Fast Reciprocating Probe System on the HL-2A Tokamak

A refined reciprocating probe system was installed on the midplane of HL-2A tokamak. The system is developed in collaboration with the Institute of Scientific Instrument, Chinese Academy of Science in Shenyang.The system has been used to measure edge density, temperature, potential and their fluctuation profiles with 8 cm scan from scrapeoff layer to plasma boundary. The velocity of the reciprocating stroke is designed by 1 m ·s^-1.

Edge Plasma Profiles Measured by Fast Reciprocating Probes System on HL-2A Tokamak

Fast reciprocating probe systems （ FRPS ） are widely used in some tokamaks, such as JT- 60 U, TEXT and DIlI-D. The parameters with high temporal-spatial resolution are measured for boundary plasmas using these systems. The FRPS on HL-2A is developed, which is composed of transmission bar, digital grating displacement system, electromagnetic valves, stepping motor and so on. The high-pressure gas from the electromagnetic valves controlled by trigger signals provides the power to drive the transmission bar forward or backward. Reciprocating distance is 8 cm with the maximum speed of 1.5 m·s^-1.

Modification of Boundary Parameters and Fluctuations by IBW and LHCD in the HT-7 Tokamak

Measurements of boundary parameters and their fluctuations have been performed in ohmic (OH) plasma and Ion Bernstein Wave (IBW) and Lower Hybrid Current Drive (LHCD) enhanced confinement plasma using a pneumatically driven Langmuir probe array on HT-7 toka-mak. In the enhanced confinement plasma, the gradients of electron density and temperature become higher and a transport barrier comes into being in the vicinity of the limiter. The boundary potential shows a clear modification in the same region. The fluctuation levels are significantly depressed and the coherences between fluctuations are reduced evidently in the enhanced plasma. Meanwhile, we obtained the spectral features and the poloidal phase velocity of fluctuations using a two-point correlation technique and found obvious modifications of the turbulence and the poloidal flow. The results suggest that the improved confinement in the IBW and LHCD enhanced plasma is at least partially due to the modification of the boundary parameters and the suppression of the boundary fluctuations and fluctuation induced fluxes.

A Method for the Determination of Turbulence Intensity by Means of a Fast Response Pressure Probe and its Application in a LP Turbine

This paper describes the measurements and the post-processing procedure adopted for the determination of the turbulence intensity in a low pressure turbine (LPT) by means of a single sensor fast response aerodynamic pressure probe. The rig was designed in cooperation with MTU Aero Engines and considerable efforts were put into the adjustment of all relevant model parameters. Blade count ratio, airfoil aspect ratio, reduced massflow, reduced speed, inlet turbulence intensity and Reynolds numbers were chosen to reproduce the full scale LP turbine. Measurements were performed adopting a phase-locked acquisition technique in order to provide the time resolved flow field downstream of the turbine rotor. The total pressure random fluctuations are obtained by selectively filtering, in the frequency domain, the deterministic unsteadiness due to the rotor blades and coherent structures. The turbulence intensity is derived from the inverse Fourier transform and the correlations between total pressure and velocity fluctuations. The determination of the turbulence intensity allows the discussion of the interaction processes between the stator and rotor for engine-representative operating conditions of the turbine.