D. Delle Side

Time-of-flight spectra for mapping of charge density of ions produced by laser

AbstractAspace-resolvedchargedensityofionsisderivedfromatime-resolvedcurrentofionsemittedfromlaser-producedplasmaandexpandedintothevacuumalongcollision-freeandfield-freepaths.Thisderivationisbasedonasimilarityrelationshipforioncurrentswith “frozen”charges observedatdifferentdistancesfromthetarget. This relationship makes itpossibletodetermine a map of ion charge density at selected times after the laser plasma interaction from signals of time-of-flightdetectors positioned at a certain distance from the target around a target-surface normal. In this work, we present mapsof the charge density of ions emitted from Cu and polyethylene plasmas. The mapping demonstrates that bursts of ionsare emitted at various ejection angles f n with respect to the target-surface normal. There are two basic directions f 1 and f 2 , one belonging to the fastest ions, i.e., protons and carbon ions, and the other one to the slowest ions being apart of each plasma plume.Keywords: Angular distribution of slow and fast ions; Ion expansion; Laser ion sources; Map of ion charge density;Modeling

Characteristics of target polarization by laser ablation

Experimental results are obtained concerning the target polarization, which aptly characterizes the laser ablation. The charge separation in the laser-produced plasma, structure of the ion front, and the current of fast electrons expanding into the vacuum chamber ahead of ions are of crucial importance for the interpretation of multi-peak structure of target currents appearing much later than the laser pulse. Of particular interest is the correlation between the partial maxima in the time-resolved target current and the square root of mass number of ionized species. The late-time negative charging of targets provides evidence for production of very slow ions by ionization of neutrals ablated at the target crater by radiation from plasma produced by 23 ns excimer krypton fluoride laser.

Drug trafficking, money laundering and the business cycle: does secular stagnation include crime?

The aim of the paper is to analyze theoretically and empirically the impact the macroeconomic cycle has on the accumulation of capital by organized crime, using estimates for the global drug market. So far the economic literature has neglected the relationships existing between illegal markets, money laundering, and the business cycle. We propose a dynamic model where the business cycle influences the criminal economy via two different channels. On the one side, illegal markets grow at variable rates, depending on the health of the legal economy. Secondly, a pass-through effect can exist, since the business cycle affects the legal markets which criminal operators use to launder their revenues. Furthermore, we analyze the consequences of a “saturation effect” limiting maximum accumulation of illegal capital. We find that overall illegal capital is affected by the business cycle through a capital multiplier; in addition to this, the dynamics of interest rates in financial markets can influence such multiplier.