Insulation structure and insulation method

An insulation method, comprising:

• applying a potential difference between a first electrode and a second electrode supporting the first electrode by an insulation member;
• extracting an ion beam from a plasma generating section by using the first electrode and the second electrode;
• and
• protecting a first part and a second part of the insulation member from contamination particles by using a first protection member and a second protection member, respectively, wherein
• the first part is connected to the first electrode and the second part is connected to the second electrode, and at least one of the first part and the second part is made of a machinable ceramic or a porous ceramic, the first part having a first circular end surface on a side of the first electrode, the second part having a second circular end surface on a side of the second electrode, the insulation member having a cylindrical side surface that connects the first end surface to the second end surface, the cylindrical side surface having a recess formed thereon and positioned between the first end surface and the second end surface,
• the first protection member is a first cover having a first cover end,
• the second protection member is a second cover comprising a second contact portion and a second stepped side wall, the second contact portion contacting the second part and sandwiched between the second part and the second electrode, the second stepped side wall extending from the second contact portion toward the first electrode to form a pathway of the contamination particles between the first cover and the second stepped side wall,
• the second stepped side wall has a thin wall portion, a thick wall portion, and a step of the stepped side wall formed between the thin wall portion and the thick wall portion, the thin wall portion surrounding the first cover end, the thick wall portion extending from an outer circumferential portion of the second contact portion to the thin wall portion and terminating at the step of the stepped side wall,
• an exit of the pathway is formed between the first cover end and the step, the exit opposed to the recess.

An insulation structure provided among a plurality of electrodes for extraction of an ion beam from a plasma generating section, the plurality of electrodes comprising a first electrode and a second electrode to which different potential from that of the first electrode is applied, the insulation structure comprising:

• an insulation member comprising a first part connected to the first electrode and a second part connected to the second electrode and configured to support the first electrode to the second electrode, the first part having a first circular end surface on a side of the first electrode, the second part having a second circular end surface on a side of the second electrode, the insulation member having a cylindrical side surface that connects the first end surface to the second end surface, the cylindrical side surface having a recess formed thereon and positioned between the first end surface and the second end surface;
• a first protection member surrounding at least a part of the first part to protect the first part from contamination particles;
• and
• a second protection member surrounding at least a part of the second part to protect the second part from contamination particles, wherein
• at least one of the first part and the second part is made of a machinable ceramic or a porous ceramic,
• the first circular end surface and the second circular end surface have a same diameter and the cylindrical side surface has the same diameter,
• the first protection member has a first tubular part surrounding the first part and the second protection member has a second tubular part surrounding the second part, a first inner diameter of the first tubular part being substantially equal to a second inner diameter of the second tubular part, such that a first gap width between the first tubular part and the first part is substantially equal to a second gap width between the second tubular part and the second part.