Ionizer for gas cluster ion beam formation

A neutral beam ionizing apparatus for electron impact ionization of a substantially cylindrical neutral beam, having a beam axis, said ionizing apparatus comprising:

• at least one electron source comprising a pair of co-focal elliptically cylindrical electrodes biased so as to cause electrons emitted from said at least one electron source to orbit repeatedly through the beam axis of the substantially cylindrical neutral beam;
• and
• an elliptically cylindrical ionizing region,
• wherein the beam axis lies substantially along a first focus of the elliptical cylinder and the electron source lies along a second focus of the co-focal elliptically cylindrical electrodes.

A neutral beam ionizing apparatus for electron impact ionization of a substantially cylindrical neutral beam, having a beam axis, said ionizing apparatus comprising:

• at least one electron source comprising a pair of co-focal elliptically cylindrical electrodes biased so as to cause electrons emitted from said at least one electron source to orbit repeatedly through the beam axis of the substantially cylindrical neutral beam;
• and
• an elliptically cylindrical ionizing region,
• wherein the neutral beam axis lies substantially along the first focus of said co-focal elliptically cylindrical electrodes, and wherein the at least one electron source is disposed to lie outside of the elliptical cylinder and to direct at least one beam of electrons through a focus of said co-focal elliptically cylindrical electrodes.