Introduction
Adevicethatartificiallygeneratesabeamoffastheavyions(ionswithamassgreaterthanalphaparticles).Itusesacertainformofelectromagneticfieldtoaccelerateheavyions,andcanprovidehigh-energyheavyionbeamswithspeedsuptothousands,tensofthousandsorevencloseto300,000kilometerspersecond(thespeedoflightinavacuum)tobombardnuclei,atoms,Molecules,solidcrystallatticesandevenbiologicalcellsareimportanttoolsforpeopletotransformatomicnucleiand"fundamentalparticles"andunderstandthedeepstructureofmatter.Theyarealsoimportantandextensiveinvariousaspectssuchasindustrialandagriculturalproduction,medicalandhealth,scienceandtechnology,andnationaldefenseconstruction.application.
Foraccelerators,thebiggestdifferencebetweenheavyionsandlightionssuchasprotonsistheircharge-to-massratio(Q/A).HereQisthechargestateoftheion,andAisitsatomicmassnumber.Theaveragekineticenergyobtainedbyeachnucleusisproportionaltothecharge-to-massratio(Q/A)oftheacceleratedion.Butingeneral,thecharge-to-massratioofheavyionsisfarlessthan1(thecharge-to-massratioofprotonsis1),andsomeareevenlessthan0.1.Inordertoimprovetheefficiencyofacceleration,itisnecessarytoincreasethecharge-to-massratio,generallybyincreasingthechargestate.Themethodistouseagasorsolidtargettostripelectronsduringtheparticleaccelerationprocess,andthecharge-to-massratioofthestrippedheavyionscanbeincreased.Furtheraccelerationonthisbasiscaneffectivelyincreasetheaveragekineticenergypernucleus.Thedevelopmentofparticleacceleratorsinmycountryhasmadegreatprogresssincethe1980s.Atpresent,theLanzhouHeavyIonAcceleratorhasthelargestscale,themosttypesofacceleratedparticles,andthehighestenergyinChina.Duringthedevelopmentofthisaccelerator,scientificresearchersandengineeringtechniciansadheredtotheprincipleofcombiningself-reliancewiththeintroductionandassimilationofforeignadvancedtechnology,andovercamenumerousdifficultieswiththeirowningenuityandfightingspirit.ItwasfirstintroducedonDecember12,1988.Theenergyis50MeVpernucleusofcarbonions,thusproclaimingtotheworld:Chinahasbuiltthethirdlarge-scaleheavyioncyclotronafterFrance(beamedin1982)andJapan(beamedin1986).Thedevelopmentandapplicationoftheworldacceleratorisadvanced.ThisachievementisanimportantmilestoneinthedevelopmentofChinaandtheworld'sacceleratortechnology.
Součásti
Podobně jako obecné urychlovače částic mají i těžké urychlovače tři základní součásti:
1.Iontový zdroj pro zajištění potřebného zrychlení těžkých iontů.
2.Vacuumaccelerationsystem,avacuumchamberequippedwithanaccelerationstructure,suchasanaccelerationtube,anaccelerationcavity,etc.,isusedtoapplyacertainformofaccelerationelectricfieldtotheparticles,andtheparticlesarenotscatteredbyairmolecules.Accelerateundertheconditions.
3.Guidanceandfocussystem,includingelectromagneticlens,dominantmagneticfield,etc.Acertainformofelectromagneticfieldisusedtoguideandconstraintheacceleratedparticlebeam,sothatitwillbeacceleratedbytheelectricfieldalongapredeterminedtrajectory.Mostacceleratorsarealsoequippedwithabeamtransportsystemcomposedofanumberofbendingmagnetsandelectromagneticquadrupolelenses,whichareusedbetweenthesourceandtheaccelerator,betweentheacceleratorandthetarget,orwhenmultipleacceleratorsworkinseries.Transporttherequiredparticlebeambetween.Inaddition,inordertoensurethestableoperationoftheaccelerator,thereareusuallyelectromagneticfieldstabilizationequipment,beamcurrentdiagnosisandmonitoringequipment,andvariouspowersupplyandoperationequipment.
Princip práce
Zařízení, které poskytuje určitou energii a určitou intenzitu svazku těžkých paprsků (A>4ion). uchasprotonsjejich poměr náboje k hmotnosti (Q/A), kdeQje stav nabití iontu aAje číslo atomové hmotnosti. Obecně platí, že poměr náboje k hmotnosti těžkých iontů je menší než 1 (poměr náboje k hmotnosti protonů = 1). Ese používá místo kinetické energie částicE.
En=E/A,
Pro lineární urychlovačJinými slovy, jednojaderná energieVkterá odebírá paprsek jako urychlovací napětí. U kruhových urychlovačů, kdekje úměrné (Bρ)2,(Bρ)je z iontu, aby bylo dosaženo tuhosti magnetu. stejná jednojaderná energie jako protony, musíte buď zvětšit velikost magnetického pole nebo oběhového urychlovače ,nebozvýšiturychlovacínapětí.To výrazně zvýší náklady na urychlovač a v budoucnuDenní provozní náklady systému jsou poměrně drahé.Za účelem snížení nákladů je lepší zvýšit hodnotu (Q/A).
Plán vylepšení
V těžkém akcelerátoru existují dva způsoby, jak zlepšit poměr nabití k hmotnosti Q/A.
(1)Increasethechargestateoftheheavyionsource.Anidealheavyionsourceshouldbeabletoprovideabeamofdifferentionswithhighintensity,longlife,andhighchargestates.Generally,electronsareusedtobombardatomsandionsintheplasma,orafastionstrippingmethodcanbeusedtoobtainahighchargestateionflow.Thefluxdensityoftheelectronbombardmentsourceisverydemanding.TheheavyionsourceusedintheheavyionacceleratorisaPIGsourceandadualplasmasource.ThefollowingtableshowsthechargestatedistributionofseveraltypicalheavyioncurrentsderivedfromthePIGheavyionsource.
(2)Strippingtheouterelectronsofions(thatis,thestrippingofatoms).Commonlyusedstrippersaresolid(suchascarbonfilm)andgas.Theaveragechargestateandthedistributionofthechargestateoftheionafterstrippingtheouterlayerofelectronsaremainlydeterminedbytheincidentenergyoftheparticle.Generallyspeaking,thehighertheenergy,theaveragecharge.Thehigherthestate.Thestrippingefficiencyofthesolidstripperishigherthanthatofthegasstripper,buttheangulardispersionandenergydispersionoftheionsafterthestrippingarelarger.
Thesetwowaysofimproving(Q/A)arenowwidelyusedinheavyionaccelerators,especiallythelatter.Becausetheaveragechargestateafterstrippingisdeterminedbytheincidentenergy,heavyionacceleratorsgenerallyadoptacombinationmethod,thatis,twoormoreacceleratorsareconnectedinserieswithastripperinthemiddle.Theformeracceleratoriscalledtheinjector,andthelatteracceleratoristhemainaccelerator.Theheavyionsourceisinstalledintheimplanter,ortheheavyionsareinjectedintotheimplanterexternally.Aftertheionsareacceleratedbytheimplanter,theyreachacertainenergy,andtheionsarestrippedintohigh-chargedheavyionsthroughthestripper.Then,itentersthemainacceleratortoaccelerateandobtainheavyionswithhigherextractionenergy.
Electrostaticaccelerator
Amongallkindsofheavyionaccelerators,theelectrostaticacceleratorischaracterizedbydirectcurrentoperation,whichcanprovidevariousheavyionbeamswithsmallspotsandhighenergyaccuracy.
Thelinearacceleratorbeamintensityislarge,andtheparticletypesarerarelylimited.Therefore,thefirstall-ionacceleratorthatcanacceleratetheionsofallelementsontheperiodictableisalinearaccelerator.Thistypeofacceleratorisalsoahigh-energyheavyion.Themainacceleratorintheinstallationisanidealinjectorforsynchrotron.However,ionscanonlybeacceleratedonceintheaccelerationstructureoftheaccelerator,andcannotbeacceleratedrepeatedly,andtheelectricalefficiencyislow.Manylaboratoriesareworkingonmoreeffectivelinearacceleratorresearch.Intermsofhigh-frequencypower,acyclotronisveryeconomical,becauseionsonlyneedtorepeatedlypassthroughthesameaccelerationstructuretocontinuouslyincreasetheirenergy,anditsmaximumcostisdeterminedbythesizeofthemagnet.Whentheionenergyisrequiredtobehigh,andthetypeandenergyarevariable,themagneticfieldchangecausedbytheincreaseoftherelativisticmassrequiresaverysophisticatedmagneticfieldshapingtechnology.
Synchronizersaremoreeconomicalintermsofhighfrequencyandmagnetconstruction.Itisanidealacceleratorforobtaininghigh-energyheavyions.
Superconductingacceleratorsareusedasheavyionaccelerators.Becauseoftheirgreateconomicandtechnicaladvantages,theyhavereceivedextensiveattention.Itcangenerateahighacceleratingelectricfieldataverylowmicrowavepower,orahighconfinementmagneticfieldataverylowexcitationpower.Thesewillreducethesizeoftheaccelerator,reducepowerconsumptionandoperatingcosts,anditisapromisingheavyionaccelerator.
Examples
Sector-focusedcyclotron
Mostofthenewandrebuiltheavyionacceleratorsintheworldareisochronouscyclotrons(ie,sector-focusedcyclotrons).Thesecondisthetandemelectrostaticaccelerator.Inordertoobtainhigherenergy,manynewlybuiltdevicesusetwoormoreacceleratorsconnectedinseries.Toformaheavyionacceleratorsystem,somearetandemelectrostaticacceleratorsinjectedintoacyclotronorlinearaccelerator,andothersaretwocyclotronsinseries.
Inordertotransmitthebeamfromtheinjectortothemainaccelerator,abeamtransportsystemisneededtochangetheshapeofthebeamfromtheinjectortomeetthebeamrequirementsofthemainaccelerator.Inaddition,inordertoreducetheionlosscausedbythechargeexchange,theacceleratorandthebeamtransportsystemrequireahighdegreeofstraightness,generallyaround1×10-7Torr.Thereshouldbeachargeanalysisdeviceonthetransmissionline.Thestructureoftheheavyionacceleratordeterminesthatitsdebuggingandoperationaremorecomplicated.Generally,anautomaticcontrolsystemshouldbeequippedtocontrolthedebuggingandoperation.Ofcourse,thebeamdiagnosticequipmentintheacceleratorandonthetransmissionlineisindispensable.Less.
LanzhouHeavyIonAccelerator
TheLanzhouNegativeIonResearchFacility,alsoknownastheLanzhouHeavyIonAccelerator,isthelargestheavyionresearchfacilityinChinawiththehighestenergy.Therearecurrently8similarmedium-energyheavy-ionacceleratorsintheworld,andHIRFListhefourthintheorderofcompletiontime.France,Japan,andmycountryalluselarge-scaleseparationfancyclotronsastheirmainaccelerators.Sincethe1960s,withthedevelopmentofheavyionaccelerators,nuclearphysicshasopenedupanewandvigorousfield-heavyionphysics.Inotherdisciplines,suchasatomicphysics,materialsscience,lifesciences,newenergyresearch,astrophysicsandotherfields,heavyionbeamshavealsoshownincreasinglyimportantapplicationprospectsandhaveformedimportantinterdisciplinarysubjects.Inorderformycountrytooccupyaplaceinthisfrontierfield,theStateInvestmentandInstituteofNearMaterialswereresponsibleforthedesignandconstruction.In1988,theLanzhouHeavyIonAccelerator(HIRFL)wasbuilt.Itsmaintechnicalindicatorsreachedtheinternationaladvancedlevelatthattime.SpecialPrizeforProgress,wontheFirstPrizeofNationalScienceandTechnologyProgressin1992.TheLanzhouHeavyIonAcceleratorNationalLaboratorywasestablishedin1991.Itspositioningistofocusonthebasicandappliedresearchofheavyionphysics,developparticleacceleratorsandexperimentaltechnologyaccordingly,andbeacomprehensivescientificresearchbaseopentodomesticandforeign.Inthe1990s,aninternationallyadvancedradioactivebeamstreamline(RIBLL)anda14.5GHzhigh-chargestateECRionsourcewerebuiltonHIRFL,bothofwhichwonthefirstprizeofscientificandtechnologicalprogressoftheChineseAcademyofSciences.Theresearchintheinternationalfrontierfieldsofionizedstateatomicphysicshascreatedadvancedexperimentalconditions.LanzhouHeavyIonAcceleratorCoolingandStorageRing(HIRFL-CSR)-isthecountry’slargestscientificprojectduringtheNinthFive-YearPlan.LanzhouNationalLaboratoryofHeavyIonAcceleratorhasdevelopedintooneoftheheavyionphysicsresearchcentersenjoyingahighreputationintheworld.
Medicalheavyionaccelerator
China’sfirstself-developedmedicalheavyionacceleratorwassuccessfullylaunched.Thismeansthatheavyionradiotherapyfortumorpatientswillnolongerrelyonforeigntechnologyandequipment.
ThismedicalheavyionacceleratorislocatedinWuweiCity,GansuProvince,anditsdevelopmentbeganinMay2012.Atpresent,400MeVpernucleuscarbonionbeamaccelerationandnonlinearresonanceslowextractionhavebeenachieved,whichhasreachedthedesignindex.Thedevicecanbeusedforheavyionradiotherapyfortumorpatients,especiallyfortumortypesthataredifficult,unsuitableforsurgery,andpronetorelapseusingothertreatmentmethods.
Previously,onlyShanghaiFudanUniversityCancerHospitalhadasetoffullyimportedmedicalheavyionacceleratorequipmentinChina.Independentresearchanddevelopmentisthefirstcase.
RelevantresearchersfromtheInstituteofNearPhysicsoftheChineseAcademyofSciencessaidthatthisheavyionacceleratoristheresultoftheaccumulationandinheritanceoftheinstitute’snearly60yearsofscientificresearchexperience.Aftertheheavyionacceleratorissuccessfullyreleased,youcanapplyfortheStateFoodandDrugAdministrationtotest.Afterthetestmeetsthestandard,clinicaltrialswillbecarriedout,andthetestindicatorscanbeofficiallyusedtoreceivetreatmentforcancerpatients.
Itisunderstoodthatintermsoftumortreatment,theenergydepositionandaccuracyofheavyionsarebetterthanprotonsthathavebeenusedformanyyears,andthetechnologyisrelativelymature,whichhasobviousadvantagesinphysicsandbiology.