{"id":17663,"date":"2020-06-16T22:54:34","date_gmt":"2020-06-16T22:54:34","guid":{"rendered":"https:\/\/www.radiation-dosimetry.org\/o-que-e-fotocatodo-e-dinodos-no-tubo-fotomultiplicador-definicao\/"},"modified":"2020-07-21T15:33:12","modified_gmt":"2020-07-21T15:33:12","slug":"o-que-e-fotocatodo-e-dinodos-no-tubo-fotomultiplicador-definicao","status":"publish","type":"post","link":"https:\/\/www.radiation-dosimetry.org\/pt-br\/o-que-e-fotocatodo-e-dinodos-no-tubo-fotomultiplicador-definicao\/","title":{"rendered":"O que \u00e9 fotocatodo e d\u00ednodos no tubo fotomultiplicador &#8211; Defini\u00e7\u00e3o"},"content":{"rendered":"<div class=\"su-quote su-quote-style-default\">\n<div class=\"su-quote-inner su-u-clearfix su-u-trim\">Um fotoc\u00e1todo converte f\u00f3tons em el\u00e9trons atrav\u00e9s do efeito fotoel\u00e9trico.\u00a0No d\u00ednodo, os el\u00e9trons s\u00e3o multiplicados por emiss\u00e3o secund\u00e1ria.\u00a0Dosimetria de Radia\u00e7\u00e3o<\/div>\n<\/div>\n<div class=\"su-divider su-divider-style-dotted\"><\/div>\n<div class=\"lgc-column lgc-grid-parent lgc-grid-100 lgc-tablet-grid-100 lgc-mobile-grid-100 lgc-equal-heights lgc-first lgc-last\">\n<div class=\"inside-grid-column\">\n<figure id=\"attachment_26292\" class=\"wp-caption aligncenter\" aria-describedby=\"caption-attachment-26292\"><a href=\"https:\/\/www.radiation-dosimetry.org\/wp-content\/uploads\/2019\/12\/Scintillation_Counter-Photomultiplier-Tube.jpg\"><img loading=\"lazy\" class=\"wp-image-26292 lazy-loaded\" src=\"https:\/\/www.radiation-dosimetry.org\/wp-content\/uploads\/2019\/12\/Scintillation_Counter-Photomultiplier-Tube-1024x637.jpg\" alt=\"Scintillation_Counter - Tubo Fotomultiplicador\" width=\"416\" height=\"259\" data-lazy-type=\"image\" data-src=\"https:\/\/www.radiation-dosimetry.org\/wp-content\/uploads\/2019\/12\/Scintillation_Counter-Photomultiplier-Tube-1024x637.jpg\" \/><\/a><figcaption id=\"caption-attachment-26292\" class=\"wp-caption-text\">Aparelho com cristal cintilante, fotomultiplicador e componentes de aquisi\u00e7\u00e3o de dados.\u00a0Fonte: wikipedia.org Licen\u00e7a CC BY-SA 3.0<\/figcaption><\/figure>\n<p><strong>Os tubos<\/strong>\u00a0fotomultiplicadores (PMTs) s\u00e3o um dispositivo de detec\u00e7\u00e3o de f\u00f3tons que usa o efeito fotoel\u00e9trico combinado com a emiss\u00e3o secund\u00e1ria para converter luz em um sinal el\u00e9trico.\u00a0Um fotomultiplicador absorve a luz emitida pelo cintilador e a reemite na forma de el\u00e9trons pelo\u00a0<a href=\"https:\/\/www.nuclear-power.com\/nuclear-power\/reactor-physics\/interaction-radiation-matter\/interaction-gamma-radiation-matter\/photoelectric-effect\/\">efeito fotoel\u00e9trico<\/a>\u00a0.\u00a0O PMT tem sido a principal escolha para detec\u00e7\u00e3o de f\u00f3tons desde ent\u00e3o, devido ao fato de terem alta efici\u00eancia qu\u00e2ntica e alta amplifica\u00e7\u00e3o.<\/p>\n<p>O dispositivo consiste em v\u00e1rios componentes e esses componentes s\u00e3o mostrados na figura.<\/p>\n<ul>\n<li><strong>Photocathode<\/strong>\u00a0.\u00a0Logo ap\u00f3s uma fina janela de entrada, existe um fotoc\u00e1todo, feito de material no qual os el\u00e9trons de val\u00eancia est\u00e3o fracamente ligados e t\u00eam uma se\u00e7\u00e3o transversal alta para converter f\u00f3tons em el\u00e9trons pelo efeito fotoel\u00e9trico.\u00a0Por exemplo, Cs\u00a0<sub>3<\/sub>\u00a0Sb (c\u00e9sio-antim\u00f4nio) pode ser usado.\u00a0Como resultado, a luz criada no cintilador atinge o fotocatodo de um tubo fotomultiplicador, liberando no m\u00e1ximo um fotoel\u00e9tron por f\u00f3ton.<\/li>\n<li><strong>D\u00ednodos<\/strong>\u00a0.\u00a0Usando um potencial de voltagem, esse grupo de el\u00e9trons prim\u00e1rios \u00e9 eletrostaticamente acelerado e focado para atingir o primeiro d\u00ednodo com energia suficiente para liberar el\u00e9trons adicionais.\u00a0H\u00e1 uma s\u00e9rie (&#8220;est\u00e1gios&#8221;) de d\u00ednodos feitos de material com fun\u00e7\u00e3o de trabalho relativamente baixa.\u00a0Esses eletrodos s\u00e3o operados com potencial cada vez maior (por exemplo, ~ 100-200 V entre d\u00ednodos).\u00a0No d\u00ednodo, os el\u00e9trons s\u00e3o multiplicados por emiss\u00e3o secund\u00e1ria.\u00a0O pr\u00f3ximo d\u00ednodo tem uma voltagem mais alta, o que faz com que os el\u00e9trons liberados desde o primeiro acelerem em sua dire\u00e7\u00e3o.\u00a0Em cada d\u00ednodo\u00a0<strong>3-4 electr\u00f5es<\/strong>\u00a0s\u00e3o introduzidas em cada electr\u00f5es incidente, e com\u00a0<strong>6 a 14 d\u00ednodos<\/strong>\u00a0o ganho total, ou do factor de amplifica\u00e7\u00e3o de electr\u00f5es, ser\u00e1 na gama de ~\u00a0<strong>10\u00a0<sup>4<\/sup>\u00a0-10<sup>7<\/sup><\/strong>\u00a0quando atingem o \u00e2nodo.\u00a0As tens\u00f5es operacionais t\u00edpicas est\u00e3o na faixa de 500 a 3000 V. No d\u00ednodo final, el\u00e9trons suficientes est\u00e3o dispon\u00edveis para produzir um pulso de magnitude suficiente para amplifica\u00e7\u00e3o adicional.\u00a0Esse pulso carrega informa\u00e7\u00f5es sobre a energia da radia\u00e7\u00e3o incidente original.\u00a0O n\u00famero desses pulsos por unidade de tempo tamb\u00e9m fornece informa\u00e7\u00f5es sobre a intensidade da radia\u00e7\u00e3o.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<div class=\"lgc-column lgc-grid-parent lgc-grid-100 lgc-tablet-grid-100 lgc-mobile-grid-100 lgc-equal-heights lgc-first lgc-last\">\n<div class=\"inside-grid-column\">\n<div class=\"su-spoiler su-spoiler-style-default su-spoiler-icon-arrow\" data-anchor=\"References\">\n<div class=\"su-spoiler-title\" tabindex=\"0\" role=\"button\"><\/div>\n<p>&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;.<\/p>\n<p>Este artigo \u00e9 baseado na tradu\u00e7\u00e3o autom\u00e1tica do artigo original em ingl\u00eas. Para mais informa\u00e7\u00f5es, consulte o artigo em ingl\u00eas. Voc\u00ea pode nos ajudar. Se voc\u00ea deseja corrigir a tradu\u00e7\u00e3o, envie-a para: translations@nuclear-power.com ou preencha o formul\u00e1rio de tradu\u00e7\u00e3o on-line. Agradecemos sua ajuda, atualizaremos a tradu\u00e7\u00e3o o mais r\u00e1pido poss\u00edvel. Obrigado.<\/p>\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>Um fotoc\u00e1todo converte f\u00f3tons em el\u00e9trons atrav\u00e9s do efeito fotoel\u00e9trico.\u00a0No d\u00ednodo, os el\u00e9trons s\u00e3o multiplicados por emiss\u00e3o secund\u00e1ria.\u00a0Dosimetria de Radia\u00e7\u00e3o Aparelho com cristal cintilante, fotomultiplicador e componentes de aquisi\u00e7\u00e3o de dados.\u00a0Fonte: wikipedia.org Licen\u00e7a CC BY-SA 3.0 Os tubos\u00a0fotomultiplicadores (PMTs) s\u00e3o um dispositivo de detec\u00e7\u00e3o de f\u00f3tons que usa o efeito fotoel\u00e9trico combinado com a emiss\u00e3o &#8230; <a title=\"O que \u00e9 fotocatodo e d\u00ednodos no tubo fotomultiplicador &#8211; Defini\u00e7\u00e3o\" class=\"read-more\" href=\"https:\/\/www.radiation-dosimetry.org\/pt-br\/o-que-e-fotocatodo-e-dinodos-no-tubo-fotomultiplicador-definicao\/\" aria-label=\"More on O que \u00e9 fotocatodo e d\u00ednodos no tubo fotomultiplicador &#8211; Defini\u00e7\u00e3o\">Ler mais<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[51],"tags":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v15.4 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>O que \u00e9 fotocatodo e d\u00ednodos no tubo fotomultiplicador - Defini\u00e7\u00e3o<\/title>\n<meta name=\"description\" content=\"Um fotoc\u00e1todo converte f\u00f3tons em el\u00e9trons atrav\u00e9s do efeito fotoel\u00e9trico. 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