US3832562A

US3832562A - Enhancement and control of radiation beams by vibrating media

Info

Publication number: US3832562A
Application number: US00323794A
Authority: US
Inventors: A Jacobs; E Kenney
Original assignee: Research Corp
Current assignee: Pennsylvania Research Corp; Research Corp
Priority date: 1971-02-22
Filing date: 1973-01-15
Publication date: 1974-08-27
Anticipated expiration: 1991-08-27

Abstract

Disclosed are apparatus and methods for controlling radiation, such as a beam of neutrons, low energy gamma rays, X-rays, or electrons, by means of successive diffractions by diffracting media, such as crystals, vibrating in a compression mode in a shear mode or in a complex superimposed vibrational mode. The radiation beam may be subjected to successive diffractions by an arrangement of such vibrating diffracting media and may thus be contained in a substantially closed path such as a hexagonal path or a figure-eight path. Alternatively, the radiation beam may be subjected to one or more diffractions by an arrangement of such vibrating diffracting media for the purpose of controlling the beam in a non-closed path.

Description

United States Patent Jacobs et al.

[45] Aug. 27, 1974 ENHANCEMENT AND CONTROL OF RADIATION BEAMS BY VIBRATING MEDIA [75] Inventors: Alan M. Jacobs; Edward S. Kenney,

both of State College, Pa.

[73] Assignee: Research Corporation, New York,

[22] Filed: Jan. 15, 1973 [21] Appl. No.: 323,794

' Related US. Application Data [63] Continuation of Ser. No. 117,647, Feb. 22. 1971,

abandoned.

[52] US. Cl 250/503, 250/396, 250/492,

[51] Int. Cl. G0ln 23/20 [58] Field of Search 250/396, 492, 503, 510

[56] References Cited UNITED STATES PATENTS 3,518,427 6/l970 Cotterill 250/5l0 OTHER PUBLICATIONS Diffraction of Neutrons and X-Rays by a Vibrating Quartz Crystal by A. G. Klein et al., from Applied Physics Letters, Vol. 10, No. 10, May 15, 1967, pgs.

Intensity of X-Rays Diffracted from an Elastically Vibrating Single-Crystal Plate by K. Haruta from Journal of Applied Physics, Vol. 38, No. 8, July, 1967, Pgs. 3,3l23,3l6.

Theory of X-Ray Diffraction by a Vibrating Crystal by M. Kuriyama et al., from Journal of Applied Physics, Vol. 40, No. 4, March, 1969, Pgs. 1,697l,702.

Primary Examiner-William F. Lindquist [57] ABSTRACT Disclosed are apparatus and methods for controlling radiation, such as a beam of neutrons, low energy gamma rays, X-rays, or electrons, by means of successive difiractions by diffracting media, such as crystals,

vibrating in a compression mode in a shear mode or in a complex superimposed vibrational mode. The radiation beam may be subjected to successive diffractions by an arrangement of such vibrating diffracting media and may thus be contained in a substantially closed path such as a hexagonal path or a figure-eight path. Alternatively, the radiation beam may be subjected to one or more diffractions by an arrangement of such vibrating diffracting media for the purpose of controlling the beam in a non-closed path.

25 Claims, 6 Drawing Figures FESONA T01? PAIENIEDmszmu sum 2 or 2 M- v K A mum, A m mmeu w Q QWQ kmwwwmvim o 338$ fix Q3 3 Hume k? Q Q 3 as r m%& mwsxmfi (E g ATTORNEY ENHANCEMENT AND CONTROL OF RADIATION BEAMS BY VIBRATING MEDIA This is a continuation, of application Ser. No. 117,647, now abandoned, filed Feb. 22, 1971.

BACKGROUND OF THE INVENTION The invention relates to apparatus and method for controlling radiation beams, and relates more specifically, to employing vibrating diffracting media such as crystals to control radiation beams by containing, enhancing, and localizing the beams. The term containing refers in this specification to causing a radiation beam to travel in a substantially closed path, such as a hexagonal or figure-eight path, such that more radiation can be added to the beam in the closed path, with the result that the intensity of the beam traveling in the closed path can be increased. The term enhancing refers to increasing the intensity of a diffracted beam over the intensity possible if the same beam is diffracted from a conventional diffracting medium such as a stationary crystal. The term localizing refers to a process similar to focusing a beam of light, i.e., to a process increasing the beam intensity gradient in a plane perpendicular to the beam path.

Highly collimated and localized radiation beams are desirable for uses such as localized tissue destruction for medical treatment and surgery, localized high intensity ionization for the purpose of modifying material properties, radiography techniques using penetrating radiation, and production of isotopes. It has been difficult, and in some cases impossible, to generate such beams by prior techniques. Ordinary optical lenses are generally incapable of controlling radiation which has shorter wave length that does not permit the degree of refraction possible with the visual spectrum radiation. While certain types of radiation such as charged particle beams are susceptible to control by means of electromagnetic fields, many other types of radiation, such as neutron or photo beams, do not have chargedparticle attributes and are not affected by electromagnetic fields.

Reflection of radiation, and particularly of neutron beams, is possible by coherent scattering (i.e., diffraction) by suitable crystals under suitable conditions. However, the mosaic microcrystal structure of even the most carefully prepared crystals yields a spread of the order of a minute of arc in the characteristic lattice vector direction of the diffracted beam. Diffraction of this type cannot be used to localize a beam of significant intensity or to contain a beam by multiple diffractions, because the spread of the diffracted beam results in a diverging beam with progressively lesser intensity per unit area of cross-section. It has been suggested that radiation such as X-ray radiation can be contained by providing a closed path defined by a plurality of Bragg reflectors (Cotterill, R., 1968, Appl. Phys. Letters, 12, 403). However, the loss rate in closed paths such as that shown by Cotterill would be intolerably high because of the spread in the diffracted beam.

It has also been suggested that the intensity of a diffracted beam of neutrons is enhanced if the diffracting crystal is a vibrating piezoelectric resonator (Klein, A., et al., Appl. Phys. Letters 10, 293). One interpretation of the phenomenon attributes the intensity enhancement to a substantial widening of the band of incident neutron volocities which satisfy the conditions for diffraction (Englehart, R., and Jacobs, A., 1969 Amer. Nucl. Soc. Trans. 12, No. 2, 520), while another interpretation attributes the phenomenon to diffracted sideband modification (Petrzilka, V., 1968, Czech. J. Phys. 18, 1,11 l The prior art relating to diffraction by a vibrating crystal does not suggest that it is possible to contain a radiation beam in a closed path defined by multiple diffractions, and does not suggest that it is possible to control and localize a radiation beam by means of a diffracting crystal vibrating in a shear (e.g., flexure) mode, or in superimposed vibration mode. Moreover, the prior art relating to diffraction by a vibrating crystal is completely confined to the quartz piezoelectric resonators and does not suggest that other motive techniques (e.g., magnetostrictive or externally driven media) will yield comparable or greater effects on the diffracted radiation beam.

SUMMARY OF THE INVENTION The invention relates to controlling radiation beams by means of multiple diffractions by vibrating diffracting media and by means of single or multiple diffractions by diffracting media vibrating in modes including shear (e.g., flexure) mode.

A radiation beam, such as, for example, a neutron beam including thermal neutrons in a defined energy range, is allowed to enter a substantially closed path defined by a plurality of diffracting media such as, for example, crystals, each crystal vibrating at a defined frequency and in a defined vibrational mode. The loss of a beam diffracted by a vibrating crystal is much less than the loss of a beam diffracted from a stationary crystal; hence, in the invented apparatus, a relatively high proportion of the neutrons which enter the closed path continue circulating within the path as more neutrons are added to the path from a source outside the path. The process results in a closed path containing a beam characterized by high radiation intensity and comprising substantially monoenergetic neutrons. This high intensity monoenergetic beam is directed at a target by selectively interrupting the closed path.

The closed path may be of various geometric shapes, such as a shape defined by a hexagonal arrangement of diffracting crystals or by a figure-eight arrangement of diffracting crystals. The diffracting crystals may be enclosed in a vacuum container to minimize undesirable particle interactions and to reduce vibration damping, and each of the diffracting crystals may be associated with means for spatially orienting the crystal with respect to the closed path for the beam, and with means for vibrating the crystal in a defined mode and at a defined frequency of vibration. In one particular embodiment, the vibrating crystals are enclosed in a vacuum container, with each crystal adjustable by an orientation vemier for proper spatial orientation with respect to the closed path of the beam. A master oscillator generates electrical signals used to vibrate the crystals, and adjustable phase shift drivers may be used to introduce phase differences between the several crystals that may be desirable to optimize parameters such as beam intensity. The closed path is interrupted by selectively A particular mode of vibration called flexure mode is used for the purposes of localizing a beam of radiation. In flexure mode, a diffracting crystal is caused to change alternately between a higher curvature and a lower curvature, of at least one of its faces, with the result that an impinging beam satisfying the diffraction criteria is diffracted primarily as a localized, or focused, rather than as a divergent beam. A diffracting crystal vibrating in flexure mode may be used to focus to a target the beam released from the closed path described above. Different vibrational modes may be used to define a particular closed path. A particular vibrational mode is flexure mode vibration superimposed on longitudinal vibration of the same crystal. The flexure mode is a special case of shear mode vibration.

The invented method and apparatus are useful with neutron beams as well as with beams of other radiation such as low energy gamma rays, X-rays and electrons.

An experimental arrangement including only two vibrating diffracting crystals is used for studying the effects resulting from varying parameters such as the nature of the diffracting crystal, vibrational mode, frequency of vibration, phase shift between the two diffracting crystals and angles of incidence of the beam.

The diffracting media may be caused to vibrate in the several useful vibrational modes by a variety of means, including piezoelectric means, sources external to the diffracting media, and magnetostrictive effect means.

BREIF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic block diagram of an arrangement for controlling a radiation beam by means of vibrating diffracting crystals.

FIG. 2 is a perspective view of a crystal vibrating in a compression mode of vibration.

FIG. 3 is a perspective view of a crystal vibrating in a flexure mode of vibration.

FIG. 4 is a schematic block diagram of a hexagonal arrangement of vibrating diffracting crystals serving to confine a radiation beam in a substantially closed path.

FIG. 5 is a schematic block diagram of an arrangement of vibrating diffracting crystals for confining a radiation beam in a substantially closed path.

FIG. 6 is a perspective view of a diffracting medium vibrated by means external to the medium.

DETAILED DESCRIPTION The invention relates to controlling radiation beams by means of successive diffractions by vibrating diffracting media, and by means of single or successive diffractions by diffracting media vibrating in modes including a shear mode. In the description below, the particular embodiment described in detail relates primarily to controlling neutron beam radiation, although it should be clear that the invented apparatus and methods are equally applicable to other types of radiation beams such as low energy gamma radiation, X-ray radiation and electron radiation. Similarly, the detailed description below shows only two geometric shapes for providing a closed path for a radiation beam. Again it should be clear that any other geometric shape defined by a plurality of vibrating diffracting media and containing a radiation beam in a substantially closed path is suitable.

The term diffracting medium is used in this specification to mean any medium, whether comprising a substance or fields, which is capable of diffracting in a radiation beam. One example of such medium is a substance having suitable crystalline structure and treated to be made capable of Bragg reflection (i.e., diffraction).

The experimental arrangement of FIG. 1 demonstrates some of the basic principles of the subject invention. In FIG. 1, a radiation source 10 may be a conventional nuclear reactor generating a radiation beam 12 which includes radiation in a defined energy range, such as thermal neutrons of the order of 0.01 eV. The beam 12 impinges on a diffracting medium such as a crystal 14 at an angle of incidence satisfying the criteria for diffraction and emerges from the diffracting crystal 14 as a diffracted beam 16. The diffracted beam 16 in turn impinges on a diffracting medium such as a crystal l8 and emerges therefrom as a diffracted beam 20 which is intercepted by a conventional radiation detector 22 designed to measure various characteristics of radiation beams such as beam intensity and energy distribution.

Each of the diffracting

crystals

14 and 18 may be a commercially available x-cut quartz crystal with a suitably treated surface to serve as a Bragg reflector. Other suitable crystalline substances may be used, as well as any other suitable medium capable of diffracting radiation beams and capable of being vibrated in specified vibrational modes either by utilizing inherent electromechanical properties, or by employing external mechanical driving agents. The diffracting

crystals

14 and 18 are supported by orientation verniers 24 and 26 respectively. The orientation verniers 24 and 26 provide for spatial orientation adjustments of the diffracting

crystals

14 and 18 respectively to assure that a beam 12 impinges on the crystal 14 at an angle of incidence within the range of angles of incidence at which Bragg reflection occurs, and to assure that the diffracted beam 16 impinges on the crystal 18 at an angle of incidence which allows Bragg reflection. Each of the diffracting

crystals

14 and 18 is under the influence of a vibrating means including an oscillator 28 which is connected directly to the diffracting crystal 14 for vibrating the crystal 14 at a specified frequency and in a specified vibrational mode, and is also connected to the crystal 18, but through an adjustable phase shift driver 30, for selectively causing the crystal 18 to vibrate at a phase displacement from the crystal 14, which phase displacement can be varied through a range including zero displacement. Vibrational motive forces other than the piezoelectric effect are suitable, e.g., mechanical, magnetostrictive.

The vibrating

crystals

14 and 18 may be the structures illustrated in FIG. 2 which show an x-cut quartz crystal 32 with its two parallel large faces connected to a modulated voltage source 33 to serve as a piezoelectric compression mode resonator. In a compression vibration mode, as illustrated in FIG. 2, the crystal 32 is caused, by means of modulated voltage potential applied across its large faces by the source 33, to contract and expand alternately along the indicated x-axis between the shape shown in solid lines and the shape shown in broken lines. Apparatus for causing compression mode vibration of x-cut quartz crystals is shown for example in Moyer, M. W. and Parkinson, T. F. 1968, Appl. Phys. Letters, 12, 403 and includes a signal generator driving a suitable high power amplifier whose output is connected to aluminum plates serving the dual function of holding the crystal and providing electrical contact with its large faces. It has been shown that a crystal vibrating in the compression mode illustrated in FIG. 2 intensifies a diffracted neutron beam. The mechanism which causes this desirable increase in intensity is not known with certainty; one explanation attributes it to widening of the energy band of incident neutrons which satisfy the diffraction criteria, while other explanation attributes it to a modification of the diffraction side band structure. The term compression mode vibration is defined herein to mean vibration of any diffracting medium which induces the medium to vibrate in a motion similar to that of the crystal 32 of FIG. 2.

FIG. 3 shows a shear vibrational mode defined as flexure mode vibration in which a crystal 34 is connected to vibration inducing apparatus similar to that described in connection with FIG. 2 but connected to cause flexure mode vibration, with the large face of the crystal 34 alternately changing between higher curvature of the face and lower curvature of the face, i.e., with the crystal 34 alternately changing between the shape shown in solid lines and the shape shown in broken lines. Vibrational motion of any diffracting medium similar to the motion of the crystal 34 of FIG. 3 is defined as flexure mode vibration and is a special case of a shear mode of vibration in which shear-type deformation is present. Depending on the parameters of the flexure mode vibration, such as type and degree of curvature and frequency, a flexure mode diffracting crystal can be caused to diffract a greater proportion of an incident beam than a stationary diffracting face, and to localize, or focus, the diffracted beam. Focal lengths of the diffracted beam of as little as on meter are possible. More complex modes of vibration, such as superimposed compression mode and shear mode vibrations are possible by establishing suitable potential fields across the large faces of an x-cut quartz crystal or by other suitable means. Other types of crystals capable of Bragg reflection can be used instead of the crystals shown in FIGS. 2 and 3. Other motive forces than the piezoelectric effect implicit in FIGS. 2 and 3 can be used. Other compression and shear modes than those indicated in FIGS. 2 and 3 can be used.

In the experimental arrangement of FIG. 1, the radiation source can be a conventional nuclear reactor generating, with the help of conventional collimators and with graphic or heavy water filter, a beam 12 including thermal neutrons of energy of the order of 0.0l eV. Each of the diffracting

crystals

14 and 18 may be a crystal such as the crystal 32 of FIG. 2 vibrating in the compression mode at a frequency in the kHz range, such as about 500 kHz, or such as the crystal 34 of FIG. 3 vibrating in the flex ure mode. The intensity of the diffracted beam 16 emerging from the vibrating diffracting crystal 14 can be of the order of 100 times greater than the intensity of the same beam after diffraction by a stationary diffracting crystal. The diffracting crystal 18 may similarly be a crystal such as the crystal 32 of FIG. 2 vibrating in the compression mode to generate the diffracted beam 20 which impinges on the radiation detector 22, or such as the crystal 34 of FIG. 3 vibrating in the flexure mode to localize, or focus, the diffracted beam 20. The radiation detector 22 may be of the type described in the Klein, et al., reference, supra.

In the case of compression mode vibration of the diffracting

crystals

14 and 18, the two crystals vibrate inphase when the phase shift driver 32 is adjusted to connect the output of the oscillator 28 to the diffracting crystal 18 directly and without phase change. Alternatively, a gradual shift may be introduced between the diffracting

crystals

14 and 18 by means of the phase shift driver 30 to determine the effects of the phase shift on the intensity of the beam 20 as detected by the detector 22 for the purposes of optimizing beam intensity.

A plurality of diffracting crystals, such as crystals of the types shown in FIG. 2 and in FIG. 3, can be arranged in a hexagonal array as shown schematically in F IG. 4 to contain a radiation beam by providing a closed path for the beam. A radiation beam 12, which may for example include thermal neutrons, originates at a radiation source 10, enters the hexagonal closed path defined by diffracting crystals 36a-f at diffracting crystal 36a, and is then confined to the hexagonal path by means of a multiplicity of successive diffractions. The intensity of the beam in the hexagonal path grows as more radiation from the source 10 enters the closed hexagonal path. The intensity of the beam in the closed path can be approximated by the following relation:

where, 1 is neutron flux intensity from a steady external neutron source such as a nuclear reactor which is initiated at time zero; 1 (2) is the neutron flux of the hexagonal path; 6 is the fraction of the neutron beam lost with each diffraction; r is the time interval between diffractions; and M is the multiplication factor of the hexagonal array of diffracting faces.

As an illustrative example, if the nominal speed of neutrons diffracted at the requisite 30 angle of incidence is 8X10 cm/sec, and the distance between any two successive diffracting crystals along the closed path is 8 centimeters, then the time interval 7 between the diffractions is I00 microseconds. In the case of the hexagonal path of FIG. 4 which has six diffracting crystals, the multiplication factor M is /ae. If e is assumed to be of the order of 10', then the multiplication factor of the arrangement shown in FIG. 4 would be about l,000,000, and the storage time necessary to achieve this asymptotic level would be several minutes.

A requirement for containing a neutron beam by successive multiple diffractions is that the parameter 6 remain small for all of the contained neutrons. If quiescent crystals are employed, 6 is a rapidly increasing function of the number of diffractions for any initial neutron velocity which satisfies the diffractions criteria when entering the closed path. However, if vibrating crystals are employed, then e maintains a relatively low value even after-many diffractions have occurred. The difference in the value of 6 between quiescent and vibrating crystals has been attributed to a widening of the acceptable range of neutron energy and direction which satisfy the Bragg condition. Applicants, however, do not wish to be boundto this or to any other theoretical explanation of the phenomenon.

The multiplication factor also depends on the phase synchronization of the individual diffracting crystals along the hexagonal path. As one example, all diffracting crystals can be vibrated at the same frequency, in the same vibrational mode and in phase with each other. As other examples, different crystals can be vibrated in different vibration modes at different frequencies, or additionally at different phase displacements.

To allow radiation to leave the closed path, one of the diffracting crystals of FIG. 4, for example, the diffracting crystal 36d, can be caused to selectively interrupt the contained beam. When the conditions for diffraction at the diffracting crystal 36d are not satisfied, as for example by suddenly changing the crystal vibration mode of crystal 36d, or by reorienting the diffracting crystal 36d such that the angle of incidence of the closed path beam is not within the range of angles of incidence resulting in Bragg reflection, then the contained beam is allowed to escape the closed path. The escaping beam can be directed to a suitable target, or it can be further controlled by means of a diffracting crystal 38 vibrating in the flexure mode to localize, or focus, the beam on a target 40.

A specific working embodiment of a plurality of diffracting crystals defining a closed path for a radiation beam is shown in FIG. where a vacuum container 42 encloses a pluraltiy of diffracting crystals 44a-f arranged to define a closed path in the general shape of the figure 8. The vacuum container 42 is for the purpose of allowing for reasonable Q values for the vibrating diffracting crystals 44a-f as well as for the purpose of allowing for very long mean free paths for radiation inside the container 42. The vacuum container 42 includes a vacuum port 46 for communication with conventional vacuum generating apparatus (not shown), and an injection port 48 for introducing radiation by a radiation source 10, enters the vacuum container 42 through the injection port 48, and then enters the figure 8 closedpath at the vibrating crystal 44a. Once in the closed path, the radiation beam travels repeatedly therein along the closed figure-eight path defined by successive diffractions from

crystals

44b, 44c, 44d, 44e, 44f and 44a, while more and more radiation from the source 10 enters the closed path at diffracting crystal 44a. The intensity of the radiation beam in the closed path can be expressed by a relation similar to that specified in conjunction with the closed path arrangement of FIG. 4.

In the arrangement of FIG. 5 each of the diffracting crystals 44a-f can be a crystal of the type shown in FIG. 2, or can be another suitable diffracting medium. Each of the diffracting crystals 44a-f is held in its proper place in the figure eight arrangement by a corresponding orientation vernier 46a-f. Each of the orientation verniers 46af also serves to allow for fine spatial adjustment of its corresponding diffracting crystal such that the conditions for diffraction for the closed path beam of radiation are satisifed at each diffracting crystal (i.e., the angle of incidence of the closed path beam at each one of the diffracting crystals 44af is within the range of angles of incidence which allow for Bragg reflection) and to assure that the beam is contained in an essentially closed path.

For the purpose of vibrating the diffracting crystals of the phase shift drivers 50b-f is adjustable to introduce phase displacement between its input and output signals ranging from zero to full cycle. If it is desired to vibrate different cyrstals at different frequencies or in different vibrational modes, each of the crystals may be coupled to an individual oscillator.

For the purpose of selectively allowing the closed path beam to leave the vacuum container 42, an orientation or vibrational mode switch 52 is used to change the orientation, or the vibrational mode, or both, of the crystal 44d such that the conditions for diffraction of the closed path beam of radiation are no longer satisfied at the diffracting crystal 44d. When the conditions for diffraction are not satisfied, no diffraction takes place at the diffracting crystal 44d and the beam diffracted from the diffracting crystal 44c leaves the vacuum container 42 through the exit port 43.

The beam leaving the vacuum container 42 through the exit port 43 can be allowed to impinge directly on a target, or it can be further controlled by means of a diffracting crystal 54 which may be a crystal of the type shown in FIG. 3. The diffracting crystal 54 is driven in flexure mode vibration by means of a flexure mode oscillator 56 to localize, or focus, to a target 58 the radiation beam leaving the vacuum container 42 through exit port 43.

In a particular example, the arrangement of FIG. 5 can be used to contain a selected portion of a beam of thermal neutrons generated by the radiation source 10 and each of the diffracting crystals 44a-f may be a crystal of the type shown in FIG. 2, with each of the crystals 44a-f vibrated at the same frequency (e.g., the natural frequencies of the crystals), with all crystals vibrating in-phase. An attempt may be made to optimize the intensity of the closed path beam of neutrons by introducing varying degrees of phase shift between the vibrating diffracting crystals 44a-f by means of adjusting the phase shift drivers 50bf.

As another example, one or more of the diffracting crystals 44a-f may be crystals of the type shown in FIG. 3 and vibrated in flexure mode to cause some localization of the closed path beam. Shear modes of vibration other than the flexure mode can be used alternatively.

As still another example, one or more of the diffracting crystals 44af and the diffracting crystal 54 may be vibrated in a complex mode of vibration which includes superimposed compression mode vibration and shear mode vibration.

The diffracting crystals 44a-f and 54 may be vibrated by a variety of means. One means for vibration is shown in FIGS. 2 and 3 and comprises conventional piezoelectric vibrations. Another means is shown in FIG. 6 and comprises and arrangement for mechanically inducing vibration in a diffracting crystal 62 which is mechanically coupled to an electromechanical driver 60 which may be a piezoelectric crystal or ceramic. The electromechanical driver 60 is driven into vibration by a conventional piezoelectric arrangement including a modulated voltage source 33. The advantage of the arrangement shown in FIG. 6 is that the diffracting crystal 62 may be vibrated at amplitudes greater than in the arrangements' shown in FIGS. 2 and 3 and that a greater variety of vibrational modes may be possible. Additionally, the face of the diffracting crystal 62 to which a radiation beam would be directed (i.e., the righthand face in FIG. 6) is left completely clear; the only contact with the external electromechanical driver 60 is through the opposite face of the diffracting crystal 62. The diffracting crystals 44af and 54 may still altematively be driven into vibration by magnetostrictive means, or by other conventional means.

We claim:

1. Apparatus comprising:

diffracting means including a plurality of diffracting media each capable of diffracting at least a substantial portion of a radiation beam impinging thereon under defined conditions;

means for vibrating each of said diffracting media in a defined vibrational mode and defined phase relationship with respect to each other; and

means for supporting the diffracting means with the diffracting media oriented with respect to each other to define a substantially closed path of travel for a radiation beam impinging on said diffracting media under said defined conditions for causing such radiation beam to recirculate along said sub stantially closed path a plurality of times by being diffracted at each medium toward a successive medium along said substantially closed path while retaining a substantial portion of its energy.

2. Apparatus as in claim 1 including means for introducing radiation into the substantially closed path defined by the diffracting media.

3. Apparatus as in claim 2 wherein the means for introducing radiation include means for generating and introducing into the substantially closed path a neutron beam including neutrons in a defined energy range.

4. Apparatus as in claim 2 wherein the means for introducing radiation include means for generating and introducing into the substantially closed path radiation selected from the group consisting of neutron radiation, low energy gamma radiation, X-ray radiation and electron radiation.

5. Apparatus as in claim 2 including means for selectively interrupting the closed path to allow radiation energy of the beam traveling along said substantially closed path to be released from the confines of the path.

6. Apparatus as in claim 5 wherein each diffracting medium has a defined orientation with respect to the closed path and a defined mode of vibration, and wherein the means for interrupting the closed path include means for selectively changing at least one of the orientation and the vibrational mode of a diffracting medium to inhibit diffraction of the radiation beam traveling along the substantially closed path by the last recited diffracting medium and to release thereby radiation from the substantially closed path.

7. Apparatus as in claim 1 including means for causing at least two of the diffracting media to vibrate out of phase with respect to each other.

8. Apparatus as in claim 1 wherein the means for vibrating include means for selectively causing at least one diffracting medium to vibrate in a vibrational mode including a flexure mode for causing focusing of radiation diffracted by the last recited medium and at least one other vibrational mode different from said flexure mode.

9. Apparatus as in claim 1 wherein said diffracting media are crystals. Y

10. Apparatus for controlling a radiation beam comprising:

means for generating a radiation beam including radiation in a defined energy range;

diffracting means comprising a plurality of diffracting media each capable of diffracting atleast a portion of an impinging radiation beam having radiation within said defined energy range, each diffraction resulting in a diffracted radiation beam;

means for supporting the diffracting means with the diffracting media oriented with respect to each other to form a substantially closed path of successive media wherein a radiation beam impinging on one diffracting medium is diffracted by it and impinges on the next successive medium, and a beam diffracted from the last medium of the succession impinges on the first medium thereof, and with the succession of diffracting media oriented with respect to the beam generating means to allow radiation generated thereby to enter said substantially closed path, said entering radiation providing a beam substantially confined within said substantially closed path and traveling repeatedly along the path; and

means for vibrating the diffracting media to enhance the diffractions thereby and to cause a net increase in the energy of the beam recirculating in the substantially closed path over at least a defined period of time including a plurality of recirculations.

11. Apparatus as in claim 10 including means for selectively interrupting said substantially closed path to allow the escape of radiation therefrom.

12. Apparatus as in claim 10 including means for selectively changing the orientation of a selected diffracting medium to inhibit diffraction thereby and to thereby selectively allow a substantial portion of the beam to leave the confines of said substantially closed path.

13. Apparatus as in claim 10 including means for selectively changing the vibrational mode of a selected diffracting medium to inhibit diffraction by the last recited medium of the radiation beam in said substantially closed path and to thereby allow escape of radiation from the path.

14. Apparatus as in claim 10 wherein the beam generating means include means for generating neutron radiation.

15. Apparatus as in claim 10 wherein the vibrating means include a master oscillator for generating a defined vibrational signal and means for applying said vibrational signal to each of the vibrated diffracting media for vibrating said media, the last recited means including an adjustable phase delay between at least two selected vibrating diffracting media.

16. Apparatus as in claim 10 including means for selectively interrupting the substantially closed path to allow radiation confined therein to escape therefrom as a released beam, and a target directing diffracting medium positioned in the path of said released beam for directing the released beam toward a selected target.

17. Apparatus as in claim 16 including means for vibrating the target directing diffracting medium to enhance the diffraction carried out thereby.

18. Apparatus as in claim 16 including means for vibrating the target directing diffracting medium to cause the last recited medium to concentrate the beam on a selected target.

19. Method of controlling radiation comprising:

confining a radiation beam within a substantially closed path defined by a plurality of diffracting media positioned in a succession in which each medium diffracts a beam impinging thereon toward the next successive medium. with the last medium of the succession diffracting the beam toward the first medium of the succession;

vibrating each of said media to enhance the diffraction of the beam thereby;

causing a beam introduced into the substantially closed path to travel along said path a plurality of times; and

adding radiation to the beam traveling along the substantially closed path for causing a net increase in the beam energy at least over a defined period of time including a plurality of recirculations of the beam along the substantially closed path.

20. Method as in claim 19 wherein the vibrating step includes vibrating at least two of said diffracting media out of phase with each other.

21. Method as in claim 19 including the step of selectively interrupting the substantially closed path to allow the escape from said path of radiation energy of the beam confined therein.

22. Method as in claim 21 wherein each vibrating diffracting medium vibrates in a defined mode of vibration and wherein the step of interrupting the substantially closed path includes selectively changing the mode of vibration of a selected medium to inhibit diffraction of the beam thereby and to thereby allow the escape of radiation from said substantially closed path.

23. Method as in claim 21 wherein each of the diffracting media has a defined orientation with respect to the remaining diffracting media, and wherein the step of interrupting the substantially closed path includes selectively changing the orientation of a selected diffracting medium to inhibit diffraction of the confined beam thereby and to thereby allow the escape of radiation from said substantially closed path.

24. Method as in claim 21 wherein the vibrating step includes vibrating at least one diffracting medium in a vibrational mode including a flexure mode for causing concentration of the beam diffracted by the last recited diffracting medium and including at least one other vibrational mode different from said flexure mode.

25. Method as in claim 19 including the step of selectively interrupting the substantially closed path to allow radiation confined therein to escape therefrom as a released beam and including deflecting the released beam toward a selected target and concentrating the released beam on said target.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,832,562 Dated Au ust 1974 v Inventor(s) Alan M. Jacobs and Edward S. Kenney It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the ABSTRACT, line, 5, insert a comma after "mode".

Column 2, line 41, delete "at" and insert to Column 3, line 32, delete "BREIF" and insert BRIEF Column 4, line 3, delete "in".

Column 5, line ll, delete "other" and insert another line 37, delete "on" and insert one line 51, delete "graphic" and insert graphite Column 6, line 28, the equation should read (t) M -[1 e 'r Column 7, line 34, after "radiation" insert into the container 42. A radiation beam 12 is generated Column 8 line 53, delete "vibrations" and insert --vibrators--;

line 54, delete "and" and insert anf Signed and sealed this 22nd day of April 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks FORM PC4050 uscoMM-oc scans-Pas;

i .5. GOVERNMENT PRINT NG GFFICE 2 "I, O-S-334

Claims

1. Apparatus comprising: diffracting means including a plurality of diffracting media each capable of diffracting at least a substantial portion of a radiation beam impinging thereon under defined conditions; means for vibrating each of said diffracting media in a defined vibrational mode and defined phase relationship with respect to each other; and means for supporting the diffracting means with the diffracting media oriented with respect to each other to define a substantially closed path of travel for a radiation beam impinging on said diffracting media under said defined conditions for causing such radiation beam to recirculate along said substantially closed path a plurality of times by being diffracted at each medium toward a successive medium along said substantially closed path while retaining a substantial portion of its energy.

9. Apparatus as in claim 1 wherein said diffracting media are crystals.

10. Apparatus for controlling a radiation beam comprising: means for generating a radiation beam including radiation in a defined energy range; diffracting means comprising a plurality of diffracting media each capable of diffracting at least a portion of an impinging radiation beam having radiation within said defined energy range, each diffraction resulting in a diffracted radiation beam; means for supporting the diffracting means with the diffracting media oriented with respect to each other to form a substantially closed path of successive media wherein a radiation beam impinging on one diffracting medium is diffracted by it and impinges on the next successive medium, and a beam diffracted from the last medium of the succession impinges on the first medium thereof, and with the succession of diffracting media oriented with respect to the beam generating means to allow radiation generated thereby to enter said substantially closed path, said entering radiation providing a beam substantially confined within said substantially closed path and traveling repeatedly along the path; and means for vibrating the diffracting media to enhance the diffractions thereby and to cause a net increase in the energy of the beam recirculating in the substantially closed path over at least a defined period of time including a plurality of recirculations.

19. Method of controlling radiation comprising: confining a radiation beam within a substantially closed path defined by a plurality of diffracting media positioned in a succession in which each medium diffracts a beam impinging thereon toward the next successive medium, with the last medium of the succession diffracting the beam toward the first medium of the succession; vibrating each of said media to enhance the diffraction of the beam thereby; causing a beam introduced into the substantially closed path to travel along said path a plurality of times; and adding radiation to the beam traveling along the substantially closed path for causing a net increase in the beam energy at least over a defined period of time including a plurality of recirculations of the beam along the substantially closed path.