1,721,119 research outputs found
Novel pulse amplifying circuits by different characteristic impedance transmission lines
No full textTwo novel circuits used to amplify electric pulses by the coupling of transmission lines of different characteristic impedance are described. The circuits are intended for doubling voltage pulses and for doubling current pulses. The former is composed by a R0 transmission line closed on a set of two 2R0 storage lines connected in parallel, while the latter is composed by a R0 transmission line closed on a set of two R0/2 storage lines connected in series. The length of every storage line is half of input-pulse length. In both circuits, one storage line is characterized by an open extremity and the other line by a closed extremity. Connecting opportunely the storage lines to suitable load resistors, 4R0 and R0/4, for the circuit having parallel and series connected lines, respectively, a twice of the pulse intensity is obtained. Such devices are very suitable to generate high intensity voltage and/or current peaks which are very interesting in the field of the accelerators. Both circuit behaviours have been theoretically studied and verified by computer simulation
On the dynamics of a non-equilibrium Cu plasma produced by an excimer laser interaction with a solid
No full textWe report here on the expansion dynamics of a non-equilibrium plasma
produced by an excimer laser interaction with a Cu solid target. Its characteristics
were investigated in the fast and slow time regime by two Faraday cups of different
diameter. The larger cup had an 8 cm diameter collector and was fixed along a drift
tube at a distance of 20 cm from the plasma source; the smaller cup had a 3.3 cm
diameter collector and was fixed transversally to the target at a distance of about
6 cm. During the experiments the target support signal was also recorded. The
laser beam was focused onto the target and the spot dimensions were analysed
by scanning it on the lens focal plane. An average power density on the target of
0.3 GW cm−2 was achieved with a 15 cm focal length lens. Using signals from the
Faraday cups we obtained information on the overall plasma evolution in the slow
and fast time regimes. Fitting the plasma current waveform by a ‘shifted’ Maxwell–
Boltzmann distribution, a Knudsen-layer temperature of 5.3×105 K (∼50 eV) and
a drift velocity of 5300 m s−1 resulted. The system efficiency in ablation yield and
ion production was 0.235 μg pulse−1 and 5 × 1013 ion pulse−1, respectively
Pre- and post-extraction analyses of different charge state ion components produced in a laser ion source
No full textKnowledge of the relative abundance and the energy distributions of various ion species produced in laser ablation plasma is essential both in the fundamental physics ground, to understand the thermalization and expansion dynamics of the plasma plume, and in the applied physics ground, to get an efficient and versatile ion source. We present measurements and analyses related to such aspects, both for plasma in free expansion and for the extracted ion bunch. In particular, we characterized the former by means of ion current measurements, employing appropriate Faraday cups and electrostatic spectrometers; as regard as the latter, we performed time-of-flight spectrometry and depth profiling of implanted substrates. The extracted bunch signal showed modulation on time-of-flight due to the presence of multiply charged ions; depth profiling by X-ray photo-electron spectroscopy also showed a maximum penetration range and a profile modulation compatible with a multi-energetic beam. In these experiments we used UV excimer lasers, at irradiance values in the range 0.1 - 10 GW/cm2, to generate plasma from Cu and Al targets. The ion beams were extracted at voltages of tens of kV, DC
A study of electron beams ejected from a plasma produced by a laser interaction with a solid target
No full textIn this work waves formation in laser-produced plasma is investigated by an analysis of time-of-flight signal of the electron pulse. Electrons are extracted from a non-equilibrium plasma, generated by pulsed laser ablation on a solid Ge target. The process is represented by ion-acoustic waves, which are generated from an external perturbation, given by the positive bias voltage of a Faraday cup. The characteristics of the waves depend substantially on the geometry of the plasma expansion chamber and on laser fluence, while are independent on bias potential. A KrF excimer UV laser was employed for plasma generation. Measurements were performed at two different laser fluence, 4 J/cm2 and 7 J/cm2. The plasma created propagates with a mean velocity of about 1.1 ∙ 104 m/s. A movable Faraday cup was employed in order to collect electrons at different bias voltage values
Temperature measurement by Maxwell-Boltzmann distribution of a plasma-laser and characterization of the ion beam
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