A hybrid digital–analog long pulse integrator

Abstract

A digital–analog integrator has been developed for use with inductive magnetic sensors in long-pulse tokamaks. Continuous compensation of input offsets is accomplished by alternating analog-to-digital convertor samples from the sensor and a dummy load, while a RC network provides passive integration between samples. Typically a sampling rate of 10 kHz is used. In operational tests on the DIII-D tokamak, digital and analog integration of tokamak data show good agreement. The output drift error during a 1200 s integration interval corresponds to a few percent of the anticipated signal for poloidal field probes in International Thermonuclear Experimental Reactor, and bench tests suggest that the error can be reduced further.

Conceptual architecture of the plant system controller for the magnetics diagnostic of the ITER tokamak

“…This integration can be performed using analogue integrators [7], digital integrators [8] or hybrid integrators [9]. Each of these type of solutions have particular implementation issues but they all share a common challenge related to the variation of the integrated drift over time, which translates into an increased error in the flux measurement.…”

Drift-free magnetic equilibrium reconstruction using the response to plasma position modulation

“…Two main sources of error have been identified: the drift of electronic integrators, since the field and flux are the time-integral of the inductive magnetic sensor output signals, and a wide diversity of radiation induced effects which induce electromotive forces in the cables [1][2][3][4][5][6]. Significant progress has been made on electronic integrators which now exhibit acceptable drifts for the duration of the ITER plasma discharges [7][8][9][10][11]. Nevertheless, the radiation induced effects which are negligible in present day machines must be assessed and taken into account for ITER because they can lead to significant errors after hundreds of seconds of plasma.…”

A multi-channel real-time digital integrator for magnetic diagnostics in HL-2A tokamak

“…Owing to the limitations of analog integration, integrators using digital techniques gain their popularity [7][8][9][10][11][12]. The principle of digital integration is to convert the analog signals into discrete digital signals by ADCs and accomplish numerical integration using digital processors and integration algorithms.…”