US3310764A - Connection system for magnet excitation coils - Google Patents

Description

2 She ets-Sheet 1 March 21, 1967 R. A. KILPATRICK CONNECTION SYSTEM FOR MAGNET EXCITATION COILS Filed July 13, 1965 INVENTOR ROBERT A. KILPATRICK ATTORNEY.

March 21, 1967 R. A. KILPATRICK 3,310,764

CONNECTION SYSTEM FOR MAGNET EXCITATION COILS Filed July 13, 1965 2 Sheets-Sheet 2 A L A \k INVENTOR ROBERT A. KILPATRICK ATTORNEY.

United States Patent 3,310,764 CONNECTION SYSTEM FOR MAGNET EXCITATION COILS Robert A. Kilpatrick, Orinda, Calif., assignor to the United States of America as represented by the United States Atomic Energy Commission Filed July 13, 1965, Ser. No. 471,774 9 Claims. (Cl. 335213) The present invention relates to charged particle accelerators and more particularly to an improved Winding arrangement for the magnet excitation coils of particle accelerators of the type having a series of magnet sections spaced along the beam orbit thereof.

In particle accelerators such as the alternating gradient or so-called strong focussing proton synchrotron, the charged particles are directed along a closed path and the particle beam is confined to the desired beam envelope by means of a continuous series of alternate focussing and defocussing magnet sections which present opposite transverse magnetic field gradients to the beam. This method of beam control has proven very advantageous, as will hereinafter be discussed, and may be used on linear as well as closed orbit machines. The invention will be described with reference to circular machines sinceit was initially designed for use in this context.

The magnets for the focussing and defocussing sections are C-shaped in cross-section and essentially act as corresponding halves of a quadrupole. The magnets are disposed in a regularly alternating arrangement around the beam path with the spaced pole faces forming a vertical gap through which an elliptical beam aperture is defined. The pole faces of the focussing magnet sections diverge radially inward with respect to the beam orbit and thus the magnetic field strength across the gap increases in the radially outward direction. The pole faces of the defocussing magnet sections diverge radially outward and the magnetic field strength in these regions increases in a radially inward direction. This systematic reversal of the field gradients provides opposing alternate restoring forces to the beam whereby the particles are deflected radially inward during focussing and radially outward during dcfocussing. Similar to lens action in optics, the magnet sections perform alternate opposite convergences in the vertical plane, thereby confining the beam to the desired aperture size.

The alternating gradient concept of orbital stability has I led to significant economies in accelerator design. The strong focussing decreases the free oscillation amplitude of the particles thereby reducing the necessary beam aperture and substantially reducing the necessary magnet size for a given energy. The amount of magnet steel may be reduced by a factor of 100 from that required for comparable weak focussing magnets. An improved momentum compaction factor reduces the necessary dimensions of the pole faces to further reduce the magnet size, as well as reducing the energy stored in the field and the power required for excitation. It therefore becomes practical to cycle the magnets at much higher frequencies, thereby increasing the number of beam pulses per second and the time-average intensity of the beam. Consequent- 1y machines of much higher energies become feasible.

Due to the unavoidable limitation imposed by the magnetic permeability of iron, the increase in the maximum energy of these machines must be accompanied by an increase in the beam orbit radius. In fact, the alternating gradient technique itself requires a larger radius for a given energy due to a need for many fieldfree spaces between the focussing and defocussing sectors. Thus the more advanced machine designs are running to larger and larger orbital dimensions. For example, a 200 bev.

3,310,764 Patented Mar. 21, 1967 proton synchrotron is currently being designed. The subject invention was developed for this machine which will use 504 focussing and defocussing magnet sections arranged around an orbit approximately one mile in diameter.

Successful application of the alternating gradient concept requires nearly perfect beam-guiding fields within the magnet, and as the machines get larger the degree of precision required becomes relatively greater. The flux density precision requirements of the gradient magnets of the 200 bev. machine, for instance, have been estimated at 0.01%. Such nearly perfect beam-guiding fields thus impose comparable accuracy demands on the magnet excitation coil system and on the alignment of the successive magnet sections.

When dealing with magnets of the size used in these machines, the providing of magnet excitation windings, which must have a coolant circulating system incorporated therein, is not a simple technique of turning a wire around the poles but becomes a major fabricating operation in itself. In addition to the field accuracy requirements, practical problems of insulation, capacitance and the like present further difliculties.

The magnet coils are generally made up of layered subassemblies of essentially rectangular copper conductor. Each layer contains a portion of the turns required for the particular pole, disposed in a single plane from an outermost turn to an innermost turn. The layers are appropriately interconnected and stacked to form the total coil assembly for that pole. In order to have an integral number of turns on a coil, which is necessary for the sake of magnetic field symmetry, both terminals of the coil assembly occur at the same circumferential point with respect to the magnet pole. Thus in the past, the coil terminals have necessarily been at the same end of each magnet section and connection between adjacent sections has necessitated bus bars running parallel to the outside of the magnet section itself. Since the long dimension of the magnet sections lies in the direction of the particle path, this doubling back represents a significant amount of repeated conductor length and adds substantially to the power usage.

In elfect, this has required an extra length of conductor at least equal to the circumference of the accelerator. More often, two separate winding circuits carrying oppositely-directed currents are used on each magnet section. This requires two lengths of copper bar essentially encircling the circumference of the beam tunnel. In view of the increasingly greater physical dimensions being considered for such accelerators, the'amount of extra copper becomes substantialapproximately 6 miles of 3 sq. in. conductor would be required for the proposed 200 bev. machine. In addition to the cost of this amount of copper conductor material, these external connections must be accommodated by a larger tunnel cross-section than would otherwise be necessary, which in itself represents a significant cost increase in the larger machines.

In view of the'foregoing it is highly desirable to have an improved magnet excitation coil design which reduces the accelerator construction costs and which simplifies the fabrication and assembly of the numerous magnet coils.

The subject invention takes advantage of the reduced magnet energy requirements and the improved power distribution of the alternating gradient machines to introduce a radical departure from the previous magnet coil design. The invention enables adjacent magnet windings to be coupled directly end-to-end without sacrifice to the magnetic field symmetry or significantly adding to the insulation problems.

Whereas conventionally each coil has been composed of a single one of the two winding circuits used in the machine, the present design employs a partial turn of both circuits on a single coil to make up the required integral number of turns thereon and to lead the windings oil in the direction of the subsequent coil. The combined Windings are systematically alternated among the magnets tocompensate for any current imbalance between the two circuits and the partial turn placement is critically prescribed to have negligible effect on the aperture field.

It is accordingly an object of this invention to reduce the cost of charged particle accelerators, particularly very large machines of the alternating gradient class.

It is another object of this invention to provide an improved magnet excitation coil design for charged particle accelerators in which the coils of successive ones of the magnet sections can be connected together at the adjacent ends thereof.

It is a further object of the invention to provide an excitation coil design and coil connection system for the magnet of a charged particle accelerator of the synchrotron type which requires no external bus bar coupling between the magnet sections.

It is still another object of the invention to provide a connection system for the magnet excitation coils of a charged particle accelerator which allows a reduction in the size of the accelerator beam tunnel.

It is another object of this invention to provide for direct end-to-end coupling of successive magnet excitation coils in an alternating gradient type of charged particle accelerator.

It is a further object of the invention to provide a magnet excitation coil winding and connection system which is relatively convenient to assemble and install in a strong focussing type of charged particle accelerator.

The invention, both as to its organization and operation, together with further objects and advantages thereof will be best understood with reference to the following specification taken in conjunction with the accompanying drawing of which:

FIGURE 1 is a plan view showing a portion of an alternating gradient proton synchrotron including several of the individual magnet sections,

FIGURE 2 is a cross-sectional view of a magnet section taken along line 22 of FIGURE 1,

FIGURE 3 is a section view taken along line 3-3 of FIGURE 2 showing an excitation coil winding of one of the magnet sections, and

FIGURE 4 is a schematic diagram of the excitation coil windings and connections for the series of accelerator magnets of FIGURE 1.

Referring now to FIGURE 1 there is shown one alternating gradient sequence of the accelerator ring 11 of a charged particle accelerator of the synchrotron class. As the accelerator is a very large machine, the curvature of the beam orbit would be barely perceptible in the segment shown and has therefore been increased in FIG- URE l for purposes of illustration. Each alternating gradient sequence of the accelerator ring 11 includes four long beam-guiding magnet sections 12, 13, 14 and 15, disposed in succession along the tubular charged particle beam vacuum chamber 17. The magnets 12, 13, 14 and 15 are rectilinear, the gradual curvature of the beam orbit 18 being obtained by a slightly angled placement of each successive magnet with respect to the preceding one.

As can best be seen in FIGURE 2, the four gradient magnets 12, 13, 14 and 15 have a laminated C-shaped core 19 with the pole faces 21 being symmetrically divergent away from the magnet center to form an outwardly widening gap 22. The magnet 19 constitutes one half of a quadruple and, as such, the essentially hyperbolic profile of the pole faces 21 provides a uniform magnetic field gradient along both the horizontal and vertical directions of the gap 22. The vacuum tubulation 17 extends through gap 22 and is of elliptical cross-section, with the major axis being horizontal, to conform with the ion beam profile.

The first magnet pair 12 and 13 serve as a focussing section to the ion beam 18 and are disposed with the back legs of the magnet cores 19 radially outward on the accelerator ring 11. By virtue of the tapered gap 22, the magnetic field gradient increases outward across the gap in this section and produces an inward horizontal restoring force on the beam 18. The second magnet pair 14 and 15 are disposed with the back legs radially inward on the ring 11 and form a defocussing section to the beam 18. In this position of the magnets 14 and 15, the field gradient is reversed across the gap 22 and produces an outward horizontal restoring force to the beam 18. These restoring forces, of course, are superimposed on the main, circumferentially constant beam-bending field which is provided by both the focussing and defocussing magnets. The pattern of the two focussing magnets 12 and 13 and two defocussing magnets 14 and 15 is continuously repeated throughout the accelerator ring 11 to provide the systematically alternating magnetic gradient along the charged particle path 18, thereby confining the particle beam to the desired envelope size. It should therefore be understood that the remarks herein directed to magnets 12, 13, 14 and 15 are not limited thereto but pertain to all the alternating gradient magnet sections of the accelerator.

Referring now to FIGURES 2 and 3 together for an understanding of the coil structure for the magnets 12, 13, 14 and 15, two excitation windings 23 are shown separately encircling the upper and lower poles respectively of the magnet core 19. The windings 23 are each composed of two coil layers 24, each of which layers 24 is a rigid pre-formed subassembly, thin enough to be separately inserted through the narrow magnet gap 22. The coils are formed of a hollow conductor 26 having a rectangular cross-section, through the inner passages 27 of which coolant liquid is circulated. Insulation 28 is provided between the turns of a coil layer 24 and a ground plane insulation envelope 29 encases each layer. The two coil layers 24 are assembled on each magnet pole and are interconnected at the inermost turn by an electrical terminal 31 and a water fitting 32. The placement of terminal 31 and of outer terminals 30, 33 and 34 for coupling to other coils 23 will presently be described in connection with the winding pattern of the coils. The leg of the coils 23 which extends through the center of the magnet cores 19 is known in accelerator art as the coil window and, as can be best seen from FIGURE 2, this portion of the coil has the greatest effect on the beam aperture field. The outer portions of the assembled coils 23 are held in a suporting frame 40, mounted by angle members 45 to the longitudinal tie bars 50 of the laminar magnet core 19 structure. As an indication of the physical proportions and material quantity involved in such magnet excitation systems, the abovedescribed coil assemblies 23 exceed 20 ft. in length and approach a weight of 2 tons apiece.

Referring now to FIGURE 4, there is shown a schematic diagram of the coil 23 winding patterns for each of the four magnets 12, 13, 14 and 15. The graphic arrangement of the windings shown in the schematic is meant to represent, as nearly as possible, the spatial arrangement of the corresponding coils as shown in the view of FIG- URE 1. The winding patterns for each of the coil layers 24 are shown to lie in separate planes with the two layers of each coil assembly 23 in vertical proximity. The coil window leg of the windings is indicated in this figure by solid encirclements 35, and the particle path 18 is shown in the space between the paired winding layers for the respective upper and lower poles of the magnets 12, 13, 14 and 15. Coupling terminals between the coil layers 24 of a single magnet are shown in the schematic as solid dots and the coupling terminals between the coils 23 of successive magnets are shown as open dots.

As was described earlier, the entire accelerator magnet winding circuit is composed of two members, one being the series return circuit of the other, whereby the currents carried therein are oppositely directed and essentially The paths of the twocircuit memequal in amplitude. bers are indicated in the drawing by the solid line 36 and the dashed line 37, respectively. This conventional use of two circuits reduces the total energy and coupling between the magnet circuits and the instrumentation wiring. For various reasons, however, such asdistributed current leakage through water passages, capacitance losses to ground, or possible non-uniform ripple currents, the two circuits do not necessarily balance exactly. Since the magnetic flux density precision requirements of the gradient magnets are so critical, the geometry of the subject winding pattern is arranged to minimize, or virtually eliminate, the effects of the possible current imbalance between the two circuit 36 and 37.

It should be noted that the current direction through the coil window legs 35 of the focussing magnet pair 12 and 13, as shown by the arrow heads, flows opposite to the direction of beam path 18 and that of the defocussing magnet pair 14 and 15 flows parallel to the beam path, as required by the accelerator design. Therefore, .the winding pattern of the to oppositely-directed current circuits 36 and 37 as used throughout both the focussing and defocussing magnet sections must, first of all, satisfy this condition. The imposed condition of the improved winding pattern of the subject invention is that all magnet coil 23 connections be made directly between the adjacent ends of successive magnets while maintaining an equal number of turns in all of the coils 23. ample each coil 23 is composed of eight turns.

Considering now the coil winding patterns for the four successive magnets 12, 13, 14 and 15, with the aforementioned requirements in mind, a coil terminal 38 of the solid line circuit 36 is shown at the bottom coil layer 12c of the upper pole of first focussing magnet 12. Layer 120 is composed solely of four turns of circuit 36 and is coupled at the innermost turn thereof to the innermost turn of its adjacent top coil layer 12b, the junction point 39 for such inter-layer connection corresponding to terminal 31 of FIGURE 3. Circuit 36 continues in the same direction from junction 39 to form only the main portion of top coil layer 12b, namely the three innermost turns and an additional partialturn through the coil window leg 35 thereof, to an upper coil terminal 41. All turns through the coil window leg 35 of the upper pole coil assembly 23 of the magnet 12 are thus composed of circuit 36. In the subassembly structure of FIGURE 3, coil terminal 33 corresponds to terminal 41 of layer 1212.

Referring again to FIGURE 4, the solid line circuit 36 is subsequently led to the bottom coil layer 13b on the lower pole of second focussing magnet 13. The circuit 36 similarly forms the main portion of this coil layer with the additional partial turn thereof along the coil window leg 35. The innermost turn of bottom coil layer 13b couples directly to that of top coil layer 13c, all four turns of which are made of circuit 36. A terminal 42 brings circuit 36 to the top coil layer 14a of the upper pole of the first defocussing magnet 14, whereupon the current direction through the COil Windows is reversed. The four turns of coil layer 14a are composed entirely of circuit 36, and the circuit is coupled directly through to all four turns of the adjacent coil layer 14d. From layer 14d, the circuit 36 is directed to the lower pole of the same magnet 14, to the bottom coil layer 14b thereof. The circuit 36 forms only a partial turn of this coil layer 14d by passing around the outer legs of the winding and avoiding the coil window leg thereof. The circuit 36 is continued at the terminal 43 of the top coil layer 15b on the upper pole of second defocussing magnet 15 where it similarly forms only an outer partial turn of the layer 15b. From layer 155 the circuit 36 is led to the lower pole of magnet 15 where it forms both coil layers 15d and 15a thereof. At coil terminal 53 of the last coil layer 15a, the circuit 36 is directed to a similar subsequent sequence of magnets and this In the presentex- 6 winding pattern is repeated at the corresponding first coil terminal 38 thereof.

The winding pattern of the dashed line, oppositelydirected current circuit 37 can be seen in the schematic to be complementary to that of circuit 36. Fromthe coil terminal 44 on magnet 15, the circuit 37 forms all of coil layer 15c and forms the major remaining portion of adjacent layer 15b to a coil terminal 46. Thus the window leg ofthe upper pole coil assembly of magnet 15 contains only this circuit 37. This pattern is repeated on the lower pole winding of magnet 14 wherein the coil window of this magnet pole is composed of only circuit 37. The circuit 37 is continued at terminal 47 to the upper pole of focussing magnet 13 where it forms the adjacent coil layers 13a and 13d thereof. The circuit 37 is subsequently led to the lower pole of magnet 13 and forms the outer partial turn of the magnet layer 13b. From coil terminal 48 on magnet 12, the circiut similarly forms a partial turn around the top layer 12b thereof and then goes to the lower pole of this magnet where the circuit forms adjacent coil layers 12d and 12a. From the coil terminal 49 of bottom layer 12a, the circuit is directed to the corresponding terminal 44 of the second defocussing magnet of a preceding four magnet sequence and the winding pattern is repeated therethrough.

In view of the foregoing description, it can be seen that although the two winding circuits 36 and 37 are not balanced within a single magnet, they are exactly balanced Within the coil window portions 35 of themagnet. The imbalance in the outer region of the winding has only a negligible effect on the beam aperture field. However, this imbalance condition in turn is staggered from the upper to the lower poles of the magnets and is alternated between the first and second magnets of the two magnet pairs in such a way as to cancel out within the total accelerator ring.

By Virtue of the systematic distribution of the two circuit 36 and 37 combinations among the four magnet positions, it can further be seen that the total winding pattern essentially constitutes a geometrical arrangement of four basic coil layer types a, b, c and d. Each layer type a, b, c and d is distinguished by the kind and the placement of the terminals thereon and by the presence or absence of a partial turn feed-through member. All the layer types are included in each of the four magnet windings, but the physical orientations of each type are either mirrored or reversed among the four magnets.

Thus, for example, coil layer type b is seen to be the subassembly structure shown in FIGURE 3. Only layer type b has the outer partial turn feed-through member, the terminal 30 of which in FIGURE 3 corresponds to the solid dot type'connection in the schematic FIGURE 4 for coupling to the layer type d or" the-same magnet. The opposite leg of the feed-through member extends further out from the winding and the terminal 34 thereat is of the open dot type for coupling to an adjacent magnet. The insulation 28 between the feed-through member and the neighboring turn is slightly increased to better isolate the two circuits appearing in layer b. The orientation of coil layer b shown in FIGURE 3 is the position it would have as used on magnet 14. On magnet 13 the position is rotated about a vertical axis; on magnet 15 the position is rotated about a horizontal axis; and on magnet 12 the position is rotated about both axes. It should be noted that the layer type b always occurs as an outside layer on the magnet poles to further diminish the possible effects of the partial turn imbalance. Similarly, layer type a is consistently used in the outside position and types a and d, and b and c are consistently paired on the magnet poles.

The four coil layer types a, b, c and d are thus fabricated according to their respective winding forms to provide four. corresponding types of coil layer subassemblies 24. The subassemblies are arranged in the proper orientations and the paired combinations thereof are assembled on the magnet core 19 to form the coils 23 on the upper and lower magnet poles. As can be seen in FIGURE 1, two connecting terminals for the two circuits 36 and 37 of the coil assemblies 23 appear at both ends of each gradient magnet and coupling between successive magnets is made directly between the adjacent ends thereof. In accordance with the schematic of FIGURE 4, between like magnets both terminals occur on either the upper or the lower pole coil assembly 23. (Only the upper pole terminals are indicated in FIGURE 1.) Between unlike magnets one terminal occurs on each of the coil assembies 23. Two short coupling bars 51 appropriately interconnect the coils 23 of the like magnet pairs 12 and 13, and 14 and 15, and two longer coupling bars 52 interconnect the coils between the focussing and defooussing magnet sections where the magnet position is reversed on the accelerator ring 11.

By eliminating the external bus bar connections running throughout the length of the entire accelerator magnet, as would be required with conventional coil winding techniques, the cost analysis of the 200 bev. accelerator for which the subject invention was designed indicates a savings of $200,000 in conductor material and $300,000 in accelerator tunnel space.

The above description has pertained to a particular accelerator design, however, it can be seen that other combinations of the two-circuit partial-turn winding technique are possible and would maintain the required symmetry of thewinding pattern. The concept is equally applicable to the excitation coils of other alternating gradient magnet system and combinations of magnets as well as to other magnet types, such as quadrupole and sextupole magnets.

Accordingly, it will be apparent to those skilled in the art that while the invention has been described with respect to a particular embodiment thereof, numerous variations and modifications are possible within the spirit and scope of the invention and thus it is not intended to limit the invention except as defined in the following claims.

What is claimed is:

1. In combination wit-h a plurality of magnets which are to be equally energized and each of which has a pair of spaced apart poles, a winding for each of said magnets comprising a first length of conductor extending from a first to a second end of said magnet and having at least one complete turn and one incomplete turn wound around a pole thereof in a first rotational sense, a second length of conductor extending from said first to said second end of said magnet and having an incomplete turn wound around said pole of said magnet in an opposite rotational sense, which incomplete turn is the complement of said incomplete turn of said first conductor thereon, and terminal means for connecting said first and said second lengths of conductor to the similar conductors of a preceding and a subsequent magnet at said first and second ends of said magnet.

2. In a charged particle accelerator of the class having a plurality of discrete magnet sections defining a charged particle orbit, each of said magnet sections having a pair of spaced apart poles which are elongated in the direction of said orbit, a winding for each of said magnet sections comprising a first length of conductor extending from a first to a second end of said magnet section and having at least one complete turn and one incomplete turn wound around a pole of said magnet section in a first rotational sense, a second length of conductor extendingf-rom said first to said second end of said magnet section and having an incomplete turn wound around said pole of said magnet section in an opposite rotational sense, which incomplete turn of said second conductor is the complement of said incomplete turn of said first conductor thereon, and terminal means for connecting said first and said second lengths of conductor to the similar conductors of a preceding and a subsequent magnet section at said first and second ends of said magnet section.

3. A charged particle accelerator as described in claim 2, wherein said terminal means connects said first and said 8 second lengths of conductor to the second and first lengths of conductor respectively of a preceding and a subsequent magnet section at said first and said second ends of said magnet section.

4. In a charged particle accelerator of the class having a plurality of discrete magnet sections defining the charged particles path of said accelerator, each of said magnet sections having a pair of spaced apart poles which are elongated in the direction of said charged particle path with one side of said poles forming a magnet coil window adjacent to said particle path, a continuous excitation winding for said plurality of magnet sections comprising a first plurality of coils disposed on alternate poles of successive ones of said magnet sections, each of said first coils having at least one complete turn and one incomplete turn wound around said pole in a first rotational sense, first coupling means connecting the terminal end of each of said first coils to the initial end of the subsequent one of said first coils between successive ones of said plurality of magnet sections, a second plurality of coils disposed on the same poles of said magnet sections as said first coils, said second coils having an incomplete turn wound around said poles in an opposite rotational sense to said first coil thereon which incomplete turn is the complement of that of said first coil, 9. third plurality of coils disposed on the opposite poles of said magnet sections from said first and second coils, each of said third coils having a complete number of turns wound around said pole in said opposite rotational sense, second coupling means connecting the terminal end of each of said third coils to the initial end of each of said seconds coils at said first end of each of said magnet sections, and third coupling means connecting the terminal end of each of said second coils to a subsequent initial end of the subsequent one of said third coils between successive ones of said magnet sections.

5. A charged particle accelerator as described in claim 4, wherein said incomplete turn of each of said first coils is wound along the side of said magnet pole which forms magnet coil window.

6. A charged particle accelerator as described in claim 4, wherein said complete number of turns of said third coil in each of said magnet sections is equal to the number of turns formed by said first and said second coils in said magnet section.

7. A magnet excitation winding system using two conducting circuits for a charged particle accelerator of the type having an alternating succession of focussing magnet pairs and defocussing magnet pairs defining the charged particle path, comprising a first coil type which first coil type includes one of said conducting circuits, and a second coil type which second coil type includes both of said conducting circuits, said first and second coil types being disposed on the separate poles of each of said magnets and arranged in a symmetrical pattern among the poles of each sequence of focussing and defocussing magnet pairs in said succession of said focussing and defocussing magnet pairs whereby the occurrence of said two conducting circuits is balanced within each of said magnet pairs and whereby the two conducting circuits of successive ones of said magnets may be coupled at the adjacent magnet ends.

8. A magnet excitation winding system as described in claim 7, wherein said first coil type contains (N /2) turns of said first conductor initiating at a first end of said coil and terminating at the opposite end of said coil, where (N) is a whole number, said first coil type also containing a complementary half-turn of said second conductor, and said second coil type contains (N) turns of said second conductor initiating and terminating at a first end of said second coil, one end of said second conductor of said second coil being coupled to the half-turn of said second conductor on said first coil type at said first end of said coils.

9. A magnet excitation winding system as described in claim 7, wherein. Said symmetrical pattern of said first and second coil types among the poles of said sequence of a focussing magnet pair and defocussing magnet pair is characterized by said first and said second coil types being separately disposed on the alternate poles of the alternate magnets within said focussing magnet pair, the 10ngi- 5 tudinal orientation of said first and second coil types on the second focussing magnet of said pair being the mirror image of those on said first focussing magnet of said pair, and the disposition of said first and second coil types and the respective longitudinal orientations thereof within said defocussing magnet pair being the mirror image of that of said first and second coil types Within said focussing magnet pair.

No references cited.

BERNARD A. GILHEANY, Primary Examiner.

G. HARRIS, Assistant Examiner.

Claims (1)

1. IN COMBINATION WITH A PLURALITY OF MAGNETS WHICH ARE TO BE EQUALLY ENERGIZED AND EACH OF WHICH HAS A PAIR OF SPACED APART POLES, A WINDING FOR EACH OF SAID MAGNETS COMPRISING A FIRST LENGTH OF CONDUCTOR EXTENDING FROM A FIRST TO A SECOND END OF SAID MAGNET AND HAVING AT LEAST ONE COMPLETE TURN AND ONE INCOMPLETE TURN WOUND AROUND A POLE THEREOF IN A FIRST ROTATIONAL SENSE, A SECOND LENGTH OF CONDUCTOR EXTENDING FROM SAID FIRST TO SAID SECOND END OF SAID MAGNET AND HAVING AN INCOMPLETE TURN WOUND AROUND SAID POLE OF SAID MAGNET IN AN OPPOSITE ROTATIONAL SENSE, WHICH INCOMPLETE TURN IS THE COMPLEMENT OF SAID INCOMPLETE TURN OF SAID FIRST CONDUCTOR THEREON, AND TERMINAL MEANS FOR CONNECTING SAID FIRST AND SAID SECOND LENGTHS OF CONDUCTOR TO THE SIMILAR CONDUCTORS OF A PRECEDING AND A SUBSEQUENT MAGNET AT SAID FIRST AND SECOND ENDS OF SAID MAGNET.

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