- Physics Find out what NIST is currently working on in Physics.
Jack Pevenstein
Technology Partnership Office
301-975-5519
nisttech@nist.gov
100 Bureau Drive, M/S 2200
Gaithersburg, MD, 20899
The present invention relates to a for a singular integral image deblurring comprising a direct procedure for classifying image smoothness and a class of fast, direct methods that recover fine-scale structure using Lipschitz (BESOV) space regularization, singular integrals, and the fast fourier transform.
A highly compact, portable, pulsed-molecular-beam Fabry-Perot cavity Fourier transform microwave spectrometer which incorporates ultra-fine Fabry-Perot mirror surface finishes has been developed for trace gas analysis. The mirrors, having a surface finish of less than or equal to 0.25 microns rms, are coated with nickel and then with either gold or silver. In a further embodiment, one or more fixed-tuned Fabry-Perot cavities are incorporated within a single vacuum chamber to monitor one or more chemical species of interest.
A method and apparatus for accurately generating a digitally synthesized sinusoidal voltage is started by storing digital values for sine waveforms in a read only memory. A first and second digital to analog converters are connected to the read only memory through latches. The outputs of the first and second digital to analog converters are alternatively switched between the inverting input and the non-inverting input of an operational amplifier such that one of the first and second digital to analog converter is connected to the inverting input while the other is connected to the non-inverting input. The output of the operational amplifier is connected to the inverting input through a variable capacitance, the feedback being determined by the one of the first and second digital to analog converter connected to the inverting input. A clock is used to control the connection of the first and second digital to analog converter to the inverting input and to control the determination of the feedback.
A Josephson quantizer is driven by a sinusoidal microwave generator whose output is combined with a digital two-level code representing a desired waveform. The result is to produce a bipolar drive signal of increased frequency and a bipolar Josephson output with voltage increased significantly. Output voltage is developed according to the relationship V=Nnmfs /KJ, where N is the number of junctions, n is the Josephson junction constant voltage step number, fs is the sampling frequency, m is an integer multiple of the sampling frequency and is .gtoreq.2, and KJ is the Josephson constant. The digital code generator receives the output of an improved modulator which incorporates a three-level to two-level transformation on the output of a standard three-level modulator in one embodiment. In a second embodiment, a modified two-level modulator produces a bit sequence where the polarity of the next bit is allowed to change only if there is an odd number of consecutive bits of the same polarity.
Spectroscopic materials analysis wherein a sample under test is bombarded by electrons in a scanning electron microscope to produce an x-ray emission collected over a large solid angle by a polycapillary lens and focused onto the surface of a microcalorimeter detector. The x-ray lens is used to increase the effective collection area of the microcalorimeter detector used in an x-ray spectrometer. By increasing the collection angle, the time period for x-ray collection is reduced and the detector can be located farther from the x-ray source. The x-ray lens is effective over a broad energy range of x-rays, thus providing compatibility with spectroscopic analysis. The microcalorimeter can be calibrated to compensate for any variations in the transmission efficiency of the x-ray lens.
A low noise accurate signal generator for a calibration system or a radar system includes a generator of a digital data stream having a predetermined frequency spectrum incorporated therein. A series connected array of Josephson junctions is coupled to and excited by the digital data stream to provide a stream of pulses with quantum mechanically accurate time integral. A low pass analog signal filter is coupled to the pulses of accurate time integral for extracting analog signals of the predetermined frequency spectrum. For radar applications, a low phase-noise local oscillator of a fixed RF frequency and the output of the filter are coupled to a signal mixer which outputs low phase-noise chirped RF signals for use in generating transmit pulses for the radar system whereby enhanced detection of targets in "clutter" can be obtained.
A pyroelectric detector with significantly reduced microphonic noise sensitivity that includes a pyroelectric detector element constructed from a z-cut LiNbO3 or LiTaO3 electret. Selective domain reversal is accomplished in the electret by applying an electric field. Electrodes are attached to either surface of the electret spanning the domain reversed region and a portion of the original domain region to create areas of equal and opposite sensitivity. The detector is mounted in an electrically grounded container or housing. The detector may also be constructed having multiple detector regions to accommodate resonant acoustic frequencies of the electret, to function as a position sensor, or both. In other words, the position sensor has multiple domain regions that also accommodate acoustic frequencies. The detector may also be constructed having domain reversed regions placed on the electret in a periodic pattern having a geometry and spacing that is related to the acoustic impulse response of the electret. Needle domains may also be interspersed in portions or throughout the electret to scatter acoustic waves and thereby reduce acoustic noise. Multiple detectors can be produced in a simple and inexpensive manner using shadow masking techniques.
A simple, compact optical spectrometer employs solid-state nonlinear crystals for obtaining broadband multichannel infrared spectra with picosecond or femtosecond time resolution. Spectrally broad infrared pulses are produced by difference frequency mixing in a first LiIO3 crystal between the second harmonic of a picosecond Nd+3 :YAG laser and broadband output of a synchronously pumped dye laser, and a resultant broadband IR pulse is upconverted by a second LiIO3 crystal to yield a blue visible pulse which is dispersed by a 0.25 meter spectrograph onto a multichannel vidicon or reticon detector to obtain four wave-number resolution single-shot transient infrared spectra of a sample. The present invention enables rapid acquisition of ultrashort time infrared spectra over a broadly tunable spectral range (in the mid to near infrared) at minimal cost and by a simple but versatile optical system employing readily available components.
A device and method provide for an accurate output from a unit, such as an oscillator and/or clock providing an output indicative of frequency and/or time. The device includes a processing section having a microprocessor that develops a model characterizing the performance of the device, including establishing predicted accuracy variations, and the model is then used to correct the unit output. An external reference is used to provide a reference input for updating the model, including updating of predicted variations of the unit, by comparison of the reference input with the unit output. The ability of the model to accurately predict the performance of the unit improves as additional updates are carried out, and this allows the interval between the updates to be lengthened and/or the overall accuracy of the device to be improved. The accuracy of the output is thus adaptively optimized in the presence of systematic and random variations.
An improved gravimeter mechanism includes a mass balanced cam having mutually opposed camming surfaces for controlling the free fall of a measuring mass. The cam is attached to a camshaft which turns at a constant rate, the rate being selected so that the drop time appropriate to achieve lift-off of the dropped object together with the time required to return to the start position equals the cam's rotational period. The mutually opposed camming surfaces cooperate to drive both a cart which supports a measuring mass and a compensating mass which is built into the gravimeter mechanism. The cam drives the cart, the measuring mass, and the compensating mass so that the time varying reduction in weight produced when the measuring mass is in free fall is exactly compensated by the compensating mass which is driven by the opposing camming surface. The opposing camming surface is displaced from the lift off region of the camming surface which drives the cart and measuring mass by 180 degrees. The measuring mass contains a mirror element of a Michelson interferometer, and the interferometer produces a signal indicative of the rate of free fall, which is directly proportional to the local gravity.
A low-loss comb-generating optical cavity including an optical amplifier and a microwave-driven electro-optic modulator crystal, produces a comb of optical frequency sidebands having spectral lines equally spaced around the frequency of an input laser beam incident on the comb-generating cavity. The comb-generating cavity includes an input mirror movable along the beam propagation direction, and a fixed position output mirror located at time synchronous distances of both the input laser wavelength and modulation wavelength. The comb-generating cavity and its microwave driven modulator are in resonance with the input laser beam, and provide iterative or recirculating beam action that transfers the input optical frequency of the laser, sideband by sideband, to remote and precisely known comb frequencies offset from, and centered on, the input laser frequency. Optical parametric amplification within the comb-generating cavity extends the sideband or comb spectrum and sharpens the time domain impulse represented by the cavity circulating fields. A relatively short bandpass filter optical cavity receives the comb output of the comb-generating cavity and is made up of the fixed-position mirror and a third mirror movable along the beam propagation direction. Fine movement of the third mirror tunes the bandpass filter cavity, and preferentially couples out the power of one or more comb frequencies. An optional input optical cavity at the input side may increase efficiency. A self-oscillating configuration provides optical parametric oscillation.
Disclosed is a system and method for stabilizing the carrier-envelope phase of the pulses emitted by a femtosecond mode-locked laser by using the powerful tools of frequency-domain laser stabilization. Control of the pulse-to-pulse carrier-envelope phases was confirmed using temporal cross correlation. This phase stabilization locks the absolute frequencies emitted by the laser, which is used to perform absolute optical frequency measurements that were directly referenced to a stable microwave clock.
The present invention uses a high energy x-ray, neutron, or gamma source for monitoring the interface between a molten and solidified crystalline phase while in a furnace in a casting process. The radiation can also be used to determine the quality and orientation of the crystals in the crystalline phase. The invention uses the distinctive diffraction patterns produced by crystalline and amorphous phases to locate the interface.
The change in the peak fluorescence wavelength of a small amount of a fluorescent compound, i.e., a fluorophore, which has been dissolved in a polymerizing material or a thermoplastic polymer is used to determine the extent of cure or solidification, respectively. The measured wavelength-shift can either be compared with a previously determined correlation to obtain an absolute value for the extent of cure, or can be utilized to compare or maintain an acceptable extent of cure throughout a manufacturing or a clinical process. Similarly, in the processing of a thermoplastic polymer by injection molding, the measured wavelength shift can either be compared with a previously determined correlation to obtain an absolute value for the temperature of the polymer, or can be utilized to adjust the injection molding cycle so that the mold is opened at the optimum times. The fluorophores used in the method are preferably selected from a class of fluorophores comprising alpha, omega substituted linear alkenes having an electron accepting group attached at the alpha position and an electron donating group attached at the omega position.
A high-Tc superconductor contact unit having low interface resistivity is disclosed, as is a method for making the unit. An inert metal is deposited on the surface of the superconductor, which surface is preferably non-degraded, to form a unit with the surface of the superconductor, and where temperatures as high as 500°C to 700°C can be tolerated, the unit is oxygen annealed to establish a still lower surface resistivity between the surface of the high-Tc superconductor and the inert metal, including a low surface resistivity of about 10-10 Ω-cm2 at high-Tc superconductor operating temperatures. The superconductor is a metal-oxide superconductor, and may be rare earth, thallium, or bismuth based.
Inspection of objects such as X-ray lithography masks is carried out by passing X-rays or extreme ultraviolet light through an object which absorbs in a pattern to provide a patterned X-ray or ultraviolet image which is then directed to a converter. The converter converts the image incident upon it to an image formed by electrons emitted from the converter. The emitted electrons are magnified in an electron microscope and the magnified electron image is displayed by the electron microscope. The visible image may be further digitized and processed by a computer, including long-term storage or display on a computer monitor. X-ray lithography masks may be inspected by passing X-rays through masks of the same type that will be used for lithography so that the magnified image of the X-rays passed through the masks corresponds to the pattern of X-rays that will be incident on a photoresist, allowing accurate inspection of X-ray masks before use.
A spray pyrolysis method for producing pure metal and/or metal oxide particles uses a mixture of a carrier gas and a solution of a metal salt precursor, water and a co-solvent reducing agent. The metal salt precursors preferably comprise metals from the group consisting of Fe, Co, Ni, Cu, Zn, Pd, Ag and Au, whereas the salt anions preferably comprise nitrates, acetates, oxalates and chlorides. The co-solvents are those that act as a reducing agent, are vaporizable, are inert with respect to the carrier gas, and are hydrophilic, such as alcohols, in particular, low-carbon numbered alcohols such as methanol or ethanol.
Multi-layer transition-edge sensors (TES) having improved performance, a method for preparing them and methods of using them. Specifically, the improvement lies in providing normal metal strips along the edges of the superconducting and normal metal layers parallel to the current flow in the TES during operation. These strips (referred to as "banks") provide for both improved detector performance and improved detector robustness against corrosion. This improvement is an important advance particularly for TES-based microcalorimeter detectors. The improved TESs also have many other applications based on the very precise thermometer function achieved by the TES.
This invention provides a method and apparatus for particle detection utilizing an Al/normal-metal bilayer transition-edge sensor (TES) coupled with a particle absorber. The TES is maintained in the transition region where its properties are extremely sensitive to temperature. In the detector, the energy of an absorbed particle is converted to heat by the absorber and the transition from the bilayer's superconducting to normal state is used to sense the temperature rise. The transition temperature, Tc, of the bilayer can be reproducibly controlled as a function of the relative thicknesses and the total thickness of the superconducting and normal-metal layers. The range of available Tc's extends from below 50 mK to above 1 K, allowing the detector to be tailored to the application. For x-ray detection the preferred Tc is about 50-150 mK. The width of the transition edge can be less than 0.1 mK, which allows very high detector sensitivity.
Apparatus and method for integrating lasers and optics on glass substrates. An optical (e.g., laser) component formed from a glass substrate doped with a optically active lanthanides species with a plurality of waveguides defined by channels within the substrate. The laser component optionally includes a monolithic array of individual waveguides in which the waveguides form laser resonator cavities with differing resonance characteristics. Another aspect is directed toward pumping the laser wherein a superstrate waveguide cavity, or cladding, Ls positioned adjacent the substrate waveguide for supplying the latter with pump light. A closed crucible processing of optical waveguides on a glass substrate is also described. Waveguides are created by exposing a surface of the substrate to an ion-exchange solvent (e.g., a molten salt). A tightly sealed multi-part crucible is provided in order that gas does not leak in or out of the crucible during cooling or heating of the system.
The phase-sensitive amplifier implementing our chi(3) 4-wave mixing source would be an enabling technology for image processing. A number of efforts in the newly labeled field of "quantum imaging" allow for better detection sensitivity or better image resolution if one is able to apply "squeezed" light with a broad range of spatial modes and frequencies. Such nonclassical light (a quantum mechanical treatment of the electromagnetic field is required) has proved difficult to produce in the past. Our present source is competitive with, but not quite as good as, the best available chi(2)-based systems in the degree of squeezing we have obtained. On the other hand, it is clearly superior to them in its ability to produce squeezed light in many spatial modes of the field. It will allow "noiseless image amplification" and "super-resolution" techniques to be employed in applications well beyond what has been demonstrated with chi(2) media. It should have uses in microscopy and image recovery from weak image data. In addition, a diode-based source should demonstrate squeezing at very low detection frequencies. This should allow the production of a very stable interferometer using our 4-wave mixing source. Such an interferometer would be an excellent detector for highly sensitive chemical detection by photothermal spectroscopy.
A technique for reducing the vibration sensitivity of laser-stabilizing optical reference cavities is based upon an improved design and mounting method for the 5 cavity, wherein the cavity is mounted vertically. It is suspended at one plane, around the spacer cylinder, equidistant from the mirror ends of the cavity. The suspension element is a collar of an extremely low thermal expansion coefficient material, which surrounds the spacer cylinder and contacts it uniformly. Once the collar has been properly located, it is cemented in place so that the spacer cylinder 10 is uniformly supported and does not have to be squeezed at all. The collar also includes a number of cavities partially bored into its lower flat surface, around the axial bore. These cavities are support points, into which mounting base pins will be inserted. Hence the collar is supported at a minimum of three points.
A zero-order overlay target comprises a first zero-order line array fabricated on a first layer of a semiconductor structure, the first zero-order line array having a first pitch, and a second zero-order line array fabricated on a second layer of the semiconductor structure, the second zero-order line array having a second pitch. The second pitch may be different from the first pitch, and a portion of the second zero-order line array may be positioned to become optically coupled to a portion of the first zero-order line array when subject to an overlay measurement. Further, the second pitch may be variable. For example, the variable pitch may comprise a first set of features having a pitch approximately equal to the first pitch, a second set of features having a pitch different from the first pitch, and a third set of features having a pitch approximately equal to the first pitch.
This invention consists of a new source for creating a focused ion beam. A magneto-optical trap serves as a source of cold atoms that are photo ionized to produce the ion source. Under appropriate conditions, the resulting ion cloud has temperature and spatial characteristics similar to that of the initial neutral atom cloud. An external electric field extracts the ions which can be focused using standard charged-particle optics. The cold temperatures achieved through laser cooling yield an ion beam with excellent characteristics which should allow for a beam resolution of 10 nm or less. The current produced from this source depends on the operating parameters of the MOT and can range from single ions on demand to over 100 pA, a much wider range than is currently possible. In addition, the wide range of elements that can be laser cooled greatly extends the possibilities for ionic species that can be used in FIBs, The net result is a source that has improved characteristics as well as expanded capabilities over current technology.
The invention is a system for obtaining a dimensional reference within a CT image. The system consists of a set of 3 spheres (for 2D; aID version would use 2 spheres; a 3D version would require 4 spheres) with a precise spacing. The material of the spheres is chosen to have x-ray absorption properties somewhat near bone. (In terms of Hounsfield units, about +500 HU to +1200 HU is useful; on this scale, bone is +1000 HU, water is 0 HU, and air is -1000 HU. Said otherwise, the attenuation length of the material should be about 2/3 to 40% of water.) The spheres need to be precisely round on the scale of a CT pixel which is typically 0.33 mm. We have found reasonably priced commercial spheres with tolerances of 0.0254 mm.
The invention disclosed herein is a novel and simple method of suppressing non-resonant background (NRB) in broadband coherent anti-Stokes Raman scattering (CARS) microscopy to improve sensitivity and signal-to-noise ratio.
A laser Doppler vibrometer for vibration measurement that employs active feedback to cancel the effect of large vibration excursions at low frequencies, obviating the need to unwrap phase data. The Doppler shift of a reflective vibrating test object is sensed interferometrically and compensated by means of a voltage-controlled oscillator driving an acousto-optic modulator. For frequencies within the servo bandwidth, the feedback signal provides a direct measurement of vibration velocity. For frequencies outside the servo bandwidth, feedback biases the interferometer at a point of maximal sensitivity, thus enabling phase-sensitive measurement of the high-frequency excursions. Using two measurements, one with a low bandwidth and one with a high bandwidth, more than five decades of frequency may be spanned. This approach is of particular interest for the frequently occurring situation where vibration amplitudes at low frequency exceed an optical wavelength, but knowledge of the vibration spectrum at high frequency is also important.
An optical method with the potential to discriminate between changes in the physical parameters of a target as represented in the properties of light scattered off of the target. For example, whether a change in the scattered light is due to a change in the height or width of a line.
A method and apparatus for detecting slow neutrons by monitoring Lyman alpha radiation produced by the .sup.3He(n,tp) nuclear reaction induced by neutrons incident on a gas cell containing .sup.3He or a mixture of .sup.3He and other atoms and/or molecules. Such a method and/or apparatus includes the use of, for example, liquid .sup.3He and .sup.4He mixtures as a scintillation counter for the sensitive detection of neutrons using Lyman alpha radiation produced by the .sup.3He(n,tp) reaction. The radiation can be detected with high efficiency with an appropriate photo-detector, or alternatively, it can be converted to radiation at longer wavelength by absorption in scintillation materials, with the radiation channeled to a photodetector. Because of the simplicity of the system and the fact that the radiation production mechanisms can be measured and/or calculated independently, the method and/or apparatus also has the potential for service as a calculable absolute detector.
Here we introduce a technique which allows sharp objects (e.g. scanning tunneling microscope tips, atomic force microscope tips, near-field scanning optical microscope tips, pipette tips, etc.) to be rapidly brought into close proximity to a particular region of a surface with high precision and accuracy in three dimensions. The method has potential applications in a broad array of tip-based research instrumentation and manufacturing techniques, including: scanning probe microscopy, atomic force microscopy, proximal probe lithography, dip-pen lithography, tip-indent lithography, molecule array manufacturing, and single atom manipulation.
In a typical atomic force microscope, course approach between tip and sample is achieved via a translation by a long range (0.1-1000 microns) stage followed by a fine stage movement (0.1-1000 nm); if the surface is not found, this process is repeated. Often, optical microscopes are used to aid in this process. Prior art does not allow registered tip approach due to the lack of a reliable method to yield precise three dimensional simultaneous localization of a tip and a sample surface. This knowledge is necessary in order to bring these objects into close proximity or contact with high resolution registration and speed.
An atomic magnetometer that simultaneously achieves high sensitivity, simple fabrication and small size. This design is based on a diverging (or converging) beam of light (in a single spatial optical mode) that passes through an alkali atom vapor cell and that contains a distribution of beam propagation vectors. The existence of more than one propagation direction permits longitudinal optical pumping of the atomic system and simultaneous detection of the transverse atomic polarization. The design could be implemented with a micromachined alkali vapor cell and light from a single semiconductor laser. A small modification to the cell contents and excitation geometry allows for use as a gyroscope.
A coherent laser radar that uses two coherent femtosecond fiber lasers to perform absolute ranging at long distance. One coherent femtosecond fiber lasers acts as a source and the other as a local oscillator for heterodyne detection of the return signal from a cooperative target. The system simultaneously returns a time-of-flight range measurement for coarse ranging and an interferometric range measurement for fine ranging which is insensitive to spurious reflections that can cause systematic errors. The range is measured with at least 3 μm precision in 200 μs and 5 nm precision in 60 ms over a 1.5 m ambiguity range. This ambiguity range can be extended to 30 km through reversal of signal and LO source roles.
Arrays of microfabricated hotplates have been used as substrate arrays for materials processing on a microscopic scale. Properties of individual elements (pixels) of the array, such as temperature and voltage bias, are controlled by addressing a given pixel with appropriate signals. Materials are deposited onto pixels with individually controlled deposition conditions (pixel temperature, bias). Pixels are also addressed to control properties during post-deposition processing steps such as heating in vacuum or various gases to alter stoichiometry of a single material, or to alloy multiple composition materials. The addressable heating characteristics may also be used for a maskless lithography on pixel elements. The result is an array of separately, but simultaneously, processed films. Properties of film elements may be measured using electrical contact pads. The array of processed films may be used for sensors, electronic devices, greatly accelerated materials development processes, and solid state physics, biology and chemistry studies.
Planar forms of chemically-sensitive materials have been combined, under temperature control, with the pixels of a specially-designed micro-hotplate array to produce a miniature device capable of analyzing chemical mixtures. The device uses integrated multiple elements having different adsorption properties and temperatures to collectively achieve chemical selectivity in sensing. The method of making and using selectively in sensing. The device of the present invention is manufactured by standard CMOS foundry techniques which allow the production of a range of devices that have improved sensing performance.
We have invented and modeled an intensity-modulated, laser-driven photoacoustic (PA) spectrometer with a calculable cell constant. The uncertainty in the calculated cell constant has been demonstrated to be about 1% or less. To this end, we combined first-principles models of acoustic wave propagation with high-resolution spectroscopic measurements. We modeled and measured the absolute response of an intensity-modulated photoacoustic spectrometer comprising a 10 cm long resonator and having a Q-factor of approximately 30. We used a detailed theoretical analysis of the system and predicted its response as a function of gas properties, resonance frequency, and sample energy transfer relaxation rates.
A method of comb-based spectroscopy with synchronous sampling for real-time averaging includes measuring the full complex response of a sample in a configuration analogous to a dispersive Fourier transform spectrometer, infrared time domain spectrometer, or a multiheterodyne laser spectrometer. An alternate configuration of a comb-based spectrometer for rapid, high resolution, high accuracy measurements of an arbitrary cw waveform.
Disclosed is a method for operating a sensor to differentiate between first and second analytes in a sample. The method comprises the steps of determining a input profile for the sensor which will enhance the difference in the output profiles of the sensor as between the first analyte and the second analyte; determining a first analyte output profile as observed when the input profile is applied to the sensor; determining a second analyte output profile as observed when the temperature profile is applied to the sensor; introducing the sensor to the sample while applying the temperature profile to the sensor, thereby obtaining a sample output profile; and evaluating the sample output profile as against the first and second analyte output profiles to thereby determine which of the analytes is present in the sample.
A pyroelectric detector with significantly reduced microphonic noise sensitivity that includes a pyroelectric detector element constructed from a z-cut LiNbO3 or LiTaO3 electret. Selective domain reversal is accomplished in the electret by applying an electric field. Electrodes are attached to either surface of the electret spanning the domain reversed region and a portion of the original domain region to create areas of equal and opposite sensitivity. The detector is mounted in an electrically grounded container or housing. The detector may also be constructed having multiple detector regions to accommodate resonant acoustic frequencies of the electret, to function as a position sensor, or both. In other words, the position sensor has multiple domain regions that also accommodate acoustic frequencies. The detector may also be constructed having domain reversed regions placed on the electret in a periodic pattern having a geometry and spacing that is related to the acoustic impulse response of the electret. Needle domains may also be interspersed in portions or throughout the electret to scatter acoustic waves and thereby reduce acoustic noise. Multiple detectors can be produced in a simple and inexpensive manner using shadow masking techniques.
The following is a description of an apparatus and method for producing and applying electron beams imprinted with phase vortices in an electron microscope. These beams have helical electron wavefronts, and each electron carries and quantized amount of orbital angular momentum and an associated magnetic dipole. Helicity-dependent absorption and scattering of electrons in a specimen, referred to here as electron helical dichroism, can be used to provide new types of information about the sample, but this requires a rapid way to switch the helicty of the probing beam. The invention described here produces multiple beams with different helicities that can be rapidly switched between.
This invention is a system for producing a charged particle beam from a photoionized cold atom beam. A vapor of neutral atoms is generated. From these atoms, an atom beam having axial and transverse velocity distributions controlled by the application of laser light is produced.The produced atom beam is spatially compressed along each transverse axis, thus reducing the cross-sectional area of the produced beam and reducing a velocity spread of the produced beam along directions transverse to the beam’s direction of propagation. Laser light is directed onto at least a portion of the neutral atoms in the atom beam, thereby producing ions and electrons. An electric field is generated at the location of the produced ions and electrons, thereby producing a beam of ions traveling in a first direction and electrons traveling in substantially the opposite direction. A vacuum chamber contains the atom beam, the ion beam and the electron beam.