Affolder, A. et al, Garcia, C., Lacasta, C., Marco, R., Marti-Garcia, S., Miñano, M., et al. (2011). Silicon detectors for the sLHC. Nucl. Instrum. Methods Phys. Res. A, 658(1), 11–16.
Abstract: In current particle physics experiments, silicon strip detectors are widely used as part of the inner tracking layers. A foreseeable large-scale application for such detectors consists of the luminosity upgrade of the Large Hadron Collider (LHC), the super-LHC or sLHC, where silicon detectors with extreme radiation hardness are required. The mission statement of the CERN RD50 Collaboration is the development of radiation-hard semiconductor devices for very high luminosity colliders. As a consequence, the aim of the R&D programme presented in this article is to develop silicon particle detectors able to operate at sLHC conditions. Research has progressed in different areas, such as defect characterisation, defect engineering and full detector systems. Recent results from these areas will be presented. This includes in particular an improved understanding of the macroscopic changes of the effective doping concentration based on identification of the individual microscopic defects, results from irradiation with a mix of different particle types as expected for the sLHC, and the observation of charge multiplication effects in heavily irradiated detectors at very high bias voltages.
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Llosa, G., Barrio, J., Lacasta, C., Callier, S., Raux, L., & de La Taille, C. (2011). First tests in the application of silicon photomultiplier arrays to dose monitoring in hadron therapy. Nucl. Instrum. Methods Phys. Res. A, 648, S96–S99.
Abstract: A detector head composed of a continuous LaBr3 crystal coupled to a silicon photomultiplier array has been mounted and tested, for its use in a Compton telescope for dose monitoring in hadron therapy. The LaBr3 crystal has 16 mm x 18 mm x 5 mm size, and it is surrounded with reflecting material in five faces. The SiPM array has 16 (4 x 4) elements of 3 mm x 3 mm size. The SPIROC1 ASIC has been employed as readout electronics. The detector shows a linear behavior up to 1275 keV. The energy resolution obtained at 511 keV is 7% FWHM, and it varies as one over the square root of the energy up to the energies tested. The variations among the detector channels are within 12%. A preliminary measurement of the timing resolution gives 7 ns FWHM. The spatial resolution obtained with the center of gravity method is 1.2 mm FWHM. The tests performed confirm the correct functioning of the detector.
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Studen, A., Chesi, E., Cindro, V., Clinthorne, N. H., Cochran, E., Grosicar, B., et al. (2011). A silicon PET probe. Nucl. Instrum. Methods Phys. Res. A, 648, S255–S258.
Abstract: PET scanners with high spatial resolution offer a great potential in improving diagnosis, therapy monitoring and treatment validation for several severe diseases. One way to improve resolution of a PET scanner is to extend a conventional PET ring with a small probe with excellent spatial resolution. The probe is intended to be placed close to the area of interest. The coincidences of interactions within the probe and the external ring provide a subset of data which combined with data from external ring, greatly improve resolution in the area viewed by the probe. Our collaboration is developing a prototype of a PET probe, composed of high-resolution silicon pad detectors. The detectors are 1 mm thick, measuring 40 by 26 mm(2), and several such sensors are envisaged to either compensate for low stopping power of silicon or increase the area covered by the probe. The sensors are segmented into 1 mm(3) cubic voxels, giving 1040 readout pads per sensor. A module is composed of two sensors placed in a back-to-back configuration, allowing for stacking fraction of up to 70% within a module. The pads are coupled to a set of 16 ASICs (VaTaGP7.1 by IDEAS) per module and read out through a custom designed data acquisition board, allowing for trigger and data interfacing with the external ring. This paper presents an overview of probe requirements and expected performance parameters. It will focus on the characteristics of the silicon modules and their impact on overall probe performance, including spatial resolution, energy resolution and timing resolution. We will show that 1 mm(3) voxels will significantly extend the spatial resolution of conventional PET rings, and that broadening of timing resolution related to varying depth of photon interactions can be compensated to match the timing resolution of the external ring. The initial test results of the probe will also be presented.
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Andricek, L. et al, Lacasta, C., Marinas, C., & Vos, M. (2011). Intrinsic resolutions of DEPFET detector prototypes measured at beam tests. Nucl. Instrum. Methods Phys. Res. A, 638(1), 24–32.
Abstract: The paper is based on the data of the 2009 DEPFET beam test at CERN SPS. The beam test used beams of pions and electrons with energies between 40 and 120 GeV, and the sensors tested were prototypes with thickness of 450 μm and pixel pitch between 20 and 32 μm. Intrinsic resolutions of the detectors are calculated by disentangling the contributions of measurement errors and multiple scattering in tracking residuals. Properties of the intrinsic resolution estimates and factors that influence them are discussed. For the DEPFET detectors in the beam test, the calculation yields intrinsic resolutions of approximate to 1 μm, with a typical accuracy of 0.1 μm. Bias scan, angle scan, and energy scan are used as example studies to show that the intrinsic resolutions are a useful tool in studies of detector properties. With sufficiently precise telescopes, detailed resolution maps can be constructed and used to study and optimize detector performance.
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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fassi, F., Ferrer, A., et al. (2012). A Particle Consistent with the Higgs Boson Observed with the ATLAS Detector at the Large Hadron Collider. Science, 338(6114), 1576–1582.
Abstract: Nearly 50 years ago, theoretical physicists proposed that a field permeates the universe and gives energy to the vacuum. This field was required to explain why some, but not all, fundamental particles have mass. Numerous precision measurements during recent decades have provided indirect support for the existence of this field, but one crucial prediction of this theory has remained unconfirmed despite 30 years of experimental searches: the existence of a massive particle, the standard model Higgs boson. The ATLAS experiment at the Large Hadron Collider at CERN has now observed the production of a new particle with a mass of 126 giga-electron volts and decay signatures consistent with those expected for the Higgs particle. This result is strong support for the standard model of particle physics, including the presence of this vacuum field. The existence and properties of the newly discovered particle may also have consequences beyond the standard model itself.
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