50 research outputs found

    Next-generation ultra-compact calorimeters based on oriented crystals

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    Calorimeters based on oriented crystals provide unparalleled compactness and resolution in measuring the energy of electromagnetic particles. Recent experiments performed at CERN and DESY beamlines by the AXIAL/ELIOT experiments demonstrated a significant reduction in the radiation length inside tungsten and PbWO4, the latter being the scintillator used for the CMS ECAL, observed when the incident particle trajectory is aligned with a lattice axis within ∼1∘. This remarkable effect, being observed over the wide energy range from a few GeV to 1 TeV or higher, paves the way for the development of innovative calorimeters based on oriented crystals, featuring a design significantly more compact than currently achievable while rivaling the current state of the art in terms of energy resolution in the range of interest for present and future forward detectors (such as the KLEVER Small Angle Calorimeter at CERN SPS) and source-pointing space-borne γ-ray telescopes

    Antiproton-nuclei annihilation cross section measurement at 125 keV

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    The experimental research with slow antiprotons and antineutrons to study hadron and nuclear physics has been widely performed in the 80’s and in the first half of the 90’s at LEAR (CERN). After the stop of LEAR in 1996, the activity in the nuclear physics field was continued and is currently carried out at at the Antiproton Decelerator (AD, CERN), the successor of LEAR, by the ASACUSA Collaboration who, alongside its main program devoted to the hyperfine spectroscopy of the ground state of antihydrogen and to the laser spectroscopy of antiprotonic helium, is also involved in performing measurements of the annihilation cross section σ\sigmaann_{ann} of low energy antiprotons on nuclei. The motivations for these measurements include the possibility of gaining information on the strong interaction both for the quark model and for the potential model by fixing the parameters of the antinucleon-nucleon interaction. In addition, both quark and potential models predict the existence of a resonant or bound antinucleon-nucleon state which could be revealed studying the behaviour of σann\sigma_{ann} at different energies and with different targets. Fundamental cosmology could benefit from a better knowledge of the antiproton σ\sigmaann_{ann} as well. The models that assume the existence of 'islands' of antimatter to explain the antimatter-matter asymmetry, need to investigate the importance of the annihilation mechanism to describe the evolution of the process in the spatial region of overlap between matter and antimatter. The existing experimental data show behaviours that cannot be described in a simple way. For instance for low antiproton momenta plab_{lab} below 60 MeV/c, the annihilation cross sections measured at LEAR do not increase with the mass number but have similar values for H, D and He, while in the case of heavy nuclei at 100 MeV/c, the σ\sigmaann_{ann} values measured by our group at AD seem to be larger than the one expected from a simple geometrical description. A 'modified black-disk model', which takes into account the focusing effect of the Coulomb attraction between the antiproton and the nuclei, seems to be in a quite good agreement with our experimental data. Also an extension of the high-energy Glauber model down to the MeV region, if the Coulomb and nuclear interaction and the change of the antiproton momentum inside a nucleus are introduced, reproduces quite well the experimental data for both high and low energy, although a mismatch between the model and some data needs more investigation. Recently, emphasis has been put also on a discrepancy between the results obtained at LEAR with antineutrons and those expected for antiprotons, since an optical potential that fits well all the available data on antiproton interactions with nuclei is not in agreement with the σ\sigmaann_{ann} for antineutrons on nuclei. Our group in the ASACUSA Collaboration, after having measured the antiproton annihilation σ\sigmaann_{ann} on Mylar, Sn, Ni and Pt at 5.3 MeV of kinetic energy, has addressed its experimental investigation to an energy below the MeV region where no data exist at all. This thesis work deals with the experimental apparatus, the technique to perform the measurements, the data analysis and the experiment results. Chapter 1 is devoted to the physical motivations of the experiment: after a brief historical introduction on the antiproton annihilation field, the open problems with the existing data will be presented. In Chapter 2 an introduction on the AD facility where the experiment has been performed will be given. The apparatus installed on the ASACUSA beam line will be described in all its parts, from the delivery of the antiprotons from the decelerator ring to the dump of the antiproton bunch on the end wall. The scintillators used for the detection of the antiproton annihilations in the target region, their acquisition system and the validation tests performed with cosmic rays and a dedicated beamtest, will be treated in Chapter 3. In Chapter 4 a description of the measurement technique which has been invented and developed for the experiment will be given. In the same Chapter, the data analysis and the needed Montecarlo simulations will be presented. Finally, the results of the antiproton σ\sigmaann_{ann} measurements will be given together with a short discussion on the comparison with the existing data and a brief outlook on future possibilities

    Exploiting the wide dynamic range of silicon photomultipliers for quantum optics applications

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    Silicon photomultipliers are photon-number-resolving detectors endowed with hundreds of cells enabling them to reveal high-populated quantum optical states. In this paper, we address such a goal by showing the possible acquisition strategies that can be adopted and discussing their advantages and limitations. In particular, we determine the best acquisition solution in order to properly reveal the nature, either classical or nonclassical, of mesoscopic quantum optical states.Comment: 13 pages, 13 figure

    Antiproton-nuclei cross sections with Woods-Saxon potential at low energies

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    The present knowledge of the antinucleons elastic scattering and annihilation processes in matter at low energies is limited to a few nuclei data in a small phase-space. Optical potential models are useful tools for modelling nuclear strong interaction of antinucleons with matter providing predictions at very low energies where data are missing. New calculations of elastic and annihilation cross sections for antiproton with nuclei using an optical potential of Woods-Saxon (WS) shape are presented. Preliminary predictions at low energies for carbon and calcium show clearly-measurable nuclear effects for nuclear elastic cross sections at large angles and momenta greater than 50 MeV/c. Some discrepancies in annihilation cross section comparing predictions and data are present using the same fitting parameters

    Upgrade of the scintillating bars detector for the ASACUSA experiment

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    The upgrade of the scintillating bars detector, used in the experiments of the ASACUSA Collaboration at the CERN Antiproton Decelerator is presented. The detector consists of several modules, each one made of ≈1m long scintillating bars, which allow the detection of the charged particles produced in the annihilations of antiprotons and antihydrogens. The mechanics, the electronic readout and the data acquisition system upgrade are described

    Boron imaging with a microstrip silicon detector for applications in BNCT

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    Boron Neutron Capture Therapy (BNCT) is a radiotherapic technique exploiting the \u3b1 particles produced after the irradiation of the isotope 10 of boron with thermal neutrons in the capture reaction . It is used to treat tumours that for their features (radioresistance, extension, localization near vital organs) cannot be treated through conventional photon-beams radiotherapy. One of the main limitations of this technique is the lack of specificity (i.e. the ability of localizing in tumour cells, saving the healthy tissues) of the compounds used to carry the 10B isotope in the organs to be treated. This work, developed in the framework of the INFN PhoNeS project, describes the possibility of boron imaging performed exploiting the neutrons photoproduced by a linac (the Clinac 2100C/D of the S. Anna Hospital Radiotherapy Unit in Como, Italy) and detecting the \u3b1 s with a non-depleted microstrip silicon detector: the result is a 1D scan of the boron concentration. Several boron doped samples have been analysed, from solutions of H3BO3 (reaching a minimum detectable amount of 25 ng of 10B) to biological samples of urine containing BPA and BSH (the two molecules currently used for the clinical trials in BNCT) in order to build kinetic curves (showing the absolute 10B concentration as a function of time). Further measurements are under way to test the imaging system with 10BPA\u2013Fructose complex perfused human lung samples

    Beam profile monitor for annihilation cross section measurements of antiprotons at 100 keV

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    The ASACUSA (the Atomic Spectroscopy And Collisions Using Slow Antiprotons) collaboration is planning to measure the cross sections of antiproton annihilations at kinetic energy 100 keV on targets of various mass numbers (C, Ni, Sn, and Pt) using the Antiproton Decelerator (AD) of CERN. No previous measurement exists in this region where the A-dependence of the cross section is expected to deviate from the A2/3(Batty et al, Nucl Phys A 689:721, 2001) as reported by the Obelix collaboration. A beam profile monitor based on secondary electron emission with a grid of electrode pads fabricated on an FR4-type glass-epoxy circuit board was developed for this measurement. The advantage of this kind of detector is that it is simple, lightweight, and low cost. It was used to measure the spatial profile of 100-ns-long beam pulses containing > 6 7 104antiprotons with an active area of 40 mm 7 40 mm and a spatial resolution of 4 mm. \ua9 2011 Springer Science+Business Media B.V
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