An end-Hall ion-source apparatus comprising: a) an ion generating means comprising: (i) a discharge region having a first end, a second end, and a side, wherein said first end is open; (ii) an electron emitting means located outside of said discharge region; (iii) an anode which encloses said discharge region at said side,- (iv) a reflector, which encloses said discharge region at said second end; (v) means for introducing an ionizable working gas into said discharge region; b) magnetic-circuit means comprising: (i) a magnetically permeable internal pole piece located outside of said second end of said discharge region and near said reflector; (ii) a magnetically permeable and thermally conductive external pole piece located around said first end of said discharge region and between said anode and said electron emitting means; (iii) a magnetically permeable path between said internal pole piece and said external pole piece; (iv) a magnetic- field generating means located in said magnetically permeable path; characterized by (c) a cooling means comprising a thermally conductive cup (720, 820) having a closed end, a side wall, an open end, and internal passages through which fluid can flow; wherein said cup encloses said anode and said reflector without being in physical or electrical contact with either said anode or said reflector; wherein said closed end is located between said reflector and said internal pole piece; wherein said cup and said external pole piece are in physical contact with each other; and wherein at least one of said cup and said external pole piece is comprised of a material with a low microhardness at the joint and wherein said low microhardness means having a maximum value of Vickers microhardness, corresponding to an indentation depth of about 1μm, of about 1 Gpa or less; and (d) assembly means holding said cup against said external pole piece. a) an ion generating means comprising: (i) a discharge region having a first end, a second end, and a side, wherein said first end is open; (ii) an electron emitting means located outside of said discharge region; (iii) an anode which encloses said discharge region at said side,- (iv) a reflector, which encloses said discharge region at said second end; (v) means for introducing an ionizable working gas into said discharge region; b) magnetic-circuit means comprising: (i) a magnetically permeable internal pole piece located outside of said second end of said discharge region and near said reflector; (ii) a magnetically permeable and thermally conductive external pole piece located around said first end of said discharge region and between said anode and said electron emitting means; (iii) a magnetically permeable path between said internal pole piece and said external pole piece; (iv) a magnetic- field generating means located in said magnetically permeable path; characterized by (i) a discharge region having a first end, a second end, and a side, wherein said first end is open; (ii) an electron emitting means located outside of said discharge region; (iii) an anode which encloses said discharge region at said side,- (iv) a reflector, which encloses said discharge region at said second end; (v) means for introducing an ionizable working gas into said discharge region; b) magnetic-circuit means comprising: (i) a magnetically permeable internal pole piece located outside of said second end of said discharge region and near said reflector; (ii) a magnetically permeable and thermally conductive external pole piece located around said first end of said discharge region and between said anode and said electron emitting means; (iii) a magnetically permeable path between said internal pole piece and said external pole piece; (iv) a magnetic- field generating means located in said magnetically permeable path; characterized by (i) a magnetically permeable internal pole piece located outside of said second end of said discharge region and near said reflector; (ii) a magnetically permeable and thermally conductive external pole piece located around said first end of said discharge region and between said anode and said electron emitting means; (iii) a magnetically permeable path between said internal pole piece and said external pole piece; (iv) a magnetic- field generating means located in said magnetically permeable path; characterized by (c) a cooling means comprising a thermally conductive cup (720, 820) having a closed end, a side wall, an open end, and internal passages through which fluid can flow; wherein said cup encloses said anode and said reflector without being in physical or electrical contact with either said anode or said reflector; wherein said closed end is located between said reflector and said internal pole piece; wherein said cup and said external pole piece are in physical contact with each other; and wherein at least one of said cup and said external pole piece is comprised of a material with a low microhardness at the joint and wherein said low microhardness means having a maximum value of Vickers microhardness, corresponding to an indentation depth of about 1μm, of about 1 Gpa or less; and (d) assembly means holding said cup against said external pole piece.