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1.
J Comp Pathol ; 203: 31-35, 2023 May.
Artigo em Inglês | MEDLINE | ID: mdl-37244160

RESUMO

The Greenland shark (Somniosus microcephalus) is a large species of shark found in the North Atlantic and Arctic Oceans and is believed to be the longest living vertebrate. Relatively little is known about its biology, abundance, health or diseases. In March 2022, only the third reported UK stranding of this species occurred and it was the first to undergo post-mortem examination. The animal was a sexually immature female, measuring 3.96 m in length and 285 kg in weight, and was in poor nutritional state. Gross findings included haemorrhages in the skin and soft tissues, particularly of the head, and silt in the stomach suggestive of live stranding, bilateral corneal opacity, slightly turbid cerebrospinal fluid (CSF) and patchy congestion of the brain. Histopathological findings included keratitis and anterior uveitis, fibrinonecrotic and lymphohistiocytic meningitis of the brain and proximal spinal cord and fibrinonecrotizing choroid plexitis. A near pure growth of a Vibrio organism was isolated from CSF. This is believed to be the first report of meningitis in this species.


Assuntos
Monitoramento Ambiental , Tubarões , Animais , Feminino , Regiões Árticas
2.
Nat Commun ; 14(1): 1707, 2023 03 27.
Artigo em Inglês | MEDLINE | ID: mdl-36973246

RESUMO

Escherichia albertii is a recently identified gastrointestinal bacterial pathogen of humans and animals which is typically misidentified as pathotypes of diarrhoeagenic Escherichia coli or Shigella species and is generally only detected during genomic surveillance of other Enterobacteriaceae. The incidence of E. albertii is likely underestimated, and its epidemiology and clinical relevance are poorly characterised. Here, we whole genome sequenced E. albertii isolates from humans (n = 83) and birds (n = 79) isolated in Great Britain between 2000 and 2021 and analysed these alongside a broader public dataset (n = 475) to address these gaps. We found human and avian isolates typically (90%; 148/164) belonged to host-associated monophyletic groups with distinct virulence and antimicrobial resistance profiles. Overlaid patient epidemiological data suggested that human infection was likely related to travel and possibly foodborne transmission. The Shiga toxin encoding stx2f gene was associated with clinical disease (OR = 10.27, 95% CI = 2.98-35.45 p = 0.0002) in finches. Our results suggest that improved future surveillance will further elucidate disease ecology and public and animal health risks associated with E. albertii.


Assuntos
Infecções por Enterobacteriaceae , Infecções por Escherichia coli , Animais , Humanos , Reino Unido/epidemiologia , Infecções por Enterobacteriaceae/epidemiologia , Infecções por Enterobacteriaceae/veterinária , Infecções por Enterobacteriaceae/microbiologia , Aves , Escherichia coli , Genômica , Infecções por Escherichia coli/epidemiologia , Infecções por Escherichia coli/veterinária
3.
Sci Rep ; 12(1): 15055, 2022 09 05.
Artigo em Inglês | MEDLINE | ID: mdl-36064956

RESUMO

The influence of supplementary feeding of wildlife on disease transmission and its consequent impacts on population dynamics are underappreciated. In Great Britain, supplementary feeding is hypothesised to have enabled the spread of the protozoan parasite, Trichomonas gallinae, from columbids to finches, leading to epidemic finch trichomonosis and a rapid population decline of greenfinch (Chloris chloris). More recently, chaffinch (Fringilla coelebs), has also declined markedly from the second to fifth commonest bird in Britain. Using citizen science data, we show that both declines were driven primarily by reduced adult survival, with the greatest reductions occurring in peri-domestic habitats, where supplementary food provision is common. Post-mortem examinations showed a proportional increase in chaffinch trichomonosis cases, near-contemporaneous with its population decline. Like greenfinches, chaffinches often use supplementary food, but are less associated with human habitation. Our results support the hypothesis that supplementary feeding can increase parasite transmission frequency within and between common species. However, the dynamics behind resultant population change can vary markedly, highlighting the need for integrating disease surveillance with demographic monitoring. Other species susceptible to T. gallinae infection may also be at risk. Supplementary feeding guidelines for wildlife should include disease mitigation strategies to ensure that benefits to target species outweigh risks.


Assuntos
Doenças das Aves , Tentilhões , Tricomoníase , Trichomonas , Animais , Animais Selvagens , Doenças das Aves/parasitologia , Tentilhões/parasitologia , Humanos , Tricomoníase/parasitologia , Reino Unido/epidemiologia
4.
Sci Rep ; 12(1): 10298, 2022 06 18.
Artigo em Inglês | MEDLINE | ID: mdl-35717348

RESUMO

Following the first detection in the United Kingdom of Usutu virus (USUV) in wild birds in 2020, we undertook a multidisciplinary investigation that combined screening host and vector populations with interrogation of national citizen science monitoring datasets to assess the potential for population impacts on avian hosts. Pathological findings from six USUV-positive wild passerines were non-specific, highlighting the need for molecular and immunohistochemical examinations to confirm infection. Mosquito surveillance at the index site identified USUV RNA in Culex pipiens s.l. following the outbreak. Although the Eurasian blackbird (Turdus merula) is most frequently impacted by USUV in Europe, national syndromic surveillance failed to detect any increase in occurrence of clinical signs consistent with USUV infection in this species. Furthermore, there was no increase in recoveries of dead blackbirds marked by the national ringing scheme. However, there was regional clustering of blackbird disease incident reports centred near the index site in 2020 and a contemporaneous marked reduction in the frequency with which blackbirds were recorded in gardens in this area, consistent with a hypothesis of disease-mediated population decline. Combining results from multidisciplinary schemes, as we have done, in real-time offers a model for the detection and impact assessment of future disease emergence events.


Assuntos
Doenças das Aves , Infecções por Flavivirus , Flavivirus , Aves Canoras , Animais , Surtos de Doenças/veterinária , Flavivirus/genética , Infecções por Flavivirus/epidemiologia , Infecções por Flavivirus/veterinária , Mosquitos Vetores , Reino Unido/epidemiologia
5.
J Wildl Dis ; 57(2): 467-470, 2021 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-33822168

RESUMO

Avian knemidokoptosis, caused by knemidokoptid mites (Knemidokoptinae: Epidermoptidae), has been reported in wild and domestic birds globally. We report two cases of severe knemidokoptosis in Dunnocks (Prunella modularis) from separate sites in Great Britain, where the disease has previously been reported predominantly in finches and, less frequently, in corvids.


Assuntos
Doenças das Aves/parasitologia , Infestações por Ácaros/veterinária , Ácaros/classificação , Aves Canoras/parasitologia , Animais , Doenças das Aves/epidemiologia , Doenças das Aves/patologia , Inglaterra/epidemiologia , Infestações por Ácaros/epidemiologia , Infestações por Ácaros/parasitologia , Infestações por Ácaros/patologia
6.
Euro Surveill ; 25(41)2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-33063656

RESUMO

In August 2020, as part of a long-term disease surveillance programme, Usutu virus was detected in five Eurasian blackbirds (Turdus merula) and one house sparrow (Passer domesticus) from Greater London, England. This was initially detected by reverse transcription-PCR and was confirmed by virus isolation and by immunohistochemical detection of flavivirus in tissues. Phylogenetic analysis identified Usutu virus African 3.2 lineage, which is prevalent in the Netherlands and Belgium, suggesting a potential incursion from mainland Europe.


Assuntos
Doenças das Aves/epidemiologia , Surtos de Doenças , Flavivirus/isolamento & purificação , Vigilância de Evento Sentinela/veterinária , Animais , Animais Selvagens , Aves , Flavivirus/genética , Filogenia , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Análise de Sequência , Reino Unido/epidemiologia
7.
Vet Rec ; 187(10): e86, 2020 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-32826344

RESUMO

BACKGROUND: When suspect Vibrio cholerae were cultured from fish at ZSL London Zoo, investigations were carried out to determine whether they were possible causes of cholera. METHODS: Bacterial culture was carried out on fish examined postmortem and colonies were identified using standard techniques including the API 20NE biochemical test kits. Suspect isolates were submitted to the Public Health England laboratory for additional testing. Separately, a number of fish were submitted for routine histopathology. RESULTS: On 13 occasions between 2014 and 2018, suspected V cholerae were cultured from individuals of eight different freshwater fish species. Archived cultures for eight of these (from six different fish species) were investigated and seven isolates (from five fish species) were confirmed as V cholerae, but all were non-O1, non-O139 strains. Whole-genome sequencing showed that the five fish species had unique V cholerae multilocus sequence types (three isolates from Aphanius danfordii were identical), all of which were genetically distant from human isolates. CONCLUSIONS: There was no evidence that these isolates could cause cholera. Histopathological changes consistent with vibriosis were seen in several fish, suggesting that V cholerae were causing the disease, but there were also concurrent infections or predisposing stress factors.


Assuntos
Cólera/veterinária , Doenças dos Peixes/microbiologia , Vibrio cholerae/isolamento & purificação , Animais , Animais de Zoológico , Cólera/microbiologia , Peixes , Londres
8.
Rev Sci Instrum ; 91(1): 013330, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-32012539

RESUMO

The AC component of a beam current extracted from a negative hydrogen (H-) ion source was detected through a 0.1 mm wide, 66.5 mm long entrance slit to observe the spatial distribution. An internal antenna type multicusp source driven by a 2 MHz radio frequency (RF) power delivered beams to an electrostatic accelerator coupled to a pair of magnetic lenses. The local beam intensity measured by a Faraday cup after the entrance slit exhibited an oscillation showing two main frequency components: the RF power supply frequency and the frequency two times the driving RF. The frequency spectrum of the detected signal showed sharp peaks at 2 MHz, 4 MHz, and 6 MHz as well as at 3 MHz and 5 MHz. A 1 mm displacement of the Faraday cup slit position from the center of the beam axis increased the oscillation amplitude, corresponding to a larger amplitude of the AC component at the beam edge.

9.
J Wildl Dis ; 55(4): 874-878, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31166852

RESUMO

Two adult Great Spotted Woodpeckers (Dendrocopos major) from separate sites in Great Britain were examined postmortem in 2013 and 2016. A Salmonella sp. was isolated from multiple tissues in both birds. Histopathology and immunohistochemistry confirmed disseminated salmonellosis. Whole-genome sequencing and biochemical analyses putatively identified both isolates as a novel variant of Salmonella enterica subsp. enterica serovar Hessarek (S. Hessarek). Salmonellosis has seldom been reported in Piciformes, and never before in association with S. Hessarek infection. These findings, therefore, add to current knowledge regarding the range of wild bird species susceptible to this Salmonella serovar, and our understanding of the pathogens affecting Great Spotted Woodpeckers, in particular.


Assuntos
Doenças das Aves/microbiologia , Aves/microbiologia , Salmonelose Animal/microbiologia , Salmonella/classificação , Animais , Evolução Fatal , Feminino , Masculino
10.
J Zoo Wildl Med ; 50(1): 183-189, 2019 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-31120677

RESUMO

Listeria monocytogenes is a ubiquitous environmental bacterium that causes disease in a wide range of species. Infection with this pathogen is most frequently diagnosed in ruminant livestock, but is also known to infect people and occasionally wildlife. Postmortem examinations of Western European hedgehogs (Erinaceus europaeus) in Great Britain (2011-2017) identified five (5/266, 2%, 95% confidence interval: 0.8-4.3%) animals with L. monocytogenes infection. The L. monocytogenes isolates comprised three serogroup 1/2a and two serogroup 4 from three multilocus sequence types (2, 37, and 121), all of which were different by single-nucleotide polymorphism analysis, indicating they were distinct and epidemiologically unrelated. These findings are consistent with hedgehogs contracting sporadic infection from the environment, perhaps through eating soil-dwelling invertebrates. Examination of data from scanning surveillance programs focused on other British wildlife species indicates that the hedgehog is one of the wildlife species from which L. monocytogenes has been most frequently identified to date in Great Britain. However, further studies of multiple taxa with comparable sampling efforts are required to assess the relative frequency of L. monocytogenes infection in different wildlife species. The bacterium was isolated from extraintestinal sites in multiple hedgehogs, which may indicate septicemia. However, histological examination was limited and could not discriminate subclinical infection from disease (i.e., listeriosis). Although L. monocytogenes is a zoonotic pathogen, disease in people is typically contracted from the ingestion of contaminated foods. The risk to immunocompetent people of contracting listeriosis from hedgehogs is considered very low to negligible.


Assuntos
Ouriços , Listeria monocytogenes/fisiologia , Listeriose/veterinária , Animais , Autopsia/veterinária , Feminino , Listeria monocytogenes/classificação , Listeria monocytogenes/genética , Listeria monocytogenes/isolamento & purificação , Listeriose/microbiologia , Listeriose/patologia , Masculino , Reino Unido
11.
Dis Aquat Organ ; 133(1): 19-24, 2019 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-30997881

RESUMO

A wild adult female common toad Bufo bufo found dead in Scotland in September 2016 was observed to have hepatomegaly, a large soft tissue mass in the coelomic cavity (2.7 g, 3.5 × 2.3 × 1.8 cm) and numerous dark-red papules (1-2 mm diameter) in the skin and subjacent tissue over the back and dorsal aspects of the limbs. Histopathological examination identified marked hepatitis and coelomitis associated with pigmented fungal hyphae, which are results consistent with a diagnosis of phaeohyphomycosis. Sequencing of the internal transcribed spacer region and the D1-D2 region of the large subunit of the ribosomal RNA gene from affected liver tissue identified the presence of Exophiala (Chaetothyriales) sp., a black yeast previously identified as a cause of amphibian phaeohyphomycosis. To our knowledge, this is the first published report of Exophiala sp. in a wild or captive amphibian in Europe and the first description of phaeohyphomycosis affecting a free-living amphibian in Great Britain. Exophiala spp. are saprobes and opportunistic pathogens. It has been postulated that phaeohyphomycosis is a disease of immunocompromised amphibians; however, we found no evidence of significant concurrent infection or generalised debility in this common toad. Phaeohyphomycosis appears to be a sporadic cause of mortality in amphibians, and this report adds to the growing list of pathogens known to affect wild amphibians in Europe.


Assuntos
Exophiala , Feoifomicose , Animais , Bufo bufo , Europa (Continente) , Feminino , Feoifomicose/veterinária , Escócia , Reino Unido
12.
Sci Rep ; 8(1): 14670, 2018 10 10.
Artigo em Inglês | MEDLINE | ID: mdl-30305642

RESUMO

Proliferative leg skin lesions have been described in wild finches in Europe although there have been no large-scale studies of their aetiology or epizootiology to date. Firstly, disease surveillance, utilising public reporting of observations of live wild finches was conducted in Great Britain (GB) and showed proliferative leg skin lesions in chaffinches (Fringilla coelebs) to be widespread. Seasonal variation was observed, with a peak during the winter months. Secondly, pathological investigations were performed on a sample of 39 chaffinches, four bullfinches (Pyrrhula pyrrhula), one greenfinch (Chloris chloris) and one goldfinch (Carduelis carduelis) with proliferative leg skin lesions and detected Cnemidocoptes sp. mites in 91% (41/45) of affected finches and from all species examined. Fringilla coelebs papillomavirus (FcPV1) PCR was positive in 74% (23/31) of birds tested: a 394 base pair sequence was derived from 20 of these birds, from all examined species, with 100% identity to reference genomes. Both mites and FcPV1 DNA were detected in 71% (20/28) of birds tested for both pathogens. Histopathological examination of lesions did not discriminate the relative importance of mite or FcPV1 infection as their cause. Development of techniques to localise FcPV1 within lesions is required to elucidate the pathological significance of FcPV1 DNA detection.


Assuntos
Doenças das Aves , Tentilhões , Ácaros , Papillomaviridae , Infecções por Papillomavirus , Dermatopatias Infecciosas , Animais , Doenças das Aves/metabolismo , Doenças das Aves/parasitologia , Doenças das Aves/patologia , Doenças das Aves/virologia , Tentilhões/parasitologia , Tentilhões/virologia , Infecções por Papillomavirus/metabolismo , Infecções por Papillomavirus/parasitologia , Infecções por Papillomavirus/patologia , Dermatopatias Infecciosas/metabolismo , Dermatopatias Infecciosas/parasitologia , Dermatopatias Infecciosas/patologia , Dermatopatias Infecciosas/virologia , Reino Unido
13.
Sci Rep ; 8(1): 2449, 2018 02 05.
Artigo em Inglês | MEDLINE | ID: mdl-29402927

RESUMO

The impacts of hedgehog (Erinaceus europaeus) Salmonella infection on public health and on animal welfare and conservation are unknown. We isolated Salmonella Enteritidis multi-locus sequence-type (ST)183 from 46/170 (27%) hedgehog carcasses (27 S. Enteritidis phage type (PT)11, 18 of a novel PT66 biotype and one with co-infection of these PTs) and from 6/208 (3%) hedgehog faecal samples (4 PT11, 2 PT66) from across Great Britain, 2012-2015. Whole genome phylogenetic analysis of the hedgehog isolates and ST183 from people in England and Wales found that PT11 and PT66 form two divergent clades. Hedgehog and human isolates were interspersed throughout the phylogeny indicating that infections in both species originate from a common population. PT11 was recovered from hedgehogs across England and Scotland, consistent with endemic infection. PT66 was isolated from Scotland only, possibly indicating a recent emergence event. People infected with ST183 were four times more likely to be aged 0-4 years than people infected by the more common ST11 S. Enteritidis. Evidence for human ST183 infection being non-foodborne included stronger correlation between geographic and genetic distance, and significantly increased likelihood of infection in rural areas, than for ST11. These results are consistent with hedgehogs acting as a source of zoonotic infection.


Assuntos
Vetores de Doenças , Ouriços/microbiologia , Linfadenite Histiocítica Necrosante/epidemiologia , Infecções por Salmonella/epidemiologia , Salmonella enteritidis/genética , Zoonoses/epidemiologia , Animais , Técnicas de Tipagem Bacteriana , Pré-Escolar , Fezes/microbiologia , Feminino , Genótipo , Linfadenite Histiocítica Necrosante/microbiologia , Humanos , Lactente , Recém-Nascido , Masculino , Tipagem de Sequências Multilocus , Filogenia , Infecções por Salmonella/microbiologia , Infecções por Salmonella/transmissão , Fagos de Salmonella/classificação , Fagos de Salmonella/genética , Fagos de Salmonella/isolamento & purificação , Salmonella enteritidis/classificação , Salmonella enteritidis/isolamento & purificação , Salmonella enteritidis/patogenicidade , Reino Unido/epidemiologia , Zoonoses/microbiologia , Zoonoses/transmissão
14.
Rev Sci Instrum ; 87(2): 02A727, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26931945

RESUMO

Ion species ratio of high current positive hydrogen/deuterium ion beams extracted from an electron-cyclotron-resonance ion source for International Fusion Materials Irradiation Facility accelerator was measured by the Doppler shift Balmer-α line spectroscopy. The proton (H(+)) ratio at the middle of the low energy beam transport reached 80% at the hydrogen ion beam extraction of 100 keV/160 mA and the deuteron (D(+)) ratio reached 75% at the deuterium ion beam extraction of 100 keV/113 mA. It is found that the H(+) ratio measured by the spectroscopy gives lower than that derived from the phase-space diagram measured by an Allison scanner type emittance monitor. The H(+)/D(+) ratio estimated by the emittance monitor was more than 90% at those extraction currents.

15.
Rev Sci Instrum ; 87(2): 02A739, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26931957

RESUMO

The objective of linear IFMIF prototype accelerator is to demonstrate 125 mA/CW deuterium ion beam acceleration up to 9 MeV. The injector has been developed in CEA Saclay and already demonstrated 140 mA/100 keV deuterium beam [R. Gobin et al., Rev. Sci. Instrum. 85, 02A918 (2014)]. The injector was disassembled and delivered to the International Fusion Energy Research Center in Rokkasho, Japan. After reassembling the injector, commissioning has started in 2014. Up to now, 100 keV/120 mA/CW hydrogen and 100 keV/90 mA/CW deuterium ion beams have been produced stably from a 10 mm diameter extraction aperture with a low beam emittance of 0.21 π mm mrad (rms, normalized). Neutron production by D-D reaction up to 2.4 × 10(9) n/s has been observed in the deuterium operation.

16.
Ecohealth ; 12(4): 689-92, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26242215

RESUMO

Streptococcus pyogenes, a common pathogen of humans, was isolated from the carcass of a free-living European hedgehog (Erinaceus europaeus) found in northern England in June 2014. The animal had abscessation of the deep right cervical lymph node, mesenteric lymph nodes and liver. The S. pyogenes strain isolated from the lesions, peritoneal and pleural cavities was characterised as emm 28, which can be associated with invasive disease in humans. This is the first known report of S. pyogenes in a hedgehog and in any free-living wild animal that has been confirmed by gene sequencing. As close associations between wild hedgehogs and people in England are common, we hypothesise that this case might have resulted from anthroponotic infection.


Assuntos
Animais Selvagens/microbiologia , Ouriços/microbiologia , Infecções Estreptocócicas/epidemiologia , Infecções Estreptocócicas/transmissão , Streptococcus pyogenes/isolamento & purificação , Zoonoses/microbiologia , Zoonoses/transmissão , Animais , Transmissão de Doença Infecciosa , Inglaterra/epidemiologia , Zoonoses/epidemiologia
17.
J Wildl Dis ; 50(4): 986-9, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-25121405

RESUMO

A European Robin (Erithacus rubecula) found dead in England had marked blepharitis and periocular alopecia associated with Aprocta cylindrica (Nematoda: Aproctidae) and concurrent mixed fungal infections. Aprocta cylindrica should be considered a differential diagnosis in periocular abnormalities of robins and other insectivorous, migratory passerines in Western Europe.


Assuntos
Doenças das Aves/parasitologia , Nematoides/classificação , Infecções por Nematoides/veterinária , Passeriformes , Animais , Doenças das Aves/epidemiologia , Dermatite/parasitologia , Dermatite/patologia , Dermatite/veterinária , Infecções por Nematoides/epidemiologia , Infecções por Nematoides/parasitologia , Reino Unido/epidemiologia
18.
PLoS One ; 9(2): e88968, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24586464

RESUMO

The importance of wild bird populations as a reservoir of zoonotic pathogens is well established. Salmonellosis is a frequently diagnosed infectious cause of mortality of garden birds in England and Wales, predominantly caused by Salmonella enterica subspecies enterica serovar Typhimurium definitive phage types 40, 56(v) and 160. In Britain, these phage types are considered highly host-adapted with a high degree of genetic similarity amongst isolates, and in some instances are clonal. Pulsed field gel electrophoresis, however, demonstrated minimal variation amongst matched DT40 and DT56(v) isolates derived from passerine and human incidents of salmonellosis across England in 2000-2007. Also, during the period 1993-2012, similar temporal and spatial trends of infection with these S. Typhimurium phage types occurred in both the British garden bird and human populations; 1.6% of all S. Typhimurium (0.2% of all Salmonella) isolates from humans in England and Wales over the period 2000-2010. These findings support the hypothesis that garden birds act as the primary reservoir of infection for these zoonotic bacteria. Most passerine salmonellosis outbreaks identified occurred at and around feeding stations, which are likely sites of public exposure to sick or dead garden birds and their faeces. We, therefore, advise the public to practise routine personal hygiene measures when feeding wild birds and especially when handling sick wild birds.


Assuntos
Doenças das Aves/transmissão , Infecções por Salmonella/transmissão , Salmonella typhimurium/isolamento & purificação , Zoonoses/epidemiologia , Animais , Doenças das Aves/epidemiologia , Doenças das Aves/microbiologia , Aves , Eletroforese em Gel de Campo Pulsado , Inglaterra/epidemiologia , Humanos , Infecções por Salmonella/epidemiologia , País de Gales/epidemiologia
19.
Rev Sci Instrum ; 83(2): 02A716, 2012 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-22380225

RESUMO

A pair of permanent magnets has formed enough intensity to realize electron cyclotron resonance condition for a 14 GHz microwave in a 2 cm diameter 9 cm long alumina discharge chamber. A three-electrode extraction system assembled in a magnetic shielding has formed a stable beam of negative hydrogen ions (H(-)) in a direction perpendicular to the magnetic field. The measured H(-) current density was about 1 mA∕cm(2) with only 50 W of discharge power, but the beam intensity had shown saturation against further increase in microwave power. The beam current decreased monotonically against increasing pressure.


Assuntos
Hidrogênio/química , Micro-Ondas , Radiometria/instrumentação , Eletrodos
20.
Rev Sci Instrum ; 83(2): 02B120, 2012 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-22380277

RESUMO

A strongly focusing He(+) ion beam source equipped with concave multi-aperture electrodes was developed for production of He(-) through a charge exchange cell. The beam was extracted at a voltage less than 20 kV from 301 apertures distributed in an area of 100 mm φ, and focused at 750 mm distance. The beam current and the beam size of 2 A and 20 mm in diameter, respectively, were achieved with an arc power less than 10 kW. The optimum perveance was obtained at 0.02 A∕kV(1.5) at the beam energy less than 20 keV which is suitable for the conversion to He(-) in an alkali vapor cell.

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