14502654
Beam test of novel n-in-p strip sensors for high radiation environment
Abstract Highly radiation tolerant n-in-p strip sensors have been developed for the high-luminosity LHC (HL-LHC). This paper reports the results of measurements with 392 MeV kinetic energy proton beam at RCNP in December 2011. The data was taken with a new DAQ system consisting of an universal read-out board ‘SEABAS’ and beam tracking telescopes whose spacial resolution is better than 5 μ m . The aim of this beam test is to evaluate the new 1 cm×1 cm n-in-p miniature sensors before and after 10 15  n eq  cm −2 irradiation. The median charge of un-irradiated sensor is 6.2 fC at full depletion voltage, while the median charge after 10 15  n eq  cm −2 irradiation of the sensor is 4.2 fC. The novel Punch-Through-Protection (PTP) has been implemented in these sensors. The length of active region of the sensor around PTP is observed to be decreased by 12 μ m in the irradiated sensors at 10 15  n eq  cm −2 .
10281433
Evaluation of test structures for the novel n + -in-p pixel and strip sensors for very high radiation environments
Abstract Radiation-tolerant n + -in-p silicon sensors were developed for use in very high radiation environments. Novel n + -in-p silicon strip and pixel sensors and test structures were fabricated, tested and evaluated, in order to understand the designs implemented. The resistance between the n + implants (interstrip resistance), the electric potential of the p-stop, and the punch-through-protection (PTP) onset voltage were measured before and as a function of fluence after irradiation. The technology computer-aided design (TCAD) simulations were used to understand the radiation damage and fluence dependence of the structures. The decrease in the interstrip resistance is a consequence of increased leakage current. The decrease in the electric potential of the p-stop results from a build-up of positive charge in the silicon–silicon oxide interface. The decrease and subsequent increase in the PTP onset voltages results from the interface charge build-up and an increase in acceptor states.
118254672
A Combine On-Line Acoustic Flowmeter and Fluorocarbon Coolant Mixture Analyzer for The ATLAS Silicon Tracker
An upgrade to the ATLAS silicon tracker cooling control system may require a change from C3F8 (octafluoro-propane) to a blend containing 10-30% of C2F6 (hexafluoro-ethane) to reduce the evaporation temperature and better protect the silicon from cumulative radiation damage with increasing LHC luminosity. Central to this upgrade is a new acoustic instrument for the real-time measurement of the C3F8/C2F6 mixture ratio and flow. The instrument and its Supervisory, Control and Data Acquisition (SCADA) software are described in this paper. The instrument has demonstrated a resolution of 3.10-3 for C3F8/C2F6 mixtures with ~20%C2F6, and flow resolution of 2% of full scale for mass flows up to 30gs-1. In mixtures of widely-differing molecular weight (mw), higher mixture precision is possible: a sensitivity of < 5.10-4 to leaks of C3F8 into the ATLAS pixel detector nitrogen envelope (mw difference 160) has been seen. The instrument has many potential applications, including the analysis of mixtures of hydrocarbons, vapours for semi-conductor manufacture and anaesthesia.
109227545
ATLAS silicon microstrip tracker operation and performance
Abstract The Semi-Conductor Tracker (SCT) is one of the key precision tracking devices in the ATLAS experiment at CERN Large Hadron Collider (LHC). The SCT was constructed of 4088 modules for a total of 6.3 million silicon strips and was installed into the ATLAS experiment in 2007. The SCT has been fully operational since then, and achieves a good tracking performance from the startup of the LHC operation.
12898781
The two flavour Schwinger model: scaling of the scalar condensate
We investigate the continuum limit scaling of the scalar condensate in the $N_f=2$ Schwinger model on the lattice. We employ maximally twisted mass Wilson fermions and overlap fermions. We compute the scalar condensate by taking the trace of the propagator (direct method) and by utilizing the integrated Ward-Takahashi identity. While the scalar condensate comes out consistent using these two methods for a given kind of lattice fermions, we find --quite surprisingly-- large discrepancies for the scalar condensate between twisted mass and overlap fermions. These discrepancies are only resolved when using the point split current for twisted mass fermions.
59467926
Phase structure and critical temperature of two-flavor QCD with a renormalization group improved gauge action and clover improved Wilson quark action
We study the finite-temperature phase structure and the transition temperature of QCD with two flavors of dynamical quarks on a lattice with the temporal size $N_t=4$, using a renormalization group improved gauge action and the Wilson quark action improved by the clover term. The region of a parity-broken phase is identified, and the finite-temperature transition line is located on a two-dimensional parameter space of the coupling ($\beta=6/g^2$) and hopping parameter $K$. Near the chiral transition point, defined as the crossing point of the critical line of the vanishing pion mass and the line of finite-temperature transition, the system exhibits behavior well described by the scaling exponents of the three-dimensional O(4) spin model. This indicates a second-order chiral transition in the continuum limit. The transition temperature in the chiral limit is estimated to be $T_c = 171(4)$ MeV.
37736424
Heavy-light spectrum and decay constant from NRQCD with two flavors of dynamical quarks
We report on a study of B mesons on Nf = 2 full QCD configurations using an RG-improved gauge action, NRQCD heavy quark action and tadpole-improved clover light quark action. Results on the heavy-light spectrum and the decay constants from 163 × 32 lattices at a−1 ≈ 1.5 GeV are presented, and compared with quenched results obtained with the same action combination at matching lattice spacings.
3243998
Testing topology conserving gauge actions for Lattice QCD
We explore gauge actions for lattice QCD, which are constructed such that the occurrence of small plaquette values is strongly suppressed. Such actions orig inate from the admissibility condition in order to conserve the topological charge. The suppression of small plaquette values is expected to be advantageous for numerical studies in the e-regime and also for simulations with dynamical quarks. Performing simulations at a lattice spacing of about 0.1 fm, we present numerical results for the static potential, the physical scale r0, the stability of the topological charge history, the condition number of the kernel of the overlap operator and the acceptance rate against the step size in the local HMC algorithm.