Compact Thomson parabola spectrometer for fast diagnostics of different intensity laser-generated plasmas

Abstract

A compact Thomson parabola spectrometer for diagnostics of laser-generated plasma, projected in Messina University, has been employed in different experiments concerning diagnostics of lasergenerated plasmas. It allows to detect charged particles emitted from hot laser plasma and fast analyzing of their charge state, kinetic energy and mass-to-charge ratio. Moreover, it is possible to detect electrons emitted from laser-generated plasma. The spectrometer consists of a double pinhole input for alignment direction, a permanent magnet (0.004-4 kG) and an electric field (0.05-5 kV=cm) both orthogonal to the direction of the incident particles, and different type of planar detectors (multichannel plates, phosphorous screen, gafchromic, CR39 and PM 355 track detectors). Measurements have been acquired at MIFT in Messina observing electrons up to 10 keV kinetic energy, at INFN-LNS of Catania using ions emitted from plasma submitted to a postacceleration up to 30 kV per charge state and at PALS Laboratory in Prague detecting energetic ions above 1 MeV per charge state. The particles recognition using the Thomson spectrometer has been obtained comparing the experimental parabola curves with the theoretical simulations obtained using COMSOL software. Results will be presented and discussed.

Dependence of high-energy proton acceleration in TNSA regime by fs laser on the laser pulse shape

“…In addition, since the hydrogen signal area is about 1.2 × 10 −9 V×s, and the input impedance of the oscilloscope is 50 Ω, the number of accelerated protons is about 1.5×10 8 per laser shot. These measurements have been confirmed by further complementary analysis using different detection devices employed to monitor the plasma, such as ion collectors, stacked Gaf-Chromic films and others [24,25].…”

Eight MeV per charge state from 300 ps laser ion acceleration by using micrometric foils

“…This theory is valid for low laser and higher laser intensity provided that the duration of the laser pulse is not less than about 300 ps, otherwise the fast acceleration field can only accelerate the lighter ions (proton and carbon) but not the heavier ones. [ 21 ] The small peak between the photopeak and the ion peak is due to the detection of an X‐rays pulse probably produced by the return electrons on the target, which induces continuous Bremsstrahlung and characteristic X‐ray fluorescence emission. [ 2 ] This electron peak is detected at about 20 ns and it is not correlated to the flight distance of 60 cm but to a minor distance corresponding to the round trip of electrons emitted and returned to the target holder.…”

“…The maximum proton acceleration of about 6.5 MeV was measured in the Au target. The X‐ray emission, which increases with the atomic number of the target up to a saturation at higher Z values, in agreement with the literature. [ 21 ] The effect of self‐focusing that can be induced by the polymeric PET thin foil using a laser focal position in front of the target surface of −100 microns. In such configuration, a maximum proton energy of about 8.3 MeV was measured.…”

Novel Spectrometer Designs for Laser Driven Ion Acceleration

“…As it has been already done in refs [16,19], it is possible to tune the drift between the electric field to the detector L det with the aim of modifying the detectable energy spectra. The value of L det =30 cm in order to achieve the 1 cm magnetic deflection for 700 MeV protons (line 3 in Figure 4A).…”

“…The trapezoidal-shaped electric field plates have been used to circumvent the spectral clipping at the low energy end of the ion spectra [14,15]. All these changes [16][17][18][19][20][21] immensely support an extensive and thorough research of relevant laser-plasma processes.…”