Method and apparatus for continuously generating laser plasma X-rays by the use of a cryogenic target

A continuous X-ray generation method of continuously generating pulsed X-rays from plasma generated by converging and irradiating a repetitive-shot pulsed main laser beam having high peak power to a target, said method comprising the steps of:

• preparing a chemically inert cryogenic material having a gaseous phase at room temperature, a rotary element which has a surface excellent in heat conductivity, which is rotatable in a vacuum chamber, and which serves as a target substrate for the main laser beam, and an auxiliary pulsed laser beam separate from the main laser beam;
• supplying a cryogenic fluid to said rotary element to cool at least a part of the surface of said rotary element to a temperature not higher than the liquefaction point of said cryogenic material;
• supplying said cryogenic material in a gaseous phase to the surface of said rotary element being cooled to form a cryogenic target layer of a predetermined thickness from said cryogenic material converted into at least one of a liquid phase and a solid phase;
• continuously generating pulsed X-rays from plasma produced by converging and irradiating the repetitive-shot pulsed main laser beam having high peak power onto said cryogenic target layer as said target, and;
• irradiating the auxiliary laser beam to fine particle debris of said cryogenic target layer which are ejected from the converging irradiation spot after dissipation of the plasma, thereby heating the fine particle debris to vaporize and eliminate the fine particle debris.

A continuous X-ray generation apparatus for continuously generating pulsed X-rays from plasma generated by converging and irradiating a repetitive-shot pulsed main laser beam having high peak power onto a target which is made of a chemically inert cryogenic material having a gaseous phase at room temperature, said apparatus comprising:

• main laser beam generating means for generating the pulsed main laser beam;
• a rotary element having a surface excellent in heat conductivity, rotatable within a vacuum chamber, and used as a target substrate for the main laser beam;
• a rotation drive mechanism for driving a rotation shaft of said rotary element to rotate said rotary element;
• cooling means for supplying a cryogenic fluid to said rotary element to cool at least a part of the surface of said rotary element to a temperature not higher than the liquefaction point of said cryogenic material;
• a cryogenic material supply mechanism for supplying said cryogenic material to the cooled surface of said rotary element to cool said cryogenic material so that a cryogenic target layer having a predetermined thickness is formed from said cryogenic material in at least one of a liquid phase and a solid phase;
• main pulse laser irradiating means for converging and irradiating the generated main laser beam onto a predetermined converging irradiation spot of said cryogenic target layer to generate the plasma;
• and
• auxiliary laser beam supplying means for generating a pulsed auxiliary laser beam to heat and vaporize or gasify fine particle debris of said cryogenic material that is discharged from the surface of the converging irradiation spot of said cryogenic target layer.

A continuous X-ray generation apparatus for continuously generating pulsed X-rays from plasma generated by converging and irradiating a repetitive-shot pulsed main laser beam having high peak power onto a target which is made of a chemically inert cryogenic material having a gaseous phase at room temperature, said apparatus comprising:

• main laser beam generating means for generating the pulsed main laser beam;
• a rotary element having a surface excellent in heat conductivity, rotatable within a vacuum chamber, and used as a target substrate for the main laser beam;
• a rotation drive mechanism for driving a rotation shaft of said rotary element to rotate said rotary element and driving the reciprocal movement of a converging irradiation spot of said main laser beam on the surface of said rotary element;
• cooling means for supplying a cryogenic fluid to said rotary element to cool at least a part of the surface of said rotary element to a temperature not higher than the liquefaction point of said cryogenic material;
• a cryogenic material supply mechanism for supplying said cryogenic material to the cooled surface of said rotary element to cool said cryogenic material so that a cryogenic target layer having a predetermined thickness is formed from said cryogenic material in at least one of a liquid phase and a solid phase;
• and
• main pulse laser irradiating means for converging and irradiating the generated main laser beam onto a predetermined converging irradiation spot of said cryogenic target layer to generate the plasma.