HASKEN DA KE SA AGOGON NUKILIYA YA CI GABA DA AIKI

Agogunan haske (optical clocks) suna ba da madogaran mita masu daidaito ga kimiyyar aunawa da gwaje-gwajen kimiyyar lissafi na asali. Tsakiyar ƙwayar zarra ta thorium-229 tana ba da wani abu mafi ban mamaki: tsakiyarta tana da yanayi mai ɗan tashi kaɗan, kusan electronvolt 8.4 sama da yanayin ƙasa, wanda laser zai iya kaiwa. Agogo da aka gina bisa tsakiyar ƙwayar zarra zai kasance mai matuƙar jin yiwuwar sauye-sauye a cikin tsayayyun ƙimomin asali na halitta. Kuma da thorium a cikin lu’ulu’u mai haske, zai iya zama agogon nukiliya mai ƙarfi (solid-state nuclear clock).

Matsalar ita ce launi. Wannan sauyi yana buƙatar haske a nanomita 148.4, a cikin ultraviolet na sararin wofi (vacuum ultraviolet). Ayyukan baya-bayan nan sun nuna cewa irin wannan haske na iya tada tsakiyar ƙwayar zarra kuma ya gudanar da agogunan nukiliya. Don karanta ɗan shanyewa mai rauni, duk da haka, dole tushen ya isar da kwararar photons tsayayye na sa’o’i, kuma dole a tace sauye-sauyen ƙarfinsa.

Rikicin muradi. Wasu marubuta ma’aikata ne ko masu Shanghai Precilasers Technology, wani kamfanin laser. Marubutan sun bayyana cewa ba su da wani rikicin muradi.

Raba tsawon zango sau uku

Ƙungiyar, daga Jami’ar Kimiyya da Fasaha ta Sin, Dakin Gwaje-gwaje na Ƙasa na Hefei, cibiyoyin Kwalejin Kimiyya ta Sin da kamfanin, ta fara daga laser na infrared mai ci gaba a nanomita 1,187. Matakai uku na ninka mita (frequency doubling) a jere suna raba tsawon zangonsa: 594, sannan 297, sannan nanomita 148.4.

Mataki na ƙarshe yana faruwa a cikin lu’ulu’u na strontium tetraborate, wani abu mai haske a cikin vacuum ultraviolet wanda zai iya juya haske zuwa ninki biyu na mitarsa. Lu’ulu’un yana cikin akwati da aka rufe, aka zubar kuma aka sake cika da nitrogen mai tsabta fiye da 99.9999%, tunda oxygen yana hadiye wannan haske. Wannan siffa tana zama gwaji: a bar ɗan oxygen ya shiga sai alamar nanomita 148.4 ta ɓace, ta bar hayaniyar bango kawai.

’Yan nanowatt kaɗan, masu tsabta sosai

• Da milliwatt 920 na hasken nanomita 297 da ke shiga, tushen yana isar da kimanin nanowatt 8.1 a nanomita 148.4.
• Alamar ta fi ƙarfi sau 38,000 fiye da bangon da ya rage bayan ƙara oxygen.
• Wannan fitarwa kusan ninki shida ne na nanowatt 1.3 da wata ƙungiya ta baya ta ba da rahoto. Amma marubutan sun jaddada cewa an samu shi da ƙarfin tura haske (pump) mai yawa sosai; a kowane murabba’in watt, juyawar biyu kusan daidai suke, don haka ba a nuna cewa lu’ulu’un ya fi inganci ba.

Lu’ulu’u da aka yanke daga shinge ɗaya ba su yi hali iri ɗaya ba. Ɗaya ya fi aiki kusa da 30 °C, wani kusa da 45 da 48 °C dangane da inda hasken ya buga. Kowane yanki yana buƙatar daidaitawarsa ta kansa.

Sa’o’i talatin da uku, da dabara kan sauyawa

Tushen ya gudana na sa’o’i 33.3 yayin da ƙungiyar ke yin ma’aunin shanyewar nukiliya da aka bayyana a wata takarda abokiya. Fitarwarsa ta tashi a hankali daga kusan ƙididdiga miliyan 5 zuwa 8 a cikin daƙiƙa, yayin da tura hasken ya kasance tsayayye; dalilin wannan sauyawa har yanzu ba a warware shi ba.

Don shawo kan irin waɗannan sauye-sauye, ƙungiyar ta kwatanta kowace milidaƙiƙa ta alama da milidaƙiƙun da ke kafin ta da bayanta. A wani gudu na sa’o’i uku daban, wannan madogara ta wuri (local referencing) ta bar hayaniyar ta ragu kusan yadda ƙididdigar photons ta yarda, ta kai ga daidaito na kaso 3.5 × 10⁻⁵ bayan daƙiƙa 1,000. Marubutan sun gabatar da shi a matsayin gwaji na matsakaita a wajen layi, ba iyakar gano shanyewa da aka auna ba tukuna.

Zuwa tushe masu haske fiye da haka

Wani kogon madubai a kewaye da lu’ulu’u mafi sirara zai iya, a kan takarda, ya ɗaga fitarwa zuwa kusan microwatt 3.4 — hasashe da ke ɗaukar ƙananan asara da aiki tsayayye. Ƙara wasu sinadarai a lu’ulu’un (doping) ko sarrafa tsarinsa na ciki wasu hanyoyi ne. A yanzu, sakamakon tushe ne mai amfani, mai daɗewa yana aiki, don sauraron raunin shanyewar tsakiyar ƙwayar zarra ta thorium.