bluuebunny/crossref_metadata_2025 huggingface dataset:
Charge-transfer dynamics in anion collisions with vicinal nanostepped surfaces
Authors: Shaw J , Monismith D , Zhang Y , Doerr D , Chakraborty H S
Published: June 2020

Synopsis

We investigate the electron dynamics at various monocrystalline metal surfaces with stepped vicinal nanostructures. The unoccupied bands of the surface superlattice are resonantly excited via the charge transfer interaction of the surface with a H− ion which flies by at grazing angles. The ion survival exhibits modulations as a function of the vicinal-terrace size and shows peaks at energies that access the image state subbands.
The missing single-scattering peak in tin ion collisions on Mo and Ru targets
Authors: Rai S , Deuzemann M J , Noordam W , Holleman E , Versolato O O , Hoekstra R
Published: June 2020

Synopsis

We report the absence of single-scattering peaks in collisions of tin ions on Mo and Ru targets. For these systems standard simulation packages as e.g. SRIM predict prominent single-scattering peaks. To identify the potential cause of the single-scattering peak missing, we changed charge state, energy, and species of the projectiles, detected ions and neutrals separately and studied collisions of Kr on Cu which has a similar mass ratio of projectie and target particles.
Modelling interactions of alkali-cation dimers in He clusters
Authors: Alharzali N , Berriche H , Villarreal P , Prosmiti R
Published: June 2020

Synopsis

Doped He droplets constitute an important environment as ultracold homogeneous matrices for spectroscopic studies. Alkali metal dopants have a series of interesting properties due to their unusual bonding behavior. Neutral atoms attached to the surface of the droplet, forming eventually cold molecules via collisions, while charged dopants form solvation shells, related with the low mobility of the ions in experiments. So, investigations on the underlying intermolecular, markedly orientational ionic, forces, and on the miscoscopic structures of alkali-cation-He complexes is essential.
Simulations of proton beam propagation in matter using entropic moment method
Authors: Olivier E , Nguyen-Bui T H , Champion C , Dubroca B
Published: June 2020

Synopsis

Atomic interactions of ions with the penetrated medium lead to a strong evolution of ion charge-state fractions as a function of the target thickness. In this paper, we present a fast and accurate method in order to simulate the slowing-down of ions in matter. Our model relies on the averaging of the transport equation leading to fast simulations of the deposited dose by particles beam. Simulations have been performed for the case of proton beams propagating through water. Results have been compared with Monte Carlo simulations.
Screened independent atom model calculations for electron emission from biologically relevant molecules by proton impact
Authors: Lüdde H J , Horbatsch M , Kirchner T
Published: June 2020

Synopsis

Screened independent atom model calculations for the net ionization of complex biomolecules bom-barded by energetic protons are presented. Scaling relations are examined and a simple parametrization of the cross section results in terms of an analytical formula is suggested.
Elastic and inelastic scattering of positrons from neon
Authors: Babij T , Cheong Z , Machacek J , McEachran R P , Buckman S J , Sullivan J P
Published: June 2020

Synopsis

Data will be presented for positron scattering from neon. As a “simple” target, neon provides a useful target for the testing and exploration of our fundamental understanding of scattering processes. The low-energy, high-resolution positron beamline based at the Australian National Universitywas used to measure elastic differential cross sections and total electronic and ionization cross sections for low energy scattering of positrons from neon. The experimental data presented will be compared to several recent theoretical calculations.
Four-body calculation of energy levels of muonic molecule dtμe in muon catalyzed fusion
Authors: Niiyama M , Yamashita T , Kino Y
Published: June 2020

Synopsis

We investigate dtμe (= d + t + μ + e) four-body system which includes the most important bound states (dtμ)11 in muon catalyzed fusion (μCF). We directly estimate the energy shift more accurately than the previous perturbation calculation. The shift found to be one order of magnitude larger than previous calculation and to be more significant in the calculation of the μCF reaction rate.
Production of cold molecular ions in superfluid helium droplets
Authors: Iguchi A , Otani H , Kuma S , Tanuma H , Azuma T
Published: June 2020

Synopsis

The capability of helium droplets to isolate cryogenic molecular ions at a temperature of 0.4 K is exploited to observe ultracold molecular processes in the RIKEN Cryogenic Electrostatic (RICE) storage ring. The development of a pulsed droplet beam consisting of extremely large helium droplets up to 1011 atoms is a promising step to apply this unique and robust cooling method to a wide variety of molecular ions. Production of ions by photoionization of neutral species inside helium droplets will provide internally cold ions below the ring temperature of 4 K.
Vibrational autodetachment from hot copper dimer anions: breakdown of the Born-Oppenheimer approximation
Authors: Anderson E K , Schmidt-May A F , Najeeb P K , Eklund G , Rosén S , Stockett M H , Chartkunchand K , Kaminska M , Hansen K , Cederquist H , Zettergren H , Schmidt H T
Published: June 2020

Synopsis

The decay of hot copper dimer anions is studied in a cryogenic storage ring. We detect atomic anion and neutral products and determine the fragmentation and vibrational autodetachment (VAD) rates separately. For short storage times the dimer anions predominantly decay by fragmentation of highly rotationally excited ions by tunneling through the rotational barrier. For storage times exceeding 100 ms, however, VAD is dominating. This process is driven by the very weak direct coupling between nuclear and electronic degrees of freedom.
An electrospray ionisation apparatus for gas phase study of biomolecules
Authors: Chiarinelli J , Bolognesi P , Ramillon J M , Rousseau P , Domaracka A , Castrovilli M C , Avaldi L
Published: June 2020

Synopsis

A set-up to study large biomolecules in the gas phase based on an ElectroSpray Ionisation source has been installed at CNR-ISM in Rome, and it is currently under commissioning. Accurate ion optics simulation provide crucial feedback in the understanding and optimisation of its performance.
DNA damage in Thymidyl(3’-5’)thymidine (TpT) induced by very low energy electrons
Authors: Khorsandgolchin G , Lemelin V , Cloutier P , Sanche L , Wagner J R
Published: June 2020

Synopsis

The interaction of high-energy radiation with the biological matter produces copious amounts of non-thermal secondary low energy electrons (LEEs; 0-30 eV). Several studies have shown that 5-15 eV electrons induce different types of DNA damage by the formation of transient negative ions (TNIs), decaying into the dissociative elec-tron attachment (DEA) process [1,2]. Here, our main focus is to understand the chemical mechanism of damage by very low energy electrons (vLEEs∼1.8 eV) by using TpT as a simple model of DNA, solid-state LEE irradiation methods and LC-MS/MS analysis of the degradation products.
Measurement of proton microbeam profiles in atmosphere produced by single tapered glass capillary optics with an end window
Authors: Ikeda T , Ikekame M , Hikima Y , Mori M , Kawamura S , Minowa T , Jin W-G
Published: June 2020

Synopsis

Profiles of 2.8 MeV H+ microbeam extracted from a single tapered glass capillary optics were meas-ured by two methods for a future irradiation to an outer organ of insect target. The halo component was analyzed to be 575 μm in full width at half maximum (FWHM) at a plastic tracking detector CR-39 located 1 mm down-stream of the capillary. The core component was examined by knife-edge method according to the ion energies. The profiles consisting of more energy-loss events have wider FWHM, which can be reduced by Al thin layers.
Real-time trajectory control on a deterministic ion source
Authors: Lopez C , Trimeche A , Comparat D , Picard Y J
Published: June 2020

Synopsis

The major challenge to improve deterministic single ion sources is to control the position and momentum of each ion. Based on the extra information given by the electron created in a photoionization process, the trajectory of the correlated ion can be controlled and corrected using a fast real time feedback system. In this work, we report on a proof-of-principle experiment that demonstrates the performance of this feedback control with individual cesium ions.
Absolute cross sections for production of molecular dications by electron impact
Authors: Sigaud L , Montenegro E C
Published: June 2020

Molecular dications are important metastable species present in a variety of environments including, but not restricted to, planetary atmospheres and the human body when submitted to radiation. On the other hand, symmetric molecular dications cannot be separated from the cation corresponding to the molecule broken in half (e.g.

N
2

+
+

and N+) in stantard mass spectrometers. The DETOF technique allows one to identify the symmetric molecular dication, obtaining absolute cross sections related to their production. Results for dications of molecular nitrogen, molecular oxygen, ethylene and benzene are discussed here, giving emphasis on the mechanisms behind their production. It is seen that, while most metastable molecular dications result from a combination of direct double ionization and Auger-like processes,

N
2

+
+

and

O
2

+
+

represent so-called pure cases, where the dication is produced only by, respectively, double direct ionization or post-collisional Auger-like decay.
Role of methylation in electron scattering on X(CH3)4 (X= C, Si, Ge) molecules
Authors: Stefanowska-Tur Sylwia , Szmytkowski Czesław , Ptasińska-Denga Elżbieta , Możejko Paweł
Published: June 2020

To investigate how replacement of H atom with methyl group (CH3) – in tetrahedral compounds of carbon, silicon and germanium – affects electron scattering process, total cross sections (TCS) for electron scattering from C(CH3)4, Si(CH3)4 and Ge(CH3)4 molecules have been compared with data for CH4, SiH4 and GeH4 molecules. All examined data have been obtained with the same experimental setup. The shape of all discussed TCS energy dependences is very similar and is characterized by a dominant maximum peaked below 10 eV. For methylated compounds a gentle structure is also visible on high energy slope of main enhancement, between 10 – 20 eV. A simple formula for TCS evaluation for partially methylated carbon, silicon and germanium compounds is also proposed.
Atomic processes with twisted electrons
Authors: Zaytsev V A , Surzhykov A , Serbo V G , Kosheleva V P , Groshev M E , Yerokhin V A , Shabaev V M , Stöhlker Th
Published: June 2020

The present status of the fully-relativistic nonperturbative calculations of the fundamental atomic processes with twisted electrons is presented. In particular, the elastic (Mott) scattering, the radiative recombination, and for the very first time, the Bremsstrahlung processes are considered. The electron-ion interaction is accounted for in a nonperturbative manner, that allows obtaining reliable results for heavy systems. We investigate the influence of the “twistedness” of the incoming electron on the angular and polarization properties of the emitted electrons and photons for the elastic and inelastic scattering, respectively. It is found that these properties exhibit a strong dependence on the opening angle of the vortex electron beam in all processes considered.
Collisional cooling of trapped ions with cold atoms: results and insights
Authors: Dutta Sourav , Sawant Rahul , Rangwala S A
Published: June 2020

We present a series of recent experimental and numerical results which allow us to propose and explain the mechanisms for collisional cooling of a trapped ion by sequential binary collisions with atoms. Our experiments in hybrid atom-ion traps study the cooling of ions when the reservoir of the coolant atoms is spatially localized at the centre of the ion trap. Under these conditions the widely and long held expectation that for the ion to collisionally cool, the atom must be of lighter mass (i.e. mI
> mA
) is overturned. Instead we show ion cooling for mI
⩽ mA
in addition to mI
> mA
, and explain why earlier work establishing mass ratios does not apply to the experiments in hybrid traps. Further, for cooling of an ion A+ by the parent atom A, the mechanism of resonant charge exchange (RCE) allows for extremely efficient cooling of the ion A+. This mechanism is demonstrated by comparing the cooling rate of an ion with a localized ensemble of its parent atoms and with a lighter atomic species, where in the latter case the RCE mechanism does not exist. The difference in measured cooling rates for a given number density of the atoms and the theoretically calculated difference between elastic and RCE cross sections are used to show that the cooling efficiency per collision with RCE is much greater than the cooling by elastic collision. We conclude with some perspectives and prospects of future experiments.
Abnormal photoelectron angular distribution of Ar atoms in pulsed XUV and IR laser fields
Authors: Tong XM , Toshima N
Published: June 2020

Synopsis

We calculated the photoelectron angular distribution of Ar atoms in pulsed XUV and IR laser fields by solving the time-dependent Schrödinger equation and found that the angular distributions of sidebands are not always straight lines in the energy-angle plot as predicted by the strong field approximation. Further study shows that the abnormality is attributed to the photoelectron-nucleus Coulomb interaction. The abnormality depends on the IR intensity, IR pulse duration, XUV photon energy and the time-delay between the two pulses.
Fano’s propensity rule in angle-resolved attosecond interferometry
Authors: Busto D , Vinblad J , Zhong S , Isinger M , Nandi S , Gisselbrecht M , L’Huillier A , Lindroth E , Dahlström J M
Published: June 2020

Synopsis

Above-threshold ionization is a corner stone of attsecond science. In this work we extend Fano’s propensity rule to two-photon above-threshold ionization and show that the asymmetry between absorption and emission of the second photon predicted by this propensity rule has strong implications for angle-resolved pump-probe experiments and in particular for attosecond photoelectron interferometry.
Spiral-like Structure: Unwinding Holographic Interference
Authors: Maxwell A S , Lai X Y , Sun R P , Figueira de Morisson Faria C , Liu X J
Published: June 2020

Synopsis

A new spiral shaped holographic interference structure in above-threshold ionisation photoelectron momentum distributions is presented in experimental and theoretical results. Given a large Coulomb interaction and bound-state symmetries encoded in interfering trajectories we demonstrate its use for imaging.
Attosecond time delay in multiphoton ionization
Authors: Yang W , Liu X , Song X , Li P , Chen J
Published: June 2020

Synopsis

Here with a semiclassical picture we show that, after emerging in the continuum state, the photoelectron can be temporarily re-trapped by the atomic potential in a quasi-bound state, stays there for hundreds of at-toseconds before it gets free again, which is the origin of the remarkable time delay in above threshold ionization experiment. Our results build a bridge between the seemingly unrelated quantum EWS and classical Coulomb-induced time delays, and hold promise for intuitive interpreting fundamental electronic processes in photophysical and photochemical experiments.
NewStock, a time-dependent close-coupling program for atomic ionization
Authors: Argenti L , Lindroth E
Published: June 2020

Synopsis

We present NewStock, a time-dependent program to compute the photoionization of polyelectronic atoms by arbitrary light pulses. The program, which expands the capabilities of the Stock B-spline close-coupling structure code to the time-dependent domain, is applied to the pump-probe ionization of the neon atom.
Attosecond delays in photoionization of diatomic and polyatomic molecules
Authors: Loriot V , Marciniak A , Nandi S , Hervé M , Karras G. , Constant E , Lépine F
Published: June 2020

Synopsis

We have investigated the photoionization dynamics of several molecular systems using attosecond in-terferometric techniques based on ultrashort extreme ultraviolet (XUV) pulses. For diatomic molecules such as N2, we can get a detailed picture of the photoionization process by measuring the attosecond delays. For polyatomic molecules such as naphthalene, such measurements can provide the average timescale over which photoionization processes at different electron energies can occur in complex quantum systems.
Ultrafast time-resolved photoelectron and ion fragment momentum imaging of vacuum ultraviolet-excited molecules
Authors: Slaughter D S , Larsen K A , Sturm F P , Belkacem A , Ranitovic P , Weber Th
Published: June 2020

Synopsis

New experimental results are presented on the dissociation dynamics of small neutral molecules in time-resolved photoexcitation-photoionization experiments by ultrashort vacuum- and extreme-ultraviolet laser pulses and charged particle momentum imaging.
Multi-channel contributions to infrared-driven high-harmonic generation in solids
Authors: Navarrete F , Ciappina M F , Thumm U.
Published: June 2020

Synopsis

We numerical and analytically investigate the electron dynamics of high-order harmonic generation (HHG) in solids driven by strong mid-infrared few-cycle laser pulses. Our numerical model distinguishes contributions to the HH yield from (i) intra- and interband transitions and (ii) the central Γ–point of the first Brillouin zone (BZ) versus the entire first BZ of the initial valence band.
Generation of high harmonics in solids
Authors: Floss I , Lemell C , Yabana K , Burgdörfer J
Published: June 2020

Synopsis

We have developed an ab-initio multi-scale simulation to model light synthesis and propagation through transparent media accounting for the non-linear response of the solid. Using this approach we are able to investigate the build-up of high harmonics induced by strong and short laser pulses along the propagation direction inside a large band-gap dielectric, diamond. Detailed analysis of the results allows to identify minimum requirements necessary to realistically model laser-solid interactions.
Disentangling relativistic non-dipole effects in strong field atomic ionisation in non-relativistic regime
Authors: Haram N , Ivanov I , Xu H , Kim K T , Atia-tul-Noor A , Sainadh U S , Litvinyuk I , Sang R T
Published: June 2020

Synopsis

Quantum mechanical description of the relativistic non-dipole effects is of fundamental interest in strong-field physics community, as they may have direct implications on the processes relying on re-collision dynamics. Here, we present a detailed experimental and theoretical study on the relativistic non-dipole effects in strong-field ionisation at moderate intensities. We compare our precise measurements with a truly ab-initio fully relativistic 3D model based on the time-dependent Dirac equation and demonstrate an excellent agreement between experimental results and theoretical predictions.
Effects of relativistic interactions in photodetachment time delay of Br−
Authors: Saha S , Jose J , Deshmukh P C , Kheifets A S , Dolmatov V K , Manson S T
Published: June 2020

Synopsis

Wigner time delay in photodetachment of Br− has been studied. The absence of Coulomb phase in photodetachment process makes the Wigner time delay more sensitive to the centrifugal barrier shape resonance and threshold effects. Important relativistic effects have been found near the threshold region.
Dynamic interference in photoemission by chirped ultrashort extreme ultraviolett pulses
Authors: Wang N , Li G , Liu A , Thumm U
Published: June 2020

Synopsis

We investigated dynamical interference (DI) in the photoionization of hydrogen atoms in intense ultrashort chirped extreme ultraviolett (XUV) pulses by numerically solving the time-dependent Schrödinger equation(TDSE) and examined its dependence on pulse intensity, duration, and chirp. We find the pulse chirp to red shift the photoelectron spectrum and weaken the DI effect.
Application of synthesized tetragonal structured zirconium oxide nanoparticle on victoria blue B and acridine orange dye
Authors: Santhosh A M , Yogendra K , Mahadevan K M , Madhusudhana N
Published: June 2020

Zirconium oxide with the tetragonal phase was prepared from zirconium nitrate and urea by solution combustion method. Nano-photocatalyst zirconium oxide was investigated by XRD, SEM-EDAX, TEM, UV absorbance spectroscopy and specific surface area analysis. The distribution size of ZrO was found to be less than 17nm and was confirmed by XRD and TEM studies. Further the ZrO nano-photocatalyst confirms the tetragonal phase by XRD. EDAX reveals the formation of ZrO. The efficiency of ZrO nanoparticles in the photodegradation of victoria blue B and acridine orange dye under sunlight was investigated. The results reveal that the degradation efficiency was found to be 95.42% for VBB (at 0.030g/pH 6/1×10−4mol/dm3) and 92.52% for AO (at 0.035g/pH 4/1×10−4mol/dm3). Further the degradation efficiency shown highest in VBB dye when compare to AO dye. Therefore, the ZrO nanoparticle has been found to be suitable for the treatment of textile effluents.
A study of dielectric relaxation properties of ZnFe2-xBixO4 nano Ferrites synthesized by sol-gel combustion method
Authors: Kumar N Suresh
Published: June 2020

A series of bismuth doped zinc nano ferrite particles with the r formula ZnBixFe2-xO4 (x = 0.00, 0.05, 0.10, 0.15, 0.20 & 0.25) were prepared by sol-gel combustion method; and these compositions were sintered at 600°C for 5 hrs. With the effect of bismuth doping, the structural properties of all prepared samples were characterized by X-ray diffraction (XRD). The X-ray diffraction spectra analyses confirm single phase cubic (FCC) spinal structure. The average crystallite size (D) of the samples found to be in the range 17-20 nm. The dielectric properties viz., dielectric constant (ε′), dielectric loss tangent (tan δ) and AC conductivity σAC) were measured at room temperature in the range 20Hz to 2MHz, which confirm the normal ferrite behavior. In the present research work, we are intended to extend dielectric relaxation studies of these samples with the help of Cole-Cole plots. The Cole-Cole plots of the bismuth doped zinc ferrites were drawn as a function of ε′ and ε″ (where, ε″=ε′ tan δ) and hence we have determined the spreading factor (β) for all the samples. It was observed that β decreases with the increase of the concentration of B2O3. It is noticed that the dielectric parameters ε′, tan δ and σAC have exhibited the similar trend. These samples may find suitable applications in electrolytic elements in battery technology.
Computational studies of Distinct Anilines for Electrooptical properties
Authors: Prasanti Marla , Jha Anjali , Kumar Ch Ravi Shankar
Published: June 2020

Significant studies of anilines reported biological activities like oxidation, polymerization, arylation, alkylation, protonation, conformation for photophysical and electrochemical properties using experimental and computational studies like CNDO, MINDO, PCILO that arise due to charge transfer interaction. These interactions still provide enough scope with analysis using electron density method to determine physical, chemical and electrooptical properties. The present work attributes family of anilines-aniline(AN),p-chloroaniline(CAN) andp-nitroaniline(NAN) with experimental studies like FTIR and FT Raman and Computational studies with Gauss View4.1 package using B3LYP–basis set 6-311++(d, p) for electrooptical properties. Interpretation of experimental spectra of FTIR and FT Raman confirm the wave numbers are in specified range corresponding to functional group and fingerprint regions. It is observed that intensity of the wave numbers in Raman spectra are reduced in comparison with infrared spectra. Molecular structures are visualized with molecular editor Avogadro for molecular properties. Computational studies are performed for optimized structures wherein the computed infrared spectra and Raman spectra are in agreement with experimental spectra. Studies of charge transfer interactions determine properties like dipole moment, EHomo, ELumo, energy gap, electrophilicity index, polarization and first order hyperpolarizability. A feature of work is NAN possess greater tendency in charge transfer interaction with reduced energy gap, high polarizability and first order Hyperpolarizability that enable to form complex for optical materials and devices.
Recent Developments and Future Advancements in Solar Panels Technology
Authors: Durganjali C Santhi , Bethanabhotla Sameer , Kasina Satwik , Radhika Dr Sudha
Published: June 2020

Although advancements and developments are happening on the electronics part of the solar cell, a steep boost in the research field of material and manufacturing perspective must highlight. Artificial intelligence-based maximum power point tracking algorithms are the future of solar-based circuits. Fabrication of transparent solar cells that have the potential to be used for a vast number of applications, solar cells with more than one layer of light capturing materials. Innovative photovoltaic modules that can lay on roads that can power LED lamps and can melt snow in winter are a few cutting-edge technologies from the materials as well as a manufacturing point of view. Surprisingly they have higher efficiency than traditional solar cells. This paper analyses the recent developments and the future potential of solar panel technologies in the material and manufacturing perspective.
Sol-gel synthesis and electrochemical properties of wolframite FeNbO4
Authors: Saritha D.
Published: June 2020

In the current effort, illustrate a different case FeNbO4 with wolframite structure. FeNbO4 was prepared by sol-gel polymeric precursor method in prospect of estimated prominent specific capacity. One cause is owing to the reduction of both Fe and Nb. The electrochemical lithium insertion/extraction studies on wolframite FeNbO4 were conducted with a rate of C/10 in the potential window of 1.0-3.8V. Ex-situ XRD procedure was used to identify the Structural changes all the way through insertion/extraction of Lithium. The details of synthesis and lithium insertion mechanism in FeNbO4 will be discussed.
X-ray Mass attenuation coefficients of Nb2O5over the energy range 18.9132-19.6882
Authors: Manjula G , Jyothsna S , Kumar A Mahesh , Roy Bunty Rani , Yadav Ashok Kumar , Rao A S Nageswara
Published: June 2020

We use the Extended X-ray absorption fine structure (EXAFS) to measure the mass attenuation coefficient of Nb2O5Niobium compound in the X-ray energy range 18.9132 - 19.6882 keV. The results represent the most extensive experimental data set for Nb2O5and include absolute mass attenuation coefficients in the region of extended x-ray absorption fine structure. Comparison of the results with tabulations of calculated photo electric absorption coefficients indicate the differences between the calculated and observed values with the theoretical predictions.
Temperature dependence of density and thermal expansion of oxides of praseodymium and dysprosium in the temperature range 300 to 1000 K
Authors: RangaRao M. , GopiKrishna N. , Chandra lingam S
Published: June 2020

In this communication the variation of density and thermal expansion of oxides of praseodymium and dysprosium with temperature is studied and reported. The gamma ray attenuation technique is employed to carry out the study with a gamma ray densitometer fitted with high temperature furnace designed in our laboratory. The temperature dependent quantities such as linear gamma ray attenuation (μ
1), density (ρ) and the coefficient of linear thermal expansion (α)of Pr6O11 and Dy2O3 have been fit to a second degree polynomial equation.
Pressure induced semimetallic B2 phase of alkaline earth tellurides
Authors: Kunduru Lavanya , Sripada Suresh , Roshan S. C. Rakesh , Yedukondalu N. , Sainath M.
Published: June 2020

We report pressure induced structural, topological quantum phase transitions and Fermi surface topology in MTe (M = Ca, Sr, Ba) compounds under high pressure using first principles calculations based on density functional theory. MTe compounds undergo a first order structural phase transition from NaCl-type (B1) to CsCl-type (B2) phase at 24.2, 14.7, 4.9 GPa respectively and are consistent with the experimental observations. Electronic structure of MTe compounds were calculated using new parameterization of Tran Blaha-modified Becke Johnson (TB-mBJ) potential and the obtained band gaps are improved over LDA/GGA functionals. The three compounds under investigation are indirect band gap semiconductors at ambient conditions. Under high pressure, B2 phase of (Ca/Sr)Te and BaTe are found to be node-line and Dirac semimetals, respectively without inclusion of spin-orbit coupling.
The MPGD-Based Photon Detectors for the upgrade of COMPASS RICH-1
Authors: Agarwala J. , Dalla Torre S. , Dasgupta S. , Gregori M. , Hamar G. , Levorato S. , Menon G. , Tessarotto F. , Triloki  , Zhao Y.X. , Bradamante F. , Bressan A. , Chatterjee C. , Ciliberti P. , Martin A. , Alexeev M. , Denisov O. , Chiosso M. , Panzieri D. , Azevedo C.D.R. , Veloso J.F.C.A. , Büchele M. , Fischer H. , Herrmann F. , Schopferer S. , Cicuttin A. , Crespo M.L. , Finger M. , Finger M. , Slunecka M. , Sulc M.
Published: June 2020

After pioneering gaseous detectors of single photon for RICH applications using CsI solid state photocathodes in MWPCs within the RD26 collaboration and by the constructions for the RICH detector of the COMPASS experiment at CERN SPS, in 2016 we have upgraded COMPASS RICH by novel gaseous photon detectors based on MPGD technology. Four novel photon detectors, covering a total active area of 1.5 m2, have been installed in order to cope with the challenging effciency and stability requirements of the COMPASS physics programme. They are the first application in an experiment of MPGD-based single photon detectors. All aspects of the upgrade are presented, including engineering, mass production, quality assessment and performance.

Perspectives for further developments in the field of gaseous single photon detectors are also indicated.
A modular mini-pad photon detector prototype for RICH application at the Electron Ion Collider
Authors: Agarwala J. , Azevedo C.D.R. , Chatterjee C. , Cicuttin A. , Ciliberti P. , Crespo M.L. , Dalla Torre S. , Dasgupta S. , Gregori M. , Levorato S. , Menon G. , Tessarotto F. , Zhao Y.X.
Published: June 2020

Experiments at the future Electron Ion Collider require excellent hadron identification in a broad momentum range, in harsh conditions. A RICH capable to fulfill the PID requirements of the EIC could use MPGD-based photon detectors with solid photocathodes for covering large surfaces at affordable cost, providing good effciency, high resolution and compatibility with magnetic field. Photon detectors realized by coupling THGEMs and Micromegas have been successfully operated at the RICH-1 detector of the COMPASS Experiment at CERN since 2016. A similar technology could be envisaged for an EIC RICH, provided a large improvement in the photon position resolution is achieved. An R&D effort in this direction is ongoing at INFN Trieste. Few prototypes with smaller pixel size (down to 3 mm x 3 mm) have been built and tested in the laboratory with X-Ray and UV LED light sources. A modular mini-pad detector prototype has also been tested at the CERN SPS H4 beamline. New data acquisition and analysis software called Raven DAQ and Raven Decoder have been developed and used with the APV-25 based Scalable Readout System (SRS), for the modular mini-pad prototype tests.

The main characteristics of the new mini-pad hybrid MPGD-based detector of single photons are described and preliminary results of laboratory and beam tests are presented.
Study of LTCC-GEM gain properties
Authors: Kato Yukihiro
Published: June 2020

Low Temperature Co-fired Ceramic (LTCC) is an insulator and has been used for electronic circuit boards. The features of LTCC are good electric discharge resistance and high rigidity. A GEM foil using LTCC is expected not to be broken by an electric discharge. The manufactured LTCC-GEM has a hole area of 100 × 100 mm2, the hole diameter is 100 µm, and the hole pitch is 200 µm. We have measured the performance with respect to the gain properties of 200 µm thick LTCC-GEM with 55Fe X-ray. In the measurement, the gain achieved was about 2000 for three gases, ArCO2 (Ar:CO2 = 70:30), P10 (Ar:CH4 = 90:10) and T2K (Ar:CF4:iC4H10 = 95:3:2), and the long-term (100 hours) fluctuation was within 6%. And when the 100 × 100 mm2 LTCC-GEM hole area was divided into 10× 10 mm2, the gain uniformity of the entire region was estimated to be 12%.
A new amplification structure for time projection chambers based on electroluminescence
Authors: González-Díaz D. , Fontaíña M. , García Castro D. , Mehl B. , De Oliveira R. , Williams S. , Monrabal F. , Querol M. , Álvarez V.
Published: June 2020

A simple hole-type secondary scintillation structure (2 mm-hole, 5 mm-pitch, 5 mm-thickness) is introduced and its operation demonstrated in pure xenon in the pressure range 2-10 bar. The new device, characteristically translucent, has been manufactured through a collaboration between IGFAE and the CERN workshop, and relies entirely on radiopure materials (acrylic and copper), being extremely rugged in the presence of sparks, mechanically robust, and easily scalable, yet made through a relatively simple process. With an overall figure (at 10 bar) characterized by an energy resolution of 18.9%(FWHM) for 55Fe x-rays, an optical gain of m
γ
= 500 ph/e, and a stable operation at reduced fields more than twice those of some of the presently running experiments (E

EL
= 3 kV/cm/bar), this family of structures seems to show great promise for electroluminescence readouts on large scale detectors. As argued below, further improvements have the potential of bringing the energy resolution close to the Fano factor and increasing the optical gain.
Study of a Passive Gating Grid for Ion Back Flow Suppression
Authors: Zakharov V , Garg P , Hemmick T , Dehmelt K
Published: June 2020

Space Charge (SC) distortions are some of the main issues for high-resolution Time Projection Chambers (TPC). The two main SC sources are those from primary ionizations and those that result from amplification stages. The gain stages are required to increase the electron (e
-) signal above electronics noise levels, but this inevitably creates extra ions. These ions can enter the drift region and distort the electric field, and thus lower the detector performance. We will present a brief motivation for our Ion Back Flow (IBF) studies along with explanations of existing techniques and our simulation results to reduce IBF. We propose several mesh structures along with static bi-polar gating. Further, we discuss position distortions in e
- trajectories due to a static bi-polar grid and use these distortions to compensate for non-linear responses of our Zig-Zag pad readout.
Characterisation of the charging up effect in resistive Micromegas detectors
Authors: Samarati J , Iengo P , Longo L , Sekhniaidze G , Sidiropoulou O , Wotschack J
Published: June 2020

During the last decade, a major improvement in the field of the Micro-Pattern Gaseous Detectors has been reached by adding a layer of resistive strips above the readout strips to reduce drastically the effect of discharges. The resistive strips are separated from the readout strips by a thin layer of insulator. When the detector is operated some gain reduction is observed over the first seconds or minutes after switch-on, stabilising after some time. Is this related to the presence of the insulator or are there other mechanisms at work? We report here the results of a detailed study of this effect and compare resistive-strip and Diamond Like Carbon (DLC) Micromegas detectors. We will present and quantify the main characteristics of this effect, i.e, the relative gain drop and the time to reach a stable regime, as a function of the detector configuration and rate. In addition we studied the influence of the pillars that support the mesh on the behaviour of bulk and non-bulk Micromegas detectors.
Study of discharge properties in cascaded gaseous detectors
Authors: Maltsev T. , Sauli F. , Shekhtman L.
Published: June 2020

In this work we describe simulation and experimental studies of the possible reasons for the observed increase of the maximum gain in multi-GEM devices. Two main hypotheses are analyzed: first, a diffusion-dominated charge spread reducing the density in individual holes, acting as independent amplifiers and therefore an increase of the discharge limit with the number of cascaded electrodes; second, the possibility that total avalanche charge before transition to a discharge (Raether limit) strongly depends on the field value and is therefore much higher in cascaded than in single-stage systems.
Long term stability study of triple GEM detector using different Argon based gas mixtures: an update
Authors: Chatterjee S , Roy S , Sen A , Chakraborty S , Biswas S , Das S , Ghosh S K , Prasad S K , Raha S
Published: June 2020

The long-term stability in terms of gain and energy resolution of a prototype triple Gas Electron Multiplier (GEM) detector has been investigated with high rate X-ray irradiation. Premixed Ar/CO2 (80:20) and (90:10) gases have been used for this stability study. A strong Fe55 X-ray source is used to irradiate the chamber. The uniqueness of this work is that the same source has been used to irradiate the GEM prototype and also to monitor the spectra. This arrangement is important since it reduces the mechanical complexity of using an X-ray generator as well as the cost of the setup. A small area of the chamber is exposed continuously to the X-ray for the entire duration of the operation. The effect of temperature and pressure on the gain and energy resolution is monitored. The result of the long-term stability test for a triple GEM detector using Ar/CO2 (70:30) gas mixture has been reported earlier [1]. The results with Ar/CO2 (80:20) and (90:10) gas mixtures for the same chamber are presented in this article.
Advanced Aging study on Triple-GEM Detectors
Authors: Fallavollita F , Fiorina D , Merlin J A
Published: June 2020

We present here a new study of the aging of Triple-GEM detectors in contaminated environment. The goal of this experiment is to evaluate the influence of the ionization power of particles on the longevity of the gaseous detectors and therefore determine the best configurations required to reliably reproduce the classical aging phenomena in laboratory. A 100 cm2 triple-GEM detector operating in Ar/CO
2 (70/30%) was irradiated simultaneously with low energy X-rays and 5.5 MeV alpha particles. Hydrocarbons and Si-based molecules were added to the gas mixture in order to accelerate the aging and simulating many years of slow gas pollution. We measured the evolution of the detector performance in two irradiated zones and we performed a systematic chemical analysis of the GEM foils to measure the polymer concentration and thus the potential aging effects. The detector collected a total charge of 165 mC/cm2 in the two irradiated sectors with no performance loss. Chemical analysis revealed a greater Si-based polymers concentration in the region irradiated with alpha particles. This is due to their higher ionization power, with respect to low energy X-rays, which generate denser electron avalanches and, thus, a higher polymerization rate. Further studies have to be performed in order to validate this result, at different experimental conditions and with different detector technologies.
Effect of deformation due to stretching of the Gas Electron Multiplier (GEM) Foil
Authors: Malhotra Shivali , Bouhali Othmane , Al-Tamimi Abdulla , Al-Gammal Mohammad
Published: June 2020

The Gas Electron Multiplier (GEM) was first introduced by Fabio Sauli in 1997, which is a thin layer of an insulating polymer, coated on both sides with copper and chemically perforated with a high density of microscopic holes. The GEM detectors, which are built using GEM foils, have been utilized for various applications due to their excellent spatial resolution, high rate capabilities and flexibility in design. Large area of triple GEM detectors are planned in experiments as it is the case in the upgrade of the CMS forward muon system. During the assembly of these detectors, the GEM foils are manually stretched to maintain the required gap configuration throughout the detector area. This stretching procedure can introduce local variation in the size or the shape of the perforated holes in GEM foil which can further vary the operational characteristics of the foil as well as the detector. Therefore, the distribution and size of the holes over a GEM foil should be uniform to achieve homogeneous functionality of the detector over the active surface. We can prevent the deformation of the perforated holes by optimizing the stretching force which is used during the assembly.
Towards MPGD-based (S)DHCAL
Authors: Shaked Renous D. , Bhattacharya P. , Chefdeville M. , Drancourt C. , Moleri L. , Tesi A. , Coimbra A. , Breskin A. , Bressler S. , Geralis T. , Kajomovitz E. , Karyotakis J. , Vouters G. , Titov M. , Veloso J. , Amaro F.
Published: June 2020

Digital and Semi-Digital Hadronic Calorimeters ((S)DHCAL) were suggested for future Colliders as part of the particle-flow concept. Though studied mostly with Resistive Plate Chambers (RPC), studies focusing on Micro-Pattern Gaseous Detector (MPGD)-based sampling elements have shown the potential advantages using such techniques.

In 2018, eight 48x48 cm2 sampling elements based on resistive Micromegas and Resistive Plate WELL (RPWELL) technologies were assembled. They were tested within a small MPGD-based SDHCAL prototype incorporating in addition three 16x16 cm2 Micromegas detectors and steel absorber plates recording hadronic showers of low-energy pions at the CERN/PS beam line. Preliminary results and analysis methodology are presented, using data samples recorded with pions with momenta in the range from 2 to 6 GeV/c.
3D muography with a gaseous TPC equipped with 2D multiplexed Micromegas
Authors: Gómez H. , Attié D. , Calvet D. , Coppolani X. , Gallois B. , Kebbiri M. , Lehuraux M. , Magnier P. , Mandjavidze I. , Procureur S , Vandenbroucke M.
Published: June 2020

Potential applications of muon tomography, or muography, as non-invasive scanning method have increased in the last years together with the performance of the particle detectors used for muon detection, known as muon telescopes. A new concept muon telescope is presented, which could enlarge even more the range of application of this technique. It is based on a compact TPC equipped with a 2D pixelized Micromegas detector with multiplexed readout. This detector will overcome some of the constraints of the instruments currently used, as they limited acceptance, while keeping other features required for muography as stability, robustness or portability. Moreover, it will be capable to reconstruct the 3D direction of the incident muons with a single instrument.

With its design and features, this kind of detectors can be fitted at boreholes from where they can scan the surroundings, being an interesting technique for mining exploration, geotechnics or monitoring of dykes or bridges which has arouse the interest of industry. In a further phase it is expected to develop a network of these detectors which will allow the 3D reconstruction of the studied object by the combination of the images registered by each of the telescopes. Main features and first tests and results of this new instrument will be presented together with some studies, performed by Monte Carlo simulations, of the capabilities of this muon telescope and the analysis principle.
VMM3a, an ASIC for tracking detectors
Authors: Iakovidis George
Published: June 2020

The VMM3a is a System on Chip (SoC) custom Application Specific Integrated Circuit (ASIC)1. It is the production version which will be used as the front ASIC for both Micromegas and sTGC detectors of the ATLAS Muon New Small Wheels upgrade at CERN. Due to its highly configurable parameters it has been proposed for several tracking detectors and other experiments. It is fabricated in the 130 nm Global Foundries 8RF-DM process. The ASIC integrates 64 channels, each providing charge amplification, discrimination, neighbour logic, amplitude and timing measurements, analog-to-digital conversions, and either direct output for trigger or multiplexed readout within a data-driven readout system. The front-end amplifier can operate with a wide range of input capacitances, has adjustable polarity, gain and peaking time. The ASIC has been tested on resistive Micromegas and sTGC prototypes in test beam campaigns at CERN.
ATLAS NSW Micromegas readout boards: Industrialisation and Quality Control and Quality Assurance
Authors: Farina Edoardo
Published: June 2020

Micromegas with a spark protection scheme were selected as instrumentation of the first forward muon station in the upgrade of the ATLAS detector for the operation of the Large Hadron Collider at high luminosity. The readout boards carrying the readout strips, the resistive anode strips for spark protection and the mesh distance holders (pillars) are industrially produced in Europe. A detailed quality control and quality assurance scheme has been developed and implemented at CERN to closely follow the industrial production. Up to today, about 2000 readout boards have been checked for their quality in a dedicated test facility at CERN. The detailed procedure, highlighting the crucial aspects leading to the rejection or acceptance of an anode board, as well as the statistical overview of the results will be presented.
Development of a Spark-Detection System for the Quality Assurance of Large-Area GEM-Foils
Authors: Ball M , Block T , Hauer P , Ottnad J , Urban S , Ratza V , Ketzer B
Published: June 2020

Gaseous detectors based on large-size GEM-foils are planned to be used for a variety of upgrades and new experiments using high-rate and high-intensity particle beams. An excellent quality control of GEM-foils is a mandatory prerequisite to select the best foils for the assembly of a GEM detector. The high voltage stability of the foils is here of uppermost importance. In particular discharges that occur at the same position need to be detected. A spark detection system has been developed to automatically detect and record the time and position of sparks. The system is based on a commercial web camera installed in a housing for the tests and a custom-made, LabVIEW-based software for control and operation. An automatic Spark-Detection System for GEM foils was designed, built and characterized. It is able to detect and record discharges in large-size GEM foils during the quality control procedure. The spark detection e ciency was estimated to be higher than 97 %, the position resolution was determined to be approximately 0.5 mm. With this system, the characterization of GEM foils can be standardized to a much greater degree than before.
Design and characteristics of ultra-wideband single-layer frequency-selective surface
Authors: Gevorkyan A V
Published: June 2020

The paper presents the design of the developed single-layer frequency-selective surface. Frequency characteristics of reflection and transmission coefficients are given. The operating frequency band of the surface on the level of reflection coefficient less than minus20 dB is in the frequency range from 8.89 to 11.22 GHz. The operating bandwidth is 2.33 GHz or 23.3% relative to 10 GHz. The surface is ultra-wideband in terms of reflection coefficient less than minus 10 dB, and its operating frequency band is in the frequency range from 6.77 to 14.22 GHz.