Vol.5, No 1, 2007 pp. 33 - 44
DOI 10.2298/FUPCT0701033M
UDC 537.569/.534.8
HOMOGENEOUS GAS PHASE MODELS OF RELAXATION KINETICS IN NEON AFTERGLOW
Vidosav Lj. Marković, Saša R. Gocić, Suzana N. Stamenković
Department of Physics, University of Niš, P.O. BOX 224, 18001 Niš, Serbia
Abstract. The homogeneous gas phase models of relaxation kinetics (application of the gas phase effective coefficients to represent surface losses) are applied for the study of charged and neutral active particles decay in neon afterglow. The experimental data obtained by the breakdown time delay measurements as a function of the relaxation time (memory curve) is modeled in early, as well as in late afterglow. The number density decay of metastable states can explain neither the early, nor the late afterglow kinetics (memory effect), because their effective lifetimes are of the order of milliseconds and are determined by numerous collision quenching processes. The afterglow kinetics up to hundreds of milliseconds is dominated by the decay of molecular neon Ne2+ and nitrogen ions N2+ (present as impurities) and the approximate value of N2+ ambipolar diffusion coefficient is determined. After the charged particle decay, the secondary emitted electrons from the surface catalyzed excitation of nitrogen atoms on the cathode determine the breakdown time delay down to the cosmic rays and natural radioactivity level. Due to the neglecting of number density spatial profiles, the homogeneous gas phase models give only the approximate values of the corresponding coefficients, but reproduce correctly other characteristics of afterglow kinetics from simple fits to the experimental data.
Keywords: electrical breakdown, time delay, memory effect, neon afterglow, nitrogen, metastable states, relaxation kinetics, homogeneous gas phase models
HOMOGENI GASNO FAZNI MODELI RELAKSACIONE KINETIKE U NEONU
U ovom radu koriste se homogeni gasno fazni modeli relaksacione kinetike (tj. opisivanje površinskih gubitaka primenom efektivnih gasno faznih koeficijenata) za proučavanje raspada naelektrisanih i neutralnih aktivnih čestica u neonu. Modelovani su eksperimentalni podaci dobijeni merenjem vremena kašnjenja električnog proboja u funkciji vremena relaksacije (memorijska kriva). Pokazano je da hipoteza sa metastabilnim stanjima ne može objasniti memorijski efekat zbog vrlo kratkog efektivnog vremena života metastabilnih stanja (reda milisekundi u datim uslovima) određenog brojnim sudarnim procesima. Memorijski efekat do stotinu milisekundi je opisan raspadom molekulskih jona neona Ne2+ i azota N2+(prisutnog kao nečistoća) i približno je određena vrednost koeficijenta ambipolarne difuzije jona azota N2+. Nakon raspada naelektisanih čestica pa do nivoa kosmičkog zračenja i prirodne radioaktivnosti okoline, vreme kašnjenja proboja je određeno sekundarnom emisijom elektrona na osnovu energije površinski katalizovane rekombinacije atoma azota na katodi. Zbog zanemarivanja prostornih profila koncentracija, homogeni gasno fazni modeli daju samo približne vrednosti rekombinacionih koeficijenata, ali korektno reprodukuju ostale karakteristike relaksacione kinetike na osnovu jednostavnog fita eksperimentalnih podataka.