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We present indirect constraints on the absolute escape fraction of ionizing photons ($f_{\rm esc}^{\rm LyC}$) of the system GN 42912 which comprises two luminous galaxies ($M_{\rm UV}$ magnitudes of -20.89 and -20.37) at $z\sim7.5$, GN 42912-NE and GN 42912-SW, to determine their contribution to the ionizing photon budget of the Epoch of Reionization (EoR). The high-resolution James Webb Space Telescope NIRSpec and NIRCam observations reveal the two galaxies are separated by only ~0.1$"$ (0.5 kpc) on the sky and have a 358 km s$^{-1}$ velocity separation. GN 42912-NE and GN 42912-SW are relatively massive for this redshift (log($M_\ast/M_\odot$) $\sim$ 8.4 and 8.9, respectively), with gas-phase metallicities of 18 per cent and 23 per cent solar, O$_{32}$ ratios of 5.3 and $>5.8$, and $\beta$ slopes of $-1.92$ and $-1.51$, respectively. We use the Mg II$\lambda\lambda$2796,2803 doublet to constrain $f_{\rm esc}^{\rm LyC}$. Mg II has an ionization potential close to that of neutral hydrogen and, in the optically thin regime, can be used as an indirect tracer of the LyC leakage. We establish realistic conservative upper limits on $f_{\rm esc}^{\rm LyC}$ of 8.5 per cent for GN 42912-NE and 14 per cent for GN 42912-SW. These estimates align with $f_{\rm esc}^{\rm LyC}$ trends observed with $\beta$, O$_{32}$, and the H$\beta$ equivalent width at $z<4$. The small inferred ionized region sizes ($<0.3$ pMpc) around both galaxies indicate they have not ionized a significant fraction of the surrounding neutral gas. While these $z>7$ $f_{\rm esc}^{\rm LyC}$ constraints do not decisively determine a specific reionization model, they support a minor contribution from these two relatively luminous galaxies to the EoR., Comment: 18 pages, submitted to MNRAS

Here we present high spectral resolution $\textit{JWST}$ NIRSpec observations of GN42437, a low-mass (log(M$_\ast/M_\odot)=7.9$), compact ($r_e < 500$pc), extreme starburst galaxy at $z=5.59$ with 13 emission line detections. GN42437 has a low-metallicity (5-10% Z$_\odot$) and its rest-frame H$\alpha$ equivalent width suggests nearly all of the observed stellar mass formed within the last 3 Myr. GN42437 has an extraordinary 7$\sigma$ significant [Ne V] 3427 $\mathring{\rm A}$ detection. The [Ne V] line has a rest-frame equivalent width of $11\pm2\mathring{\rm A}$, [Ne V]/H$\alpha =0.04\pm0.007$, [Ne V]/[Ne III] 3870$\mathring{\rm A} = 0.26\pm0.04$, and [Ne V]/He II 4687 $\mathring{\rm A} = 1.2\pm0.5$. Ionization from massive stars, shocks, or high-mass X-ray binaries cannot simultaneously produce these [Ne V] and low-ionization line ratios. Reproducing the complete nebular structure requires both massive stars and accretion onto a black hole. We do not detect broad lines nor do the traditional diagnostics indicate that GN42437 has an accreting black hole. Thus, the very-high-ionization emission lines powerfully diagnose faint narrow-line black holes at high-redshift. We approximate the black hole mass in a variety of ways as log(M$_{\rm BH}/M_\odot) \sim 5-7$. This black hole mass is consistent with local relations between the black hole mass and the observed velocity dispersion, but significantly more massive than the stellar mass would predict. Very-high-ionization emission lines may reveal samples to probe the formation and growth of the first black holes in the universe., Comment: 18 pages, submitted to MNRAS. Comments encouraged

The geometry of the neutral gas in and around galaxies is a key regulator of the escape of ionizing photons. We present the first statistical study aiming at linking the neutral and ionized gas distributions to the Lyman continuum (LyC) escape fraction (fesc(LyC)) in a sample of 22 confirmed LyC leakers and non-leakers at z~0.35 using the Keck Cosmic Web Imager (Keck/KCWI) and the Low Resolution Spectrograph 2 (HET/LRS2). Our integral field unit data enable the detection of neutral and low-ionization gas, as traced by Mg II, and ionized gas, as traced by [O II], extending beyond the stellar continuum for 7 and 10 objects, respectively. All but one object with extended Mg II emission also shows extended [O II] emission; in this case, Mg II emission is always more extended than [O II] by a factor 1.3 on average. Most of the galaxies with extended emission are non or weak LyC leakers (fesc(LyC) < 5%), but we find a large diversity of neutral gas configurations around these weakly LyC-emitting galaxies. Conversely, the strongest leakers (fesc(LyC) > 10%) appear uniformly compact in both Mg II and [O II] with exponential scale lengths <1 kpc. We also find a trend between fesc(LyC) and the spatial offsets of the nebular gas and the stellar continuum emission. Moreover, we find significant anti-correlations between the spatial extent of the neutral gas and the [O III]/[O II] ratio, and H$\beta$ equivalent width, as well as positive correlations with metallicity and UV size, suggesting that galaxies with more compact neutral gas sizes are more highly ionized. The observations suggest that strong LyC emitters do not have extended neutral gas halos and ionizing photons may be emitted in many directions. Combined with high ionization diagnostics, we propose the Mg II, and potentially [O II], spatial compactness are indirect indicators of LyC emitting galaxies at high-redshift., Comment: 31 pages, 24 figures, 4 tables, submitted to A&A

We report observational evidence of highly turbulent ionized gas kinematics in a sample of 20 Lyman continuum (LyC) emitters (LCEs) at low redshift ($z\sim 0.3$). Detailed Gaussian modeling of optical emission line profiles in high-dispersion spectra consistently shows that both bright recombination and collisionally excited lines can be fitted as one or two narrow components with intrinsic velocity dispersion of $\sigma$ $\sim$ 40-100 km s$^{-1}$, in addition to a broader component with $\sigma \sim$ 100-300 km s$^{-1}$, which contributes up to $\sim$40% of the total flux and is preferentially blueshifted from the systemic velocity. We interpret the narrow emission as highly ionized gas close to the young massive star clusters and the broader emission as a signpost of unresolved ionized outflows, resulting from massive stars and supernova feedback. We find a significant correlation between the width of the broad emission and the LyC escape fraction, with strong LCEs exhibiting more complex and broader line profiles than galaxies with weaker or undetected LyC emission. We provide new observational evidence supporting predictions from models and simulations; our findings suggest that gas turbulence and outflows resulting from strong radiative and mechanical feedback play a key role in clearing channels through which LyC photons escape from galaxies. We propose that the detection of blueshifted broad emission in the nebular lines of compact extreme emission-line galaxies can provide a new indirect diagnostic of Lyman photon escape, which could be useful to identify potential LyC leakers in the epoch of reionization with the JWST., Comment: 11 Pages, 7 Figures. A&A in Press

We report the discovery of broad components with P-Cygni profiles of the hydrogen and helium emission lines in the two low-redshift low-metallicity dwarf compact star-forming galaxies (SFG), SBS 1420+540 and J1444+4840. We found small stellar masses of 10^{6.24} and 10^{6.59} M$_\odot$, low oxygen abundances 12+log O/H of 7.75 and 7.45, high velocity dispersions reaching $\sigma$ ~700 and ~1200km/s, high terminal velocities of the stellar wind of ~1000 and ~1000-1700km/s, respectively, and large EW(H$\beta$) of ~300A for both. For SBS 1420+540, we succeeded in capturing an eruption phase by monitoring the variations of the broad-to-narrow component flux ratio. We observe a sharp increase of that ratio by a factor 4 in 2017 and a decrease by about an order of magnitude in 2023. The peak luminosity of ~10^{40}ergs/s of the broad component in $L$(H$\alpha$) lasted for about 6 years out of a three-decades monitoring. This leads us to conclude that there is probably a LBV candidate (LBVc) in this galaxy. As for J1444+4840, its very high $L$(H$\alpha$) of about 10^{41}ergs/s, close to values observed in active galactic nuclei (AGNs) and Type IIn Supernovae (SNe), and the variability of no more than 20 per cent of the broad-to-narrow flux ratio of the hydrogen and helium emission lines over a 8-year monitoring do not allow us to definitively conclude that it contains a LBVc. On the other hand, the possibility that the line variations are due to a long-lived stellar transient of type LBV/SNIIn cannot be ruled out., Comment: 14 pages, 9 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society

[Abridged] Using the JWST/NIRSpec observations from CEERS we found an extreme N-emitter, CEERS-1019 at z=8.6782 showing intense NIV and NIII emission. From the observed rest-UV and optical lines we conclude that it is compatible with photoionization from stars and we determine accurate abundances for C, N, O, and Ne, relative to H, finding a highly supersolar ratio log(N/O) = -0.18+/-0.11, and normal log(C/O) = -0.75+/-0.11 and log(Ne/O) = -0.63+/-0.07, for its low metallicity, 12+log(O/H)= 7.70+/-0.18. We also analyze other N-emitters from the literature. All show strongly enhanced N/O ratios and two of them normal C/O. Massive star ejecta from WR stars are needed to explain the galaxies with enhanced C/O (Lynx arc and Mrk 996). On the other hand, supermassive stars (>1000 Msun, SMS) in the ``conveyer-belt model'' put forward to explain globular clusters (GCs), predict a high N/O and small changes in C/O, compatible with CEERS-1019, the Sunburst cluster, SMACS2031, and GN-z11. Based on the chemical abundances, possible enrichment scenarios, compactness, and high ISM density, we suggest that CEERS-1019, SMACS2031, and the Sunburst cluster could contain proto-GCs. Finally, we propose that some N-emitters enriched by SMS could also have formed intermediate-mass black holes, and we suggest that this might be the case for GN-z11. Our observations and analysis reinforce the suggested link between some N-emitters and proto-GC formation, which is supported both by empirical evidence and quantitative models. Furthermore, the observations provide possible evidence for the presence of supermassive stars in the early Universe (z>8) and at z~2-3. Our analysis also suggests that the origin and nature of the N-emitters is diverse, including also objects like GN-z11 which possibly host an AGN., Comment: Accepted for publication in A&A, 19 pages, 9 figures, 4 tables

Entropy measures are effective features for time series classification problems. Traditional entropy measures, such as Shannon entropy, use probability distribution function. However, for the effective separation of time series, new entropy estimation methods are required to characterize the chaotic dynamic of the system. Our concept of Neural Network Entropy (NNetEn) is based on the classification of special datasets in relation to the entropy of the time series recorded in the reservoir of the neural network. NNetEn estimates the chaotic dynamics of time series in an original way and does not take into account probability distribution functions. We propose two new classification metrics: R2 Efficiency and Pearson Efficiency. The efficiency of NNetEn is verified on separation of two chaotic time series of sine mapping using dispersion analysis. For two close dynamic time series (r = 1.1918 and r = 1.2243), the F-ratio has reached the value of 124 and reflects high efficiency of the introduced method in classification problems. The electroenceph-alography signal classification for healthy persons and patients with Alzheimer disease illustrates the practical application of the NNetEn features. Our computations demonstrate the synergistic effect of increasing classification accuracy when applying traditional entropy measures and the NNetEn concept conjointly. An implementation of the algorithms in Python is presented., Comment: 26 pages, 18 figures, 2 tables

In the quasi-gasdynamic high-current ion source described in this work, the plasma is sustained by high-power millimeter-wave radiation under the electron cyclotron resonance (ECR) condition. In such facilities, it is possible to achieve high volumetric energy input of up to $250$ $W/cm^3$ and obtain pure proton beams with a minimum amount of impurities and molecular ions. Experiments conducted on the GISMO facility demonstrated the possibility of a proton beam formation with a current of $50$ mA and an extremely high ($99.9$\%) content of atomic ions.

Kinetic instabilities in a dense plasma of a continuous ECR discharge in a mirror magnetic trap at the GISMO setup are studied. We experimentally define unstable regimes and corresponding plasma parameters, where the excitation of electromagnetic emission is observed, accompanied by the precipitation of energetic electrons from the magnetic trap. Comprehensive experimental study of the precipitating electron energy distribution and plasma electromagnetic emission spectra, together with theoretical estimates of the cyclotron instability increment proves that under the experimental conditions the observed instability is related to the excitation of whistler-mode waves, which are a driver of losses of energetic electrons from the magnetic trap. The results of this study are important for the further development of the GISMO ECRIS facility and for the improvement of its parameters as an ion source. Also, this research of plasma kinetic instabilities is of fundamental interest and provides experimental tools to simultaneously study plasma electromagnetic activity and corresponding changes in a resonant electron energy distribution., Comment: 9 pages, 9 figures, submitted to Physics of Plasmas

Healthcare digitalization requires effective applications of human sensors, when various parameters of the human body are instantly monitored in everyday life due to the Internet of Things (IoT). In particular, machine learning (ML) sensors for the prompt diagnosis of COVID-19 are an important option for IoT application in healthcare and ambient assisted living (AAL). Determining a COVID-19 infected status with various diagnostic tests and imaging results is costly and time-consuming. This study provides a fast, reliable and cost-effective alternative tool for the diagnosis of COVID-19 based on the routine blood values (RBVs) measured at admission. The dataset of the study consists of a total of 5296 patients with the same number of negative and positive COVID-19 test results and 51 routine blood values. In this study, 13 popular classifier machine learning models and the LogNNet neural network model were exanimated. The most successful classifier model in terms of time and accuracy in the detection of the disease was the histogram-based gradient boosting (HGB) (accuracy: 100%, time: 6.39 sec). The HGB classifier identified the 11 most important features (LDL, cholesterol, HDL-C, MCHC, triglyceride, amylase, UA, LDH, CK-MB, ALP and MCH) to detect the disease with 100% accuracy. In addition, the importance of single, double and triple combinations of these features in the diagnosis of the disease was discussed. We propose to use these 11 features and their binary combinations as important biomarkers for ML sensors in the diagnosis of the disease, supporting edge computing on Arduino and cloud IoT service., Comment: 30 pages, 9 figures, 8 tables, 1 algorithm

Recently, Kojima and co-authors have reported a record low oxygen abundance, 12+logO/H=6.90+/-0.03 in the low-mass star-forming galaxy HSC J1631+4426. This exceptionally low oxygen abundance was obtained by the direct method, using the [OIII]4363 emission line. However, using the strong-line method by Izotov et al. (2019b), these authors have derived a significantly higher metallicity 12+logO/H=7.175+/-0.005. To clarify the situation, we have obtained new observations of HSC J1631+4426 with the Large Binocular Telescope (LBT)/Multi-Object Dual Spectrograph (MODS). We have derived a higher oxygen abundance, 12+logO/H=7.14+/-0.03, using the direct method, a value similar to the oxygen abundance obtained by the strong-line method. Thus, HSC J1631+4426 has a metallicity close to that of the well known blue compact dwarf galaxy IZw18., Comment: 6 pages, 3 figures, accepted for publication in MNRAS Letters

Deep images and near-IR spectra of galaxies in the field of the lensing cluster SMACS J0723.3-7327 were recently taken in the Early Release Observations program of JWST. Among these, two NIRSpec spectra of galaxies at $z=7.7$ and one at $z=8.5$ were obtained, revealing for the first time rest-frame optical emission line spectra of galaxies in the epoch of reionization, including the detection of the important[OIII]4363 auroral line (see JWST PR 2022-035). We present an analysis of the emission line properties of these galaxies, finding that these galaxies have a high excitation (as indicated by high ratios of [OIII]/[OII], [NeIII]/[OII]), strong [OIII]4363/H$\gamma$, high equivalent widths, and other properties which are typical of low-metallicity star-forming galaxies. Using the direct method we determine oxygen abundances of $12+\log(O/H)=7.9$ in two $z=7.7$ galaxies, and a lower metallicity of $12+\log(O/H)\approx 7.4-7.5$ in the $z=8.5$ galaxy using different strong line methods. More accurate metallicity determinations will require better data. With stellar masses estimated from SED fits, we find that the three galaxies lie close to or below the $z \sim 2$ mass-metallicity relation. Overall, these first galaxy spectra at $z \sim 8$ show a strong resemblance of the emission lines properties of galaxies in the epoch of reionization with those of relatively rare local analogues previously studied from the SDSS. Clearly, the first JWST observations demonstrate already the incredible power of spectroscopy to reveal properties of galaxies in the early Universe., Comment: 6 pages, 6 Figures. Accepted for publication in Astronomy & Astrophysics Letters

The properties that govern the production and escape of hydrogen ionizing photons (Lyman continuum, LyC; with energies >13.6 eV) in star-forming galaxies are still poorly understood, but they are key to identifying and characterizing the sources that reionized the Universe. Here we empirically explore the relationship between the hardness of ionizing radiation and the LyC leakage in a large sample of low-$z$ star-forming galaxies from the recent Hubble Space Telescope Low-$z$ Lyman Continuum Survey. Using Sloan Digital Sky Survey stacks and deep XShooter observations, we investigate the hardness of the ionizing spectra ($Q_{\rm He^+}/Q_{\rm H}$) between 54.4 eV (He$^{+}$) and 13.6 eV (H) from the optical recombination lines HeII 4686A and H$\beta$ 4861A for galaxies with LyC escape fractions spanning a wide range, $f_{\rm esc} \rm (LyC) \simeq 0 - 90\%$. We find that the observed intensity of HeII/H$\beta$ is primarily driven by variations in the metallicity, but is not correlated with LyC leakage. Both very strong ($ \simeq 0.5$) and nonleakers ($ < f_{\rm esc} \rm (LyC) > \simeq 0$) present similar observed intensities of HeII/H$\beta$ at comparable metallicity, between $\simeq 0.01$ and $\simeq 0.02$ for $12 + \log({\rm O/H}) > 8.0$ and $<8.0$, respectively. Our results demonstrate that $Q_{\rm He^+}/Q_{\rm H}$ does not correlate with $f_{\rm esc} \rm (LyC)$, which implies that strong LyC emitters do not show harder ionizing spectra than nonleakers at similar metallicity., Comment: 6 pages, 2 figures, 1 tables. Accepted for publication in A&A Letters. v2: updated to match published version, including new title

We have studied the spectral time variations of candidate luminous blue variable stars (cLBV) in two low-metallicity blue compact dwarf galaxies, DDO 68 and PHL 293B. The LBV in DDO 68, located in HII region #3, shows an outburst, with an increase of more than 1000 times in Halpha luminosity during the period 2008-2010. The broad emission of the HI and HeI lines display a P Cygni profile, with a relatively constant terminal velocity of ~800 km/s, reaching a maximum luminosity L(Halpha) of ~2x10^38 erg/s, with a FWHM of ~1000-1200 km/s. On the other hand, since the discovery of a cLBV in 2001 in PHL 293B, the fluxes of the broad components and the broad-to-narrow flux ratios of the HI and HeI emission lines in this galaxy have remained nearly constant over 16 years, with small variations. The luminosity of the broad Halpha component varies between ~2x10^38 erg/s and ~10^39 erg/s, with the FWHM varying in the range ~500-1500 km/s. Unusually persistent P Cygni features are clearly visible until the end of 2020 despite a decrease of the broad-to-narrow flux ratio in the most recent years. A terminal velocity of ~800 km/s is measured from the P Cygni profile, similar to the one in DDO 68, although the latter is 3.7 more metal-deficient than PHL 293B. The relative constancy of the broad Halpha luminosity in PHL 293B suggests that it is due to a long-lived stellar transient of type LBV/SN IIn., Comment: 12 pages, 7 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society

Dwarf galaxies are by far the most numerous galaxies in the Universe, showing properties that are quite different from those of their larger and more luminous cousins. This review focuses on the physical and chemical properties of the interstellar medium of those dwarfs that are known to host significant amounts of gas and dust. The neutral and ionized gas components and the impact of the dust will be discussed, as well as first indications for the existence of active nuclei in these sources. Cosmological implications are also addressed, considering the primordial helium abundance and the similarity of local Green Pea galaxies with young, sometimes proto-galactic sources in the early Universe., Comment: 29 pages, 10 figures, review article in Galaxies, volume 10

Using the Space Telescope Imaging Spectrograph, we have obtained ultraviolet (UV) spectra from $\sim 1200$ to 2000 \AA\ of known Lyman continuum (LyC) emitting galaxies at low redshift ($z \sim 0.3-0.4$) with varying absolute LyC escape fractions (fesc $\sim 0.01 - 0.72$). Our observations include in particular the galaxy J1243+4646, which has the highest known LyC escape fraction at low redshift. While all galaxies are known Lyman alpha emitters, we consistently detect an inventory of additional emission lines, including CIV 1550, HeII 1640, OIII] 1666, and CIII] 1909, whose origin is presumably essentially nebular. CIV 1550 emission is detected above 4 $\sigma$ in six out of eight galaxies, with equivalent widths of EW(CIV)$=12-15$ Ang for two galaxies, which exceeds the previously reported maximum emission in low-$z$ star-forming galaxies. We detect CIV 1550 emission in all LyC emitters with escape fractions fesc $> 0.1$ and find a tentative increase in the flux ratio CIV 1550/ CIII] 1909 with fesc. Based on the data, we propose a new criterion to select and classify strong leakers (galaxies with fesc $> 0.1$): CIV 1550/ CIII] 1909 $> 0.75$. Finally, we also find HeII 1640 emission in all the strong leakers with equivalent widths from 3 to 8 Ang rest frame. These are among the highest values observed in star-forming galaxies and are primarily due to a high rate of ionizing photon production. The nebular HeII 1640 emission of the strong LyC emitters does not require harder ionizing spectra at $>54$ eV compared to those of typical star-forming galaxies at similarly low metallicity., Comment: 6 pages, 3 figures; Accepted for publication in A\&A Letters

Energy distribution of electrons in the plasma sustained by the electron-cyclotron resonance (ECR) discharge has a complicated shape as a function of various parameters that still remains unknown. Meanwhile, it is an important plasma characteristic. Some methods and approaches give the possibility to estimate or measure the properties of the distributions of the electrons lost from the plasma. One of them, similar to the ion mass spectrometry, was used in this work to obtain such distributions in the non-classical continuous ECR ion source with high (up to $ 50-100$ W/cm$ ^ 3 $) energy input for the first time along with bremsstrahlung spectra. For certain parameters, a threshold-like regime was discovered, which comprised of the bursts of energetic electrons, bremsstrahlung and, supposedly, the development of kinetic instabilities., Comment: 10 pages, 24 figures

We report experimental results of vacuum ultraviolet (VUV) emission from the plasma of an electron cyclotron resonance (ECR) discharge in hydrogen, sustained by powerful millimeter-wavelength radiation of a gyrotron. Distinctive features of the considered discharge are the high plasma density ($10^{13}$ cm$^{-3}$ order of magnitude) and, at the same time, the high electron average energy ($10 - 300$ eV), which makes it possible to significantly increase the efficiency of VUV re-emission of the energy deposited into the plasma by the microwave radiation. Experiments were performed with the plasma confined in a simple mirror trap and heated by pulsed gyrotron radiation $37.5$ GHz / $100$ kW under the ECR condition. The measured volumetric VUV emission power of Lyman-alpha line ($122 \pm 10$ nm) overlapping with the Werner band, Lyman band ($160 \pm 10$ nm), and molecular continuum ($180 \pm 20$ nm) reached $45$, $25$, and $55$ W/cm$^3$, respectively. The total absolute radiation power in these three ranges integrated over the plasma volume is estimated to be $22$ kW i.e. $22$% of the incident microwave power, which matches theoretical predictions. Further optimization of the conditions of the ECR hydrogen discharge sustained by powerful gyrotron radiation provides an opportunity for the development of effective technological VUV sources of a kilowatt power level.

We report on a successful test of a new method for intense ion beam formation using an extraction with inhomogeneous electric field. Its key feature is a special shape of the extraction electrodes providing a higher rate of ion acceleration. It is applicable to any ion source type and could be used to improve performance of a wide range of plasma devices. The proof of concept was carried out using a high-current electron-cyclotron resonance ion source SMIS 37. High efficiency of the new extraction and proton beam formation with a record current density of up to 1.1 A cm-2 was demonstrated.

Available data on the polarization of the secondary proton (as a function of its momentum $K$) in the inelastic ({\it p, p$'$}) reactions with the $^{9}$Be, $^{12}$C, and $^{40}$Ca nuclei and differential cross section data (the momentum distributions) for the reactions at the initial proton energy 1 GeV and scattering angles $\Theta$=21$^\circ$ and $\Theta$=24.5$^\circ$ were analysed in a range of the high momenta $K$ close to the momentum corresponding to the proton elastic scattering off the investigated nucleus. A structure in the polarization and momentum distribution data at the high momenum $K$, related probably to quasi-elastic scattering off a $^{8}$Be-like nucleon cluster inside the nuclei, was observed., Comment: 14 pages, 11 figures

The Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, provides unique possibilities for a new generation of hadron-, nuclear- and atomic physics experiments. The future antiProton ANnihilations at DArmstadt (PANDA or $\overline{\rm P}$ANDA) experiment at FAIR will offer a broad physics programme, covering different aspects of the strong interaction. Understanding the latter in the non-perturbative regime remains one of the greatest challenges in contemporary physics. The antiproton-nucleon interaction studied with PANDA provides crucial tests in this area. Furthermore, the high-intensity, low-energy domain of PANDA allows for searches for physics beyond the Standard Model, e.g. through high precision symmetry tests. This paper takes into account a staged approach for the detector setup and for the delivered luminosity from the accelerator. The available detector setup at the time of the delivery of the first antiproton beams in the HESR storage ring is referred to as the \textit{Phase One} setup. The physics programme that is achievable during Phase One is outlined in this paper., Comment: 35 pages, 15 figures

In this paper we report on a high current density ion beam profile diagnostics with a slit-based system as a reliable method, capable of high thermal load applications. The task arose in frames of a point-like neutron source development for neutron radiography. In previous research, it was suggested to construct such a system as a D-D neutron generator based on the high current gasdynamic ion source, which utilises the plasma of electron cyclotron resonance discharge sustained by powerful millimeter wave gyrotron radiation. This device is able to produce focused D+ beams with a characteristic diameter of 1 mm, total current above 100 mA, and current density at a level of several A/cm^2. Study of such intense beams profile to obtain the best focusing efficiency and minimize neutron producing area appeared to be a challenging task. The paper also demonstrates the possibility of fast neutron imaging with a point-like powerful neutron generator (neutron yield on the level of 10^10 1/s)., Comment: 11 pages, 7 figures, submitted to JINST

The quasilinear model of electron cyclotron resonance (ECR) heating in a mirror magnetic field predicts essential broadening of the electron distribution function in case of bichromatic wave. This may stabilize kinetic instabilities in the electron-cyclotron frequency range resulting in improved performance of ECR ion sources, the effect which is observed in many independent experiments., Comment: 9 pages, 4 figures

Fundamental studies of excitation and non-linear evolution of kinetic instabilities of strongly nonequlibrium hot plasmas confined in open magnetic traps suggest new opportunities for fine-tuning of conventional electron cyclotron resonance (ECR) ion sources. These devices are widely used for the production of particle beams of high charge state ions. Operating the ion source in controlled turbulence regime allows increasing the absorbed power density and therefore the volumetric plasma energy content in the dense part of the discharge surrounded by the ECR surface, which leads to enhanced beam currents of high charge state ions. We report experiments at the ECR ion source at the JYFL accelerator laboratory, in which adopting of a new approach allows to increase the multicharged ion beam current up to two times, e.g. to 95 $\mu$A of O$^{7+}$ achieved with mere 280 W power at 11.56 GHz. A theoretical model supporting and explaining the experimental findings is presented. The study suggests that the controlled turbulence regime has the potential to enhance the beam currents of modern high-performance ion sources, including state-of-the-art superconducting devices., Comment: Submitted to Plasma Sources Sci. Tech

Finding and elucidating the properties of Lyman-continuum(LyC)-emitting galaxies is an important step for our understanding of cosmic reionization. Although the z - 0.3-0.4 LyC emitters found recently show strong optical emission lines, no consistent quantitative photoionization model taking into account the escape of ionizing photons and inhomogenous interstellar medium (ISM) geometry of these galaxies has yet been constructed. We hence construct one- and two-zone photoionization models accounting for the observed LyC escape, which we compare to the observed emission line measurements. We find that one-zone density-bounded photoionization models cannot reproduce the emission lines of the LyC leakers because they systematically underpredict the lines of species of low ionization potential, as [OI] and [SII]. Introducing a two-zone model, with differing ionization parameter and a variable covering fraction and where one of the zones is density-bounded, we show that the observed emission line ratios and escape fractions of the LyC emitters are well reproduced. The [OI] excess, which is observed in some LyC leakers, can be naturally explained in this model, e.g., by emission from low-ionization and low-filling-factor gas. LyC emitters with a high escape fraction (fesc > 38%) are deficient both in [OI]6300A and in [SII]6716,6731A. We also confirm that a [SII] deficiency can be used to select LyC emitter candidates. Finally, we find indications for a possible dichotomy in terms of escape mechanisms for LyC photons between galaxies with relatively low (fesc < 10%) and higher escape fractions. We conclude that two-zone photoionization models are sufficient and required to explain the observed emission line properties of z - 0.3-0.4 LyC emitters. These models provide a first step towards the use of optical emission lines and their ratios as quantitative diagnostics of LyC escape from galaxies., Comment: 16 pages, 11 figures, accepted for publication in Astronomy & Astrophysics, revised by language editor

A new approach to the development of extraction systems capable of forming ion beams with previously inaccessible intensity is proposed. The use of inhomogeneous accelerating field allows to improve the ion beam formation efficiency significantly. The increase of electric field magnitude is achieved by changing the shape of the electrodes only, without increasing the accelerating voltage and decreasing the interelectrode distance. The comparison is made between a new extraction system and a flat traditional one, which is the most common. The use of a new electrode geometry allows to increase the lifetime of the electrodes in sources of intense beams operating in a continuous wave mode. For electron cyclotron resonance ion sources, results demonstrate the possibility to form high-quality ion beams with a current density of more than $1\:A/cm^2$., Comment: 5 pages, 7 figures

We report the first measurement of the average of the electron-proton and positron-proton elastic scattering cross sections. This lepton charge-averaged cross section is insensitive to the leading effects of hard two-photon exchange, giving more robust access to the proton's electromagnetic form factors. The cross section was extracted from data taken by the OLYMPUS experiment at DESY, in which alternating stored electron and positron beams were scattered from a windowless gaseous hydrogen target. Elastic scattering events were identified from the coincident detection of the scattered lepton and recoil proton in a large-acceptance toroidal spectrometer. The luminosity was determined from the rates of M{\o}ller, Bhabha and elastic scattering in forward electromagnetic calorimeters. The data provide some selectivity between existing form factor global fits and will provide valuable constraints to future fits., Comment: 6 pages, 3 figures, submitted to PRL

Using new VLT/XShooter spectral observations we analyse the physical properties of five z~0.3-0.4 confirmed LyC leakers. Strong resonant MgII 2796,2803 emission lines (I(2796,2803)/I(Hbeta)=10-38 per cent) and non-resonant FeII* 2612,2626 emission lines are observed in spectra of five and three galaxies, respectively. We find high electron densities Ne~400cm-3, significantly higher than in typical low-z, but comparable to those measured in z~2-3 star-forming galaxies. The galaxies have a mean value of logN/O=-1.16, close to the maximum values found for star-forming (SF) galaxies in the metallicity range of 12+logO/H=7.7-8.1. All 11 low-z LyC emitting galaxies found by Izotov et al. (2016, 2018), including the ones considered in the present study, are characterised by high EW(Hbeta)~200-400A, high ionisation parameter (log(U)=-2.5 to -1.7), high average ionising photon production efficiency \xi= 10^{25.54} Hz erg-1 and hard ionising radiation. On the BPT diagram we find the same offset of our leakers from low-$z$ main-sequence SFGs as that for local analogues of LBGs and extreme SF galaxies at z~2-3. We confirm the effectiveness of the HeI emission lines diagnostics proposed by Izotov et al. (2017) in searching for LyC leaker candidates and find that their intensity ratios correspond to those in a median with low neutral hydrogen column density N(HI)=10^{17}-5x10^{17} cm-2 that permit leakage of LyC radiation, likely due to their density-bounded HII regions., Comment: 20 pages, 10 figures, accepted for publication in the Monthly Notices of the Royal Astronomical Society

Identifying the mechanisms driving the escape of Lyman Continuum (LyC) photons is crucial to find Lyman Continuum Emitter (LCE) candidates. To understand the physical properties involved in the leakage of LyC photons, we investigate the connection between the HI covering fraction, HI velocity width, the Lyman alpha (LyA) properties and escape of LyC photons in a sample of 22 star-forming galaxies including 13 LCEs. We fit the stellar continua, dust attenuation, and absorption lines between 920 and 1300 A to extract the HI covering fractions and dust attenuation. Additionally, we measure the HI velocity widths of the optically thick Lyman series and derive the LyA equivalent widths (EW), escape fractions (fesc), peak velocities and fluxes at the minimum of the LyA profiles. Overall, we highlight strong correlations between the presence of low HI covering fractions and (1) low LyA peak velocities; (2) more flux at the profile minimum; and (3) larger EW(LyA), fesc(LyA), and fesc(LyC). Hence, low column density channels are crucial ISM ingredients for the leakage of LyC and LyA photons. Additionally, galaxies with narrower HI absorption velocity widths have higher LyA equivalent widths, larger LyA escape fractions, and lower LyA peak velocity separations. This suggests that these galaxies have low HI column density. Finally, we find that dust regulates the amount of LyA and LyC radiation that actually escapes the ISM. Overall, the ISM porosity is one origin of strong LyA emission and enables the escape of ionizing photons in low-z leakers. However, this is not enough to explain the largest fesc(LyC) observed, which indicates that the most extreme LCEs are likely density-bounded along all lines of sight to the observer. Overall, the neutral gas porosity constrains a lower limit to the escape fraction of LyC and LyA photons, providing a key estimator of the leakage of ionizing photons., Comment: Accepted for publication in A&A. 28 pages, 23 figures, 7 tables

PANDA (anti-Proton ANnihiliation at DArmstadt) is planned to be one of the four main experiments at the future international accelerator complex FAIR (Facility for Antiproton and Ion Research) in Darmstadt, Germany. It is going to address fundamental questions of hadron physics and quantum chromodynamics using cooled antiproton beams with a high intensity and and momenta between 1.5 and 15 GeV/c. PANDA is designed to reach a maximum luminosity of 2x10^32 cm^2 s. Most of the physics programs require an excellent particle identification (PID). The PID of hadronic states at the forward endcap of the target spectrometer will be done by a fast and compact Cherenkov detector that uses the detection of internally reflected Cherenkov light (DIRC) principle. It is designed to cover the polar angle range from 5{\deg} to 22{\deg} and to provide a separation power for the separation of charged pions and kaons up to 3 standard deviations (s.d.) for particle momenta up to 4 GeV/c in order to cover the important particle phase space. This document describes the technical design and the expected performance of the novel PANDA Disc DIRC detector that has not been used in any other high energy physics experiment (HEP) before. The performance has been studied with Monte-Carlo simulations and various beam tests at DESY and CERN. The final design meets all PANDA requirements and guarantees suffcient safety margins., Comment: TDR for Panda/Fair to be published

Negative hydrogen ion sources are used as injectors into accelerators and drive the neutral beam heating in ITER. Certain processes in low-temperature hydrogen plasmas are accompanied by the emission of vacuum ultraviolet (VUV) emission. Studying the VUV radiation therefore provides volumetric rates of plasma-chemical processes and plasma parameters. In the past we have used gasdynamic ECR discharge for volumetric negative ion production and investigated the dependencies between the extracted H$^-$ current density and various ion source parameters. It was shown that it is possible to reach up to 80 mA/cm$^2$ of negative ion current density with a two electrode extraction. We report experimental studies on negative hydrogen ion production in a high-density gasdynamic ECR discharge plasma consisting of two simple mirror traps together with the results of VUV emission measurements. The VUV-power was measured in three ranges -- Ly$_\alpha$, Lyman band and molecular continuum -- varying the source control parameters near their optima for H$^-$ production. It was shown that the molecular continuum emission VUV power is the highest in the first chamber while Ly$_\alpha$ emission prevails in the second one. Modifications for the experimental scheme for further optimization of negative hydrogen ion production are suggested.

The paper presents recent results of a "point-like" neutron source development based on a D-D fusion in a D-loaded target caused by its bombardment with a sharply focused deuterium ion beam. These developments are undergoing at the Institute of Applied Physics of Russian Academy of Sciences in order to study a possibility to create an effective and compact device for fast-neutron radiography. Last experiments with a beam produced by a gasdynamic high-current ECR ion source and its focusing with magnetic lens demonstrated that 60 mA of deuterium ions may be constricted to a transversal size of ~1 mm at the focal plane. With a purpose to improve this result in terms of the beam current and its size a combined electrostatic and magnetic focusing system is proposed and analysed. It is shown that combined system may enhance the total beam current and reduce its footprint down to 0.13 mm. All numerical analysis was performed using the IBSimu code.

Results of experimental investigation of the ECR discharge in a single coil magnetic field as an alternative to RF and helicon discharges for wide-aperture dense plasma fluxes production are presented. A possibility of obtaining wide-aperture high density hydrogen plasma fluxes with homogenous transverse distribution was demonstrated in such a system. The prospects of using this system for obtaining high current ion beams are discussed., Comment: Contributed paper at Proceedings of the 18th International Conference on Ion Sources