new developments in high voltage technology.pdf

TRUMP:NEWDEVELOPMENTSINHIGHVOLTAGETECHNOLOGYNEWDEVELOP1vNTSINHIGHVOLTAGETECHNOLOGYJohnG.Trump MabssachusettsInstituteofTechnology Cambridge,MAssachusettsandHighVoltageEngineeringCorporation Burlington,MbssachusettsSUvRYTheelectrostaticandelectromagnetic straight-lineacceleratorsoriginatedbyRobert VandeGraafffornuclearsciencehave,forvery heavyions,movedtowardtheGeVlevelthrough advancesinhighvoltagetechnologyappliedtothe multi-stage(tandem)accelerationofmulti- strippedions.Anaccountisgivenofthe discreetstepsinthisexponentialprogresswhich dependsbasicallyonthemaximumreliablevoltage ofoneoraseriesofterminals.Recentstudies oncompressedgasinsulationandonthecontrolof electricalprocesseswithinlonghigh-gradient accelerationtubesaredescribed.Theseindicate thepossibilityoffurthersubstantialincreases interminalandcolumngradientsapplicablelater toexistingacceleratorsandtoenlargedgoalsfor newones.INTRODUCTIONInRutherford'sretiringpresidentialaddress totheRoyalSocietyin1921heexpressedhislong felt hopeforamorepotentsourceofenergetic heavyparticles.Thatneedforhigherparticle energyandbeamintensityfornuclearstructure researchandhighenergyphysicshassincestead- ilyintensified.Today,particleaccelerator technologyfindsitselfdrivenbytheextra- ordinaryaccomplishmentsofnuclearscienceduring thepast4decadesbutimpededbytherapidly growingcostsoflargesystems.Itnowfacesthe economicnecessityofattaininghigherparticle energiesbyvastlyimprovedaccelerationmethods andbysubstantialincreasesintheoperating gradientandpowerdensityoftheaccelerating system.ItisthusappropriatethatIdiscussthis afternoonseveralnewlinesofthoughtand developmentsinhighvoltagetechnologywhichcan againupgradeourabilitytoproducemoreenerget- icparticlesinincreasingnumbersandinvariety coveringtheentireatomictable,yetaccurately selectableinenergy,mass,andchargestate.ROEJEISONVANDEGRAAFFIintendtocenterthisdiscussionaroundthe VandeGraaffaccelerator,meaningtherebythe systemofelectrostaticbeltgeneratorandtube whichRobertVandeGraafforiginatedsome36 yearsago,andwhichintheseinterveningyears hasattainedinternationalrecognitionastheprecisionsourceofnuclearprojectilesfornu- clearscience.Thisfamiliarelectrostatichigh voltagesourceisnowsupplementedbytheelectro- magneticconstant-potentialsourceknownas Insulated-Core-Transformer.Thisisthefirst embodimentofanewelectromagneticmethodof powergenerationandtransformationoriginatedand encouragedbyVandeGreaffduringthelastdecade ofhislifetomeettheneedwhichheforsawfor fargreaterincreasesinoutputparticleenergy andpower.Indeedthesenewprinciplesandtech- niquesof managingelectricandmagneticfields areagainsodirectandpowerfulthat theycanbe appliednotonlytotheproductionofintensehigh energyparticlesourcesbutalso tothefuture energyconversionequipmentsofhighvoltageelec- tricpowersystems,particularlythoseinvolving thehighervoltagesand thelargerunitsofpower.Manyofthemembersofthisconferenceandoftheworldofphysicalscienceweresaddenedbythe deathofRobertVandeGreaffonJanuary16of thisyear.I,whohadtheprivilegeofhisteach- ingandinspirationandencouragementandwarm friendshipformanyyears,dedicatethispresenta- tiontoRobertJemisonVandeGraaffwiththe deepestgratitudeandappreciation.THEEXPONENTIALPROGRESSOFELECTROSTATICACCELER- ATORSPowerdensityofelectricalequipmentrefers totheoutputpowerperunitweightorunitvolume. Theelectricalpowersystemsofourcountryhave beenmovingtheirpowercapacityandpowerdensity upwardformorethaneightyyearswithimportant accompanyingadvantagesofefficiencyandreli- ability.Inparticleacceleratortechnologythe correspondingincreasesinparticleenergyand powerdensityhavebeenequallyimpressiveand havecomethroughasuccessionofdefinablesteps.Thefirstgreatadvanceinpowercompactness camebytheexploitationofthesuperiorinsulat- ingpropertiesofcompressedgases.Throughthe workofPaschen,Natterer,Townsend,andmany othersthebeneficialinfluenceofhighergas pressuresandofelectronegativegasmolecules werealreadyappreciatedatthetimeofVande Graaff'sdramaticinnovationin1930.Thoughthe earliestVandeGraaffswereconvenientlyinsul- atedinatmosphericair,thetrendtowardcom- pressedgaseswasimmediateandirreversible.1113IEEETRANSACTIONSONNUCLEARSCIENCE,JUNE1967Theprinciplewaswellunderstoodthatanincrease bythefactorkinthedielectricstrengthofthe mediumsurroundingahighvoltageelectrostatic systempermitsak-foldreductionofallits lineardimensions.Inthebeltgeneratorthis superiordielectricalsoincreasesthepermissible electricfieldarisingfromtheconveyorbelt charge.Inthelimit,suchabetterdielectric resultsinak3reductioninthevolumeofthe apparatusforthesamevoltageandgenerator power.Thus,longbeforethelargeair-insulated electrostaticacceleratoratM.I.T.completedits twodecadesofresearchandwastransferredto itspresentsiteattheBostonMuseumofScience, equivalentpressure-insulatedacceleratorshad becomeavailablewhichrequiredlessthan1 thousandththevolumtoconfinetheirelectric fields.Farmoreimportant,ofcourse,wasthe factthatthisincreasingvoltageandpower densitymadepracticaltheattainmentofhigher particleenergy.Thenextmajorstepinincreasin。