52 research outputs found
Experimental investigation of an atmospheric photoconductively switched high-voltage spark gap
We report on the experimental investigation of the photoconductively switched gas-filled spark gap. When the laser intensity of a femtosecond laser is high enough (around 1018 Wm-2), a plasma can be created that spans the complete distance between the electrodes. The gas-filled spark gap is then closed on a femtosecond timescale, similar to photoconductive switching of a semiconductor switch. Stochastic breakdown processes, such as avalanche and streamer formation that cause the breakdown in laser triggered spark gaps, are passed over, which results in faster risetime and less jitter. Measurements of the switched pulses as a function of laser energy were performed in a 1 mm gap at an applied voltage of 4.5 kV. A clear transition from triggering to switching was measured with increased laser energy. Measurements of the output pulses with the gap filled with nitrogen at 1 atm showed results very similar to measurements in air in the same gap. In the switching regime, the amplitude of the switched pulse did not depend strongly on the laser energy. Measurements at lower applied voltages but with the same gap distance showed that it was possible to switch voltages as low as 10% of the self-breakdown voltage. At low applied voltages, a significant difference between the applied voltage and the output voltage is measured. A possible explanation is given based on the dynamic behavior of the laser created plasma. The measured rise time and jitter of the switched pulses were both below the resolution of the measurement equipment, i.e., better than 100 ps and 15 ps, respectively
Data and supplemental material of the paper \u201cEffectiveness of digital-based interventions for children with mathematical learning difficulties: A meta-analysis\u201d
Data and supplement material of the article \u201cEffectiveness of digital-based interventions for children with mathematical learning difficulties: A meta-analysis\u201d (Benavides-Varela et al.) [1] are presented. Data were collected from studies included in the meta-analysis to evaluate the effects of digital-based interventions for children with mathematical learning difficulties compared to control conditions in group-designed randomized controlled trials. Literature search, inclusion criteria and coding procedure are described. PRISMA flow-chart is reported to summarize the literature search and coding of all the relevant characteristics of the primary studies is made available. This allows other researchers to easily access to the information needed to evaluate the studies and to use these data in future meta-analyses. However, researchers are highly recommended to refer to the original papers in order to check studies suitability to their own criteria. Moreover, in the supplemental material all the information needed to reproduce the meta-analysis results is reported together with the R code syntax. Data and supplemental material are available online (https://osf.io/ajdnv/)
- …