Mfundo yodziwika bwino yakuti “zochuluka n’zamphamvu kwambiri” yakhazikitsidwa kalekale m’magulu ambiri a anthu, kuphatikizapo sayansi ndi luso lazopangapanga. Komabe, muzochitika zamakono, kukhazikitsidwa kothandiza kwa mawu oti "wang'ono, koma amphamvu" akuchulukirachulukira. Izi zikuwonetseredwa mu makompyuta, omwe kale adatenga chipinda chonse, koma tsopano akuyenera m'manja mwa mwana, ndi ma particle accelerators. Inde, kumbukirani Large Hadron Collider (LHC), yomwe miyeso yake yochititsa chidwi (26 m kutalika) imasonyezedwa m'dzina lake? Kotero, ichi ndi chinthu chakale kale malinga ndi asayansi ochokera ku DESY, omwe apanga kachidutswa kakang'ono ka accelerator, chomwe sichiri chochepa pakuchitapo kanthu kwa omwe adatsogolera kukula kwake. Kuphatikiza apo, mini accelerator idayika mbiri yatsopano padziko lonse lapansi pakati pa ma terahertz accelerators, kuwirikiza kawiri mphamvu zama elekitironi ophatikizidwa. Kodi chothamangitsira chaching'onocho chinapangidwa bwanji, mfundo zazikuluzikulu za kagwiritsidwe ntchito kake ndi chiyani, ndipo zoyeserera zenizeni zasonyeza chiyani? Lipoti la gulu lofufuza litithandiza kudziwa za izi. Pitani.
Maziko ofufuza
Malinga ndi Dongfang Zhang ndi anzake ku DESY (German Electron Synchrotron), amene anapanga mini-accelerator, ultrafast magwero elekitironi amagwira ntchito yofunika kwambiri pa moyo wa anthu amakono. Ambiri aiwo amawoneka muzamankhwala, chitukuko chamagetsi komanso kafukufuku wasayansi. Vuto lalikulu ndi ma accelerator amakono omwe amagwiritsa ntchito ma radio frequency oscillator ndi mtengo wawo wokwera, zomangamanga zovuta, komanso kugwiritsa ntchito mphamvu modabwitsa. Ndipo zophophonya zotere zimachepetsa kwambiri kupezeka kwa matekinoloje otere kwa ogwiritsa ntchito ambiri.
Mavuto odziwikiratu awa ndi chilimbikitso chachikulu chopanga zida zomwe kukula kwake ndi kugwiritsa ntchito mphamvu sikungayambitse mantha.
Zina mwazachilendo pamakampaniwa ndi ma terahertz accelerators, omwe ali ndi "maubwino" angapo:
- Zikuyembekezeka kuti mafunde amfupi ndi mafunde amfupi a radiation ya terahertz aziwonjezera kwambiri sweka*, chifukwa cha munda, umene udzawonjezera mathamangitsidwe gradient;
Kuwonongeka kwamagetsi * - kuwonjezereka kwakukulu kwa mphamvu zamakono pamene voteji pamwamba pa yovuta ikugwiritsidwa ntchito.
- kukhalapo kwa njira zothandiza zopangira ma radiation a terahertz apamwamba amalola kulumikizana kwamkati pakati pa ma elekitironi ndi minda yosangalatsa;
- Njira zamakono zingagwiritsidwe ntchito popanga zipangizo zoterezi, koma mtengo wawo, nthawi yopangira ndi kukula zidzachepetsedwa kwambiri.
Asayansi amakhulupirira kuti ma millimeter-scale terahertz accelerator ndi kusagwirizana pakati pa ma accelerator ochiritsira omwe alipo panopa ndi ma micro-accelerator omwe akupangidwa, koma ali ndi zovuta zambiri chifukwa cha kukula kwawo kochepa kwambiri.
Ofufuza samakana kuti ukadaulo wothamangitsa terahertz wakhala ukukula kwakanthawi. Komabe, m'malingaliro awo, pali zinthu zambiri m'derali zomwe sizinaphunzire, kuyesedwa kapena kukhazikitsidwa.
Mu ntchito yawo, yomwe tikukambirana lero, asayansi akuwonetsa kuthekera kwa STEAM (Segmented terahertz electron accelerator ndi manipulator) - terahertz electron accelerator ndi manipulator. STEAM imapangitsa kuti zitheke kuchepetsa kutalika kwa mtengo wa elekitironi kukhala nthawi yayitali ya picosecond, potero kupatsa mphamvu ya femtosecond pagawo lothamangitsa.
Zinali zotheka kukwaniritsa mathamangitsidwe munda wa 200 MV/m (MV - megavolt), zomwe zimatsogolera mbiri terahertz mathamangitsidwe> 70 keV (kiloelectronvolt) kuchokera ophatikizidwa elekitironi mtengo ndi mphamvu ya 55 keV. Mwanjira iyi, ma elekitironi othamanga mpaka 125 keV adapezedwa.
Kapangidwe kachipangizo ndi kukhazikitsa
Chithunzi 1: chithunzi cha chipangizo chomwe chikuphunziridwa.
Chithunzi No. 1-2: a - chithunzi cha mapangidwe opangidwa ndi 5-wosanjikiza magawo, b - chiŵerengero cha mathamangitsidwe owerengeka ndi malangizo a kufalitsa ma elekitironi.
Ma elekitironi (55 keV) amapangidwa kuchokera electron mfuti* ndipo amalowetsedwa mu terahertz STEAM-buncher (mtengo compressor), pambuyo pake amadutsa mu STEAM-linac (linear accelerator*).
Mfuti ya electron* - chida chopangira mtengo wa ma elekitironi a kasinthidwe kofunikira ndi mphamvu.
Linear accelerator* - accelerator momwe tinthu zoyipiridwa zimadutsamo kamodzi kokha, zomwe zimasiyanitsa chowongolera chotsatira kuchokera ku cyclic (mwachitsanzo, LHC).
Zipangizo zonse ziwiri za STEAM zimalandila ma terahertz kuchokera ku laser imodzi yapafupi ndi infrared (NIR), yomwe imayatsanso photocathode yamfuti ya ma elekitironi, zomwe zimapangitsa kulumikizana kwamkati pakati pa ma elekitironi ndi magawo omwe akufulumizitsa. Ma ultraviolet pulses a photoemission pa photocathode amapangidwa kudzera mu magawo awiri otsatizana GVG* kutalika kwa mafunde apafupi ndi infrared. Izi zimatembenuza 1020 nm laser pulse poyamba kukhala 510 nm ndiyeno kukhala 255 nm.
GVG* (optical second harmonic generation) ndi njira yophatikizira ma photon a ma frequency omwewo panthawi yolumikizana ndi zinthu zopanda malire, zomwe zimatsogolera kupanga ma photon atsopano omwe ali ndi mphamvu ziwiri ndi mafupipafupi, komanso theka la kutalika kwake.
Chotsalira cha mtengo wa laser wa NIR chimagawika kukhala mizati 4, yomwe imagwiritsidwa ntchito kupanga ma terahertz anayi amtundu umodzi popanga ma frequency a intra-pulse.
Ma terahertz awiriwa amaperekedwa ku chipangizo chilichonse cha STEAM kudzera m'manyanga ofananira omwe amawongolera mphamvu ya terahertz kudera lomwe limalumikizana kudutsa komwe kumafalikira ma elekitironi.
Ma electron akalowa pa chipangizo chilichonse cha STEAM, amakumana ndi zida zamagetsi ndi maginito Lorentz forces*.
Lorentz Force* - mphamvu yomwe gawo lamagetsi lamagetsi limagwirira ntchito pa tinthu tambiri.
Pachifukwa ichi, gawo lamagetsi ndilomwe limayambitsa kuthamanga ndi kutsika, ndipo mphamvu ya maginito imayambitsa kusokonezeka.
Chithunzi #2
Monga tikuonera pazithunzi 2 и 2b, M'kati mwa chipangizo chilichonse cha STEAM, zitsulo za terahertz zimagawidwa mozungulira ndi mapepala achitsulo opyapyala kukhala zigawo zingapo za makulidwe osiyanasiyana, zomwe zimakhala ngati mafunde, kusamutsira gawo la mphamvu zonse ku dera lolumikizana. Palinso mbale za dielectric pagawo lililonse kuti zigwirizane ndi nthawi yofika ya terahertz gwero lakutsogolo* ndi kutsogolo kwa ma elekitironi.
Wavefront* - pamwamba pomwe mafunde afika.
Zipangizo zonse ziwiri za STEAM zimagwira ntchito mumagetsi, ndiko kuti, m'njira yokakamiza mphamvu yamagetsi ndikupondereza mphamvu ya maginito pakatikati pa malo olumikizirana.
Pachida choyamba, ma elekitironi amayikidwa nthawi kuti adutse kuwoloka ziro* kumunda wa terahertz, komwe ma gradient a nthawi yamagetsi amakulitsidwa ndipo gawo lapakati limachepetsedwa.
Zero kuwoloka* - pomwe palibe mikangano.
Kukonzekera uku kumapangitsa kuti mchira wa mtengo wa elekitironi ukufulumire komanso kuti mutu wake uchepe, zomwe zimapangitsa kuti pakhale kuyang'ana kwakutali (ballistic longitudinal)2 и 2s).
Pachida chachiwiri, kulumikizana kwa ma electron ndi terahertz kumayikidwa kotero kuti mtengo wa electron umakhala ndi kuzungulira koyipa kwa gawo lamagetsi la terahertz. Kukonzekera uku kumabweretsa chiwonjezeko chopitilira muyeso (2b и 2d).
Laser ya NIR ndi njira yoziziritsa bwino ya Yb:YLF yomwe imapanga ma pulses owoneka a 1.2 ps kutalika ndi 50 mJ mphamvu pamlingo wa 1020 nm ndi kubwereza kwa 10 Hz. Ndipo ma terahertz omwe ali ndi ma frequency apakati a 0.29 terahertz (nthawi ya 3.44 ps) amapangidwa ndi njira yakutsogolo ya pulse.
Kuti apange mphamvu ya STEAM-buncher (beam compressor) 2 x 50 nJ ya mphamvu ya terahertz yokha ndiyomwe idagwiritsidwa ntchito, ndipo STEAM-linac (linac) inkafunika 2 x 15 mJ.
Kutalika kwa mabowo olowera ndi kutulutsa kwa zida zonse za STEAM ndi ma microns 120.
Compressor yamtengowo imapangidwa ndi zigawo zitatu za kutalika kofanana (0 mm), zomwe zimakhala ndi mbale za silika zosakanikirana (ϵr = 225) zautali 4.41 ndi 0.42 mm kuti azilamulira nthawi. Kutalika kofanana kwa zigawo za kompresa kukuwonetsa kuti palibe mathamangitsidwe (2s).
Koma mu liniya accelerator kutalika kale osiyana - 0.225, 0.225 ndi 0.250 mm (+ anasakaniza mbale quartz 0.42 ndi 0.84 mm). Kuwonjezeka kwa kutalika kwa wosanjikiza kumatanthawuza kuwonjezeka kwa liwiro la ma electron panthawi yothamanga.
Asayansi amaona kuti chiwerengero cha zigawo ndi udindo mwachindunji ntchito iliyonse ya zipangizo ziwiri. Kukwaniritsa mathamangitsidwe okwera, mwachitsanzo, kungafune zigawo zambiri ndi masinthidwe osiyanasiyana amtali kuti mukwaniritse kulumikizana.
Zotsatira za kuyesa kothandiza
Choyamba, ofufuzawo amakumbutsa kuti mumayendedwe amtundu wa ma radio frequency accelerators, mphamvu yanthawi yayitali ya mtengo wamagetsi wophatikizidwa pamitengo yamtengo wothamanga ndi chifukwa cha kusintha kwa gawo lamagetsi lomwe limakumana ndi ma electron osiyanasiyana mkati mwa mtengowo. pa nthawi zosiyanasiyana. Chifukwa chake, zitha kuyembekezera kuti minda yokhala ndi ma gradients apamwamba komanso mizati yokhala ndi nthawi yayitali idzatsogolera kufalikira kwamphamvu. Miyendo yobayidwa kwa nthawi yayitali imathanso kupangitsa kuti ikhale yokwera kwambiri zotulutsa*.
Emittance* - gawo danga wotanganidwa ndi inapita patsogolo mtengo wa particles mlandu.
Pankhani ya accelerator ya terahertz, nthawi yachisangalalo ndi pafupifupi 200 kufupikitsa. Chifukwa chake, nyonga* gawo lothandizira lidzakhala 10 nthawi zambiri.
Mphamvu yamagetsi * - chizindikiro cha malo amagetsi, chofanana ndi chiŵerengero cha mphamvu yomwe imagwiritsidwa ntchito pamtengo woyima womwe umayikidwa pa malo operekedwa m'munda mpaka kukula kwake.
Chifukwa chake, mu accelerator ya terahertz, ma gradients akumunda omwe ma elekitironi amakumana nawo amatha kukhala maulamuliro angapo apamwamba kuposa chida wamba. Kutalika kwa nthawi yomwe kupindika kwa gawo kumawonekera kudzakhala kochepa kwambiri. Izi zimachokera ku izi kuti nthawi yamtengo wapatali wa electron idzakhala ndi zotsatira zodziwika bwino.
Asayansi adaganiza zoyesa malingalirowa pochita. Kuti achite izi, adayambitsa matabwa a ma elekitironi a nthawi zosiyanasiyana, omwe ankayendetsedwa ndi kukakamiza pogwiritsa ntchito chipangizo choyamba cha STEAM (STEAM-buncher).
Chithunzi #3
Pankhani yomwe kompresa sinalumikizidwe ndi gwero lamagetsi, matabwa a ma elekitironi (55 keV) okhala ndi ~ 1 fC (femtocoulomb) adadutsa pafupifupi 300 mm kuchokera pamfuti ya elekitironi kupita ku chipangizo chothamangitsira (STEAM-linac). Ma elekitironi amatha kukula motengera mphamvu ya mlengalenga mpaka nthawi yopitilira 1000 fs (femtoseconds).
Panthawiyi, mtengo wa elekitironi unkatenga pafupifupi 60% ya theka la kutalika kwa gawo lothamanga pafupipafupi 1,7 ps, zomwe zimapangitsa kuti pakhale mphamvu yowonjezereka yamagetsi ndi nsonga ya 115 keV ndi theka la kugawa mphamvu. kuposa 60 keV (3).
Poyerekeza zotsatirazi ndi zomwe zimayembekezeredwa, momwe ma elekitironi amafalitsidwira kudzera mu chowonjezera chowonjezera chinafaniziridwa pamene ma elekitironi anali atasiya kulunzanitsa ndi (mwachitsanzo, osalumikizana ndi) nthawi yokwanira yojambulira. Kuwerengera kwa izi kunawonetsa kuti kuwonjezeka kwa mphamvu ya ma elekitironi kumadalira kwambiri nthawi ya jakisoni, mpaka ku subpicosecond time scale (3b). Ndiko kuti, ndi malo abwino kwambiri, ma elekitironi amakumana ndi theka lathunthu la ma radiation ya terahertz pagawo lililonse (3s).
Ngati ma elekitironi afika nthawi zosiyanasiyana, amathamanga pang'ono mu gawo loyamba, zomwe zimawapangitsa kuti atenge nthawi yaitali kuti adutse. Desynchronization imawonjezeka m'magawo otsatirawa, zomwe zimapangitsa kuchepa kosafunikira (3d).
Pofuna kuchepetsa zotsatira zoyipa za kukulitsa kwakanthawi kwa mtengo wa elekitironi, chipangizo choyamba cha STEAM chimagwira ntchito mopondereza. Kutalika kwa mtengo wa ma elekitironi pa linac kunakokedwa kufika pafupifupi ~ 350 fs (theka la m'lifupi) mwa kukonza mphamvu ya terahertz yoperekedwa ku kompresa ndikusintha linac kukhala hatch mode.4b).
Chithunzi #4
Kutalika kwa mtengo wocheperako kunakhazikitsidwa molingana ndi nthawi ya Photocathode UV pulse, yomwe inali ~ 600 fs. Mtunda wapakati pa kompresa ndi mzerewo unathandizanso kwambiri, zomwe zimachepetsa kuthamanga kwa mphamvu yokulirakulira. Pamodzi, izi zimathandizira kulondola kwa femtosecond mu gawo la jakisoni la gawo lothamangitsira.
Pa chithunzi 4 zitha kuwoneka kuti kufalikira kwamphamvu kwa mtengo woponderezedwa wa ma elekitironi pambuyo pa kuthamangitsidwa kokwanira mumzere wothamanga kumachepa ndi ~ nthawi zinayi poyerekeza ndi yosakanizidwa. Chifukwa cha mathamangitsidwe, mphamvu yamphamvu ya mtengo woponderezedwa imasunthidwa kupita ku mphamvu zapamwamba, mosiyana ndi mtengo wosakanizidwa. Pachimake cha sipekitiramu mphamvu pambuyo mathamangitsidwe pafupifupi 4 keV, ndi mkulu-mphamvu mchira kufika pafupifupi 115 keV.
Ziwerengerozi, malinga ndi mawu odzichepetsa a asayansi, ndi mbiri yatsopano yofulumira (isanafike mathamangitsidwe inali 70 keV) mumtundu wa terahertz.
Koma kuti muchepetse kufalikira kwa mphamvu (4), mtengo wocheperako uyenera kukwaniritsidwa.
Chithunzi #5
Pankhani ya mtengo wosakanizidwa woyambitsidwa, kudalira kofananira kwa kukula kwa mtengo pakali pano kumawonetsa kutulutsa kozungulira kopingasa komanso kolunjika: εx,n = 1.703 mm*mrad ndi εy,n = 1.491 mm*mrad (5).
Kuponderezana, kumapangitsanso kutuluka kwa mpweya wodutsa nthawi 6 kufika εx,n = 0,285 mm*mrad (yopingasa) ndi εy,n = 0,246 mm*mrad (moima).
Ndikofunikira kudziwa kuti kuchuluka kwa kuchepa kwa emittance ndi pafupifupi kuwirikiza kawiri kuposa kuchuluka kwa nthawi yochepetsera mtengo, womwe ndi muyeso wa kusagwirizana kwa mphamvu zolumikizirana ndi nthawi yomwe ma elekitironi amawona kuyang'ana kwakukulu ndi kufooketsa mphamvu ya maginito panthawi yothamanga (5b и 5s).
Pa chithunzi 5b Zitha kuwoneka kuti ma elekitironi omwe adayambitsidwa nthawi yabwino amakumana ndi theka lonse la mathamangitsidwe amagetsi. Koma ma elekitironi omwe amafika nthawi isanakwane kapena itatha nthawi yabwino samathamanga kwambiri komanso amatsika pang'ono. Ma elekitironi oterowo amatha kukhala ndi mphamvu zochepa.
Mkhalidwe wofananawo umawonedwa pamene uli ndi mphamvu ya maginito. Ma electron omwe amabayidwa pa nthawi yoyenera amakumana ndi ma symmetrical maginito abwino ndi oyipa. Ngati kuyambitsidwa kwa ma elekitironi kunachitika isanafike nthawi yoyenera, ndiye kuti panali minda yambiri yabwino komanso yocheperako. Ngati ma elekitironi ayambitsidwa mochedwa kuposa nthawi yoyenera, padzakhala zochepa zabwino ndi zoipa kwambiri (5s). Ndipo kupatuka koteroko kumapangitsa kuti ma elekitironi apatukire kumanzere, kumanja, mmwamba kapena pansi, kutengera malo ake ogwirizana ndi olamulira, zomwe zimatsogolera pakuwonjezeka kwamphamvu yodutsa molingana ndi kuyang'ana kapena kufooketsa mtengowo.
Kuti mudziwe zambiri za ma nuances a phunziroli, ndikupangira kuyang'ana и kwa iye.
Epilogue
Mwachidule, magwiridwe antchito a accelerator adzawonjezeka ngati nthawi ya mtengo wa electron yachepetsedwa. Mu ntchitoyi, kutalika kwa mtengo wotheka kunachepetsedwa ndi geometry yoyika. Koma, mwamalingaliro, kutalika kwa mtengo kumatha kufika kuchepera 100 fs.
Asayansi amaonanso kuti khalidwe la mtengowo likhoza kupitilizidwa bwino mwa kuchepetsa kutalika kwa zigawo ndikuwonjezera chiwerengero chawo. Komabe, njirayi ilibe mavuto, makamaka kuonjezera zovuta kupanga chipangizocho.
Ntchitoyi ndi gawo loyambirira la kafukufuku wozama komanso watsatanetsatane wa kamvekedwe kakang'ono ka liniya accelerator. Ngakhale kuti mtundu woyesedwa ukuwonetsa kale zotsatira zabwino kwambiri, zomwe zitha kutchedwa kuswa mbiri, pali ntchito yambiri yoti tichite.
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