Search NASA⌕ Search

SEARCH · Search NASA

Results for “General Physics,PHYS”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

8 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Topological Quantization in Units of the Fine Structure Constant

Fundamental topological phenomena in condensed matter physics are associated with a quantized electromagnetic response in units of fundamental constants. Recently, it has been predicted theoretically that the time-reversal invariant topological insulator in three dimensions exhibits a topological magnetoelectric effect quantized in units of the fine structure constant {alpha} = e{sup 2}/{h_bar}c. In this Letter, we propose an optical experiment to directly measure this topological quantization phenomenon, independent of material details. Our proposal also provides a way to measure the half-quantized Hall conductances on the two surfaces of the topological insulator independently of each other.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

A Silicon-Tungsten ECal with Integrated Electronics

We summarize recent R&D progress for a silicon-tungsten electromagnetic calorimeter (ECal) with integrated electronics, designed to meet the ILC physics requirements. A basic physics requirement for ILC detectors is that they provide excellent reconstruction of hadronic final states. This allows access to new physics which is complementary to the LHC. One statement for a requirement on jet reconstruction is that intermediate particles which decay into jets, such as W, Z, or top, can be identified and isolated. This places unprecedented requirements on 2-jet or 3-jet mass resolution, typically at the level of 3-5% using the PFA technique, which makes challenging demands on the calorimeters. The electromagnetic energy resolution is not expected to limit jet resolution using a PFA. However, particle separation - photon-photon and charged hadron-photon - is crucial. In addition, if one provides this kind of imaging calorimeter to meet the PFA needs, these same features will also be put to good use for reconstruction of specific tau decay modes (to enable final-state polarization measurement), to 'track' photons (even if originating from a vertex displaced from the interaction point), to track MIPS, and so forth. Figure 1 and Table 1 provide some context for our ECal design within the SiD detector concept, along with some main design parameters. More detail is included in the presentation.

43 PARTICLE ACCELERATORS↗
DOE OSTI2011

ILC Instrumentation R&D at SCIPP

The Santa Cruz Institute for Particle Physics (SCIPP) continues to be engaged in research and development towards an ILC detector. The latest efforts at SCIPP are described, including those associated with the LSTFE front-end readout ASIC, the use of charge division to obtain a longitudinal coordinate from silicon strip detectors, and the contribution of strip resistance to readout noise.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Photoluminescence of Diamondoid Crystals

The photoluminescence of diamondoids in the solid state is examined. All of the diamondoids are found to photoluminesce readily with initial excitation wavelengths ranging from 233 nm to 240 nm (5.3 eV). These excitation energies are more than 1 eV lower than any previously studied saturated hydrocarbon material. The emission is found to be heavily shifted from the absorption, with emission wavelengths of roughly 295 nm (4.2 eV) in all cases. In the dissolved state, however, no uorescence is observed for excitation wavelengths as short as 200 nm. We also discuss predictions and measurements of the quantum yield. Our predictions indicate that the maximum yield may be as high as 25%. Our measurement of one species, diamantane, gives a yield of 11%, the highest ever reported for a saturated hydrocarbon, even though it was likely not at the optimal excitation wavelength.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Strongly aligned gas-phase molecules at free-electron lasers

Here, we demonstrate a novel experimental implementation to strongly align molecules at full repetition rates of free-electron lasers. We utilized the available in-house laser system at the coherent x-ray imaging beamline at the linac coherent light source. Chirped laser pulses, i.e., the direct output from the regenerative amplifier of the Ti:Sa chirped pulse amplification laser system, were used to strongly align 2, 5-diiodothiophene molecules in a molecular beam. The alignment laser pulses had pulse energies of a few mJ and a pulse duration of 94 ps. A degree of alignment of $\langle {\mathrm{cos}}^{2}{\theta }_{2{\rm{D}}}\rangle =0.85$ was measured, limited by the intrinsic temperature of the molecular beam rather than by the available laser system. With the general availability of synchronized chirped-pulse-amplified near-infrared laser systems at short-wavelength laser facilities, our approach allows for the universal preparation of molecules tightly fixed in space for experiments with x-ray pulses.

74 ATOMIC AND MOLECULAR PHYSICS↗