TFTR neutral beam injected power measurement

Abstract

Energy flow within TFTR neutral beamlines is measured with a waterflow calorimetry system capable of simultaneously measuring the energy deposited within four heating beamHnes (three ion sources each), or of measuring the energy deposited in a separate neutral beam test stand. Of the energy extracted from the ion source on the well-instrumented test stand, 99.5 ± 3.5% can be accounted for. When the ion deflection magnet is energized, however, 6.5% of the extracted energy is lost. This loss is attributed to a spray of devious particles onto unmonitored surfaces. A 30% discrepancy is also observed between energy measurements on the internal beamline calorimeter and energy measurements on a calorimeter located in the test stand target chamber. Particle reflection from the fiat piate calorimeter in the target chamber, which the incident beam strikes at a near-grazing angle of 12°, is the primary loss of this energy. A slight improvement in energy accountability is observed as the beam pulse length is increased. This improvement is attributed to systematic error in the sensitivity of the energy measurement to small fluctuations in the supply water temperature. An overall accuracy of 15 % is estimated for the total power injected into TFTR. Contributions to this error are uncertainties in the beam neutralization efficiency, reionization and beam scrape-off in the drift duct, and fluctuations in the temperature of the supply water.

Measurement of HL-2A NBI Beam Profile and Beam Power

“…Energetic neutral beam injection (NBI) is an effective method to heat the plasma in fusion devices [1,2] . High power NBI systems were built up in large tokamaks and stellarators.…”

Empirical Scaling Laws of Neutral Beam Injection Power in HL-2A Tokamak

“…[5] Thermocouples are also arranged on downstream components, and their measurement error is about 5%. Energy intercepted on NBI components can be obtained by measuring the energy taken out by the cooling water [6] or integrating beam power density distribution. Beam optical performance can be acquired with the data processing programs by the multi-Gauss function fitting of the maximum temperature rise from thermocouples on the calorimeter target in the injector.…”

Temporal behavior of neutral particle fluxes in TFTR (Tokamak Fusion Test Reactor) neutral beam injectors

“…Waterflow calorimetry was used to measure the energy deposited on the full-and half-energy ion dumps, the neutralizer and collimators (in one combined water circuit), and the target chamber calorimeter. 15 Beam composition (i.e., the relative proportions of the extracted D + , D 2 + , and D 3 + ) was determined using a variety of techniques," but for this study results from Doppler-shift spectroscopy of the light emitted by the beam in the neutralizer were used. 16 Beam profiles and divergence angles were derived from least square fits to data from thermocouples embedded in the calorimeter.…”