[en] Commercialization of peat briquetting technology was analyzed to know whether the technology is economically viable or not compared to commercialization of charcoal. The investigation of economic viability was assessed from raw-peat production to briquetting technologies. The briquettes were made by naturally dried of peat from Bisika, Bahimba, Ndongozi and Nyirabirande bogs, through a rotary pulverizer and a briquette press; they were carbonized into furnace at 450 °C to reduce its health effects. The burning rate of peat briquettes made varied from 0.178 kg/hour to 0.222 kg/hour. Ash content varying between 3 and 7.2 percent was also observed. The results showed that peat briquettes can be sold at USD0.18 per unit, with a total NPV of USD17.2 million. However, as the NPV tends to be zero, the selling price would be approximately USD0.155 per briquette. Monthly charcoal expenses were about USD23.20/household compared to a per-household cost of USD16.20/month of peat briquettes consumption; the supplanting of charcoal by peat briquettes would help the average Rwandan household reduce its monthly expenses by 30 percent. Peat briquettes utilization as cooking fuel in Rwanda could save 0.05 percent of CO_2 and more than 99 percent of CH_4 emissions, compared to charcoal emissions. - Highlights: • A technical process for peat production and peat briquetting. • An efficiency test of carbonized briquettes. • Commercialization of peat briquettes is compared to commercialization of charcoal. • Opportunities for greenhouse gas emissions reduction.

[en] At the Center for Relativistic Laser Science (CoReLS) petawatt (PW) lasers have been developed for the investigations of strong field physics. The CoReLS has successfully upgraded one of the existing PW laser beamlines to a 4 PW laser at 20 fs. From laser-driven charged-particle acceleration experiments, multi-GeV electrons and 90-MeV protons can be generated using the laser wakefield acceleration and the radiation pressure acceleration schemes, respectively. The GeV electron beam can be, in turn, used for Compton backscattering with another PW laser. Such a Compton scattering process can be examined for other quantum electrodynamics (QED) effects, including the radiation reaction effect and the Breit-Wheeler pair production process. PW lasers have, thus, offered new opportunities to pursue novel physics research in relativistic plasma physics, strong field quantum electrodynamics, nuclear physics and laboratory astrophysics.

[en] High-power Ti:sapphire femtosecond laser systems have contributed significantly to advancements in various aspects of science; however, the stability of the laser systems limits the application of intense laser pulses. This study presents the development of a stable high-power femtosecond laser system. To this end, 25-TW laser pulses were generated at 10-Hz repetition rate from a chirped-pulse amplification Ti:sapphire laser seeded with a frequency-doubled erbium-fiber laser. Laser pulses with 54-fs duration and 780-nm central wavelength from the stable fiber laser were amplified to 2.3 J after sufficient temporal stretching. To shorten the temporal duration of the amplified pulse, the spectral bandwidth was broadened by controlling its spectral amplitude, and the spectral phase error was minimized by precisely controlling the pulse compressor. Finally, the compressed laser pulse had a high energy of 1.6 J, good energy stability of 0.8%, and a short duration of 60 fs, which is close to the seed pulse duration. Thus, the stable high-power femtosecond laser system developed in this study can facilitate various femtosecond laser pulse applications

[en] Korea country was set up over 30% greenhouse gas reduction target in comparison with BAU (Business as usual) at the national level, depending on climate change, which have been promoted as several technical and policy planning in order to reduce national greenhouse gas reduction. In this study, we derived the policies and technologies of power plant sector that is a high rate of reduction and public interest, we established a model for a common evaluation indicators and each of the evaluation factors between policy and technology priorities based on appropriate subject experts using analytic hierarchy process (AHP). Further we suggest insight to electricity company to establish the investment strategies of the technology and the associated policy by applying a weight evaluation index presenting a comprehensive priority.

[en] The generation of high-order harmonics is well-known method producing coherent extreme-ultraviolet radiation with pulse duration in the femtosecond regime. High-order harmonics have attracted much attention due to their unique features such as coherence, ultrashort pulse duration, and table-top scale system. Due to these unique properties, high-order harmonics have many applications of atomic and molecular spectroscopy, plasma diagnostics and solid-state physics. Bright generation of high-order harmonics is important for actual applications. Especially, the generation of strong well-collimated harmonics at 13 nm can be useful for the metrology of EUV lithography optics because of the high reflectivity of Mo-Si mirrors at this wavelength. The generation of bright high-order harmonics is rather difficult in the wavelength region below 15nm. Though argon and xenon gases have large conversion efficiency, harmonic generation from these gases is restricted to wavelengths over 20 nm due to low ionization potential. Hence, we choose neon for the harmonic generation around 13 nm; it has larger conversion efficiency than helium and higher ionization potential than argon. In this experiment, we have observed enhanced harmonic generation efficiency and low beam divergence of high-order harmonics from a elongated neon gas jet by the enhancement of laser propagation in an elongated gas jet. A uniform plasma column was produced when the gas jet was exposed to converging laser pulses.

[en] Development of ultrashort, high-power lasers has opened a pathway to generate very high order harmonics through highly nonlinear processes. This high-order harmonics can be utilized to applications, that require coherent x-rays. A number of studies have been devoted to increase both its efficiency and photon flux. To improve the number of harmonic photons in a microscopic gas medium the phase-matching conditions have to be fulfilled and also the propagation of pumping laser pulse has to be well controlled to couple laser energy with as many atoms as possible. In this work, we present experimental results of high-order harmonics obtained using a ion gas jet pumped by intense 28-fs laser pulses. a 6-mm slit nozzle and high intensity laser pulse over the saturation intensity were applied to generate an elongated interaction medium and to drive a large number of atoms with high laser intensity. The reflection of laser pulses in ionizing medium was monitored with a visible charge-coupled device (CCD) and a long uniform plasma column was observed when the gas jet was placed at the proper position of converging beam. Good phase matching between the driving laser pulse and generated harmonic signal was obtained by optimizing laser parameters, medium density and position.

[en] Coherent control of high-order harmonics was investigated to generate sharp harmonics. It has been known that high-order harmonics contain negative chirp due to dynamically induced harmonic chirp. We systematically analyzed the spectral structure of harmonics using chirped laser pulses, which revealed that sign of harmonic chirp was either negative or positive, depending on applied laser intensity. The application of appropriately chirped laser pulse allowed the generation of sharp and strong harmonics.

[en] We investigate the effect of laser polarization on spatial and momentum distribution of back-reflected e ⁻ e ⁺ pairs from the collision of an intense laser pulse (I = 5 × 10²² W cm⁻²) with a counter-propagating 5 GeV electron beam. During the pair production, a significant amount of particles (10⁶–10⁷) are ejected in the opposite direction of the incoming electron beam (back-reflected), they are trapped by and co-propagate with the laser beam, gaining energy up to the GeV level. From our multi-dimensional particle-in-cell studies, we observe that laser polarization affects the angular distribution of these particles: a linearly polarized pulse produces two transversely separated particle jets, while a circular one leads to the formation of a radially symmetric cone-shaped emission. The results presented here add insights for future experiments performed at multi-PW laser facilities. (paper)

[en] Laser wakefield acceleration (LWFA), owing to its large acceleration field, is a promising method for overcoming the limitations of radio-frequency linear accelerators. Recent demonstrations of petawatt (PW) lasers have afforded opportunities for further advancing research on LWFA. The research group at the ultrashort quantum beam facility (UQBF), Advanced Photonics Research Institute (APRI), Gwangju institute of science and Technology (GIST), developed PW lasers in 2010 and successfully applied these PW lasers to LWFA. LWFA research involving PW lasers was succeeded by the Center for Relativistic Laser Science (CoReLS), Institute for Basic Science (IBS). In this review, we summarize the research results from UQBF and CoReLS pertaining to LWFA

[en] We report here a systematic quantitative study on the generation and characteristics of an active muon source driven by the interaction of an electron beam within the energy range of 1–10 GeV from laser wakefield acceleration (LWFA) with a tungsten target, using Monte Carlo simulations. The 10 GeV electron beam, achievable in the near future, from LWFA using femtosecond multi-PW lasers is employed to drive the bright source of muon pairs in a compact setup. We show that a highly directional and intense source of short-pulsed GeV muon pairs (μ ⁻ μ ⁺) have a peak brightness of 5 × 10¹⁷ pairs s^–1cm^–2sr^–1 and sub-100 ps duration could be produced using a quasi-monoenergetic 10 fs, 10 GeV electron bunch with a 1-mrad divergence and 100 pC charge. The muon pairs are emitted from a point-like source with a well-defined position and timing; the source has a size and geometric emittance of about 1 mm and 40 μm, respectively. Such muon sources can greatly benefit applications in muon radiography as well as studies on anomalous dipole moments, rare decays of muons, neutrino oscillations, and an injector for a future compact muon collider. (paper)