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Tang, L

Publications and source records attributed to Tang, L.

8 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Bucking Coil Implementation on PMT for Active Cancelling of Magnetic Field

Aerogel and water Cerenkov detectors were employed to tag kaons for a lambda hypernuclear spectroscopic experiment which used the (e,e'K{sup +}) reaction in experimental Hall C at Jefferson Lab (JLab E05-115). Fringe fields from the kaon spectrometer magnet yielded ~5 Gauss at the photomultiplier tubes (PMT) for these detectors which could not be easily shielded. As this field results in a lowered kaon detection efficiency, we implemented a bucking coil on each photomultiplier tubes to actively cancel this magnetic field, thus maximizing kaon detection efficiency.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Improvement of near-infrared absorption linewidth in AlGaN/GaN superlattices by optimization of delta-doping location

We report a systematic study of the near-infrared intersubband absorption in AlGaN/GaN superlattices grown by plasma-assisted molecular-beam epitaxy as a function of Si-doping profile with and without {delta}-doping. The transition energies are in agreement with theoretical calculations including many-body effects. A dramatic reduction of the intersubband absorption linewidth is observed when the {delta}-doping is placed at the end of the quantum well. This reduction is attributed to the improvement of interface roughness. The linewidth dependence on interface roughness is well reproduced by a model that considers the distribution of well widths measured with transmission electron microscopy.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2011

Binding energy of (Lambda)He-7 and test of charge symmetry breaking in the Lambda N interaction potential

The binding energy of 7LambdaHe has been obtained for the first time with reaction spectroscopy using the (e, e'K+) reaction at Jefferson Lab's Hall C. A comparison among the binding energies of the A = 7 T = l iso-triplet hypernuclei, 7LambdaHe, 7LambdaLi*and 7LambdaBe, is made and possible charge symmetry breaking (CSB) in the LambdaN potential is discussed. For 7LambdaHe and 7LambdaBe, the shifts in binding energies are opposite to those predicted by a recent cluster model calculation, which assumes that the unexplained part of the binding energy difference between 4LambdaH and 4LambdaHe, is due to the CSB of the LambdaN potential. Further examination of CSB in light hypernuclear systems is required both experimentally and theoretically.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Tagged-weak {pi} method

A new 'tagged-weak {pi} method' is proposed for determination of electromagnetic transition probabilities B(E2) and B(M1) of the hypernuclear states with lifetimes of {approx}10{sup -10} s. With this method, we are planning to measure B(E2) and B(M1) for light hypernuclei at JLab. The results of Monte Carlo simulations for the case of E2(5/2{sup +}, 3/2{sup +} {yields} 1/2{sup +}) transitions in {sub {Lambda}}{sup 7}He hypernuclei are presented.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Precise Extraction of the Induced Polarization in the {sup 4}He(e,e{sup '}p-vector){sup 3}H Reaction

We measured with unprecedented precision the induced polarization P{sub y} in {sup 4}He(e,e{sup '}p-vector){sup 3}H at Q{sup 2}=0.8 and 1.3 (GeV/c){sup 2}. The induced polarization is indicative of reaction-mechanism effects beyond the impulse approximation. Our results are in agreement with a relativistic distorted-wave impulse approximation calculation but are overestimated by a calculation with strong charge-exchange effects. Our data are used to constrain the strength of the spin-independent charge-exchange term in the latter calculation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗