As the strong thermal effect in the surface, intense pulsed ion beam (IPIB) has been extensively used in material surface modification. The ablation is an important part in the interaction process between IPIB and material. In order to investigate the ablation mechanism, combined with IPIB dynamic energy spectrum and infrared imaging diagnostic results, a two-dimensional axisymmetric heat conduction model considering the effect of ablated material was constructed to describe the ablation process and calculate the lost mass of the targets. The influences of beam parameters and ablated matter on the ablation rate were discussed. The experimental and simulative results of ablation threshold and mass were compared.

This paper presents the design and tests of a repetitive 800 kA fast linear transformer driver (LTD) stage aimed for the Z-pinch driven fusion-fission hybrid reactor (Z-FFR).The LTD stage consists of 34 parallel basic resistor R, inductor L, and capacitor C (RLC) circuits each made up of two 100 kV/40 nF capacitors, a multi-stage gas switch and Metglas magnetic cores. The stage can deliver about 800 kA current pulse with rise time of 100 ns into the matched liquid resistive load at a repetitive frequency 0.1 Hz. A novel method to trigger the stage via a continuous internal trigger bus composed by a single cable has been proposed and demonstrated. The experimental results show that the new trigger method is feasible and reliable. A 140 kV, 25 ns rising time trigger pulse, and a 5.2 kA, 30 μs width pre-magnetization current pulse which can operate at a repetition rate 0.1 Hz were used in this stage to insure the LTD stage generating a 80 kV/800 kA current pulse every 10 s. A multi-stage gas switch that has a lifetime in excess of 10,000 shots and a jitter less than 3 ns one sigma agrees well with the demand of Z-FFR. The electrical behavior of the stage can be predicted from a simple RLC circuit, which can simplify the design of various LTD-based accelerators.

The aneutronic 11B(p, α)2α fusion reaction driven by the interaction of high-energy lasers with matter has become a popular topic of research, since it represents a potential long-term goal alternative to the most studied deuterium-tritium reaction. However, the detection of the typical ionic products, especially alpha particles, of this low-rate fusion reaction is a challenging issue, due to their low flux. One of the diagnostic devices that can be implemented in laser-driven proton-boron fusion experiments is a Thomson spectrometer (TS), which is capable of detecting and discriminating ions according to their mass-to-charge ratio (A/Z, where A is the mass number and Z is the atomic number of the ions). In this work, we report on the ultimate test of a TS, which was designed and developed at the ENEA Research Centre in Frascati, Italy, in the context of a p + 11B fusion experiment. Our device—designed to have high sensitivity and a robust shielding against electromagnetic pulses (EMPs)—was implemented at the PALS laser facility (∼700 J in ∼350 ps pulses) at a distance of 367 mm from the laser-plasma interaction point. We analyse here the measured signals obtained with our device, focusing on the assessment of their signal-to-background ratio. Despite the presence of strong EMPs and background radiation at such a short distance from the laser-irradiated target, the TS proved to be suitable for effectively detecting protons and heavier ions stemming from the plasma source.

In this paper we present a newly developed one-dimensional hydrodynamic simulation code and use it to determine the shock evolution in flyer plate impact experiments. The code is Lagrangian with artificial viscosity and uses shock Hugoniot data in its equation-of-state calculations instead of SESAME data tables. First shock calculations for transparent targets show a good agreement with theoretical predictions, making the code suitable for designing future flyer impact experiments at the Nevada Terawatt Facility.

The results of formation of elongated krypton/helium plasma channels are presented. Two laser pulses were used: one to produce plasma channels and the second one for conversion to soft X rays. The soft X-ray radiation was in turn used for backlighting the channels and their visualization. The study of their formation and uniformity was performed using a combination of soft X-ray shadowgraphy and pinhole camera imaging. The plasma channels, with various lengths and various densities, were visualized and the results of their characterization are presented. Using moderate laser pulse energy quite uniform channels, up to 9 mm in length, were demonstrated.

Liquid leaf targets show promise as high repetition rate targets for laser-based ion acceleration using the Target Normal Sheath Acceleration (TNSA) mechanism and are currently under development. In this work, we discuss the effects of different ion species and investigate how they can be leveraged for use as a possible laser-driven neutron source. To aid in this research, we develop a surrogate model for liquid leaf target laser-ion acceleration experiments, based on artificial neural networks. The model is trained using data from Particle-In-Cell (PIC) simulations. The fast inference speed of our deep learning model allows us to optimize experimental parameters for maximum ion energy and laser-energy conversion efficiency. An analysis of parameter influence on our model output, using Sobol’ and PAWN indices, provides deeper insights into the laser-plasma system.

Flux waveforms of aluminum cluster beams supplied from a laser-ablation cluster source were precisely investigated under various source conditions such as background pressure, ablation laser intensity, and nozzle structure. A time-of-flight mass spectroscopy revealed that aluminum clusters with sizes up to 200 were generated and the amount of the clusters could be maximized by choosing a proper background pressure (~2 MPa) and an ablation laser fluence (~40 mJ/cm2). Flux waveforms of clusters having specific sizes were carefully reconstructed from the observed mass spectra. It is found that the pulse widths of the aluminum cluster beams were typically about 100 µs and much smaller than that of the monoatomic aluminum beam, indicating that the cluster formation was limited in a relatively small volume in the laser-ablated vapor. Introducing a conical nozzle having a large open angle was also found to enhance the cluster beam velocity and reduce its pulse width. A velocity measurement of particles in the cluster beam was conducted to examine the velocity spread of the supplied clusters. We found that the aluminum clusters were continuously released from the source for about 100 µs and this release time mainly determined the pulse width of the cluster beam, suggesting that controlling the behavior of an ablated vapor plume in the waiting room of the cluster source holds the key to drastically improving the cluster beam flux.

In terms of energy conservation and vector matching relations, the dynamic process of the second harmonic emission from a laser plasma has been analyzed in this article for the first time. Then, considering the Langmuir wave spectrum which reflects the second harmonic spectrum, we derive the kinetic equation of the Langmuir wave. After a numerical Fourier analysis, the spectrum profiles are obtained, which coincide well with the experiments.

Formation of transverse inhomogeneities in the corona of a solid target irradiated by an inhomogeneous main laser pulse and a uniform background pulse was observed experimentally via side-on shadowgraphy. The experimental results were successfully interpreted using a two-dimensional hydrodynamics code. Our simulations identified the onset of sharp contact boundaries between plasma streams of different expansion velocities. The formation and the decay of the contact boundaries is investigated in detail. When the background pulse is used as a laser prepulse, a layer of coronal plasma is formed that enhances main pulse collisional absorption in underdense plasma and creates conditions for an efficient thermal smoothing of the transverse inhomogeneities.

We report on the observation of neutrons resulting from a thermonuclear reaction D + D = 3He(0.82 MeV) + n(2.45 MeV), taking place in plasma created on the surface of a modified solid-state target. The plasma was produced by a 200-fs laser pulse with intensity in excess of 1016 W/cm2 and energy of only 0.3 mJ.

We present a Rayleigh–Taylor mixing rate simulation with an acceleration rate falling within the range of experiments. The simulation uses front tracking to prevent interfacial mass diffusion. We present evidence to support the assertion that the lower acceleration rate found in untracked simulations is caused, at least to a large extent, by a reduced buoyancy force due to numerical interfacial mass diffusion. Quantitative evidence includes results from a time-dependent Atwood number analysis of the diffusive simulation, which yields a renormalized mixing rate coefficient for the diffusive simulation in agreement with experiment. We also present the study of Richtmyer–Meshkov mixing in cylindrical geometry using the front tracking method and compare it with the experimental results.

We consider ion projectile slowing down at low velocity Vp < Vthe, target thermal electron velocity, in a strongly coupled and de-mixing H-He ionic mixture. It is investigated in terms of quasi-static and critical charge-charge structure factors. Non-polarizable as well as polarizable partially degenerate electron backgrounds are given attention. The low velocity ion slowing down turns negative in the presence of long wavelength and low frequency hydromodes, signaling a critical de-mixing. This process documents an energy transfer from target ion plasma to the incoming ion projectile.

The superconducting synchrotron SIS100 of the FAIR accelerator project will provide heavy ion beams of highest intensities. SIS100 is the first synchrotron with a special design, optimized for the control of ionization beam loss. Ionization beam loss is the most pronounced loss mechanism at operation with high-intensity, intermediate charge state heavy ions. The new synchrotron layout comprises an ion catcher system, which in combination with a charge separator lattice shall suppress dynamic vacuum effects.

A prototype cryogenic ion catcher, including a dedicated cryostat has been designed, manufactured, and tested under realistic conditions with beams from the heavy-ion synchrotron SIS18 at GSI. The gas desorption induced by the impact of heavy ions on this cryocatcher has been measured. For the very first time, a rise of desorption yield with increasing beam energy has been observed. However, measurements at room temperature have confirmed the known decrease of the pressure rise in the investigated energy regime. A transition temperature of 18 K, underneath hydrogen is adsorbed, could be verified several times. The results are significant and used to predict the ionization beam loss at operation of SIS100 at full-beam intensity.

In this paper, we extend our previous work of classical over barrier ionization (COBI) model to study the multiple-ionization and mean charge state of noble gases colliding with heavy ions at energies close to the Bragg peak region ranging up to some hundreds of keV/amu. The method we report is in good agreement with experimental data and offers the advantage of very small computation time. Therefore, this model will be extremely helpful to be included in numerical codes to calculate the charge state distribution in plasma.

This paper presents numerical simulations to study the heating of a two-dimensional (2D) solid target under an ion cluster interaction. 2D quantum hydrodynamic (QHD) model is employed for the heating of solid target to warm dense matter on a picosecond time scale. A Gaussian cluster is used to uniformly heat the solid target to a temperature of several eV. The density and temperature of the target are calculated by a full self-consistent treatment of the QHD formalisms and the Poisson's equation. The technique described in this paper provides a method for creating uniformly heated strongly coupled plasma states.

To realize a heavy-ion inertial fusion (HIF) driver, we have studied a possibility of laser ion source (LIS). A LIS can provide high-current high-brightness heavy-ion beams; however, it was difficult to manipulate the beam parameters. To overcome the issue, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The rapid ramping magnetic field could enhance limited time slice of the current and simultaneously the beam emittance changed accordingly. This approach may also be useful to realize an ion source for HIF power plant.

The spatial profile, as well as ion-velocity distribution of laser-produced plasmas can be controlled experimentally by varying the time-form of laser pulse. A compression of nearly all produced plasma into a thin monovelocity spherical shell has been observed for the first time. A hydrodynamic numerical simulation shows that the shell generates due to special dynamics of ion ablation and geometry of experiment.

We report soft X-ray spectra (4–18 nm) produced by the interaction of 25–100-fs laser pulses at an intensity of up to 7 × 1016 W/cm2 with a cryogenically cooled Ar gas jet. New spectral lines from Ar8+, Ar9+, and Ar10+ charge states appeared with decreasing preexpansion gas temperature. A nonlinear increase of X-ray line emission from Ar7+, Ar8+, and Ar9+ was observed with cooling, which saturated below a certain temperature. The drastic change in the spectrum is attributed to efficient collisional heating and collisional ionization of growing, small- to medium-sized (102–103 atoms) Ar clusters from the cooled jet. When the laser pulse was extended from 25 to 100 fs we observed considerably stronger emission on lines from high charge states, such as Ar8+, Ar9+, and Ar10+, which suggests that the resonance absorption condition could be reached for the 100-fs pulse.

Plasmas with solid-state density at temperatures of a few eV will be produced in the near future at GSI by high-energy heavy ions. To diagnose these plasmas, novel methods–based on hard X-ray diagnostics–have to be applied. An investigation of the hydrodynamic expansion of the target requires a space- and time-resolved measurement of the plasma density. The determination of the target density independently of its temperature is obtained by a special X-ray pinhole camera enabling a selective registration of the target K-shell emission in combination with space- and time-resolved beam intensity measurements.