RF Sheath-Enhanced Plasma Surface Interaction Studies using Beryllium Optical Emission Spectroscopy in JET ITER-Like Wall

Conference · Sun Oct 01 00:00:00 EDT 2017

OSTI ID:1423084

Agarici, G. ^[1]; Klepper, C Christopher  ^[2]; Colas, L. ^[3]; Krivska, Alena ^[4]; Bobkov, V. ^[5]; Jacquet, P. ^[6]; Delabie, Ephrem G.  ^[2]; Giroud, C. ^[7]; Kirov, K K. ^[8]; Lasa Esquisabel, Ane  ^[2]; Lerche, E. ^[9]; Dumortier, P. ^[9]; Durodie, Frederic ^[4]

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1. Fusion for Energy (F4E), Barcelona, Spain
2. ORNL
3. French Atomic Energy Commission (CEA)
4. Ecole Royale Militaire, Brussels Belgium
5. Max-Planck-Institut fur Plasmaphysik, EURATOM Association, Garching, Germany
6. Culham Centre for Fusion Energy (CCFE), Abingdon, UK
7. EURATOM / UKAEA, UK
8. Association EURATOM-CCFE, Abingdon, UK
9. ERM-KMS, Association EURATOM-Belgian State, Brussels, Belgium

A dedicated study on JET-ILW, deploying two types of ICRH antennas and spectroscopic observation spots at two outboard, beryllium limiters, has provided insight on long-range (up to 6m) RFenhanced plasma-surface interactions (RF-PSI) due to near-antenna electric fields. To aid in the interpretation of optical emission measurements of these effects, the antenna near-fields are computed using the TOPICA code, specifically run for the ITER-like antenna (ILA); similar modelling already existed for the standard JET antennas (A2). In the experiment, both antennas were operated in current drive mode, as RF-PSI tends to be higher in this phasing and at similar power (~0.5 MW). When sweeping the edge magnetic field pitch angle, peaked RF-PSI effects, in the form of 2-4 fold increase in the local Be source,are consistently measured with the observation spots magnetically connect to regions of TOPICAL-calculated high near-fields, particularly at the near-antenna limiters. It is also found that similar RF-PSI effects are produced by the two types of antenna on similarly distant limiters. Although this mapping of calculated near-fields to enhanced RF-PSI gives only qualitative interpretion of the data, the present dataset is expected to provide a sound experimental basis for emerging RF sheath simulation model validation.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1423084
• Resource Relation: Conference: 22nd Radiofrequency Power in Plasmas Topical Conference (RFPPC 2017) - Aix-en-Provence, , France - 5/30/2017 12:00:00 AM-6/2/2017 12:00:00 AM, Aix-en-Provence, France, 5/30/2017 - 6/02/2017
• Country of Publication: United States
• Language: English