High-beta Experiment on 15.4.2002 Objective: Combination high-b (8 NBI-sources) with OXB (+ Radialinjector?) - higher power, temperature --> optimum B lower --> beta higher !? 1. Reproduce reference discharge at B = -1.25 T: #54867 (900 MHz, iota=0.48, Bz = 260 G, Icc = -2.5 kA, 8 NBI sources) 2. Reduce field to B = -1.1 T: (reproduce #54870, but switch off NBI at t = 0.55 s) 3. Switch 3 NBI injectors off at t = 0.4 s and replace NBI heating power by ECRH (establish 4th harm. OXB heating in time interval 0.4...0.55 s, optimize launch angle) 4. Apply OXB heating on top of 8 NBI injector discharge (t = 0.35...0.5 s) 5. Repeat 3.+4. for different fields (B = -1.0 T, -0.9 T ?) 6. Radial injector on top of 8 NBI injector discharge (t = 0.4...0.45 s) 7. Radial injector on top of 8 NBI + OXB discharge

Reproduction of Reference #54867 B = 1. 25 T, Bz = 260 G, iota = 0 Reproduction of Reference #54867 B = 1.25 T, Bz = 260 G, iota = 0.48, 8 NBI sources

Transition to B = 1. 1 T, Reproduction of Reference #54870 B = 1 Transition to B = 1.1 T, Reproduction of Reference #54870 B = 1.1 T, Bz = 220 G, iota = 0.48, 8 NBI sources

Assessment of O-X-B heating efficiency at B = -1 Assessment of O-X-B heating efficiency at B = -1.1 T Replacement of NBI power by OXB - 3 Gyrotrons sequentially and stacked -

Optimization of O-X-B heating profile by B-scan (1.15...1.0 T)

O-X-B heating in case of different NBI heating powers (B = -1.1 T)

Optimization of O-X-B heating efficiency by density scan

Soft X-ray measurements show effect of O-X-B heating

O-X-B heating at lower field ? (0.9 T) - density too low for OXB ! -

Weiteres Vorgehen Detail... Bild 1. D -> D Injektion (ist Heizleistung grösser? confinement besser ? Strahlung anders ?) auch für die Ermittlung des schnellen-Ionen-betas über Neutronenfluss wichtig. NBI-Schaltexperimente ---> NBI Heizleistung (rel.) aus n-Fluss, B-Abhängigkeit !? 2. Fortsetzung Hoch-beta Gleichgewichte mit signifikanten Strömen Ausheilen des m=2 Moden induzierten Kollapses bei iota = 1/2 durch Gaspuff, Dichte-Variation an der Tearing-Moden Stabilitätsgrenze (Murakami-Limit ?) 3. Hoch-beta bei iota = 5/8 kombiniert mit negativen Stromtrieb Tearing Moden bei umgekehrtem Shear ? 4. Hoch-beta in Spiegelkonfigurationen. von der MHD können veränderte Stabilitätsgrenzen erwartet werden. Heizeffizienz ? 5. dynamische Bz Programmierung zur Verbesserung des Plasmastarts (während Energieaufbaus, Bz-Rampe von -100 G auf -250 G bei -1.25 T-Bestfall) Dies ist evtl. zur Zündung bei abgesenkten Feld notwendig ! 6. Hoch-beta bei iota ≤ 0.25 : --> Shafranov-Shift, Gleichgewichts-beta-Limit ? Detail... Bild

High-beta with D -> D NBI Aims of the D->D experiments April 22 - 29: - Compare heating effic., confinement and radiation with H->H, extension of operational regime ? - MHD, fast particle confinement, thresholds for confinement transitions ? 1. Reproduce reference discharge at B =-1.25 T: #54867 (900 MHz, iota=0.48, Bz =260 G, Icc = -2.5 kA, 8 NBI sources, <b>≈2.7%) 2. Density scan (IC threshold ? MHD ? optimum confinement ?) 3. B scan (1.25->0.7 T) heating efficiency ? confinement ? optimum beta ? fast particle confin. ? a.) 8 NBI sources (compare with H->H case #54867, 70, 76, 80, 81, 82) b.) 4 unmodulated NBI s. + 2 mod. s. (0.18...0.35s) + 2 mod. radial Inj. (0.35...0.45 s) compare scaling of Wdia , b , n-flux with B and PNBI , assess scaling of prompt fast ion losses 4. NBI-Power scan with adjusted Bz , switch from 8->6, 7->5, 6->4, 5->3 NBI sources (compare with H->H case #54900, 02, 07, 08,10) steps in neutron flux --> heating efficieny, fast ion confinement 5. Repeat maximum beta cases #51755 (=#54022) at iota=0.52, B=-0.9 T, <b>≈3.1% with D->D 6. Density scan at 2...3 different B (iota = 0.48) with 4 NBI sources (until 0.45 s) + „NBI blips“ (2 sources 0.35...0.38 s + 2 radial injector sources 0.41...0.43 s) variation of slowing-down time --> fast ion confin. from neutron flux, diffusive-prompt losses

Predicted NBI Heating Efficiency and Heating Power Profiles

Dependence of D-D Neutron Flux on Temperature back