68 research outputs found
An Overview of Recent Progress in Laser Wakefield Acceleration Experiments
No full textThe goal of this paper is to examine experimental progress in laser wakefield acceleration over the past decade (2004–2014), and to use trends in the data tounderst and some of the important physical processes. By examining a set of over 50 experiments, various trends concerning the relationship between plasma density, accelerator length, laser power and the final electron beam energy are revealed. The data suggest that current experiments are limited by dephasing and that current experiments typically require some pulse evolution to reach the trapping threshold.The goal of this paper is to examine experimental progress in laser wakefield acceleration over the past decade (2004-2014), and to use trends in the data to understand some of the important physical processes. By examining a set of over 50 experiments, various trends concerning the relationship between plasma density, accelerator length, laser power and the final electron beam en- ergy are revealed. The data suggest that current experiments are limited by dephasing and that current experiments typically require some pulse evolution to reach the trapping threshold
Sadie Peterson Delaney Article, June 1951
No full textAn article written on the career and accomplishments of Dr. Sadie Peterson Delaney. The author also mentions of Delaney's humanitarian work, discussing her dedication to working with the "socially handicapped." Written on recto: It will probably be two or three years [?] I retire. S.P.D
Measurements of forward scattered spectra from intense laser interactions in the forced laser wake-field regime
No full textInternational audienceResults of an experiment using an ultra-short laser pulse to create plasma waves through the forced laser wake-field process are described. The transmitted optical spectra are shown to exhibit both red- and blue-shifting, likely due to self-phase modulation through the interaction between the laser pulse and a large amplitude plasma wave. Spectral side-bands shifted by multiples of the plasma frequency associated with the forward Raman instability (FRS) are absent, indicating that the plasma waves which are observed to accelerate electrons are likely not generated through the FRS process. One- and two-dimensional particle-in-cell simulations using similar parameters as the experiment are discussed
Modeling few-cycle shadowgraphy of laser-wakefield accelerators
No full textInternational audienceUltrafast shadowgraphy utilizes few cycle probe pulses in order to image density gradients in a plasma allowing to probe structures, such as laser-driven wakes, moving close to the speed of light. Here we study the process of shadowgraphic image formation in the interaction of a few cycle probe pulse with a laser-driven wake using particle-in-cell (PIC) simulations. The output of the PIC code is then post-processed by means of Fourier optics in order to take into account the effect of a typical imaging setup. This allows to construct synthetic shadowgrams which can be compared with experimentally recorded ones. This facilitates the correct interpretation of such involved measurements
Electron Beam Production with an Ultra Short and Intense Laser Pulse: A New Tool for Scientists
No full textInternational audienceBy focusing a 10 Hz, 30 TW, 30 fs laser beam onto a gas jet, it is now possible to produce an ultra short and high quality electron beam with a maximum energy of up to 200 MeV. The gas is instantaneously ionized by the laser electric field and transformed into plasma, in which accelerating electric fields of the order of 1 TV/m have been generated in the non-linear regime. Some applications of this attractive and compact electron source are presented
Multi-Pulse Laser Wakefield Acceleration: A New Route to Efficient, High-Repetition-Rate Plasma Accelerators and High Flux Radiation Sources
No full textPaper 234003Laser-driven plasma accelerators can generate accelerating gradients three orders of magnitude larger than radio-frequency accelerators and have achieved beam energies above 1 GeV in centimetre long stages. However, the pulse repetition rate and wall-plug efficiency of laser plasma accelerators is limited by the driving laser to less than approximately 1 Hz and 0.1% respectively. Here we investigate the prospects for exciting the plasma wave with trains of low-energy laser pulses rather than a single high-energy pulse. Resonantly exciting the wakefield in this way would enable the use of different technologies, such as fibre or thin-disc lasers, which are able to operate at multi-kilohertz pulse repetition rates and with wall-plug efficiencies two orders of magnitude higher than current laser systems. We outline the parameters of efficient, GeV-scale, 10 kHz plasma accelerators and show that they could drive compact x-ray sources with average photon fluxes comparable to those of third-generation light source but with significantly improved temporal resolution. Likewise free-electron laser (FEL) operation could be driven with comparable peak power but with significantly larger repetition rates than extant FELs.47Nr. 2
Portofolio Kontrak Kerja PT Cakrawala Muda Mandiri
No full textMangsa. Moh. Sabrin, 2023. (CMM Translation). Counsellor: Dr. Muhammad Fadli Ramadan, S.P.D., M.P.D. The COE Internship Programmeme Arabic Translator, counselled by Muhammadiyah Malang University Arabic Education Studies Programmeme, aims to give the students the opportunity to apply the knowledge learned during the course in a more real world of work. This research covers the job offers received by the author. The company sees and evaluates that the performance of the author for the client is excellent, therefore the author gets the opportunity to work as a technician. The two-month internship programme is scheduled for October 2 and December 2, 2023. Working days at the Youth Independent Horizon are from Monday to Friday. The internship model applied at PT Cakrawala Muda Indiri is full-time. In carrying out his duties as an internship student, the CMM party divided it into two sections: administration and technicians, so the writer gained work experience during the internships taking place in the technician section. In this section, the author is tasked with preparing the device for the interpreter. Therefore, the writer really had good work experience
Electron trapping and acceleration on a downward density ramp: a two-stage approach
No full textIn a recent experiment at Lawrence Berkeley National Laboratory (Geddes et al 2008 Phys. Rev. Lett. 100 215004), electron bunches with about 1MeV mean energy and small absolute energy spread (about 0.3MeV) were produced by plasma wave breaking on a downward density ramp. It was then speculated that such a bunch might be accelerated further in a plasma of low constant density, while mostly preserving its small absolute energy spread. This would then lead to a bunch with a high mean energy and very low relative energy spread. In this paper, trapping of a low-energy, low-spread electron bunch on a downward density ramp, followed by acceleration in a constant-density plasma, has been explored through particle-in-cell simulations. It has been found that the scheme works best when it is used as a separate injection stage for a laserwakefield accelerator, where the injection and acceleration stages are separated by a vacuum gap
Modeling ultrafast shadowgraphy in laser-plasma interaction experiments
No full textInternational audienceUltrafast shadowgraphy is a new experimental technique that uses few cycle laser pulses to image density gradients in a rapidly evolving plasma. It enables structures that move at speeds close to the speed of light, such as laser driven wakes, to be visualized. Here we study the process of shadowgraphic image formation during the propagation of a few cycle probe pulse transversely through a laser-driven wake using three-dimensional particle-in-cell simulations. In order to construct synthetic shadowgrams a near-field snapshot of the ultrashort probe pulse is analyzed by means of Fourier optics, taking into account the effect of a typical imaging setup. By comparing synthetic and experimental shadowgrams we show that the generation of synthetic data is crucial for the correct interpretation of experiments. Moreover, we study the dependence of synthetic shadowgrams on various parameters such as the imaging system aperture, the position of the object plane and the probe pulse delay, duration and wavelength. Finally, we show that time-dependent information from the interaction can be recovered from a single shot by using a broadband, chirped probe pulse and subsequent spectral filtering
Realising single-shot measurements of quantum radiation reaction in high-intensity lasers
No full textModern laser technology is now sufficiently advanced that collisions between high-intensity laser pulses and laser-wakefield-accelerated (LWFA) electron beams can reach the strong-field regime, so that it is possible to measure the transition between the classical and quantum regimes of light–matter interactions. However, the energy spectrum of LWFA electron beams can fluctuate significantly from shot to shot, making it difficult to clearly discern quantum effects in radiation reaction (RR), for example. Here we show how this can be accomplished in only a single laser shot. A millimetre-scale pre-collision drift allows the electron beam to expand to a size larger than the laser focal spot and develop a correlation between transverse position and angular divergence. In contrast to previous studies, this means that a measurement of the beam's energy-divergence spectrum automatically distinguishes components of the beam that hit or miss the laser focal spot and therefore do and do not experience RR
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