BABBAN TANKIN RUWA YA KAMA TASHOSHIN NUKILIYA DA KE KILOMITA 146

Injinan nukiliya masana’antu ne na antineutrino na electron. A cikin makamashin, ɓangarorin rarrabuwar zarra (fission) suna fuskantar ruɓewar beta: neutron a cikin tsakiyar zarra ya koma proton, electron da antineutrino. A haƙiƙa injinan nukiliya ne tushen neutrino na farko da aka taɓa ganowa, a gwajin Cowan–Reines na 1956. Tun daga lokacin, sun taimaka wajen auna yadda neutrino ke sauyawa (oscillate) — suna canza nau’i yayin da suke tafiya.

Haɗin gwiwar Super-Kamiokande, kimanin masana kimiyyar lissafi 250 daga Japan, Amurka, Turai, Koriya, China, Kanada da wasu wurare, yanzu ta ba da rahoton cewa na’urarta ma tana ganinsu.

Tankin da aka gina don babban farauta

Super-Kamiokande na’urar gano abubuwa ce ta ruwa mai kiloton 50, mita 1,000 a ƙarƙashin ƙasa a mahaƙar Kamioka a Japan. Cikinta yana ɗauke da tan 32,000 na ruwa da na’urorin gano haske 11,129 ke kallo, kowanne faɗinsa inci 20. Ƙwaya mai caji mai sauri da ke ratsa ruwan tana fitar da wani ɗan mazugin haske mara ƙarfi, hasken Cherenkov, wanda daga gare shi za a iya sake gano wurinta, alkiblarta da kuzarinta.

Sai dai antineutrino daga injinan nukiliya suna ɗauke da ’yan miliyoyin electronvolt kawai. A wannan ƙaramin kuzari, walƙiya guda ɗaya tana ɓacewa cikin sauƙi a cikin tururin zarra na halitta (radioactivity) da tarkacen hasken sararin samaniya.

Ɗan tsunkulen gadolinium

Dabarar ita ce alama mai bugu biyu. Lokacin da antineutrino ya bugi proton a cikin ruwan, yana samar da positron, wanda ke walƙiya nan take, da neutron, wanda ke yawo, ya rage gudu kuma a ƙarshe wata tsakiyar zarra ta kama shi. Idan hydrogen ne ya kama neutron ɗin, yana fitar da hasken gamma guda ɗaya na 2.2 MeV, mai wuyar gani. Idan gadolinium ne ya kama shi, yana fitar da jerin hasken gamma da jimillarsu ta kai kusan 8 MeV, mai sauƙin gani.

Don haka a watan Yuli 2020, an narkar da tan 13 na gadolinium sulfate a cikin ruwan (0.011% bisa nauyi); a watan Yuni 2022, an ƙara tan 27 (0.033%). Kusan rabin neutron, sannan kusan kashi uku cikin huɗu, yanzu gadolinium ne ke kama su, cikin kusan microsecond 120 sannan 60. Wani mai kunnawa na manhaja mai sauri yana kama electron har zuwa kusan 2.5 MeV da inganci kusan 100%.

Sauraron Tekun Wakasa

Tashoshin wuta da dama suna kusan kilomita 200 daga na’urar, galibi a Japan, da ɗan gudunmawa daga Koriya. Mafi kusa masu aiki suna a Tekun Wakasa: Mihama 3 (kilomita 146), Ohi 3 da 4 (kilomita 179) da Takahama 1 zuwa 4 (kilomita 191). Tsakanin 2020 da 2023, da yawa daga cikinsu suna aiki ko ana sake kunna su. An lissafa kwararar da ake tsammani wata-wata daga nauyin aikin da kowane inji ya bayar da rahoto, ta amfani da rumbun bayanan injinan nukiliya na Hukumar Makamashin Nukiliya ta Duniya.

Hayaniyar baya tana fitowa daga geoneutrino — antineutrino daga tururin zarra na Duniya kanta —, daga haɗuwar ba-zata, da kuma daga tarkacen tururin zarra da muon na sararin samaniya ke bari. Don auna ta, ƙungiyar ta yi amfani da wata dama ta sa’a: a watan Nuwamba da Disamba 2020, manyan injinan Tekun Wakasa a kashe suke ko ana kashe su. Bayanan waɗannan watanni biyu kusan hayaniyar baya ce zalla.

Nazarin ya ƙunshi kwanaki 411.52 na lokacin aiki, daga Fabrairu 2021 zuwa Satumba 2023. Wani mai rarrabewa na koyon na’ura (machine learning) da yankewa bisa lokaci (ƙasa da microsecond 80) da nisa (ƙasa da mita 2) tsakanin walƙiyoyin biyu suna zaɓar ma’auratan da ake zato.

Siginar da ke bin injinan

Yawan abubuwan da ke faruwa a kowane wata yana bin aikin injinan kuma ya yi daidai da hasashen da ya haɗa da sauye-sauye. An ƙi duniyar da babu antineutrino daga injinan nukiliya da muhimmanci na kusan sigma 6: wannan shi ne karo na farko da aka ga antineutrino daga injinan nukiliya a Super-Kamiokande. Takardar ba ta ba da jimillar yawan abubuwan da aka zaɓa ba.

Daga yanayin kuzarin, ƙungiyar ta fitar da ma’aunan sauyawa biyu: sin²θ₁₂ = 0.500 ± 0.155 da Δm²₂₁ = (9.08 +0.55/−0.54) × 10⁻⁵ eV².

Neutrino da antineutrino, gefe da gefe

Super-Kamiokande tana kuma auna neutrino daga Rana, waɗanda abu ne (matter), ba kishiyar abu (antimatter) ba. Kwatanta su biyun gwaji ne na wata muhimmiyar daidaituwa ta kimiyyar lissafi, da ake kira CPT. Ƙimomin sun bambanta da kusan sigma 1.1 ga kusurwar da sigma 2.2 ga bambancin nauyi; gaba ɗaya, rukunonin bayanan biyu sun dace a matakin sigma 1.9 — babu wata alama mai muhimmanci a ƙididdiga ta bambanci. Idan aka haɗa su, suna ba da sin²θ₁₂ = 0.332 (+0.028/−0.026) da Δm²₂₁ = (8.94 +0.46/−0.47) × 10⁻⁵ eV².

Takardar farko, da aka aika wa Physical Review Letters, tana ɗauke da rashin daidaito guda ɗaya: an ba da gwajin dacewar a matsayin Δχ² = 7.25 a babban rubutun da 7.64 a ƙarin bayani, duka biyun an ambace su a matsayin sigma 1.9. Marubutan sun kammala cewa ruwan da aka sa wa gadolinium yana mayar da babban tankin Cherenkov zuwa na’urar ganowa mai aiki ga antineutrino masu ’yan miliyoyin electronvolt, mai yuwuwar amfani don ma’auni na gaba a wannan matakin kuzari.