「超音速渦の窓」で大気と真空をつなぐための新技術－新しい運転モードが生み出す自己適応渦－

2026-08-27 理化学研究所,長岡技術科学大学

理化学研究所と長岡技術科学大学などの研究グループは、固体の仕切りを設けず、超音速ガス流の渦によって大気圧空間と真空空間を隔てる「超音速渦の窓」の新しい運転方法を開発した。従来は理想的な自由渦に近い流れを作ることが重視されていたが、本研究では逆に両側の圧力差を意図的に大きくすることで、ガスジェット自身が流れの形を変えて圧力差に適応する性質を利用した。その結果、直径15mmの開口を維持したまま、最大約200倍の圧力比を実証。低いガス供給圧力・少ない流量でも高い圧力分離性能を得られ、ガスの回収・循環利用も可能となる。さらに、2段直列化すれば理論上約4,550倍の圧力比が期待される。RIBFの荷電変換リング用ガスストリッパーの小型化をはじめ、半導体製造、EUVリソグラフィー、表面処理、分析・計測、宇宙機器など、真空と外部空間を開口状態で接続する技術への応用が期待される。

超音速渦の窓（左）と超音速渦の窓を重ねて大気と真空を直接つなぐ概念図（右）

＜関連情報＞

乱れた自由渦空力窓による高圧比真空シール
High-pressure-ratio vacuum sealing by a perturbed free-vortex aerodynamic window

Hiroshi Imao;Kazumasa Takahashi;Yasuto Miyake;Kazuyuki Oyamada;Hiroki Okuno;Kazuhiko Horioka
Review of Scientific Instruments Published:August 06 2026
DOI:https://doi.org/10.1063/5.0336979

In this study, we investigated a perturbed free-vortex operating concept for enhancing the sealing pressure ratio p_high/p_low of a free-vortex aerodynamic window by intentionally shifting the flow away from the conventional matched free-vortex condition. A compact free-vortex aerodynamic-window assembly with a 15-mm-diameter open beam passage was designed, fabricated, and tested using air under low-gas-flow-rate conditions while keeping the supply-plenum pressure below atmospheric pressure. Under the conventional matched condition, the pressure ratio was limited to about 5 at p_high = 9.1 kPa, whereas perturbed free-vortex operation increased it to about 70 and, in a lower-flow configuration with stronger low-pressure-side evacuation, to about 200. The obtained pressure ratios, the response to diffuser-geometry changes, and the internal pressure distributions showed good agreement with computational fluid dynamics simulations, suggesting that the performance enhancement was accompanied by reorganization of the internal flow structure. Measurements with Ar and He and a design-map evaluation of two free-vortex aerodynamic windows connected in series further indicated the extendability of the concept to other gases and multistage configurations, with an estimated overall pressure ratio of about 4550 for the two-stage configuration. These results show that, in a low-gas-flow-rate regime while keeping the supply-plenum pressure below atmospheric pressure, perturbed free-vortex operation can realize a high sealing pressure ratio that cannot be obtained under the conventional matched condition. This approach is promising for accelerator gas targets, gas strippers, and other high-pressure-ratio vacuum-sealing applications.