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Exploring Power Deposition and Heating Efficiency in HHFW Experiments

This document outlines the discussion points from the HHFW group meeting on January 23, 2003, focusing on novel heating techniques in plasma experiments. Key issues include power deposition characteristics as RF and plasma parameters are adjusted, such as phasing and density. The planned HHFW CD experiment will test various phasings and plasma conditions to assess heating efficiency and core power deposition. Additional topics include modulation experiments, ion temperature measurements, and configurations necessary for effective experimentation. The post-meeting action plan indicates a highly structured approach to address these problems.

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Exploring Power Deposition and Heating Efficiency in HHFW Experiments

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  1. XP – Electron Heating with HHFW David Swain, Randy Wilson and the usual suspects HHFW Group Meeting Jan 23, 2003

  2. Heating XP ideas • Issues: • Where is the power deposited? • How does it change as rf parameters (e.g., phasing) are changed? • How does it change as plasma parameters (e.g., ne, Ip) are changed? • Efficiency? How much winds up in the core? • HHFW CD experiment will carry out experiments at different phasings: • ± 90°, ±30°, 00ππ00, (0π0π0π?) • Mostly at low ne (≤ 2e19?) and low Ip (≤ 500 kA?) • For heating: • Look at power deposition on these shots FIRST • Expand range in parameter space (higher ne, Ip) during time allocated to this XP (e.g., ne ≥ 4e19, Ip ≈ 1 MA); look at heating for different rf phases

  3. Things probably NOT covered in this XP • Study of H-mode threshold or operation • For high power may be difficult to avoid • Run in He to avoid H-mode? • ITB formation • Run time for this XP is 1 day, plus 1 day later. • Don’t have time to study these topics.

  4. Questions • Power deposition measurements: • Can we get power deposition from USXR array data? Stutman says yes. • How about the new Italian X-ray diagnostic-GEMS? Stutman says April (?) • TS? • Other ideas? • Modulation experiments? • Amount of modulation (20%, 50%, 100%?) • Frequency of modulation? (sources good to “a few kHz) • Ion temperature measurements: • How necessary are they? • Argon Ti? • Beam blip? • Power • Scan needed? • What power to use for experiments?

  5. Other questions • Plasma configuration: • LSN? • DN? • Inner-wall limited? • Need to do same as HHFW CD XP to use their data. • What else?

  6. Strawman run plan • First day (in Feb). • Initial setup: • He, 0.45T, 900 kA, ~4e19, LSN • Phasing -90° • P = 2 – 3 MW (want reproducible shots) • Modulate rf: ~30% square-wave with ~10-ms period (rough guess) • Need USXR set for Te measurements, • Second day (in April?) will depend on results from first day.

  7. Shot list for first day of experiment • Setup initial conditions, get 2 shots alike, check x-ray signals 5 shots Enough power to change Te, modulation to get good S/N on USXR • Change phase to +90°, get 2 shots alike 3 shots • Change phase to -30°, get 2 shots alike 4 shots • Change phase to +30°, get 2 shots alike 4 shots • Change Ip to ~ 400 kA, repeat above. • It would be very helpful to have a couple of shots before this day to check out modulation and X-ray capability; otherwise will need Plan B.

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