arXiv subjects

B. Michel

Publications and source records attributed to B. Michel.

6 recordsLinked to original sources

arXiv2015

The E00-110 experiment in Jefferson Lab's Hall A: Deeply Virtual Compton Scattering off the Proton at 6 GeV

We present final results on the photon electroproduction ($\vec{e}p\rightarrow epγ$) cross section in the deeply virtual Compton scattering (DVCS) regime and the valence quark region from Jefferson Lab experiment E00-110. Results from an analysis of a subset of these data were published before, but the analysis has been improved which is described here at length, together with details on the experimental setup. Furthermore, additional data have been analyzed resulting in photon electroproduction cross sections at new kinematic settings, for a total of 588 experimental bins. Results of the $Q^2$- and $x_B$-dependences of both the helicity-dependent and helicity-independent cross sections are discussed. The $Q^2$-dependence illustrates the dominance of the twist-2 handbag amplitude in the kinematics of the experiment, as previously noted. Thanks to the excellent accuracy of this high luminosity experiment, it becomes clear that the unpolarized cross section shows a significant deviation from the Bethe-Heitler process in our kinematics, compatible with a large contribution from the leading twist-2 DVCS$^2$ term to the photon electroproduction cross section. The necessity to include higher-twist corrections in order to fully reproduce the shape of the data is also discussed. The DVCS cross sections in this paper represent the final set of experimental results from E00-110, superseding the previous publication.

nucl-ex↗

arXiv2008

Utility of transient testing to characterize thermal interface materials

This paper analyzes a transient method for the characterization of low-resistance thermal interfaces of microelectronic packages. The transient method can yield additional information about the package not available with traditional static methods at the cost of greater numerical complexity, hardware requirements, and sensitivity to noise. While the method is established for package-level thermal analysis of mounted and assembled parts, its ability to measure the relatively minor thermal impedance of thin thermal interface material (TIM) layers has not yet been fully studied. We combine the transient thermal test with displacement measurements of the bond line thickness to fully characterize the interface.

physics.gen-ph↗

arXiv2008

High Performance Thermal Interface Technology Overview

An overview on recent developments in thermal interfaces is given with a focus on a novel thermal interface technology that allows the formation of 2-3 times thinner bondlines with strongly improved thermal properties at lower assembly pressures. This is achieved using nested hierarchical surface channels to control the particle stacking with highly particle-filled materials. Reliability testing with thermal cycling has also demonstrated a decrease in thermal resistance after extended times with longer overall lifetime compared to a flat interface.

physics.gen-ph↗

arXiv2007

Characterization of Thermal Interface Materials to Support Thermal Simulation

In this paper new characterization equipment for thermal interface materials is presented. Thermal management of electronic products relies on the effec-tive dissipation of heat. This can be achieved by the optimization of the system design with the help of simulation methods. The precision of these models relies also on the used material data. For the determi-nation of this data an experimental set-up for a static measurement is presented, which evaluates thermal conductivity and interface resistance of thermal inter-face materials (e.g. adhesive, solder, pads, or pastes). A qualitative structure-property correlation is pro-posed taking into account particle size, filler content and void formation at the interface based on high resolution FIB imaging. The paper gives an overview over the set-up and the measurement technique and discusses experimental and simulation results.

cond-mat.mtrl-sci↗

arXiv2006

Measurements of the Electron-Helicity Dependent Cross Sections of Deeply Virtual Compton Scattering with CEBAF at 12 GeV

We propose precision measurements of the helicity-dependent and helicity independent cross sections for the ep->epg reaction in Deeply Virtual Compton Scattering (DVCS) kinematics. DVCS scaling is obtained in the limits Q^2>>Lambda_{QCD}^2, x_Bj fixed, and -Δ^2=-(q-q')^2< 2 GeV^2, W>2 GeV, and -Δ^21 GeV^2. We will use our successful technique from the 5.75 GeV Hall A DVCS experiment (E00-110). With polarized 6.6, 8.8, and 11 GeV beams incident on the liquid hydrogen target, we will detect the scattered electron in the Hall A HRS-L spectrometer (maximum central momentum 4.3 GeV/c) and the emitted photon in a slightly expanded PbF_2 calorimeter. In general, we will not detect the recoil proton. The H(e,e'g)X missing mass resolution is sufficient to isolate the exclusive channel with 3% systematic precision.

nucl-ex↗

arXiv1999

Extinction and polarization of radiation by absorbing spheroids: shape/size effects and benchmark results

We use the separation of variables and T-matrix methods to calculate the optical properties of homogeneous spheroids with refractive indices from m = 1.3+0.0i up to 3+4i. It is found that the extinction cross-sections for highly absorbing spheroids are normally 1.5 -- 2 times larger than those for spheres of the same volume. The albedo of the non-spherical particles rather slightly depends on the particle shape and is mainly determined by the imaginary part of the refractive index. Beginning at some size, the spheroidal particles do not polarize the transmitted radiation independent of their shape. We also suggest a new approach for axisymmetric particles which would combine the strong aspects of both methods mentioned above and give several values of the cross-sections as benchmarks in tabular form.

astro-ph↗