Continuous-wave laser utilizingF₂⁺:O^2–color centers in an NaCl:OH crystal tunable in the 1.42–1.78 μm range

Abstract

In equatorial single null diverted discharges in TEXT-Upgrade, up-down asymmetries have been noted, the sign and magnitude of which depend on plasma conditions such as electron density and X point position. Geometrical effects do not play a role in these plasmas, which are topologically up-down symmetric, so the asymmetry must come from physical driving mechanisms. Several such mechanisms will be investigated, both computationally and experimentally, and compared with data from tokamak discharges. An analysis is included of the E × B, diamagnetic and rT × B drifts as well as plasma rotation. The B2-EIRENE plasma simulation code is used to evaluate the respective influences of the rT × B driving terms. Scans of the X point position relative to the divertor plates and of the electron density are performed. The X point is brought in all the way to the divertor plates so as to assess the importance of the private region in the drift flow patterns and to break the flow loops. The low recycling regime typical of TEXT-Upgrade single null plasmas allows separation and identification of the influence of individual flows. It is concluded that E × B drift is the dominant effect and that it qualitatively explains the reported behaviour. * Current affiliation: Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA. the ∇T ×B associated flows. Mathematically, E ×B drift motion can be expressed as v E = E × B/B 2 . The diamagnetic velocity is

Infrared-induced bleaching and `F-light' regeneration of laser-active centres in

“…This new centre shows better thermal stability, but, in spite of the anchoring impurity, its laser emission unfortunately still suffers from fading. In NaCl at 77 K, stable laser operation is achieved only when an UV (Pinto et al 1986, Matts et al 1990 or green (German and Pollock 1987, Kurobori et al 1989, Carrig and Pollock 1991 light is focused on the active crystal, simultaneously with the pumping light which excites the 1sσ g → 2pσ u transition (see figure 1(a)). This infrared transition appears in absorption at 77 K at around 1.05 µm for the (a) variety and 1.08 µm for the (b) variety of (F +…”