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Selection and design of ion sources for use at the Holifield radioactive ion beam facilitya) (1994)

Alton, G. D. ; Haynes, D. L. ; Mills, G. D. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Review of Scientific Instruments 65 (1994), S. 2012-2018

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ISSN: 1089-7623

Source: AIP Digital Archive

Topics: Physics , Electrical Engineering, Measurement and Control Technology

Notes: The Holifield Radioactive Ion Beam Facility now under construction at the Oak Ridge National Laboratory will use the 25 MV tandem accelerator for the acceleration of radioactive ion beams to energies appropriate for research in nuclear physics; negative ion beams are, therefore, required for injection into the tandem accelerator. Because charge exchange is an efficient means for converting initially positive ion beams to negative ion beams, both positive and negative ion sources are viable options for use at the facility. The choice of the type of ion source will depend on the overall efficiency for generating the radioactive species of interest. Although direct-extraction negative ion sources are clearly desirable, the ion formation efficiencies are often too low for practical consideration; for this situation, positive ion sources, in combination with charge exchange, are the logical choice. The high-temperature version of the CERN-ISOLDE positive ion source has been selected and a modified version of the source designed and fabricated for initial use at the facility because of its low emittance, relatively high ionization efficiencies, and species versatility, and because it has been engineered for remote installation, removal, and servicing as required for safe handling in a high-radiation-level ISOL facility. The source will be primarily used to generate ion beams from elements with intermediate to low electron affinities. Prototype plasma-sputter negative ion sources and negative surface-ionization sources are under design consideration for generating radioactive ion beams from high-electron-affinity elements. The design features of these sources and expected efficiencies and beam qualities (emittances) will be described in this report.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.1144805

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Selection and design of ion sources for use at the Holifield Radioactive Ion Beam Facility (abstract)a) : Proceedings of 5th international conference on ion sources (1994)

Alton, G. D. ; Haynes, D. L. ; Mills, G. D. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Review of Scientific Instruments 65 (1994), S. 1391-1391

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ISSN: 1089-7623

Source: AIP Digital Archive

Topics: Physics , Electrical Engineering, Measurement and Control Technology

Notes: The Holifield Radioactive Ion Beam Facility now under construction at the Oak Ridge National Laboratory will use the 25-MV tandem accelerator for the acceleration of radioactive ion beams to energies appropriate for research in nuclear physics; negative ion beams are, therefore, required for injection into the tandem accelerator. Because charge exchange is an efficient means for converting initially positive ion beams to negative ion beams, both positive and negative ion sources are viable options for use at the facility. The choice of the type of ion source will depend on the overall efficiency for generating the radioactive species of interest. Although direct-extraction negative ion sources are clearly desirable, the ion formation efficiencies are often too low for practical consideration; for this situation, positive ion sources, in combination with charge exchange, are the logical choice. The high-temperature version of the CERN-ISOLDE positive ion source has been selected and a modified version of the source designed and fabricated for initial use at the facility because of its low emittance, relatively high ionization efficiencies and species versatility, and because it has been engineered for remote installation, removal and servicing as required for safe handling in a high-radiation-level ISOL facility. The source will be primarily used to generate ion beams from elements with intermediate to low ionization potentials. Prototype plasma-sputter negative ion sources and negative surface-ionization sources are under design consideration for generating radioactive ion beams from high-electron-affinity elements. The design features of these sources and expected efficiencies and beam qualities (emittances) will be described in this report.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.1144970

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Errors associated with estimating parasitism using a modified version of Southwood's graphical method (1990)

Groden, E. ; Drummond, F. A. ; Casagrande, R. A. ; [et al.]

Springer

BioControl 35 (1990), S. 335-346

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ISSN: 1573-8248

Keywords: Southwood's method ; estimation ; parasitism ; sampling ; Méthode de Southwood ; estimation ; parasitisme ; échantillonnage

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Description / Table of Contents: Résumé Un modèle de simulation est utilisé pour examiner les erreurs dans l'estimation des densités d'hôtes parasités et non parasités indépendamment avec la technique graphique de Southwood. Cette technique est exacte quand l'attaque du parasitoïde a lieu avant la période d'échantillonnage. Quand ceci n'est pas le cas, la densité d'hôtes parasités est estimée exactement mais la densité d'hôtes non parasités est surestimée par ces individus qui sont échantillonnés comme vivants avant l'attaque. Cette erreur est négligeable aux faibles niveaux de parasitisme (〈20%), mais elle augmente avec l'accroissement du parasitisme. Des paramètres biologiques testés, seul le modèle d'attaque du parasitoïde (forme de la courbe d'attaque du parasitoïde) a une influence significative sur la valeur de cette erreur. Un modèle de simulation généralisé est présenté pour évaluer les erreurs dans l'estimation du parasitisme saisonnier pour les interactions spécifiques hôte-parasitoïde.

Notes: Abstract A simulation model is used to examine the errors in estimating parasitized and nonparasitized host densities independently with Southwood's graphical technique. This technique is accurate when parasitoid attack occurs prior to the sampling period (e.g. the previous life stage of the host). When this is not the case, the parasitized host density is estimated accurately, but the unparasitized host density is over estimated by those individuals that are sampled as healthy prior to attack. This error is neglible at low levels of parasitism (〈20% parasitized), but increases with increasing parasitism. Of the biological parameters tested, only the parasitoid attack pattern (shape of the parasitoid attack curve) has a significant influence on the magnitude of this error. A generalized simulation model is presented for evaluating errors in estimates of seasonal parasitism for specific host-parasitoid interactions.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02375257

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