Abstract:
The invention provides a position sensor (300) which comprises an optical system (305,306) configured to provide measurement radiation (304) to a substrate (307). The optical system is arranged to receive at least a portion of radiation (309) diffracted by a mark (308) provided on the substrate. A processor (313) is applied to derive at least one position-sensitive signal (312) from the received radiation. The measurement radiation comprises at least a first and a second selected radiation wavelength. The selection of the at least first and second radiation wavelengths is based on a position error swing-curve model.
Abstract:
A reluctance actuator assembly comprising a reluctance actuator, a flux sensor to measure a magnetic flux in a gap of the reluctance actuator, and a flux amplifier to drive an actuator coil of the reluctance actuator based on a flux set point and the flux measured by the flux sensor. A method comprising providing to the flux amplifier a flux setpoint, the flux setpoint comprising a time constant component and a sinusoidally varying component at an excitation frequency, measuring a force generated by the reluctance actuator in response to the flux setpoint, and calibrating the reluctance actuator assembly from the measured force.
Abstract:
A free electron laser FEL comprises an undulator 24 generating coherent EUV radiation receiving an upstream electron beam EB2 and emitting a downstream electron beam EB4 and at least an electron source 21a, 21b operable to produce an upstream electron beam EB1, EB2 comprising bunches of electrons. A beam path is configured to direct the upstream electron beam through: a linear accelerator system (LINAC) comprising at least a first and a second linear accelerators 22a, 22b, a bunch compressor 28b, and said undulator 24. The downstream electron beam EB3, EB4 that leaves the undulator 24 recirculates through the second linear accelerator 22b in parallel with the upstream electron beam with a phase such that the downstream beam is decelerated by the second linear accelerator 22b and then recirculates through the first linear accelerator 22a in parallel with the upstream electron beam with a phase such that the downstream beam is decelerated by the first linear accelerator 22a; and to direct the downstream beam to a beam dump 100. At least a first energy spreader 50a, 50b, 50c imparts a reversible change to the energy distribution of bunches of electrons and is located at a position in the beam path before the bunch compressor 28b and so that it is only passed through by the upstream electron beam EB1. A second energy spreader 50d reverses the change to the energy distribution of bunches of electrons imparted by the at least one first energy spreader 50a, 50b, 50c, the second energy spreader 50d being located at a position in the beam path before the undulator 24 and so that it is only passed through by the upstream electron beam EB2.
Abstract:
A photocathode comprises a substrate in which a cavity is formed and a film of material disposed on the substrate. The film of material comprises an electron emitting surface configured to emit electrons when illuminated by a beam of radiation. The electron emitting surface is on an opposite side of the film of material from the cavity.
Abstract:
A sensor includes two shear-mode piezoelectric transducers, wherein each piezoelectric transducer has a bottom surface and a top surface, wherein the top surfaces of the piezoelectric transducers are rigidly connected to each other, and wherein the bottom surfaces of the piezoelectric transducers are configured to be attached to an object to be measured.
Abstract:
An undulator for a free electron laser includes a pipe for an electron beam and one or more periodic magnetic structures extending axially along the pipe. Each periodic magnetic structure includes a plurality of magnets and a plurality of passive ferromagnetic elements, the plurality of magnets being arranged alternately with the plurality of passive ferromagnetic elements in a line extending in an axial direction. Each of the plurality of magnets is spatially separated from the pipe, and each of the passive ferromagnetic elements extends radially from an adjacent magnet towards the pipe. A spacer element may be provided between the magnets and the pipe to provide radiation shielding for the magnets and/or cooling for the pipe.
Abstract:
A reluctance actuator assembly comprising a reluctance actuator, a flux sensor to measure a magnetic flux in a gap of the reluctance actuator, and a flux amplifier to drive an actuator coil of the reluctance actuator based on a flux set point and the flux measured by the flux sensor. A method comprising providing to the flux amplifier a flux setpoint, the flux setpoint comprising a time constant component and a sinusoidally varying component at an excitation frequency, measuring a force generated by the reluctance actuator in response to the flux setpoint, and calibrating the reluctance actuator assembly from the measured force.
Abstract:
The invention provides a position sensor (300) which comprises an optical system (305, 306) configured to provide measurement radiation (304) to a substrate (307). The optical system is arranged to receive at least a portion of radiation (309) diffracted by a mark (308) provided on the substrate. A processor (313) is applied to derive at least one position-sensitive signal (312) from the received radiation. The measurement radiation comprises at least a first and a second selected radiation wavelength. The selection of the at least first and second radiation wavelengths is based on a position error swing-curve model.
Abstract:
A photocathode comprises a substrate in which a cavity is formed and a film of material disposed on the substrate. The film of material comprises an electron emitting surface configured to emit electrons when illuminated by a beam of radiation. The electron emitting surface is on an opposite side of the film of material from the cavity.
Abstract:
A sensor includes two shear-mode piezoelectric transducers, wherein each piezoelectric transducer has a bottom surface and a top surface, wherein the top surfaces of the piezoelectric transducers are rigidly connected to each other, and wherein the bottom surfaces of the piezoelectric transducers are configured to be attached to an object to be measured.