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.
Компоненти
Подобно на общите ускорители на частици, ускорителите на тежки йони имат три основни компонента:
1.Източник на йони за осигуряване на необходимото ускоряване на тежки йони.
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.
Принцип на работа
Устройство, което осигурява определена енергия и определен интензитет на лъч от тежки йони (A>4ion). Принципът на ускоряване и структурата на ускорителя на тежки йони са основно същите като на протоновия ускорител. Въпреки това, за ускорителите, най-голямата разлика между тежките йони и светлини като протоните е тяхното съотношение на заряд към маса (Q/A), къдетоQе зарядното състояние на йона, аAе неговото атомно масово число. Обикновено съотношението на заряда към масата на тежките йони е много по-малко от 1 (съотношението на заряда към масата на протоните=1). За удобство на дискусията, това единично ядро е енергия Eни се използва вместо кожната енергия на частицатаE.
En=E/A,
За линеен ускорител С други думи, едноядрената енергияVкоято изтегля лъчите от ускоряващото напрежение. За кръговите ускорители, къдетоkе пропорционално на (Bρ)2, (Bρ)е магнитната твърдост. Може да се види от горната формула, която искате да получите тежък йон лъч със същата единична ядрена енергия като протони, трябва или да увеличите размера на магнитното поле, или кръговия ускорител ,или да увеличи ускоряващото напрежение. Това значително ще увеличи цената на ускорителя и в бъдеще ежедневните експлоатационни разходи на системата са наистина доста скъпи. За да се намалят разходите, е по-добре да се увеличи (Q/A) стойността.
План за подобрение
В тежкия йонен ускорител има два начина за подобряване на съотношението заряд към маса 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.