A relativistic plasma shutter technique is proposed and tested to remove the sub-100 ps pedestal of a high-intensity laser pulse. The shutter is an ultrathin foil placed before the target of interest. As the leading edge of the laser ionizes the shutter material it will expand into a relativistically underdense plasma allowing for the peak pulse to propagate through while rejecting the low inte...

The pedestal (prepulse and postpulse) associated with a chirped-pulse-amplification (CPA) laser is studied. Four components have been identified that contribute to the pedestal. Pulses are spectrally shaped by gain narrowing in a frequency-matched, regenerative amplifier, while self-phase modulation is avoided. The intensity contrast is further improved through the use of a saturable absorber, ...

Single-crystal rare-earth doped YAG fiber lasers grown by the laser-heated pedestal growth technique Report Title High concentrations of the rare-earth elements erbium, holmium and thulium have been successfully doped into single crystal (SC) yttrium aluminum garnet (YAG, Y3Al5O12) fibers by use of the laser heated pedestal growth (LHPG) method. The spontaneous emission spectra and fluorescence...

We demonstrate almost chirpand pedestal-free optical pulse compression in a nonlinear fiber Bragg grating with exponentially decreasing dispersion. The exponential dispersion profile can be well-approximated by a few gratings with different constant dispersions. The required number of sections is proportional to the compression ratio, but inversely proportional to the initial chirp value. We pr...

Quasi-periodic Pedestal Burst Instabilities (PBIs), featuring alternative turbulence suppression and bursts, have been clearly identified by various edge diagnostics during I-mode to H-mode transition in the EAST Tokamak. The radial distribution of phase perturbation caused PBI shows that is localized pedestal. Prior each PBI, a significant increase density gradient close pedestal top can be di...

In this thesis high resolution soft x-ray measurements from the Alcator C-Mod plasma edge are presented for a variety of different plasma conditions. These measurements provide radial profiles of the soft x-ray emissivity with 1.5 mm resolution or better, and temporal resolution down to 12 μs. These profiles show a distinct and very narrow pedestal shape in H-mode, indicative of the H-mode tran...

Abstract We present PEdestal Neural Network (PENN) as a machine learning model for tokamak pedestal predictions. Here, the is trained using EUROfusion JET database to predict electron temperature and density from set of global engineering plasma parameters. Results show that PENN makes accurate predictions on test database, with R 2 = 0.93 temperature, 0.91 density. To demonstrate applicability...

Our impressive sensitivity to vernier offsets as compared to resolution acuity has long inspired vision researchers to study the phenomena in great detail. In this study we use the test-pedestal framework to compare resolution and vernier acuity. In these experiments the test stimulus is the same for both tasks, only the pedestals differ. When thresholds are expressed in common units of test st...

Abstract The neutral ionisation model proposed by Groebner et al (2002 Phys. Plasmas 9 2134) to determine the plasma density profile in H-mode pedestal, is extended include charge exchange processes pedestal stimulated ideas of Mahdavi (2003 10 3984). then tested against JET data, both a ‘standalone’ version using experimental temperature profiles and also incorporating it Europed EPED. able pr...