Intensified Charge-coupled Device Research Articles

Fast breakdown process and characteristics diagnosis of nanosecond pin–pin discharge

In this paper, the characteristics of a nanosecond spark discharge with a pin–pin electrode configuration have been systematically studied. Both a streak camera with high temporal resolution and an intensified charge-coupled device (ICCD) camera are employed together to investigate the breakdown and evolution process of the discharge. The formation of initial breakdown and mode transition from streamer to spark in the electrode gap are clearly observed on the time scale of several nanoseconds with a temporal resolution of 100 ps. In addition, the time-resolved spectra technology is also used to analyze the generation and quenching mechanisms of reactive species, the electron density, and the electron temperature. The results show that there is a 1.25 ns initial discharge breakdown and that a bright cathode spot exists before the transformation from streamer to spark channel. After a faster cathode filament and a slower anode filament propagate and merge at the electrode gap, the spark discharge phase begins. The generation processes of different reactive species depend on the discharge phase to a great extent. The N2* is first generated during the streamer phase while the O*, N*, and N+ are mainly generated under the spark phase, in which the electron temperature calculated by Boltzmann plots is 2.74 eV, and the electron density determined from the Stark broadening of O lines is on the order of 1016 cm−3.

Experimental study on the structure and propagation of the stretched hydrogen-rich turbulent premixed flames in the thin-reaction-zone regime

An experimental study on the structure and propagation of the stretched hydrogen-rich premixed turbulent flames in the thin-reaction-zone regime was conducted. A set of optical diagnostic techniques including the 2D/3D-particle image velocimetry, hot wire anemometer, intensified charge-coupled device (ICCD), and laser tomography visualization (LTV) methods were adopted to quantitatively measure the velocity field, turbulent intensity, and thickness of the stretched flame of the under various conditions. A new method to improve the measurements of the flame preheat zone thickness was developed by using the low-temperature available LTV method to identify the onset of the preheat zone and using the peak location of CH* to identify the reaction zone. The results showed that the flow field was in the inertial turbulent subrange and the turbulent flames obtained in the present counterflow configuration were categorized into the thin reaction zone regime in Borghi/Peters turbulent flame diagram. The experimental results showed that the flame structure of a turbulent H2-rich premixed flame was synergistically influenced by the hydrodynamic stretch, turbulence, and preferential diffusion. New evidence of the phenomenon accumulated that large-scale vortices wrinkled the surface of the flame while small-scale vortices penetrated into the flame preheat zone. Scaling laws for the turbulent flame propagation speed, apparent turbulent thermal conductivity, and were given with the consideration of the synergetic effect of hydrodynamic stretch, turbulence, and preferential diffusion. The scaling of the turbulent flame preheat zone thickness turned out to be sensitive, while those of the turbulent flame propagation speed and apparent turbulent thermal conductivity were insensitive, to the bulk flow strain rate.

DBD-streamer mode transition of atmospheric-pressure plasma jet applied on water with varying distance and AC power

The discharge of atmospheric-pressure plasma jet (APPJ) applied on the water was studied by varying an air gap between a powered electrode and the water, and the alternating current power. It was found that the streamers were converged by the air flow to form a streamer bridge to allow current flow across the air gap to transition from a dielectric barrier discharge (DBD) mode to a streamer mode. Because the AC power alternates periodically, this study proposed an analysis without the parameter of time by the voltage amplitude to power characteristic. It was found that the longer distance required higher voltage amplitude and power to transition. Prior research of plasma rarely mentioned the real power and the reactive power, which are essential for electric devices. Because different discharge mode produces different species, this study proposed a simple method to analyze and predict discharge modes based on the power factor, which presents the relationship of the real power and the reactive power. It was found that the streamer mode had a higher power factor than the DBD mode, and thus the power factor decides the discharge mode. Therefore, a power factor analysis can be a systematic basis to produce the required discharge by changing the equivalent capacitance and resistance to change the reactive power and real power. This study proposed a simple method to analyze periodic discharge by the intensified charge-coupled device (ICCD). A period of the AC was divided into twelve timings. For each timing, each shot was configured to have the minimum exposure time to avoid the afterimage. Thousands of shots were overlapped into one snapshot to increase the fluorescence and make such snapshot more representative for the timing. Snapshots show that the streamer bridge was only formed in specific timings periodically.

Visualizing the Hardy's Paradox using Hyper‐Entanglement‐Assisted Ghost Imaging

AbstractThe concept of quantum nonlocality, lying at the heart of quantum information science and technologies, is physically counter‐intuitive and mathematically elusive. Here, a hyper‐entanglement‐assisted ghost imaging system is designed to visualize the evidence of Hardy's paradox by capturing the purely nonlocal photonic events with a spatially resolved intensified charge‐coupled device (ICCD) camera. In the two‐photon polarization‐spatial‐mode hyper‐entangled state, spatial entanglement conveys the ghost images while polarization entanglement encodes the imaging channels in the logical structure of Hardy's nonlocality proof. Then whether the single ghost image of a skull‐shape object is observed or not can be a direct yet intuitive signature to support or defy quantum mechanics. Moreover, the degree of the violation of locality can be characterized by the contrast‐to‐noise ratio of ghost images macroscopically, and the nonlocal behavior of violating the locality microscopically at the single‐pixel level with a reasonable confidence level of 75% is also achieved. The proposed strategy not only sheds new light on the fundamental issue of quantum mechanics, but also holds promise for developing hyper‐entanglement‐based quantum imaging technology.

Analysis of Discharge Failure Mechanism of IGBT Power Modules

IGBT power modules are usually used as circuit-breaking components in power systems, and are widely used in solid-state DC circuit breakers, hybrid DC circuit breakers, all-electric aircraft, high-speed railways, new energy vehicles, and power transmission systems. In these systems, IGBT power modules are usually faced with extremely harsh working conditions and there is a failure risk. Insulation degradation should be a cause for concern as a potential path of power module failure. In this paper, the discharge phenomena of the IGBT power module were observed based on Intensified Charge Coupled Devices (ICCD), and the triple junctions composed of copper–ceramic–silicone gel inside IGBT were found as the discharge points. Furthermore, the directed bonded copper (DBC) ceramic filled with silicone gel was used as a test sample to study the discharge failure process, including the partial discharge (PD), surface charges, and electric trees. The mechanism of discharge failure is discussed and analyzed. The insulation degradation process is accompanied by phenomena such as severe partial discharge and rapid electric tree growth. This research provides support for the analysis idea and guidance of the research method for the cause of power module failure.

Range-Gated LIDAR Utilizing a LiNbO3 (LN) Crystal as an Optical Switch

In this paper, a range-gated LIDAR system utilizing an LN crystal as the electro-optical switch and a SCMOS (scientific complementary metal oxide semiconductor) imaging device is designed. To achieve range-gated operations, we utilize two polarizers and an LN (LiNbO3) crystal to form an electro-optical switch. The optical switch is realized by applying a pulse voltage at both ends of the crystal due to the crystal’s conoscopic interference effect and electro-optical effect. The advantage of this system is that low-bandwidth detectors, such as a CMOS and a CCD (charge-coupled device), can be used to replace conventional high-bandwidth detectors, such as an ICCD (intensified charge-coupled device), and it displays better imaging performance under specific conditions at the same time. However, after using an electro-optical crystal as an optical switch, a new inhomogeneity error will be introduced due to the conoscopic interference effect of the electro-optical crystal, resulting in a range error for the LIDAR system. To reduce the influence of inhomogeneity error on the system, this paper analyzes the sources of inhomogeneity error caused by the electro-optical crystal and calculates the crystal’s inhomogeneity mathematical expression. A compensation method is proposed based on the above inhomogeneity mathematical expression. An experimental LIDAR system is constructed in this paper to verify the validity of the compensation method. The experimental results of the range-gated LIDAR system show that in a specific field of view (2.6 mrad), the LIDAR system has good imaging performance; its ranging standard deviation is 3.86 cm and further decreases to 2.86 cm after compensation, which verifies the accuracy of the compensation method.

A Low-Cost Test Method for Accurate Detection of Different Excited-State Species with a Lifetime Span over 5 Orders of Magnitude in One Time Window

Accurate quantification on the quantum yields (φ) of both the prompt fluorescence (PF) and the delayed fluorescence (DF) species is quite essential for the clarification of molecular design rationales for thermally activated delayed fluorescence (TADF) luminogens. Currently, most φPF and φDF data of TADF fluorophores were acquired through time-correlated single-photon counting (TCSPC) lifetime measurement systems. However, because of their equal-time-channel working manner, so far all the commercially available TCSPC systems cannot render accurate measurement on φPF of TADF materials due to the lack of enough valid data points in the faster decay region of the corresponding photoluminescence (PL) decay curves. Although an intensified charge coupled device (ICCD) system equipped with a streak camera or an optical parametric oscillation laser has been proven to be a powerful tool for accurate determination of φPF and φDF of TADF fluorophores, the ultrahigh cost of these ICCD systems makes them inaccessible to most users. Herein, by replacing the timing module of a commercial TCSPC system with a low-cost and versatile time-to-digital converter (TDC) module, we developed a modified TCSPC system that can work in an unequal-time-channel manner. The resultant TDC-TCSPC system can not only concurrently determine the accurate lifetime of PF and DF species whose lifetime span even exceeds 5 orders of magnitude in just one time window but also render accurate measurements on φPF and φDF of TADF fluorophores. The reliability of the TDC-TCSPC method was verified through TCSPC- and ICCD-based comparative experiments on ACMPS, a known TADF fluorophore. Our results not only can provide a low-cost and convenient test method for accurate determination of key experimental data of TADF materials but also will facilitate deeper understanding of the molecular design principles for high-performance TADF materials.

Effect of neutral pressure on the blue core in Ar helicon plasma under an inhomogeneous magnetic field

The effect of neutral pressure on the blue core in Ar helicon plasma under an inhomogeneous magnetic field was investigated in this work. The neutral pressure was set to 0.08 Pa, 0.36 Pa, and 0.68 Pa. A Nikon camera, intensified charge-coupled device (ICCD), optical emission spectrometer (OES), and Langmuir probe were used to diagnose the blue core in helicon plasma. Helicon plasma discharges experienced density jumps from the E mode, H mode to W mode before power just rose to 200 W. The plasma density increased and maintained a central peak with the increase of neutral pressure. However, the brightness of the blue core gradually decreased. It is demonstrated that the relative intensity of Ar II spectral lines and the ionization rate in the central area were reduced. Radial electron temperature profiles were flattened and became hollow as neutral pressure increased. It is demonstrated that increasing the neutral pressure weakened the central heating efficiency dominated by the helicon wave and strengthened the edge heating efficiency governed by the TG wave and skin effect. Therefore, the present experiment successfully reveals how the neutral pressure affects the heating mechanism of helicon plasma in an inhomogeneous magnetic field.

Study of increment of emission intensity in a cold atmospheric pressure helium plasma jet using the ADAS

In this paper, the Atomic Data and Analysis Structure (ADAS) has been used to study the cold atmospheric pressure plasma jet. Variation of emission intensity pattern from glass nozzle to the plasma jet tip of a helium plasma jet in ambient air has been observed from the intensified charge-coupled device (ICCD) camera image. The increase of intensity pattern towards the plasma jet tip is an important and fundamental feature of the plasma jet in ambient air. The correlation of this observed pattern with electron impact processes has been studied by computing photon emissivity coefficients (PEC) using the ADAS. The role of various atomic processes involved in this study has also been discussed.

Frequency-Tuned Porous Polyethylene Glycol Films Obtained in Atmospheric-Pressure Dielectric Barrier Discharge (DBD) Plasma

This study focuses on the fabrication of plasma-polymerized polyethylene glycol (pp-PEG) with porous morphology in a pulsed dielectric barrier discharge (DBD) plasma under atmospheric pressure. The signal frequency that modulates the plasma discharge was found to have a major influence on the pp-PEG film morphology. The recorded discharge current–voltage characteristic allowed us to establish a homogeneous regime of the DBD plasma operated in helium gas flow upon the frequency range 2–10 kHz. The as-prepared pp-PEG films were characterized by the Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and liquid-phase chromatography (HPLC) techniques. The performed analysis revealed that as the discharge frequency increases, the morphology of the obtained films becomes porous due to the plasma-induced stronger monomer fragmentation. To gain knowledge about the plasma species and the interaction processes that impact the film morphology, optical emission spectroscopy (OES) and intensified charge-coupled device (ICCD) fast imaging technique were applied. The determined vibrational (Tvib) and rotational (Trot) temperatures exhibit a decrease with the introduction of monomer vapors into the discharge gap. For instance, Trot drops from approximately 475 K to 350 K, and Tvib falls from 2850 K to 2650 K for a monomer vapor injection rate of 16 µL/min. This was attributed to the energy losses of the plasma-generated particles, as the inelastic collisions augment with the injection of a monomer. Concurrently with the change in temperature, the discharge current varies significantly for the investigated frequency range and exhibits a drop at high frequencies. This discharge current drop was explained by an enhancement of the recombination rate of charged particles and seems to confirm the prevalence of a plasma-induced monomer fragmentation process at high frequencies.

Repetitive pulsed gas-liquid discharge in different atmospheres: from discharge characteristics to plasma-liquid interactions.

Gas-liquid discharges enable efficient plasma-liquid interactions and thus have promising applications, but many concerns remain unanswered regarding working gas, an important influencing factor. Investigations of a pulsed needle-to-water gas-liquid discharge in Ar, He, and N2 are carried out in this study. Voltage-current waveforms and intensified charge-coupled device (ICCD) images were combined to explore discharge modes and evolution processes. Experimental results demonstrate that the Ar tip spark discharge develops all the way to liquid compared with the He and N2 discharges concentrated in the tube, considerably increasing the plasma-liquid interaction efficiency. According to the optical emission spectra (OES), plasma properties are found to be strongly influenced by interactions between gas particles and interfering particles (H2O, etc.). For instance, excess water vapor causes quenching of excited species, resulting in OH (A-X) in Ar and NO (A-X) in N2 concentrated in the middle region with weak discharge. By adding dimethyl sulfoxide, it is demonstrated that OH dominates H2O2 production in Ar and contributes to both NO2- and NO3- generation in Ar and He, whereas in N2 it only affects NO3- generation. This study advances the "bridge building" between practical application and gas-liquid discharge employing different working gases.

Positive and negative streamers in air and nitrogen in a sharply inhomogeneous electric field under conditions of runaway electron generation

AbstractThe development of positive and negative streamers in a point‐to‐plane gap filled with air and nitrogen at various pressures (50–200 kPa) and voltages (8–25 kV) was studied. A four‐channel intensified charge‐coupled device (ICCD) and a streak‐camera were used. Electrical parameters were measured with high resolution (10 GHz). An original method of measuring a displacement current caused by a streamer was applied. As was expected, positive streamer branches in nitrogen at low voltages and/or elevated pressures while a large‐diameter streamer is formed in air. However, at high voltages or negative polarity, the large‐diameter streamer is formed both in nitrogen and air in the entire pressure range. It was found that runaway electrons (REs) are generated in the very first picoseconds of gas ionisation near the pointed cathode. It was assumed that REs can be generated near the pointed anode and produce bremsstrahlung radiation due to a sharply inhomogeneous distribution of electrical potential. It was found that in the final stage of negative streamer development in air and nitrogen, the gas between the streamer front and the opposite electrode is ionised almost simultaneously in the entire volume when the streamer diameter is almost equal to the interelectrode gap.

Raman detection system for in situ oxidation and ablation analysis in hypersonic wind tunnel

AbstractWe have developed a system for remote Raman spectra detection in hypersonic wind tunnel, which can be used in extreme environments such as ultra‐high temperature, high pressure, and complex airflow to measure in situ Raman spectra of ceramic matrix composites during oxidation, phase transformation or ablation. The designed system avoids stray light generated by windows and airflow through oblique incidence of excitation light. The time‐resolved method combined with pulsed laser and intensified charge‐coupled device (ICCD) was used to reduce the thermal emission background. An optical structure design based on fiber bundle is adopted to suppress the influence of aero‐optical effects and mechanical vibration on Raman spectrum acquisition. We demonstrated the feasibility of in situ Raman spectra detection in a Mach 5 combustion wind tunnel system. The design of anti‐interference prevents Raman spectra intensity from the influence of wind tunnel testing conditions.

Transmission and multiple reflection mechanisms of guided streamers propagating through grounded annular electrode and interacting with grounded surface electrode

The repeatable dynamics and the reversal propagation of guided streamers remains a major question of fundamental physics. In this article, trains of positive guided streamers are generated within an atmospheric pressure plasma jet supplied in helium and polarized by a high-voltage nanosecond pulse generator. The device is completed by two distant targets: a grounded annular electrode (GAEL) coaxially centered around the capillary through which guided streamers can propagate, and a grounded surface electrode (GSEL) on which they can interact. The resulting transmitted and multiple reflected guided streamers are measured combining optical characterization (fast intensified charge-coupled device (ICCD) imaging) and electrical characterization (high voltage probe and current monitors). While the electrical approach provides information on the capacitive/conductive nature of the current peaks as well as on their positive/negative value, fast ICCD imaging distinguishes whether the guided streamers are incident, reflected or transmitted. Combining these two techniques allow us to demonstrate experimentally that the reflected streamers are negative contrarily to the others. Besides, four types of reflections have been highlighted: a reflection (r) at the outlet of the capillary, a reflection on the GSEL (R) and two reflections (r′ and r″) observed when an incident guided streamer passes through the GAEL. The two techniques agree that the characteristic propagation times are always shorter for reflected negative streamers than for the positive ones propagating forward. Hence, for a GAEL placed 3 cm away from the high voltage electrode, propagation time is 80 ns for reflection versus 250 ns for transmission. These characteristic propagation times are even shorter when the annular electrode is brought closer to the surface electrode with velocities typically higher than 300 km s−1. In addition, the intensity ratios of reflected/incident guided currents drop sharply, typically losing one decade over a counter-propagation length of only 3–5 cm. Finally, all these experimental data are utilized to build an equivalent electrical model that allow to better understand the dynamics of the guided streamers and explain their transmission and reflection modes upon their interaction with the two distant grounded electrodes.

Influence of surface roughness on nanosecond laser-induced shock wave enhancement effects.

In this paper, an effective method is proposed for improving the energy of the shock waves that are generated by plasma expanding outward and colliding with another gas. Silicon targets are used as the response medium with roughness of 2.3 nm, 457.8 nm, 1.1 µm, and 37.1 µm, respectively. A 532-nm-laser with a pulse duration of 8 ns and a repetition rate of 10 Hz is used as the irradiation source. An intensified charge-coupled device (ICCD) is used to photograph the morphology of the shock waves. The time-resolved emission images of silicon plasma plumes are observed between 20-200 ns. As the surface roughness of the target increases, the intensity of the shock wave gradually increases, and the energy of the shock wave reaches up to 39.45 mJ at a roughness of 37.1 µm.

Temperature-dependent Raman spectra of KTaO3 crystal and melt along with its phonon and electronic properties

In situ high temperature Raman spectra of KTaO3 crystal and melt were measured over the wavenumber range of 100–1600 cm−1 from ambient temperature to 1723 K by intensified charge coupled device (ICCD) coupled with high temperature observational furnace. The band structure, density of states (DOS), phonon density of states (PDOS) and phonon dispersion of KTaO3 crystal were calculated by density functional theory (DFT). According to the theoretical calculation, strong covalence of Ta-O bonds and band gap were confirmed, phonon branch assignments for the second order Raman spectrum of KTaO3 crystal were made. A series of model clusters were constructed and their Raman spectra were simulated by DFT to determine the microstructures of KTaO3 melt. The relation between TaO bond lengths and characteristic Raman-active vibration wavenumbers of the molten KTaO3 has been investigated by which Raman spectrum of KTaO3 melt was deconvoluted by a sum of Gaussian peaks based on DFT results. Results showed that the lattice framework collapsed and the second order Raman peaks disappeared while the crystal being melt. Different from previous conclusion that there was only one type of TaO complex, a mixture of TaO anion complexes was proved to coexist in the molten KTaO3 while disproportionation equilibrium being reached, and those complexes were identified in this work.

Effect of HMDSO Addition on Discharge Characteristics and Uniformity of Nanosecond-Pulsed Plasma Jet Array

Atmospheric-pressure plasma jet (APPJ) array is considered as an efficient method to enlarge treatment and improve treatment efficiency. With the addition of precursors containing Si, the APPJ array can be used for improving the surface hydrophobicity and insulating performance of insulating materials. In this article, the influence of hexamethyl disiloxane (HMDSO) addition on the discharge characteristics and uniformity of a 1-D nanosecond-pulsed jet array in Ar has been investigated through electrical and optical methods. It is found that the addition of HMDSO in a small amount can promote the plume length, discharge power, transported charge, and emission intensity through the Penning effect. When the HMDSO content is higher than 0.04%, the discharge of jet array is weaken, especially the middle unit, which results in the decrease of the uniformity, plume length, discharge power, transported charge, and emission intensity. With the intensified charge-coupled device (ICCD) measurement of the ionization wave propagations of jet arrays in pure Ar, 0.04%, and 0.50% HMDSO, it shows that the 0.04% HMDSO enhances the spatial electric field strength in jet array and promotes plasma bullets propagation. However, more HMDSO addition reduces the space charges and plasma bullets propagation speed. The competition of Penning effect and electron absorption by the HMDSO addition results that the Ar jet array has maximum values of plume length, discharge power, transported charge, and emission intensity at 0.04% HMDSO content.

Development of a High-Energy X-ray Backlighting System for Z-pinch Experiments

A backlighting system is developed for Z-pinch experiments that is composed of a pulsed X-ray generator (the backlighter), a scintillator, an optical module, and an intensified charge-coupled device (ICCD). By optimizing the geometrical layout, choosing the appropriate scintillator, and optimizing the parameters of the optical module, the system is successfully designed. The key properties of the system are theoretically calculated based on parameters of the X-rays and the scintillator. Calculation results of sensitivity show that the amount of scintillator fluorescence falls in the linear dynamic range of the ICCD. Spatial resolution is calculated to be 241 µm, which is mainly determined by the geometrical layout and the size of the X-ray focal spot. Temporal resolution is calculated to be 2.3 ns, which is mainly determined by the decay time of the scintillator. Calculation results indicate that the properties of the system meet the requirements of the Z-pinch capsule diagnostics. The system has been fabricated. Performance of the system is tested through static W wire experiments in the laboratory. Experimental results show that 250-µm W wire is clearly seen in the image when X-ray fluence is high, while 100-µm W wire cannot be seen.

In vitro and in vivo NIR fluorescence lifetime imaging with a time-gated SPAD camera.

Near-infrared (NIR) fluorescence lifetime imaging (FLI) provides a unique contrast mechanism to monitor biological parameters and molecular events in vivo. Single-photon avalanche diode (SPAD) cameras have been recently demonstrated in FLI microscopy (FLIM) applications, but their suitability for in vivo macroscopic FLI (MFLI) in deep tissues remains to be demonstrated. Herein, we report in vivo NIR MFLI measurement with SwissSPAD2, a large time-gated SPAD camera. We first benchmark its performance in well-controlled in vitro experiments, ranging from monitoring environmental effects on fluorescence lifetime, to quantifying Förster resonant energy transfer (FRET) between dyes. Next, we use it for in vivo studies of target-drug engagement in live and intact tumor xenografts using FRET. Information obtained with SwissSPAD2 was successfully compared to that obtained with a gated intensified charge-coupled device (ICCD) camera, using two different approaches. Our results demonstrate that SPAD cameras offer a powerful technology for in vivo preclinical applications in the NIR window.

Distinguishing bacteria from minerals in a layered sample using time-resolved Raman spectroscopy and global analysis

Mars is one of the prime candidates in the search for extraterrestrial life. At the most comparable terrestrial Martian analogue sites, life often occurs in endolithic form; i.e. hiding below the surface. To detect biomarkers of endolithic life, the two most promising options are drilling or measuring through the surface, the latter being less invasive and preferable. Raman spectroscopy is an established chemical identification method, and advanced Raman modes have been developed for sub-surface analysis. Time-resolved Raman spectroscopy (TRRS), based on picosecond pulsed excitation and a gated intensified charge-coupled device (ICCD) detector, adds the capability of fluorescence suppression and depth selection. This paper focuses on the separation of layers with time differences that are much smaller than the full width at half-maximum gating time of the detector. As an analogue for endolithic life on Mars, Deinococcus radiodurans bacteria were measured through a and top layer of translucent calcite. TRRS spectra were recorded in a backscattering geometry, while stepwise increasing the detector delay in steps. Through both of these layers, the Raman spectrum of the bacteria’s carotenoids could be detected. Global analysis was used to model a complete time-resolved spectrum of the sample. Using this analysis, the signals could be separated into three components: mineral Raman, bacterial Raman and bacterial fluorescence. The model also corrects for gating differences across the horizontal axis of the ICCD camera. With this approach well-separated Raman spectra were obtained even for the calcite layer despite the temporal separation of approximately , which is much shorter than the detector gating time. TRRS could be a suitable approach for non-invasive detection of extraterrestrial subsurface biomarkers.