Πρωτότυπο παρακεντρικό ημισφαιρικό φασματόμετρο υψηλής απόδοσης για φασματοσκοπία Auger Ηλεκτρονίων μηδέν μοιρών

A novel high-efficiency paracentric hemispherical spectrograph for zero-degree auger projectile spectroscopy

Μπενής, Εμμανουήλ Π

Τζούρος, Θεόδωρος

The basic aim of this work is to describe in detail the implementation of a state of the art hemispherical spectrograph into the zero-degree Auger projectile spectroscopy technique and to provide new absolute differential cross section measurements utilizing very weak intensity beams and/or low cross section processes. A secondary task is the investigation of the spectrograph focusing and dispersive properties independently of the experimental technique, due to the non-conventional paracentric entry in combina- tion with the PSD and the focusing/decelerating lens system in use. Binary encounter electrons along with the (2p 2 ) 1 D RTE state, both produced in collisions of 21.6 MeV F 8+ with H2 targets were utilized for the study of the spectrograph operational proper- ties. The study was completed with simulations using the ion optics simulation package SIMION and with the theoretical investigation of the ideal 1/r electrostatic potential of a paracentric hemispherical de ector analyser. It is explicitly shown that the para- centric entry improves the analyser focusing properties. An eΖciency factor of about 300 - 1,000 compared to the KSU tandem parallel plate analyser slit spectrometer has been established for low intensity beams. Using the ZAPS technique with the new high-eΖciency spectrograph the BEe peak enhancement factors for the collision system B (2-5)+ H2, at impact energies of 0.4{1.2 MeV/u were studied. Impulse Approxi- mation Elastic Scattering Model calculations are shown to be in very good agreement with the measurements. These results were used for the in situ calibration of the elec- tron detection eΖciency. In addition, utilizing the low intensity boron beams available at the tandem Van de Graa accelerator,first systematic measurements on the B q+ (q = 1,2,3) spectroscopy, obtained from collisions of 4-8 MeV B(2-4)+ ions with H2 targets was accomplished. These results showed the formation of the (2s2p 2 ) 2 D Li-like B 2+ triply excited state in a single ion{atom collision. Furthermore, the metastable (1s2s) 3 S component oftheB 3+ beam was determined, a result of potential importance for the determination of absolute cross sections in ion{atom collisions involving the B 3+ ions. Finally, first measurements on the single differential cross sections (SDCSs) and Resonance Excitation collision strengths (ΩRE) ofthe B 3+ (2p 2 ) 1 D and B 3+ (1s2p 2 ) 2 D Resonance Transfer and Excitation (RTE) states were obtained. Impulse Approxima- tion calculations for RTE followed by Auger decay (RTEA) are seen to be in good agreement with the measurements. (EN)

Τύπος Εργασίας--Διδακτορικές διατριβές

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Πανεπιστήμιο Κρήτης

E-Locus Ιδρυματικό Καταθετήριο

Elocus

Αγγλική γλώσσα

2001-09-11

2001-12-0

uch.physics.phd//2001benis

http://elocus.lib.uoc.gr:443/dlib/d/f/7/metadata-dlib-2001benis.tkl

Σχολή/Τμήμα--Σχολή Θετικών και Τεχνολογικών Επιστημών--Τμήμα Φυσικής--Διδακτορικές διατριβές