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Tritium (T) inventory in Plasma Facing Components (PFCs) will be one of the critical issues for ITER because of the impact tritium can have on the machine operation and safety. Laser Induced Breakdown Spectroscopy (LIBS) is a promising technique to accomplish this task, providing both qualitative and quantitative composition of the chemical elements retained in PFCs. LIBS does not require sample pretreatment or manipulation, it can work in-situ between fusion discharges or during maintenance periods, it is suitable for measurements at different residual pressures, with different background gases. It can detect all the chemical elements through their spectral emission. This paper presents the results of LIBS measurements at 100 mbar nitrogen pressure on metallic coating (W-Al-D) simulating the superficial composition of ITER divertor PFCs contaminated with nuclear fuel and material eroded from the first wall. LIBS spectra showed clear W, Al, D emission lines. A quantitative estimation of their relative concentration was performed by applying the Calibration Free (CF) analysis. CF does not require reference samples, so it's particularly suitable for this purpose. CF results were compared with the nominal concentrations and were found in good agreement with the latter.

The amount of hydrogen isotopes retained in plasma facing components (PFCs) and the determination of their surface layer composition are among the most critical issues for the next generation fusion device, ITER, under construction in Cadarache (France). Laser Induced Breakdown Spectroscopy (LIBS) is currently under evaluation as a technique suitable for quantitative, in situ, non-invasive measurements of these quantities. In order to detect traces of contaminant in metallic samples and improve its limit of detection (LOD), the Double Pulse LIBS (DP-LIBS) variant can be used instead of the standard Single Pulse LIBS (SP-LIBS), as it has been proven by several authors that DP-LIBS can considerably raise the analytical performances of the technique. In this work Mo samples coated with a 1.5–1.8 μm thick W-Al mixed layer, contaminated with co-deposited deuterium (D) were measured by SP- and DP-LIBS under vacuum (p ~ 5 × 10− 5 mbar), with an experimental set-up simulating conditions that can be found in a real fusion device between plasma discharges. A partial Calibration Free procedure (pCF) was applied to the LIBS data in order to retrieve the relative concentration of W and Al in the mixed layer. The amount of deuterium was then inferred by using tungsten as internal standard, accounting for the intensity ratio between the Dα line and nearby W I lines. The results are in satisfactory agreement with those obtained from preliminary Ion Beam Analysis measurements performed immediately after the specimen's realization. © 2017 Elsevier B.V.

In this paper the Laser Induced Breakdown Spectroscopy (LIBS) measurement of the deuterium (used as a proxy for tritium) retained in and the surface elemental composition of the FTU Mo (TZM) toroidal limiter tiles, carried out from remote (∼2.5 m) during short breaks of the operations or during machine maintenance, are reported. Single pulse technique has been used with the FTU vessel under high vacuum or in Nitrogen or Argon atmosphere. In vacuum experiments Dα and Hα lines have been detected with good resolution, while in Ar atmosphere (5 × 104 Pa) the two lines were partially overlapped due to Stark broadening. First results of measurements in N2 atmosphere (105 Pa) showed no presence of Dα and Hα lines. These measurements were also carried out for supporting the foreseen use of a robotic arm for an extended LIBS analysis of retained deuterium in the FTU vessel components. Keywords: LIBS, FTU tokamak, Toroidal limiter, Deuterium retention

High temperature plasma in hydrogen isotopes is peculiar of thermonuclear fusion devices. The study of plasma-wall interaction is of paramount importance for avoiding both damage of plasma facing components (PFCs) and pollution of the plasma. To assure continuous and fault-free operation a strict control must be exerted on the amount of impurities deposited on, and of the fuel retained in the PFCs. This requirement makes Laser-Induced-Breakdown-Spectroscopy (LIBS) an ideal candidate for on-line quantitative monitoring of the walls of the current as well as of the next generation fusion devices like the International Thermonuclear Experimental Reactor (ITER). An experimental setup has been designed and realized in order to optimize the characteristics of a LIBS system working at low pressure and remotely, and it has been utilized in combination with calibration free procedures for quantitative analysis. In this work, a partial calibration free method has been developed for single shot analysis of hydrogen isotopes retention at the PFCs-like surfaces, based on the acquisition of high resolution spectra in a narrow wavelength range. Results of calibration free and partial calibration free have been obtained on suitably deuterated samples; preliminary spectroscopic considerations on tritium detection are also presented. © 2013 Elsevier B.V. All rights reserved.

The study of plasma-wall interactions is of paramount importance for continuous and fault free operations in thermonuclear fusion research to monitor the damages of plasma facing components (PFCs), plasma pollution from impurities and wall retention of hydrogen isotopes, like tritium. These needs make laser-induced-breakdown-spectroscopy (LIBS) a suitable candidate for a real time monitoring of PFCs in the current and next generation fusion devices, like ITER. It is also worthwhile for the quantitative analysis of surfaces, with micro-destructivity of the sample and depth profiling capabilities with sub-micrometric sensitivity. In this paper LIBS spectroscopy is exploited as a valid diagnostic tool for PFCs at the ENEA Research Center in Frascati (Italy) and at the Institute of Plasma Physics and Laser Microfusion (IPPLM) of Warsaw (Poland). The activities have been focused on LIBS characterization of samples simulating PFCs surfaces eroded/redeposited or contaminated from nuclear fuel after or during the normal operation of the reactor. © 2016 The Royal Swedish Academy of Sciences.

Estimating the tritium amount retained in the plasma facing components and their surface layer composition is of crucial importance for ITER. Laser-induced breakdown spectroscopy (LIBS) is an analytical technique suitable for in situ measurements of both these quantities. For improving its sensitivity, the double pulse (DP) variant can be used, instead of the standard single pulse (SP). In this work Mo samples coated with 1.5-1.8 μm thick W-Al (as a proxy for Be) mixed layer, with co-deposited deuterium were analyzed under vacuum (∼5 10-5 mbar) by SP and DP LIBS, showing enhancement of the spectral intensity for the latter. Calibration free method was applied to the LIBS data for getting the elemental concentration of W and Al. Results are in satisfactory agreement with those obtained from preliminary, ion beam analysis measurements. Deuterium concentration was tentatively estimated by accounting for the intensity ratio between Dα and nearby WI lines. © 2016 EUROfusion.

Laser Induced Breakdown Spectroscopy (LIBS) is an attractive analytical technique for the in situ analysis of the chemical composition of the components inside the vacuum vessel of ITER and for estimating the tritium content in the machine. To improve its sensitivity a dual pulse (DP) configuration, with two laser pulses delayed in the range of nanosecond to several microseconds can be used. In this work DP measurements carried out jointly by ENEA and IPPLM associations in the frame of EFDA task WP13-IPH-A01-P3-01 on samples resembling ITER in vessel components after material re-deposition (still including carbon) are presented. A DP Nd:YAG laser, operating at 1064 nm, with delay between pulses ranging from 20 ns to 80 ms and pulse duration of 8-12 ns was used to interact with tungsten sample coated with 3 μm thick mixed layer of C/Al/W (Al was used instead of Be). An enhancement of the spectroscopic emission of the elements was observed compared to the standard LIBS measurements. A Calibration Free method was applied to the data for getting the concentration of each element. Results are in good agreement with the concentrations found by the post-mortem energy dispersive X-ray (EDX) analysis. © 2015 Elsevier B.V. All rights reserved.

Analytical performances of Laser Induced Breakdown Spectroscopy (LIBS) resulted not fully satisfactory in some cases such as historical bronzes, therefore, efforts should be focussed on improving ablation efficiency and on better understanding the plasma parameter evolution. To this aim a set of double pulse experiments have been carried out in almost collinear geometry at about 530 nm laser excitation. The first emitting source was either a ns or a fs laser the second a ns one. Data were collected as a function of the interpulse delay, in order to determine the ablation efficiency increase, to study the kinetics of plasma parameters (temperature, electron density) and the decay of atomic and ionic intensities with respect to the optical background. In parallel a previously developed model for laser ablation, ionization and following plasma decay, was implemented, adding a second laser pulse, to analyse the double pulse excitation in the considered geometry, and the time evolution of the same variables was investigated. Model results are able to reproduce the observed experimental trends and support the possibility of improving analytical performances by using the double pulse technique with inter-pulse delays in the entire investigated range. © 2014 Elsevier B.V.

Laser Induced Breakdown Spectroscopy (LIBS) is a potential candidate to monitor the layer composition and fuel retention during and after plasma shots on specific locations of the main chamber and divertor of ITER. This method is being investigated in a cooperative research programme on plasma devices such as TEXTOR, FTU, MAGNUM-PSI and in other various laboratorial experiments. In this paper LIBS results from targets of D-H-rich carbon films and mixed W-Al-C deposits on bulk tungsten substrates are reported (simulating ITER-like deposits with Al as proxy for Be). Two independent methods, one to determine the relative elemental composition and the other the absolute contents of the target based on the experimental LIBS signals are proposed. The results show that LIBS has the capability to provide the relative concentrations of the elements on the deposited layer when the experimental conditions on the targets surface are identical to the calibration samples. © 2013 Elsevier B.V. All rights reserved.