There are two main designs on the table today – circular and linear. The motivation for linear colliders is due to the problem of sending electrons and positrons round in a circle – they radiate photons. So as you go to higher energies in a circular collider, electrons and positrons radiate that energy away in the form of synchrotron radiation.

Meanwhile, the American Particle Physics Project Prioritization Panel (P5) chose to support upgrades at CERN over building a separate Higgs factory. There are also plans to build an International Linear Collider (ILC) in Japan.

There is also a clearer view of the international landscape. In December 2023 the US “P5” prioritisation process stated that the US would support a Higgs factory in the form of an FCC-ee at CERN or an International Linear Collider (ILC) in Japan, while also exploring the feasibility of a high-energy muon collider at Fermilab

文部科学省が２９日公表した２０２５年度予算の概算要求で、国際リニアコライダー（ILC）関連は２４年度当初予算と同額の１０億５千万円が計上された。将来加速器の性能向上に向けた重要要素技術開発事業費として、２４年度と同額の７億円を盛り込んだ。ILCテクノロジーネットワークの国際的な協力枠組みを活用して取り組みを推進する。(In the budget estimate for FY2025 announced by the Ministry of Education, Culture, Sports, Science and Technology on November 29, 1.05 billion yen has been allocated for the ILC. This amount matches the initial budget for FY24. The project aims to advance efforts through the international cooperation framework of the ILC Technology Network.)

The head of the P5 panel, theorist Hitoshi Murayama, calls the ILC “shovel-ready and technologically mature.” But to move forward with construction, scientists still need to gain the approval of the Japanese Ministry of Education, Culture, Sports, Science and Technology, something they’ve been working on for a little over a decade.

宙誕生の謎を探る次世代大型加速器について、欧州合同原子核研究所（CERN）のマキシム・ティトフ研究員が共同通信の取材に応じた。岩手・宮城両県の北上山地が候補地に挙がる国際リニアコライダー（ILC）を、技術面の準備や費用の国際分担を踏まえ「現実的で手が届く計画だ」と評価。日本政府は実現に向けて議論を先導すべきだと強調した。(Maxim Titov, a researcher at the European Laboratory for Nuclear Research (CERN), gave an interview to Kyodo News regarding the next generation of large accelerators that will probe the mysteries of the birth of space. He praised the International Linear Collider (ILC), for which the Kitakami Mountains in Iwate and Miyagi prefectures are a candidate site, as a ‘realistic and affordable plan’, based on technical preparations and the international sharing of costs. He stressed that the Japanese Government should lead discussions towards its realisation.)

東京大で開かれた国際学会リニアコライダー・ワークショップ（ＬＣＷＳ、８～１１日）について、山本均・東北大名誉教授（６９）＝素粒子実験＝は「世界の研究者に国際リニアコライダー（ＩＬＣ）の優位性を印象づけた」と総括した。欧州や中国で進められる大型円形加速器計画とＩＬＣが本格的に比較された初めての機会だとして「日本政府が誘致に向けて踏み出すなら今しかない」と強調した。東京都内で岩手日報社の取材に答えた。(The International Conference Linear Collider Workshop (LCWS) held at the University of Tokyo (8-11 August) was summed up by Hitoshi Yamamoto, 69, Professor Emeritus of Particle Physics at Tohoku University, who said that the workshop ‘impressed researchers around the world with the superiority of the International Linear Collider (ILC)’. He stressed that this was the first time that the ILC had been compared in earnest with the large circular accelerator programmes underway in Europe and China, and that ‘now is the time for the Japanese Government to step forward to invite the ILC’. He gave an interview to The Iwate Nippo in Tokyo.)

宇宙誕生の謎を探る次世代大型加速器に関する米政府諮問委員長を務める、村山斉・米カリフォルニア大バークリー校教授は1日、盛岡市内で講演し、日本に国際リニアコライダー（ILC）ができるとはっきりすれば「米国は必ず乗ってくる」と述べ、米側の協力が期待できると強調した。(Professor Hitoshi Murayama of the University of California, Berkley, who chairs the US government’s advisory committee on the next-generation large accelerator that will probe the mysteries of the birth of the universe, gave a speech in Morioka City on 1 January, saying that if it is clear that Japan will build the International Linear Collider (ILC), ‘the US will definitely come on board’ and stressing that US cooperation is expected. The ILC will be a major project in the future.)

国際学会リニアコライダー・ワークショップ（ＬＣＷＳ）を開催している東京大で９日、同大名誉教授で国際リニアコライダー（ＩＬＣ）を推進する中心メンバーだった故駒宮幸男さんの追悼セッションが行われた。(On 9 September, a memorial session was held at the University of Tokyo, which is hosting the International Conference Linear Collider Workshop (LCWS), for the late Yukio Komamiya, a professor emeritus at the University and a key member in promoting the International Linear Collider (ILC)

国際学会リニアコライダー・ワークショップ（ＬＣＷＳ）は８日、東京大で開幕した。国内開催は２０１９年の仙台市以来５年ぶりで、１１日までの４日間。岩手県が建設候補地とされる国際リニアコライダー（ＩＬＣ）の準備状況や科学的意義について研究者が共有する。欧州や中国でも建設が計画されている大型加速器の最新動向も示された。(The International Conference Linear Collider Workshop (LCWS) opened at the University of Tokyo on 8 August. It is the first time in five years that the conference has been held in Japan since Sendai in 2019, and will last for four days until 11 November. Researchers will share information on the preparation status and scientific significance of the International Linear Collider (ILC), for which Iwate Prefecture is considered a candidate construction site. The latest developments on large accelerators, which are also planned for construction in Europe and China, were also presented.)

宇宙誕生の謎を探る次世代大型加速器に関する米政府諮問委員長を務める、村山斉・米カリフォルニア大バークリー校教授は1日、盛岡市内で講演し、日本に国際リニアコライダー（ILC）ができるとはっきりすれば「米国は必ず乗ってくる」と述べ、誘致すれば米側の協力が期待できると強調した。(Professor Hitoshi Murayama of the University of California, Berkley, who chairs the US government’s advisory committee on the next-generation large accelerator that will probe the mysteries of the birth of the universe, gave a speech in Morioka City on 1 January, saying that if it is clear that Japan will host the International Linear Collider (ILC), ‘the US will definitely come on board’ and stressed that if Japan invites the ILC, cooperation from the US can be expected. He stressed that if Japan invites the ILC to Japan, the cooperation of the US side can be expected.)