Measurements Of Radial Profiles Research Articles

Conceptual design of visible spectroscopy diagnostics for DTT

The project of the Visible Spectroscopy diagnostics for the Z eff radial profile measurement and for the divertor visible imaging spectroscopy, designed for the new tokamak DTT (Divertor Tokamak Test), is presented. To deal with the geometrical constraints of DTT and to minimize the diagnostics volume inside the access port, an integrated and compact solution hosting the two systems has been proposed. The Z eff radial profile will be evaluated from the Bremsstrahlung radiation measurement in the visible spectral range, acquiring light along ten Lines of Sight (LoS) in the upper part of the poloidal plane. The plasma emission will be focused on optical fibers, which will carry it to the spectroscopy laboratory. A second equipment, with a single toroidal LoS crossing the plasma centre and laying on the equatorial plane, will measure the average Z eff on a longer path, minimizing the incidental continuum spectrum contaminations by lines/bands emitted from the plasma edge. The divertor imaging system is designed to measure impurity and main gas influxes, to monitor the plasma position and kinetics of impurities, and to follow the plasma detachment evolution. The project aims at obtaining the maximum coverage of the divertor region. The collected light can be shared among different spectrometers and interferential filter devices placed outside the torus hall to easily change their setup. The system is composed of two telescopes, an upper and a lower one, allowing both a perpendicular and a tangential view of the DTT divertor region. This diagnostic offers a unique and compact solution designed to cope the demanding constraints of this next-generation tokamak fusion devices, integrating essential tools for wide-ranging impurity characterization and versatile investigation of divertor physics.

High-Spatial-Resolution Coherent Doppler Lidar With Pseudo-Random Phase-Shift Keying

A high-spatial-resolution coherent Doppler wind lidar (CDWL) incorporating pseudo-random phase-shift keying (PR-PSK) modulation is proposed and demonstrated. The pseudo-random phase coding technique can enhance the spatial resolution without broadening the backscattered spectrum but suffers from the non-instantaneous transition edges caused by the limited bandwidth. In this work, ideal binary PSK modulation is achieved by exploiting the zero crossing of the Mach-Zehnder modulator’s (MZM) transfer function, thus greatly reducing the bandwidth requirement. The amplitude shaping and phase modulation of the pulses are naturally aligned as they are realized together in one MZM. Meanwhile, a real-time bias monitoring scheme for the MZM is proposed to facilitate engineering applications. At laser peak power of 300 W, continuous radial wind profile measurement in 800 m is demonstrated, with spatial/temporal resolution of 3 m/0.5 s.

High resolution Thomson scattering diagnostic for measurements of radial profiles of electron temperature and density in the gas dynamic trap.

The incoherent Thomson scattering diagnostic with multiple lines of sight is installed at the gas dynamic trap (GDT) for measurements of radial profiles of the plasma electron temperature and density. The diagnostic is built on the Nd:YAG laser operating at 1064nm. The laser input beamline is provided with an automatic system for alignment status monitoring and correction. The collecting lens uses ∼90° scattering geometry having 11 lines of sight in total. Presently, six of them (covering the full plasma radius from the axis to the limiter) are equipped with high etendue (f/2.4) interference filter spectrometers. The design of the spectrometer's data acquisition system based on the "time stretch" principle allowed for the 12 bits vertical resolution with a sampling rate of 5 GSample/s and a maximum sustainable measurement repetition frequency of 40kHz. The repetition frequency is the crucial parameter for the study of plasma dynamics with a new pulse burst laser to be started in early 2023. Results of the diagnostic operation in several GDT campaigns show that radial profiles are routinely delivered with the typical observation error of 2%-3% for Te ⩾ 20eV in a single pulse. After Raman scattering calibration, the diagnostic is capable to measure the electron density profile with the resolution ne (min)≃4⋅1018m-3 and error bars of 5%.

Performance improvement of space-resolved extreme ultraviolet spectrometer by use of complementary metal-oxide semiconductor detectors at the Experimental Advanced Superconducting Tokamak.

Two pairs of space-resolved extreme ultraviolet (EUV) spectrometers working at 5-138 Å with different vertical observation ranges of -7 ≤ Z ≤ 19 and -18 ≤ Z ≤ 8cm have been newly developed to observe the radial profile of impurity line emissions and to study the transport of high-Z impurity ions intrinsically existing in EAST tokamak plasmas. Both spectrometers are equipped with a complementary metal-oxide semiconductor (CMOS) detector (Andor Marana-X 4.2B-6, Oxford Instruments) with sensitive area of 13.3 × 13.3mm2 and number of pixels equal to 2048 × 2048 (6.5 × 6.5 µm2/pixels). Compared to the currently operating space-resolved EUV spectrometers with a charge-coupled detector (CCD: 1024 × 255 pixels, 26 × 26 µm2) working at 30-520 Å, this spectrometer's performance was substantially improved by using the CMOS detector. First, the spectral resolution measured at full width at half maximum was improved in the whole wavelength range, e.g., Δλ1/2_CMOS = 0.092 Å and Δλ1/2_CCD = 0.124 Å at C VI 33.73 Å and Δλ1/2_CMOS = 0.104 Å and Δλ1/2_CCD = 0.228 Å at Mo XXXI 115.999 Å, thus enabling a more accurate analysis of spectra with complicated structure such as tungsten unresolved transition array in the range 45-65 Å. Second, the temporal resolution was largely improved due to the high-speed data acquisition system of the CMOS detector, e.g., Δt_CMOS = 15 ms/frame and Δt_CCD = 200 ms/frame at routine operation in the radial profile measurement. Third, signal saturation issues that occurred when using the old CCD sensor during impurity accumulation now disappeared entirely using the CMOS detector due to lower exposure time at high readout rates, which largely improved the observation performance in similar impurity burst events. The above-mentioned performance improvements of the space-resolved EUV spectrometer led to a rapid change in the W XXXIII (52.22 Å) radial profile during a single cycle of low-frequency sawtooth oscillation with fst = 5-6Hz at a sufficient detector count rate.

High Resolution Coherent Doppler Wind Lidar Incorporating Phase-Shift Keying

A coherent Doppler wind lidar (CDWL) with spatial/temporal resolution of meter and sub-second scale is reported. Phase-shift keying (PSK) is introduced into the pulse pair to enhance the measurement efficiency, and the pulse shaping and perfect binary PSK modulation are both realized by a single Mach-Zehnder modulator (MZM). The identical intensity envelope of the paired pulses reduces the influence of amplifier's gain profile and provides a monitoring parameter for bias control, which improves the system stability in practice. Theoretical analysis and numerical simulation are conducted to illustrate the principle of the proposed method. In experiments, the bias drift of the MZM is monitored in real time. Continuous radial wind profile measurement over 800 m is demonstrated with spatial and temporal resolution of 3 m and 0.1 s, respectively.

1.8 m/0.5 s Resolution Coherent Doppler Wind Lidar Using Continuous Phase Modulation

A high-spatial-resolution coherent Doppler wind lidar (CDWL) with high modulation efficiency is reported. The pseudo-random phase coding (PRPC) links the spatial resolution to the modulation rate but suffers from the non-rectangular transition caused by the limited bandwidth. With the help of continuous phase modulation (CPM), the abrupt phase switching between successive bit intervals is avoided, thus significantly reducing the bandwidth requirement. By mapping the binary sequence into different transition states rather than phase levels, a 10-fold modulation efficiency improvement is realized. In experiments, the performance of the proposed lidar is compared with lidars in the PRPC method and conventional non-coding method. Continuous radial wind profile measurement of 800 m is demonstrated with spatial and temporal resolution of 1.8 m and 0.5 s, which is the highest spatial resolution realized by a pulsed CDWL to our best knowledge.

Turbulence, coherence, and collapse: Three phases for core evolution

ABSTRACT We study the formation, evolution, and collapse of dense cores by tracking structures in a magnetohydrodynamic simulation of a star-forming cloud. We identify cores using the dendrogram algorithm and utilize machine learning techniques, including Neural Gas prototype learning and Fuzzy c-means clustering to analyse the density and velocity dispersion profiles of cores together with six bulk properties. We produce a 2-d visualization using a Uniform Manifold Approximation and Projection (UMAP), which facilitates the connection between physical properties and three partially-overlapping phases: i) unbound turbulent structures (Phase I), ii) coherent cores that have low turbulence (Phase II), and iii) bound cores, many of which become protostellar (Phase III). Within Phase II, we identify a population of long-lived coherent cores that reach a quasi-equilibrium state. Most prestellar cores form in Phase II and become protostellar after evolving into Phase III. Due to the turbulent cloud environment, the initial core properties do not uniquely predict the eventual evolution, i.e. core evolution is stochastic, and cores follow no one evolutionary path. The phase lifetimes are 1.0 ± 0.1 × 105 yr, 1.3 ± 0.2 × 105 yr, and 1.8 ± 0.3 × 105 yr for Phase I, II, and III, respectively. We compare our results to NH3 observations of dense cores. Known coherent cores predominantly map into Phase II, while most turbulent pressure-confined cores map to Phase I or III. We predict that a significant fraction of observed starless cores have unresolved coherent regions and that ≳20 per cent of observed starless cores will not form stars. Measurements of core radial profiles in addition to the usual bulk properties will enable more accurate predictions of core evolution.

Spatial Resolution Enhancement of Coherent Doppler Lidar by Pseudo-Random Phase Coding

A high spatial resolution coherent Doppler wind lidar (CDWL) incorporating pseudo-random phase coding (PRPC) is proposed and demonstrated. Random phase coding of the transmitted lightwave spreads the atmospheric backscattered spectrum and the spatial resolution can be enhanced as only the signal with specific time delay could be despread during decoding. The narrow peak of the despread spectrum provides higher wind velocity retrieval accuracy compared with conventional pulsed CDWL with the same spatial resolution. Spectrum difference is applied to reduce the interference between the spread and despread spectra. The new method's performance is verified in a comparison experiment with a non-coding CDWL. Continuous radial wind profile measurement over 800 m is demonstrated with spatial/temporal resolution of 4.5 m/1 s, at laser peak power of 250 W.

Measurement and evaluation of wheel profiles of a rail vehicle on an underfloor wheelset lathe

Wheel profile form directly affects the dynamic behaviour of rail vehicles. Moreover, it is an important factor to ensure the safe running of a high-speed vehicle. As off-line measurements do not provide high-efficiency and high-accuracy wheel profile measurements, we focused on on-machine measurement and evaluation for obtaining the wheel profiles of a rail vehicle in this study. By combining the wheel machining with the wheel measurement, the measurement and evaluation of radial and axial wheel profiles on the underfloor wheelset lathe were proposed. The measurement of radial wheel profile based on two laser sensors was introduced, and the corresponding error models of on-machine measurement were established. The error models were used to separate the measurement errors from the measurement data. This can improve the accuracy of measuring the radial wheel profile effectively. For measuring the axial wheel profile, an adaptive correction method of profile error was proposed to suppress the measurement error, which was the basis for obtaining an accurate equivalent conicity. By measuring radial and axial wheel profiles, polygonisation evaluation and equivalent conicity were obtained to evaluate the radial and axial dynamic behaviours of a wheelset, respectively. Finally, the measurements were applied to an underfloor wheelset lathe to verify the effectiveness of measuring wheel profiles. In this study, we not only improved working efficiency for the machine tools, but also provided a high-accuracy measurement method for the wheel profiles of rail vehicle.

Confirmation of the Absence of Contact Between Edge Boundary Plasma and Inboard First Wall in LHD Discharges Based on Radial Profile Measurement of Hβ Line Emissions

In the Large Helical Device (LHD), a high-performance plasma has been obtained at the inwardly shifted magnetic axis position of Rax = 3.60 m in which a spatial distance between the first wall on the vacuum vessel and the outermost edge boundary of the stochastic magnetic field layer existing outside the last closed flux surface takes a minimum value of ~12 mm at the inboard side. In order to investigate contact between the edge plasma boundary and the inboard first wall, a radial profile of Hβ line emissions at 4861 Å has been measured using a Czerny-Turner visible spectrometer and a 40-channel optical fiber array. All Hβ profiles measured at different magnetic axis positions of Rax = 3.60, 3.75, and 3.90 m showed a centrally peaked profile except for a few fiber channels observing the outboard edge plasma. The Hβ emission near the inboard first wall was negligibly weak, in particular, in the case of Rax = 3.60 m, suggesting no significant contact between the edge boundary plasma and the vacuum vessel first wall. The radial Hβ profile was then analyzed in detail using the EMC3-EIRENE edge plasma simulation code. The simulation well reproduced the measured profiles, including the extremely weak Hβ emission around the inboard first wall in the Rax = 3.60 m configuration. The centrally peaked profiles are found to originate in the Hβ emissions around X-points, while hydrogen neutrals are dominantly localized near the divertor plates. These results confirm the formation of a complete open divertor configuration in the LHD discharge without significant contact with the first wall. The presence of a region with extremely short magnetic field connection lengths (Lc < 5 m) between the inboard first wall and the outermost edge boundary is a key point to eliminate the strong plasma-wall interaction because sustainment of a significant edge plasma is entirely difficult in such a low Lc region.

Measurements of near-surface radial profiles of electrophysical characteristics of cylindrical objects by the eddy current method using a priori data

A new multiparameter express method for eddy-current measurement of radial near-surface profiles of electrophysical parameters of cylindrical control objects with a priori accumulation of information about them is proposed. The method combines in-situ measurements and model calculations using high-performance computing technologies of artificial intelligence based on neural networks, carried out both in advance in order to obtain specific information about objects, and directly in the process of performing measurements to quickly obtain a result. Mathematically, the method is based on the unique ability to quickly solve Maxwell's equations as a result of its approximation by deep neural networks without actually explicitly executing this solution. This allows deep learning to be used not only in the forward direction, but also in the opposite direction, i.e. apply to solve inverse measuring problems. The method is universal and can be extended to multiparameter measurement control with simultaneous additional determination of the diameter of a cylindrical object. The adequacy of the proposed method by numerical experiments is proved; examples of the implementation of all stages of its application are given. Algorithms and a complex of programs in the Python 3 environment have been created, which make it possible to practically implement the method. The profile measurement accuracy established on model calculations is characterized by maximum relative errors not exceeding 0.5%, provided that the probe signal is perfectly fixed. It is possible to generalize the use of the proposed method to similar eddy current measurements with surface probes of profiles of material parameters of flat objects.

Physics studies of ADITYA & ADITYA-U tokamak plasmas using spectroscopic diagnostics

Several spectroscopic diagnostics encompassing the spectral emission range from the x-ray to near infrared (NIR) have been developed, installed and operated for diagnosing and physics studies in the ADITYA and ADITYA-U tokamaks. The recycling and impurity influxes and plasma Z eff after lithium (Li) coating have been studied using a PMT (photomultiplier tube)-filter based system by capturing H α , O1+, C2+, and visible continuum emissions. Significant reduction in the Z eff values has been observed in the discharge with the Li coated walls. The measured radial profile of H α emission using a filter-PMT array, has been modelled using a neutral transport code. The results show substantial contributions from the molecular hydrogen and molecular hydrogen ion dissociation (∼56%) and charge-exchange (∼30%) processes in the measured H α emission. Furthermore, a high-resolution, 1 m spectrometer with charge coupled device detector capable of multi-track measurements, has been used to study impurity transport, neutral and ion temperature and intrinsic plasma rotation. By modelling the measured radial profile of O4+ spectral line emission using an impurity transport code, substantial contribution of edge fluctuations on the oxygen transport has been observed. The toroidal ( ∼ 20 km s−1 in core) and poloidal ( ∼ 4.5 km s−1 at edge) rotation velocities are measured using C5+ (529 nm) and C2+ (464.7 nm) passive line emissions respectively. The measurement of radial profile of toroidal plasma rotation revealed a reversal of rotation direction depending on the electron density content of the ADITYA-U plasmas. The neutral temperature measurements showed a poloidal asymmetry indicating a presence of asymmetrical source of neutral heating. Moreover, the modelling of measured Fe14+ and Fe15+ vacuum ultraviolet spectral lines has revealed the neo-classical nature of iron transport in ADITYA core. Fast visible camera images captured the formation of filament structures triggered by interchange instabilities during plasma disruptions.

The impact of the presence of water ice on the analysis of debris disk observations

Context. The analysis of debris disk observations is often based on the assumption of a dust phase composed of compact spherical grains consisting of astronomical silicate. Instead, observations indicate the existence of water ice in debris disks. Aims. We quantify the impact of water ice as a potential grain constituent in debris disks on the disk parameter values estimated from photometric and spatially resolved observations in the mid- and far-infrared. Methods. We simulated photometric measurements and radial profiles of debris disks containing water ice and analyzed them by applying a disk model purely consisting of astronomical silicate. Subsequently, we quantified the deviations between the derived and the true parameter values. As stars in central positions we discuss a β Pic sibling and main-sequence stars with spectral types ranging from A0 to K5. To simulate observable quantities we employed selected observational scenarios regarding the choice of wavelengths and instrument characteristics. Results. For the β Pic stellar model and ice fractions ≥50% the derived inner disk radius is biased by ice sublimation toward higher values. However, the derived slope of the radial density profile is mostly unaffected. Along with an increasing ice fraction, the slope of the grain size distribution is overestimated by up to a median factor of ~1.2 for an ice fraction of 90%. At the same time, the total disk mass is underestimated by a factor of ~0.4. The reliability of the derived minimum grain size strongly depends on the spectral type of the central star. For an A0-type star the minimum grain size can be underestimated by a factor of ~0.2, while for solar-like stars it is overestimated by up to a factor of ~4–5. Neglecting radial profile measurements and using solely photometric measurements, the factor of overestimation increases for solar-like stars up to ~7–14.

The NIKA2 Sunyaev-Zeldovich Large Program: Precise galaxy cluster physics for an accurate cluster-based cosmology

The NIKA2 Guaranteed-Time SZ Large Program (LPSZ) is dedicated to the high-angular resolution SZ mapping of a representative sample of 45 SZ-selected galaxy clusters drawn from the catalogues of the Planck satellite, or of the Atacama Cosmology Telescope. The LPSZ sample spans a mass range from 3 to 11 × 1014M⊙ and a redshift range from 0:5 to 0:9, extending to higher redshift and lower mass the previous samples dedicated to the cluster mass calibration and universal properties estimation. The main goals of the LPSZ are the measurement of the average radial profile of the ICM pressure up to R500 by combining NIKA2 with Planck or ACT data, and the estimation of the scaling law between the SZ observable and the mass using NIKA2, XMM-Newton and Planck/ACT data. Furthermore, combining LPSZ data with existing or forthcoming public data in lensing, optical/NIR or radio domains, we will build a consistent picture of the cluster physics and further gain knowledge on the mass estimate as a function of the cluster morphology and dynamical state. We give an overview of the LPSZ, present recent results and discuss the future implication for cosmology with galaxy clusters.

Measurements of radial profile of isotope density ratio using bulk charge exchange spectroscopy.

A bulk charge exchange spectroscopy (BCXS) system using a grism (grating prism) spectrometer has been applied to measure the profile of the deuterium (D) fraction in deuterium and hydrogen (H) mixture plasma in the Large Helical Device. The observed spectrum can be fitted with four Gaussian functions successfully by reduction of free parameters for the least-squares fit. The plasma flow velocity and ion temperature profile measured by charge exchange spectroscopy using carbon impurity are used for estimation of the wavelength shift of hot components to reduce the free parameter. The ion temperature is used to estimate the apparent wavelength shift due to the energy dependent emission cross section only and is not used to set the Doppler width for H and D in the fitting. The sensitivity of the evaluated D fraction on the velocity is increased for a higher D fraction. The error of the D fraction is calculated from the error in the fitted parameter and sensitivity on the velocity of the hot component. The difference in the profile and time trace of the D fraction with D pellet and H pellet injection was observed clearly by BCXS using a grism spectrometer.

Development of a Langmuir probe array for radial potential profile measurement in the collisional merging formation FRC.

The radial electric field in a field-reversed configuration (FRC) plasma plays an important role in the global stability and confinement properties. Herein, we developed a new Langmuir probe array named "Skewered probe" employed in measuring the radial potential profile in the collisional merging formation of an FRC in the FAT-CM (FRC Amplification via Translation - Collisional Merging) device. Because an FRC has a strong toroidal flow, the skewered probe consists of alternately skewered ring electrodes and ceramic beads on a thin stainless-steel tube to neutralize the effect of plasma flow. The developed array has nine electrodes, one every 2cm from r = 9-25cm, and it measures the FRC boundary in the case when the radius of the excluded flux ranges from 10 to 20cm. The skewered probe also has one additional electrode that measures the potential near the chamber wall as a reference for the other electrodes. The radial potential profile of the FRC formed by the collisional merging method in the FAT-CM device was measured using the probe, and the results showed that the region of negative potential gradually changed to a positive potential after merging the FRCs. It was also shown that a strong outward electric field is formed near the separatrix at n = 2 rotational instability.

Radial profile measurement with an improved 1 kHz Thomson scattering system on Versatile Experiment Spherical Torus.

A Thomson scattering (TS) system has been utilized to measure the electron temperature and density of the core region of Versatile Experiment Spherical Torus (VEST). Recently, the laser injection system is successfully upgraded adopting the burst laser with the repetition rate of 1 kHz and the energy of 2J. Furthermore, improved collection optics with additional polychromators and a 32-channel fast digitizer are prepared to observe the fast time evolution of radial profiles. This improvement is essential to study fast phenomena such as internal reconnection event (IRE). We increase the TS signal and reduce the stray light by introducing new filters having better optical properties such as high optical density at 1064nm, transmission, and reflectance. Moreover, the optimum reverse bias voltages are newly set to make the system operational independent of the background radiation. As a result, 1 kHz radial profiles of the core electron temperature and density are measured for the first time, showing characteristics of IREs in VEST.

Fast-ion D alpha diagnostic with 3D-supporting FIDASIM in the Large Helical Device

For understanding the physics of energetic particles, the deuterium experimental campaigns started in Large Helical Device (LHD) from March 2017. To investigate the behavior of energetic particles, a Fast-ion D Alpha (FIDA) diagnostic was installed on the LHD. In the FIDA diagnostic, the Doppler-shifted D alpha light from fast-neutrals are utilized as signals of energetic particles, where these fast-neutrals are produced by the charge exchange process between fast-ions in the plasma and actively injected neutrals by neutral beam (NB). The advantages of the FIDA diagnostic are the velocity and the spatially resolved measurement of fast-ions at the crossing point between its line of sight (LOS) and the incident line of NB. The most recent FIDASIM is enhanced to simulate signals produced in three-dimensional magnetic configurations. The new version of FIDASIM uses the fast-ion distribution function produced by GNET as input to simulate FIDA signals at LHD. In order to validate the new version of the code, measurements of radial profiles of fast-ions using the FIDA diagnostic are performed in magnetohydrodynamic (MHD)-quiescent plasmas. The measured spectra are in good agreement with the theoretical prediction by 3D-supporting FIDASIM at the center of the plasma (R= 3.5 m∼3.7 m, reff/a99= −0.28∼0.05) on the LHD when the line averaged electron density is ne_avg < 1.23 × 1019 m−3. On the other hand, the measured spectra are in disagreement with the theoretical prediction by 3D-supporting FIDASIM at even the center of the plasma when the line averaged electron density is ne_avg ≥ 1.23 × 1019 m−3.

Terrella for advanced undergraduate laboratory

A terrella developed for the undergraduate Advanced Laboratory course in the University of Wisconsin-Madison Physics Department is described. Our terrella consists of a permanent magnet, mounted on a pedestal in a vacuum chamber, surrounded by electrodes that may be biased in various ways. The system can confine a plasma, which may, in some ways, be considered as a toy model of the plasma confined in the Earth's magnetosphere. Our axisymmetric plasma forms in a region where the magnitude of the magnetic field B is 14 G ≤B≤ 550 G; for typical operation, the neutral gas pressure is p∼10−4 Torr. The plasma is created by thermionic emission from a hot filament. Available diagnostics are a swept Langmuir probe, a spectroscopic fiber and visible-wavelength spectrometer, and visible imaging. In two four-hour laboratory sessions, students are guided through vacuum pumpdown, connection of electrical circuits, establishment of plasma, acquisition of data, analysis of data, and critique of data. In this paper, we present student measurements of radial profiles of electron temperature Te and density ne as well as imaging of mirror trapping and ∇B drift and curvature drift. We conclude by outlining some opportunities for additional terrella-based student experiments.

Numerical simulation of trickle bed reactors for biological methanation

Biological methanation in trickle bed reactors is an auspicious approach to convert hydrogen and carbon dioxide into methane. In order to analyze this process, a comprehensive CFD model was implemented including multiphase flow, absorption, and reaction phenomena. The model is based on the Eulerian-Eulerian method. Experimental investigations and literature data serve as its validation. The experiments focused on the hydrodynamics of a trickle bed composed of clay granulate and the applied reactor enabled detailed measurements of radial liquid flow profiles and liquid holdup dependent on the overall volume flow rate. The simulation of liquid dispersion confirms the experimental results regarding averaged macroscopic fluid flow. However, liquid holdup is slightly underestimated by the computational model. In addition to the hydrodynamic investigation, simulation of biological methanation provide insight into mutual interactions between multiphase flow and biochemical conversion and present a methane production rate on the same order of magnitude as literature values.