Characterization of <i>in situ</i> work function and cesium flux measurement setup suitable for cesium seeded negative ion source applications

Singh, Pranjal; Bandyopadhyay, M.; Pandya, K.; Bhuyan, M.; Chakraborty, Arun

doi:10.1088/1741-4326/ab312c

Cited by 8 publications

(1 citation statement)

References 26 publications

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“…It is experimentally observed that optimum Cs coverage on tungsten (W) or molybdenum (Mo) surfaces can achieve very low work functions in the range of 1.4-1.6 eV [6]. During negative ion source operation, the Cs monolayer is continuously renewed, with the caesiated surfaces maintained at 150 • C to keep the work function as low as possible and preserve the balance between Cs evaporation and deposition rates [7,8].…”

Section: Introductionmentioning

confidence: 99%

Investigations on Caesium Dispersion and Molybdenum Coating on SPIDER Components

et al. 2022

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SPIDER is the 100 keV full-size Negative Ion Source prototype of the ITER Neutral Beam Injector, operating at Consorzio RFX in Padova, Italy. The largest Negative Ion Source in the world, SPIDER generates an RF driven plasma from which Deuterium or Hydrogen negative ions are produced and extracted. At the end of 2021, a scheduled long-term shutdown started to introduce major modifications and improvements aiming to solve issues and drawbacks identified during the first three years of SPIDER operations. The first action of the shutdown period was the disassembly and characterization of the SPIDER beam source after removal from the vacuum vessel and its placement inside the clean room. Each component was carefully assessed and catalogued, following a documented procedure. Some source components, i.e., the Plasma Grid, Extraction Grid and Bias Plate, revealed the presence of different and non-uniform red, white and green coatings that might be correlated to back-streaming positive ions impinging on grid surfaces, electrical discharges and caesium evaporation. Thus, several analyses have been carried out to understand the nature of such coatings, with the study still ongoing. The evidence of caesium evaporation and deposition on molybdenum-coated SPIDER components, such as the formation of oxides and hydroxides, is demonstrated through surface characterization analyses with the use of the Scanning Electron Microscope (SEM), X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS).

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Section: Introductionmentioning

confidence: 99%