Ion debris mitigation from tin plasma using ambient gas, magnetic field and combined effects

Influence of spot size on propagation dynamics of laser-produced tin plasma

“…This is caused by ionization of ambient gas atoms by prompt electrons and/or intense EUV light coming out from the early stages of plasma formation. 16,20 During initial times of plume expansion, the ablated species streams away from the target surface with supersonic free expansion. As time evolves, the plasma species start to sweep background gas species, leading to a pile of mass at the ablation front.…”

“…For collecting ions the FC is positioned at 15 cm away from the target surface and at an angle approximately 12 degrees with respect to the target normal. Since the presence of ambient partial pressure can slow down the fast moving ions, 16 the ion kinetic profiles recorded with the FC are done in vacuum. The ion TOF profile in vacuum is represented by a sharp prompt peak followed by a broad slower peak.…”

“…1,2, 15,16 Presently, a lot of efforts are going on worldwide for optimizing EUV emission from tin plasma and mitigating various debris coming from the plasmas. The debris includes fast ions and neutrals, clusters, and out of band emission and, hence, controlling the expanding plume species is indeed a greatest challenge for future LPP EUV light source.…”

“…The debris includes fast ions and neutrals, clusters, and out of band emission and, hence, controlling the expanding plume species is indeed a greatest challenge for future LPP EUV light source. We employed various methods for controlling and/or mitigating energetic ions including; low-density targets, 4,17 ambient gas, 16 magnetic field, 18 pre-pulse 2 and synergetic effects ͑combina-tion of two methods͒. 16 We recently reported that the spot size has negligible effect on the conversion efficiency ͑CE͒ of in-band radiation ͑13.5 nm with 2% bandwidth͒.…”

“…We employed various methods for controlling and/or mitigating energetic ions including; low-density targets, 4,17 ambient gas, 16 magnetic field, 18 pre-pulse 2 and synergetic effects ͑combina-tion of two methods͒. 16 We recently reported that the spot size has negligible effect on the conversion efficiency ͑CE͒ of in-band radiation ͑13.5 nm with 2% bandwidth͒. 19 The constant CE irrespective of the spot size is attributed to the balance of the laser energy loss due to lateral expansion of the plasma and reabsorption of the EUV light.…”