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A few-layer tungsten disulfide (WS2) nanosheet film on a YAG substrate was fabricated and used as saturable absorber in a passively Q-switched Er:SrF2 laser operating at 2.79 µm. Under an absorbed power of 2.42 W, a stable Q-switched laser operation was realized with an average output power of 428 mW and a pulse duration of 679 ns at a repetition rate of 38 kHz, corresponding to a pulse energy of 11.26 µJ.

The saturable absorption properties of multilayer tungsten diselenide (WSe2) nanosheets in 3 µm wavelength range were characterized for the first time. A stable passively Q-switched Er:Lu2O3 laser at 2.85 µm was achieved by using the home-made WSe2 saturable absorber (SA). Under an absorbed power of 7.24 W, a maximum average output power of 776 mW was obtained with a pulse duration of 280 ns at a repetition rate of 121 kHz, producing a pulse energy of 6.4 µJ and a peak power of 21.3 W.

The processes of plasma self-organization and formation of plasma structures at reduced pressures is considered with respect to the electrode microwave (2.45 GHz) discharge (EMD). The term EMD is attributed to discharge maintained near the ending of powered electrode/antenna if plasma region is less than characteristic dimensions of discharge chamber. EMD is generated at gas pressures ranged between 0.5 and 400 Torr, plasma gases are Ne, Ar, H2, N2, O2, air and mixtures containing CH4 C2H2. Electrodes/antennas of different shapes were used to ignite the discharge: solid and tube cylindrical antennas with diameter of 1-6 mm, needle, spiral and trident antennas etc. Plasma absorbed power is less than 30 W. Phenomenology of EMD is presented. Results of emission spectroscopy and probe measurements together with results of EMD modelling are described. The concept of ''selfsustained - non-selfsustained'' mechanism of EMD is concluded from analysis of publications on microwave discharges and results of study of EMD. Areas of possible EMD application are discussed.

Electrodynamic characteristics of the tunable cavity plasma source, as well as the optical and chemical properties of a nonequilibrium microwave plasma generated in this type of plasma device are presented. Some characteristic features of the adjustable length rectangular cavity plasma generator are described: (i) the possibility of continuing varying the plasma absorbed power without any variation of the incident microwave power, and (ii) the possibility of variation in the internal spatial structure of plasma. Products of methane decomposition in Ar+1% CH4 and Ne+1% CH4 microwave plasmas are compared with those measured in the positive column of a DC discharge under similar external parameters. The observed differences in the gas component concentrations and in the yields in the condensed phase are within a factor of three for both discharges, and can be attributed to distinctions in the internal structure of the discharges. These results are in agreement with previous theoretical considerations.

Using a combined ray tracing and Fokker-Planck code, an investigation is made on the propagation and absorption of the launched power spectrum during lower hybrid (LH) current drive in tokamaks, in a situation where toroidally induced ray stochasticity is important. Stochastic effects are correctly taken into account by tracing a large number of rays. The influence of the balance between the wave damping and the stochastic divergence of nearby ray trajectories in governing the power spectrum dynamics and in establishing the characteristics of the LH power deposition patterns is illustrated. It is shown that, when strong wave damping prevails, the launched power spectrum behaves regularly: the LH power deposition is localized and the absorbed power spectrum is very similar in shape to the launched one, although some broadening and shifting in the parallel wave index generally occur. If the wave damping is weak and stochastic effects are important, the rays end by covering the entire plasma cross-section and the power spectrum dynamics follows a diffusive pattern: the LH power deposition turns out to be extended and the absorbed power spectrum is much broader than the launched one, as a result of strong spreading towards the high absolute values of the parallel wave index

In JT-60, H-mode experiments with outer and lower divertors have been performed. In the outer divertor discharge, an H-mode similar to the modes observed in the lower/upper divertor discharges is obtained. Its threshold absorbed power and electron density are 16 MW and 1.8 × 1019 m−3. In the two schemes of combined heating with NB + ICRF and NB + LHRF, H-mode discharges are also obtained. Moreover, in the new configuration with the JT-60 lower divertor, H-mode phases with and without edge localized modes are obtained. The improvement in the energy confinement time in both divertor configurations is limited to values within 10%. The paper mainly presents the H-mode results of the outer divertor discharges. Also, typical results of the lower divertor discharges are shown for a comparison of the H-mode characteristics of the two configurations.

The use of more smaller industrial NH3 screw compressors operating in parallel seems to offer the optimum way when it comes to fulfilling maximum part load efficiency, increased redundancy and other highly requested features in the industrial refrigeration industry today. Parallel operation in an optimum way can be selected to secure continuous operation and can in most applications be configured to ensure lower overall operating economy. New compressors are developed to meet requirements for flexibility in operation and are controlled in an intelligent way. The intelligent control system keeps focus on all external demands, but yet striving to offer always the lowest possible absorbed power, including in future scenarios with connection to smart grid.

Full wave simulations of fusion plasmas show a direct correlation between the location of the fast-wave cut-off, radiofrequency (RF) field amplitude in the scrape-off layer (SOL) and the RF power losses in the SOL observed in the National Spherical Torus eXperiment (NSTX). In particular, the RF power losses in the SOL increase significantly when the launched waves transition from evanescent to propagating in that region. Subsequently, a large amplitude electric field occurs in the SOL, driving RF power losses when a proxy collisional loss term is added. A 3D reconstruction of absorbed power in the SOL is presented showing agreement with the RF experiments in NSTX. Loss predictions for the future experiment NSTX-Upgrade (NSTX-U) are also obtained and discussed.

The E–H mode transition and hysteresis in low pressure argon inductively coupled discharges are investigated using a global model and a transformer model. The total absorbed power by the plasma and the coil current are calculated as a function of the electron density at fixed RF injected power rather than fixed RF coil current as previously shown in the literature. We found that the transition corresponds to a difference of the absorbed power efficiency between E and H mode. The calculation results show the existence of an inaccessible region between E and H mode as well as a threshold coil current and a minimum absorbed power for the H mode. Hysteresis is well reproduced by this simple calculation and can be directly compared with experimental data.

Microwave discharges are widely used for generation of quasi-equilibrium and nonequilibrium plasma for different applications. Microwave plasma can be generated at pressures from 10 -5 Torr up to atmospheric pressure in the pulse and continuum wave regimes at incident powers ranged between several Watts and hundreds of kW. The plasma absorbed power can be high enough and runs up to 90% of the incident power. This paper reviews the methods of microwave plasma generation, general features of microwave plasma, and selected aspects of microwave plasma diagnostics.

Characteristics of attachment instabilities in SF6 inductively coupled plasmas are experimentally studied under different coupling intensities. Experimental results show that the instabilities only occur in H modes operating in positive feedback regions. Both the sudden mode transitions and the instabilities are influenced by the coupling intensities. With increasing absorbed power, weak and middle coupling discharges can sequently undergo sudden mode transitions and attachment instabilities. In strong coupling discharges, the sudden mode transitions disappear and only attachment instabilities exist. The strong and weak coupling discharges are the most stable and unstable, respectively.

Velocity-selective absorption by a long lifetime transition in a calcium atomic beam has been measured for two spatially separated counterpropagating laser beams. The observed variation of the absorbed power as well as of the Lamb dip depth with laser power and with velocity of the atoms is in agreement with calculations of Rabi cycles.

Several evidences, typical of a superfluorescence effect, have been obtained for the first time under continuous excitation. Emission from Er3+ in LiYF4 at 10 K is obtained at 2.72 μm with a threshold of 3 mW of absorbed power at 6470 A.

A surge in absorbed power by a heterogeneous catalyst placed in an RF field was observed at high temperatures. This phenomenon has been explained by the dielectric behaviour of the material. A transition in dielectric behaviour from low to high loss is sensitive to both temperature and chemisorbed water and will cause thermal fluctuations in the catalyst.

The electron velocity-field (v–E) characteristics of GaxIn1-xSb in the composition range 0.4≤x≤0.9 are measured by a microwave heating technique at 35 GHz at room temperature, to study the transferred electron effect at high frequency. New microwave cavity perturbation tequnique is developed to measure a small signal conductance against the absorbed power in order to obtain the v–E curve. The results indicate that all samples except one of x=0.4, show negative differential mobility characteristics above the threshold field. The threshold field increases from 430 V/cm to 1200 V/cm and the negative mobility decreases with increasing x. For x=0.4, an impact ionization prevents from mesuring a negative differential conductivity. These results suggest that a useful Ga composition range of x for transferred electron devices is between 0.55 and 0.82, and that the response time of hot electrons is not much different from that in GaAs.

Current drive by radiofrequency waves is considered for a preionization plasma. The ratio J/P of the driven current density and the absorbed power density is computed, taking into account both Coulomb and electronneutral collisions. A considerable modification of the fully ionized plasma case is found.