Transmission properties of a 4-MeV C ion beam entering a narrow gap between two cylindrical glass surfaces

Motohashi, Kenji*; Saito, Yuichi; Miyawaki, Nobumasa; Matsuo, Yutaro*

The transmission properties of a 4-MeV C ion beam entering a narrow gap between a pair of convex and concave glass rods facing each other are investigated in order to inspect the possibility to guide the ion beam with the tilting curved gap. The curvature of both rods was R = 155.70 mm, the gap was 1.2 mm. The entire setup can be tilted around the z-axis passing through the center of the gap at the entrance side. The tilt angle was defined positive for clockwise rotation. The ion transmission of 42-59% obtained at a tilt angle = 3 was 20-30 times larger than the value of 2% estimated from the cross section of the narrow gap. About 10% of the ions transmitted even at = 3.4 in which almost no ions can pass through the gap without interacting with the cylindrical glass surfaces, according to the results of laser-transmission experiment. No significant loss in their initial energies was observed in the angular range of -3 +3.4. These results show an evidence of a guide effect of the carved gap to swift heavy ion beams.