A new method is presented for the analysis of coherent mode activity, using tomographic reconstruction of the soft x-ray emissivity of the plasma. The analysis includes the determination of the mode frequency, the poloidal mode number, the radial location, the propagation direction, and the ballooning character. The parameters of a constructed mode are fitted to the line-integrated frequency-filtered soft x-ray signals of the 360 photodiodes installed in the Wendelstein 7-X (W7-X) stellarator. Artificial line-integrated photodiode signals, based on experiment-relevant parameters, are used to explain the workflow of the mode analysis. It is demonstrated that the mode parameters can be successfully reconstructed, even for modes at or near the noise level of the measurements. The method is applied to experimental measurements on W7-X, where strong coherent mode activity has been observed in the frequency space during a phase with a core plasma beta of β0 = 4.8%. The mode analysis indicates an m = 14 ± 2 mode whose characteristics agree with kinetic ballooning modes that can be destabilized at high β.

Abstract Wendelstein 7-X (W7-X) nominally operates at a magnetic field of 2.5T, but operation at a lower magnetic field strength is desired. The electron cyclotron resonance heating (ECRH) system of W7-X operates at 140GHz, corresponding to second harmonic (X2) heating at 2.5T, but also allows for heating at the third harmonic with a vacuum magnetic field around 1.7T to 1.8T. However, plasma start-up is not possible with X3-heating. Therefore one of the gyrotrons was tuned down to 101GHz for an X2 breakdown of the plasma at 1.8T on the magnetic axis. The available power in the plasma vessel for this detuned gyrotron is only 250kW with a pulse length of the order of 50ms. For this reason a multi-pass scenario was designed with six passes close to the magnetic axis to increase the effective power in the first few milliseconds during the breakdown. During the short 101GHz gyrotron pulse, this X2 multi-pass scenario creates a small plasma with temperatures up to several keV and line integrated densities around 8*10^18m^-2. It could also be shown that the multi-pass scenario is necessary to achieve plasma breakdown within 50ms. The plasma can be taken over by two sources of the neutral beam injection (NBI), starting at the same time as the detuned gyrotron to increase temperature and density. After about 1.5s at least 3MW of X3 ECRH are needed to take over from the NBI to maintain a stable plasma. This enables the low field operation of W7-X.

This work analyses vacuum magnetic field topology in Wendelstein 7-X (W7-X) with respect to changes in the current in the superconducting coils. We develop a fast automated scheme to locate fixed points (such as X- and O-points) and calculate the trace of the Jacobian of the field line map for them ( $\mathrm{Tr}(\text{M})$ ), which represents several important properties of the fixed point. We perform two sets of coil current scans: (i) scans where each coil current is varied individually, using the ‘standard’, ‘high iota’ and ‘low iota’ configurations as starting points; (ii) a scan of over $2\times 10^5$ magnetic configurations in which the coil currents are randomly sampled. In both cases, we constrain the coil currents to the normal range of W7-X. We verify the principal roles of the non-planar, planar and control coils: the non-planar coils establish island chains with a certain phase; the planar coils modify the location of the island chain by both controlling the $\iota$ profile and shifting the configuration ‘inward’ and ‘outward’; the control coil affects the island size and phase. We also find that $\vert (\mathrm{Tr}(\text{M})-2)\vert$ (a quantity closely related to the magnitude of the Greene’s residue) tends to increase with the minor radius of the fixed points, and that $\mathrm{Tr}(\text{M})$ for X- and O-points can be very differently affected by the control coil current. Finally, we show that $\vert (\mathrm{Tr}(\text{M})-2)\vert$ serves as a proxy for island size for internal island chains, which may help identification of suitable experimental candidates.

A low-noise, high-speed optical detector module is characterized and successfully commissioned for the measurement of high-frequency, low-intensity beam emission on Wendelstein 7-X (W7-X). An ultra-narrow bandpass optical filter is employed to selectively transmit the desired emission line while suppressing broadband plasma background emissions. Carbon density fluctuations are investigated by observing the carbon C-VI emission line (n = 8 → 7, λ ∼ 529nm), arising from charge exchange (CX) between the neutral beam atoms and the intrinsic carbon population. We present the characterization of the optical detector module and experimental measurements of carbon density fluctuations using available fibers on W7-X. The initial performance of the detector is presented in both active and passive CX measurements of intrinsic carbon density fluctuations. The low frequency dynamics of fluctuation is observed in response to the neutral beam and the pellet injection, demonstrating that the optical detector module is capable of providing a sufficient signal level with an adequate signal-to-noise ratio. In the upcoming OP2.4 campaign, this optical detector module will be adapted for use in a beam emission spectroscopy system by replacing the optical bandpass filter with one centered at 654nm (90% transmission: 653-655.3nm), which facilitates two-dimensional measurements of ion gyro-scale turbulence on W7-X.

Abstract The Wendelstein 7-X (W7-X) aims to demonstrate that the HELIAS line of stellarators can achieve high power and high performance under steady-state conditions. Such a scenario makes stellarators attractive candidates for fusion reactors offering potentially lower operating costs for continuously operated power plants. Therefore, a number of experiments have been performed at W7-X to demonstrate long-pulse operation. During the operational phase 1.2 (OP1.2) at W7-X, which took place in 2017–2018, a 100 s discharge with attached divertor plasmas was achieved, while the detached conditions were sustained for about 27 s. Performed experiments showed that a robust detachment scenario allows to reduce the peak heat flux by almost an order of magnitude and no significant increase of impurity concentration was observed (with Z eff < 1.5). The pulse duration was limited by the thermal limits of inertially (non active) cooled carbon divertor configuration. In operational phase OP2.1, the installation of a new actively water-cooled carbon-fiber composite divertor allowed a significant extension of pulse operation. The longest attached discharge lasted 8 min reaching 1.3 GJ energy throughput. In this experiment, attached plasma was heated with an average of 2.7 MW of ECRH power. The longest detachment phase in OP2.1 was achieved with feed-forward Ne seeding, which kept peak heat flux at the very low level, almost everywhere below 0.5 MW m −2 . As a consequence, no significant increase of impurity concentration occurs with the cooler plasma boundary, and the Z eff stayed below 2. The spectroscopic observation confirms that there is no Ne accumulation in the plasma core, which is an important prerequisite for steady-state high power plasmas.

Abstract A novel optical gas analyser, designed for isotope-resolved exhaust composition measurement, was field-tested at Wendelstein 7-X (W7-X) to validate its laboratory-proven concept under operational fusion experiment conditions. The system, Optix, comprises a cold cathode remote plasma generator and a high-resolution Fabry–Perot spectrometer and was deployed in the exhaust line of W7-X during the OP2.3 campaign. The injection of 3 He and 4 He for minority ion-cyclotron heating provided a test case for helium isotope discrimination. Despite limitations due to background gas and low partial pressures of the target species, isotope-resolved spectral signatures were successfully observed, demonstrating the fundamental viability of the Optix approach. Additionally, the spectrometer was evaluated for plasma emission measurements from both core and edge sightlines. While helium line emission was detectable, interpretation was hindered by complex background signals, highlighting the benefits of controlled remote plasma generators for spectroscopy. This first deployment provides critical insight into pressure requirements, spectral resolution, and operational constraints, informing future applications of optical exhaust diagnostics in fusion devices.

Abstract We present the first gyrokinetic simulations of multiscale turbulence in a stellarator, using the magnetic geometry of Wendelstein 7-X (W7-X) and experimentally relevant parameters. A broad range of scenarios is explored, including regimes where electron-temperature-gradient (ETG) turbulence coexists with varying levels of ion-temperature-gradient (ITG) turbulence, as well as cases involving microtearing modes (MTMs) relevant to high- β and reactor-like conditions. Notably, while ETG turbulence does not form radial streamers as in tokamaks, it can still drive significant transport and interact with ion-scale turbulence. In electrostatic ITG-dominated regimes, electron-scale fluctuations erode zonal flows, enhancing ion-scale transport, while ion-scale turbulence suppresses ETG activity. In contrast, under electromagnetic MTM conditions, the isotropic nature of ETG turbulence limits its suppressive effect, allowing MTMs to persist. These findings underscore the critical role of cross-scale effects for accurate transport predictions in W7-X and future stellarators.

A frequency modulated continues wave (FMCW) reflectometry with heterodyne detection has been developed for electron density profile measurement in front of the ion cyclotron resonance heating (ICRH) antenna on Wendelstein 7-X (W7-X). The dual-band setup consists of one band at E-band (60–90 GHz) and another at W-band (75–110 GHz), enabling measurements of local density at two different poloidal positions. The system is polarized in the extraordinary mode (X-mode), corresponding to a measurable density of at a central magnetic field of = 2.5 T. The transmission line includes an oversized Ka-band (WR28) waveguide in vacuum, which is tapered to a fundamental waveguide at E-band or W-band, respectively. Two pairs of sectoral horn antennas are mounted between the ICRH antenna straps. The horn mouth is designed to maintain the E-plane at the Ka-band dimension, while the elongated H-plane is customized to achieve sufficient gain and directivity. In this paper, the layout of the front-end and the design of electronic module are presented. Furthermore, the evaluated density profiles from the experiments show good agreement with profiles measured by other diagnostics, such as Alkali beam emission spectroscopy (ABES). Additionally, the density profile inside the magnetic island is presented. This diagnostic will be operated routinely for density profile measurements and will contribute to related physical study on W7-X.

Rayleigh scattering is used in an in-situ approach to determine the relative and absolute calibration factors of the Thomson scattering diagnostic at Wendelstein 7-X (W7-X). Using light pulses from an optical parametric oscillator (OPO), it is shown for the first time that the method is allowing for the calibration of all spatial channels (scattering volumes) at once. That has been realized by reducing the high amount of stray light observed in prior attempts. The improved setup is presented and compared to the literature ones.The Rayleigh scattering evaluation is containing the vacuum stray light measurement, which is yielding a rough estimate of the relative calibration without the need of any gas and used for background subtraction and a Rayleigh measurement on argon inside the vessel. The pressure dependency of the Rayleigh contribution in argon is evaluated for two wavelengths in each spectral channel. At the pressure of 377 mbar, the full spectral measurement used for the calibration is recorded. Under the assumption of the typical Rayleigh scattering cross-section from literature, the relative and absolute calibration factors are estimated. While the in-situ Rayleigh relative calibration and the conventional relative calibration mostly agree within the error bars, the absolute calibration is too high by a factor of roughly 3. Variations between different scattering volumes need further investigation and probably make additional improvements of the setup necessary. However, the general suitability of the method as absolute calibration is confirmed.

Abstract In Wendelstein 7-X (W7-X), future campaigns will include H, D and He as both NBI injection and target plasmas but, so far, only H injection and target plasmas have been extensively performed. The species effect on the beam-ion confinement and associated power loads has been studied with the ASCOT code to estimate the location and intensity of the hot spots. For this analysis, standard, high and low mirror configurations were considered to provide results covering the variation of the mirror term most likely to affect the beam-ion behaviour. Beam-ion losses were highest for D beams and lowest for He beams. Changing the target plasma from hydrogenic species to helium also produced higher losses. Hot-spot analysis showed peak loads up to 3 MW m −2 for D beams, with 1 MW m −2 and 0.1 MW m −2 for H and He beams, respectively. Losses were predominantly to carbon components independent of the mirror term. This is particularly apparent for the low-mirror configuration, showing that 97%–99% of the power loads avoid the more delicate steel components. The results of the helium injection and target plasmas can be validated against experimental results in the upcoming campaign to support the results for the deuterium modelling.

The particle exhaust system plays a pivotal role in fusion reactors and is essential for ensuring both the feasibility and sustained operation of the fusion reaction. For the successful development of such a system, density control is of great importance and some key design parameters include the neutral gas pressure and the resulting particle fluxes. This study presents a simplified conductance-based model for estimating neutral gas pressure distributions in the particle exhaust system of fusion reactors, focusing specifically on the sub-divertor region. In the proposed model, the pumping region is represented as an interconnected set of reservoirs and channels. Mass conservation and conductance relations, appropriate for all flow regimes, are applied. The model was benchmarked against complex 3D DIVGAS simulations across representative operating scenarios of the Wendelstein 7-X (W7-X) stellarator. Despite geometric simplifications, the model is capable of predicting pressure values at several key locations inside the particle exhaust area of W7-X, as well as various types of particle fluxes. The developed model is computationally efficient for large-scale parametric studies, exhibiting an average deviation of approximately 20%, which indicates reasonable predictive accuracy considering the model simplifications and the flow problem complexity. Its application may assist early-stage engineering design, pumping performance improvement, and operational planning for W7-X and other future fusion reactors.

Abstract Radiative losses from the plasma represent a key component of global power balance in a magnetic confinement fusion device. Measurements of the plasma radiation and its spatial distribution are essential for physical studies and to ensure safe machine operation. Here, an imaging bolometer diagnostic is employed to characterize the plasma radiated power in the island divertor of the large Wendelstein 7-X (W7-X) stellarator device. In attached plasmas, the divertor radiation pattern exhibits magnetic field-aligned stripes and a toroidally non-uniform character highly correlated with the target power load deposition pattern of the given magnetic field configuration. Toroidal uniformity of the plasma emissivity is partly recovered in detached discharges. Similar results are found in EMC3-EIRENE simulations of carbon impurity radiation, which indicate that the steep toroidal emissivity gradients observed in the experiment (factor x2 change over 10 cm parallel distance) are supported by toroidally localized particle sources.

The Wendelstein 7-X (W7-X), the largest stellarator in the world investigating the suitability of stellarators as power plant, has been in operation since 2015 at the Max-Planck-Institut für Plasmaphysik in Greifswald. W7-X has three magnet systems, namely, superconducting magnet system, trim coil magnet system, and control coil (CC) magnet system. The CC system consists of ten identical, 3-D shaped coils, situated inside the plasma vessel (PV) behind the baffle plates of each corresponding divertor unit. They are designated to both rectify the error field and sweep hot spots on the divertor target plates. These coils are constructed by winding a hollow copper conductor (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$15\times 15$</tex-math> </inline-formula> mm with 8-mm-diameter water channel, with overall dimensions of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.0\times 0.4$</tex-math> </inline-formula> m) and operated under higher thermal and electromagnetic (EM) loads. Enhanced plasma operation scenarios planned for the 2024/2025 campaigns required implementing a 3.5-kA CC direct current (dc) pulse, which is 40% higher than the CC system’s design value of 2.5-kA dc. The original ANSYS CC finite element model (FEM) developed in 2017 has been refined for both thermal and mechanical analyses in order to provide reliable results for life time estimations. The model enhancements include modeling the water flowing through the hollow channel, aiming to capture both the thermal gradient between neighboring conductors and the corresponding thermal stresses in the orthotropic insulation. This enhancement adds the possibility to validate the FEM result with the results obtained from the temperature sensors at the outlet during the experiment. Another model enhancement consisted in employing a quadratic mesh on each component of the CC FEM in order to avoid artificial concentration of stresses due to a coarse mesh choice. The mechanical analysis takes into account the deadweight (DW) load, EM forces applied to the copper conductor, and temperature gradient from the transient thermal analysis at the time when the conductor temperature reaches its maximum. As a result, the CC pulse with ~10-s flat top of 3.5-kA dc at 2.5-T main magnetic field is compatible with the W7-X CC system. However, the analysis indicated some critical areas with stress levels above allowable static limits in the conductor and stainless steel (SS) coil case. Two finite element (FE) submodels (SMs) with finer mesh have been created for the critical regions and analyzed under boundary conditions interpolated from the refined FEM. The submodelling results confirmed that the CC system can be operated with the required short pulse when the PV temperature is below <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50~^{\circ }$</tex-math> </inline-formula>C, without both overloading the metallic components and delaminating the insulation.

Abstract We present a systematic experimental study of the ion plasma velocity field in the Wendelstein 7-X (W7-X) stellarator, in multiple magnetic configurations and operation conditions, and assess the ability of neoclassical theory to explain the observations. In this assessment, we employ a forward model of the velocity measurement from the charge exchange recombination spectroscopy (CXRS) diagnostic with a rigorous treatment of the ion flow and line of sight geometries, as well as wavelength corrections due to atomic physics and instrumental effects.The minimisation of the absolute difference between the experimentally measured velocity profiles and those predicted by the forward model enables the inversion of radial profiles of the radial electric field and the net parallel impurity ion velocity, which can be directly compared with neoclassical computations. Non-trivial redundancy in the multiple simultaneous velocity measurements allows to self-calibrate instrumental wavelength drifts within the forward model. A recent extension in the model representation has resulted in a substantial quantitative improvement in the agreement between CXRS velocity measurements and neoclassical flow expectations, which are now shown to be compatible in the majority of the cases. Furthermore, we show that the flow inversions are statistically robust and consistent when two different emission lines are used. The radial electric field compares well with independent Doppler reflectometry measurements within the radial region where they overlap. By and large, the observations presented support the validity of neoclassical flow calculations in the plasma core and mid-radius region ( ρ 0.7) in W7-X. However, with the presently accessible experimental accuracy and magnetic configuration variations, a clear configuration dependence of the ion flow could not be determined.

We present an improved diffraction model for phase contrast imaging (PCI), relevant to the measurement of electron density fluctuations in magnetically confined fusion plasmas. The model applies to optical systems containing multiple special components, such as phase plates, localization masks, and apertures, connected by segments describable in terms of ray transfer matrices. Fresnel diffraction in the connecting segments may be described using linear canonical transforms, while the special components are characterized by their respective transfer functions. For a PCI system with ideal placement of the phase plate and localization mask, deviations between the Fresnel and Fraunhofer diffraction models are entirely determined by the distance from the diffraction plane to the object plane of the optical system. Application of the developed model to the synthetic PCI diagnostic at the Wendelstein 7-X (W7-X) stellarator shows minimal impact of diffraction on the DC detector power. However, significant amplitude modifications due to phase scintillation from diffraction are expected for high-wavenumber PCI sound wave calibration signals at W7-X, in qualitative agreement with the experimental observations. In contrast to previous expectations, diffraction is found to have only a small impact on the localization mask response characteristics at W7-X. Based on this observation, we show that the synthetic PCI mask response at W7-X can be reproduced by a model which only considers the signal at the beam center in the image plane without diffraction. We further use a similar model to reproduce the experimentally observed mask response from the DIII-D tokamak, indicating the general applicability of such models.

At Wendelstein 7-X (W7-X), the world's largest superconducting stellarator with a five-fold symmetry and reduced neoclassical transport, a broad suite of microwave diagnostics is installed and operated. Due to the robustness of in-vessel components and transmission lines against the harsh environment in fusion devices, they are candidates for reactor plasma control.This presentation will show an overview of microwave diagnostics at W7-X. After introducing the governing equations for the propagation of microwaves in a fusion plasma e.g. the determination of the local positions where the measurements are performed, the different diagnostics are presented. The presentation will encompass the installed diagnostics, but also, the planned upgrades and show important technical details and highlighting results obtained during the last campaigns. It will cover passive microwave diagnostics for the estimation of the electron temperature profile by radiometry from the 2nd and 3rd harmonic of the electron cyclotron emission (ECE) with a temporal resolution in the MHz-range. Furthermore, the 1st–3rd harmonic ECE radiation is measured with interferometry for both, X- and O-mode polarization. Also, fluctuations of the electron temperature are measured by various methods of correlation ECE. Active probing radar applications, so-called reflectometry, are installed to measure density fluctuations and its propagation. They allow measuring the turbulence propagation for a wide wavenumber range. Under certain assumptions the radial electric field, an important quantity for the neoclassical transport is deduced from this propagation. To measure the electron density profile in the edge, a frequency modulated continuous wave reflectometer is installed in the Ion Cyclotron Resonance Heating (ICRH)-antenna. The purpose of the instrument is the measurement of the density profile to improve the coupling of the ICRH-waves into the plasma. Besides this, the measurement of the density profile in the edge with high spatial and temporal resolution is independent of the ICRH-operation. Furthermore, a microwave scattering diagnostic, the collective Thomson Scattering (CTS), uses a gyrotron as active probing beam yields direct information of the ion temperature of hydrogen or in later campaigns deuterium species and does not rely on the impurity temperature.

Abstract This paper presents a neural‐network surrogate model for Wendelstein 7-X (W7-X) edge transport simulations, trained on an EMC3-EIRENE dataset that spans nearly the entire operating-parameter space currently explored in the W7-X standard configuration. The model uses an autoencoder to compress EMC3-EIRENE outputs into a low-dimensional latent space representation, then a neural regressor maps EMC3-EIRENE input parameters to those latent vectors, and finally both components are fine-tuned together to predict outputs directly from inputs. In benchmark tests, the improved surrogate outperforms a traditional multilayer perceptron model, most notably in predicting detached regime. Leave‐one‐value‐out evaluation indicates high accuracy within the interpolation domain, with minor degradation when extrapolating. Relative to full EMC3‐EIRENE runs, the surrogate provides over a 10 8 - fold speedup, enabling large-scale parameter scans or real-time feedback control based on 3D transport simulations to become feasible in the future.

Abstract In the Wendelstein 7-X (W7-X) stellarator, a ball-pen probe (BPP) has been routinely employed to measure Ti in the island SOL across large parts of the recent 2024/2025 campaigns. The high temporal resolution of 25 µs allows us to resolve Ti fluctuations, their probability density function and modulation by low-frequency MHD modes. We present a unique comparison of ion temperature measured using BPP with a more conventional retarding field analyzer (RFA). A good agreement between the two diagnostics is found, when fast Ti measurements are reduced to the same temporal resolution (5ms) using "RFA-like" averaging. With the RFA-like interpretation of fast BPP data, we find a linear decrease of SOL Ti and Te with line-integrated density. The SOL ion-to-electron temperature ratio τi,e ranges between τi,e = 1-3 with smaller τi,e values observed for higher densities (collisionalities) and at positions close to the LCFS. The upstream BPP Ti measurements are compared to averaged C 2+ Ti obtained by a coherence imaging spectroscopy (CIS), in the divertor region, magnetically mapped to the BPP. The downstream Ti measured by CIS is about half the upstream Ti and exhibits a similar inverse scaling with line-integrated density. Lastly, we benchmark experimentally obtained SOL Ti and Te against the EMC3-Eirene modeling and find a good agreement at high density plasmas, but significantly diverging results for low density plasmas.

Abstract Line-integrated density fluctuation measurements from the core of the optimised stellarator Wendelstein 7-X (W7-X) are studied in the context of magnetic field geometry changes. The amplitude as well as the spectral distribution of fluctuations is affected by varying the magnetic field configuration. Weaker turbulent fluctuations are observed in configurations with higher rotational transform and lower magnetic mirror depth. Simulations with the gyrokinetic codes stella and GENE-3D are used to investigate the role of magnetic geometry for the experimental observations. The stabilising effect of the high rational transform configuration is reproduced by simulations and can be associated with stronger shaping of the magnetic field. This leads to increased finite Larmor radius and local shear effects, which limit the toroidal extent of ion temperature gradient (ITG) modes. For W7-X configurations with higher magnetic mirror depth, gyrokinetic theory and simulations predict weaker fluctuations, since they are closer to having the maximum- J property, which has a stabilising effect on trapped-electron mode and ITG. The opposite trend is observed experimentally, which can therefore not be explained by geometry effects on turbulence alone.

Experiments in the Wendelstein 7-X (W7-X) stellarator with plasma density beyond the established density limit in stellarators [Scalings of energy confinement and density limit in stellarator/heliotron devices, Nucl. Fusion 30, 11 (1990).NUFUAU0029-551510.1088/0029-5515/30/1/002] resulted in unusual, reduced size, fully radiative plasmas lasting stably for many confinement times [Small, stable plasmas, fully decoupled from the plasma-facing components in W7-X, Stellarator News 175, 1 (2021).]. In these experiments, the plasma had shrunk to a significantly smaller minor radius due to intense edge radiation from a radiating mantle and had no contact with material components, yet it remained relatively well confined for many confinement times with electron temperatures on the order of 1keV. To our knowledge, this is the first definitive experimental long-time stability demonstration of such high-temperature contactless plasmas in the laboratory. It is shown that the onset and extent of this fully radiative small plasma state is predictable. The stability of the plasma size is elucidated with a simple power-balance model. In other helical devices such as the Large Helical Device (LHD) and the Wendelstein 7-AS (W7-AS), plasmas that start shrinking suffered from core impurity accumulation leading to a collapse whereas this was generally not observed for these W7-X plasmas.