Engineering topics

Qin, X.

Publications and source records attributed to Qin, X..

3 records

DOE OSTI2023

Experimental Validation of a Kinetic Ballooning Mode in High-Performance High-Bootstrap Current Fraction Fusion Plasmas

We report the observation of a set of coherent high frequency electromagnetic fluctuations that leads to a turbulence induced self-regulating phenomenon in the DIII-D high bootstrap current fraction plasma. The fluctuations have frequency of 130~220kHz, the poloidal wave length and phase velocity are 16~30 m -1 and ~30 km/s, respectively in the outboard midplane with the estimated toroidal mode number n~5- 9. The fluctuations are located in the internal transport barrier (ITB) region at large radius and are experimentally validated to be kinetic ballooning modes (KBM). Furthermore, quasilinear estimation predicts the KBM to be able to drive experimental particle flux and non-negligible thermal flux, suggesting its significant role in regulating the ITB saturation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2018

Initial beam emission spectroscopy diagnostic system on HL-2A tokamak

A beam emission spectroscopy system is being developed and deployed on the HL-2A tokamak to measure local low wavenumber (k ⊥ ρ i < 1) density fluctuations by measuring the Doppler-shifted emission from a 50 kV deuterium heating neutral beam. High spatial resolution (Δr ≤ 1 cm, Δz ≤ 1.5 cm) measurements are achieved with customized in-vacuum optics. High frequency, high-gain preamplifiers sample the light intensity at a Nyquist frequency of 1 MHz and achieve a high S/N ratio via high optical throughput, low-noise preamplifiers, and high quantum efficiency photodiodes. A first set of 16 detector channels [configured in an 8 (radial) × 2 (poloidal) array] has been installed and tested at HL-2A, covering the radial range r/a = 0.8–1.1. The frequency and wavenumber spectra have been measured under different plasma conditions. Initial measurements have demonstrated the capability of measuring edge plasma density fluctuation spectra and the poloidal flow velocity fields with a high S/N ratio.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

NASA NTRS1992

Database computing in HEP

The major SSC experiments are expected to produce up to 1 Petabyte of data per year each. Once the primary reconstruction is completed by farms of inexpensive processors, I/O becomes a major factor in further analysis of the data. We believe that the application of database techniques can significantly reduce the I/O performed in these analyses. We present examples of such I/O reductions in prototypes based on relational and object-oriented databases of CDF data samples.

Day, C. T.↗