Abstract: A blower in one aspect of the present disclosure includes: a housing including a first discharge port; a motor in the housing; a fan in the housing; an attachment fitting portion; and a motor drive circuit. The attachment fitting portion is configured to detachably attach, to the first discharge port, an attachment including a second discharge port. The motor drive circuit (i) delivers a designated power to the motor and (ii) performs a constant power control that maintains a magnitude of an electric power delivered to the motor at a magnitude of the designated power.

Abstract: A metasurface element includes a support body and a metasurface formed on a surface of the support body. The metasurface includes a metal pattern that is disposed to emit an electron in response to incidence of an electromagnetic wave, and a metal layer that contains an alkali metal and is formed on the metal pattern. The metal layer extends beyond the metal pattern to reach a region on the surface of the support body, the region being not formed with the metal pattern.

Abstract: In an electron tube, the meta-surface emits an electron in response to an incidence of the electromagnetic wave. The first and second electrodes are spaced away from each other, and apply potentials different from each other to the meta-surface. A holder is disposed in the housing and holds the electron emitter. A first conductive line of the meta-surface is electrically connected to the first electrode. A second conductive line of the meta-surface is spaced away from the first conductive line, and is electrically connected to the second electrode. The first conductive line extends from the first electrode to the second conductive line. The second conductive line extends from the second electrode to the first conductive line.

Abstract: 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.