WO2014178823A1

WO2014178823A1 - Gamma-ray microscopy methods

Info

Publication number: WO2014178823A1
Application number: PCT/US2013/038708
Authority: WO
Inventors: Nathaniel TRAN
Original assignee: Proteomyx Inc.
Priority date: 2013-04-29
Filing date: 2013-04-29
Publication date: 2014-11-06
Also published as: EP2992533A1

Abstract

This invention teaches a method of performing gamma-ray microscopy and how to build a gamma-ray microscope as well as its equivalent X-ray microscope, and neutron microscope. The method uses projection microscopy with a single-point source of radiation projecting the image of a sample onto a detector array like a film being projected onto a big screen in a movie theater. The advancement here is the creation of point source of radiation small enough to be significant because the size of this point source determines the best resolution possible. The point source of gamma rays is created by crossing a beam of electrons or just ions and a beam of positrons where both beams can be focused to be as small as their De Broglie wavelength. Similarly, a point source for X-rays is generated by crossing a beam of electrons and a beam of ions. A point source of neutrons can be created by crossing a beam of electrons and a beam of protons with sufficient energy, or a beam of protons knocking neutrons out of a beam of mercury ions. Methods for sourcing positrons and ions are taught as well as other features that are necessary to perform these microscopy methods.

Description

GAMMA-RAY MICROSCOPY METHODS

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to US patent No. 8,433,039 which is formerly US patent application No. 12,773,005 filed May 3^rd, 2010.

TECHNICAL FIELD

This invention is related to microscopy specifically gamma-ray microscopy, X-ray microscopy, neutron microscopy with high magnification and ultra-high resolution for use in the probing molecular structures and sub-molecular structures of matter.

BACKGROUND

Light microscopy's resolution is limited by its wavelength so naturally shorter wavelength can yield better resolution. However, the shortest wavelength equivalence of light is gamma rays and high energy X-rays cannot be bent or focused controllably the way light is thus there has been no gamma-ray microscope. Recently low-energy X-rays AKA soft X-rays have been used successfully for microscopy using a Fresnel zone lenses or a reflective mirror. This is because soft X-rays deflect or bounce off matter easily unlike high energy or hard X-rays which mostly pass through matter as they are absorbed.

Unlike light and electrons, there has not been a method available that can focus or bend gamma rays or hard X-rays controllably for use in microscopy. Thus instead of a gamma-ray microscope or a high energy microscope capable of seeing what' s inside atoms, physicists have to build the next best thing: the particle accelerator to smash atomic nuclei up to see what falls out.

Light is known to be bendable by traveling through a transparent material of higher refractive index than air at an angle. Electrons have charges thus the flight path of electrons can be controlled both by an electric field or a magnetic field. The shorter the wavelength of the radiation source used, the higher the achievable resolution possible. For electrons and other particles, the De Broglie wavelength at certain speed or momentum is the best known theoretically calculated wavelength of the particle radiation.

Gamma rays and X-rays are among the highest energy electromagnetic radiation with the shortest wavelength that can even penetrate dense materials such as lead. Both gamma rays and X-rays are identical electromagnetic radiation. They are only differently named because of the way they are generated. Gamma rays are naturally occurring electromagnetic radiation from atomic nuclear events such as radioactive decays and matter-antimatter annihilation. X-rays are man-made on Earth by crashing electrons into atoms especially more efficiently with higher atomic number atoms. Then there are gamma-rays which is an astronomy term referring to high energy electromagnetic radiation naturally produced from space that are mostly generated the same way that X- rays are generated here on Earth. The term gamma-rays indicate that they are naturally occurring while the hyphen reminds people that they are mostly generated the same way as X-rays.

Gamma rays typically have frequencies above 10¹⁹ Hz or wavelength in the picometer range or smaller. Lower energy and longer wavelength gamma rays are much rarer and harder to produce, but not their equivalent X-rays.

Werner Karl Heisenberg (1932 Nobel Prize in Physics) dreamt up a model gamma-ray microscope that can achieve very high resolution by using high-energy gamma rays for illumination to illustrate his uncertainty principle in 1925-1927. He explained how this gamma-ray microscope can be used to probe an electron' s position to within one wavelength of the gamma rays at best (λ). When this happen, the electron being probed may receive all or none of the momentum from the collision with this gamma-ray photon thus the electron' s momentum uncertainty is the same in magnitude as that of one gamma-ray photon (h/ λ). Multiplying the positional uncertainty and the momentum uncertainty yields his famous uncertainty principle: ΔρΔχ > (λ)(η/ λ) or ΔρΔχ > h. However, it has never been possible to make the lenses in his gamma-ray microscope model so up until now no such gamma-ray microscope exists. The short wavelength of gamma rays makes them desirable for use in high resolution and high magnification probing of sample. According to existing microscopy's principle, the shorter the wavelength, the higher the resolution is possible. With the wavelength of gamma rays, it is possible for a gamma-ray microscope to examine samples at the molecular, atomic, and even subatomic level.

The challenge is that since gamma rays cannot be controlled predictably in any way except for blocking by heavy shielding, it can only be used for non-magnifying or low magnifying methods of imaging such as Positron Emission Tomography aka PET scan. Similarly, high energy or hard X-rays are used to obtain an image of an object density, but little to no magnification can be done. As a result, instead of hard X-ray microscopy, X-ray diffraction patterns must be used to deduce the molecular structure of a molecule within a crystal to deduce the structure of molecules within. This is only possible for any molecules that can be crystallized because the repeatable patterns of the same molecule in the crystal are necessary for this method.

SUMMARY OF THE INVENTION The main object of this invention is to teach a method to perform gamma-ray microcopy using a single-point source of gamma radiation to illuminate samples thus enable magnification without the need to focus or bend gamma rays in a predictable manner. A sample is placed in close proximity to this single -point source which irradiates gamma rays outward from this point. Gamma rays that pass through the sample can continue traveling and they are detected by a detector array placed at a distance away. As a result, magnification is achieved with a magnification factor equal to the ratio of the source-to-detector distance divided by the source-to-sample distance. At high

magnification, the best resolution is equal to the size of the single -point source. Existing technologies can create a single point source of X-rays >1 micron in diameter by bombarding the very small tip of a needle with electrons. This invention teaches how to make a submicron single-point source of gamma rays by having a beam of electrons intercepting a beam of positrons where the interception point is the single-point source of gamma rays. Since both electron beam and positron beam can easily be focused, the size of the point source can be controlled and made as small as their theoretical De Broglie wavelength. Thus a 200 KeV beam of either electrons or positrons can be focused to be as small as 2.5 picometer in diameter at the very best. Accordingly, making a gamma-ray microscope with one Angstrom resolution is sufficient to probe the molecular structure of any molecules directly. This is already better resolution than any microscopes in existence.

Another object of this invention is to teach a method of achieving a small single- point source of other radiations such as X-rays, neutrons, neutrinos ... in addition to gamma rays by having a beam of subatomic particles intercepting another beam of subatomic particles, or a beam of subatomic particle intercepting a beam of molecules. Even two beams of molecules colliding can generate radiation. To control the size of the beam, this invention is limited to charged particles, and charged molecules AKA ions, and other focusable neutral particles such as photons in the infra-red, visible, ultraviolet and even soft X-rays to get a submicron and much smaller beam's focal point. The size of the beam is controlled and focused by electrostatic lenses including Einzel lenses which has the converging effect like a convex lenses' effect on light. Similarly, molecules can be ionized to gain charged so that a beam of molecules can be focused into submicron size. While the best mode of the invention is gamma-ray microscopy, other forms of microscopy such as X-ray microscopy, neutron microscopy, even neutrino microscopy can be accomplished by the same method.

A further object of the invention is to provide details on how to build a gamma- ray microscope and use it to probe a sample. Positrons can be sourced as they are emitted from positron emitting radioactive isotopes, and diverted into a beam by a small particle accelerator. Positron can also be trapped in a special device such as a Penning-Malmberg trap to create a pulsed beam if necessary. Electrons beams are generated by methods known in the art of making an electron microscope. Slits and electrostatic lenses are used to shape and focus the final positron and electron beam for interception at or near their focal points. These technologies allow portable generation of a positron beam and an electron beam that can be focused and crossed at a desirable point to yield a single-point source of gamma radiation. For instance, if the single -point source of gamma radiation is localized at 10 micrometer distance from a sample, and a detector array is placed 10 meters away then an effective one-million-time magnification is possible. If the sensor array can achieve 10 micrometer resolution, then the sample can be probed at 10 picometer resolution if the point source of gamma rays is < 10 picometer in diameter.

A further object of the invention is to mobilize the single-point source to different relative positions with respect to the sample to enable three dimensional imaging.

Alternatively the sample can be mobilized to achieve similar results. Multiple layers of detectors are used to increase detection efficiency, resolution, and enable tomography mapping. Any gamma-ray detected can easily penetrate layers of detector and trigger more than one detection events. Such events can be mapped to trace the gamma-ray path and separate signal from noise. An added feature for this mobilization is one that couple the sample vibration with the point source vibration. All matter vibrates even at near absolute zero Kelvin. Vibration will blur the images thus one way to overcome this obstacle is to make the sample and the point source vibrate in unison to an external stimulus such as a piezo crystal.

Additionally, while most gamma rays will pass through the sample unaffected, some will be scattered by deflection (bent) or even by reflection (bounced). A further object of this invention is to provide a means to study scattered or deflected and reflected gamma rays from a single -point source using multiple layers of detector array. The layers allow tomography mapping to trace the path of the gamma rays back to its points of origin on a sample. This allow studying of the angle that gamma rays strike the sample and the resulting angle from reflected and deflected gamma rays as well as their correlations. This will provide better understanding of subatomic structures and how different elements can scatter gamma rays differently.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1: Illustrates a description of how a gamma-ray microscope is assembled: a single -point source of gamma radiation is generated by crossing a positron beam and an electron beam. A sample is placed at a short distance from this source so that it is between a detector array and the single-point source. The sample is shaped as a thin slice to avoid getting hit by un-reacted electrons or positrons. The electron beam and the positron beam can be turned on individually to destroy any excess part of the sample that is in the path of these beams if necessary. It is also possible to have the electron beam and the positron beam in the same plane, but not the sample. This allows the sample to be placed very close to the source without getting struck by un-reacted positrons or electrons from the beam.

Figure 2: Illustrates how a gamma-ray microscope works. Gamma radiation is emitted from a single point source and irradiates outward from this point. The ratio (D₂:Di) of the distance between the single-point source and the detector (D₂) to the distance between the single point source and the sample (Di) is the magnification factor. Accordingly, the smaller the single point source is, the higher the resolution can be in addition to wavelength resolution limitation.

Figure 3: Illustrates how reflected gamma rays can be studied using a single-point source of gamma rays to map exactly how gamma rays interact with the sample. The detector arrays are shielded from the point source to enable analysis. These detector arrays have multiple layers to map the exact path of any gamma rays detected by the same process used in PET scanning. This path allows back tracing of the gamma ray to a point of origin on the sample. This point of origin is also most likely the point that a gamma- ray from the point source has hit allowing all the paths to be known. The back detector array is used to determine the amount of gamma rays passing through so that the percentage of gamma rays reflected can be calculated.

Figure 4: Illustrates how deflected or bent gamma rays can be studied using a single- point source of gamma rays. The exact path that a gamma-ray travel to hit the detector array can be determined with this set up. The back detector array is used to determine the amount of gamma rays passing through so that the percentage of gamma rays deflected can be calculated.

DETAIL DESCRIPTION OF THE INVENTION

Definitions: • Resolution: the ability to separate or resolve two objects that are very close together. One nanometer resolution thus means the ability to tell two objects that are one nanometer apart from each other.

• Point source is defined as a source with the size sufficiently small as a point. For the purpose of analysis here the point source should have a size equal to or smaller than the desirable resolution. Single-point source is used to emphasize that every thing come from one single point.

• Radiation: includes all electromagnetic radiation as well as all particle radiation such as alpha, beta, neutron, and neutrino... radiation.

· Scatter (radiation): as described here is either refraction or reflection or anything else that causes change to the path of radiation.

• Ion: charged molecule or atom with either positive or negative charge; ion can be created by stripping away one or more electrons or adding one or more electrons to a neutral molecule.

· Subatomic particles: any particles smaller than the size of an atom.

• Submicron: smaller than one micron or one micrometer.

Methodology:

Since gamma rays propagation cannot be manipulated controllably yet to make a gamma-ray microscope, we devise an alternative design that will yield the desirable high magnification and high resolution needed for gamma-ray microscopy. This design uses a single -point source to illuminate and project the image of an object placed close to this single -point source by projection microscopy. When a single -point gamma radiation source that irradiate gamma rays outward only from this point is placed in front of a sample, and a gamma-ray detector array is placed behind the sample (in relation to this source) the result is that the detector can detect gamma rays that travel through the sample as a magnified picture or a larger projected image. This is identical to what happens in a movie theater when a projector is used to show a movie, but here the projection light source is gamma rays from a point smaller than a micron in diameter. Since the single- point source irradiates gamma rays outward, the beam naturally magnify and become bigger and bigger as it is measured farther and farther away from the source. The same principle applies to the beam (portion) of gamma rays that passes through the sample; it is magnified into a larger beam as it gets further away from its source. If the sample blocks a part of the beam, or bend a part of the beam, then these actions would be magnified as the beam travel further away from the source. For instance, if the sample is placed just one hundred micrometers away from the single-point source of emission and the detector array is placed one hundred meters behind the sample, then the magnification factor is equal to the distance between the source and the detector divided by the distance between the source and the sample or (1,000,000 +1)/1 = 1,000,001 times. As a result, while gamma rays cannot be focused, we can still make a gamma-ray microscope according to this method.

The resolution of this method depends on two factors: size of the point source and detector resolution (wavelength is the third limiting factor that's not relevant here because both other factors are both bigger than wavelength). For example, with a single-point source of 1 nanometer maximal diameter and 10-micrometer detector resolution, at >10,000 times magnification, the resolution is 1 nanometer. With decreasing

magnification below 10,000 times, the resolution gets larger up until to 10 micrometer at 1 time magnification.

Typically, a detector is placed behind a sample with relative to the gamma-ray source. However, additional information can be gained by observing gamma rays that are bent or deflected by the sample thus other detectors all around the areas may be desirable. For instance, gamma rays have been known to bounce back when hitting a nucleus of an atom, thus a detector on the opposite side may pick this up as signal above the normal amount generated by the single-point source. If the source can generate gamma rays evenly in all direction then any increase in signal at any location can be readily detectable. With our design of gamma rays generated from intercepting a positron and an electron beam, gamma rays inherit the momentum of these electrons and positrons, thus radiation mostly favor one quadrant or one side of the point source, making it much easier to detect gamma rays that have been bounced by the sample.

Sourcing gamma rays:

We know that gamma rays can be generated when a positron annihilate an electron. So if we can control where the positron comes into contact with the electron, the position where gamma radiation originated can be defined. Furthermore, we want this position to be as small as possible down to a tiny point in space because the resolution of this imaging method depends on it. It is possible to generate and focus an electron beam as described in electron microscopy. A typical 200 kV electron microscope can have an electron beam with the wavelength of 2.5 picometer and can be focused with electrostatic lenses to a theoretical minimum size of 2.5 picometer in diameter at best. Similarly a positron beam can be accelerated and focused to collide with an electron beam at a defined point in space. A 2.5 picometer round beam intercepting another 2.5 picometer round beam at a perpendicular angle will have the interception point the size of a sphere with a diameter of 2.5 picometer at the biggest. For easier interception, a round beam of positrons between 1 micron and 2.5 picometer in diameter can intercept a wider but still have the same thickness beam of electrons to produce a single point source of gamma rays with the maximal diameter of slightly bigger than the diameter of the positron beam. An even more practical design is having a round or ellipsoidal positron beam passing through an Einzel lenses at the final stage to get a convex beam to intercept a rectangular convex beam of electrons at or near their focal points. The round beam thus will be cone shape with the tip of the cone as its focal point. The rectangular beam will be flatter and flatter toward its focal point. Moving these focal points is as simple as adjusting the lenses' voltage, thus changing the size of the point source is just as easy. These are simple ways of generating sufficiently small point sources of gamma rays; however, multiple beams can be used or different angles can be used for improving and manipulating the source if necessary.

One necessary feature for this type of source is the ability to manipulate both the positron beam and the electron beam in effect to tune the microscope. In addition to positioning the beam relative to the sample where the beam can be moved or the sample can be moved, the sizes and shapes of each beam can be changed. The directions of each beam can be manipulated to adjust how they intercept each others.

Positrons are not naturally abundant in this part of the universe as electrons, thus a source for producing them is needed. Radioactive isotopes that emit positrons can be used as a portable source. Naturally these isotopes will emit positrons in all directions. When any of the positrons come into contact with a molecule, the positrons will annihilate equal amount of electrons on that molecule and generate gamma rays. Instead of this natural loss, positrons can be diverted using electric field and magnetic field. These positrons can be accelerated and focused into a narrow beam for collision with an electron beam as they are generated. Alternatively, these positrons can be trapped and stored for use later when needed. A method of trapping and storing positrons is taught by US patent No. 6,630,666 the content of which is incorporated herein by reference. This allows various modes of operation such as continuous mode vs. pulse mode for the gamma-ray microscope. We can improve upon this trap by adding stacked electrostatic lenses to divert positrons and fill the chamber with helium^2"1" instead of vacuum. He^2"1" molecules do not have electrons for positrons to annihilate thus they work better than vacuum which is never perfect. When trapping is not necessary, then there is no need to moderate positrons using a moderator such as solid neon which yield only about 1 % of low energy positrons.

Positrons can be sourced from radioactive isotopes that emit positrons such as sodium-22. Many such isotopes exist and are known to those skilled-in-the art and can be selected depending on availability and cost. Other artificial sources can also be used such as positrons produced by high energy collision involving a particle beam, high energy laser striking a target such as gold to produce pairs of electron-positron from energy to mater conversion. The photons come from an intense laser and strike a gold target so that the energy get converted into matter to create pairs of electron-positron. Then electrons and positrons can be separated by a magnetic field into two different directions. The electron beam and positron beam used to generate the point source of gamma radiation can be controlled to produce coherent source of gamma radiation if necessary. One can use a method similar to the method taught by US patent No. 5,887,008.

The gamma rays generated by positron-electron annihilation inherit most of the kinetic energy of the parent particles, thus when 200 keV positrons annihilate 200 keV electrons the resulting gamma rays mostly have energy as high as 511 keV + 200 keV = 711 keV. As a result, shorter and shorter wavelength gamma rays can be generated with more energetic beam of positrons and electrons. It is also possible to generate a point source of X-rays. The traditional method of generating X-rays is by smashing electrons into a high atomic element such as a metal anode. However, the point source generated by this method cannot be as small. At best, current technology can only make this target to be ~1 micron such as a very fine tip of a needle. Accordingly, a beam of electrons can strike this tip of a needle to generate X- rays. While this is possible, the tip of the needle will melt or vaporize shortly under this high kinetic energy collision, leaving a duller and bigger tip behind. Another problem is that the point source has to be placed as close to the sample as possible for maximum magnification. When the sample is too close, these electrons may strike the sample as well. To overcome this problem, we have an electron beam striking a metal ion beam instead. Other types of rays such as neutrons, and neutrinos can also be used with this method to avoid the need of any focusing lenses.

Detection:

The method of detecting gamma rays and other high energy rays are known by those skilled in the arts. A gamma-ray detector array can be constructed of many photomultiplier tubes or photodiodes. Since gamma rays can penetrate several layers of detectors, it is best to have at least a few layers. Such detectors have been made for use in a Positron Emission Tomography or PET scanning instrument. Some have also been made for gamma-ray telescope and detector arrays used in a particle accelerator. Then a process similar to coincident counting can be used to eliminate noise. Briefly, if a detector in front detects a signal, then one of the detectors closely behind it should have detected a signal within a certain time frame for the signal to be counted; or else the signal is considered noise and is discarded. This will eliminate most of the noises generated by these highly sensitive detectors.

A more economical way to detect and record image of gamma rays is to use phosphor-imaging screens. These are made with phosphorescent materials that can be excited by radiation and then read back by re-excitation using a Phosphor-imager such as a Storm® 820 scanner from GE health care. This scanner has 50-micron resolution.

Having detectors or phosphor-imaging plates behind the sample relative to the point source make it possible to detect radiation passing through or come into contact with the sample to yield a transmission image, and radiation passing in close proximity (around) the sample to yield the outline shape of the sample. Shadows resulting from gamma rays getting scattered yield the position of things that gamma rays come into contact with or get interfered by. These things can be electrons or atomic nuclei. There may also be other things such as virtual particles that hold the atom together, but we have yet to see them. By strategically locate detectors at other locations, scattered gamma rays can also be detected and back traced by tomography to the source. At certain angles, gamma rays from the point source can be heavily shielded, but not gamma rays from the sample. Normally gamma rays are not emitted behind the point source relative to the sample (due to conservation of energy and momentum) thus making back scattering detection possible.

Alignment:

Typically, gamma rays generated by annihilation of fast moving positrons and fast moving electrons radiate within 30 degrees from the direction that these particles travel. This is conservation of momentum thus most resulting gamma rays will keep going in approximately the same direction of the parent particles. With reference to figure 1, most resulting gamma rays will travel upward toward the top quadrant. For maximum efficiency, it is best to place the sample on the imaginary center line dividing this quadrant into two equal parts.

It is desirable to have a positron beam and an electron beam intercepting each other to generate the smallest and most symmetrical point source possible. However, when such alignment is impractical such as in the case when the sample needs to be really close to the source, these beams can be crossed at different angles with the consideration of all resulting gamma rays inheriting the energy and momentum of electrons and positrons from these beams. Multiple beams of electrons can be used to cross one beam of positrons if need to. If the point source is not symmetrical in shape, then adjustment can be made at the detection end to compensate for the imaging process. The point source of gamma rays can be continuous or pulse depending on needs. Pulse mode along with fast detector array allows studying of temporal changes in structures as well.

Sample:

It is desirable to place the sample as close to the point source of gamma radiation as possible. Because of inherited momentum, more gamma rays will travel in one direction thus it is desirable to place the sample accordingly to get the maximum exposure. To do so, the sample needs to be shaped like a thin wire to keep the electron beam and the positron beam from hitting it. Such thin wire can be held between two needle points that can also provide the necessary cooling. Alternatively, the sample can be spread out like a pancake held by multiple points. The positron beam or electron beam when turned on individually can destroy part of the sample in their path if it does not destroy the sample in the process. If that pose a problem, then a laser beam should be used to cut these holes first. The purpose of creating these holes is for un-reacted positrons and electrons to escape without generating undesirable gamma rays or X-rays.

Miscellaneous:

It is possible to determine the shape and size of the point source using the method taught in US patent No. 5,432,349. Alternatively there are commercially available parts that can be used to determine the resolution by microscopy and thus the size of the point source.

Since positrons are harder to get, it is desirable to use excess amount of electrons compared to the amount of positrons in the corresponding beams. Un-reacted positrons are those that fail to turn into gamma rays via annihilation reaction with electrons. These un-reacted positrons can produce gamma rays elsewhere if they come into contact with mater or just electrons. As a result, the path for un-reacted positrons should be clear and then they can be reacted with electrons in a well shielded area or recycled back into the trap. It is also easier to control the energy of the electron beam simply by adjusting the cathode voltage, thus varying this voltage to get maximum annihilation can be done experimentally. A faster electron beam can pack more electrons into the same volume per second compared to a slower positron beam. Detector arrays should be shielded from all unwanted sources of radiation that can trigger a detection event when possible. Detectors that are exposed to the source of radiation directly can determine the radiation intensity and distribution. Gamma rays can travel long distance in air and especially in vacuum, thus there is little limit to how far away the detector array can be.

Scattering:

While a detector array placed behind a sample with respect to a single-point source is expected for microscopy, not all of the gamma rays that come into contact with the sample will pass through the sample. In theory, gamma rays get scattered such as deflected or bent (slight change in direction) after striking electrons. The same theory suggests that gamma rays get reflected or bounced back when striking atomic nuclei. If the theory holds, then scattering can provide useful information such as atomic nuclei's sizes... yielding composition of matter. The single-point source scattering allow one to map the exact path that gamma rays travel. Using multilayer detector arrays, topographic information can be obtained to back trace any detected gamma-ray to its point of emission. From there it is traced back to the single-point source origin. This makes possible the study of angle of incident, deflection, and reflection. Care should be taken to shield the detectors in use from the point source itself or any other sources of radiation not coming from the sample.

Variations:

While gamma rays is the best mode of this invention, other type of radiation including EM radiation as well as particle radiation can also be used for microscopy by a simple adaptation. For example, using a beam of electron intercepting a beam of molecules can generate X-rays. The efficiency of X-ray generation increases with higher atomic number atoms or molecules. Normally more than one wavelength of X-rays can be generated simultaneously, and the shortest wavelength depends on the collision energy of the crossing beam. This feature allows a single -point source X-ray microscope to operate at different wavelength of X-rays especially the longer wavelength where gamma rays generated by positron and electron annihilation can only be shorter than 2.5 picometer wavelength.

Single-point source neutron microscopy is also possible by generating a single- point source of neutrons for illumination. One way to do this is to cross a beam of electron and a beam of protons with sufficient energy so that electrons combine with protons to become neutrons and generate neutrinos in the process. Another way is to cross a beam of protons with a beam of molecules such as mercury so that each proton can knock about 20 neutrons out of a mercury atom for neutron microscopy. The neutrons will scatter from the point of collision mostly within a narrow angle toward one direction to obey the conservation of momentum. This neutron scattering can be used to illuminate a sample for neutron microscopy. The wavelength of neutrons can be calculated by the De Broglie wavelength equation as is 1837 times shorter than that of electrons moving at the same speed (a neutron's mass is 1837 times an electron's mass). While the preferred method to generate a single-point source of gamma radiation is having a beam of positrons intercepting a beam of electrons, a beam of positron intercepting a beam of charged molecules (that still have electrons) will also generate gamma rays. A beam of charged molecules may have some advantages and

disadvantages compared to a beam of electrons.

Ion generation:

Ions are preferably generated in gas phase or plasma phase for used in this method. While it is possible to have ion beams made of liquid, it is much more difficult to focus such beam to submicron size. Metal such as mercury can be vaporized by heat and then ionized by electro-ionization as well as photo-ionization. Electro-ionization can add or remove electrons using high voltage, while photo-ionization mostly removes electrons. Once ionized, ions can be accelerated into a beam using the same quadrupole used to accelerate positrons. This is only one possible design for particle accelerator out of many.

Possibilities:

The method of single-point source projection microscopy here can be applied to any beam of particles, and beam of molecules in existence. Crossing two beam so that the intersection yield a point source of radiation; controlling the beams so that this single point source is smaller than any similar source of radiation currently achievable. The only requirement is that the particles must be controllable specifically focusable. This means that any beam of charged subatomic particles or charged atoms or molecules (ions) can be used. Additionally, beams of focusable electromagnetic radiations such as infrared, visible light, ultraviolet light, and even soft X-rays can be used. This can be adapted to yield special properties of the resulting radiation such as using a laser beam and a coherent beam of electrons to generate coherent gamma rays as described in US patent No. 5,887,008

While it is also possible to create a single point source by having one beam hitting a thin foil, it is less stable. Gold foil has been known to be made as thin as 0.1 micron. A beam of positrons can hit gold foil resulting in gamma rays, or a beam of electron can hit the same foil resulting in X-rays. The problem here is that the kinetic energy of these particles will first move the foils' target spots so their positions are unstable, then with longer exposure the target area will be destroyed. Accordingly, this method is limited to lower resolution of just under one micron. Higher resolution with shorter wavelength:

Since the resulting gamma rays inherit the kinetic energy for its parent particles, having electrons and positrons colliding at higher speed can generate shorter wavelength gamma rays. The main limitation is other interfering events such as pair production by high energy gamma rays. At above 1.22 MeV, gamma rays can produce electron-positron pairs when it strikes anything such as the sample. This production does not become significant until the energy exceed 10 MeV. This means that 10 MeV gamma-ray microscope can be made with the theoretical smallest possible point source of -0.12 picometer or 0.12 picometer resolution.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The most preferred method of the invention is gamma-ray microscopy using a single -point source of gamma rays resulting from intercepting a beam of electrons and a beam of positrons at or near their focal points. Positrons are supplied by sourcing from positron emitting radioactive isotopes such as Sodium-22, Fluorine-18... The emitting positrons are diverted by electric field and magnetic field if possible (to increase yield) and accelerate to a beam with constant speed. The preferred particle accelerator has quadrupole design with four electrodes, best with hyperbolic shape just like those used in quadrupole mass spectrometers. With the right radio frequency and direct current voltage applied to these rods, only particles or ions with the correct charge to mass ratio are transmitted through. As a result, with the right frequency and voltage, we can send positrons streaming through the quadrupole and shooting out the other side as a constant beam of positrons. Now the positron beam can be passed through a slit if necessary to obtain certain shape, then electrostatic lenses to manipulate the size of the beam. Finally it goes through an Einzel lenses where the parallel moving positrons will be converging or a parallel beam will turn into a convex beam. The lenses voltage is then adjusted to move the focal point of the beam for controlled interception with an electron beam. Electrons are much easier to source thus a bigger rectangular shape electron beam will be made for ease of interception. At the last stage of focusing is also an Einzel lenses converging this beam into a flatter and flatter beam so that at the focal point, the beam has about the same thickness as the biggest diameter of the positron beam. Basically, it does not matter how wide the beam is, just the diameter of the interception volume as seen from the sample position. This diameter will be the same as the best possible resolution that can be achieved at high magnification.

At the heart of the gamma-ray microscope is a single-point source of gamma radiation that irradiate outward from a single point in space. Existing technology can produce the equivalent X-rays point source > 1 micron in size for a short time until the micron size needle tip melts or vaporizes to yield bigger tips. A focused and narrow beam of electrons is used to intercept a focused and narrow beam of positrons at a single point in space to create this single -point gamma radiation source. Similarly a focus beam of electrons intercepting a beam of metal ions can generate the same point source of X- rays. The reason for going to X-rays is to make longer wavelength which have unique behaviors in different materials. One example of this is the water window of X-rays from 2.34nm to 4.4 nm where water is transparent, but nitrogen and other elements found in biological molecules are absorbing. A sample holder to hold the sample is placed in close proximity to where the point source is when the beams are turned on. The holder should also provide cooling to the sample if necessary to keep molecular agitation to a minimum. Additionally, the sample holder can move the sample around or rotate in various axes so that the sample can be viewed in 3-D. The sample itself should be small enough to avoid getting struck by un- reacted positrons or electrons. Alternatively, simple way to trim the sample is by simply turning on just the positron beam, and then just the electron beam to vaporize any excess parts or at least to check to see if the beam will react with the sample.

There are two possibilities when gamma rays come into contact with a sample. Gamma rays can go right through, be scattered bent or deflected and slightly change direction or be bounced or reflected in almost the opposite direction. Accordingly, sensor arrays for detecting all these events should be available when possible. To detect gamma rays that have come into contact with the sample, the detectors' lines of sight to all other sources of radiation should be shielded leaving open only the path to the sample.

Claims

I claim:

1. A method of producing a sub-micron single-point source of radiation comprising the step of: crossing a beam of a first subatomic particles with a beam of a second subatomic particles or ions whereas the intersection of both beams is smaller than one micron in diameter.

2. The method of claim 1 further comprises the steps of:

a) exposing a sample to radiation from said sub-micron single-point source of radiation; and,

b) detecting radiation that has come into contact or come in close proximity with said sample.

3. The method of claim 2 wherein an image of radiation passing through said sample is obtained.

4. The method of claim 2 wherein an image of radiation scattered by said sample is obtained.

5. The method of claim 2 wherein said first subatomic particles are electrons and said second subatomic particles are protons.

6. The method of claim 2 wherein said first subatomic particles are electrons and said second subatomic particles are positrons.

7. The method of claim 6 wherein an image of radiation passing through said sample is obtained.

8. The method of claim 6 wherein an image of radiation scattered by said sample is obtained.

9. A method of analysis comprises the steps of:

a) producing a sub-micron single-point source of radiation by crossing a beam of subatomic particles with a beam of molecules whereas the intersection of both beams is smaller than one micron in diameter;

b) exposing a sample to radiation from said sub-micron single-point source of radiation; and,

c) detecting radiation that has come into contact or come in close proximity with said sample.

10. The method of claim 9 wherein said subatomic particles are positrons.

1 1. The method of claim 9 wherein said subatomic particles are electrons.

12. The method of claim 9 wherein an image of radiation passing through said sample is obtained.

13. The method of claim 9 wherein an image of radiation deflected by said sample is obtained.

14. The method of claim 9 wherein an image of radiation bounced or reflected by said sample is obtained.

microscopy method without the need for lenses or mirror comprises the steps of: a) producing a single-point source of radiation by crossing a beam of a first subatomic particles with a beam of a second subatomic particles or molecules whereas the intersection's diameter of both beams is not longer than a desirable microscopy resolution;

b) exposing a sample to radiation from said single-point source of radiation; and, c) detecting radiation that has come into contact or come in close proximity with said sample.

16. The method of claim 15 wherein at least one image of radiation that has come into contact with said sample is obtained.

17. The method of claim 15 wherein at least one image of radiation that has come in close proximity with said sample is obtained.