scholarly journals Atomic Physics at the 5 MV Tandem at Demokritos: the UoC APAPES project

2019 ◽  
Vol 23 ◽  
pp. 65
Author(s):  
I. Madesis ◽  
A. Dimitriou ◽  
S. Doukas ◽  
A. Laoutaris ◽  
C. Nounis ◽  
...  
Keyword(s):  
Atomic Physics ◽  
Mixed State ◽  
Ground State ◽  
Ion Beam ◽  
Tandem Accelerator ◽  
Angle Correction ◽  
Research Initiative ◽  
Zero Degree ◽  
Gas Targets ◽  
Set Up

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 Center for Scientific Research (NCSR) “Demokritos” in Athens, and has been put together to perform high resolution studies of electrons emitted during ion-atom collisions. The apparatus consists of a Hemispherical Deflector Analyzer (HDA) combined with a 2-dimensional Position Sensitive Detector (PSD) and a doubly-differentially pumped gas cell containing the gas-target. The goal is to perform a systematic isoelectronic investigation of K-Auger spectra emitted from pre-excited and ground state He-like ions in collisions with gas targets using novel techniques. So far, various Auger electron spectra produced through collisions of mixed state (1s2, 1s2s3S) C4+ ion beam with various gas targets have been recorded. In addition, detailed simulations using SIMION have also explored the optimal lens voltages and the solid angle correction factors for long-lived metastable states. A terminal gas stripper system is scheduled to be installed in the accelerator, extending its range of available charge states and enabling the production of pure ground state as well as mixed state beams with different metastable fractions, a measurement vital to APAPES. Here, we report on the progress made up to date on the APAPES project, the description of the apparatus, updated results and plans for the near future.

scholarly journals Zero-degree Auger Projectile Electron Spectroscopy of Li-like Ions obtained in Collisions of 1s2s 3S He-like Ions with Gaseous Targets

2019 ◽  
Vol 24 ◽  
pp. 1
Author(s):  
I. Madesis ◽  
A. Laoutaris ◽  
E. P. Benis ◽  
A. Lagoyannis ◽  
M. Axiotis ◽  
...  
Keyword(s):  
High Resolution ◽  
Cross Sections ◽  
Particle Physics ◽  
Ion Beam ◽  
Tandem Accelerator ◽  
Dilute Gas ◽  
Zero Degree ◽  
Gas Targets ◽  
Set Up

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 composed of a single-stage Hemispherical Deflector Analyser (HDA) and a 2-dimensional Position Sensitive Detector (PSD), combined with a doubly differentially pumped gas target has been set up for high resolution studies of electrons emitted from projectile ions at θ = 0◦ with respect to the beam direction in collisions with dilute gas targets. A terminal gas stripper, as well as both a foil and a gas post-stripper, have also been newly installed, enhancing the capabilities of the TANDEM by allowing for the production of more intense, highly charged ion beams, thus complementing and expanding the range of the available energies and charge states of the TANDEM. Using this setup, a systematic isoelectronic investigation of high resolution K-Auger electron spectra emitted from pre-excited ions in collisions with gas targets has been commenced within the APAPES initiative. Here, we present some highlights of this program together with recent results. This investigation is expected to lead to a better understanding of electron capture to excited states of the ion beam and in particular the overlooked role of cascade feeding of metastable states contributing to the capture cross sections, recently a field of contested interpretations awaiting further resolution.

scholarly journals APAPES - Atomic Physics with Accelerators: Projectile Electron Spectroscopy

2019 ◽  
Vol 21 ◽  
pp. 153
Author(s):  
I. Madesis ◽  
A. Lagoyannis ◽  
M. Axiotis ◽  
T. J. Mertzimekis ◽  
M. Andrianis ◽  
...  
Keyword(s):  
Atomic Physics ◽  
Nuclear Physics ◽  
Strong Field ◽  
Ion Beam ◽  
Strong Support ◽  
Heavy Ion ◽  
Collision Dynamics ◽  
Atomic Collisions ◽  
Zero Degree ◽  
Gas Targets

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 contributions to fusion, hot plasmas, astrophysics, accelerator technology and basic atomic physics of ion-atom collision dynamics, structure and technology. This will be accomplished by combining the existing interdisciplinary atomic collisions expertise from three Greek universities, the strong support of distinguished foreign researchers and the high technical ion-beam know-how of the TANDEM group into a cohesive initiative.Using the technique of Zero-degree Auger Projectile Spectroscopy (ZAPS), we shall complete a much needed systematic isoelectronic investigation of K-Auger spectra emitted from collisions of pre-excited ions with gas targets using novel techniques. Our results are expected to lead to a deeper understanding of the neglected importance of cascade feeding of metastable states [1] in collisions of ions with gas targets and further elucidate their role in the non-statistical production of excited three-electron states by electron capture, recently a field of conflicting interpretations awaiting further resolution.

scholarly journals Investigation of the C3+ Auger KLL spectrum obtained in collisions of 6-15 MeV C4+ (1s2, 1s2s 3S) with gas targets

2019 ◽  
Vol 26 ◽  
pp. 125
Author(s):  
I. Madesis ◽  
A. Laoutaris ◽  
E. P. Benis ◽  
T. J. M. Zouros
Keyword(s):  
Cross Sections ◽  
Collision Energy ◽  
Ion Beam ◽  
Tandem Accelerator ◽  
Naturally Occurring ◽  
Zero Degree ◽  
Gas Targets ◽  
A New Technique ◽  
Beam Component

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 direct 2p transfer to the 1s2s 3S. Higher lying (1s2s 3S)nl2,4L states produced by nl transfer (n>2) were also observed and can in principle feed the lower lying 1s2s2p2Pand 4Pstates. However, due to spin selection rules only the quartets have large enough radiative branching ratios resulting in a proposed selective feeding of only the 1s2s2p 4P state by E1 cascades, while minimally affecting the 1s2s2p 2P states. In the absence of cascades, the ratio of cross sections for 2p transfer to the 1s2s 3S state, Rm≡ σm(4P)/σm(2P), is 2 according to spin statistics. However, the 1s2ground state beam component also contributes to the production of the 1s2s2p 2P doublet states by transfer-excitation. To isolate just the 1s2s 3S transfer contribution and compute Rm, a new technique was employed requiring the recording of two KLL spectra, with the same collision energy, but each with appreciably different 1s2s 3S content, varied by stripping techniques. Our determination of Rmshows this to be >2, in agreement with spin statistics, but contrary to the expected 4P enhancement due to cascade feeding. Details of the analysis and results are discussed.

scholarly journals Production of C4+ (2s2p 3,1P) hollow states in collisions of 6-18 MeV C4+ (1s2, 1s2s 3S) mixed-state beams with gas targets

2019 ◽  
Vol 26 ◽  
pp. 133
Author(s):  
A. Laoutaris ◽  
I. Madesis ◽  
E. P. Benis ◽  
T. J. M. Zouros
Keyword(s):  
Ground State ◽  
Collision Energy ◽  
Spin Exchange ◽  
Electron Excitation ◽  
Target Species ◽  
Zero Degree ◽  
Excitation Mechanisms ◽  
Gas Targets ◽  
Ar Gas

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) + e-with high resolution. These states are of particular importance in the detailed study of fundamental excitation mechanisms, i.e. electron-nucleus excitation, electron-electron excitation and electron-electron excitation with spin exchange. Currently, the role of the above mechanisms in the production of the 2s2p 3,1P states is investigated utilizing variable 1s2s 3S metastable fraction beams as a function of collision energy and target species. Our latest results are presented.

scholarly journals Investigation of electron capture in swift C4+ (1s2s 3S) collisions with gas targets using a zero-degree Auger projectile spectroscopy apparatus built with the L45 beam line at the ‘Demokritos’ 5.5MV tandem accelerator

2021 ◽  
Author(s):  
Ιωάννης Μαδέσης
Keyword(s):  
Electron Capture ◽  
Beam Line ◽  
Tandem Accelerator ◽  
Zero Degree ◽  
Gas Targets

Η παρούσα διατριβή εστιάζει ως επί το πλείστον στην μελέτη της παρακάτω διεργασίας κρούσης: C4+(1s2s 3S) + T->C3+ (1s2s2p 4P, 2P±) + T+, κατά την οποία μια υψηλά φορτισμένη δέσμη ηλιοειδών ιόντων C4+ στη μακρόβια, μετασταθή κατάσταση 1s2s 3S συγκρούεται με αέριους στόχους (He, H2). Κατά τη κρούση αυτή, ένα ηλεκτρόνιο από τον στόχο δεσμεύεται στο 2p τροχιακο του ιόντος άνθρακα (ένας μηχανισμός γνωστός ως σύλληψη/ηλεκτρονίου), οδηγώντας στην παραγωγή των διπλά διεγερμένων λιθιοειδών καταστάσεων 1s2s2p 4P (quartet), 1s2s2p 2P- (εν συντομία 2P- ) και 1s2s2p 2P+ (εν συντομία 2P+), (doublet), μεταξύ άλλων που θα συζητηθούν μετέπειτα στο κείμενο. Αυτή η διεργασία κρούσης μπορεί εύκολα να διερευνηθεί πειραματικά, καθώς ο αρχικός 1s2s 3S, ιοντικός σχηματισμός είναι μετασταθής και ως εκ τούτου, συνυπάρχει σε διάφορες αναλογίες με τα 1s2 ιόντα στη θεμελιώδη κατάσταση κατά τη παραγωγή της δέσμης από τον επιταχυντή.Το βασικό ενδιαφέρον στη παραπάνω διεργασία έγκειται στο ερώτημα του αν οι καταστάσεις 4P και 2P± με παρόμοια 1s2s2p ηλεκτρονιακή διάταξη εποικίζονται κατά την 2p σύλληψη σύμφωνα με τη στατιστική των σπιν, δηλαδή κατά τον λόγο R των εκφυλισμών των spin για την quartet προς τις doublets. Η έννοια της εποίκισης σύμφωνα με τη στατιστική των σπιν είναι βασικού ενδιαφέροντος, καθώς οι περισσότεροι μηχανισμοί κατά τη διάρκεια ατομικών κρούσεων θεωρείται ότι ακολουθούν αυτή τη στατιστική. Πιο συγκεκριμένα, έχει βρεθεί ότι στη παραπάνω διεργασία δεν ακολουθεί αυτή τη στατιστική, όπως πρωτοπαρουσιάστηκε το 2004 για ηλιοειδή ιόντα φθορίου (F7+) οδηγώντας σε αμφιλεγόμενα συμπεράσματα. Σε αυτή τη διατριβή, οι διαφορικές ενεργείς διατομές Δσ/ΔΩ προσδιορίζονται για κάθε ένα από τα παραγώμενα 1s2s2p επίπεδα, χρησιμοποιώντας την υψηλής διακριτικής ικανότητας φασματογραφία Auger ηλεκτρονίων ιόντων δέσμης γνωστή ως ZAPS, όπου το παραγόμενο Auger ηλεκτρόνιο eA μετράται στις 0 μοίρες σε σχέση με τη κατεύθυνση της δέσμης. Προς αυτό το σκοπό, μια νέα πειραματική γραμμή L45, μαζί με μια μοναδική, υπερσύγχρονη πειραματική εγκατάσταση δημιουργήθηκε από το μηδέν, στον μοναδικό ερευνητικό επιταχυντή βαρέων ιόντων στην Ελλάδα, τον 5.5 MV tandem Van ded Graaff επιταχυντή (για συντομία tandem), που λειτουργεί από το 1972 στο Ινστιτούτο Πυρηνικής και Σωματιδιακής Φυσικής του Εθνικού Κέντρου Έρευνας Φυσικών Επιστημών "ΔΗΜΟΚΡΙΤΟΣ", στην Αθήνα. Επιπλέον, αυτή η νέα πρωτοβουλία ατομικής φυσικής περιλαμβάνει ουσιώδεις αλλαγές στο υπάρχον υλικό και τρόπο λειτουργίας του επιταχυντή tandem, που χρησιμοποιείται κυρίως για πειράματα πυρηνικής φυσικής με τη πλειονότητα των πειραμάτων να αφορά τη χρήση δεσμών πρωτονίων. Τα πειραματικά αποτελέσματα, με τη χρήση της μεθόδου ZAPS, όσων αφορά τους σχετικούς πληθυσμούς των quartet και doublet καταστάσεων, είναι σε συμφωνία με παλιότερες, διορθωμένες μετρήσεις. Ταυτόχρονα, έγιναν υπολογισμοί από πρώτες αρχές από την ομάδα θεωρητικών του καθ. Alain Dubois - UPMC-Sorbone και CNRS Paris, οι οποίοι περιλαμβάνουν για πρώτη φορά 3 ενεργά ηλεκτρόνια. Αυτά τα παρουσιασμένα αποτελέσματα, επιλύουν την προϋπάρχουσα διαφωνία μεταξύ θεωρίας και πειράματος και εφιστούν την προσοχή στην περιορισμένη προγνωστική ισχύ της frozen core προσέγγισης όσον αφορά την σπιν στατιστική σε ιδιαιτέρως συσχετισμένα δυναμικά ατομικά συστήματα.

scholarly journals The new external ion-beam station at the Demokritos Tandem 5.5 MV accelerator: A unique analytical tool in the fields of cultural heritage and environmental science

2020 ◽  
Vol 16 ◽  
pp. 209
Author(s):  
D. Sokaras ◽  
... Et al.
Keyword(s):  
Nuclear Physics ◽  
Environmental Science ◽  
Ion Beam ◽  
Tandem Accelerator ◽  
Near Surface ◽  
Experimental Parameters ◽  
Set Up ◽  
Non Destructive ◽  
Conductive State

At the 5.5 MV Tandem accelerator of the Institute of Nuclear Physics of NCSR Demokritos, Athens, a new external ion-beam set-up has been recently installed. The aim of this development was to establish a complete experimental set-up integrating the analytical capabilities of the PIXE, RBS and PIGE techniques, so that a complete elemental and near surface structural characterization of samples/artifacts to be attained in an almost non-destructive way and without any limitation concerning their size or conductive state. A careful 3D mechanical drawing optimized the experimental parameters of the set-up so that the special requirements imposed for optimum performance of the aforementioned techniques to be fulfilled.The first applications were focused in the quality control of tagged materials (technologically authentic replicas of attic ceramics and in coatings used by conservators for paintings).

scholarly journals Installation of a gas terminal stripper and a gas/foil post stripper system at the 5.5 MV Demokritos Tandem Van de Graaff accelerator

2019 ◽  
Vol 24 ◽  
pp. 266
Author(s):  
A. Laoutaris ◽  
I. Madesis ◽  
A. Dimitriou ◽  
A. Lagoyannis ◽  
M. Axiotis ◽  
...  
Keyword(s):  
Ground State ◽  
Ion Beams ◽  
Gas Stripping ◽  
Tandem Accelerator ◽  
Selective Determination ◽  
Electron Spectra ◽  
Zero Degree ◽  
Gas Stripper ◽  
Auger Electron Spectra

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 the production of He-like ion beams used in the APAPES‡ project for the investigation of electron capture phenomena in ion-atom collisions using high resolution zero-degree Auger projectile electron spectroscopy in a dedicated experimental setup already in operation since two years. Older measurements have shown that for He-like ion beams foil stripping results in the production of a mixed-state beam (1s2, 1s2s 3S), while gas stripping in the terminal can produce an almost pure ground-state (1s2) beam. Thus, using both strippers, collision measurements will allow for the selective determination of state-selective capture contributions from either the metastable- (1s2s 3S) or the ground-state of the ion by judicious analysis of both associated projectile K-Auger electron spectra. In addition, post-stripping will allow us to obtain ion charge states whose production is not possible with only one stage of stripping.

Resistless Patterning of Magnetic Storage Media Using Ion Projection Structuring

2001 ◽  
Vol 705 ◽  
Author(s):  
A. Dietzel ◽  
R. Berger ◽  
H. Grimm ◽  
C. Schug ◽  
W. H. Bruenger ◽  
...  
Keyword(s):  
Process Development ◽  
Ion Beam ◽  
Silicon On Insulator ◽  
Magnetic Storage ◽  
Magnetic Islands ◽  
Superlattice Structure ◽  
Head Positioning ◽  
Out Of Plane ◽  
Set Up ◽  
The Impact

AbstractCo/Pt thin film multilayers with strong perpendicular anisotropy and out-of-plane coercivities of 5-11 kOe were magnetically altered in areas of local ion beam interaction. The ion irradiations were performed by ion projection through silicon stencil masks fabricated by silicon on insulator (SOI) membrane technology. The ion projector at the Fraunhofer Institute for Silicon Technology (ISiT) was operated at 73 keV ion energy and with a 8.7- fold demagnification. After exposure to 3 × 1014Ar+/ cm2 magnetic islands smaller than 100 nm in diameter were resolved in the Co/Pt multilayersby means of magnetic force microscopy. The impact of different ion species (He+, Ar+ and Xe+) and ion energies (10 – 200 keV) on the multilayer structure was evaluated using Monte Carlo simulations. The ballistic interface intermixing was used to predict magnetic coercivity changes for various irradiation conditions. The simulations revealed that with 73 keV Ar+ and Xe+ ions the irradiation dose could be reduced by a factor of 100 and 400 respectively in comparison to 73 keV He+which was verified in the experiments. X-ray reflectivity measurements confirmed that the Co/Pt superlattice structure is slightly weakened during the irradiation and that the surface smoothness of the media is preserved. Using the Ion Projection Process Development Tool (PDT) at IMS-Vienna concentric data tracks including head positioning servo informations were patterned onto a 1” IBM microdrive™ glass disk which was coated with Co/Pt multilayers. In a single exposure step several tracks within an exposure field of 17 mm in diameter were structured by 2 × 1015He+/ cm2 at 45 keV using a 4- fold demagnification set-up.

Recent Progress in the 3D Experimentation and Simulation of Nanoindents

2007 ◽  
Vol 550 ◽  
pp. 199-204
Author(s):  
N. Zaafarani ◽  
Franz Roters ◽  
Dierk Raabe
Keyword(s):  
Cross Section ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Physically Based Model ◽  
Rotation Direction ◽  
Crystal Rotation ◽  
Crystal Plasticity Model ◽  
Physically Based ◽  
Set Up ◽  
Rotation Map

This work studies the rotations of a (111) Cu single crystal due to the application of a conical nanoindent. With the aid of a joint high-resolution field emission SEM-EBSD set-up coupled with serial sectioning in a focused ion beam (FIB) system in the form of a cross-beam 3D crystal orientation microscope (3D EBSD) a 3D rotation map underneath the indent could be extracted. When analyzing the rotation directions in the cross section planes (11-2) perpendicular to the (111) surface plane below the indenter tip we observe multiple transition regimes with steep orientation gradients and changes in rotation direction. A phenomenological and a physically-based 3D elastic-viscoplastic crystal plasticity model are implemented in two finite element simulations adopting the geometry and boundary conditions of the experiment. While the phenomenological model predicts the general rotation trend it fails to describe the fine details of the rotation patterning with the frequent changes in sign observed in the experiment. The physically-based model, which is a dislocation density based constitutive model, succeeded to precisely predict the crystal rotation map compared with the experiment. Both simulations over-emphasize the magnitude of the rotation field near the indenter relative to that measured directly below the indenter tip. However, out of the two models the physically-based model reveals better crystal rotation angles

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