2025 – Cryogenic Shell Pellets for Inside-Out Mitigation

Cryogenic Shell Pellets for Inside-Out Mitigation

2025 Research Campaign, Disruption Mitigation

Purpose of Experiment

The purpose of this experiment is to experimentally quantify the use of cryogenic shell pellets (CSP) for disruption mitigation. This novel mitigation technique aims to release radiating impurities into the plasma core by encapsulating them within a minimally radiating shell that burns through as it travels deeper into the plasma. Simulations of this mitigation technique show favorable metrics for the avoidance of runaway electron mitigation such as a slow thermal quench, high radiation fraction of the plasma’s stored energy, and MHD activity continuing through the first half of the current quench [1]. This experiment would be the first demonstration of CSP and will be compared to existing SPI and massive gas injection (MGI) datasets on DIII-D.

Experimental Approach

1. Establish reference shot. Fire CSP (composition 1) at 1700 ms with the PCS. 2 Shots 1.1. Examples based on beam availability (all are similar targets): · Target 1 (5 beams, no 210): 172264, 30L, 30R, 33L, 33R, 15R · Target 2 (6 beams, co-210): 195224, 30L, 33R, 15L, 15R, 21L, 21R · Target 3 (5 beams, co-210): 180013, 30L, 33L, 33R, 15R, 21L 2. Repeat CSP (composition 1) 2-4 Shots 2.1. Get good Thomson burst and fastcamera data during injection. 3. Pellet composition endpoint comparison using the same barrel 4 Shots 3.1. Pure Ne pellet (+ thin layer of D2 grease) 3.2. Mixed D2/Ne pellet (similar quantities at CSP) 3.3. Pure D2 pellet At this point we have met our main goal – following points desirable for a more complete measurement. 4. Change CSP speed, injection timing 4 Shots 4.1. Fire at 500 m/s 4.2. Change injection timing to 1900 ms 4.2.1. 300 m/s pellet 4.2.2. 500 m/s pellet 5. Change Ne content within core (composition 2) 4 Shots 6. Fill in gaps Remaining Total: 20+ shots

Interested in a behind-the-scenes look at DIII-D? Join us for a virtual tour during Fusion Energy Week (tour times: May 7 at 10am PDT, May 8 at 4pm PDT)! Sign up for a tour here.

X