Development of a deep-sea laser-induced breakdown spectrometer for in situ multi-element chemical analysis

Abstract

a b s t r a c tSpectroscopy is emerging as a technique that can expand the envelope of modern oceanographic sensors. The selectivity of spectroscopic techniques enables a single instrument to measure multiple components of the marine environment and can form the basis for versatile tools to perform in situ geochemical analysis. We have developed a deep-sea laser-induced breakdown spectrometer (ChemiCam) and successfully deployed the instrument from a remotely operated vehicle (ROV) to perform in situ multi-element analysis of both seawater and mineral deposits at depths of over 1000 m. The instrument consists of a long-nanosecond duration pulse-laser, a spectrometer and a high-speed camera. Power supply, instrument control and signal telemetry are provided through a ROV tether. The instrument has two modes of operation. In the first mode, the laser is focused directly into seawater and spectroscopic measurements of seawater composition are performed. In the second mode, a fiberoptic cable assembly is used to make spectroscopic measurements of mineral deposits. In this mode the laser is fired through a 4 m long fiber-optic cable and is focused onto the target's surface using an optical head and a linear stage that can be held by a ROV manipulator. In this paper, we describe the instrument and the methods developed to process its measurements. Exemplary measurements of both seawater and mineral deposits made during deployments of the device at an active hydrothermal vent field in the Okinawa trough are presented. Through integration with platforms such as underwater vehicles, drilling systems and subsea observatories, it is hoped that this technology can contribute to more efficient scientific surveys of the deep-sea environment.

Calibration-free analysis of immersed brass alloys using long-ns-duration pulse laser-induced breakdown spectroscopy with and without correction for nonstoichiometric ablation

“…The excited atoms and ions emit specific wavelengths of light as they relax back to their ground state, which allows for simultaneous multi-element detection. LIBS is a promising tool for on-site chemical analysis and has been applied to the surveys of nuclear powers plants [1,2], planetary [3,4] and deep-sea explorations [5][6][7]. However, LIBS signals obtained underwater using a conventional single pulse method are significantly degraded compared to measurements in gaseous environments [8][9][10].…”

“…It has further been shown that well resolved spectra can be observed for both bulk liquids [17] and submerged solids [18] at pressures of up to 30 MPa with little effect of external pressure using a long-pulse technique. This method has been applied to in situ measurements of seawater and hydrothermal deposits at depths of more than 1000 m, using a 3000 m depth rated long-pulse LIBS device, ChemiCam [5]. The aim of this study is to investigate whether the signals obtained using the long-pulse technique are suitable for quantitative analysis.…”

Study of the Effect of Water Pressure on Plasma and Cavitation Bubble Induced by Pulsed Laser Ablation in Liquid of Silver and Missed Variations of Observable Nanoparticle Features

“…In particularthe employment of high water pressure during laser ablation and the understanding of its role on the laser induced plasma and bubble dynamics can be used in different surveys such as geochemistryi nd eep ocean, [1] laser propulsion in water, [2] hydraulic machinery [3] biomedicine. In particularthe employment of high water pressure during laser ablation and the understanding of its role on the laser induced plasma and bubble dynamics can be used in different surveys such as geochemistryi nd eep ocean, [1] laser propulsion in water, [2] hydraulic machinery [3] biomedicine.…”

Effects of temporal laser profile on the emission spectra for underwater laser-induced breakdown spectroscopy: Study by short-interval double pulses with different pulse durations

“…1-3 Especially, LIBS has a potential to be applied even to underwater environments, and the application to in-situ remote analysis at the bottom of the sea/lake is highly desired. [4][5][6][7][8][9][10][11] However, the emission spectra of the laser-induced plasma in water are severely deformed [12][13][14] due to the strong confinement effect on the plasma. [15][16][17] To overcome this problem, double-pulse or multi-pulse irradiation with a pulse interval of tens of microseconds 4,12,[18][19][20][21][22] and single long-pulse ($150 ns) irradiation 5, [23][24][25][26] have been investigated, and the use of such irradiation schemes have been found to improve the spectral features of atomic lines for underwater LIBS applications, i.e., narrow spectral lines are obtained.…”