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To investigate the possibility of guiding a fast, heavy-ion beam with tilted curved surfaces, we study the transmission properties of a 4 MeV C+-ion beam passing through a narrow gap between a convex glass lens and concave glass lens. The ion-beam transmission of 42–59% obtained at the tilt angle θ= 3° is 20–30 times greater than that of 2% estimated from the cross section of the narrow gap between the two cylindrical lenses. The results of laser-beam-transmission experiments indicate that, even at θ= 3.4° where almost no ions pass through the gap without interacting with the cylindrical glass surfaces, approximately 10% of the ions are transmitted. The transmission probability is asymmetric with respect to the polarity of θ, indicating that the ion beam impinging on the concave surface is more easily transmitted than when impinging on the convex surface. Furthermore, no significant ion-energy loss occurs upon transmission for the angular range -3≤θ≤+ 3.4°. These results provide evidence that fast heavy-ion beams are guided by curved surfaces.

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