Isimiso esijwayelekile sokuthi “okuningi kunamandla kakhulu” sekunesikhathi eside sasungulwa emikhakheni eminingi yomphakathi, kuhlanganise nesayensi nobuchwepheshe. Kodwa-ke, emaqinisweni anamuhla, ukuqaliswa okusebenzayo kwesisho esithi "okuncane, kodwa okunamandla" kuya ngokuya kuvame kakhulu. Lokhu kubonakala kokubili kumakhompiyutha, ngaphambili ayethatha ikamelo lonke, kodwa manje angena entendeni yesandla somntwana, kanye nama-accelerator ezinhlayiyana ezikhokhisiwe. Yebo, khumbula iLarge Hadron Collider (LHC), obukhulu bayo obuhlaba umxhwele (26 m ubude) buboniswe ngokwezwi nezwi egameni layo? Ngakho-ke, lokhu sekuvele kuyinto yesikhathi esidlule ngokusho kososayensi abavela ku-DESY, abaye bahlakulela inguqulo encane ye-accelerator, engeyona engaphansi ekusebenzeni kokwandulele usayizi ogcwele. Ngaphezu kwalokho, i-accelerator encane yaze yabeka irekhodi lomhlaba elisha phakathi kwama-accelerator e-terahertz, okuphinda kabili amandla ama-electron ashumekiwe. Sathuthukiswa kanjani isisheshisi esincane, yiziphi izimiso eziyisisekelo zokusebenza kwaso, futhi ukuhlola okungokoqobo kuye kwabonisani? Umbiko weqembu locwaningo uzosisiza ukuthi sithole mayelana nalokhu. Hamba.
Isisekelo socwaningo
Ngokuka-Dongfang Zhang kanye nozakwabo kwa-DESY (German Electron Synchrotron), abathuthukise i-mini-accelerator, imithombo ye-electron esheshayo idlala indima ebaluleke ngendlela emangalisayo empilweni yomphakathi wanamuhla. Eziningi zazo zivela kwezokwelapha, ukuthuthukiswa electronics kanye nocwaningo lwesayensi. Inkinga enkulu ngama-accelerator akhona manje asebenzisa ama-oscillator omsakazo izindleko zawo eziphezulu, ingqalasizinda eyinkimbinkimbi, kanye nokusetshenziswa kwamandla okuhlaba umxhwele. Futhi ukushiyeka okunjalo kukhawulela kakhulu ukutholakala kobuchwepheshe obunjalo ebangeni elibanzi labasebenzisi.
Lezi zinkinga ezisobala ziyisisusa esihle sokuthuthukisa amadivayisi ubukhulu bawo namandla asetshenziswayo angeke abangele ukwethuka.
Phakathi kwamanoveli ahlobene kulo mkhakha kukhona ama-accelerator e-terahertz, anenani “lezinzuzo”:
- Kulindeleke ukuthi amaza amafushane nama-pulses amafushane emisebe ye-terahertz azokwandisa kakhulu umkhawulo ukwehlukana*, okubangelwa insimu, okuzokwandisa ama-gradients okusheshisa;
Ukuphuka kukagesi* - Ukwenyuka okubukhali kwamandla amanje lapho kusetshenziswa i-voltage engaphezu kwesibucayi.
- ukuba khona kwezindlela ezisebenzayo zokukhiqiza imisebe ye-terahertz ephezulu yenkundla ivumela ukuvumelanisa kwangaphakathi phakathi kwama-electron nezinkambu ezivusa amadlingozi;
- Izindlela zakudala zingasetshenziswa ukudala amadivaysi anjalo, kodwa izindleko zabo, isikhathi sokukhiqiza kanye nosayizi kuzoncishiswa kakhulu.
Ososayensi bakholelwa ukuthi i-millimeter-scale terahertz accelerator yabo iwukuvumelana phakathi kwama-accelerator avamile atholakalayo njengamanje nama-micro-accelerator athuthukiswayo, kodwa anobubi obuningi ngenxa yobukhulu bawo obuncane kakhulu.
Abacwaningi abaphiki ukuthi ubuchwepheshe bokusheshisa i-terahertz buye bathuthuka isikhathi eside. Kodwa-ke, ngokombono wabo, zisekhona izici eziningi kule ndawo ezingazange zifundwe, zihlolwe noma zisetshenziswe.
Emsebenzini wabo, esiwucabangela namuhla, ososayensi bakhombisa amakhono e-STEAM (i-terahertz electron accelerator ne-manipulator) - isisheshisi se-electron esihlukanisiwe se-terahertz kanye ne-manipulator. I-STEAM yenza kube nokwenzeka ukunciphisa ubude be-electron beam ibe ubude be-picosecond, ngaleyo ndlela inikeze ukulawula kwe-femtosecond phezu kwesigaba sokusheshisa.
Kube nokwenzeka ukuzuza inkambu yokusheshisa engu-200 MV/m (MV - megavolt), okuholela ekusheshisweni kwerekhodi le-terahertz> 70 keV (kiloelectronvolt) kusuka ku-electron beam eshumekiwe enamandla angu-55 keV. Ngale ndlela, ama-electron asheshisiwe afika ku-125 keV atholakala.
Ukwakheka nokusetshenziswa kwedivayisi
Isithombe esingu-1: idayagramu yedivayisi esacwaningwayo.
Isithombe esingu-1-2: a - umdwebo wesakhiwo esinezingqimba ezi-5 ezithuthukisiwe, b - isilinganiso sokusheshisa okubaliwe kanye nesiqondiso sokusabalalisa kwe-electron.
Imishayo ye-electron (55 keV) ikhiqizwa kusukela isibhamu se-electron* futhi zingeniswa ku-terahertz STEAM-buncher (i-compressor ye-beam), ngemva kwalokho zidlulela ku-STEAM-linac (i-accelerator*).
Isibhamu se-electron* — isisetshenziswa sokukhiqiza isigxobo sama-electron sokucushwa okudingekayo namandla.
Isisheshisi somugqa* - i-accelerator lapho izinhlayiya ezishajiwe zidlula esakhiweni kanye kuphela, ehlukanisa i-accelerator eqondile kune-cyclic (isibonelo, i-LHC).
Womabili amadivaysi e-STEAM athola ama-terahertz pulses kusuka kulaser eyodwa eseduze ne-infrared (NIR), ephinde idubule i-photocathode yesibhamu se-electron, okuholela ekuvunyelanisweni kwangaphakathi phakathi kwama-electron nezinkambu ezisheshisayo. I-Ultraviolet pulses ye-photoemission ku-photocathode ikhiqizwa ngezigaba ezimbili ezilandelanayo GVG* ubude begagasi obuyisisekelo bokukhanya okuseduze kwe-infrared. Le nqubo iguqula i-laser pulse engu-1020 nm kuqala ibe ngu-510 nm bese iba ku-255 nm.
GVG* (isizukulwane sesibili se-harmonic se-optical) inqubo yokuhlanganisa ama-photon we-frequency efanayo ngesikhathi sokusebenzisana ne-nonlinear material, okuholela ekwakhekeni kwama-photon amasha anamandla aphindwe kabili kanye nemvamisa, kanye nengxenye yobude be-wavelength.
Ingxenye esele ye-laser ye-NIR ihlukaniswe yaba yimishayo emi-4, esetshenziselwa ukukhiqiza ama-terahertz amane omjikelezo owodwa ngokudala umehluko wefrikhwensi ye-intra-pulse.
Amapayipi amabili e-terahertz abe eselethwa kudivayisi ngayinye ye-STEAM ngezakhiwo zophondo olulinganayo eziqondisa amandla e-terahertz endaweni yokusebenzisana yonkana indlela yokusakazeka kwama-electron.
Uma ama-electron engena kudivayisi ngayinye ye-STEAM, achayeka ezingxenyeni zikagesi nezikazibuthe Lorentz forces*.
Lorentz force* - amandla inkambu ye-electromagnetic esebenza ngawo ezinhlayiyeni ezishajiwe.
Kulesi simo, insimu kagesi inesibopho sokusheshisa nokunciphisa, futhi insimu yamagnetic ibangela ukuphambuka kwe-lateral.
Isithombe #2
Njengoba sibona ezithombeni I-2 и 2b, Ngaphakathi kwedivayisi ngayinye ye-STEAM, imishayo ye-terahertz ihlukaniswa ngokuphambana ngamashidi ensimbi azacile abe yizingqimba ezimbalwa zogqinsi oluhlukahlukene, ngayinye esebenza njenge-waveguide, idlulisela ingxenye yengqikithi yamandla endaweni yokusebenzisana. Kukhona futhi amapuleti e-dielectric kungqimba ngayinye ukuze axhumanise isikhathi sokufika se-terahertz gagasa phambili* ngengaphambili lama-electron.
I-Wavefront* - indawo lapho igagasi lifinyelele khona.
Womabili amadivaysi e-STEAM asebenza kumodi kagesi, okungukuthi, ngendlela yokuphoqelela inkambu kagesi futhi acindezele inkambu kazibuthe emaphakathi nendawo yokusebenzisana.
Edivayisini yokuqala, ama-electron abekwe isikhathi ukuze adlule Ukuwela uziro* insimu ye-terahertz, lapho ama-gradients esikhathi senkambu kagesi enziwa abe nkulu futhi inkambu evamile incishisiwe.
Ukuwela iqanda* - iphuzu lapho kungekho ukungezwani.
Lokhu kumiswa kubangela ukuthi umsila we-electron beam usheshe futhi ikhanda lawo linciphe, okuholela ekugxilweni kwe-ballistic longitudinal (I-2 и 2s).
Edivayisini yesibili, ukuvumelanisa kwemisebe ye-electron kanye ne-terahertz kusethwe ukuze isigxobo se-electron sihlangabezane nomjikelezo omubi kuphela wensimu kagesi ye-terahertz. Lokhu kulungiselelwa kuphumela ekusheshiseni okuqhubekayo okuqhubekayo (2b и 2d).
Ilaser ye-NIR iwuhlelo lwe-Yb:YLF olupholile ngokukhaliphile olukhiqiza ama-optical pulses ubude besikhathi esingu-1.2 ps namandla angu-50 mJ kubude begagasi obungu-1020 nm kanye nezinga lokuphindaphinda elingu-10 Hz. Futhi ama-terahertz pulses anemvamisa emaphakathi engu-0.29 terahertz (inkathi engu-3.44 ps) akhiqizwa indlela yangaphambili ye-pulse ethagekile.
Ukuze kunikwe amandla i-STEAM-buncher (i-compressor ye-beam) kwasetshenziswa kuphela u-2 x 50 nJ wamandla e-terahertz, futhi i-STEAM-linac (isisheshisi esinomugqa) sidinga u-2 x 15 mJ.
Ububanzi bezimbobo zokungena neziphumayo zazo zombili izisetshenziswa ze-STEAM zingama-microns angu-120.
I-compressor ye-beam iklanywe ngezingqimba ezintathu zobude obulinganayo (0 mm), ezifakwe amapuleti e-silica ahlanganisiwe (ϵr = 225) ubude obungu-4.41 no-0.42 mm ukulawula isikhathi. Ukuphakama okulinganayo kwezingqimba ze-compressor kubonisa iqiniso lokuthi akukho ukusheshisa (2s).
Kodwa ku-accelerator eqondile ukuphakama sekuhlukile kakade - 0.225, 0.225 no-0.250 mm (+ amapuleti e-quartz ahlanganisiwe angu-0.42 no-0.84 mm). Ukwanda kokuphakama kwesendlalelo kuchaza ukwanda kwejubane lama-electron ngesikhathi sokusheshisa.
Ososayensi bayaqaphela ukuthi inani lezendlalelo libophezelekile ngokuqondile ekusebenzeni kwedivayisi ngayinye kokubili. Ukufinyelela amazinga aphezulu okusheshisa, isibonelo, kuzodinga izendlalelo eziningi kanye nokulungiselelwa okuhlukile kobude ukuze kuthuthukiswe ukusebenzisana.
Imiphumela yokuhlolwa okusebenzayo
Okokuqala, abacwaningi bakhumbuza ukuthi kuma-accelerators omsakazo wendabuko, umthelela wezinga lesikhashana le-electron beam eshumekiwe ezimpahleni ze-beam esheshayo kungenxa yoshintsho emkhakheni kagesi okuhlangenwe nakho ngesikhathi sokusebenzisana kwama-electron ahlukene ngaphakathi kwe-beam efika. ngezikhathi ezahlukene. Ngakho-ke, kungalindelwa ukuthi amasimu anama-gradient aphezulu kanye nemishayo enesikhathi eside azoholela ekusabalaleni okukhulu kwamandla. Imishayo ejovwe yesikhathi eside ingaholela kumavelu aphezulu ukukhishwa*.
I-Emittance* - Isikhala sesigaba esithathwe yi-beam esheshayo yezinhlayiya ezishajiwe.
Endabeni yesisheshisi se-terahertz, isikhathi senkambu yenjabulo cishe sifushane izikhathi ezingu-200. Ngakho, ukungezwani* inkambu esekelwe izoba phezulu izikhathi ezingu-10.
Amandla enkundla kagesi* - inkomba yensimu kagesi, elingana nesilinganiso samandla asetshenziswe eshadini lephoyinti elimile elibekwe endaweni ethile ensimini kuya kubukhulu balokhu kukhokha.
Ngakho-ke, ku-accelerator ye-terahertz, ama-gradient asensimini atholwa ama-electron angaba ama-oda amaningana obukhulu aphakeme kunasesisetshenziswa esivamile. Isilinganiso sesikhathi lapho ijika lenkundla libonakala khona lizoba lincane kakhulu. Kulandela kulokhu ukuthi ubude be-electron beam eyethulwe buyoba nomphumela ozwakalayo.
Ososayensi banquma ukuhlola lezi zinkolelo-mbono ngokusebenza. Ukuze benze lokhu, bethula imishayo yama-electron yobude obuhlukahlukene, eyayilawulwa ngokucindezelwa kusetshenziswa idivayisi yokuqala ye-STEAM (STEAM-buncher).
Isithombe #3
Esimeni lapho i-compressor yayingaxhunywanga kumthombo wamandla, imishayo yama-electron (55 keV) eneshaji engu-∼1 fC (femtocoulomb) yadlula cishe u-300 mm isuka kusibhamu se-electron yaya emshinini wokusheshisa umugqa (STEAM-linac). Lawa ma-electron angakhula ngaphansi kwethonya lokushaja komkhathi kuze kube isikhathi esingaphezu kuka-1000 fs (femtoseconds).
Ngalesi sikhathi, i-electron beam ithathe cishe u-60% wesigamu-wavelength wenkundla esheshayo ngemvamisa engu-1,7 ps, okuholele ku-post-acceleration energy spectrum enenani eliphakeme elingu-115 keV kanye nohhafu wobubanzi bokusabalalisa amandla. ngaphezu kuka-60 keV (I-3).
Ukuze uqhathanise le miphumela naleyo elindelekile, isimo sokusatshalaliswa kwama-electron ngesisheshisi esiwumugqa siye salingiswa lapho ama-electron ayengasavumelanisi (okungukuthi, awahambisani) nesikhathi sokujova esilungile. Izibalo zalesi simo zibonise ukuthi ukwanda kwamandla e-electron kuncike kakhulu esikhathini sokujova, kuze kufike esikalini sesikhathi se-subpicosecond (3b). Okusho ukuthi, ngokusetha okuhle, i-electron izothola umjikelezo ogcwele wesigamu sokusheshisa kwemisebe ye-terahertz kungqimba ngalunye (3s).
Uma ama-electron efika ngezikhathi ezihlukene, athola ukusheshisa okuncane kungqimba lokuqala, okuwenza athathe isikhathi eside ukuhamba kuwo. Ukususwa kokuvumelanisa bese kukhuphuka ezingqimbeni ezilandelayo, okubangela ukwehla okungafuneki (3d).
Ukuze kuncishiswe umphumela ongemuhle wesandiso sesikhashana se-electron beam, idivayisi yokuqala ye-STEAM yasebenza ngemodi yokuminyanisa. Ubude besikhathi be-electron beam ku-linac buthuthukiswe ukuba bube ubuncane obungu-~350 fs (uhhafu wobubanzi) ngokulungisa amandla e-terahertz anikezwa i-compressor nokushintsha i-linac ibe imodi yokuchamusela (4b).
Isithombe #4
Ubuncane besikhathi be-beam bamiswa ngokuhambisana nobude besikhathi se-photocathode UV pulse, obungu-~600 fs. Ibanga phakathi kwe-compressor kanye ne-strip nayo yadlala indima ebalulekile, eyanciphisa isivinini samandla aqina. Ngokuhlangene, lezi zinyathelo zinika amandla ukunemba kwe-femtosecond esigabeni somjovo sesigaba sokusheshisa.
Esithombeni I-4 kungabonakala ukuthi ukusabalala kwamandla ensimbi ecindezelweyo ye-electron ngemva kokusheshisa okulungiselelwe ku-accelerator yomugqa kwehla ngo-~ izikhathi ezingu-4 uma kuqhathaniswa nengacindezelwanga. Ngenxa yokusheshisa, i-spectrum yamandla ye-beam ecindezelwe ishintshelwa kumandla aphezulu, ngokungafani ne-beam engacindezelwanga. Ukuphakama kwe-spectrum yamandla ngemva kokusheshisa cishe ku-115 keV, futhi umsila onamandla amakhulu ufinyelela cishe ku-125 keV.
Lezi zibalo, ngokusho kwesitatimende esithobekile sososayensi, irekhodi elisha lokusheshisa (ngaphambi kokusheshisa bekuyi-70 keV) ebangeni le-terahertz.
Kodwa ukuze kuncishiswe ukuhlakazeka kwamandla (I-4), kufanele kuzuzwe ugongolo olufushane nakakhulu.
Isithombe #5
Esimeni se-beam eyethulwe engacindezelwanga, ukuncika kwe-parabolic kosayizi we-beam kweyamanje kuveza ukuphuma kwe-transverse kuzikhombisi-ndlela ezivundlile nezime mpo: εx,n = 1.703 mm*mrad kanye ne-εy,n = 1.491 mm*mrad (I-5).
Ukuminyanisa, nakho, kuthuthukise ukuphuma okuphambeneyo izikhathi ezingu-6 ukuze εx,n = 0,285 mm*mrad (evundlile) kanye no-εy,n = 0,246 mm*mrad (iqondile).
Kuyaphawuleka ukuthi izinga lokuncishiswa kwe-emittance licishe libe likhulu ngokuphindwe kabili kunezinga lokuncishiswa kobude be-beam, okuyisilinganiso sokungaqondile komugqa we-dynamics yokusebenzisana ngesikhathi lapho ama-electron ethola ukugxila okuqinile nokungagxili kwensimu kazibuthe ngesikhathi sokusheshisa (5b и 5s).
Esithombeni 5b Kungabonakala ukuthi ama-electron ethulwe ngesikhathi esifanele ahlangabezana nayo yonke ingxenye yomjikelezo wokusheshisa kwenkundla kagesi. Kodwa ama-electron afika ngaphambi noma ngemva kwesikhathi esilungile ahlangabezana nokusheshisa okuncane ngisho nokwehla kancane kancane. Ama-electron anjalo agcina esenamandla amancane, uma sikhuluma nje.
Isimo esifanayo siyabonwa lapho sichayeka endaweni kazibuthe. Ama-electron ajovwe ngesikhathi esilungile ahlangabezana namanani alinganayo wezinkambu kazibuthe eziphozithivu nezingezinhle. Uma ukwethulwa kwama-electron kwenzeka ngaphambi kwesikhathi esifanele, khona-ke kwakukhona izinkambu eziningi ezinhle kanye nezimbalwa ezimbi. Uma ama-electron ethulwa kamuva kunesikhathi esifanele, kuzoba mbalwa okuhle nokubi kakhulu (5s). Futhi ukuphambuka okunjalo kuholela eqinisweni lokuthi i-electron ingaphambukela ngakwesobunxele, kwesokudla, phezulu noma phansi, kuye ngokuthi isikhundla sayo esihlobene ne-eksisi, okuholela ekwandeni komfutho oguquguqukayo ohambisana nokugxila noma ukuchithwa kwe-beam.
Ukuze uthole ulwazi oluningiliziwe ngama-nuances ocwaningo, ngincoma ukubheka и kuyena.
Epilogue
Kafushane, ukusebenza kwe-accelerator kuzokhuphuka uma ubude be-electron beam buncishisiwe. Kulo msebenzi, ubude be-beam obufinyelelekayo bukhawulelwe yijometri yokufakwa. Kodwa, ngokombono, ubude bensimbi bungafinyelela ngaphansi kuka-100 fs.
Ososayensi baphinde baqaphele ukuthi izinga le-beam lingathuthukiswa ngokuqhubekayo ngokunciphisa ukuphakama kwezingqimba nokwandisa inombolo yazo. Nokho, le ndlela ayinazo izinkinga, ikakhulukazi ukwandisa inkimbinkimbi yokukhiqiza idivayisi.
Lo msebenzi uyisigaba sokuqala socwaningo olunzulu futhi olunemininingwane yenguqulo encane yesisheshisi esiwumugqa. Naphezu kweqiniso lokuthi inguqulo ehloliwe isivele ibonisa imiphumela emihle kakhulu, engabizwa ngokufanelekile ngokuthi ukuphulwa kwerekhodi, kusenomsebenzi omningi okufanele wenziwe.
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Source: www.habr.com