Lub hauv paus ntsiab lus paub txog "ntau dua yog muaj zog dua" tau tsim los ntev ntev hauv ntau lub zej zog, suav nrog kev tshawb fawb thiab thev naus laus zis. Txawm li cas los xij, hauv qhov tseeb niaj hnub no, kev siv tswv yim ntawm cov lus hais tias "me me, tab sis muaj zog" tau dhau los ua ntau dua. Qhov no yog manifested ob qho tib si nyob rau hauv computers, uas yav tas los coj mus rau ib tug tag nrho chav tsev, tab sis tam sim no haum nyob rau hauv lub xib teg ntawm tus me nyuam, thiab nyob rau hauv them nqi particle accelerators. Yog lawm, nco ntsoov lub Loj Hadron Collider (LHC), uas nws qhov loj me (26 m nyob rau hauv ntev) tau qhia hauv nws lub npe? Yog li, qhov no yog ib qho ntawm yav dhau los raws li cov kws tshawb fawb los ntawm DESY, uas tau tsim cov qauv me me ntawm cov accelerator, uas tsis yog qhov qis dua hauv kev ua tau zoo rau nws cov thawj coj loj. Ntxiv mus, lub mini accelerator txawm teem ib lub ntiaj teb no cov ntaub ntawv tshiab ntawm terahertz accelerators, ob npaug rau lub zog ntawm lub embedded electrons. Tus me me accelerator tau tsim li cas, cov ntsiab lus tseem ceeb ntawm nws txoj haujlwm yog dab tsi, thiab qhov kev sim ua tau zoo li cas? Daim ntawv tshaj tawm ntawm pab pawg tshawb fawb yuav pab peb paub txog qhov no. Mus.
Kev tshawb fawb hauv paus
Raws li Dongfang Zhang thiab nws cov npoj yaig ntawm DESY (German Electron Synchrotron), uas tsim lub tshuab hluav taws xob me me, cov khoom siv hluav taws xob ultrafast ua lub luag haujlwm tseem ceeb hauv lub neej niaj hnub no. Ntau yam ntawm lawv tshwm sim hauv cov tshuaj, kev tsim kho hluav taws xob thiab kev tshawb fawb tshawb fawb. Qhov teeb meem loj tshaj plaws nrog tam sim no linear accelerators siv RF oscillators yog lawv cov nqi siab, complex infrastructure, thiab impressive zog noj. Thiab cov kev tsis txaus siab no txwv tsis pub muaj cov thev naus laus zis no rau ntau tus neeg siv.
Cov teeb meem pom tseeb no yog qhov kev txhawb siab zoo los tsim cov khoom siv uas nws qhov loj thiab lub zog siv yuav tsis ua rau ntshai heev.
Ntawm cov txheeb ze tshiab hauv kev lag luam no yog terahertz accelerators, uas muaj ntau yam "cov txiaj ntsig":
- Nws cia siab tias tsis ntev thiab luv pulses ntawm terahertz hluav taws xob yuav ua rau muaj kev nce qib. kev tawg *, tshwm sim los ntawm daim teb, uas yuav ua rau kom acceleration gradients;
Hluav taws xob tawg * - qhov nce ntxiv ntawm lub zog tam sim no thaum muaj qhov hluav taws xob siab tshaj qhov tseem ceeb tau siv.
- lub xub ntiag ntawm txoj kev ua tau zoo rau kev tsim cov hluav taws xob terahertz siab tso cai rau kev sib koom ua ke ntawm electrons thiab excitation fields;
- Cov txheej txheem classic tuaj yeem siv los tsim cov khoom siv zoo li no, tab sis lawv cov nqi, sijhawm ntau lawm thiab qhov loj me yuav raug txo kom tsawg.
Cov kws tshawb fawb ntseeg tias lawv cov millimeter-scale terahertz accelerator yog kev sib haum xeeb ntawm cov pa accelerators uas tam sim no muaj thiab micro-accelerators uas tab tom tsim, tab sis muaj ntau yam tsis zoo vim lawv qhov me me heev.
Cov kws tshawb fawb tsis lees paub tias terahertz acceleration technology tau nyob hauv kev txhim kho rau qee lub sijhawm. Txawm li cas los xij, hauv lawv txoj kev xav, tseem muaj ntau yam hauv cheeb tsam no uas tsis tau kawm, sim lossis siv.
Hauv lawv txoj haujlwm, uas peb tab tom xav txog niaj hnub no, cov kws tshawb fawb pom tau tias muaj peev xwm ntawm STEAM (segmented terahertz electron accelerator thiab manipulator) - segmented terahertz electron accelerator thiab manipulator. STEAM ua rau nws muaj peev xwm txo tau qhov ntev ntawm lub teeb hluav taws xob mus rau lub sijhawm ncua picosecond, yog li muab femtosecond tswj nyob rau theem acceleration.
Nws muaj peev xwm ua tiav qhov nrawm ntawm 200 MV / m (MV - megavolt), uas ua rau cov ntaub ntawv terahertz acceleration ntawm> 70 keV (kiloelectronvolt) los ntawm cov kab hluav taws xob embedded nrog lub zog ntawm 55 keV. Nyob rau hauv txoj kev no, ceev electrons mus txog 125 keV tau txais.
Tus qauv tsim thiab kev siv
Duab No. 1: daim duab ntawm lub cuab yeej nyob rau hauv kev kawm.
Duab No. 1-2: a - daim duab ntawm tus tsim 5-txheej segmented qauv, b - piv ntawm kev xam acceleration thiab kev taw qhia ntawm electron propagation.
Cov kab hluav taws xob hluav taws xob (55 keV) yog tsim los ntawm phom electron * thiab tau nkag mus rau hauv terahertz STEAM-buncher (beam compressor), tom qab ntawd lawv nkag mus rau hauv STEAM-linac (linear accelerator *).
Electron phom * - ib qho khoom siv rau kev tsim cov kab hluav taws xob ntawm qhov xav tau kev teeb tsa thiab lub zog.
Linear accelerator * - ib tug accelerator nyob rau hauv uas them cov khoom xa mus los ntawm cov qauv ib zaug xwb, uas txawv ib tug linear accelerator los ntawm ib tug cyclic (piv txwv li, LHC).
Ob lub tshuab STEAM tau txais terahertz pulses los ntawm ib qho ze-infrared (NIR) laser, uas tseem tua hluav taws xob phom electron's photocathode, uas ua rau hauv synchronization ntawm electrons thiab accelerating teb. Ultraviolet pulses rau photoemission ntawm photocathode yog tsim los ntawm ob theem ua tiav GVG* Qhov tseem ceeb wavelength ntawm ze-infrared teeb. Cov txheej txheem no hloov lub 1020 nm laser mem tes ua ntej rau 510 nm thiab tom qab ntawd mus rau 255 nm.
GVG* (optical thib ob harmonic tiam) yog cov txheej txheem ntawm combining photons ntawm tib zaus thaum muaj kev cuam tshuam nrog ib tug nonlinear cov ntaub ntawv, uas ua rau lub tsim ntawm tshiab photons nrog ob lub zog thiab zaus, nrog rau ib nrab ntawm lub wavelength.
Cov seem ntawm NIR laser beam raug muab faib ua 4 kab teeb, uas yog siv los tsim plaub lub voj voog ib zaug terahertz pulses los ntawm kev tsim intra-pulse zaus sib txawv.
Ob lub terahertz pulses yog tom qab ntawd xa mus rau txhua lub tshuab STEAM los ntawm cov qauv sib xyaw ua ke uas coj lub zog terahertz mus rau thaj tsam kev sib cuam tshuam thoob plaws kev taw qhia ntawm electron propagation.
Thaum cov hluav taws xob nkag mus rau txhua lub tshuab STEAM, lawv raug rau cov khoom siv hluav taws xob thiab sib nqus Lorentz rog *.
Lorentz zog * - lub zog uas lub electromagnetic teb ua rau ib tug nqi particle.
Nyob rau hauv cov ntaub ntawv no, hluav taws xob teb yog lub luag hauj lwm rau acceleration thiab deceleration, thiab lub magnetic teb ua rau lateral deflections.
Duab #2
Raws li peb pom hauv cov duab 2 ΠΈ 2b, Hauv txhua lub tshuab STEAM, cov kab hluav taws xob terahertz tau muab faib ua ntu ntu ntawm cov ntawv hlau nyias rau hauv ob peb txheej ntawm cov thickness sib txawv, txhua tus ua raws li lub waveguide, hloov ib feem ntawm tag nrho lub zog mus rau thaj tsam sib cuam tshuam. Kuj tseem muaj cov phaj dielectric hauv txhua txheej los tswj lub sijhawm tuaj txog ntawm terahertz yoj pem hauv ntej * nrog rau pem hauv ntej ntawm electrons.
Wavefront * - qhov chaw uas lub nthwv dej tau mus txog.
Ob chav chav ua haujlwm hauv hom hluav taws xob, uas yog, nyob rau hauv xws li ib txoj kev hluav taws xob thiab tsim kev sib nqus hauv qhov chaw ntawm cov chaw sib cuam tshuam.
Hauv thawj lub cuab yeej, cov khoom siv hluav taws xob yog sijhawm dhau mus xoom hla * terahertz teb, qhov twg lub sij hawm gradients ntawm hluav taws xob teb yog maximized thiab qhov nruab nrab teb yog minimized.
Zero hla * - ib qho chaw uas tsis muaj kev ntxhov siab.
Qhov kev teeb tsa no ua rau tus Tsov tus tw ntawm cov kab hluav taws xob kom nrawm thiab nws lub taub hau kom decelerate, ua rau ballistic longitudinal tsom (2 ΠΈ 2c ib).
Nyob rau hauv lub thib ob ntaus ntawv, lub electron thiab terahertz hluav taws xob yog synchronized kom lub electron beam tsuas yog ib tug tsis zoo voj voog ntawm lub terahertz hluav taws xob teb. Qhov kev teeb tsa no ua rau muaj qhov nrawm nrawm nrawm (2b ΠΈ 2d).
Lub NIR laser zoo ib yam li lub tshuab txias txias Yb: YLF, uas tsim cov pulses kho qhov muag ntawm 1.2 ps ntev thiab 50 mJ zog ntawm lub wavelength ntawm 1020 nm thiab rov ua dua ntawm 10 Hz. Thiab terahertz pulses nrog lub hauv nruab nrab zaus ntawm 0.29 terahertz (lub sij hawm ntawm 3.44 ps) yog tsim los ntawm inclined mem tes pem hauv ntej txoj kev.
Txhawm rau siv lub zog STEAM-buncher (beam compressor) tsuas yog 2 x 50 nJ ntawm terahertz lub zog tau siv, thiab STEAM-linac (linear accelerator) xav tau 2 x 15 mJ.
Qhov txoj kab uas hla ntawm qhov nkag thiab qhov hluav taws xob ntawm ob lub tshuab STEAM yog 120 microns.
Lub beam compressor yog tsim los nrog peb txheej ntawm qhov sib npaug ntawm qhov siab (0 mm), uas yog nruab nrog fused silica daim hlau (Ο΅r = 225) ntawm qhov ntev 4.41 thiab 0.42 mm los tswj lub sijhawm. Qhov sib npaug ntawm qhov siab ntawm cov khaubncaws sab nraud povtseg qhia qhov tseeb tias tsis muaj qhov nrawm (2c ib).
Tab sis nyob rau hauv lub linear accelerator qhov siab twb sib txawv - 0.225, 0.225 thiab 0.250 mm (+ fused quartz daim hlau 0.42 thiab 0.84 mm). Ib qho kev nce hauv qhov siab ntawm txheej piav qhia qhov nce ntawm qhov ceev ntawm electrons thaum lub sij hawm acceleration.
Cov kws tshawb fawb tau sau tseg tias tus lej ntawm cov khaubncaws sab nraud povtseg yog lub luag haujlwm ncaj qha rau kev ua haujlwm ntawm txhua qhov ntawm ob lub cuab yeej. Ua kom tiav cov nqi siab dua, piv txwv li, yuav xav tau ntau cov khaubncaws sab nraud povtseg thiab qhov siab sib txawv los ua kom zoo rau kev sib cuam tshuam.
Cov txiaj ntsig ntawm kev xyaum ua
Ua ntej, cov kws tshawb fawb tau ceeb toom tias nyob rau hauv ib txwm siv xov tooj cua zaus accelerators, cov nyhuv ntawm lub sijhawm ntawm lub embedded electron beam ntawm cov khoom ntawm lub nrawm nrawm yog vim qhov kev hloov pauv hauv hluav taws xob tau ntsib thaum muaj kev cuam tshuam ntawm cov hluav taws xob sib txawv hauv cov nqaj tuaj txog. thaum sib txawv. Yog li, nws tuaj yeem cia siab tias thaj chaw nrog cov gradients siab dua thiab kab teeb nrog ntev ntev yuav ua rau lub zog loj dua. Txhaj kab teeb ntawm lub sijhawm ntev tuaj yeem ua rau muaj txiaj ntsig ntau dua emissions *.
Kev xa tawm * - theem qhov chaw nyob los ntawm ib tug ceev beam ntawm them hais.
Nyob rau hauv cov ntaub ntawv ntawm ib tug terahertz accelerator, lub sij hawm ntawm lub excitation teb yog kwv yees li 200 lub sij hawm luv. Vim li no, nruj * qhov chaw txhawb nqa yuav siab dua 10 npaug.
Lub zog hluav taws xob * - qhov taw qhia ntawm lub teb hluav taws xob, sib npaug ntawm qhov sib npaug ntawm lub zog siv rau qhov chaw nres tsheb ntawm qhov chaw them nqi muab tso rau ntawm qhov taw qhia hauv thaj teb rau qhov loj ntawm qhov nqi no.
Yog li, nyob rau hauv ib tug terahertz accelerator, lub teb gradients paub los ntawm electrons yuav ua tau ntau yam kev txiav txim ntawm magnitude siab tshaj nyob rau hauv ib tug pa ntaus ntawv. Lub sij hawm teev ntawm qhov chaw curvature yog pom tau yuav me me. Nws ua raws los ntawm qhov no hais tias lub sij hawm ntawm cov kab hluav taws xob qhia tau yuav muaj kev cuam tshuam ntau dua.
Cov kws tshawb fawb tau txiav txim siab los sim cov kev xav no hauv kev xyaum. Ua li no, lawv tau qhia cov kab hluav taws xob ntawm lub sijhawm sib txawv, uas tau tswj los ntawm compression siv thawj STEAM ntaus ntawv (STEAM-buncher).
Duab #3
Nyob rau hauv rooj plaub uas lub compressor tsis txuas nrog lub hwj chim, kab hluav taws xob (55 keV) nrog tus nqi ntawm βΌ1 fC (femtocoulomb) dhau li ntawm 300 hli los ntawm rab phom electron mus rau cov khoom siv accelerator linear (STEAM-linac). Cov hluav taws xob no tuaj yeem nthuav dav nyob rau hauv qhov cuam tshuam ntawm qhov chaw them nqi mus txog lub sijhawm ntau dua 1000 fs (femtoseconds).
Nyob rau lub sijhawm no, cov kab hluav taws xob nyob hauv kwv yees li 60% ntawm ib nrab-yoj ntawm qhov nrawm nrawm nrog qhov zaus ntawm 1,7 ps, ua rau lub zog tom qab nrawm nrawm nrog lub ncov ntawm 115 keV thiab ib nrab-dav ntawm lub zog faib. ntau tshaj 60 keV (3).
Txhawm rau sib piv cov txiaj ntsig no nrog cov kev xav tau, qhov xwm txheej ntawm electron propagation los ntawm linear accelerator tau simulated thaum lub electrons tawm ntawm sync nrog (piv txwv li, tawm ntawm sync nrog) lub sij hawm zoo txhaj tshuaj. Kev suav ntawm qhov xwm txheej no tau pom tias qhov nce ntawm lub zog hluav taws xob yog nyob ntawm lub sijhawm ntawm kev txhaj tshuaj, mus rau lub sijhawm subpicosecond (3b). Ntawd yog, nrog rau qhov chaw zoo tshaj plaws, lub tshuab hluav taws xob yuav ua tiav ib nrab-lub voj voog ntawm terahertz hluav taws xob acceleration hauv txhua txheej (3c ib).
Yog tias cov electrons tuaj txog ntawm lub sijhawm sib txawv, lawv muaj kev nrawm dua hauv thawj txheej, uas ua rau lawv siv sijhawm ntev dua los ntawm nws. Lub desynchronization ces nce nyob rau hauv cov khaubncaws sab nraud povtseg hauv qab no, ua rau tsis xav slowdown (3d).
Txhawm rau kom txo qis qhov tsis zoo ntawm lub cev txuas ntxiv ntawm cov nqaj hluav taws xob, thawj lub tshuab STEAM ua haujlwm hauv hom compression. Lub sijhawm hluav taws xob hluav taws xob ntawm lub linac tau ua kom zoo rau qhov tsawg kawg nkaus ntawm ~ 350 fs (ib nrab-dav) los ntawm kev kho lub terahertz lub zog muab rau lub compressor thiab hloov lub linac rau hom hatch (4b).
Duab #4
Qhov tsawg kawg nkaus beam ntev tau teeb tsa raws li lub sijhawm ntawm photocathode UV mem tes, uas yog ~ 600 fs. Qhov kev ncua deb ntawm lub compressor thiab lub sawb kuj ua lub luag haujlwm tseem ceeb, uas txwv qhov ceev ntawm lub zog thickening. Ua ke, cov kev ntsuas no pab kom femtosecond precision nyob rau hauv txhaj tshuaj theem ntawm acceleration theem.
Ntawm daim duab 4 Nws tuaj yeem pom tias lub zog sib kis ntawm cov kab hluav taws xob compressed tom qab optimized acceleration nyob rau hauv ib tug linear accelerator txo los ntawm ~ 4 zaug piv rau uncompressed ib. Vim acceleration, lub zog spectrum ntawm lub compressed beam yog hloov mus rau ntau zog, nyob rau hauv sib piv rau lub uncompressed beam. Lub ncov ntawm lub zog spectrum tom qab acceleration yog hais txog 115 keV, thiab lub siab-lub zog tail nce mus txog 125 keV.
Cov duab no, raws li cov lus qhia me me ntawm cov kws tshawb fawb, yog cov ntaub ntawv ceev ceev tshiab (ua ntej acceleration nws yog 70 keV) nyob rau hauv terahertz ntau.
Tab sis txhawm rau txo lub zog tawg (4), ib qho luv luv beam yuav tsum tau ua tiav.
Duab #5
Nyob rau hauv cov ntaub ntawv ntawm ib tug uncompressed qhia beam, parabolic dependence ntawm lub beam loj ntawm lub tam sim no qhia cov transverse emittance nyob rau hauv kab rov tav thiab ntsug cov lus qhia: Ξ΅x, n = 1.703 mm * mrad thiab Ξ΅y, n = 1.491 mm * mrad (5).
Compression, nyob rau hauv lem, txhim kho lub transverse emittance los ntawm 6 lub sij hawm rau Ξ΅x, n = 0,285 mm * mrad (kab rov tav) thiab Ξ΅y, n = 0,246 mm * mrad (ntev).
Nws yog ib qho tsim nyog sau cia tias qhov kev txo qis ntawm cov emittance yog kwv yees li ob npaug ntawm qhov loj ntawm qhov kev txo qis ntawm cov nqaj ntev, uas yog qhov ntsuas ntawm qhov tsis sib xws ntawm kev sib cuam tshuam nrog lub sij hawm thaum cov hluav taws xob muaj zog tsom thiab defocusing ntawm cov hlau nplaum thaum lub sij hawm acceleration (5b ΠΈ 5c ib).
Ntawm daim duab 5b Nws tuaj yeem pom tau tias cov khoom siv hluav taws xob tau qhia nyob rau lub sijhawm zoo tshaj plaws ntawm tag nrho ib nrab-lub voj voog ntawm cov hluav taws xob acceleration. Tab sis cov hluav taws xob uas tuaj txog ua ntej lossis tom qab lub sijhawm zoo muaj kev nrawm dua thiab txawm tias ib nrab deceleration. Xws li electrons xaus nrog tsawg zog, hais lus ntxhib.
Ib qho xwm txheej zoo sib xws yog pom thaum raug cov hlau nplaum. Cov hluav taws xob txhaj tshuaj ntawm lub sijhawm zoo tshaj plaws muaj qhov sib npaug ntawm qhov zoo thiab qhov tsis zoo ntawm cov hlau nplaum. Yog tias qhov kev taw qhia ntawm electrons tshwm sim ua ntej lub sijhawm zoo, ces muaj ntau qhov zoo thiab tsawg dua qhov tsis zoo. Yog tias cov khoom siv hluav taws xob tau tshaj tawm tom qab lub sijhawm zoo, yuav muaj tsawg dua qhov zoo thiab tsis zoo (5c ib). Thiab xws li deviations ua rau lub fact tias lub electron yuav deviate mus rau sab laug, sab xis, nce los yog down, nyob ntawm seb nws txoj hauj lwm txheeb ze rau lub axis, uas ua rau kom ib tug nce nyob rau hauv lub transverse momentum sib haum mus rau focusing los yog defocusing ntawm lub beam.
Rau cov ncauj lus kom ntxaws ntxiv nrog cov nuances ntawm txoj kev tshawb no, kuv xav kom saib ΠΈ rau nws.
Epilogue
Nyob rau hauv cov ntsiab lus, accelerator kev ua tau zoo yuav nce yog tias lub sij hawm ntawm lub electron beam raug txo. Hauv kev ua haujlwm no, lub sijhawm ua tiav ntawm cov nqaj tau raug txwv los ntawm geometry ntawm lub installation. Tab sis, nyob rau hauv txoj kev xav, lub sij hawm beam tuaj yeem ncav cuag tsawg dua 100 fs.
Cov kws tshawb fawb kuj tau sau tseg tias qhov zoo ntawm cov nqaj tuaj yeem txhim kho ntxiv los ntawm kev txo qis qhov siab ntawm cov txheej thiab ua kom lawv cov lej. Txawm li cas los xij, txoj kev no tsis yog tsis muaj teeb meem, tshwj xeeb tshaj yog nce qhov nyuaj ntawm kev tsim cov cuab yeej.
Txoj haujlwm no yog thawj theem ntawm kev kawm ntau dua thiab nthuav dav ntawm cov qauv me me ntawm cov kab nrawm nrawm. Txawm hais tias qhov tseeb tias qhov kev sim version twb tau qhia cov txiaj ntsig zoo, uas tuaj yeem raug hu ua cov ntaub ntawv tawg, tseem muaj ntau txoj haujlwm ua.
Ua tsaug rau kev nyeem ntawv, nyob xav paub thiab muaj lub lim tiam zoo! π
Ua tsaug uas koj nyob nrog peb. Koj puas nyiam peb cov ntawv? Xav pom cov ntsiab lus nthuav ntxiv? Txhawb nqa peb los ntawm kev tso ib qho kev txiav txim lossis qhia rau cov phooj ywg, 30% luv nqi rau cov neeg siv Habr ntawm qhov tshwj xeeb analogue ntawm nkag-theem servers, uas tau tsim los ntawm peb rau koj: (muaj nrog RAID1 thiab RAID10, mus txog 24 cores thiab mus txog 40GB DDR4).
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