Laser-induced thermal acoustics (LITA) signals from finite beams

Laser-induced thermal acoustics (LITA) is a four-wave mixing technique that may be employed to measure sound speeds, transport properties, velocities, and susceptibilities of fluids. It is particularly effective in high-pressure gases (>1 bar). An analytical expression for LITA signals is derived by the use of linearized equations of hydrodynamics and light scattering. This analysis, which includes full finite-beam-size effects and the optoacoustic effects of thermalization and electrostriction, predicts the amplitude and the time history of narrow-band time-resolved LITA and broadband spectrally resolved (multiplex) LITA signals. The time behavior of the detected LITA signal depends significantly on the detection solid angle, with implications for the measurement of diffusivities by the use of LITA and the proper physical picture of LITA scattering. This and other elements of the physics of LITA that emerge from the analysis are discussed. Theoretical signals are compared with experimental LITA data

Using Laboratory Experiments For Policy Making: An Example From The Georgia Irrigation Reduction Auction

In April 2000, the Georgia legislature passed a law requiring that the state use an unspecified "auction-like process" to pay some farmers to suspend irrigation in declared drought years. In response, we conducted a series of laboratory and field experiments to test a variety of auction procedures. This paper reports the results of these experiments, and how they were used by the policy makers who determined the auction procedures. Experimental results are compared with farmers' bidding behavior in the state-run irrigation auction conducted in March 2001. Working Paper # 2002-00

MULTIPAC, a multiple pool processor and computer for a spacecraft central data system, phase 2 Final report

MULTIPAC, multiple pool processor and computer for deep space probe central data syste

Signatures of quantum chaos in rare-earth elements: I. Characterization of the Hamiltonian matrices and coupling matrices of Ce I and Pr I using the statistical predictions of Random Matrix Theory.

Using the relativistic configuration interaction Hartree–Fock method the Hamiltonian matrices of Ce I, J = 4±, and Pr I, J = 11/2±, are studied. These matrices can be characterized as sparse, banded matrices, with a leading diagonal. Diagonalization of the Hamiltonian results in a set of energy eigenvalues and corresponding eigenvectors and the purpose of this investigation will be to characterize the Hamiltonian matrices and coupling matrices of Ce I and Pr I, for both ls and jj coupling representations, using various statistical predictions of Random Matrix Theory

A computational investigation of the impact of aberrated Gaussian laser pulses on electron beam properties in laser-wakefield acceleration experiments

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98752/1/PhysPlasmas_18_053110.pd

Exam 2 Strategy

After students take their first exam in an accounting course, tax accounting and intermediate accounting in this case, their reactions to their test scores may be varied. This is their first major assessment of how they have performed in the class. The students in the class near the high end of the grading scale are going to be satisfied with their score. Yet the overwhelming majority of students should be thinking about how they can do better on the next exam or an “Exam 2 strategy”. This paper describes a process which allows students to develop a strategy or “action plan” for their next exam. This process provides students a way to earn bonus points while developing their communication skills and showcasing their writing skills in a convenient electronic forum. Thus students develop their own strategy and benefit by considering the collective wisdom of the top ten strategies posted on the course web site. Detailed instructions are provided below to implement an “Exam 2 strategy” assignment which provides students an action plan to better their next exam scores

High Flux Femtosecond X-ray Emission from the Electron-Hose Instability in Laser Wakefield Accelerators

Bright and ultrashort duration X-ray pulses can be produced by through betatron oscillations of electrons during Laser Wakefield Acceleration (LWFA). Our experimental measurements using the \textsc{Hercules} laser system demonstrate a dramatic increase in X-ray flux for interaction distances beyond the depletion/dephasing lengths, where the initial electron bunch injected into the first wake bucket catches up with the laser pulse front and the laser pulse depletes. A transition from an LWFA regime to a beam-driven plasma wakefield acceleration (PWFA) regime consequently occurs. The drive electron bunch is susceptible to the electron-hose instability and rapidly develops large amplitude oscillations in its tail, which leads to greatly enhanced X-ray radiation emission. We measure the X-ray flux as a function of acceleration length using a variable length gas cell. 3D particle-in-cell (PIC) simulations using a Monte Carlo synchrotron X-ray emission algorithm elucidate the time-dependent variations in the radiation emission processes.Comment: 6 pages, 4 figures, accepted for publication in Phys. Rev. Accel. Beam

Signatures of quantum chaos in rare-earth elements: II. Characterization of the energy eigenvalues and dipole moments of Ce I and Pr I

Using the relativistic configuration interaction Hartree–Fock method the energy eigenvalues and dipole moments of Ce I, J = 4± and Pr I, J = 11/2±, both members of the rare earth sequence, are examined for the presence of signatures of quantum chaos, using the following spectral statistics: nearest neighbour spacing, covariance of adjacent spacings, spectral rigidity, correlation-hole method and χ2(ν) probability distribution

Multifractal analysis of selected rare-earth elements.

The multifractal formalism is applied to the energy eigenvalues of Ce I, CeII, Nd II, SmI, SmII, and Tb I. The R´enyi dimensionsDq , mass exponents τ(q) and f (α) spectra are calculated and used to characterize the eigenvalue spectra. It is found that these elements show multi-scaling behaviour that can be accurately modelled by simple multifractal recursive Cantor sets. The effect of unfolding the spectra is also investigated