1,720,990 research outputs found
Production and acceleration of protons by Titanium Hydride solid disks via excimer laser ablation
No full textProton beams by Titanuim targe
Electromagnetic and geometric characterization of accelerated ion beams by laser ablation
No full textLaser ion sources offer the possibility to get ion beam useful to improve particle accelerators. Pulsed lasers
at intensities of the order of 108 W/cm2 and of ns pulse duration, interacting with solid matter in vacuum,
produce plasma of high temperature and density. The charge state distribution of the plasma generates
high electric fields which accelerate ions along the normal to the target surface. The energy of emitted ions
has a Maxwell–Boltzmann distribution which depends on the ion charge state. To increase the ion energy,
a post-acceleration system can be employed by means of high voltage power supplies of about 100 kV.
The post acceleration system results to be a good method to obtain high ion currents by a not expensive
system and the final ion beams find interesting applications in the field of the ion implantation, scientific
applications and industrial use. In this work we compare the electromagnetic and geometric properties,
like emittance, of the beams delivered by pure Cu, Y and Ag targets. The characterization of the plasma
was performed by a Faraday cup for the electromagnetic characteristics, whereas a pepper pot system
was used for the geometric ones. At 60 kV accelerating voltage the three examined ion bunches get a
current peak of 5.5, 7.3 and 15 mA, with a normalized beam emittance of 0.22, 0.12 and 0.09 mm mrad
for the targets of Cu, Y, and Ag, respectively
Linear Rogowski coil
No full textNowadays, the employment and development of fast current pulses require sophisticated systems to perform measurements. Rogowski coils are used to diagnose cylindrical shaped beams; therefore, they are designed and built with a toroidal structure. Recently, to perform experiments of radiofrequency biophysical stresses, flat transmission lines have been developed. Therefore, in this work we developed a linear Rogowski coil to detect current pulses inside flat conductors. The system is first approached by means of transmission line theory. We found that, if the pulse width to be diagnosed is comparable with the propagation time of the signal in the detector, it is necessary to impose a uniform current as input pulse, or to use short coils. We further analysed the effect of the resistance of the coil and the influence of its magnetic properties. As a result, the device we developed is able to record pulses lasting for some hundreds of nanoseconds, depending on the inductance, load impedance, and resistance of the coil. Furthermore, its response is characterized by a sub-nanosecond rise time (∼100 ps). The attenuation coefficient depends mainly on the turn number of the coil, while the fidelity of the response depends both on the magnetic core characteristics and on the current distribution along the plane conductors
Protons production by solid hydrogenated targets via excimer laser ablation
No full textThe production of proton beams by ns low intensity pulsed excimer laser ablation of solid hydrogenated targets is investigated. The targets used were solid disks produced by compression of TiH2 and CaH2 powder. The ion emission was analyzed by the time-of-flight (TOF) technique using a Faraday Cup as ion collector. We performed preliminary studies on the produced plasma in free expansion mode and under an accelerating voltage up to 15 kV, for different laser fluence values. The TOF spectra deconvolution through Maxwell-Boltzmann shifted function permitted us to evaluate the plasma temperature, particle density, ion charge state distributions, proton and ion energy and their relative yield. Using these special targets, we were able to obtain protons, titanium and calcium ion beams with a kinetic energy of some tens of keV
Proton extraction from transition metals using PLATONE
No full textIn thisworkwepresentastudyonprotonbeamsextractionfromaplasmageneratedbypulsedlaser
ablation oftitaniumandtantalumdisks.ThedeviceusedwasthePLATONElaserionsourceoperatingat
the LEASLaboratoryinLecce,Italy.ItisbasedonaKrFlaseroperatingatlowirradiance(109–1010 W/cm2)
and nspulseduration.Theprotonandionsemissionwasanalyzedbythetime-of-flight techniqueusing
a Faradaycupasioncollectorandanelectrostaticbarriertoidentifytheparticles.Studiesonthe
produced protonsandionsatdifferentlaserirradiancevalueswereperformed.Theextractedbeams
showedhighproton flux upto1010 protons/cm2
Characteristics of target polarization by laser ablation
Full text linkExperimental 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?
No full textThe 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. Second, 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
Emittance study of an accelerated ion beam provided by laser ablation
No full textEmittance study of an accelerated ion beam provided by laser ablatio
Production and Acceleration of Ion beams by Laser Ablation
No full textIn this work, we present a new pulsed laser ablation technique to obtain energetic ion beams. The
accelerator we made is a compact device able to extract and accelerate the ionic components of plasma
up to 160 keV per charge state. It is composed by a generating chamber containing an expansion
chamber used like first electrode. Next, a second electrode connected to ground and a third electrode
connected to negative voltage are used. The third electrode is used also as Faraday cup. By the analysis
of the ion signals we studied the plume parameters such as TOF accelerated signals, charge state, and
divergence
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