Ioannis Madesis

National and Kapodistrian University of Athens | uoa · Department of Nuclear and Particle Physics

Radioactivity in the marine environment, although present since the Earth’s formation, is comparatively understudied in contrast to aerial and terrestrial environments. A thorough examination of the radioactivity levels in aquatic environments can establish a robust foundation for comprehending various geochemical processes and phenomena within the...

Natural radioactivity is examined in soil samples collected from Northwestern Epirus, specifically in Pogoni and Zagori areas. The focus was to determine experimentally the specific activity for naturally occurring isotopes (40K, U and Th series) and the anthropogenic 137Cs, in the samples collected from a generally unexplored area of Greece. The m...

A prototype mobile underwater CdZnTe-based spectrometer was tested under realistic environmental conditions under the scope of the RAMONES Research Programme. Field measurements took place on the island of Milos, which is characterized by the extended hydrothermal vents. A combination of static and dynamic in situ measurements along with analysis o...

Urban parks are typically undisturbed natural locations inside metropolitan areas, attracting human recreation activities. The present work focuses on studying the radioactivity levels in urban parks in the metropolitan areas of Athens, Barcelona, and Bucharest to establish a baseline of the overall environmental load and the associated contributio...

The present work concentrates on the detailed study of various types of γ-radiation spectrometers used mainly for applications. More specifically, various experiments were carried out to characterize and compare two (2) different high-purity germanium (HPGe) detectors, one (1) NaI scintillation detector, three (3) CdZnTe (CZT) detectors with standa...

Among the naturally occurring radioactive materials (NORM), radon and its isotopes 222Rn and 220Rn, being the only gaseous products, have a significant role due to their unique transport properties and common chemical characteristics within the respective decay chains of uranium and thorium. Continuous monitoring of radon emissions has diverse appl...

The harsh environmental conditions in the marine environment pose various constraints on developing efficient instruments to carry out long-term, in situ radioactivity measurements. In addition, the strong attenuation of γ-rays in the water medium, makes remote sensing of such radiation a challenging task. In the present work, we report on the effo...

A decommissioned p-type, co-axial HPGe detector has been recently brought back to operational mode in an effort to build a γ-ray spectroscopy station at the National and Kapodistrian University of Athens dedicated for environmental radioactivity studies. The detector was fully characterized prior to and during its operation to obtain detailed infor...

The scope of this study is to characterize the response of a CdZnTe spectrometer to evaluate its performance for measuring radioactivity in the marine environment. CdZnTe semiconductor detectors have never been used before for such applications. More specifically, a spectrometer with a 4 cm3 CZT crystal was studied under various scenarios, by means...

For more than 40 years since the first ion-atom collision investigations of the two-electron process of electron transfer with excitation and its resonant and nonresonant features, a satisfactory quantum mechanical treatment has been lacking. We present now such a comprehensive transfer excitation treatment using a three-electron atomic orbital clo...

We report on double and single differential cross section measurements of the 1s2s2S2, 1s2s2pP±2, and 1s2s2pP4 doubly excited states produced by single-electron capture in 6–15 MeV collisions of pre-excited C4+(1s2sS3) ions with H2, He, Ne, and Ar targets. Ab initio cross section calculations based on a three active electrons atomic orbital close-c...

The process of the capture of a target electron into the projectile continuum (ECC) is investigated both experimentally and theoretically for collisions of 1.25-6.00 MeV deuterons with multielectron gas targets. Double-differential cross sections (DDCS), d2σ/dωdE, of the ECC cusp-shaped electron peak involving He, Ne, and Ar gas targets were measur...

The Tandem Accelerator Laboratory of NCSR “Demokritos,” Athens, Greece, is presented. A technical description of the laboratory, the installed setups together with currently implemented upgrades and associated funded projects are given. A few highlights as well as future upgrade plans and access possibilities to external users are also presented.

This study focuses on the details of cascade repopulation of doubly excited triply open-shell C 3+ (1s2s2p) 4 P and 2 P ± states produced in 2-18 MeV collisions of C 4+ (1s2s 3 S) with He. Such cascade calculations are necessary for the correct determination of the ratio R of their cross sections, used as a measure of spin statistics [Madesis et al...

We report on C3+(1s2ℓ2ℓ′ L2S+1)-resolved cross sections of electron capture in collisions of swift C4+(1s2s S3) ions with helium and hydrogen. The study focuses on the formation of doubly excited triply open-shell C3+(1s2s2p) P4 and P2± states with emphasis on the ratio R of their cross sections as a measure of spin statistics. Using zero-degree Au...

Synopsis New state-resolved Li-like carbon Auger KLL measurements of mixed-state C ⁴⁺ (1s ² ¹ S, 1s2s ³ S) ions in 6-15 MeV collisions with He are presented. Results of three-electron semiclassical atomic orbital AOCC coupled channel (3eAOCC) calculations are also presented and compared.

Booklet of Abstracts works presented by the participants

Auger KLn lines are observed in high‐resolution electron spectra obtained in collisions of mixed‐state (1s21S,1s2s3S) He‐like beams of 4 MeV B3+ with H2 and 6 MeV C4+ with He targets. Supporting atomic structure calculations show these lines to correspond to doubly excited states, which can be readily populated by electron transfer to the component...

Normalized electron yields of the formation of 2s2p 3,1P states from the metastable states 1s2s 3,1S and from the ground state 1s21S were obtained in 6-18MeV C4+ collisions with H2, He, Ne and Ar gas targets. The method of zero-degree Auger projectile spectroscopy was used to detect electrons emitted in the Auger decay C4+ (2s2p 3,1P) → C5+ (1s) +...

Single electron transfer to the 1s2s 3S long-lived component of the naturally occurring mixed-state(1s2, 1s2s 3S) C4+ion beam in collisions with gas targets was investigated using zero-degree Auger projectile spectroscopy at the Demokritos 5.5 MV tandem accelerator. The observed KLL Auger spectrum contains 1s2s2p 2P and 4P states resulting from dir...

An experimental station has recently been completed with a beam line dedicated to atomic collision physics at the 5.5 MV TANDEM accelerator laboratory of the Institute of Nuclear and Particle Physics (INPP) at the National Center for Scientific Research (NCSR) “Demokritos” in Athens. A Zero-degree Auger Projectile Spectroscopy (ZAPS) apparatus comp...

A gas stripper system has been installed inside the terminal of the Demokritos TANDEM accelerator, in addition to the existing foil stripper system, while two additional post strippers (one gas and one foil) were also installed in the beam line between the analyzing and switching magnets of the accelerator. These installations were necessary for th...

The only existing heavy-ion accelerator in Greece, the 5.5 MV TANDEM at the National Research Center “Demokritos” in Athens has been used to date primarily for investigations centering around nuclear physics. Here, we propose to establish the new (for Greece) discipline of Atomic Physics with Accelerators, a strong field in the EU with important co...

A new accelerator beam line dedicated to atomic collision physics has been constructed as part of the APAPES project that is being carried out at the TANDEM of the NCSR “Demokritos”. Interest in various charge states resulted in the design of a second stripping point after acceleration that was added to the main part of the TANDEM accelerator after...

University of Crete (UoC) has initiated the research initiative APAPES funded by THALES‡ that has already set up a new experimental station with a beam line dedicated solely on basic atomic physics research. This new experiment utilizing Zero-degree Auger Projectile Spectroscopy (ΖΑPS) is located at the 5 MV TANDEM accelerator of the National Cente...

The use of mixed-state ionic beams in collision dynamics investigations is examined. Using high resolution Auger projectile spectroscopy involving He-like ( 1 s 2 1 S , 1 s 2 s 3 , 1 S ) mixed-state beams, the spectrum contributions of the 1 s 2 s 3 S metastable beam component is effectively separated and clearly identified. This is performed with...

The use of mixed-state ionic beams in collision dynamics investigations is examined. Using high resolution Auger projectile spectroscopy involving He-like ($1s^2\thinspace^1\!S, 1s2s\thinspace^{3,1}\!S$) mixed-state beams, the spectrum contributions of the $1s2s\thinspace^3\!S$ metastable beam component is effectively separated and clearly identifi...

In zero-degree Auger projectile spectroscopy (ZAPS), electrons are measured with high energy resolution at 0° with respect to the beam direction and state-selective cross sections can be determined. However, for Auger electrons from long-lived projectile states such as the 1s2s2pPJ4 (with lifetimes ranging from ns to ms depending on atomic number Z...

Effective solid angle correction factors for two high resolution electrostatic spectrometers - a hemispherical and a tandem parallel plate – are determined using SIMION Monte Carlo simulations. Results are compared to experimental correction factors directly determined from Auger spectra produced by 1s ionization in collisions of 6.6 MeV C²⁺ (1s²2s...

We have recently build a new experimental station with a beam line dedicated to atomic collision physics at the 5 MV TANDEM accelerator of the Institute of Nuclear and Particle Physics at the National Research Center " Demokritos " in Athens, Greece. A complete zero-degree Auger projectile spectroscopy apparatus composed of a single stage hemispher...

The methodology and results of a detailed four-element lens optimization analysis based on electron trajectory numerical simulations are presented for a hemispherical deflector analyzer (HDA), whose entry aperture size is determined by the injection lens itself and is therefore virtual. Trajectory calculations were performed using both the boundary...

We have investigated the voltage settings for the 4-element injection lens of a biased paracentric hemispherical deflection analyzer (HDA) with virtual entry aperture using numerical methods. The two lens electrode voltages were varied as free parameters while the electron optical properties of the analyzer were calculated from trajectories with te...

We present the unique benefits of gas and foil pre- and post- stripping in the production of pure ground state (1s?), as well as mixed (1s?, 1s2s) state He-like beams. The availability of such beams in TANDEM accelerators is of vital importance in studies concerning the population mechanisms of the 1s2s2p ?P metastable states produced in collisions...

We investigate the energy resolution and line shape of a biased paracentric hemispherical deflector analyzer considering the distance between the exit focal plane and the detection plane. Equipped with a piezoelectrically controlled location of a 2D position sensitive detector we were able to accurately determine the optimum conditions for best ene...

We demonstrate an experimental approach to the solid angle correction needed for the metastable 1s2s2p ^4P state obtained in ion-atom collisions with gaseous targets. By applying a small bias voltage VGC on the target gas cell, the ^4P contributions are separated into two peaks one arising from inside (which is shifted by e_{VGC}) and the other out...

The Optimization of a 4-Element Input Lens on a Hemispherical Deflector Analyzer Using SIMION - Volume 21 Issue S4 - TJM Zouros, A. Kanellakopoulos, I. Madesis, A. Dimitriou, M. Fernández-Martín, G. Martinez, T.J. Mertzimekis

We present SIMION 8.1 Monte Carlo type simulations of the response function and detection solid angle for long lived Auger states (lifetime τ ∼ 10−9 − 10−5 s) recorded by a hemispherical spectrograph with injection lens and position sensitive detector used for high resolution Auger spectroscopy of ion beams. Also included in these simulations for t...

The new research initiative APAPES (http://apapes.physics.uoc.gr/) has already established a new experimental station with a beam line dedicated for atomic collisions physics research, at the 5 MV TANDEM accelerator of the National Research Centre "Demokritos" in Athens, Greece. A complete zero-degree Auger projectile spectroscopy (ZAPS) apparatus...