a duct through which charged particles pass;

a device configured to interact with charged particles that pass through the duct, the duct is configured to extend through the device;

a support configured to support the device with respect to a floor surface;

a joint configured to allow the duct to be inserted there through;

an annular seal configured to contact an outer peripheral surface of the duct;

a ring configured to allow the duct to be inserted there through; and

at least one nut configured to allow the duct to be inserted there through, wherein:

a male screw is engraved on an outer peripheral surface of the joint;

a contact surface to be in contact with the annular seal is formed at an end of an inner peripheral surface of the joint, the contact surface enlarges the inner peripheral surface of the joint to the extent that an outer circumference of the ring is engaged therewith, and a surface with which the annular seal is brought into close contact is formed in a tapered shape;

a pressing surface for pressing the annular seal toward the contact surface of the joint is formed on the ring and the pressing surface is formed in a tapered shape;

an abutting surface that abuts on the ring is formed on the nut; and

a female screw to be screwed to the male screw, the female screw is engraved on an inner peripheral surface of the nut,

wherein a first clearance formed by the duct and the joint and a second clearance formed by the duct and the nut allow the duct to tilt with respect to the joint,

wherein the device is one of a bending electromagnet, a quadrupole electromagnet, and a screen monitor, and

wherein end faces of each of the joint and the ring are formed in the tapered shape, so that the annular seal is brought into abutting contact to form a V-shape.