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Title: | Analiza metoda redukcije fona germanijumskih spektrometara Background reduction methods of germanium spectrometers |
Authors: | Mrđa Dušan | Keywords: | gama-spektrometrija, pasivna zaštita, zakočno zračenje, aktivna zaštita, fonskabrzina brojanja, koincidentni događa;gamma spectrometry, passive shield, bremsstrahlung, active shield, backgroundcount rate , coincidence events | Issue Date: | 15-Jun-2007 | Publisher: | Univerzitet u Novom Sadu, Prirodno-matematički fakultet u Novom Sadu University of Novi Sad, Faculty of Sciences at Novi Sad |
Abstract: | <p>Analizirane su komponente fona germanijumskih spektrometara i predstavljene metode<br />redukcije fonskih događaja.<br />Prikazana je konstrukcija nove Pb zaštite za detektor tipa GMX. Pokazano je da se novi<br />dizajn odlikuje visokim kvalitetom , koji čak prevazilazi kvalitet savremenog komercijalnog<br />pasivnog štita.<br />Olovo, koje se često koristi kao materijal zaštite sadrži Pb-210. Intenzitet gama linije od<br />46.5 keV može biti lako redukovan primenom unutrašnjeg zaštitnog sloja, ali zakočno zračanje<br />uzrokovano beta raspadom njegovog potomka, Bi-210, sa maksimalnom energijom elektrona od<br />1.16 MeV, će doprinositi fonskom gama spektru. Spektar zakočnog zračenja je izračunat<br />numeričkim fitovanjem beta spektra i integracijom Koch-Motz formule. Apsorpcija zakočnog<br />zračenja u olovu i efikasnosti detekcije za GMX HPGe detektor su izračunate primenom<br />algoritma efektivnog prostornog ugla, uz korišćenje korekcije za fotopik / Kompton odnos<br />preseka u Ge.<br />Opisani su operacioni problemi germanijumskog spektometra zaštićenog pasivno sa 12cm<br />olova i aktivno pomoću pet 0.5m x 0.5m x 0.05m plastičnih scintilacionih detektora. Istraženi su<br />efekti aktivnog štićenja od gama zračenja iz okoline, kosmičkih miona i neutrona. Širok opseg<br />impulsa iz plastičnih detektora., koji odgovaraju energetskom opsegu od 160keV-80MeV, je<br />iskorišten za antikioincidentno gate-ovanje.</p> <p>The background components of germanium detectors are analyzed, and methods for<br />background reduction are presented.<br />The construction of the new Pb shield for the GMX type detector is presented. It is shown<br />that the new design has even better shielding performances than commercial passive shield.<br />Lead, which is often used as a shielding material, contains Pb-210. The 46.54 keV<br />γ-intensity of Pb-210 can be easily reduced by an inner lining, but the bremsstrahlung caused by<br />the β-decay of its daughter, Bi-210, with a maximal electron energy of 1.16 MeV, will contribute<br />to the gamma detector background. The spectrum of this bremsstrahlung is calculated by<br />numerically fitting the β-spectrum and integrating the Koch-Motz formula. The absorption of the<br />bremsstrahlung in the lead and detection efficiencies for the HPGe detector are calculated by the<br />effective solid angle algorithm, using corrections for the photopeak/Compton ratio of cross<br />sections in Ge.<br />The operational problems of the gamma ray spectrometer shielded passively with 12 cm of<br />lead and actively by five 0.5 m x 0.5 m x 0.05 m plastic veto shields are described. The active<br />shielding effect from environmental gamma ray, cosmic muons, and neutrons was investigated.<br />Wide range of scintillator pulses, corresponding to the energy range of 160 keV – 80 MeV, was<br />used for anticoincidence gating.</p> |
URI: | https://open.uns.ac.rs/handle/123456789/27865 |
Appears in Collections: | PMF Teze/Theses |
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