Patent Number: 
Section: description

In accordance with the present invention, a mechanism is provided for trapping and storing relatively large quantities of excited electrically neutral positronium (Ps*) in a mobile device, along with a means for either allowing the Ps* to self-annihilate and release the stored energy, or for ionizing the Ps* and producing a directed positron beam. Further, a mechanism is provided for introducing positronium into the trap and achieving the appropriate excited state. Relatively high storage densities are achieved by using the Bose-Einstein Condensate (BEC) form of Ps*. The approach of the present invention is based on a highly innovative trap for antimatter or exotic matter (mixture of antimatter and normal matter, e.g. positronium). The trap is constructed of photonic bandgap (PBG) structures containing at least one cavity, or an array of cavities. Recent theoretical and experimental work shows that it is possible to maintain atoms in an excited state by trapping them in cavities inside a three-dimensional PBG structure. The PBG behavior of the structure is dependent on a periodic contrast (one-dimensional, two-dimensional, or three-dimensional) in the index of refraction between the different constituent elements of the structure, the geometry and spacing associated with the arrangement of the constituent elements, and the shapes of the constituent elements. Examples of this type of material include the inverse opal backbone, macroporous silicon, colloidal crystals, woodpile structure, Yablonovite, and others well known in the field. It is important to note that given any two substances having sufficient index of refraction contrast that can be placed in a stable periodic arrangement, particular choices for the geometry, spacing, and shapes of the constituent substances of this periodic arrangement lead to the development of a photonic bandgap for a particular range of photon wavelengths. For two-dimensional lattices, the structure geometry can have symmetries such as triangular, rectangular, hexagonal, quasicrystal, etc. Generally, fully three-dimensional PBG structures are used for the PBG antimatter trap, but in certain cases it may be possible to use two-dimensional PBG structures. Open, connected structures (e.g., inverse opal) are preferred for vacuum attainment. As a specific example, a discussion is provided herein on the trapping and storage of Ps*, which is considered to be the most important embodiment at the present time. As technology improves, the technique may in the future be applied to excited states of other electrically neutral species of antimatter or exotic matter, as previously noted. The technique of the current invention may be modified to trap electrically charged species. However, the achievable storage density for an electrically charged species will in general not be as high as the achievable storage density for an electrically neutral species. FIG. 1 schematically depicts a single PBG cavity 10. Specifically, a cavity wall 12 is surrounded by PBG material 14. Excited positronium (Ps*) 16, comprising an electron (exe2x88x92) 16a and a positron (e+) 16b, is stored in the cavity 10. The Ps* can be stored in the form of a BEC, for applications requiring higher storage densities. The positron 16b can annihilate in one of two ways. In Ps* self-annihilation, the excited positronium Ps* 16 decays to the ground state and from the ground state the constituent electron 16a and positron 16b annihilate and are converted to two (or sometimes four) gamma rays for self-annihilation from the spin singlet state, or three (or sometimes five) gamma rays for self-annihilation from the spin triplet state. In Ps* pickoff annihilation, the positron 16b can annihilate with an electron at the wall 12 of the cavity 10, producing two (or sometimes four) gamma rays. In FIG. 1, S1 is the distance between the electron 16a and the positron 16b. S1 must be large enough to prevent self-annihilation, but small enough to keep the electron and positron in orbit about each other (a bound state). This is accomplished by placing the positronium atom 16 in the highly excited Rydberg state Ps*. S2 is the distance between Ps* 16 and the cavity wall 12. S2 must be large enough to prevent contact of Ps* 16 with the wall 12, thereby maintaining the Ps* in isolation from other electrons that could initiate the pickoff process. The positronium 16 is forced to the center of the cavity 10 by the intermediate photon 18 that is constantly being exchanged by the positronium and the wall 12 of the cavity 10. This central force is created by the average action, over time, of many photon exchanges. This central force maintains the Ps* near the center of the cavity 10. Further, a second (or third, etc.) bandgap can be used to block the 203 GHz pickoff process, in conjunction with the fact that the Ps* 16 is maintained near the center of the cavity 10, in isolation from electrons available at the cavity wall 12 (e.g., the pickoff process is attenuated by two techniques: maintain the Ps* 16 far from electrons, and also use the PBG structure 14 to block the photons emitted during the pickoff process). It will be appreciated that a delicate balance between S1 and S2 gives a long lifetime to Ps* 16 and confines the Ps* within the cavity 10. An excited species (e.g., Ps* 16) located deep inside this type of structure cannot decay by the emission of photons whose wavelengths lie within the bandgap, where the local radiative density of states is greatly reduced. When the excited species 16 tries to emit a photon 18, the photon undergoes multiple Bragg scatterings in the surrounding PBG structure 14 and is reflected back to the species 16, where it is reabsorbed. As noted above, this results in a stationary-state superposition of a localized photon and partially excited atom, or stable photon-atom-cavity bound state, and this process also provides a central force which tends to maintain the Ps* 16 near the center of the cavity 10. This unusual state of matter (or antimatter, or exotic matter) is predicted to be stable. It is noted that the excited species 16 is stable if it is ordinary matter at this point, but where positronium is concerned, it will self-annihilate into two gamma rays or three gamma rays unless it is in an atomic excited state, which inhibits this self-annihilation process. There are two things trying to happen when the positronium is in an excited state: atomic decay to lower energy levels, finally arriving at the ground state (and subsequent self-annihilation), and self-annihilation directly from the excited state. The teachings of the present invention are directed to delaying self-annihilation from the ground state by inhibiting the atomic transition from the excited state to lower energy states. This is accomplished by the use of PBG structures that prevent the emission of transition photons, and by preparing the initial excited state such that decays to lower energy states are inhibited due to there being a naturally-occurring forbidden transition. The initial excited state is also selected, as described below, to have minimal probability of direct self-annihilation. As noted above, once the bound antimatter or exotic matter atoms are created in a PBG structure 14, it is well known that these atoms can be placed in the proper long-lived excited state. This can be done using a laser tuned to a wavelength outside the bandgap. The proper long-lived excited state can also be achieved by creating the excited atom in a more highly excited state that cascades down to the proper excited state, from which further decay is inhibited by the surrounding PBG structure. Alternatively, the proper long-lived state can be achieved directly during the process for forming Ps*. Radioactive sources that exhibit xcex2+-decay (e.g., 22Na) are embedded in the PBG structure 14. As emitted high-energy positrons traverse the PBG material 14, they are slowed, and as they pass through the cavity wall 12, they capture an electron and form positronium in a Rydberg state. This Rydberg state can be the desired state, or it can be a state of higher energy (cascades down to the desired state), or it can be a state of lower energy (laser pumped up to a higher state). If higher storage densities are required for a particular application, then a BEC of Ps* can be established by any of a number of cooling techniques well known in the literature. Although only one cavity 10 is depicted in FIG. 1, it will be appreciated that, in fact, there is a three-dimensional array of cavities 10 in the PBG device, each capable of storing multiple atoms of Ps* 16. FIG. 2 depicts such an array 110 of cavities 10. Each cavity 10 is separated from its nearest neighbor cavities by a distance S3. As noted earlier, if S3 is greater than the photon localization length "xgr", then the cavities 10 will be isolated from each other. However, if S3 is less than the photon localization length "xgr", then the cavities 10 will be able to interact, a situation postulated to result in a new collective atomic steady state (a xe2x80x9cshadow crystalxe2x80x9d). The PBG structure of the present invention preferably comprises materials and geometry that together provide bandgaps at frequencies specific to each species to be stored in the antimatter storage device. The PBG behavior of the structure is dependent on a periodic contrast in the index of refraction between the different constituent elements of the structure, the geometry and spacing associated with the arrangement of the constituent elements, and the shapes of the constituent elements. It is important to note that given any two substances having sufficient index of refraction contrast that can be placed in a stable periodic arrangement, particular choices for the geometry, spacing, and shapes of the constituent substances of this periodic arrangement lead to the development of a photonic bandgap for a particular range of photon wavelengths. It is also important to note that if the periodic arrangement or index of refraction contrast is disturbed, the properties of the bandgap change, and the bandgap frequencies can be shifted or the bandgap effect can be entirely turned off. Controlled, recoverable structural deformation can be achieved, for example, using actuation by piezoelectric or microelectromechanical (MEM) devices, or by passing shock waves through the PBG structure. One-time destructive deformation can be achieved in many ways, including crushing or pulverizing the material. The index of refraction contrast can be altered by changing the index of refraction of the constituent elements, for example by applying external electric fields to an electro-optically active constituent such as birefringent nematic liquid crystal. If positronium is stored in the Rydberg state with principal quantum number n=33, a de-excitation cascade starting with a decay to the state with n=32 must be blocked. The decay from the state with n=32 takes place by the emission of a photon with a frequency of 95.9 GHz, or 3.13 mm. Therefore, the PBG structure must have a bandgap which includes 3.13 mm. Further, a second bandgap is used to block the pickoff process occurring at 203 GHz, or 1.48 mm. The PBG structure can be formed of air holes laid out in a quasicrystal geometry in an embedding matrix of silicon nitride, which is known to produce multiple bandgaps; for example, see FIG. 2 of M. E. Zoorob et al., xe2x80x9cComplete photonic bandgaps in 12-fold symmetric quasicrystals,xe2x80x9d Nature, Vol. 404, pp. 740-743 (13 Apr. 2000). The de-excitation cascade could also start with the emission of a photon with wavelength much different from the 1.48 mm wavelength associated with the pickoff process. In such cases, superimposed PBG structures can be used. For example, positronium decays from the state with n=11 to the state with n=10 by the emission of a photon with a frequency of 2.86 THz, or 105 xcexcm. A PBG structure for blocking photons with a wavelength of 105 xcexcm can be formed of a body-centered tetragonal lattice of silicon rods and veins, see for example D. Roundy and J. Joannopoulos, xe2x80x9cPhotonic crystal structure with square symmetry within each layer and a three-dimensional band gap,xe2x80x9d Applied Physics Letters, Vol. 82, pp. 3835-3837 (2 Jun. 2003). Superimposed on this structure can be another PBG structure for blocking photons with a wavelength of 1.48 mm. This PBG structure can consist, for example, of copper wires arranged in the three-dimensional diamond lattice of D. F. Sievenpiper et al, xe2x80x9c3D Wire Mesh Photonic Crystalsxe2x80x9d, Physical Review Letters, Vol. 76, pp. 2480-2483 (1 Apr. 1996). Other examples of three-dimensional PBG structures useful for the current invention are well known in the literature. The inverse opal structure is discussed by S. John and K. Busch, xe2x80x9cPhotonic Bandgap Formation and Tunability in Certain Self-Organizing Systemsxe2x80x9d, Journal of Lightwave Technology, Vol. 17, pp. 1931-1943 (11 Nov. 1999). The woodpile structure is discussed by S. Lin and J. G. Fleming, xe2x80x9cA Three-Dimensional Optical Photonic Crystalxe2x80x9d, Journal of Lightwave Technology, Vol. 17, pp. 1944-1947 (11 Nov. 1999). Yablonovite is discussed by E. Yablonovitch et al, xe2x80x9cPhotonic Band Structure: The Face-Centered-Cubic Case Employing Nonspherical Atomsxe2x80x9d, Physical Review Letters, Vol. 67, pp. 2295-2298 (21 Oct. 1991). Two-dimensional PBG structures useful for the current invention have been extensively reviewed in the literature; see, for example, J. N. Winn et al., xe2x80x9cTwo-dimensional photonic band-gap materialsxe2x80x9d, Journal of Modern Optics, Vol. 41, pp. 257-273 (1994) and J. D. Joannopoulos et al, xe2x80x9cPhotonic Crystals: Molding the Flow of Lightxe2x80x9d, Princeton: Princeton University Press (1995). Nowhere in the open scientific literature or in patent prior art are there suggestions that one can trap excited positronium 16 in a PBG cavity 10. Specifically, it is certainly not obvious that Ps* can or should be trapped using cavities in PBG structures, such that the lifetimes against self-annihilation and pickoff annihilation with electrons in the cavity walls 12 are greatly enhanced. Self-annihilation and pickoff annihilation are not relevant when trapping atoms or molecules composed of ordinary matter. To the best of their knowledge, the present inventors are the first to recognize that by balancing the two distance parameters S1 and S2 (see FIG. 1), it becomes possible to extend the lifetime of Ps*, and other excited neutral species of antimatter or exotic matter as discussed above, by many orders of magnitude without extensive apparatus. The parameter S2 is kept at a maximum, with the beneficial action of preventing the Ps* 16 from contacting electrons in the cavity wall 12. This prevents pickoff annihilation processes with electrons available at the cavity surface. The lifetime against self-annihilation can be a few seconds to a few years. The lifetime is chosen based on the application. For example, a lifetime of seconds is appropriate for the medical field, whereas a lifetime of years is appropriate for interplanetary propulsion. In positronium, the separation S1 between the electron 16a and the positron 16b increases with the principle quantum number n, where n can be at least as high as 134 (P. Wallyn et al., xe2x80x9cThe Positronium Radiative Combination Spectrum: Calculation in the Limit of Thermal Positrons and Low Densitiesxe2x80x9d, Astrophysical Journal, Vol. 465, pp. 473-486, 1 Jul. 1996). In the technical language of quantum mechanics, this is expressed by stating that as n increases, the overlap of the wave functions of the electron and positron decreases, and they can be considered further apart (larger S1). Karlson and Miitleman (Antonella Karlson and Marvin Mittleman, xe2x80x9cStabilization of positronium by laser fieldsxe2x80x9d, Journal of Physics B, Vol. 29, pp. 4609-4623, 1996) note the following: xe2x80x9cPositronium (Ps) is an unstable system. Singlet Ps annihilates mainly by emission of two gamma quanta with a lifetime of xcex93s=1.25xc3x9710xe2x88x9210 s and the triplet state mainly by three gamma emission and xcex93tr=1.4xc3x9710xe2x88x927 s. The annihilation reaction is caused by a quantum electrodynamical interaction term in the Hamiltonian, whose range is of the order of the Compton wavelength xcexc [xcexc=2.42xc3x9710xe2x88x9212 m]. On the scale of the Ps atom, this is essentially a zero-range operator. Thus, the decay rate is proportional to the absolute value squared of the Ps wavefunction at the origin, where the two particles are in contact. Since the wavefunction of Ps vanishes at the origin for all but states with angular momentum zero, Ps annihilates for all practical purposes only from S states. For them the annihilation rate depends on the principal quantum number as nxe2x88x923. For states with higher angular momentum l, the annihilation rate is smaller than the rate for the respective S state by a factor of (aB/xcexc)xe2x88x9221 . . . , where aB is the Bohr radius [aB=52.9xc3x9710xe2x88x9212 m] . . . Therefore, the lifetime of these states is considerably larger.xe2x80x9d It is then clear that the lifetime xcex93n,l of an excited state of positronium with principal quantum number n and angular momentum l is related to the lifetime of the ground state of positronium xcex930 (either the singlet state or the triplet state) by xcex93n,l=xcex930n3(aB/xcexc)2l=xcex930n3(21.8)2l. For an excited state with angular momentum l=0, the lifetime is increased over that of the ground state by a factor of n3. For example, an excited state with n=134 and l=0 has a lifetime extended by a factor of approximately two million over that of the ground state. If Ps* could be maintained in the spin triplet state with n=134 and l=0, e.g., by using the device of the present invention, the lifetime of the spin triplet Ps* would be extended from 1.4xc3x9710xe2x88x927 s to approximately 0.3 s. If we prepare the excited state to have a non-zero value for the angular momentum l, then the lifetime is enhanced by another factor of (21.8)2l. For example, an excited state with n=134 and l=1 has a lifetime extended by a factor of approximately one billion over that of the spin triplet form of the ground state. An excited state with n=134 and l=3 has a lifetime extended by a factor of approximately 2.6xc3x9710xe2x88x9214 over that of the spin triplet form of the ground state, resulting in a lifetime of xcex93134,3=3.6xc3x97107 s=1.15 years. It is recognized by the present inventors that the method of Ackermann, Schmelcher, and Shertzer may be synergistically used in conjunction with the device of the present invention to extend the lifetime of Ps*. However, this may result in the need for substantial apparatus that is not amenable to a mobile device, but could certainly be used for applications that allow substantial apparatus (e.g., power plant or interplanetary propulsion system). As with the he lifetime against self-annihilation, the lifetime here can also be a few seconds to a few years. Again, the lifetime is chosen based on the specific application, where, for example, a lifetime of seconds is appropriate for the medical field, whereas a lifetime of years is appropriate for interplanetary propulsion. It is noted above that the scientific literature contains references to forming a BEC of positronium in its ground state, Ps. The present inventors have recognized that a BEC can also be formed using positronium in its excited state, Ps* 16, and this BEC can be trapped and stored in the device of the present invention. Since there is no prior art discussion of forming and using a BEC of Ps*, the present inventors consider this to be a new application for storing Ps. Assume, for example, that Na=109 Ps* atoms can be stored in a single cavity 10, in the form of a BEC. Further, assume that at least Nc=1012 cavities/cm3 can be created as arrays 110 in PBG materials 14 such as the inverse opal structures noted above. This gives a Ps* number density xcfx81Ps*=Naxc3x97Nc=102l Ps*/cm3. The energy released upon the self-annihilation of positronium is 1.022 MeV/Ps*. For the storage conditions of this example, the energy storage density is xcfx81E=xcfx81Ps*xc3x971.022 MeV/Ps*=1027 eV/cm3xcx9c108 J/cm3. If 1 cm3 of this material is released in 1 ms, the resulting power is 108 J/10xe2x88x923 s=1011 W, or 100 Gigawatts. Assume also that the cavities have a typical diameter of 1 xcexcm, as is commonly achievable using the inverse opal geometry. Then, from FIG. 4 of Cassidy and Golovchenko, supra, it is clear that the Ps* can undergo a transition to the BEC state at a temperature approaching room temperature, or approximately 300 degrees Kelvin. Given the expected Ps* number density per cavity, the device can be fashioned to have cavity diameters larger or smaller, in order to achieve a transition to the BEC state at a particular desired temperature. The antimatter may be introduced into the antimatter trap by a variety of methods, including, but not limited to, the following three methods: (1) The antimatter (e.g., positrons) from radioactive sources or accelerator sources can be injected through a velocity moderator (e.g., tungsten). The velocity moderator can be located within the PBG material 14 of the PBG device, or it can be located outside the PBG device. (2) Positrons and electrons can be pair-produced by high-energy gamma rays generated by electron beams or as a by-product of neutron capture processes such as 113Cd(n,xcex3)114Cd* (see above). The neutrons can impinge on the PBG device in a collimated beam, or the PBG device can be placed inside a nuclear reactor in which there is an abundance of neutrons. (3) A radioactive material that emits positrons (e.g., 22Na) can be embedded in the PBG structure 14, resulting in a xe2x80x9cself-chargingxe2x80x9d device. A positron 16b that has been introduced into the PBG structure by any of the foregoing methods travels through the material, and when it encounters a cavity 10, the positron 16b picks up an electron 16a as it traverses the cavity wall 12. This process results in the formation of an excited positronium atom 16 in the cavity 10. The formed excited state could have principal quantum number n different from that desired for the trapped state. If the created Ps* is in a state with energy lower than desired, then a tuned laser can be used to pump the Ps* up to (or above) the desired excited state. If the created Ps* is in a state with energy higher than desired, or if it has been pumped up to a state with energy higher than desired, then the Ps* can then be allowed to cascade decay down to the desired state, at which point the surrounding PBG structure prevents further decay and preserves the desired state. All current traps for electrically neutral species share the common disadvantage of not being able to capture and store relatively large quantities of positronium for relatively long times. All current traps for electrically neutral species are generally not easily portable, due to operating requirements calling for relatively high mass, relatively high volume, and relatively high power requirements. The present invention should produce a mobile storage container that can trap relatively large quantities of positronium, and store it for relatively long times (orders of magnitude longer than the natural in vacuo lifetime of positronium). The device of this invention would have utility in several fields, including medical applications, materials testing applications, rocket motors, high power/high energy density storage, and as an ignition device for initiating nuclear fusion reactions in power plant reactors or hybrid rocket propulsion systems. It may also be possible to coherently annihilate all of the Ps* stored in the photonic bandgap (PBG) device of the present invention. This makes possible a PBG device as a component of a 511 KeV gamma ray laser (GRASER) operating from the annihilation radiation. The GRASER is well described in the scientific literature. One method for developing a GRASER is based on the generation of gamma rays from the decay of excited nuclei (e.g., George C. Baldwin and Johndale C. Solem, xe2x80x9cRecoilless gamma-ray lasersxe2x80x9d, Reviews of Modem Physics, Vol. 69, pp. 1085-1117, 4 Oct. 1997, or U.S. Pat. No. 4,939,742 entitled xe2x80x9cNeutron-Driven Gamma-Ray Laserxe2x80x9d and issued to Charles D. Bowman on Jul. 3, 1990). Another method using a Bose-Einstein Condensate (BEC) of electrons stored in a high-energy electron storage ring or collider is disclosed in U.S. Pat. No. 5,887,008, entitled xe2x80x9cMethod and Apparatus for Generating High Energy Coherent Electron Beam and Gamma-Ray Laserxe2x80x9d and issued to Hidetsugu Ikegami on Mar. 23, 1999. Another method is based on the generation of gamma rays via the annihilation of electrons and positrons. Hidetsugu Ikegami discloses a method of producing a GRASER by combining an electron beam and a positron beam using accelerators, in U.S. Pat. No. 4,933,950, entitled xe2x80x9cGenerating Method for Free Positronium Radiation Light and Apparatus Used in this Methodxe2x80x9d and issued on Jun. 12, 1990) and in U.S. Pat. No. 5,617,443, entitled xe2x80x9cMethod and Apparatus for Generating Gamma-Ray Laserxe2x80x9d and issued on Apr. 1, 1997). Using a BEC of positronium to generate a GRASER is discussed by Edison P. Liang and Charles D. Dermer in xe2x80x9cLaser Cooling of Positroniumxe2x80x9d, Optics Communications, Vol. 65, pp. 419-424, 15 Mar. 1988, and by Allen P. Mills Jr. (May 2002, supra). The methods for producing a GRASER using a BEC of electrons or a combination of a positron beam and an electron beam require substantial apparatus and physical plant, and sufficient cooling mechanisms to develop a BEC for the former case. For using a BEC of Ps to generate a gamma ray laser, sufficient storage densities must be achieved. The present inventors are the first to describe a way to achieve sufficient storage density for a Ps BEC-based GRASER, with the absolute numbers of stored Ps atoms exceeding what is possible in the standard charged plasma traps or the conventional neutral atom traps. Furthermore, the present inventors describe a device that does not require substantial apparatus and physical plant. Moreover, in the present device, the Ps BEC is maintained for lifetimes many orders of magnitude greater than that in the prior art, allowing the user great flexibility in the timing for releasing the energy in the form of a GRASER. Mills (May 2002, supra) calculates that having 1012 Ps atoms stored in the spin triplet form of the ground state in a cavity with radius 200 nm and length 1 mm is sufficient for radiation amplification, upon the application of a pulse of radiation tuned to the hyperfine transition such that the Ps atoms decay from the spin triplet ground state to the spin singlet ground state and subsequently self-annihilate. The device of the present invention meets, and far exceeds, these storage density requirements. It should be noted that depending on the application for the present device, it may be desired for the stored Ps to annihilate from the singlet ground state, so that two 511 KeV gamma rays are produced. The decay mode preferred by the spin triplet ground state results in three gamma rays whose total energy sums to 1.022 MeV, allowing the possibility of gamma rays with energy small compared to 511 KeV. Hence, it is necessary to control the PBG such that the stored excited positronium can be stimulated to go to the ground state, where both the spin singlet and spin triplet states are populated, and then modify the decay of the spin triplet state to either self-annihilation into three gamma rays, or further decay to the spin singlet state and subsequent self-annihilation into two gamma rays. De-excitation from the excited state can be accomplished by several mechanisms, including shifting or turning off the photonic bandgap by applying stress to the PBG lattice (e.g., by using piezoelectric actuator devices attached to the PBG lattice) or by using any method to sufficiently change the symmetry, lattice constant, or the refractive index contrast ratio of the PBG structure. By controlling the energy level decay path, it is possible to use multiple photonic bandgaps to route the decay to the ground state. As the atoms drop to the ground state, sending a gamma ray pulse with energy 511 KeV through the device in the desired direction will stimulate coherent annihilation, rather than allowing self-annihilation to produce isotropic radiation. Also, as the atoms drop to the ground state, applying a pulse of radiation with frequency 203 GHz (the frequency separating the spin triplet and spin singlet states) can cause the spin triplet population to decay to the spin singlet state rather than self-annihilating directly from the spin triplet state. It is also noted that one can encase the present device in a material with a high cross section for 511 KeV gamma rays, leaving open an aperture in the desired direction for the GRASER. The encasing material will absorb gamma rays not traveling in the desired direction, possibly generating waste heat that can be captured and used for other purposes such as energy production via thermoelectric conversion. If the self-annihilation is allowed to occur from the spin triplet state, many gamma rays with energy less than 511 KeV are produced. The gamma rays with energy less than 511 KeV are easier to capture in a material than the 511 KeV gamma rays. As described above, the antimatter trap disclosed and claimed herein can store excited electrically neutral species, e.g., an excited state of positronium (Ps*). The antimatter trap comprises the three-dimensional or two-dimensional photonic bandgap (PBG) structure, in which carefully chosen periodic variations in the amplitude of the local index of refraction N(x,y,z) exist in all three spatial dimensions. These periodic variations in the amplitude of N(x,y,z) have length scales comparable to the central wavelength of the bandgap. Excited species soon attempt to reach their ground state via the emission of one or more photons. An excited species located within a cavity deep inside the type of PBG structure disclosed in this invention cannot decay by the emission of photons whose wavelengths lie within the bandgap, where the local radiative density of states is greatly reduced. When the excited species tries to emit a photon, the photon is reflected by multiple Bragg scatterings within a photon localization length "xgr" (typically approximately several photon wavelengths) back to the species, where it is reabsorbed. In effect, the species is dressed by its own radiation field (Sajeev John and Jian Wang, xe2x80x9cQuantum optics of localized light in a photonic band gapxe2x80x9d, Physical Review B, Vol. 43, pp. 12772-12789, 1 Jun. 1991). The result is a stationary-state superposition of a localized photon and partially excited atom, or stable photon-atom-cavity bound state. This unusual state of matter is predicted to be stable (Sajeev John and Jian Wang, xe2x80x9cQuantum electrodynamics near a Photonic Band Gap: Photon Bound States and Dressed Atomsxe2x80x9d, Physical Review Letters, Vol. 64, pp. 2418-2421, 14 May 1990). If adjacent cavities are located within the photon localization length "xgr", the localized photon can be shared among excited species via the Resonant Dipole-Dipole Interaction (RDDI). The RDDI process can protect the excitation energy from dissipation through nonradiative relaxation channels, further enabling the extension of the lifetime of the excited state (Sajeev John and Tran Quang, xe2x80x9cPhoton-hopping conduction and collectively induced transparency in a photonic band gapxe2x80x9d, Physical Review A, Vol. 52, pp. 4083-4088, Nov. 1995). It is postulated that the collective properties of excited species of ordinary matter located in cavities within a PBG structure with inter-cavity separations less than the photon localization length "xgr" result in the occurrence of a new collective atomic steady state (a xe2x80x9cshadow crystalxe2x80x9d), the electromagnetic analog of a spin-xc2xd dipolar glass, and an associated Bose-glass state of photons in the cavity mode (Sajeev John and Tran Quang, xe2x80x9cQuantum Optical Spin-Glass State of Impurity Two-Level Atoms in a Photonic Band Gapxe2x80x9d, Physical Review Letters, Vol. 76, pp. 1320-1323, 19 Feb. 1996). Whereas researchers have considered these effects only for ordinary matter, the present invention extends these concepts to trapping and storing excited states of electrically neutral species of antimatter or exotic matter, in particular exotic matter in the form of excited positronium (Ps*). As defined herein, the term xe2x80x9cexotic matterxe2x80x9d refers to a mixture of normal matter and antimatter. The technique of this invention can be applied to excited states of antihydrogen (Ĥ), protonium (bound state of a proton and an antiproton), antimuonium (bound state of a positron and a negatively charged muon), molecular positronium (e.g., Ps2 and in general Psn), molecules containing positronium or positronium molecules bound to ordinary matter (e.g., PsH, CuPs, LiPs, etc.), and electrically neutral molecules containing a positron bound to ordinary matter having a single negative charge. Once the bound neutral antimatter or bound neutral exotic matter atoms are created in a PBG structure, it is well known that these atoms can be placed in the proper long-lived excited state using a laser tuned to a wavelength outside the bandgap (Quang et al., xe2x80x9cCoherent Control of Spontaneous Emission near a Photonic Band Edge: A Single-Atom Optical Memory Devicexe2x80x9d, Physical Review Letters, Vol. 79, pp. 5238-5241, 29 Dec. 1997) The proper long-lived excited state can also be achieved by creating the excited atom (e.g., Ps*) in a more highly excited state that cascades down to the proper excited state, from which further decay is inhibited by the surrounding PBG structure. Alternatively, the proper long-lived state can be achieved directly during the process for forming Ps*. For Ps*, the de-excitation mechanism known as the pickoff process can also be blocked by the PBG structure. In the pickoff process, a positronium atom in which the positron and electron have parallel spins (spin triplet: ortho-positronium) interacts with a nearby electron possessing spin opposite that of the positron. This results in a final state in which the positronium atom""s electron and positron have antiparallel spins (spin singlet: para-positronium). One of the periodicities in the PBG structure can be tuned to block the spin-flip transition associated with the pickoff process. By using active elements in the PBG structure, waveguides can be opened between the cavity or array of cavities and an exit aperture or exit apertures, and the species are channeled into the waveguides. While the excited species are traveling in the waveguides, the surrounding PBG structure continues to inhibit decay to the ground state (therefore preventing the subsequent annihilation from the ground state). As the excited species exit the structure, they are no longer blocked from decaying to the ground state. The species decay to the ground state and annihilate, releasing energy. The energy can be captured by an encompassing absorbing material, heating the material, and thermoelectric conversion processes can be used to produce electricity. Prior to their departure from the device, the electrically neutral excited species can be ionized by an electric field. This separates the electrically neutral species into positively and negatively charged ions. In the case of positronium, this separates each positronium atom into its constituent positron and electron. Electric and magnetic fields can then be used to direct the ions or antimatter and/or normal matter out of the PBG device and into the desired direction, forming a particle beam. As the beam of antimatter ions interacts with ordinary matter, annihilation occurs, a process useful for example as a drill or for ablation. The PBG trap has three key advantages over prior art neutral species traps (e.g., the Ioffe-Pritchard Trap, the Time-Averaged Orbiting Potential Trap, and the magnetic microtrap). First, in contrast with the Ioffe-Pritchard Trap and the Time-Averaged Orbiting Potential Trap, the PBG trap uses substantially less energy, weighs substantially less, and occupies substantially less volume. Second, in contrast with the Ioffe-Pritchard Trap and the Time-Averaged Orbiting Potential Trap, by using microcavities regularly spaced throughout a PBG structure the PBG trap stores electrically neutral antimatter or exotic matter in a scalable distributed manner, not in a non-scalable clump. Third, in contrast with the Ioffe-Pritchard Trap, the Time-Averaged Orbiting Potential Trap, and the magnetic microtrap, the PBG trap extends the lifetime of the trapped excited species by many orders of magnitude over the lifetime of the excited species when located outside the PBG trap. In contrast with prior art lifetime extension methods using externally applied crossed electric and magnetic fields or externally applied laser fields, the PBG trap provides a mechanism for capturing and storing large quantities of the excited electrically neutral species, and the PBG trap extends the lifetime of the trapped excited electrically neutral species by many orders of magnitude more than the factor of 20 achievable using the externally applied laser fields. It is to be understood that the present invention is not limited to the precise constructions herein disclosed and shown in the drawings, but also comprises any modifications or equivalents within the scope of the claims.