Search results for: D. Bullard

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Bullard</title> <meta name="description" content="Search results for: D. Bullard"> <meta name="keywords" content="D. Bullard"> <meta name="viewport" content="width=device-width, initial-scale=1, minimum-scale=1, maximum-scale=1, user-scalable=no"> <meta charset="utf-8"> <link href="https://cdn.waset.org/favicon.ico" type="image/x-icon" rel="shortcut icon"> <link href="https://cdn.waset.org/static/plugins/bootstrap-4.2.1/css/bootstrap.min.css" rel="stylesheet"> <link href="https://cdn.waset.org/static/plugins/fontawesome/css/all.min.css" rel="stylesheet"> <link href="https://cdn.waset.org/static/css/site.css?v=150220211555" rel="stylesheet"> </head> <body> <header> <div class="container"> <nav class="navbar navbar-expand-lg navbar-light"> <a class="navbar-brand" href="https://waset.org"> <img src="https://cdn.waset.org/static/images/wasetc.png" alt="Open Science Research Excellence" title="Open Science Research Excellence" /> </a> <button class="d-block d-lg-none navbar-toggler ml-auto" type="button" data-toggle="collapse" data-target="#navbarMenu" aria-controls="navbarMenu" aria-expanded="false" aria-label="Toggle navigation"> <span class="navbar-toggler-icon"></span> </button> <div class="w-100"> <div class="d-none d-lg-flex flex-row-reverse"> <form method="get" action="https://waset.org/search" class="form-inline my-2 my-lg-0"> <input class="form-control mr-sm-2" type="search" placeholder="Search Conferences" value="D. 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Bullard"> <input type="submit" class="btn_search" value="Search"> </div> </div> </form> </div> </div> <div class="row mt-3"> <div class="col-sm-3"> <div class="card"> <div class="card-body"><strong>Commenced</strong> in January 2007</div> </div> </div> <div class="col-sm-3"> <div class="card"> <div class="card-body"><strong>Frequency:</strong> Monthly</div> </div> </div> <div class="col-sm-3"> <div class="card"> <div class="card-body"><strong>Edition:</strong> International</div> </div> </div> <div class="col-sm-3"> <div class="card"> <div class="card-body"><strong>Paper Count:</strong> 1</div> </div> </div> </div> <h1 class="mt-3 mb-3 text-center" style="font-size:1.6rem;">Search results for: D. Bullard</h1> <div class="card paper-listing mb-3 mt-3"> <h5 class="card-header" style="font-size:.9rem"><span class="badge badge-info">1</span> Inverted Geometry Ceramic Insulators in High Voltage Direct Current Electron Guns for Accelerators</h5> <div class="card-body"> <p class="card-text"><strong>Authors:</strong> <a href="https://publications.waset.org/abstracts/search?q=C.%20Hernandez-Garcia">C. Hernandez-Garcia</a>, <a href="https://publications.waset.org/abstracts/search?q=P.%20Adderley"> P. Adderley</a>, <a href="https://publications.waset.org/abstracts/search?q=D.%20Bullard"> D. Bullard</a>, <a href="https://publications.waset.org/abstracts/search?q=J.%20Grames"> J. Grames</a>, <a href="https://publications.waset.org/abstracts/search?q=M.%20A.%20Mamun"> M. A. Mamun</a>, <a href="https://publications.waset.org/abstracts/search?q=G.%20Palacios-Serrano"> G. Palacios-Serrano</a>, <a href="https://publications.waset.org/abstracts/search?q=M.%20Poelker"> M. Poelker</a>, <a href="https://publications.waset.org/abstracts/search?q=M.%20Stutzman"> M. Stutzman</a>, <a href="https://publications.waset.org/abstracts/search?q=R.%20Suleiman"> R. Suleiman</a>, <a href="https://publications.waset.org/abstracts/search?q=Y.%20Wang"> Y. Wang</a>, <a href="https://publications.waset.org/abstracts/search?q="></a>, <a href="https://publications.waset.org/abstracts/search?q=S.%20Zhang">S. Zhang</a> </p> <p class="card-text"><strong>Abstract:</strong></p> High-energy nuclear physics experiments performed at the Jefferson Lab (JLab) Continuous Electron Beam Accelerator Facility require a beam of spin-polarized ps-long electron bunches. The electron beam is generated when a circularly polarized laser beam illuminates a GaAs semiconductor photocathode biased at hundreds of kV dc inside an ultra-high vacuum chamber. The photocathode is mounted on highly polished stainless steel electrodes electrically isolated by means of a conical-shape ceramic insulator that extends into the vacuum chamber, serving as the cathode electrode support structure. The assembly is known as a dc photogun, which has to simultaneously meet the following criteria: high voltage to manage space charge forces within the electron bunch, ultra-high vacuum conditions to preserve the photocathode quantum efficiency, no field emission to prevent gas load when field emitted electrons impact the vacuum chamber, and finally no voltage breakdown for robust operation. Over the past decade, JLab has tested and implemented the use of inverted geometry ceramic insulators connected to commercial high voltage cables to operate a photogun at 200kV dc with a 10 cm long insulator, and a larger version at 300kV dc with 20 cm long insulator. Plans to develop a third photogun operating at 400kV dc to meet the stringent requirements of the proposed International Linear Collider are underway at JLab, utilizing even larger inverted insulators. This contribution describes approaches that have been successful in solving challenging problems related to breakdown and field emission, such as triple-point junction screening electrodes, mechanical polishing to achieve mirror-like surface finish and high voltage conditioning procedures with Kr gas to extinguish field emission. <p class="card-text"><strong>Keywords:</strong> <a href="https://publications.waset.org/abstracts/search?q=electron%20guns" title="electron guns">electron guns</a>, <a href="https://publications.waset.org/abstracts/search?q=high%20voltage%20techniques" title=" high voltage techniques"> high voltage techniques</a>, <a href="https://publications.waset.org/abstracts/search?q=insulators" title=" insulators"> insulators</a>, <a href="https://publications.waset.org/abstracts/search?q=vacuum%20insulation" title=" vacuum insulation"> vacuum insulation</a> </p> <a href="https://publications.waset.org/abstracts/115179/inverted-geometry-ceramic-insulators-in-high-voltage-direct-current-electron-guns-for-accelerators" class="btn btn-primary btn-sm">Procedia</a> <a href="https://publications.waset.org/abstracts/115179.pdf" target="_blank" class="btn btn-primary btn-sm">PDF</a> <span class="bg-info text-light px-1 py-1 float-right rounded"> Downloads <span class="badge badge-light">118</span> </span> </div> </div> </div> </main> <footer> <div id="infolinks" class="pt-3 pb-2"> <div class="container"> <div style="background-color:#f5f5f5;" class="p-3"> <div class="row"> <div class="col-md-2"> <ul class="list-unstyled"> About <li><a href="https://waset.org/page/support">About Us</a></li> <li><a href="https://waset.org/page/support#legal-information">Legal</a></li> <li><a target="_blank" rel="nofollow" href="https://publications.waset.org/static/files/WASET-16th-foundational-anniversary.pdf">WASET celebrates its 16th foundational anniversary</a></li> 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Search results for: D. Bullard