Tracor Northern, Inc.

Noran Instruments, Inc.

Wisconsin Alumni Research Foundation

Thermo Noran, Inc.

Jon J McCarthy

Thomas F Kelly

James V Howard

Jeffrey Carl Buchholz

Steven J Foote

James F Aeschbach

Frederick H Schamber

John D Fairing

David J McMillan

Derrick C Mancini

An x-ray optic is employed in combination with an energy dispersive spectroscopy (EDS) detector to enhance detection performance. Such a combined optic and detector may be employed in scanning electron microscope or environmental scanning electron microscope (ESEM) applications. The x-ray optic may be a grazing incidence optic (GIO) employed as a flux enhancing collimator for use with an EDS detector, used to perform electron beam microanalysis. It is found that the GIO in combination with an EDS provides substantial intensity gain for x-ray lines with energy below 1 keV. The GIO is also found to provide a modest focus effect, i.e., by limiting the field of view of the detector, and introduces minimal spectral effects. The combined optic and detector is useful in applications employing broad beam excitation, such as an ESEM or a system using x-ray fluorescence, to spatially limit the x-rays of interest to those within the acceptance angle of the optic.

Application of x-ray optics to energy dispersive spectroscopy

An x-ray collimator for wavelength dispersive spectroscopy and the like includes a grazing incidence mirror optic having a polycapillary x-ray optic nested therein. The polycapillary x-ray optic is mounted in a hollow bore of the grazing incidence mirror optic so as not to interfere with operation of the grazing incidence mirror. The polycapillary x-ray optic extends the range of the grazing incidence mirror optic to higher energy ranges. The x-ray collimator of the present invention may be employed in a wavelength dispersive x-ray spectrometer including a diffracting element positioned to receive x-rays collimated by the x-ray collimator, and an x-ray detector positioned to receive the x-rays defracted by the diffracting element. A wavelength dispersive x-ray spectrometer in accordance with the present invention may be used in combination with an energy beam microscope, such as an electron microscope, to analyze x-rays emanating from a sample specimen.

Wavelength dispersive x-ray spectrometer with x-ray collimator optic for

An improved X-ray spectrometer detector system includes a mechanical cooling system with a compressor connected by supply and return lines to a cryocooler connected to an X-ray dispersive spectrometer detector for an electron microscope. Within a housing containing a cryocooler heat exchanger, a heat sink thermal mass is thermally connected to a cold finger heat conducting structure which has the X-ray detector mounted at its distal end. The housing insulates the cryocooler heat exchanger and the heat sink from the external ambient. The compressor unit is operated to cool the detector to a desired low operating temperature at which precision measurements may be made. When such measurements are to be made, the compressor is turned off to minimize vibrations that could interfere with X-ray detector measurements or the operation of the electron microscope. The total heat capacity of the thermal mass of the heat sink is sufficient to cause the temperature of the detector to increase gradually while the compressor is turned off to allow a long period of time during which precision measurements may be made without any mechanical vibrations being introduced into the system from active refrigeration. When a temperature of the detector exceeds a higher threshold temperature, the compressor may automatically be turned back on to cool the detector down again to its desired operating range.

Method and apparatus for mechanically cooling energy dispersive X-ray

Atom probe apparatus includes an emission tip from which atoms can be evaporated in atomic emission events, a position sensitive detector for detecting the position and timing of the charge cloud resulting from atomic emission events, and a pulse heating beam for heating the emission tip in short pulses to evaporate atoms essentially one at a time from the emission tip. The heating beam may be formed as an electron beam from an electron gun which is directed to the tip and scanned rapidly back and forth across the tip to be incident upon the tip for short periods of time as the beam is scanned back and forth. The beam may further be produced as a chopped beam of electrons by scanning the beam back and forth across a slit in an aperture plate so that only pulses of electrons pass through the plate as the beam passes across the slit. The electrons passing through the slit are then focused and directed to the tip. The tip may also be heated by light from a pulsed source such as a laser which is passed through a reflecting Schwarzschild objective and focused onto the tip in pulses to provide excitation by light photons. The position sensitive detector, which may include a microchannel plate backed by a position sensitive wedge and strip detector, determines both the time of arrival of a charge pulse from an atomic emission event and the relative position of the charge cloud at the point where it impacts upon the detector. The detector may also be formed as a three-level, trigonal array of pads which allows both one and two atomic events per heating pulse to be resolved.

High-repetition rate position sensitive atom probe

The objective lens in a confocal tandem scanning reflected light microscope is movable relative to the specimen stage by piezoelectric actuators controlled by a closed-loop feedback control system having eddy current sensors to detect lens position. Position control input is either manual or automatic.

Objective lens positioning system for confocal tandem scanning reflected

A Tandem Scanning Microscope is disclosed using a modified Nipkow disk design. With this scanning system, scanning is performed using many apertures at once and using one disk for both image and illumination scanning. The apertures in the disk are in an annular pattern of spiral arms. Each aperture is located along a spiral arm at the end of a radius vector. Relative aperture locations are established in accordance with a mathematical relationship.

Confocal tandem scanning reflected light microscope

X-ray spectral data are normalized to beam current by basing data accumulations upon a fixed beam current integral rather than a fixed acquisition time. A current proportional to beam current is obtained from an aperture in an electron column instrument to provide a continuous monitor of beam current during data accumulation. The current is applied to a digital current integrator producing output pulses at a frequency proportional to the current. Connected to the digital current integrator is a one-shot producing a pulse of fixed width for each integrator pulse. The interval between one-shot pulses is defined as 'delay time,' and a signal representative of that time interval is produced and utilized to control the actual analysis time such that a prescribed beam current integral is obtained. The delay time signal may be combined with the normal system dead time signal to derive an effective dead time signal for controlling the length of actual analysis time to correct for variations in beam current as well as system dead time.

Growing community of inventors

Middleton, WI, United States of America

Jon J McCarthy