Analysis of the L–H and H–L transition power thresholds (Pth) and pedestal parameters are presented for the mega ampere spherical tokamak (MAST). The dependencies of Pth on the average, core plasma electron density, X-point height, and plasma current are described. Increasing X-point distance from the divertor floor over 10–12 cm is found to increase Pth by a factor of three, while X-point heights greater than this have no further influence. The X-point height dependence of Pth is also observed to be sensitive to the plasma current. An Ip decrease from 0.77 MA to 0.65 MA, is observed to lower Pth by a factor of three across the X-point height scan and increases the maximum X-point height at which Pth stops increasing by 3 cm. Finally, a comparison of the experimental results with the predictions by the finite beta drift wave model is made, which provides a reasonable condition for the transition into and out of the H-mode.

We demonstrate a new, to the best of our knowledge, method of generating mid-infrared pulses by difference frequency mixing the Stokes pulse generated by four-wave mixing in a photonic crystal fiber with the remaining pump pulse. The Stokes pulses generated by four-wave mixing are inherently overlapped temporally and spatially with the pump pulse at the output of the fiber. Focusing this output into a nonlinear crystal phase matched for difference frequency generation between the pump and Stokes pulses results in a simple method of generating mid-infrared pulses. With a pump source at 1.064 µm, and a photonic crystal fiber engineered to generate Stokes pulses at approximately 1.65 µm, we generate 160 mW of mid-infrared light at approximately 3 µm through difference frequency generation.

We report a seeded optical parametric generator (OPG) producing tunable radiation from 4.2-4.6 µm. The seeded OPG employs a 13 mm long CdSiP 2 (CSP) crystal cut for non-critical phasematching, pumped by a nanosecond pulsed, MHz repetition rate Raman fiber amplifier system at 1.24 µm. A filtered, continuouswave fiber supercontinuum source at 1.72 µm is used as the seed. The source generates up to 0.25 W of MIR idler power with a total pump conversion of 42% (combined signal and idler).

We report a single-cell level resolution (≤10 µm), laser desorption-based mass spectrometry imaging platform. An optical parametric amplifier is used to generate ∼100 ps, 200 nJ pulses at around 3 µm with a maximum repetition rate of 500 kHz. The pulses are tightly focussed on to fresh frozen animal tissue samples with a thickness of 10 µm. Small volumes of tissue are readily ablated by the laser and are subsequently chemically analyzed using a Rapid Evaporative Ionization Mass Spectrometry (REIMS) source installed on a time of flight mass analyzer. Raster scanning the samples through the laser focus enables the acquisition of mass spectrometry data which can be processed into images with pixel size 10 µm without oversampling, corresponding to cellular level resolution.

We demonstrate a nanosecond-pulsed 743 nm source by second harmonic generation of a cascaded phosphosilicate Raman fiber amplifier operating at 1485 nm. The source emits >1 W of 743 nm average power at a 5 MHz repetition rate.