TRANSP for core particle transport studies

M. Maslov

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ITER L-H transition at full field DT plasma is not robust!

At L-H transition density increases, PLH increases, Prad increases and therefore Ploss goes down -> going back to L mode, unless PDT increase after L->H will compensate change in Prad and PLHEvolution of core Te and ne at L-H transition is important, since it determines evolution of Prad and PDT and can make difference between reaching Q=10 burning plasma or falling back to L-mode

Evolution of ne – particle transport, still not very well modelled! (even in the core)

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Few years ago it was noticed that on JET at L-H transition a hollow density profile is formed transiently as edge density is rising much quicker than the core.

Ref: A Loarte et al “Plasma density and temperature evolution following the H-mode transition at JET and implications for ITER”, NF 2013

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• Slow evolution of hollow density profile observed on JET in high current baseline scenarios. After several -s typically terminated by a sawtooth

• Provisionally in agreement with GK simulations Paper on pinboard: B.Baiocchi et al

• Evolution is dominated by NBI core particle fuelling, i.e. if we use sourceless heating (like ICRH) and plasma w/o sawteeth – evolution could take MUCH longer (whole pulse duration?)

Slow evolution is benefitial in ITER scenario (Pbrems would increase slower than PDT, plus tungsten accumulation reduced until PDT ramped to full)BUT evolution must not be too slow! PDT=max at high core density so that point must be eventually reached to achieve target Q=10

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Why TRANSP?Experiment proposed on JET to study particle transport at transition from hollow to “normal” density profile and validate first principle models (ITPA high priority)

TRANSP is needed to interpret experimental data -> calculate turbulent particle fluxes (distinguish from NBI deposited) and heat diffusivity at these conditions. Processes are transient so time evolution is important. For different cases empirical dependencies on plasma parameters will be derived and then compared with gyrokinetic models

PLAN

- Experiments to be approved, call for participation (February-March?)- “Practice” run #79676 (best example in C-wall we have)- Analysis of experiments parasitically – various pellet fuelled discharges- Dedicated experiments if time is given (pellet at L-H transition to magnify the hollowness)- If I’ll not manage to do TRANSP analysis myself – help from the experts (YOU!) will be

needed.