ATTOSECOND 100, TERAWATT 10

Attosecond ɗaya shi ne kashi ɗaya cikin biliyan na kashi ɗaya cikin biliyan na daƙiƙa. Bugun haske mai gajarta haka yana ba da damar ganin motsin electrons kai tsaye a cikin atoms, molecules da abubuwa masu ƙarfi, a ma’aunin lokacinsu na halitta — fannin da aka karrama da Kyautar Nobel ta Physics ta 2023. Na’urori ƙanana na kan tebur suna samar da bugun haske na attosecond, amma da ƙarancin makamashi, musamman a gajerun tsawon raƙuman haske. Wannan yana hana gwaje-gwajen “tuƙi mai ƙarfi”, inda haske ke tuƙa electrons da ƙarfi.

Laser na electrons masu ’yanci (free-electron lasers) sun shawo kan wannan iyaka. A cikin waɗannan na’urori, wani rafi na electrons da ke tafiya kusan da saurin haske yana ratsa dogon jerin maganadisu masu sauya alkibla, wato undulator. Ƙananan sauye-sauyen yawa a cikin rafin suna ƙara wa kansu ƙarfi har electrons su fitar da walƙiyar X-ray mai ƙarfi. Wasu cibiyoyi da dama irin waɗannan sun riga sun saba samar da bugun X-ray na attosecond, har zuwa ɗaruruwan microjoules.

Gajartar tari, gajartar walƙiya

Don samun walƙiya ta attosecond, tarin electrons da ke yin aikin laser shi kansa dole ya kasance gajere sosai. Evgeny Schneidmiller da abokan aikinsa 37 a DESY, European XFEL, TU Dortmund, da jami’o’in Hamburg da Kassel sun kai matuƙa a European XFEL, laser na X-ray mai superconducting da ke Schenefeld, a Jamus.

Tsarin European XFEL: matakan matsewa biyar da aka yi amfani da su a wannan aiki an zagaye su da kore. — Hoto na 1, Schneidmiller da abokan aiki (2026), arXiv:2609.31534.

Matsewa biyar maimakon uku

A aiki na yau da kullum, tarin electrons suna wucewa ta “chicanes” na maganadisu guda uku da ke gajarta su, kuma na ƙarshe yana matsewa rabi kawai da gangan. Ƙungiyar ta sauya komai:

• Chicane na uku yanzu yana matse wani tari mai ɗan nauyi na picocoulomb 350 gaba ɗaya.
• Wani sashen collimator, wanda a al’ada ba ya yin komai, ya zama mataki na huɗu: gudanar da rafin a 14.3 GeV, MeV 300 sama da makamashinsa na al’ada, yana kunna wani tasiri na mataki na biyu da ke ƙara matse shi.
• Lanƙwasar da ke tsakanin layukan undulator biyu ta zama mataki na biyar, ta hanyar karkatar da saitin wasu maganadisu biyu masu tattara rafi. Tarin ya riga ya samu yaɗuwar makamashi da ta dace yayin da yake ratsa wani undulator mai tsawon mita 200 a gaba.

Kwaikwayo sun nuna an matse tarin zuwa ƙasa da micrometre ɗaya, tare da ƙarfin wutar lantarki na ƙoli na ampere 150,000 — mai tsananin yawa ga laser na X-ray, ko da yake ba za a iya auna shi kai tsaye a wannan layin ba. Babban makamashin electrons ne mabuɗin: a 3–4 GeV da ake amfani da su don X-ray mai laushi a wasu wurare, yaɗuwar makamashin irin wannan tari za ta hana laser aiki, in ji marubutan.

Millijoules a cikin attosecond

Zagayen gwaje-gwaje uku, a 2025 da 2026, sun samar da walƙiyar X-ray a electronvolt 1,000 (tsawon raƙumi na kusan nanometre 1.2). Ya danganta da zagayen, kashi 20 zuwa 39% na bugun hasken sun nuna ƙoli guda ɗaya mai tsabta a cikin spectrum ɗinsu, tare da matsakaicin makamashi na millijoule 1.2 zuwa 2.0. Wasu bugun haske ɗaiɗai sun kai millijoule 3, tare da faɗin spectrum na eV 10 zuwa 30.

Ana ƙiyasta tsawon lokacin ne daga spectrum: bugun haske mai faɗin eV 18 yana daidai da kusan attosecond 100 a mafi kyawun yanayi. Idan aka zana faɗi a kan makamashi, kashi 57% na abubuwan masu ƙoli ɗaya suna sama da layin da ya yi daidai da ƙarfin ƙoli na terawatt 10 a ƙarƙashin wannan zato mai kyau, har ma kashi 6% a ƙarƙashin zato na rashin fata.

Kowane ɗigo bugun X-ray ne mai ƙoli ɗaya. Ɗigogin da ke saman layukan masu yanke-yanke suna daidai da ƙarfin ƙoli sama da terawatt 10. — Hoto na 4, Schneidmiller da abokan aiki (2026), arXiv:2609.31534.

Zaɓe ɗaya bayan ɗaya

Ba a auna tsawon lokacin kai tsaye a cikin lokaci ba: spectrum ba ya ba da damar ganin phase na haske, don haka ƙiyasin ya dogara ne a kan wani samfuri na yau da kullum da kuma ma’aunai na baya-bayan nan da ke nuna cewa irin waɗannan bugun haske suna kusa da mafi gajartar tsawon lokacin da za su iya kaiwa. Harbe-harbe kuma suna sauyawa sosai daga ɗaya zuwa na gaba. Amma European XFEL yana samar da har dubun dubatar bugun haske a kowace daƙiƙa, kuma ana iya rubuta makamashi da spectrum na kowane bugun haske ba tare da lalata shi ba. Masu amfani za su iya riƙe mafiya gajarta da ƙarfi kawai — sabon yanayi, in ji marubutan, don kallon electrons da aka tura zuwa iyakarsu.