Xp to examine the front end of long pulse discharges
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XP to Examine the Front-end of Long Pulse Discharges. C. Kessel ISD, 3/24/2006. T e and T i much higher in “late heating” (109063,109070) than in “early heating H-mode” (112546,116313). Confinement regime for these plasmas is significantly different, is reverse shear causing this?.

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XP to Examine the Front-end of Long Pulse Discharges

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Xp to examine the front end of long pulse discharges

XP to Examine the Front-end of Long Pulse Discharges

C. Kessel

ISD, 3/24/2006


Xp to examine the front end of long pulse discharges

Te and Ti much higher in “late heating” (109063,109070) than in “early heating H-mode” (112546,116313)

Confinement regime for these plasmas is significantly different, is reverse shear causing this?

Ti ≈ Te

Ti ≈ 1.7 x Te

Early heating

Late heating


Xp to examine the front end of long pulse discharges

Simulations Point to NBI Absorbed Power at H-mode Onset for Different E Regimes

109070: H-mode transition occurs at 200 ms, when Ip = 800 kA

NBI power injected at this time is well confined

This generates RS in q-profile that persists for the discharge

---> Higher Te,I ---> shorter tflattop

116313: H-mode transition occurs at 85 ms, when IP = 450 kA

NBI power injected at this time is poorly confined

This amplifies RS in q-profile, but this does not persist

---> Lower Te,i ---> longer tflattop

H-mode onset

H-mode onset

Optimize plasma formation for confinement and MHD stability

MSE confirms this


Run plan

Run Plan

  • Reference discharges

    • 109070 (Ip = 800 kA, BT = 0.5 T,  = 2.0, tNB = 100, 200, 250 m)

    • 116313 (Ip = 750 kA, BT = 0.45 T,  = 2.3, tNB = 60, 100, 175 ms)

  • Reproduce 109070 in present machine conditions (Li, shape, Ip and BT) ---> 3 shots

    • Move 1st NB source back in time to 80 and 60 ms leaving others fixed (at 200 and 250 ms) ---> 3 shots

    • Move 2nd NB source back in time to 175, 150, 125 ms leaving others fixed (at 100 ms and 250 ms) ---> 4 shots

    • With 1st NB source at 100 ms, 2nd NB source at 125 ms, and move 3rd NB source back to 200 ms ---> 2 shots

    • With 1st NB source at 60 ms, 2nd NB source at 100 ms, and move 3rd NB source back to 175 ms ---> 2 shots

  • Reproduce 116313 in present machine conditions (Li) ---> 3 shots

    • Move 3rd NB source forward in time to 200, 225 and 250 ms leaving others fixed (at 60 and 100 ms) ---> 4 shots

    • With 3rd NB source at 250 ms, move 2nd NB source forward in time to 125, 150 and 200 ms, leaving other fixed (at 60 ms) ---> 4 shots

    • With 3rd NB source at 250 ms, 2nd NB source at 200 ms, move 1st NB source forward in time to 80 and 100 ms ---> 3 shots

  • Variations to produce more reliable plasmas; dIp/dt, gas, Li


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