Oscilloscope

An oscilloscope (informally scope or O-scope) is a type of electronic test instrument that graphically displays varying voltages of one or more signals as a function of time. The main purpose is capture information on electrical signals for debugging, analysis, or characterization. The displayed waveform can then be analyzed for properties such as amplitude, frequency, rise time, time interval, distortion, and others. Originally, calculation of these values required manually measuring the waveform against the scales built into the screen of the instrument. Modern digital instruments may calculate and display these properties directly. Oscilloscopes are used in the sciences, engineering, biomedical, automotive and the telecommunications industry. General-purpose instruments are used for maintenance of electronic equipment and laboratory work. Special-purpose oscilloscopes may be used to analyze an automotive ignition system or to display the waveform of the heartbeat as an electroca

Stability at high performance in the MAST spherical tokamak

Olivier Sauter

The development of reliable H-modes on MAST, together with advances in heating power and a range of high spatial resolution diagnostics, has provided a platform to enable MAST to address some of the most important issues of tokamak stability. In particular the high beta potential of the spherical tokamak is highlighted with stable operation at beta(N) similar to 5-6, beta(T) similar to 16% and beta(p) up to similar to2. Magnetic diagnostic evaluation of the global beta parameters is independently confirmed by kinetic profile data. Calculations indicate that the beta(N) values are in the vicinity of no-wall stability limits. Studies of neoclassical tearing modes (NTMs) have been extended to explore their effects and develop avoidance strategies. Experiments have demonstrated that sawteeth play a strong role in triggering NTMs-by avoiding large sawteeth a much higher beta(N) value has been reached. The significance of NTMs is confirmed, with large islands observed using the 300 point Thomson scattering diagnostic, and locking of large n = 1 modes frequently leading to disruptions, which become more rapid at low q(95). The role of error fields has been explored. H-mode plasmas are also limited by edge localized modes (ELMs), with confinement degraded as the ELM frequency rises. However, in contrast to the conventional tokamak, the ELMs in high performing regimes on MAST (H-IPB98Y2 similar to 1) appear to be type III in nature. Modelling using the ELITE code, which incorporates finite n corrections, identifies instability to peeling modes, consistent with a type III interpretation. It also shows considerable scope to raise pressure gradients before ballooning type modes (perhaps associated with type I ELMs) occur. The calculations show that narrow pedestals can support much stronger pressure gradients than might be expected from simple n = infinity ballooning calculations. Finally sawteeth are shown to degrade confinement by similar to10-15% in particular cases examined. They are observed not to remove the q = 1 surface in the cases where snakes are present-various physics models of the sawteeth are now being explored. Thus research on MAST is not only demonstrating stable operation at high performance levels and developing methods to control instabilities; it is also providing detailed tests of the stability physics and models applicable to conventional tokamaks, such as ITER.

2004

Performance of Instantaneous Microwave Analysis by Parametric Channelized Receiver Through Time Domain Monitoring

Camille Sophie Brès

For many applications, ranging from commercial, surveillance, or defense, it is essential to analyze the frequency components of a captured microwave signal over a wide bandwidth in real time and with high resolution. Various photonic approaches have been proposed for the processing of wideband microwave signals in order to overcome limitations imposed by conventional electronic frequency measurements. Here, we present the performance analysis and characterization of a parametric channelized receiver with 275 MHz resolution defined by the Fabry-Perot 3 dB bandwidth and 1 GHz step. Our approach relies on the generation of high quality copies of the RF input by self-seeding wavelength multicasting in a two-pump parametric mixer. Periodic filtering using off-the-shelf elements is then performed on the multicast beam. Ease of filtering is thus achieved by relying on frequency nondegeneracy of the newly generated copies. In this paper, instantaneous analysis of the incoming microwave signal is demonstrated by simultaneous monitoring five of the generated parametric copies while transmitting a frequency-hopping pattern. Operating margins in terms of optical and microwave powers are studied using the five-channel data simultaneously collected on a real-time oscilloscope. Dynamic range adjustments through optical power tuning of the input signal seed are demonstrated. Finally, the effects of frequency mapping detuning are observed to determine optimal operating conditions.

Ieee-Inst Electrical Electronics Engineers Inc2012

Stability at high performance in the MAST spherical tokamak

Olivier Sauter

2004

Stability at high performance in the MAST spherical tokamak

Performance of Instantaneous Microwave Analysis by Parametric Channelized Receiver Through Time Domain Monitoring

Characterization of parametric RF channelized receiver through time domain monitoring

Stability at high performance in the MAST spherical tokamak

Characterization of parametric RF channelized receiver through time domain monitoring

Performance of Instantaneous Microwave Analysis by Parametric Channelized Receiver Through Time Domain Monitoring