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| 3. |
- Coad, J. P., et al.
(author)
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Erosion and deposition in the JET MkII-SRP divertor
- 2007
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In: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 363, s. 287-293
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Journal article (peer-reviewed)abstract
- Carbon-13 labelled methane was injected into the outer divertor during a series of H-mode discharges on the last day of operations with the JET MkII-SRP divertor. Tiles from around the vessel were removed during the subsequent shutdown and surface deposits were analysed by IBA techniques and SIMS. First attempts to model the pattern of 13 C deposition using EDGE2D are reported. Erosion of W markers at the outer divertor was observed, with implications for the ITER-like wall experiment planned for JET, whilst thin film growth in the same region has been followed by the effect on infrared measurements. The composition of thick films deposited at the inner divertor during the MkII-SRP campaign, and the migration to the inner corner of the divertor observed by a quartz micro-balance, provide further information on divertor transport. Crown
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| 4. |
- Coad, J. P., et al.
(author)
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Overview of material re-deposition and fuel retention studies at JET with the Gas Box divertor
- 2006
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In: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 46:2, s. 350-366
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Journal article (peer-reviewed)abstract
- in the period 1998-2001 the JET tokamak was operated with the MkII Gas Box divertor. On two occasions during that period a number of limiter and divertor tiles were retrieved from the torus and then examined ex situ with surface sensitive techniques. Erosion and deposition patterns were determined in order to assess the material erosion, material migration and fuel inventory on plasma facing components. Tracer techniques, e.g. injection of C-13 labelled methane and tiles coated with a low-Z and high-Z marker layer, were used to enhance the volume of information on the material transport. The results show significant asymmetry in the distribution of fuel and plasma impurity species between the inner (net deposition area) and the outer (net erosion) divertor channels. No significant formation of highly hydrogenated carbon films has been found in the Gas Box structure. The important processes for material migration, and the influence of operation scenarios on the morphology of the deposits are discussed. Comparison is also made with results obtained following previous divertor campaigns.
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| 5. |
- Likonen, J., et al.
(author)
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Beryllium accumulation at the inner divertor of JET
- 2005
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In: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 337-39:03-jan, s. 60-64
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Journal article (peer-reviewed)abstract
- MkIIGB divertor tiles exposed in JET for the 1998-2001 and 1999-2001 campaigns have been used to assess the amount of beryllium and carbon deposited at the inner divertor wall. Total amount of Be at the inner divertor tiles was determined and integrated toroidally. Results were compared with data obtained with optical spectroscopy and good agreement was obtained. The amount of deposited C was computed from the amount of deposited Be assuming that the Be/C ratio arriving in the divertor is the same as the Be/C ratio in the main chamber. On the basis of this analysis we would expect there to be similar to 0.4 kg of C deposited. This gives an average C deposition rate lower than during the MkIIA phase.
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| 6. |
- Likonen, J., et al.
(author)
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Post-mortem measurements of fuel retention at JET with MKII-SRP divertor
- 2009
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In: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 390-91, s. 631-634
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Journal article (peer-reviewed)abstract
- The deuterium inventory at JET after 2001-2004 operational campaign has been determined using nuclear reaction analysis (NRA) and secondary ion mass spectrometry (SIMS). A full poloidal set of divertor tiles and a set of outer poloidal limiter (OPL) tiles were analysed providing an estimation for the total deuterium retention of about 66 g. Deuterium is trapped mainly at the inner divertor on horizontal target tile and at the inner divertor louvre area where similar to 60% of the trapped D is found. The long-term D retention is similar to 4% of the total D input.
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| 7. |
- Likonen, J., et al.
(author)
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Structural investigation of re-deposited layers in JET
- 2008
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In: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 377:3, s. 486-491
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Journal article (peer-reviewed)abstract
- JET Mk-II Gas Box divertor tiles exposed in 1998-2001 have been analysed with various ion beam techniques, secondary ion mass spectrometry (SIMS) and Raman spectroscopy. Inner divertor wall tiles removed in 2001 were covered with a duplex film. The inner layer was very rich in metallic impurities, with Be/C - 1 and H-isotopes only present at low concentrations. The outer layer contained higher concentrations of D than normal for plasma-facing surfaces in JET (D/C - 0.4), and Be/C - 0.14. Raman and SIMS analyses show that the deposited films on inner divertor tiles are hydrogenated amorphous carbon with low sp' fractions. The deposits have polymeric structure and low density. Both Raman scattering and SIMS indicate that films on inner divertor wall Tiles 1 and 3, and on floor Tile 4 have some differences in the chemical structure of the deposited films
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| 8. |
- Likonen, J., et al.
(author)
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Structural studies of deposited layers on JET MkII-SRP inner divertor tiles
- 2007
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In: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 363, s. 190-195
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Journal article (peer-reviewed)abstract
- Deposited layers formed on JET inner divertor tiles during 1998-2004 and 2001-2004 campaigns have been investigated using secondary ion mass spectrometry (SIMS), Rutherford Backscattering (RBS) and optical microscopy. The thickness of the deposit decreases from the top of vertical tile 1 to the bottom and then increases on vertical tile 3 reaching similar to 60 mu m. There are even thicker deposits on the small sloping section of the floor tile 4 that can be accessed by the plasma at the inner divertor legs. Deposited films on divertor inner wall tiles are enriched in Be indicating chemical erosion of C and a multi-step transport of C to the shadowed area on floor tile 4. The films have generally a layered and globular structure in the areas with plasma contact.
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| 9. |
- Wu, D., et al.
(author)
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A novel strained Si0.7Ge0.3 surface-channel pMOSFET with an ALD TiN/Al2O3/HfAlOx/Al2O3 gate stack
- 2003
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In: IEEE Electron Device Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 0741-3106 .- 1558-0563. ; 24:3, s. 171-173
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Journal article (peer-reviewed)abstract
- Proof-of-concept pMOSFETs with a strained-Si0.7Ge0.3 surface-channel deposited by selective epitaxy and a TiN/Al2O3/HfAIO(x)/Al2O3 gate stack grown by atomic layer chemical vapor deposition (ALD) techniques were fabricated. The Si0.7Ge0.3 pMOSFETs exhibited more than 30% higher current drive and peak transconductance than reference Si pMOSFETs with the same gate stack. The effective mobility for the Si reference coincided with the universal hole mobility curve for Si. The presence of a relatively low density of interface states, determined as 3.3x10(11) cm(-2) eV(-1), yielded a subthreshold slope of 75 mV/dec. for the Si reference. For the Si0.7Ge0.3 pMOSFETs, these values were 1.6x10(12) cm(-2) eV(-1) and 110 mV/dec., respectively.
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| 10. |
- Wu, Dongping, et al.
(author)
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Characterization of high-kappa nanolaminates of HfO2 and Al2O3 used as gate dielectrics in pMOSFETs
- 2004
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In: Integration Of Advanced Micro-And Nanoelectronic Devices-Critical Issues And Solutions. - : Springer Science and Business Media LLC. - 155899761X ; , s. 19-24
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Conference paper (peer-reviewed)abstract
- In order to combine the merits of both HfO2 and Al2O3 as high-kappa gate dielectrics for CMOS technology, high-kappa nanolaminate structures in the form of either Al2O3/HfO2/Al2O3 or Al2O3/HfAlOx/Al2O3 were implemented in pMOSFETs and electrically and microstructurally charachterized. ALD TiN film was used as the metal gate electrodes for the pMOSFETs. After full transistor-processing including a rapid thermal processing step at 930 T, the HfO2 film in the former nanolaminate was found to be crystallized. In contrast, the HfAlOx layer in the latter nanolaminate remained in the amorphous state. Both types of pMOSFETs exhibited a hysteresis as small as similar to20 mV in C-V characteristics in the bias range of +/- 2 V. They also showed a reduced gate leakage current. The pMOSFET with the Al2O3/HfAlOx/Al2O3 nanolaminate was characterized with a subthreshold slope of 77 mV/decade and a channel hole mobility close to the universal hole mobility curve. The pMOSFET with the Al2O3/HfO2/Al2O3, however, exhibited a subthreshold slope of 100 mV/decade and a similar to30W lower hole mobility than the universal curve.
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