On the performance of JET hybrid plasmas, our latest contribution published in Nuclear Fusion

The Joint European Torus (JET) – Courtesy of EUROfusion

The paper entitled “Modelling of JET hybrid plasmas with emphasis on performance of combined ICRF and NBI heating” has been published by Nuclear Fusion. It advances our understanding of the optimisation of fusion performance of the recent Joint European Torus (JET) hybrid plasmas. The hybrid scenario is an advanced regime of tokamak plasma operation expected to be applied in ITER. It is characterized by a low plasma current Ip which allows operation at a high normalised beta as well as a safety factor at the plasma centre greater than 1 which is beneficial from the plasma stability point of view.

The paper focuses on the impact of neutral beam injection (NBI) and specially ion cyclotron resonance frequency (ICRF) heating on the neutron production rate. The main scheme studied is minority hydrogen (H) in a deuterium (D) plasma with D beams. The modelling takes into account the synergy between ICRF and NBI heating through the second harmonic cyclotron resonance of D beam ions which allows us to assess its impact on the neutron rate RNT. Apart from the D scenario, the deuterium-tritium (DT) scenario is also assessed through an extrapolation  of D high-performance hybrid discharges. These results are relevant for the forthcoming DTE2 campaign at JET where one of the goals is to achieve the highest possible fusion performance for a duration of more than 5 s.

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Evidence of generation of non-inductive toroidal plasma current above density limit

Alcator C-Mod (Photo: Courtesy of MIT)

One of the key requirements to achieve steady-state power production in a fusion reactor based on the so-called tokamak configuration is to generate non-inductive toroidal plasma current in an efficient way. A recent paper published in Physical Review Letters entitled “Observation of Efficient Lower Hybrid Current Drive at High Density in Diverted Plasmas on the Alcator C-Mod Tokamak” reports on the use of lower hybrid current drive (LHCD) as an efficient mean to obtain non-inductive plasma current at high plasma densities in a diverted tokamak configuration such as Alcator C-Mod.

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New cloud-based computing platform for fusion research

Since June Culham Centre for Fusion Energy (CCFE) provides a new facility to fusion scientists, named the CUMULUS Modular Data Centre. The centre contains a new cloud-based computing platform that promises to process scientific data quicker, cheaper and more accurately than ever before.

Scientific computing is an essential technology for assimilating and understanding the large quantities of data that are now commonplace in the fusion community, as well as carrying out complex predictive simulations of tokamak plasmas. To give an idea of where we are heading, the next-generation fusion experiment ITER will generate 2 petabytes of raw data each day (2,000 trillion bytes), more than JET has produced in its entire 34-year history!

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Visit to JET

JET – Aerial view. Photo: EFDA-JET

During the two-week Culham Plasma Physics Summer School organized at Culham Science Center, UK, one of the most expected moments is the visit to Joint European Torus (JET). JET is the world’s largest operational magnetically confined plasma physics experiment. It is based on a tokamak design and is the direct predecessor to ITER, which should be operative in 2025.

JET runs only during some seconds at the time and thereafter it must rest about 20min before a new run. In a good operative day, about 20 runs are carried out. These runs are made for experimentation and no electricity is produced. However, a lot of energy is required (about a 1% of the total energy used at a given moment in the UK). This is why a direct phone line from London to the JET control room can ring at any moment, kindly requesting to stop experiments.

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Group member defends his thesis

Our Fusion group member Marc Fuster has successfully presented his final Bachelor thesis in Physics entitled “Application of the Edge-Based Finite Element Method for fusion plasma simulation” based on the work he has been carrying out since last August in our group under supervision of Dr Shimpei Futatani. The defense took place at the Faculty of Sciences of Universitat Autònoma de Barcelona, Spain.

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