Basic principles of heterodyne techniques are introduced and the various components of a heterodyne system are summarized. Special applications in ECE, interferometry and reflectometry are discussed after introducing the diagnostic principles. Realized systems as described in the literature are briefly outlined. Ordering principles are radiometer types in the case of ECE, mixing scheme and generation and stabilization of local oscillator and intermediate frequency signals in the case of interferometry and reflectometry. Special techniques and their impact on the performance of the diagnostic instruments are discussed. Contents Introduction 1694 Components of the heterodyne receiver 1695 2.1 Heterodyne detection scheme 1696 2.1.1 Mixers 1697 2.1.2 Local oscillators 1705 2.1.3 IF chain 1706 2.2 Sensitivity 1707 2.3 Antennas and waveguides 1709 Radiometry of electron cyclotron emission 1711 3.1 Principles of ECE diagnostics 1711 3.1.1 Frequency and intensity of the emission 1711 3.

Abstract. The potential of high-resolution repeat DEMs was investigated for glaciological applications including periglacial features (e.g. rock glaciers). It was shown that glacier boundaries can be delineated using airborne LIDARDEMs as a primary data source and that information on debris cover extent could be extracted using multi-temporal DEMs. Problems and limitations are discussed, and accuracies quantified. Absolute deviations of airborne laser scanning (ALS) derived glacier boundaries from ground-truthed ones were below 4 m for 80% of the ground-truthed values. Overall, we estimated an accuracy of +/−1.5% of the glacier area for glaciers larger than 1 km 2 . The errors in the case of smaller glaciers did not exceed +/−5% of the glacier area. The use of repeat DEMs in order to obtain information on the extent, characteristics and activity of rock glaciers was investigated and discussed based on examples.

Collective scattering of gyrouon radiation and its potennal for plasma diapostics was investigated using the WFAS stellamor. The ion temperature was determined from thermal spectra in neuwd-beom-heated plasmas. The excitation of a n m w band plasma wave by a non.thermd ion component w a observed and the wave characteristics wece investigated experimentally. The results constitute an important step toward a-pmicle diagnostic via scattering of powerful microwave radiation.

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In W 7-AS the H mode has been observed for the first time in a currentless stellarator plasma. H modes are achieved with 0.4 MW electron cyclotron resonance heating at 140 GHz at high density. The H phases display all characteristics known from tokamak H modes including edge localized modes (ELMs). The achievement of the H mode in a shear-free stellarator without toroidal current has consequences on //-mode transition and ELM theories.

Radially peaked density profiles were observed in the stellarator W7-AS in discharges with small central particle sources. Particle balance analyses and density modulation experiments revealed the existence of a convective inward particle flux. The peaked density profiles appear only in discharges with flat central electron temperature profiles. In discharges with peaked temperature profiles the convective inward flux is canceled by outward directed thermodiffusion. [S0031-9007(98)08292-1] PACS numbers: 52.55. Hc, 52.25.Fi Clear evidence exists that transport of particles and energy across magnetic flux surfaces of magnetically confined high-temperature plasmas is caused by turbulent processes. This is true for most of the accessible collisionality regimes in stellarators and tokamaks [1]. Progress in recent years with the numerical simulation of turbulent transport processes allows one now to account at least in the plasma edge for the magnitude of the observed losses [2,3]. It remains, however, difficult to understand how transport can be directed opposite to the corresponding thermodynamic force [4,5], as is reported in this Letter for the particle transport in the W7-AS stellarator. Evidence is presented for the fact that a fraction of the particle transport is (inward) convected up the density gradients. Under standard discharge conditions, a radially peaked temperature profile counteracts this inward component. Only when flat temperature profiles are generated by noncentral plasma heating, does this component become visible. In the edge of stellarators and tokamaks or in the core of low density and temperature discharges, probe measurements show that the fluctuation induced transport has intermittent character. The direction of transport due to these fluctuations depends on the phase shift between density and potential fluctuations. It is observed that most of the transport is outward directed but there exists a fraction where the phase shift results in inward-directed transport [6]. The observed inward convection could be related to these events and it was observed in the H-1 Heliac that the phase shift between density and potential fluctuations can change during a discharge leading to an increase of the inward directed fraction of particle transport [7].The radial particle flux through a magnetic flux surface is governed by the continuity equation. The electron particle flux G e is given bywith n e , the electron density, and S, the sum of all particle sources and sinks. The effective plasma radius r labels the magnetic flux surfaces. In collisional transport theory, radial electron density and temperature gradients drive the particle flux, which can be written as G e 2n e √ D 11 = r n e n e 1 D 12 = r T e

Electron transport coefficients have been determined in the W7-AS stellarator. The diffusion and convection coefficients were obtained by modulating the gas feed into the plasma and by measuring the propagation of the density perturbation. The experiments were carried out at a variety of plasma densities, heating powers and magnetic fields. The results are summarized in the form of a scaling expression for the diffusion coefficient. Transient inward convection was found in the boundary plasma. This convection plays a minor role in the core plasma except with higher heating power, where outward convection was observed. The results are compared with earlier W7-AS transport results.

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