Dmitriĭ Nikolaevich Nasledov (obituary)

Abstract

The results of recent experimental and theoretical studies concerning the effects of plasma shape and current and pressure profiles on edge instabilities in DIII-D are presented. Magnetic oscillations with toroidal mode number n ≈ 2-9 and a fast growth time γ −1 = 20-150 µs are often observed prior to the first giant type I ELM in discharges with moderate squareness. High n ideal second ballooning stability access encourages edge instabilities by facilitating the buildup of the edge pressure gradient and bootstrap current density, which destabilize the intermediate to low n modes. Analysis suggests that discharges with large edge pressure gradient and bootstrap current density are more unstable to n > 1 modes. Calculations and experimental results show that ELM amplitude and frequency can be varied by controlling access to the second ballooning stability regime at the edge through variation of the squareness of the discharge shape. A new method is proposed to control edge instabilities by reducing access to the second ballooning stability regime at the edge using high order local perturbation of the plasma shape in the outboard bad curvature region.

Spectrum, temporal structure, and fluctuations in a high-gain free-electron laser starting from noise

“…For small undulator lengths we have found that the spectral bandwidth shrinks as 1/N, in agreement with the undulator radiation spectrum width [13]. In the highgain region the envelope reaches the well known bandwidth [3,5] Ak/k, = 2p, i.e.…”

Angular distribution of nonlinear harmonic generation in helical undulators: A comparison between experiments and theory

“…and N w ≫ 1, major simplifications arise because fast oscillating terms in powers of exp[ik w z ′ ], which explicitly appear in Eq. (6) after substituting the trajectory [24], effectively average to zero after integration in dz ′ . To complete the resonance approximation, we further select frequencies such that…”

Relationship Between Spatial Coherence of Synchrotron Radiation and Emittance

“…Before the calculation, we will investigate a limiting case of the ®eld pattern in (46). The far-®eld pattern of synchrotron radiation from the undulator is approximately written as (Alferov et al, 1973(Alferov et al, , 1974Kincaid, 1977) ExY L 9 sinN%2xaN sin%2x…”