Astrophysicists in Germany and North America have published plans to build the world’s largest neutrino telescope on the sea floor off the coast of Canada. The Pacific Ocean Neutrino Experiment (P-ONE) is designed to snare very-high-energy neutrinos generated by extreme events from beyond our galaxy.
於德國及北美的天體物理學家們已經發布了，在加拿大海岸外，海底建造世界上最大微中子望遠鏡的計劃。該項太平洋微中子實驗(P-ONE)旨在捕捉，來自銀河系外極端事件，產生的超高能微中子。
Neutrino telescopes observe the Cerenkov radiation that is emitted when neutrinos passing through the Earth interact very occasionally with atomic nuclei resulting in the production of fast-moving secondary particles.
微中子望遠鏡進行觀測，當微中子通過地球時，極偶爾與原子核交互作用，從而產生快速移動之次級粒子，發出的切倫科夫輻射(是當帶電粒子(諸如電子)以大於介質中，光之相速度(介質中波的傳播速度)的速度通過介質時，發出的電磁輻射)。
Being uncharged and exceptionally inert, neutrinos can penetrate gas and dust as they travel through the universe, allowing astronomers in principle to identify the exceptionally energetic phenomena that generate them. Photons from such events, in contrast, are absorbed on their journey.
不帶電且異常惰性的微中子，當行進穿過宇宙時，能穿透氣體及塵埃。原則上，使天文學家們得以確認，產生它們之異常高能的事象。相較之下，來自此類事件的光子，在行進中被吸收掉。
The world’s largest neutrino telescope, known as IceCube, consists of dozens of strings of photomultiplier tubes suspended in holes drilled deep into the ice at the South Pole. Covering a volume of 1 km3, IceCube made history in 2013 when it reported intercepting the first extragalactic neutrinos.
被通稱為IceCube的世界最大微中子望遠鏡(位於南極洲的阿蒙森-斯科特南極觀測站)，由數十串懸吊於南極冰層深處，鑽出之孔中的光電倍增管組成。在2013年，當涵蓋1公里立方米體積的IceCube，報告攔截到第一批銀河外的微中子時，創造了歷史。
Four years later it then recorded an event that could be tied to a very distant, bright galactic nucleus known as a blazar, thanks to concurrent gamma-ray observations.
四年後，由於同時進行的伽瑪射線觀測，它另外記錄了一個，可能與一個被通稱為耀變體(是具有由以近乎光速行進之離子化物質組成之相對論性噴流的活躍星系核心)之非常遙遠、明亮的星系核心，被聯繫起來的事件。
According to P-ONE head, Elisa Resconi at the University of Munich, IceCube’s 2017 result strictly speaking only constitutes “evidence” for the blazar source. To really claim a discovery and pinpoint the origin of other cosmic neutrinos, she argues, requires the construction of additional neutrino observatories as well as the extension of IceCube.
根據P-ONE負責人，德國慕尼黑大學Elisa Resconi的說法，嚴格說來，IceCube於2017年的觀測結果，僅構成耀變體來源的“證據”。她認為，要真正斷言發現及確切找出，其他宇宙微中子的來源，除了擴展IceCube之外，也需要建造額外的微中子觀測站。
“We are now on the verge of opening up neutrino astronomy,” she says, “but if we base this process on just one telescope it could take a really long time, perhaps decades.”
她宣稱：「目前，她們處於開啟微中子天文學的邊緣。不過，倘若她們僅以一座望遠鏡的上述進程為基礎，可能需要很長的時間，或許數十年。」
P-ONE will consist of seven groups of 10 detector strings creating an instrument volume of about 3 km3. Being larger than IceCube, it will detect rarer, higher-energy neutrinos, and will be most sensitive at a few tens rather than a handful of teraelectronvolts.
P-ONE將由，形成一座體積大約3公里立方之儀器的七組10個探測器串組成。比IceCube更大，它能探測到更稀有、更高能量的微中子，且在幾十而不是少數幾兆電子伏特時，會是最敏感。
圖1. 七組10個探測器串組成的P-ONE (圖援用自原文)
It will also observe a different part of the sky, mainly capturing neutrinos from the southern hemisphere rather than the north. But there will be some overlap between the two, says Resconi, potentially allowing independent observations of the same event.
它也將觀測蒼穹的不同區域，主要捕捉來自南半球而不是北部的微中子。Resconi表示，不過兩者之間會有一些重疊，潛在上容許相同事件的獨立觀測。
The new facility will be located at a depth of about 2.6 km in the Cascadia Basin, some 200 km from the coast of British Columbia. As such, it will take advantage of pre-existing infrastructure – an 800 km-long loop of fibre-optic cable operated by the University of Victoria’s Ocean Networks Canada that supplies power and ferries data to and from existing sea-floor instruments.
該新設施將座落於卡斯卡迪亞盆地(離加拿大英屬哥倫比亞省海岸約200公里)大約2.6公里的深處。本身，它將利用現有的基礎架構。也就是，一條由加拿大維多利亞大學所屬海洋網絡所營運，為現有海底儀器提供，電力及來、回傳輸數據之800公里長的光纖纜線迴路。
Having already confirmed that this site has the necessary optical properties by sending down two initial strings of light emitters and sensors in 2018, the P-ONE collaboration are now planning to deploy a steel cable with additional detectors to investigate the site – including spectrometers, lidars and a muon detector.
藉由在2018年，沉降兩條初期的光發射體及感測器串。已經證實，此位置具有必要的光學屬性。目前，P-ONE的合作團隊正計劃部署一條，具有其他探測器的鋼纜，來調查研究，包括了光譜儀、雷射雷達及一個μ介子探測器的此位置。
The plan then, says Resconi, is to install the first part of the observatory – a ring containing seven 1 km-long strings – around the end of 2023. And if that succeeds, the researchers will then apply for the bulk of the $50–100m needed to complete the project, with personnel costs adding roughly $100m more.
Resconi表示，之後該項計劃將在2023年底左右，安裝該觀測台的第一部分，一個包含七條1公里長串的環。如果成功的話，研究人員將申請完成該項計劃所需的5千萬到1億美元的大部分，人員成本增加大約1億多美元。
Resconi hopes that the full observatory will be installed and taking data by the end of the decade. But she describes this timeline as “very ambitious”. In addition to delays caused by the ongoing COVID- 19 pandemic, she says it will be a challenge to ensure that the detectors work as planned – given the huge pressures and the presence of salt and sea creatures, which together make the seabed such a harsh environment.
Resconi期盼，這整個觀測台能在十年內安置完成，並獲取數據。不過，她記述此時間表是“非常雄心勃勃的”。除了持續之COVID-19大流行造成的延誤之外，也考慮到巨大壓力及鹽與海洋生物的存在，一起使海底環境如此惡劣。她表示，確保此些探測器如計劃般運作，會是一項挑戰。
Indeed, scientists had already planned on operating a cubic-kilometre scale neutrino telescope known as KM3NeT on the floor of the Mediterranean Sea back in 2014, which was delayed to 2020.
其實，科學家們早已計畫，在2014年，於地中海海底運作一座，被通稱為KM3NeT之千米立方級的微中子望遠鏡。這被延宕到2020年。
According to collaboration member Feifei Huang, just two of the 230 strings due to be installed off the coast of southern Italy are so far in place, while another site in French waters currently has six out of a planned 115 strings running – with completion not foreseen until 2026 and 2024 respectively.
根據合作團隊成員Feifei Huang的說法，到目前為止，由於在義大利南部海岸外，被安裝的230串中，僅兩串就緒。而法國水域的另一位置，計劃的115串中，目前只有6串運作中。因此，預計分別到2026年及2024年才能完成。
Resconi says that part of the problem with that project is a lack of specialist personnel, with the physicists essentially doing everything themselves – for example, their self-built junction boxes, which connect cables on the sea floor, having failed.
Resconi表示，那項計劃的部分問題是缺乏專業人員。由於，基本上這些物理學家們親自做每件事。譬如，他們自行建構，於海床上連接海底電纜的接合箱，結果失敗了。
She hopes that the experience acquired by Ocean Networks Canada will mean a similar fate can be avoided for P-ONE. With 30 or 40 people dedicated to laying cables in the ocean, she says that her team “can focus on the physics”.
她期盼，該由加拿大海洋網絡獲得的經驗，對P-ONE而言，將意味著能避免類似的命運。由於，30或40人致力於，在海洋中鋪設電纜。她說表示，其團隊“能專注於此些物理現象”。
原文網址：https://physicsworld.com/a/astronomers-plan-huge-neutrino-observatory-in-the-pacific-ocean/
翻譯：許東榮
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