Synchronous post-acceleration of laser-driven protons in helical coil targets by controlling the current dispersion

Post-acceleration of protons in helical coil targets driven by intense, ultrashort laser pulses can enhance ion energy by utilizing the transient current from the targets’ self-discharge. The acceleration length of protons can exceed a few millimeters, and the acceleration gradient is of the order of GeV/m. How to ensure the synchronization between the accelerating electric field and the protons is a crucial problem for efficient post-acceleration. In this paper, we study how the electric field mismatch induced by current dispersion affects the synchronous acceleration of protons. We propose a scheme using a two-stage helical coil to control the current dispersion. With optimized parameters, the energy gain of protons is increased by four times. Proton energy is expected to reach 45 MeV using a hundreds-of-terawatts laser, or more than 100 MeV using a petawatt laser, by controlling the current dispersion

Um programa de ginástica para coronariopatas Coletânea de Exercícios Sugeridos

The acceleration of super-heavy ions (SHIs) from plasmas driven by ultrashort (tens of femtoseconds) laser pulses is a challenging topic waiting for breakthrough. The detecting and controlling of the ionization process, and the adoption of the optimal acceleration scheme are crucial for the generation of highly energetic SHIs. Here, we report the experimental results on the generation of deeply ionized super-heavy ions (Au) with unprecedented energy of 1.2 GeV utilizing ultrashort laser pulses (22 fs) at the intensity of 10^22 W/cm2. A novel self-calibrated diagnostic method was developed to acquire the absolute energy spectra and charge state distributions of Au ions abundant at the charge state of 51+ and reaching up to 61+. The measured charge state distributions supported by 2D particle-in-cell simulations serves as an additional tool to inspect the ionization dynamics associated with SHI acceleration, revealing that the laser intensity is the crucial parameter for the acceleration of Au ions over the pulse duration. The use of double-layer targets results in a prolongation of the acceleration time without sacrificing the strength of acceleration field, which is highly favorable for the generation of high-energy super heavy ions

Introduction of Research Work on Laser Proton Acceleration and Its Application Carried out on Compact Laser–Plasma Accelerator at Peking University

Laser plasma acceleration has made remarkable progress in the last few decades, but it also faces many challenges. Although the high gradient is a great potential advantage, the beam quality of the laser accelerator has a certain gap, or it is different from that of traditional accelerators. Therefore, it is important to explore and utilize its own features. In this article, some recent research progress on laser proton acceleration and its irradiation application, which was carried out on the compact laser plasma accelerator (CLAPA) platform at Peking University, have been introduced. By combining a TW laser accelerator and a monoenergetic beamline, proton beams with energies of less than 10 MeV, an energy spread of less than 1%, and with several to tens of pC charge, have been stably produced and transported in CLAPA. The beamline is an object–image point analyzing system, which ensures the transmission efficiency and the energy selection accuracy for proton beams with large initial divergence angle and energy spread. A spread-out Bragg peak (SOBP) is produced with high precision beam control, which preliminarily proved the feasibility of the laser accelerator for radiotherapy. Some application experiments based on laser-accelerated proton beams have also been carried out, such as proton radiograph, preparation of graphene on SiC, ultra-high dose FLASH radiation of cancer cells, and ion-beam trace probes for plasma diagnosis. The above applications take advantage of the unique characteristics of laser-driven protons, such as a micron scale point source, an ultra-short pulse duration, a wide energy spectrum, etc. A new laser-driven proton therapy facility (CLAPA II) is being designed and is under construction at Peking University. The 100 MeV proton beams will be produced via laser–plasma interaction by using a 2-PW laser, which may promote the real-world applications of laser accelerators in malignant tumor treatment soon

Energetic laser-driven proton beams from near-critical-density double-layer targets under moderate relativistic intensities

Double-layer targets composed of near-critical-density carbon nanotube foams (CNFs) and solid foils have shown their advantages in laser-driven ion acceleration under high relativistic intensity. Here, we report the experimental and numerical results on the laser-accelerated proton beams from such targets under moderate relativistic intensities I -5 x 1019W/cm2. 40-TW femtosecond laser pulses were used to irradiate CNF-based double-layer targets. Compared to single-layer targets, significant enhancements on the cutoff energy and numbers of ions were observed. It was found that the CNF layer also leads to a larger divergence angle and a more homogeneous spatial distribution pro -file of the proton beam. Particle-in-cell simulations reveal the reason for the enhanced proton acceleration. It is found that the lateral electric field and the strong magnetic field built by the directly accelerated electrons from the CNF layer contribute to the enlarged divergence angle.11Nsciescopu

Brilliant femtosecond-laser-driven hard X-ray flashes from carbon nanotube plasma

Brilliant X- and γ-ray sources with ultrashort duration are widely pursued in fundamental science, industry and medicine. Compact femtosecond X-ray sources based on relativistic electrons accelerated by the laser wakefield in gases have performed outstandingly. Their energy conversion efficiency from laser to hard X-ray photons (>10 keV) is, however, limited to 10−7–10−5. Here we report the high-yield generation of hard X-ray flashes from targets made of carbon nanotubes, instead of gases. Orders-of-magnitude more electrons, accelerated to relativistic energy, are strongly wiggled inside a micrometre-scale, near-critical density plasma formed by the nanotube target, emitting 1012 high-energy photons per shot. The yield of hard X-rays exceeds 1010 photons per joule, corresponding to an unprecedented efficiency of 10−3. Irradiated by upcoming 10-PW-class lasers, such targets can deliver 10-MeV photons with brightness outperforming existing sources by two orders of magnitude. © 2022, The Author(s), under exclusive licence to Springer Nature Limited.11Nsciescopu

Measurements of D-D fusion neutrons generated in nanowire array laser plasma using Timepix3 detector

Pulse width modulation (PWM) is widely used in different applications. PWM transforms the information in the amplitude of a bounded input signal into the pulse width output signal without suffering from quantization noise. The frequency of the output signal is usually constant. In this paper, the new PWM system with frequency changing (PWMFM) is described. In such PWMFM the pulse width and also the carrier frequency are changed. Therefore, two independent pieces of information can be simultaneously transmitted over one channel; hence PWM and frequency modulation (FM) are simultaneously used. But such system needs 2 demodulators, one for PWM and the second for FM. PWMFM can be used in the following applications: LED light intensity control via PWM and several LED block switching by FM PWMFM is highly useful in motor speed control applications by PWM and direction of rotation with FM. PWMFM can be used also in a class-D audio amplifier for power control, e.g. coarse by means of FM and fine by PWM. PWMFM can be used for the simultaneous transmission of two independent information between all, mutual combinations of analog and digital circuits. The analog and digital circuits for modulation and demodulation of PWMF signal are described and measuring results are presented in this work