Radiation hardness of diamond and silicon sensors compared

The radiation hardness of silicon charged particle sensors is compared with single crystal and polycrystalline diamond sensors, both experimentally and theoretically. It is shown that for Si- and C-sensors, the NIEL hypothesis, which states that the signal loss is proportional to the Non-Ionizing Energy Loss, is a good approximation to the present data. At incident proton and neutron energies well above 0.1 GeV the radiation damage is dominated by the inelastic cross section, while at non-relativistic energies the elastic cross section prevails. The smaller inelastic nucleon-Carbon cross section and the light nuclear fragments imply that at high energies diamond is an order of magnitude more radiation hard than silicon, while at energies below 0.1 GeV the difference becomes significantly smaller.Comment: 6 pages, 4 figurs, invited talk at the Hasselt Diamond Workshop, Feb. 200

Photoionization of monocrystalline CVD diamond irradiated with ultrashort intense laser pulse

Direct laser writing of conductive paths in synthetic diamond is of interest for implementation in radiation detection and clinical dosimetry. Unraveling the microscopic processes involved in laser irradiation of diamond below and close to the graphitization threshold under the same conditions as the experimental procedure used to produce three-dimensional devices is necessary to tune the laser parameters to optimal results. To this purpose a transient currents technique has been used to measure laser-induced current signals in monocrystalline diamond detectors in a wide range of laser intensities and at different bias voltages. The current transients vs time and the overall charge collected have been compared with theoretical simulations of the carrier dynamics along the duration and after the conclusion of the 30 fs laser pulse. The generated charge has been derived from the collected charge by evaluation of the lifetime of the carriers. The plasma volume has also been evaluated by measuring the modified region. The theoretical simulation has been implemented in the framework of the empirical pseudopotential method extended to include time-dependent couplings of valence electrons to the radiation field. The simulation, in the low-intensity regime, I\ensuremath{\sim}1\phantom{\rule{0.28em}{0ex}}\mathrm{TW}/{\mathrm{cm}}^{2}, predicts substantial deviation from the traditional multiphoton ionization, due to nonperturbative effects involving electrons from degenerate valence bands. For strong field with intensity of about $50\phantom{\rule{0.28em}{0ex}}\mathrm{TW}/{\mathrm{cm}}^{2}$, nonadiabatic effects of electron-hole pair excitation become prominent with high carrier densities eventually causing the optical breakdown of diamond. The comparison of theoretical prediction with experimental data of laser-generated charge vs laser energy density yields a good quantitative agreement over six orders of magnitude. At the highest intensities the change of slope in the trend is explained taking into account the dependence of the optical parameters and the carrier mobility on plasma density

The ALICE experiment at the CERN LHC

ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries. Its overall dimensions are 161626 m3 with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008

Ion spectroscopy — A diamond characterization tool

The stopping power Delta E and the energy-loss resolution delta E/Delta E of Single-Crystal CVD-Diamond Detectors (SC-DDs) measured with relativistic Heavy Ions (HIs) are interpreted as global quality parameters, characterizing simultaneously crystal texture and carrier-trapping concentrations, as well as the charge-transport properties of intrinsic diamond samples. HI spectra are presented, where spectral lines are obtained similar to the predictions of the Lindhard and Sorensen (LS) theory [J. Lindhard, A.H. Sorensen, Phys. Rev. A 53 (1996) 2443]. The spectroscopic results indicate an almost defect free material, and spatial homogeneity of all parameters relevant to the detector signal (i.e., mass density, dielectric constant, drift mobility and velocity of the charge carriers). Measured and simulated transient current signals generated by relativistic Xe-132 ions are discussed according to theories [A. Many, G. Rakavy, Phys. Rev., 126 (1962) 1980: G. Juska, M. Viliunas. O. Klima, E. Sipek. J. Kocka, Phil, Mag. B 69 (1994) 277; G. Juska, M. Viliunas, K. Arlauskas, J. Kocka, Phys. Rev. B 51 (1994) 16 668] of space-charge limited current (SCLC) transients. The evidence of the spectroscopic results is confirmed by the current-mode studies, and thus indirectly, the potential of the characterization method as well