[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"detail-sidebar-cat-0-en-105":3,"doc-seo-153995-105":59,"doc-detail-153995-en":130},{"code":4,"msg":5,"data":6},0,"success",[7,13,18,23,28,33,38,43,48,51,55],{"id":8,"doc_module":4,"doc_module_name":9,"category_name":10,"show_sort_weight":11,"slug":12},1,"Document","Story & Novel",90,"story-novel",{"id":14,"doc_module":4,"doc_module_name":9,"category_name":15,"show_sort_weight":16,"slug":17},2,"Literature",80,"literature",{"id":19,"doc_module":4,"doc_module_name":9,"category_name":20,"show_sort_weight":21,"slug":22},4,"Exam",70,"exam",{"id":24,"doc_module":4,"doc_module_name":9,"category_name":25,"show_sort_weight":26,"slug":27},5,"Comic",60,"comic",{"id":29,"doc_module":4,"doc_module_name":9,"category_name":30,"show_sort_weight":31,"slug":32},6,"Technology",50,"technology",{"id":34,"doc_module":4,"doc_module_name":9,"category_name":35,"show_sort_weight":36,"slug":37},7,"Healthcare",40,"healthcare",{"id":39,"doc_module":4,"doc_module_name":9,"category_name":40,"show_sort_weight":41,"slug":42},8,"Research & Report",30,"research-report",{"id":44,"doc_module":4,"doc_module_name":9,"category_name":45,"show_sort_weight":46,"slug":47},9,"Religion & Spirituality",20,"religion-spirituality",{"id":46,"doc_module":4,"doc_module_name":9,"category_name":49,"show_sort_weight":46,"slug":50},"World Cup","world-cup",{"id":52,"doc_module":4,"doc_module_name":9,"category_name":53,"show_sort_weight":52,"slug":54},10,"Lifestyle","lifestyle",{"id":56,"doc_module":4,"doc_module_name":9,"category_name":57,"show_sort_weight":24,"slug":58},19,"General","general",{"code":4,"msg":60,"data":61},"ok",{"site_id":62,"language":63,"slug":64,"title":65,"keywords":66,"description":67,"schema_data":68,"social_meta":123,"head_meta":125,"extra_data":127,"updated_unix":129},105,"en","an-investigation-of-beam-driven-alfven-instabilities-in-the-diii-d-tokamak","AN INVESTIGATION OF BEAM DRIVEN ALFVÉN INSTABILITIES IN THE DIII-D TOKAMAK","","Neutral beams are injected into low-field deuterium plasmas in DIII-D to test whether toroidicity-induced Alfvén eigenmodes (TAE) can be destabilized by a beam-driven energetic ion population. When the parallel beam velocity approaches the Alfvén velocity and the volume-averaged beam beta exceeds 2%, localized propagating modes with toroidal mode number n=2–10 emerge. Up to 45% of beam power is lost due to these modes. The TAE instability threshold is at least an order of magnitude higher than earlier theoretical predictions.",{"@graph":69,"@context":122},[70,84,105],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":40,"@type":76,"position":81},"https://docshare.wps.com/document/research-report/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/an-investigation-of-beam-driven-alfven-instabilities-in-the-diii-d-tokamak/153995/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/an-investigation-of-beam-driven-alfven-instabilities-in-the-diii-d-tokamak/153995.png","ImageObject",300,407,{"name":92,"@type":93},"Felix Montgomery","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-10-17","2026-08-28",true,{"@type":102,"interactionType":103,"userInteractionCount":52},"InteractionCounter",{"@type":104},"ViewAction",{"@type":106,"mainEntity":107},"FAQPage",[108,114,118],{"name":109,"@type":110,"acceptedAnswer":111},"What role do alpha particles play in tokamak ignition, according to the text?","Question",{"text":112,"@type":113},"For ignition, most fusion-produced alpha particles must thermalize in the plasma. If energetic alphas drive collective instabilities leading to anomalous losses, ignition will not occur.","Answer",{"name":115,"@type":110,"acceptedAnswer":116},"How do the neutral beam experiments simulate alpha physics in a reactor?",{"text":117,"@type":113},"Neutral beam injection creates an energetic ion population analogous to reactor alphas, with an anisotropic velocity distribution in the beam case. Aside from this anisotropy, the beam ions are described as effectively simulating alpha physics in a reactor-relevant energy regime.",{"name":119,"@type":110,"acceptedAnswer":120},"Under what conditions were TAE-related modes observed and what was their impact?",{"text":121,"@type":113},"Localized propagating modes with n=2–10 were observed when the parallel beam velocity approached the Alfvén velocity and the volume-averaged beam beta exceeded 2%. These modes caused losses of up to 45% of the beam power.","https://schema.org",{"og:url":83,"og:type":124,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":126,"canonical":83},"index,follow",{"doc_id":128,"site_id":62},153995,1787884733,{"code":4,"msg":5,"data":131},{"doc_id":128,"user_id":132,"nickname":92,"user_avatar":133,"doc_module":4,"category_id":39,"category_name":40,"doc_title":65,"doc_description":67,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":52,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":139,"language":140,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":141,"faqs":142,"seo_title":143,"seo_description":67,"update_tm":129,"read_time":144,"preview_page_count":4},549768064778,"https://ap-avatar.wpscdn.com/davatar_6f874abed73319feea01a86fa6f0fab8","# AN INVESTIGATION OF BEAM DRIVENALFVÉN INSTABILITIES IN THE DIII-D TOKAMAK\n\nW.W.HEIDBRINK*,E.J.STRAIT,E.DOYLE**,  \nG.SAGER***,R.T.SNIDERGeneral Atomics,San Diego,California,United States of America  \n## 1.INTRODUCTION\n\nTo sustain ignition in a tokamak reactor,most of thealpha particles produced in D-T fusion reactions mustthermalize in the plasma.If the energetic alpha popula-tion drives collective instabilities that result in anomalouslosses of the alphas,the reactor will not ignite.There-fore,it is desirable,before construction of a reactor,to assess the likelihood that alphas will drive collectiveinstabilities.In this paper,we describe experiments inwhich neutral beam injection is employed to create anenergetic ion population that simulates the alphas.Theprincipal difference between a beam population and analpha population in a reactor is that the distribution ofbeam ions is anisotropic in velocity space (the alphadistribution is isotropic).In other regards,the beamion distribution effectively simulates alpha physics ina 20kV reactor such as the International ThermonuclearExperimental Reactor(ITER)(Table I).Our experimentsare also relevant to neutral beam current drive with~1 MeV ions in future devices such as ITER [1].If Alfvén instabilities cause appreciable anomalouslosses or pitch angle scattering of the circulating beamions,the current drive efficiency will be reduced anda high plasma current will not be sustained.Finally,destabilization of Alfvén waves by energetic ions is offundamental interest,since super-Alfvénic ion popula-tions are common in space [2].  \nPermanent addresses:  \n*Physics Department,University of California,Irvine,CA,USA.  \n**Electrical Engineering Depatment,University of California,Los Angeles,CA,USA.  \n***Nuclear Engineering Department,University of Illinois,Urbana,IL,USA.  \nABSTRACT.Neutral beams were injected into low field (B=0.7-1.0 T)deuterium plasmas in an attempt todestabilize toroidicity induced Alfvén eigenmodes (TAE modes).When the parallel beam velocity approached theAlfvén velocity and the volume averaged beam beta exceeded 2%,localized,propagating modes with n =2-10were observed.As much as 45%of the beam power was lost as a result of the modes.The threshold for TAEinstability is at least one order of magnitude higher than that predicted by Fu and VanDam(Phys.Fluids B1(1989)1949).  \nDestabilization of shear Alfvén waves by circulatingfast ions has been explored theoretically by manyauthors.In a homogeneous plasma,Alfvén waves arenormal modes of the plasma that are weakly Landaudamped by electrons.The waves are analogous totransverse waves on a string and propagate with aphase velocity w/k₁=VA=B/√4πn;m;,where the'tension’of the string is provided by the magneticfield B and the 'inertia'of the string is due to the ionmass density n;m;.For instability,the waves must gainenough energy from the fast ion distribution to overcomeelectron damping.Fast ion distributions that are non-monotonic in velocity space)can beunstable through inverse Landau damping [3].Althoughthese velocity space instabilities might be observedtransiently,steady state slowing down distributionsgenerally are monotonic in velocity space and thusconfiguration space instabilities are of greater concern.  \nTABLE I.COMPARISON OF BEAM IONS INDIII-D AND ALPHAS IN ITER  \n\n| Ratio   | Description   | DIII-D   |  ITER [1]   |\n| --- | --- | --- | --- |\n| Pr:P₁Pe   | Gyroradii of fast ions,  \u003Cbr>thermal ions and electrons   | 6:1:0.16     |  10:1:0.16   |\n| Ve:V₁:v;   | Velocities of electrons,  \u003Cbr>fast ions and thermal ions   | 10:1:0.16    |   6:1:0.26   |\n| βr(O)   | Central fast ion pressure to  \u003Cbr>magnetic field pressure   | ≤15%   | 2-4%   |\n| v₁IVA   | Fast ion velocity to  \u003Cbr>Alfvén velocity   | ≤1.4   | 1.9   |\n\nBecause of the curvature drift in toroidal geometry,circulating fast ions can resonate with Alfvén waveson different mode rational surfaces [4].This providesa mechanism to tap the free energy in the fast ionpres","cbCaisJD9PyGm7Bq","https://ap.wps.com/l/cbCaisJD9PyGm7Bq","pdf",1444339,14,"English","# 1. Introduction","[{\"question\":\"What role do alpha particles play in tokamak ignition, according to the text?\",\"answer\":\"For ignition, most fusion-produced alpha particles must thermalize in the plasma. If energetic alphas drive collective instabilities leading to anomalous losses, ignition will not occur.\"},{\"question\":\"How do the neutral beam experiments simulate alpha physics in a reactor?\",\"answer\":\"Neutral beam injection creates an energetic ion population analogous to reactor alphas, with an anisotropic velocity distribution in the beam case. Aside from this anisotropy, the beam ions are described as effectively simulating alpha physics in a reactor-relevant energy regime.\"},{\"question\":\"Under what conditions were TAE-related modes observed and what was their impact?\",\"answer\":\"Localized propagating modes with n=2–10 were observed when the parallel beam velocity approached the Alfvén velocity and the volume-averaged beam beta exceeded 2%. These modes caused losses of up to 45% of the beam power.\"}]","AN INVESTIGATION OF BEAM DRIVEN ALFVÉN INSTABILITIES IN THE DIII-D TOKAMAK | PDF",35]