Development of featured diagnostics — Twenty years of SUNIST (chapter 7)

Magnetically driven reciprocating probes were widely used in SUNIST. The left figure shows a radial system utilizing pulsed coils to accelerate probes up to $20 m / s$ [16], scanning the full SUNIST plasma radius within $10 m s$ . Meanwhile, the vertical launcher in the right figure employed a similar electromagnetic technique to loft a fully self-contained measurement sphere (with magnetic probes, ADC, buffer, MCU and wireless communications inside) to the central midplane. With no long supporting stalk, plasma perturbation was minimized for the free-floating probe (Fig. 17).

Figure 17, panel 1 — Fig. 17. The horizontal magnetically driven probe (left) and the vertical one (right).

Figure 17, panel 2 — Fig. 17. The horizontal magnetically driven probe (left) and the vertical one (right).

A 5-channel $105 G H z$ interferometer[17] was constructed, achieving a bandwidth up to $2 M H z$ and density resolution of $1 \times 10^{15} m^{- 2}$ . As shown, excellent agreement was obtained between density fluctuations measured by interferometry and magnetic signals, capturing events up to 100 kHz. This may be the first evidence of density fluctuation caused by Alfvénic perturbations (Fig. 18).

Figure 18, panel 1 — Fig. 18. The five channel high sensitivity interferometers (left) and the Alfvén wave density fluctuation measured (right). Reprinted from [17], with the permission of AIP Publishing.

Figure 18, panel 2 — Fig. 18. The five channel high sensitivity interferometers (left) and the Alfvén wave density fluctuation measured (right). Reprinted from [17], with the permission of AIP Publishing.