Variable rotating capacitor for synchrocyclotron

A synchrocyclotron 1 comprising an RF system (2,3,4) for accelerating charged particles in the synchrocyclotron, said RF system comprising a transmission line (3), a dee (2) and a variable rotating capacitor or RotCo (5), wherein the RotCo (5) is adapted to be connected via the transmission line (3) to the dee (2) of the synchrocyclotron (1) and is adapted to modify a resonant frequency of the synchrocyclotron as a function of time, said RotCo comprising:

• a rotor (10) having a rotation axis (Z) and having a plurality of circumferentially-distributed rotor electrodes (11) extending parallel to the rotation axis (Z);
• and
• a stator (20), coaxial with the rotor (10), and having a plurality of circumferentially-distributed stator electrodes (21) extended parallel to the rotation axis (Z), each rotor electrode (11) being adapted to face at least one stator electrode (21) during rotation of the rotor (10) in order to form a capacitor, wherein each stator electrode (21) consists of a single metal plate (21) and wherein all the stator electrodes (21) are distributed on a same stator circumference (25) centered on the rotation axis (Z),
• wherein the rotor electrodes comprise a first group of rotor electrodes (11-1) distributed over a first rotor circumference (80) and a second group of rotor electrodes (11-2) distributed over a second rotor circumference (90), wherein a radius (R1) of the stator circumference (25) is between a radius (R2) of the first rotor circumference (80) and a radius (R3) of the second rotor circumference (90), wherein the first group of rotor electrodes (11-1) comprises the same number of electrodes as the second group of rotor electrodes (11-2), wherein the electrodes of the first group (11-1) are arranged opposite the electrodes of the second group (11-2) respectively and wherein the first and second groups of rotor electrodes form a single electromechanical assembly.

A synchrocyclotron 1 comprising an RF system (2,3,4) for accelerating charged particles in the synchrocyclotron, said RF system comprising a transmission line (3), a dee (2) and a variable rotating capacitor or RotCo (5), wherein the RotCo (5) is adapted to be connected via the transmission line (3) to the dee (2) of the synchrocyclotron (1) and is adapted to modify a resonant frequency of the synchrocyclotron as a function of time, said RotCo comprising:

• a rotor (10) having a rotation axis (Z) and having a plurality of circumferentially-distributed rotor electrodes (11) extending parallel to the rotation axis (Z);
• and
• a stator (20), coaxial with the rotor (10), and having a plurality of circumferentially-distributed stator electrodes (21) extending parallel to the rotation axis (Z), each rotor electrode (11) being adapted to face at least one stator electrode (21) during rotation of the rotor (10) in order to form a capacitor, wherein each stator electrode (21) consists of a single metal plate (21) and wherein all the stator electrodes (21) are distributed on a same stator circumference (25) centered on the rotation axis (Z), wherein each stator electrode (21) has a straight first flank (26) parallel to the rotation axis (Z) and a second flank (27) having a profile that varies such that the distance between the first flank and the second flank decreases along the direction of the rotation axis (Z) and over at least part of the length of said stator electrode (21).