Tritium distributions on W-coated divertor tiles used in the third JET ITER-like wall campaign

Tritium (T) distributions on tungsten (W)-coated plasma-facing tiles used in the third ITER-like wall campaign (2015-2016) of the Joint European Torus (JET) were examined by means of an imaging plate technique and beta-ray induced x-ray spectrometry, and they were compared with the distributions after the second (2013-2014) campaign. Strong enrichment of T in beryllium (Be) deposition layers was observed after the second campaign. In contrast, T distributions after the third campaign was more uniform though Be deposition layers were visually recognized. The one of the possible explanations is enhanced desorption of T from Be deposition layers due to higher tile temperatures caused by higher energy input in the third campaign.EURATOM 633053Japan Society for the Promotion of Science JP2628935

Investigation of deuterium trapping and release in the JET ITER-like wall divertor using TDS and TMAP

Selected set of samples from JET ITER-Like Wall (JET-ILW) divertor tiles exposed both in 2013–2014 and 2011–2014 has been analysed using Thermal Desorption Spectrometry (TDS). The deuterium (D) amounts obtained with TDS were compared with Ion Beam Analysis (IBA) and Secondary Ion Mass Spectrometry (SIMS) data. The highest amount of D was found on the top part of inner divertor which has regions with the thickest deposited layers. This area resides deep in the scrape-off layer. Changes in plasma configurations between the first (2011–2012) and the second (2013–2014) JET-ILW campaign altered the material migration towards the inner and the outer divertor corner increasing the amount of deposition in the shadowed areas of the divertor base tiles. D retention on the outer divertor tiles is clearly smaller than on the inner divertor tiles. Experimental TDS spectra for samples from the top part of inner divertor and from the outer strike point region were modelled using TMAP program. Experimental deuterium profiles obtained with SIMS have been used and the detrapping and the activation energies have been adjusted. Analysis of the results of the TMAP simulations enabled to determine the nature of traps in different samples.Peer reviewe

Deuterium retention on the tungsten-coated divertor tiles of JET ITER-like wall in 2015-2016 campaign

Tungsten-coated divertor files exposed during the third JET ITER-Like Wall (ILW) campaign in 2015-2016 (ILW-3) were studied with Secondary Ion Mass Spectrometry (SIMS). ILW-3 campaign contained more high-power plasma discharges and longer plasma time than the earlier ILW campaigns. Measurements showed increased beryllium (Be) deposition on the upper inner divertor, whereas on the outer divertor, Be deposition was lower than during the second campaign in 2013-2014 (ILW-2). Increased intensifies of nickel, molybdenum and tungsten were observed at the surface layer of the inner divertor Be dominated deposits. These layers are probably formed during the high-power plasma discharge phase near the end of the ILW-3 campaign. Compared to the earlier campaigns, D retention on the upper inner divertor was observed to on a similar level than after ILW-2, whereas at the lower inner divertor and most parts of the outer divertor, D retention was lower for ILW-3 than ILW-2. D retention was increased at lower part of outer divertor Tile 7, where Be deposition was slightly increased. Probable reason for the reduction is the higher surface temperature of the files due to higher powers used.Peer reviewe

ENTRAP and its potential interaction with European networks

AbstractENTRAP comprises a pan-European cooperation of leading scientific institutions and regulatory bodies in the field of nuclear-waste characterization and its quality assurance for the safe disposal of radioactive waste. Here, the scope of this cooperation is presented and explained and links or interfaces for a potential collaboration with partners fulfilling tasks of IDG-TP are pursued

Overview of the JET ITER-like wall divertor

The work presented draws on new analysis of components removed following the second JET ITER-like wall campaign 2013–14 concentrating on the upper inner divertor, inner and outer divertor corners, lifetime issues relating to tungsten coatings on JET carbon fibre composite divertor tiles and dust/particulate generation. The results show that the upper inner divertor remains the region of highest deposition in the JET-ILW. Variations in plasma configurations between the first and second campaign have altered material migration to the corners of the inner and outer divertor. Net deposition is shown to be beneficial in the sense that it reduces W coating erosion, covers small areas of exposed carbon surfaces and even encapsulates particles.The work presented draws on new analysis of components removed following the second JET ITER-like wall campaign 2013–14 concentrating on the upper inner divertor, inner and outer divertor corners, lifetime issues relating to tungsten coatings on JET carbon fibre composite divertor tiles and dust/particulate generation. The results show that the upper inner divertor remains the region of highest deposition in the JET-ILW. Variations in plasma configurations between the first and second campaign have altered material migration to the corners of the inner and outer divertor. Net deposition is shown to be beneficial in the sense that it reduces W coating erosion, covers small areas of exposed carbon surfaces and even encapsulates particles.Peer reviewe

KOMERSIALISASI PENDIDIKAN DI ERA GLOBALISASI (Studi Kasus tentang Persepsi Masyarakat terhadap Kuasa Modal dalam Dunia Pendidikan di Kelurahan Jebres, Kecamatan Jebres, Surakarta tahun 2011)

Dwi Hartini. K8407021. KOMERSIALISASI PENDIDIKAN DI ERA GLOBALISASI (Studi Kasus Tentang Persepsi Masyarakat terhadap Kuasa Modal dalam Dunia Pendidikan di Kelurahan Jebres, Surakarta). Skripsi Surakarta: Fakultas Keguruan dan IImu Pendidikan. Universitas Sebelas Maret. 2011. Penelitian ini bertujuan untuk (1) Mengetahui komersialisasi pendidikan yang terjadi di era globalisasi, (2) Mengetahui dampak adanya komersialisasi pendidikan di era globalisasi masyarakat, (3) Mengetahui upaya yang dilakukan masyarakat dalam menghadapi komersialisasi pendidikan yang terjadi di era globalisasi. Penelitian ini menggunakan metode pendekatan kualitatif dengan studi kasus tunggal terpancang. Sumber data dari informan atau narasumber, peristiwa atau aktivitas, dokumen dan arsip serta studi pustaka. Teknik cuplikan menggunakan purposive sampling. Pengumpulan data menggunakan observasi berperan pasif, wawancara dan dokumentasi. Validitas data menggunakan trianggulasi data (sumber) dan metode. Teknik analisis data yang digunakan adalah metode analisis interaktif. Berdasarkan hasil penelitian, dapat disimpulkan 1) Komersialisasi pendidikan yang terjadi di era globalisasi yaitu (a) biaya pendidikan mahal, (b) banyaknya pungutan-pungutan lembaga pendidikan, (c) perdagangan di dunia pendidikan. 2) Dampak positif adanya komersialisasi pendidikan di era globalisasi bagi masyarakat yaitu (a) beban pemerintah membiayai pendidikan semakin berkurang, (b) lembaga pendidikan semakin kompetitif sehingga meningkatkan fasilitas dan mutu pendidikan, (c) menambah keuntungan dan pemasukan kas lembaga pendidikan, sedangkan dampak negatifnya yaitu (a) pendidikan semakin mahal (b) pendidikan sebagai ladang bisnis, (c) gejala stigmatisasi dan diskriminasi antara kaya dan miskin, (d) rantai kemiskinan yang sulit diputuskan melalui pendidikan, (e) tercipta privatisasi pendidikan, (f) sistem suap atau politik uang (money politics) semakin banyak, (g) memacu gaya hidup “besar pasak daripada tiang”, (h) perubahan misi pendidikan dari budaya akademik menjadi budaya ekonomi. 3) Upaya yang dilakukan masyarakat dalam menghadapi komersialisasi pendidikan di era globalisasi yaitu (a) pasrah dengan keadaan seperti pepatah Jawa ”setiap anak membawa rejeki sendiri-sendiri”, (b) memanfaatkan kemajuan teknologi untuk meminimalisir pengeluaran, (c) Pendidikan mahal serta keuangan keluarga yang minim memaksa masyarakat untuk meminjam dana dari bank atau orang lain bahkan menggadaikan atau menjual barang berharga, (d) Kerja keras untuk menambah pendapatan, (e) mengikuti program asuransi maupun tabungan pendidikan, (f) bagi pemerintah seharusnya memperbesar anggaran untuk membantu pendidikan

A machine learning approach based on generative topographic mapping for disruption prevention and avoidance at JET

The need for predictive capabilities greater than 95% with very limited false alarms are demanding requirements for reliable disruption prediction systems in tokamaks such as JET or, in the near future, ITER. The prediction of an upcoming disruption must be provided sufficiently in advance in order to apply effective disruption avoidance or mitigation actions to prevent the machine from being damaged. In this paper, following the typical machine learning workflow, a generative topographic mapping (GTM) of the operational space of JET has been built using a set of disrupted and regularly terminated discharges. In order to build the predictive model, a suitable set of dimensionless, machine-independent, physics-based features have been synthesized, which make use of 1D plasma profile information, rather than simple zero-D time series. The use of such predicting features, together with the power of the GTM in fitting the model to the data, obtains, in an unsupervised way, a 2D map of the multi-dimensional parameter space of JET, where it is possible to identify a boundary separating the region free from disruption from the disruption region. In addition to helping in operational boundaries studies, the GTM map can also be used for disruption prediction exploiting the potential of the developed GTM toolbox to monitor the discharge dynamics. Following the trajectory of a discharge on the map throughout the different regions, an alarm is triggered depending on the disruption risk of these regions. The proposed approach to predict disruptions has been evaluated on a training and an independent test set and achieves very good performance with only one tardive detection and a limited number of false detections. The warning times are suitable for avoidance purposes and, more important, the detections are consistent with physical causes and mechanisms that destabilize the plasma leading to disruptions.Peer reviewe

An assessment of nitrogen concentrations from spectroscopic measurements in the JET and ASDEX upgrade divertor

The impurity concentration in the tokamak divertor plasma is a necessary input for predictive scaling of divertor detachment, however direct measurements from existing tokamaks in different divertor plasma conditions are limited. To address this, we have applied a recently developed spectroscopic N II line ratio technique for measuring the N concentration in the divertor to a range of H-mode and L-mode plasma from the ASDEX Upgrade and JET tokamaks, respectively. The results from both devices show that as the power crossing the separatrix, P-sep, is increased under otherwise similar core conditions (e.g. density), a higher N concentration is required to achieve the same detachment state. For example, the N concentrations at the start of detachment increase from approximate to 2% to approximate to 9% as P-sep, is increased from approximate to 2.5 MW to approximate to 7 MW. These results tentatively agree with scaling law predictions (e.g. Goldston et al.) motivating a further study examining the parameters which affect the N concentration required to reach detachment. Finally, the N concentrations from spectroscopy and the ratio of D and N gas valve fluxes agree within experimental uncertainty only when the vessel surfaces are fully-loaded with N.Peer reviewe