Soft X-ray Measurements Research Articles

Spatial localization of ECE measurement in EAST LHW-heated plasmas

In this work, electron cyclotron emission (ECE) is simulated by using the code SPECE to study the spatial localization of ECE measurement in EAST plasmas heated by lower hybrid wave (LHW). The results indicate that generally there are two emission layers for an individual frequency in plasmas with non-thermal electrons, and they are separately attributed to the thermal electrons and non-thermal electrons. The emission layer due to the thermal electrons is nearly identical to that for the case with Maxwellian distribution. The emission layer due to non-thermal electrons is well localized in the location of the non-thermal electrons. Even though the non-thermal emission layer is broader, the emission intensity is smaller than that from the thermal emission layer for the cases studied in this work. Localized electron temperature fluctuations can still be distinguished by ECE measurement as long as it does not coexist with the non-thermal electrons. Sawtooth inversion radii and tearing mode island location determined respectively by the ECE measurement and the soft x-ray measurement for a LHW-heated plasma show a good agreement, and this indicates that the ECE measurement in the plasma core region is not seriously polluted.

Soft X-Ray Measurement on the Collisional Merging Process in a Field-Reversed Configuration

Soft X-Ray Measurement on the Collisional Merging Process in a Field-Reversed Configuration

Narrowband lamellar multilayer grating with low contrast MoSi2/Si materials for the soft x-ray region

To develop highly efficient narrow-bandwidth multilayer optics for the soft x-ray (SXR) spectroscopy, a low optical contrast MoSi2/Si lamellar multilayer grating (LMG) was proposed and developed. The low contrast LMG allows for a large lamel width which can potentially achieve higher resolution than the conventional LMG and simplify the fabrication. As a first demonstration, a MoSi2/Si multilayer with a d-spacing of 5 nm and 180 bilayers was deposited. The lamellar grating structure with a period of 614 nm, lamel-to-period ratio of 0.38, and lamel height of 670 nm was fabricated in the multilayer with reactive ion etching process. The SXR measurements show a high 0th-order diffraction efficiency of 16%–33% at 876 eV–1648 eV, which reaches around 80% of the unetched multilayer reflectivity. A maximal bandwidth reduction of 2.2 times was obtained compared with the multilayer mirror, indicating an energy resolution of E/ΔE = 108 at 1183 eV. The resolution can be further improved by reducing the multilayer d-spacing and increasing the etching depth.

SiC detectors for evaluation of laser–plasma dynamics employing gas-puff targets

An Nd:YAG pulsed laser was employed to irradiate different gas-puff targets. The interaction gives rise to the emission of soft X-ray (SXR), ultraviolet and extreme ultraviolet (EUV) radiation useful for X-ray microscopy. A Silicon Carbide (SiC) and a Si detector were employed to characterize the photon plasma emission of different gases in different wavelength ranges. The EUV and SXR measurements with different filters show the applicability of SiC detectors for plasma monitoring and characterization. Detector linearity, plasma evolution over the time and the relative intensity signal of both detectors will be presented and discussed.

Evolution of a Pinch Column During the Acceleration of Fast Electrons and Deuterons in a Plasma-Focus Discharge

Plasma in a pinch column, as produced by a plasma-focus discharge at the deuterium filling and the current intensity reaching 1 MA, was investigated at the total neutron yield reaching about 10 10 per discharge. The use was made of neutron diagnostics, laser interferometry, soft X-ray measurements, optical emission spectroscopy, magnetic probes, as well as electron and ion measurements with the temporal, spatial, and energetic resolutions. The detailed studies showed the ordered toroidal, helical, and plasmoidal structures which could contain currents with poloidal and toroidal components and their associated magnetic fields. Their spontaneous transformations were explained by changes in a topology of magnetic field lines due to magnetic reconnections. A nonthermal acceleration of fast electrons and ions (producing hard X-rays and fusion neutrons, respectively) corresponded to: 1) the formation of plasmoids in the pinch column and 2) a decay of pinch constrictions and secondary plasmoids during the evolution of instabilities. A filamentary structure of the current flow could explain the high energy density and fast transformations of the magnetic energy into kinetic energy of electron and ion beams (reaching energy of hundreds of kiloelectronvolt). This paper summarizes the results obtained with the PF-1000 facility in 2009-2017, and describes the internal transformations in a dense plasma column during the evolution of MHD instabilities.

Alignment of the aberration-free XUV Raman spectrometer at FLASH.

An extreme-ultraviolet (XUV) double-stage Raman spectrometer is permanently installed as an experimental end-station at the PG1 beamline of the soft X-ray/XUV free-electron laser in Hamburg, FLASH. The monochromator stages are designed according to the Czerny-Turner optical scheme, adapted for the XUV photon energy range, with optical elements installed at grazing-incidence angles. Such an optical scheme along with the usage of off-axis parabolic mirrors for light collimation and focusing allows for aberration-free spectral imaging on the optical axis. Combining the two monochromators in additive dispersion mode allows for reaching high resolution and superior stray light rejection, but puts high demands on the quality of the optical alignment. In order to align the instrument with the highest precision and to quantitatively characterize the instrument performance and thus the quality of the alignment, optical laser interferometry, Hartmann-Shack wavefront-sensing measurements as well as off-line soft X-ray measurements and extensive optical simulations were conducted. In this paper the concept of the alignment scheme and the procedure of the internal optical alignment are presented. Furthermore, results on the imaging quality and resolution of the first monochromator stage are shown.

Applications of thin film plastic scintillator in measurement of soft x rays generated from Z-pinch implosion.

A thin film plastic scintillator detector has been developed for the measurement of radiation power and yield of soft x rays produced from Z-pinch implosion. To enable soft x-ray measurements using plastic scintillators, the detector geometry has been specially designed to minimize visible light and alleviate nonlinear behavior. Energy response has been calibrated, and saturation effects have been explored and described in details. The possibility and limitation of its application to such high-density radiation bursts are analyzed. The detector has been fielded on several meters away in vacuum pipes for hundreds of shots at different Z-pinch facilities, and the measured data in these experiments agreed well with the results from other diagnostics, demonstrating the feasibility and reliability of the detector.

Advanced Real-time Evaluation and Data Quality Monitoring Model Integration with FPGAs for Tokamak High-performance Soft X-ray Diagnostic System

Based on the publications regarding new or recent measurement systems for the tokamak plasma experiments, it can be found that the monitoring and quality validation of input signals for the computation stage is done in different, often simple, ways. In the paper is described the unique approach to implement the novel evaluation and data quality monitoring (EDQM) model for use in various measurement systems. The adaptation of the model is made for the GEM-based soft X-ray measurement system FPGA-based. The EDQM elements has been connected to the base firmware using PCI-E DMA real-time data streaming with minimal modification. As additional storage, on-board DDR3 memory has been used. Description of implemented elements is provided, along with designed data processing tools and advanced simulation environment based on Questa software.

Model Validation for Quantitative X-Ray Measurements

Soft–X-ray (SXR) brightness measurements contain information on a number of physics parameters in fusion plasmas; however, it is nearly impossible to extract the information without modeling. A validated forward model is therefore necessary for the accurate interpretation of SXR measurements and will be critical in the burning plasma era, where medium- and high-Z impurities are ever present. The Atomic Data and Analysis Structure (ADAS) database is a powerful interpretive tool that is extensively used to model and predict atomic spectra, level populations, and ionization balance for fusion plasmas. These predictions are in good agreement with experimental measurements. However, continuum radiation in the X-ray range, while also modeled in ADAS, has not been rigorously verified or tested against experimental data. We therefore performed a systematic comparison of ADAS to a simplified model called PFM. PFM only calculates continuum radiation but shows good agreement with experimental data when only continuum radiation is present. ADAS and the simplified model agree to within 1% to 2% indicating that ADAS is calculating continuum radiation correctly. We have also begun a validation of SXR brightness calculations from ADAS. The SXR brightness measurements modeled by ADAS agree well with experimental measurements from an extreme where the signal is dominated by line radiation continuously through another extreme where the signal is dominated by continuum emission. While this validation work is preliminary, it strongly suggests that ADAS accurately models the physics that lead to SXR radiation.

Soft X-ray and cathodoluminescence measurement, optimisation and analysis at liquid nitrogen temperatures

Advances in field emission gun electron microprobes have led to significant gains in the beam power density and when analysis at high resolution is required then low voltages are often selected. The resulting beam power can lead to damage and this can be minimised by cooling the sample down to cryogenic temperatures allowing sub-micrometre imaging using a variety of spectrometers. Recent advances in soft X-ray emission spectrometers (SXES) offer a spectral tool to measure both chemistry and bonding and when combined with spectral cathodoluminescence the complementary techniques enable new knowledge to be gained from both mineral and materials. Magnesium and aluminium metals have been examined at both room and liquid nitrogen temperatures by SXES and the L-emission Fermi-edge has been observed to sharpen at the lower temperatures directly confirming thermal broadening of the X-ray spectra. Gains in emission intensity and resolution have been observed in cathodoluminescence for liquid nitrogen cooled quartz grains compared to ambient temperature quartz. This has enabled subtle growth features at quartz to quartz-cement boundaries to be imaged for the first time.

SXR measurement and W transport survey using GEM tomographic system on WEST

Measuring Soft X-Ray (SXR) radiation (0.1–20 keV) of fusion plasmas is a standard way of accessing valuable information on particle transport. Since heavy impurities like tungsten (W) could degrade plasma core performances and cause radiative collapses, it is necessary to develop new diagnostics to be able to monitor the impurity distribution in harsh fusion environments like ITER. A gaseous detector with energy discrimination would be a very good candidate for this purpose. The design and implementation of a new SXR diagnostic developed for the WEST project, based on a triple Gas Electron Multiplier (GEM) detector is presented. This detector works in photon counting mode and presents energy discrimination capabilities. The SXR system is composed of two 1D cameras (vertical and horizontal views respectively), located in the same poloidal cross-section to allow for tomographic reconstruction. An array (20 cm × 2 cm) consists of up to 128 detectors in front of a beryllium pinhole (equipped with a 1 mm diameter diaphragm) inserted at about 50 cm depth inside a cooled thimble in order to retrieve a wide plasma view. Acquisition of low energy spectrum is insured by a helium buffer installed between the pinhole and the detector. Complementary cooling systems (water) are used to maintain a constant temperature (25̂C) inside the thimble. Finally a real-time automatic extraction system has been developed to protect the diagnostic during baking phases or any overheating unwanted events. Preliminary simulations of plasma emissivity and W distribution have been performed for WEST using a recently developed synthetic diagnostic coupled to a tomographic algorithm based on the minimum Fisher information (MFI) inversion method. First GEM acquisitions are presented as well as estimation of transport effect in presence of ICRH on W density reconstruction capabilities of the GEM.

Implosion dynamics of condensed Z-pinch at the Angara-5-1 facility

The implosion dynamics of a condensed Z-pinch at load currents of up to 3.5 MA and a current rise time of 100 ns was studied experimentally at the Angara-5-1 facility. To increase the energy density, 1- to 3-mm-diameter cylinders made of a deuterated polyethylene−agar-agar mixture or microporous deuterated polyethylene with a mass density of 0.03–0.5 g/cm3 were installed in the central region of the loads. The plasma spatiotemporal characteristics were studied using the diagnostic complex of the Angara-5-1 facility, including electron-optical streak and frame imaging, time-integrated X-ray imaging, soft X-ray (SXR) measurements, and vacuum UV spectroscopy. Most information on the plasma dynamics was obtained using a ten-frame X-ray camera (Е > 100 eV) with an exposure of 4 ns. SXR pulses were recorded using photoemissive vacuum X-ray detectors. The energy characteristics of neutron emission were measured using the time-offlight method with the help of scintillation detectors arranged along and across the pinch axis. The neutron yield was measured by activation detectors. The experimental results indicate that the plasma dynamics depends weakly on the load density. As a rule, two stages of plasma implosion were observed. The formation of hot plasma spots in the initial stage of plasma expansion from the pinch axis was accompanied by short pulses of SXR and neutron emission. The neutron yield reached (0.4–3) × 1010 neutrons/shot and was almost independent of the load density due to specific features of Z-pinch dynamics.

A STATISTICAL STUDY OF FLARE PRODUCTIVITY ASSOCIATED WITH SUNSPOT PROPERTIES IN DIFFERENT MAGNETIC TYPES OF ACTIVE REGIONS

ABSTRACT It is often believed that intense flares preferentially originate from the large-size active regions (ARs) with strong magnetic fields and complex magnetic configurations. This work investigates the dependence of flare activity on the AR properties and clarifies the influence of AR magnetic parameters on the flare productivity, based on two data sets of daily sunspot and flare information as well as the GOES soft X-ray measurements and HMI vector magnetograms. By considering the evolution of magnetic complexity, we find that flare behaviors are quite different in the short- and long-lived complex ARs and the ARs with more complex magnetic configurations are likely to host more impulsive and intense flares. Furthermore, we investigate several magnetic quantities and perform the two-sample Kolmogorov–Smirnov test to examine the similarity/difference between two populations in different types of ARs. Our results demonstrate that the total source field strength on the photosphere has a good correlation with the flare activity in complex ARs. It is noted that intense flares tend to occur at the regions of strong source field in combination with an intermediate field-weighted shear angle. This result implies that the magnetic free energy provided by a complex AR could be high enough to trigger a flare eruption even with a moderate magnetic shear on the photosphere. We thus suggest that the magnetic free energy represented by the source field rather than the photospheric magnetic complexity is a better quantity to characterize the flare productivity of an AR, especially for the occurrence of intense flares.

Comparison of silicon drift detectors made by Amptek and PNDetectors in application to the PHA system for W7-X

Abstract The paper presents comparison of two silicon drift detectors (SDD), one made by Amptek, USA, and the second one by PNDetector, Germany, which are considered for a soft X-ray diagnostic system for W7-X. The sensitive area of the first one is 7 mm2 × 450 μm and the second one is 10 mm2 × 450 μm. The first detector is cooled by a double-stage Peltier element, while the second detector is cooled by single-stage Peltier element. Each one is equipped with a field-effect transistor (FET). In the detector from Amptek, the FET is mounted separately, while in the detector from PNDetector, the FET is integrated on the chip. The nominal energy resolution given by the producers of the first and the second one is 136 eV@5.9 keV (at -50°C) and 132 eV@5.9 keV (at -20°C), respectively. Owing to many advantages, the investigated detectors are good candidates for soft X-ray measurements in magnetic confinement devices. They are suitable for soft X-ray diagnostics, like the pulse height analysis (PHA) system for the stellarator Wendelstein 7-X, which has been developed and manufactured at the Institute of Plasma Physics and Laser Microfusion (IPPLM), Warsaw, in collaboration with the Max Planck Institute for Plasma Physics (IPP), Greifswald. The diagnostic is important for the measurements of plasma electron temperature, impurities content, and possible suprathermal tails in the spectra. In order to choose the best type of detector, analysis of technical parameters and laboratory tests were done. Detailed studies show that the most suitable detector for the PHA diagnostics is the PNDetector.

Temperature and Humidification Effect on Mass Transfer of PEMFC Via EIS and Soft X-Ray Measurement

In proton exchange membrane fuel cells (PEMFCs), appropriate water management is critical to achieve high power density operation with increased robustness. Proton exchange membranes (PEMs) require sufficient hydration to fulfill its function as proton conductor, while flooding at the cathode side can hamper the transport of reactant, resulting in deterioration of cell operation. Liquid water accumulation and its transportation is one of major issue for PEMFCs. For diagnosis the water and mass transport ability the following experimental methods can be used: polarization, oxygen gain, limiting current density, calculate oxygen transportation resistance, electrochemical impedance spectrum (EIS), and visualization technique etc. However, there are not so many literatures point out where the water accumulation can cause the mass transport resistance arc. In this study, the cell operated temperature and cathode humidify has been selected as main parameters for investigating the mass transfer phenomenon. The EIS was using for indicating mass transport occurs condition and the soft X-ray radiography was using for verify the location of the water accumulation. The soft X-ray radiography [1-13] had been proved it is a powerful tool to investigate liquid water within membrane electrode assemblies (MEAs). Fig. 1 (a) shows EIS and water extraction image with different humidification conditions. The liquid water accumulation within gas diffusion substrates/channel is barely effects nothing on the mass transport resistance art. The water extraction image implies the water accumulates within/nearby catalyst layer is the main reason to cause the mass transport resistance art. Fig. 1(b) shows EIS and water extraction image with different operating conditions. It is barely no mass transport resistance arc at high temperate condition, due to generation water is mainly as vapor form. This result indicates the mass transport resistance arc is important indicator which points out there are liquid water accumulate within/nearby catalyst layer. Acknowledgement This work has been supported by the New Energy and Industrial Technology Development Organization (NEDO) of Japan.

Temperature and Humidification Effect on Mass Transfer of PEMFC Via EIS and Soft X-Ray Measurement

Proper water management is essential for proton exchange membrane fuel cells (PEMFCs) to approach high current densityand high power density operation. Therefore the analysis of water and mass transport ability within PEMFC are one of the important issues that needs to be solved. Electrochemical impedance spectrum (EIS) and soft X-ray visualization technique are useful methods for diagnosing mass transportation resistance and water behavior, respectively. In this study, a correlation between EIS and visualization images were used to investigate the mass transfer phenomenon. The operated oxygen concentration, cathode gas humidity and cell temperature had been discussed in this study. The visualization image implies the mass transport arc which was mainly caused by water flooding within or nearby the catalyst layer.

Numerical and experimental study of the redistribution of energetic and impurity ions by sawteeth in ASDEX Upgrade

In the non-linear phase of a sawtooth, the complete reconnection of field lines around the q = 1 flux surface often occurs resulting in a radial displacement of the plasma core. A complete time-dependent electromagnetic model of this type of reconnection has been developed and implemented in the EBdyna_go code. This contribution aims at studying the behaviour of ions, both impurity and fast particles, in the pattern of reconnecting field lines during sawtoothing plasma experiments in the ASDEX Upgrade tokamak by using the newly developed numerical framework. Simulations of full reconnection with tungsten impurity that include the centrifugal force are achieved and recover the soft x-ray measurements. Based on this full-reconnection description of the sawtooth, a simple tool dedicated to estimate the duration of the reconnection is introduced. This work then studies the redistribution of fast ions during several experimentally observed sawteeth. In some cases of sawteeth at ASDEX Upgrade, full reconnection is not always observed or expected so the code gives an upper estimate of the actual experimental redistribution. The results of detailed simulations of the crashes are compared with measurements from various diagnostics such as collective Thomson scattering and fast-ion D-alpha (FIDA) spectroscopy, including FIDA tomography. A convincing qualitative agreement is found in different parts of velocity space.

Study on Reaction Magnesium Deposition Mechanism By Operando Soft X-Ray Absorption Spectroscopy

Magnesium rechargeable batteries have much attention for next generation batteries because of the high theoretical volumetric capacity, safety, and abundance of magnesium metal anode. In order to improve the efficiency of magnesium metal anode, it is required to develop the electrolyte that enables magnesium deposition and dissolution reversibly. Although Grignard reagents have been widely known as the electrolyte for magnesium deposition/dissolution[1], the stability of the electrolytes in high potential and their corrosive nature are major problems. In recent years, magnesium deposition/dissolution in magnesium inorganic salts with triglyme solvents have been reported[2,3]. For the further development of electrolyte for magnesium batteries, the reaction mechanism at electrolyte/magnesium metal interface should be elucidated. In this study, we have developed operando soft X-ray measurement system and apply to the analysis of electronic and local structure of electrolyte during magnesium deposition. Furthermore, bulk structure of electrolyte is investigated by Raman spectroscopy, X-ray absorption spectroscopy (XAS) and the theoretical calculation. 0.5 M Mg(TFSA)2/triglyme and 0.5 M Mg(TFSA)2/2-MeTHF electrolytes were prepared by mixing Mg(TFSA)2 (KISHIDA CHEMICAL Co., Ltd., 99.9%>) with triglyme (KISHIDA CHEMICAL Co., Ltd. 99%>) or 2-MeTHF (Merck, 98%>) in an Ar-filled glove box. Electrochemical properties of the electrolyte were investigated by cyclic voltammetry (CV) with the three-electrode cell. Platinum plate and magnesium rod were used as working electrode and counter electrode, respectively. Operando XAS measurements at Mg K-edge were carried out at the beam line BL27SU at SPring-8 (Japan). XAS spectra were obtained at different potential during magnesium deposition. Raman spectroscopic measurements were carried out using LabRAM HR-800 (HORIBA, Ltd.) equipped with He-Ne laser (633 nm) at room temperature. While magnesium deposition/dissolution is observed in Mg(TFSA)2/triglyme and Grignard system, magnesium is not deposited in Mg(TFSA)2/2-MeTHF. From the results of Raman spectroscopy, TFSA anion exists as uncoordinated state with magnesium ion in the triglyme system, while TFSA anion coordinates with magnesium ion in the 2-MeTHF system. Fourier transform from Mg K-edge EXAFS oscillation measured at different potentials in 0.5 M Mg(TFSA)2/triglyme and 0.5 M Mg(TFSA)2/2-MeTHF indicate that peak intensity of Mg-O bond decreases with decreasing potential.The decreases of peak intensity reflect the desolvation process of triglyme and 2-MeTHF from magnesium ion. These results suggested that reason of high overpotential in 0.5 M Mg(TFSA)2/2-MeTHF is specific adsorption of TFSA anion. The specific adsorped TFSA anion may inhibits charge transfer raction of magnesium ion. ACKNOWLEDGMENTS This study was partially supported by the Research and Development Initiative for Scientific Innovation of New Generation Battery (RISING) Project under the auspices of New Energy and Industrial Technology Development Organization (NEDO), Japan. Synchrotron radiation experiment was performed at BL27SU of SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (JASRI). REFERENCES [1] Aurbach, D.; Lu, Z.; Schechter, A.; Gofer, Y.; Gizbar, H.; Turgeman, R.; Cohen, Y.; Moshkovich M.; Levi, E., Nature, 407, 724 (2000). [2] Ha, S.-Y.; Lee, Y.-W.; Woo, S.W.; Koo, B.; Kim, J.-S.; Cho, J.; Lee, K.T.; Choi, N.-S., ACS Appl. Mater. Interfaces 6, 4063 (2014). [3] Orikasa, Y.; Masese, T.; Koyama, Y.; Mori, T.; Hattori, M.; Yamamoto, K.; Okado, T.; Huang, Z. -D.; Minato, T.; Tassel, C.; Kim, J.; Kobayashi, Y.; Abe, T.; Kageyama, H.; Uchimoto, Y., Sci. Rep., 4, 5622 (2014).

Progress in stellarator research at IPP-Kharkov

Abstract A new antenna of ‘crankshaft’ type has been installed in the Uragan-2M device in order to increase the plasma density and heating below the ion cyclotron frequency. Antenna operation is modelled by 1D code, which solves boundary problem for time-harmonic Maxwell’s equations in radially non-uniform plasma cylinder. In recent experiments with this antenna, the SXR, CV, OV and OII emission measurements indicate that the light impurity radiation barrier is overcame at this device. Plasma with a temperature of ~50 eV exists during a short period of a few milliseconds. Then the radiation collapse comes owing to strong influx of impurities to the plasma column. A new magnetic diagnostics has been installed at Uragan-3M. Using it the poloidal magnetic field is measured and the shift of toroidal current in major radius is registered. A miniature pinhole camera array for spatially and temporally resolved measurements of soft X-ray (SXR) plasma emission has been recently installed on the U-3M. Different shapes of the SXR emission profile has been observed in different discharge conditions.

Coronal O VI emission observed with UVCS/SOHO during solar flares: Comparison with soft X-ray observations

In this work, we derive the O VI 1032 A luminosity profiles of 58 flares, during their impulsive phase, based on off-limb measurements by the Ultraviolet Coronagraph Spectrometer (UVCS) aboard the SOlar and Heliospheric Observatory (SOHO). The O VI luminosities from the transition region plasma (here defined as the region with temperatures 5.0 ≤ log T (K) ≤ 6.0) were inferred from the analysis of the resonantly scattered radiation of the O VI coronal ions. The temperature of maximum ionization for O VI is log T max (K) = 5.47. By comparison with simultaneous soft X-ray measurements, we investigate the likely source (chromospheric evaporation, footpoint emission, or heated prominence ejecta) for the transition region emission observed during the impulsive phase. In our study, we find evidence of the main characteristics predicted by the evaporation scenario. Specifically, most O VI flares precede the X-ray peaks typically by several minutes with a mean of 3.2 ± 0.1 min, and clear correlations are found between the soft X-ray and transition region luminosities following power laws with indices ~ 0.7 ± 0.3. Overall, the results are consistent with transition region emission originating from chromospheric evaporation; the thermal X-ray emission peaks after the emission from the evaporation flow as the loops fill with hot plasma. Finally, we were able to infer flow speeds in the range ~20−100 km s-1 for one-third of the events, 14 of which showed speeds between 60 and 80 km s-1 . These values are compatible with those found through direct spectroscopic observations at transition region temperatures by the EUV Imaging Spectrometer (EIS) on board Hinode.