Abstract: A FAIMS cell has an elongated inner electrode with a longitudinal axis extending along a first direction. The inner electrode has a curved outer surface that defines a circle when viewed in a cross section that is taken in a plane normal to the longitudinal axis, which itself passes through the center of the circle so defined. An outer electrode having an inner surface is disposed in a spaced-apart facing relationship relative to the outer surface of the inner electrode so as to define an analytical gap therebetween. A first ion inlet orifice is defined through a first portion of the outer electrode, and an ion outlet orifice is defined through a second portion of the outer electrode. In particular, the first ion inlet orifice has a first ion injection axis that does not pass through the center of the circle. Furthermore, the second electrode does not have defined through any portion thereof an ion inlet orifice having an ion injection axis that passes through the center of the circle.

Abstract: Systems and methods of the invention include a branched radio frequency multipole configured to act, for example, as an ion guide. The branched radio frequency multipole comprises multiple ion channels through which ions can be alternatively directed. The branched radio frequency multipole is configured to control which of the multiple ion channels ions are directed, through the application of appropriate potentials.

Abstract: A method for differential mobility separation of ions using digital-drive based high voltage fast switching electronics. The digital waveform delivered to the spectrometer is characterized by at least two substantially rectangular pulses of different amplitude and polarity. The control circuitry allows for waveform frequency, duty cycle and pulse amplitudes to be varied independently. Balanced as well as unbalanced asymmetric waveforms can be designed for optimum differential mobility separation of ions. The digital drive is designed for differential mobility spectrometers including parallel plate and segmented plate multipoles of planar symmetry, as well as multipoles of cylindrical symmetry, which may optionally be arranged in series. The use of the digital drive establishes alternating electric fields during which the displacement as a result of ion oscillation is determined by mobility coefficients.

Abstract: There is provided a method of arranging, as a composite charged-particle beam system, a gas ion beam apparatus, an FIB and an SEM in order to efficiently prepare a TEM sample. The composite charged-particle beam system includes an FIB lens-barrel 1, an SEM lens-barrel 2, a gas ion beam lens-barrel 3, and a rotary sample stage 9 having an eucentric tilt mechanism and a rotating shaft 10 orthogonal to an eucentric tilt axis 8. In the composite charged-particle beam system, an arrangement is made such that a focused ion beam 4, an electron beam 5 and a gas ion beam 6 intersect at a single point, an axis of the FIB lens-barrel 1 and an axis of the SEM lens barrel 2 are orthogonal to the eucentric tilt axis 8, respectively, and the axis of the FIB lens-barrel 1, an axis of the gas ion beam lens-barrel 3 and the eucentric tilt axis 8 are in one plane.

Abstract: An electron gun includes an electron source configured to emit electrons. The electron source includes an electron emission region configured to emit the electrons and an electron emission restrictive region configured to restrict emission of the electrons. The electron emission restrictive region is located on a side surface of the electron source except an electron emission surface on a tip of the electron source and is covered with a different material from the electron source. The electron gun emits thermal field-emitted electrons by applying an electric field to the tip while maintaining a sufficiently low temperature to avoid sublimation of a material of the electron source. The material of the electron source may be lanthanum hexaboride (LaB6) or cerium hexaboride (CeB6). The electron emission restrictive region may be covered with carbon.

Abstract: An electron beam system or a method for manufacturing a device using the electron beam system in which an electron beam can be irradiated at a high current density and a ratio of transmittance of a secondary electron beam of an image projecting optical system can be improved and which can be compact in size. The surface of the sample S is divided into plural stripe regions which in turn are divided into rectangle-shaped main fields. The main field is further divided into plural square-shaped subfields. The irradiation with the electron beams and the formation of a two-dimensional image are repeated in a unit of the subfields. A magnetic gap formed by the inner and outer magnetic poles of the objective lens is formed on the side of the sample, and an outer side surface and an inner side surface of each of the inner magnetic pole and the outer magnetic pole, respectively, forming the magnetic gap have each part of a conical shape with a convex having an angle of 45° or greater with respect to the optical axis.

Abstract: Techniques, apparatus and systems for detecting particles such as muons for imaging applications. Subtraction techniques are described to enhance the processing of the muon tomography data.

Abstract: A scanning probe microscopy (SPM) inspection and/or modification system which uses SPM technology and techniques. The system includes various types of microstructured SPM probes for inspection and/or modification of the object. The components of the SPM system include microstructured calibration structures. A probe may be defective because of wear or because of fabrication errors. Various types of reference measurements of the calibration structure are made with the probe or vice versa to calibrate it. The components of the SPM system further include one or more tip machining structures. At these structures, material of the tips of the SPM probes may be machined by abrasively lapping and chemically lapping the material of the tip with the tip machining structures.

Abstract: An electron beam inspection apparatus images reflected electrons and cancels negative charging derived from electron-beam irradiation. Ultraviolet rays are irradiated and an irradiated area of ultraviolet rays is displayed as a photoelectron image. The photoelectron image and a reflected-electron image are displayed on a monitor while being superposed on each other, to easily grasp the positional relationship between the images and the difference in size between them. Specifically, the shape of the irradiated area of an electron beam includes the shape of the irradiated area of ultraviolet rays on a display screen. The intensity of the ultraviolet rays in the irradiated area of the electron beam is adjusted while the reflected-electron imaging conditions for the reflected-electron image are sustained.

Abstract: A charged particle detector consists of a plurality independent light guide modules assembled together to form a segmented in-lens on-axis annular detector, with a center hole for allowing the primary charged particle beam to pass through. One side of the assembly facing the specimen is coated with or bonded to scintillator material as the charged particle detection surface. Each light guide module is coupled to a photomultiplier tube to allow light signals transmitted through each light guide module to be amplified and processed separately. A charged particle detector is made from a single block of light guide material processed to have a cone shaped circular cutout from one face, terminating on the opposite face to an opening to allow the primary charged particle beam to pass through. The opposite face is coated with or bonded to scintillator material as the charged particle detection surface.

Abstract: An object of the present invention is to provide an electron beam apparatus, in which a plurality of electron beams, e.g., four electron beams, is produced for one optical axis with a relatively high current achieved for each electron beam. Provided is an electron beam apparatus comprising: an electron beam emitter (32) having an electron gun (30), said electron gun (30) disposed along an optical axis (23) and operable to emit a plurality of off-axis electron beams along a direction defined by a certain angle with respect to the optical axis (23); a plurality of apertures (34) disposed at a location offset from the optical axis (23); and an electromagnetic lens (7) for forming a magnetic field between the electron gun (30) and the apertures (34) to control the plurality of off-axis electron beams emitted from the electron gun (30) so that the plurality of off-axis electron beams passes through the apertures (34).

Abstract: Provided is a portable electron microscope using a microcolumn. The portable electron microscope includes a microcolumn, a low vacuum pump, a high vacuum pump, an ultra-high vacuum ion pump, a first chamber for receiving and fixing the microcolumn and a sample to be measured and forming a vacuum by means of the pumps, a controller, and a case for receiving the pumps, the chamber and the controller.

Abstract: Information of a specimen holder or information of a specimen mounted on the specimen holder is stored in a memory inside the specimen holder mounted to an electron microscope. The memory is accessed to transmit the information of the specimen holder to the electron microscope, thereby ensuring that the user can use the specimen holder without mistaking characteristics of the specimen holder and danger of erroneous recording of the specimen information can be reduced.

Abstract: A photoconductive element for generating or detecting a terahertz wave comprises a carrier generation layer for generating carriers on light irradiation, a pair of conductive electrodes provided in opposition on one face of the carrier generation layer, each containing a strip line, a pair of conductive antennas placed in opposition with a gap for light irradiation onto the carrier generation layer, each being joined to the electrodes, a pair of conductive adjusting stubs for adjusting a propagation state of the terahertz wave generated or detected by the carriers, wherein each of the adjusting stubs has a length of not longer than the wavelength ? of the terahertz wave generated by the carriers, and is placed at a distance of not more than the wavelength ? from a joint between the antenna and the electrode.

Abstract: A representative embodiment of the invention provides an infrared (IR) detector having a movable plate supported at an offset distance from a substrate by a suspension arm. In response to a temperature difference between the plate and the substrate generated by the incident IR radiation, the suspension arm deforms and changes the offset distance for the plate. In one embodiment, the suspension arm has three rod-shaped bimorph transducers that lie within a plane that is parallel to the substrate. The transducers are also parallel to one another, with the transducer that is attached to an anchor of the suspension arm being located between the two transducers that are attached to the plate.

Abstract: Aspects described herein provide for the design and fabrication of a device with an enhanced pyroelectric response signal comprised of multi-capacitors that are connected in series. These capacitors are fabricated using multi-layers of materials such as lead zirconate titanate (PZT), BaxSr1-xTiO3 (barium strontium titanate) and Bi4Ti3O12 (bismuth titanate) films that exhibit pyroelectric affect and belong to the class of polar materials. By controlling the poling direction of the multi-layer integrated structure, the pyroelectric voltage can be aligned in one direction, and as a result, the voltage output from the single element is the total contribution from each capacitor.

Abstract: Diamond-like carbon based energy conversion devices and methods of making and using the same are disclosed. Such devices may include a surface for detection of infrared photons. Such a surface may include at least one metal cone and a diamond-like carbon layer disposed on the at least one metal cone. The at least one diamond-like carbon-coated metal cone is thus configured to receive infrared photons and generate electrons therefrom. In another aspect, the at least one metal cone may be an array of electronically coupled metal cones.

Abstract: Method and apparatus for detecting, by absorption spectroscopy, an isotopic ratio of a sample, by passing first and second laser beams of different frequencies through the sample. Two IR absorption cells are used, a first containing a reference gas of known isotopic ratio and the second containing a sample of unknown isotopic ratio. An interlacer or reflective chopper may be used so that as the laser frequencies are scanned the absorption of the sample cell and the reference cell are detected alternately. This ensures that the apparatus is continuously calibrated and rejects the baseline noise when phase sensitive detection is used.

Abstract: Disclosed is a Fourier transform infrared spectrophotometer, which comprises: a main interferometer section including a beam splitter, a fixed mirror, a movable mirror, and a phase plate disposed between the beam splitter and the fixed mirror; a control interferometer section having a quadrature control system for calculating a position of the movable mirror; a center-burst-position detection section operable, based on an input of interference signals and interferograms, to subject respective intensities of the interferograms to an addition processing while correcting a positional deviation of the movable mirror, so as to obtain a cumulative interferogram, and detecting a center burst position having a maximum intensity value in the cumulative interferogram; a center-burst-position storage section operable to store the detected center burst position; and a measurement-start-position determination section operable, based on the stored center burst position, to determine a measurement start position of the mova

Abstract: A color image sensing apparatus and a method of processing an infrared-ray signal are provided.

Abstract: A method and apparatus for excess signal compensation in an imaging system is described. In one particular embodiment, the invention provides for non-linear background, offset (due to time dependent dark current) and/or lag (including constant, linear and non-linear terms, due to image persistence) corrections of large area, flat panel imaging sensors.

Abstract: A radiation detector (100) includes at least first (202) and second (204) scintillators which absorb radiation and generate light at respective first (212) and second (214) wavelengths. The detector also includes at least first (206) and second (208) photodetectors. The first photodetector (206) is substantially non-responsive to light of the wavelength (212) generated by the second scintillator (204). Detectors having three or more scintillators and photodetectors may also be implemented.

Abstract: A portable hand-held system for identification of a radiation source includes a portable detection unit that detects gamma radiation, X-ray radiation and neutron radiation emitted due to nuclear decay in the radiation source being inspected and provides a corresponding detection signal based on the radiation. A radioisotope analysis unit analyzes radiation detected by the detection unit for determining radioisotope information. A display unit for displaying results of the analysis to a user, including radiation spectrum and the radioisotope information. A GPS receiver provides a current position information. A connecting unit communicates the results of the analysis and the current location to a remote computer. The detection unit, the radioisotope analysis unit, the display unit, the GPS receiver and the connecting unit form an integral device. The common housing includes a personal communicator with a microprocessor for the analyzing of the radiation spectra.

Abstract: A neutron detector comprises a gas-filled dielectric shell, preferably a glass balloon, having opposite electrodes. An electric field is established whereby ionizing particles may be detected via ionization and current flow in the gas, using a pulse height analyzer or other conventional means. The dielectric shell preferably has low gas permeability and a bulk resistivity in the range of 108 to 1017 ?-m, and is preferably in the millimeter to centimeter size range. Multiple balloons may be arranged in parallel or may be individually addressable by the detector electronics.

Abstract: A neutron detector has a volume of neutron moderating material and a plurality of individual neutron sensing elements dispersed at selected locations throughout the moderator, and particularly arranged so that some of the detecting elements are closer to the surface of the moderator assembly and others are more deeply embedded. The arrangement captures some thermalized neutrons that might otherwise be scattered away from a single, centrally located detector element. Different geometrical arrangements may be used while preserving its fundamental characteristics. Different types of neutron sensing elements may be used, which may operate on any of a number of physical principles to perform the function of sensing a neutron, either by a capture or a scattering reaction, and converting that reaction to a detectable signal. High detection efficiency, an ability to acquire spectral information, and directional sensitivity may be obtained.

Abstract: An improved radiation detection device measures a broad range of dose rate levels. According to one arrangement, the radiation detection device calculates a radiation value based on, gamma count information representing counts for different energy levels of radiation in a radiation field as well as a radiation intensity indicator value (e.g., photomultiplier tube anode DC current, measured directly by conventional Analog to Digital Converters or indirectly by power or current consumption information indicating how much energy is required to maintain a photomultiplier tube at a constant voltage) that is at least proportional to an amount of overall radiation energy detected in the radiation sample. Based on a combination of the gamma count information and the radiation intensity indicator value, a controller associated with a corresponding radiation detection device can calculate a radiation dose rate associated with the received radiation sample.

Abstract: A particle therapy system is provided. The particle therapy system includes a rotatable gantry with a gantry wall that surrounds an interior. A small irradiation chamber, with an irradiation chamber wall, is located inside the interior. The irradiation chamber wall is spaced apart from the gantry wall, and a deflection chamber is embodied between the two walls. The irradiation chamber wall includes a plurality of wall elements, which to enlarge the irradiation chamber are adjustable in the direction of the deflection chamber, for example, when positioning a treatment table in the small irradiation chamber, such that an opening in the irradiation chamber wall is created.

Abstract: The invention provides a method for patterning a resist coated substrate carried on a stage, where the patterning utilizes a charged particle beam. The method comprises the steps of: moving the stage at a nominally constant velocity in a first direction; while the stage is moving, deflecting the charged particle beam in the first direction to compensate for the movement of the stage, the deflecting including: (a) compensating for an average velocity of the stage; and (b) separately compensating for the difference between an instantaneous position of the stage and a calculated position based on the average velocity. The separately compensating step uses a bandwidth of less than 10 MHz. The invention also provides a deflector control circuit for implementing the separate compensation functions.

Abstract: A beam guidance magnet for deflecting a beam of electrically charged particles along a curved particle path is provided. The beam guidance magnet includes a coil system that does not include a ferromagnetic material affecting the beam guidance and has curved coils stretched out along the particle path, the coils being arranged in pairs in mirror symmetry to the beam guidance plane. The coil system includes two primary coils and two substantially flat secondary coils. The two primary coils include primary coil sides and primary coil end parts bent upward relative to the beam guidance plane. The two substantially flat secondary coils are disposed between the primary coil end parts. Supplementary coils are disposed in the field range of the respective curved secondary coil end parts.

Abstract: A high voltage insulator for preventing instability in an ion implanter due to triple junction breakdown is described. In one embodiment, there is an apparatus for preventing triple junction instability in an ion implanter. In this embodiment, there is a first metal electrode and a second metal electrode. An insulator is disposed between the first metal electrode and the second metal electrode. The insulator has at least one surface between the first metal electrode and the second metal electrode that is exposed to a vacuum that transports an ion beam generated by the ion implanter. A first conductive layer is located between the first metal electrode and the insulator. The first conductive layer prevents triple junction breakdown from occurring at an interface of the first electrode, insulator and vacuum. A second conductive layer is located between the second metal electrode and the insulator opposite the first conductive layer.

Abstract: A method of and apparatus for treating liquids flowing in a thin film around a source of wave energy to directly exposes the liquid to the wave energy, preferably generated in whole or part by an electrical arc between carbon electrodes. In addition to the wave energy generated by the electrical arc, energy generated by cavitation of the flowing liquid may be used in treating the liquid.

Abstract: An observable optical lamp status display system is provided for an ultraviolet irradiation lamp concealed from view. An external lamp status display panel that is within the field of view of an observer registers the operating status of each ultraviolet light irradiation lamp in an array of irradiation lamps. A separate fiberoptic lamp status display filament extends between each ultraviolet radiation lamps and the display panel. The lamp status display filament has a first end terminated in optical communication with the ultraviolet lamp and an opposite end that terminates at an optical sensor in the lamp status display panel. An observer can determine whether or not a lamp is operating simply by observing the output of the optical sensor in the display panel for each lamp operated.

Abstract: The invention relates to cleanable spiral modules and a method for production thereof.

Abstract: A fluorescence measurement probe capable of stably receiving a maximum received light amount of a fluorescent light generated from a specimen onto which an excitation light is radiated. The fluorescence measurement probe is applied to a fluorescence measurement system provided with an optical system. A light source emits an excitation light. A detector receives the fluorescent light. A solid light guide path serves as an optical path of the excitation light as well as the fluorescent light. A lens is disposed between an edge surface of the solid light guide path and the specimen. When a radiation angle of the excitation light is set to 2? at a position where the excitation light is collected by the lens which collects the fluorescent light. A excitation light beam NA expressed by sin ? is set to 0.14 or more and 0.31 or less.

Abstract: A method for performing photo-modification of a biological sample, the method comprising: (a) irradiating the sample; (b) detecting one or more signals based on the irradiated sample; (c) using one or more processor means to analyze the detected signals and determine one or more irradiation parameters, and, (d) returning to (a) conditioned on the irradiation parameters. Thus modifications may be determined and executed interactively as an experiment progresses, and therefore directed towards specific structures and/or events identified as of particular interest in the course of the experiment.

Abstract: The invention relates to a focusing and positioning ancillary device for a particle-optical scanning microscope, a particle-optical scanning microscope including a corresponding positioning aid, and a method for focusing and positioning an object in a particle-optical scanning microscope. The focusing and positioning ancillary device includes an illuminating device, a camera, a display and a control unit. The illuminating device produces a collimated or focused light beam at an angle to the particle-optical beam axis which intersects the particle-optical beam axis at a predetermined position. The camera is sensitive to the wavelength of the light beam and records an image of the object, which is positioned on the object table, at a second angle to the particle-optical beam axis. The control unit produces an image captured by the camera on the display together with a marking which indicates the position of the particle-optical beam axis in the image.

Abstract: The invention relates to a radiation detector, a method of manufacturing a radiation detector and a lithographic apparatus comprising a radiation detector. The radiation detector has a radiation-sensitive surface. The radiation-sensitive surface is sensitive for radiation with a wavelength between 10-200 nm. The radiation detector has a silicon substrate, a dopant layer, a first electrode and a second electrode. The silicon substrate is provided in a surface area at a first surface side with doping profile of a certain conduction type. The dopant layer is provided on the first surface side of the silicon substrate. The dopant layer has a first layer of dopant material and a second layer. The second layer is a diffusion layer which is in contact with the surface area at the first surface side of the silicon substrate. The first electrode is connected to dopant layer. The second electrode is connected to the Silicon substrate.

Abstract: The present invention provides a charged particle beam system which can perform evacuation on an electron gun chamber or an ion-gun chamber having a non-evaporable getter pump in a short time and can maintain the ultra-high vacuum for a long time, and a technology of evacuation therefor.

Abstract: To obtain an optical component having excellent secondary optical nonlinear properties by irradiating a surface and/or inside of glass having at least one member selected from Ni, Fe, V, Cu, Cr and Mn as a heat source material for absorbing and converting a laser beam to heat, incorporated to a glass matrix comprising at least one glass-forming oxide-selected from SiO2, GeO2, B2O3, P2O5, TeO2, Ga2O3, V2O5, MoO3 and WO3 and at least one member selected from alkali metals, alkaline earth metals, rare earth elements and transition elements, with a laser beam with a wavelength to be absorbed by the heat source material, to convert the irradiated portion to a single crystal or a group of crystal grains comprising components contained in the glass matrix and not containing the heat source material, thereby to form a pattern.

Abstract: A method for manufacturing a stitched space in a semiconductor circuit implements a photolithographic process for printing one or more image fields on a wafer surface, each image field corresponding to a portion of a circuit or device and including a space that is to be stitched in adjacent image fields. The space to be stitched that is produced from an image field is overlapped onto the space to be stitched produced from the adjacent image field, however, the overlapped space from the adjacent image fields is intentionally misaligned. The stitched space is then subject to the double light exposure dose to print the stitched space, with the result that an overlay tolerance of the stitched space is improved.

Abstract: A method and system for measuring contamination of a lithographic element is disclosed. In one aspect, the method comprises providing a first lithographical element in a process chamber. The method further comprises providing a second lithographical element in the process chamber. The method further comprises covering part of the first lithographical element providing a reference region. The method further comprises providing a contaminant in the process chamber. The method further comprises redirecting an exposure beam via the test region of the first lithographical element towards the second lithographical element whereby at least one of the lithographical elements gets contaminated by the contaminant. The method further comprises measuring the level of contamination of the at least one contaminated lithographical element in the process chamber.

Abstract: Information on the side of the body of an exposure apparatus is effectively used on the side of the laser light source apparatus. There is provided a laser light source apparatus which supplies a laser beam to a body of an exposure apparatus which exposes a wafer, and includes a controller adjusting an operation condition of the laser light source apparatus based on exposure information about the exposure operation supplied from the body of the exposure apparatus. The exposure information is exemplified by information on the waiting time until the light emission start or light emission continuation time and the operation condition is exemplified by the gas pressure in an emission chamber in which a laser beam is emitted, the temperature in the emission chamber and a number of revolutions of a blower in the emission chamber.

Abstract: The present invention relates to an ion implanter IMP comprising a pulsed plasma source SPL, a substrate-carrier tray PPS, and a power supply ALT for the tray. The implanter also includes a capacitor C connected directly to ground E and connected downstream from the tray power supply ALT. The invention also provides a method of using the implanter.

Abstract: A method for flattening a sample surface by irradiating the sample surface with a gas cluster ion beam, generates clusters of source gas in a cluster generating chamber, ionizes the generated clusters in an ionization chamber, accelerates the ionized cluster beam in an electric field of an accelerating electrode, selects a cluster size using a magnetic field of a sorting mechanism, and irradiates the surface of a sample. An irradiation angle between the sample surface and the gas cluster ion beam is less than 30° and an average cluster size of the gas cluster ion beam is 50 or above.

Abstract: A method that includes implantation of dopants while a III-nitride body is being grown on a substrate, and an apparatus for the practice of the method.

Abstract: A focused ion beam (FIB) processing system includes a FIB irradiation unit that irradiates a FIB onto a pattern formed in a wafer, to form a section of the pattern, an imaging unit that images the section of the pattern, a calculation unit that calculates a pattern size based on the image of the section, a judgment unit that judges whether or not a differential of the pattern size with respect to time is equal to or below a threshold; and a control unit that stops the FIB irradiation unit if the judgment unit judges that the differential of the pattern size is equal to or below the threshold.

Abstract: The invention relates to a structure characterising device comprising means which are used for generating a first pump radiation and a second probe radiation and for transmitting different wavelength radiation, means for producing a time offset between said first pump and second probe radiation on the structure by means of detecting means of said second beam after the reflection or transmission thereof to said structure in such a way that an analysis signal is generated, means for processing said signal and identifying an area corresponding to the signal jump, for determining the jump amplitude according to different wavelengths, for comparing said amplitude with a theoretical amplitude variation pattern according to the wavelengths and for determining, for the wavelength characteristic for said theoretical pattern, a characteristic value associated to the structure thickness and to the radiation propagation velocity in said structure.

Abstract: A flat UV light source has a tight packing of UV light-emitting diodes (56) that are arranged in a matrix. These light-emitting diodes are cooled by cooling air flows (66) or by cooling water flows.

Abstract: The invention relates to a UV irradiation unit comprising a housing (10), a rod-shaped lamp (12) which is arranged therein, a reflector (14) which extends along the UV-lamp (12) and which defines a lamp chamber (22) which surrounds the UV-lamp (12), in addition to a channel system (20) for guiding a cooling coolant through the reflector (14). According to the invention, the channel system (20) is arranged on the outside of the lamp chamber (22) such that it remains void of the coolant flow (24) for operating the lamp in an optimum manner.

Abstract: An optical system for radiation in the EUV wavelength range, in particular a projection exposure apparatus, having at least one vacuum vessel, including: at least one EUV-reflective optical element arranged in an optical path, and a holder which includes at least one sample element, the sample element having an optical surface which is exposed to incident EUV-radiation outside of the optical path, the sample element being sensitive to chemical alterations under influence of the incident EUV-radiation which also affect the optical element. The optical system further includes at least one detection unit for online detection of the contamination status of the sample element during exposure of the sample element to the incident EUV-radiation.