Simulation Of Momentum Correlations With The Hijing Model

We study predictions of number and momentum correlation functions in heavy ion collisions based on the Heavy Ion Jet Interaction Integrator (HIJING). This work is part of a research program designed to establish whether dynamical effects other than viscosity can induce broadening of the C correlation induced by Gavin et al. Specifically, two million Au+Au collisions at sqrt(s)=200GeV were generated and a number correlation R2 and a similar correlation with momentum information C where analyzed. We observed an increase in the width of R2 and C with the respect to the evolution from most peripheral to central event classes. Additionally, we did not observe significant differences in the qualitative features of R2 and C. Further work must be done to investigate some outlying data points in this study

Model-Independent Tuning for Maximizing Free Electron Laser Pulse Energy

The output power of a free electron laser (FEL) has extremely high variance even when all FEL parameter set points are held constant because of the stochastic nature of the self-amplified spontaneous emission (SASE) FEL process, drift of thousands of coupled parameters, such as thermal drifts, and uncertainty and time variation of the electron distribution coming off of the photo cathode and entering the accelerator. In this work, we demonstrate the application of automatic, model-independent feedback for the maximization of average pulse energy of the light produced by free electron lasers. We present experimental results from both the European x-ray free electron laser at DESY and from the Linac Coherent Light Source at SLAC. We demonstrate application of the technique on rf systems for automatically adjusting the longitudinal phase space of the beam, for adjusting the phase shifter gaps between the undulators, and for adjusting steering magnets between undulator sections to maximize the FEL output power. We show that we can tune up to 105 components simultaneously based only on noisy average bunch energy measurements

Experimental demonstration of attosecond pump–probe spectroscopy with an X-ray free-electron laser

Pump–probe experiments with subfemtosecond resolution are the key to understanding electronic dynamics in quantum systems. Here we demonstrate the generation and control of subfemtosecond pulse pairs from a two-colour X-ray free-electron laser. By measuring the delay between the two pulses with an angular streaking diagnostic, we characterize the group velocity of the X-ray free-electron laser and show control of the pulse delay down to 270 as. We confirm the application of this technique to a pump–probe measurement in core-ionized para-aminophenol. These results reveal the ability to perform pump–probe experiments with subfemtosecond resolution and atomic site specificity