measure the production in target fragmentation of light charged fragments as protons, deuterons, tritons and Helium nuclei. The FOOT data taking is foreseen at the CNAO experimental room and will start during early 2018 with the emulsion setup, while the complete electronic detector will take data since 2019

An FPGA based DAQ System for the Readout of SiPM Matrices in PET Applications

The DASiPM2 project is funded by INFN and is aimed at the development of a demonstrator of a PET system based on SiPM photo-detectors. In this framework an FPGA based DAQ system has been designed and developed at INFN-Pisa to read and characterize 4x4 SiPM matrices. The system architecture, the first test and characterization results and the planned future development activities are here described. \ua92008 IEEE

Studies of silicon photomultipliers at cryogenic temperatures

We investigate the behavior of silicon photomultipliers (SiPMs) at low temperatures: I–V characteristics, breakdown voltage, dark noise, afterpulsing, crosstalk, pulse shape, gain and photon detection efficiency are studied as a function of temperature in the range 50 K<T<320 K. We discuss our measurements on the basis of the temperature dependent properties of silicon and of the models related to carrier generation, transport and multiplication in high electric field. We conclude that SiPMs provide an excellent alternative to vacuum tube photomultipliers (PMTs) in low temperature environments, even better than in room temperature ones: in particular they excel in the interval 100 K<T<200 K

Experimental study of beam hardening artifacts in photon counting breast computed tomography

We are implementing an X-ray breast Computed Tomography (CT) system on the gantry of a dedicated single photon emission tomography system for breast Tc-99 imaging. For the breast CT system we investigated the relevance of the beam hardening artifact. We studied the use of a single photon counting silicon pixel detector (0.3 mm thick, 256 7256 pixel, 55&#956;m pitch, bump-bonded to the Medipix2 photon counting readout chip) as detector unit in our X-ray CT system. We evaluated the beam hardening \u201ccupping\u201d artifact using homogeneous PMMA slabs and phantoms up to 14 cm in diameter, used as uncompressed breast tissue phantoms, imaged with a tungsten anode tube at 80 kVp with 4.2 mm Al filtration. For beam hardening evaluation we used a bimodal energy model. The CT data show a \u201ccupping\u201d artifact going from 4% (4-cm thick material) to 18% (14-cm thick material). This huge artifacts is influenced by the low detection efficiency and the charge sharing effect of the silicon pixel detector

Digital mammographic application of a single photon counting pixel detector

We present the imaging capabilities of a system based on a single photon counting chip, bump-bounded to a Si pixel detector. The detector is 300 mum thick a matrix of 64 x 64 square pixels with a dimension side of 170 mum. The active area is about 1.2 cm(2). The photon counting chip matches the geometry of the detector so it has 4096 asynchronous read-out cells, each containing a charge preamplifier, a leading edge comparator and a pseudo-random counter. We have tested the image quality and the stability of our acquisition system imaging some phantoms used for mammografic quality checks. Our system allows to see low contrast details with a patient dose comparable with that given in mammographic examinations