An electron tube module includes an electron tube and a casing. The electron tube includes a vacuum container with a light transmitting substrate, a photocathode provided in an inner surface of the light transmitting substrate, an anode, and a prism. The prism includes a first surface bonded to an outer surface of the light transmitting substrate, a second surface inclined with respect to the first surface, and a third surface which further reflects light incident to the photocathode through the prism and the light transmitting substrate and reflected at an interface between the photocathode and a vacuum space so that the light is incident to the photocathode again. The casing includes a ceiling wall provided with an opening. The second surface is parallel to the ceiling wall. At least a part of the second surface is exposed to outside through the opening.

A novel photocathode employing a conduction band barrier is described. Incorporation of a barrier optimizes a trade-off between photoelectron transport efficiency and photoelectron escape probability. The barrier energy is designed to achieve a net increase in photocathode sensitivity over a specific operational temperature range.

A novel photocathode employing a conduction band barrier is described. Incorporation of a barrier optimizes a trade-off between photoelectron transport efficiency and photoelectron escape probability. The barrier energy is designed to achieve a net increase in photocathode sensitivity over a specific operational temperature range.

A method of patterning lithographic substrates, the method comprising using a free electron laser to generate EUV radiation and delivering the EUV radiation to a lithographic apparatus which projects the EUV radiation onto lithographic substrates, wherein the method further comprises reducing fluctuations in the power of EUV radiation delivered to the lithographic substrates by using a feedback-based control loop to monitor the free electron laser and adjust operation of the free electron laser accordingly.

A novel photocathode employing a conduction band barrier is described. Incorporation of a barrier optimizes a trade-off between photoelectron transport efficiency and photoelectron escape probability. The barrier energy is designed to achieve a net increase in photocathode sensitivity over a specific operational temperature range.

A novel photocathode employing a conduction band barrier is described. Incorporation of a barrier optimizes a trade-off between photoelectron transport efficiency and photoelectron escape probability. The barrier energy is designed to achieve a net increase in photocathode sensitivity over a specific operational temperature range.

An electron tube includes a housing that is internally held in a vacuum and has a window transmitting an electromagnetic wave, an electron emitting unit that is disposed in the housing and has a meta-surface emitting electrons in response to incidence of the electromagnetic wave, an electron multiplying unit that is disposed in the housing and multiplies the electrons emitted from the electron emitting unit, and an electron collecting unit that is disposed in the housing and collects the electrons multiplied by the electron multiplying unit. The window contains at least one selected from quartz, silicon, germanium, sapphire, zinc selenide, zinc sulfide, magnesium fluoride, lithium fluoride, barium fluoride, calcium fluoride, magnesium oxide, and calcium carbonate.

An electron tube includes a housing that is internally held in a vacuum and has a window transmitting an electromagnetic wave, an electron emitting unit that is disposed in the housing and has a meta-surface emitting electrons in response to incidence of the electromagnetic wave, an electron multiplying unit that is disposed in the housing and multiplies the electrons emitted from the electron emitting unit, and an electron collecting unit that is disposed in the housing and collects the electrons multiplied by the electron multiplying unit. The window contains at least one selected from quartz, silicon, germanium, sapphire, zinc selenide, zinc sulfide, magnesium fluoride, lithium fluoride, barium fluoride, calcium fluoride, magnesium oxide, and calcium carbonate.