No Arabic abstract
THGEMs (THick Gas Electron Multiplier) of varying thickness, hole diameter and hole pitch have been studied. For a thinner-THGEM of thickness 0.2 mm, with hole diameter 0.2 mm, pitch 0.2 mm and narrow (5-10 {mu}m) rim, the performance of gain versus high voltage with different gas mixtures have been studied using 5.9 keV X-rays. In general, a gain of around 3times10^3 was obtained with a single board in Ar/iC4H10, and gains higher than 10^4 were obtained in Ne mixture at lower voltage. The dependence of the energy resolution on the drift and induction electric fields was measured and an energy resolution of 15.9% was obtained. A curved thinner-THGEM chamber with one-dimensional readout has been assembled for use in the diffraction studies at the Beijing Synchrotron Radiation Facility (BSRF). A cosmic-ray muon hodoscope based on thinner-THGEM was developed as a teaching experiment for the Graduate University of the Chinese Academy of Sciences (GUCAS).
We discuss the AdS/CFT correspondence in which space-time emerges from an interacting theory of D-branes and open strings. These ideas have a historical continuity with QCD which is an interacting theory of quarks and gluons. In particular we review the classic case of D3 branes and the non-conformal D1 brane system. We outline by some illustrative examples the calculations that are enabled in a strongly coupled gauge theory by correspondence with dynamical horizons in semi-classical gravity in one higher dimension. We also discuss implications of the gauge-fluid/gravity correspondence for the information paradox of black hole physics.
We revisit a recent bound of I. Shparlinski and T. P. Zhang on bilinear forms with Kloosterman sums, and prove an extension for correlation sums of Kloosterman sums against Fourier coefficients of modular forms. We use these bounds to improve on earlier results on sums of Kloosterman sums along the primes and on the error term of the fourth moment of Dirichlet $L$-functions.
In a previous paper [1], we have discussed the non-perturbative tuning of the chirally rotated Schroedinger functional (XSF). This tuning is required to eliminate bulk O(a) cutoff effects in physical correlation functions. Using our tuning results obtained in [1] we perform scaling and universality tests analyzing the residual O(a) cutoff effects of several step-scaling functions and we compute renormalization factors at the matching scale. As an example of possible application of the XSF we compute the renormalized strange quark mass using large volume data obtained from Wilson twisted mass fermions at maximal twist.
The conceptual design and operational principle of a novel high-efficiency, fast neutron imaging detector based on THGEM, intended for future fan-beam transmission tomography applications, is described. We report on a feasibility study based on theoretical modeling and computer simulations of a possible detector configuration prototype. In particular we discuss results regarding the optimization of detector geometry, estimation of its general performance, and expected imaging quality: it has been estimated that detection efficiency of around 5-8% can be achieved for 2.5MeV neutrons; spatial resolution is around one millimeter with no substantial degradation due to scattering effects. The foreseen applications of the imaging system are neutron tomography in non-destructive testing for the nuclear energy industry, including examination of spent nuclear fuel bundles, detection of explosives or drugs, as well as investigation of thermal hydraulics phenomena (e.g., two-phase flow, heat transfer, phase change, coolant dynamics, and liquid metal flow).
A sealed high gas pressure detector working in pure argon is assembled. It consists of a 5 cm $times$ 5 cm PCB THGEM (THick Gaseous Electron Multipliers). The detector structure and experimental setup are described. The performances under high pressure of 2 atm mainly consist in selecting optimal voltages for ionization region and induction region. The dependence of the shape of Alpha particle spectra measured with relative gas gain on gas pressure (1.3 $sim$ 2.0 atm) has been studied. The 8 groups of relative gas gain versus working voltage of THGEM expressed by weighting filed $E/P$ are normalized, being consistent with theory. The results show that the air tightness of the chamber is good measured by a sensitive barometer and checked with gas gain. The experimental results are compared with Monte Carlo simulation on energy deposition without gas gain involved.