Radiation experience with the CMS pixel detector

The CMS pixel detector is the innermost component of the CMS tracker occupying the region around the centre of CMS, where the LHC beams are crossed, between 4.3 cm and 30 cm in radius and 46.5 cm along the beam axis. It operates in a high-occupancy and high-radiation environment created by particle collisions. Studies of radiation damage effects to the sensors were performed throughout the first running period of the LHC . Leakage current, depletion voltage, pixel readout thresholds, and hit finding efficiencies were monitored as functions of the increasing particle fluence. The methods and results of these measurements will be described together with their implications to detector operation as well as to performance parameters in offline hit reconstruction

PULSE WIDTH MODULATED IGBT AC CHOPPER

A new circuit is presented for three-phase voltage controller (AC chopper) constructed from IGBTs. Traditionally such an equipment contains thyristors as switching elements. All drawbacks of this solution come from its only possible control method: firing control. The new circuit allows Pulse Width Modulation (PWM) control, providing much better properties. A new and advantageous control method is presented, including the protections also. Many application fields can be found, all require AC voltage control. The examined ones are: Energy-saving control of induction motor drive; Compensation of an unbalanced supply; Active filtering of the upper harmonics; Excitation system of brushless motor

Alignment of the CMS Tracking-Detector with First 2015 Cosmic-Ray and Collision Data

The performance of the CMS tracking-detector alignment with the first 2015 cosmic-ray data and proton-proton collision data at 13 TeV center-of-mass energy with the magnetic field at 0 T and 3.8 T is presented

Accurate interaction energies at DFT level by means of an efficient dispersion correction

This paper presents an approach for obtaining accurate interaction energies at the DFT level for systems where dispersion interactions are important. This approach combines Becke and Johnson's [J. Chem. Phys. 127, 154108 (2007)] method for the evaluation of dispersion energy corrections and a Hirshfeld method for partitioning of molecular polarizability tensors into atomic contributions. Due to the availability of atomic polarizability tensors, the method is extended to incorporate anisotropic contributions, which prove to be important for complexes of lower symmetry. The method is validated for a set of eighteen complexes, for which interaction energies were obtained with the B3LYP, PBE and TPSS functionals combined with the aug-cc-pVTZ basis set and compared with the values obtained at CCSD(T) level extrapolated to a complete basis set limit. It is shown that very good quality interaction energies can be obtained by the proposed method for each of the examined functionals, the overall performance of the TPSS functional being the best, which with a slope of 1.00 in the linear regression equation and a constant term of only 0.1 kcal/mol allows to obtain accurate interaction energies without any need of a damping function for complexes close to their exact equilibrium geometry