BRIEF DESCRIPTION OF THE DRAWINGS
These and other features and advantages will be better and more completely understood by reference to the following detailed description of exemplary illustrative embodiments in conjunction with the drawings, of which:
FIG. 1 is a schematic partial cross-sectional view of a conventional ion source;
FIG. 2 is a sectional view taken along section line II-II of FIG. 1;
FIG. 3 is a sectional view similar to FIG. 2, taken along section line II-II in FIG. 1, in another embodiment illustrating that the ion source may be shaped in an oval manner instead of in a circular manner;
FIG. 4 shows a stack of magnets used in a prior art magnet system;
FIG. 5 is a sectional view similar to FIG. 3, taken along section line II-II in FIG. 1, showing how the stacks of magnets included in the magnet system are disposed throughout the ion source;
FIG. 6 is a sample magnet in accordance with an example embodiment;
FIG. 7 is a sample lower yoke in accordance with an example embodiment;
FIG. 8 shows sample magnets placed on a lower yoke in accordance with an example embodiment;
FIG. 9 is an exploded view of magnets within a magnetic yoke in accordance with an example embodiment;
FIG. 10 is a view of a complete yoke assembly in accordance with an example embodiment; and,
FIG. 11 shows a complete yoke assembly being placed into an ion source in accordance with an example embodiment.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION OF THE INVENTION
Referring now more particularly to the accompanying drawings in which like reference numerals indicate like parts throughout the several views.
In certain example embodiments of this invention, the ion source is of the cold-cathode closed drift type, as shown in FIGS. 1-11. The magnet assembly of FIGS. 6-11 is usable in the ion source of FIGS. 1-5 in certain example embodiments, although the magnet assembly of FIGS. 6-11 may instead be used in other types of ion sources in other embodiments of this invention.
FIG. 6 illustrates a sample magnet 60 in accordance with an example embodiment of this invention. Magnet 60 as shown in FIG. 6 has a rectangular prism shape. One preferred set of dimensions for magnet 60 is 4.2×0.75×0.5″ although other dimensions may instead be used, and a source in certain example embodiments may include three such magnet 60. In certain example embodiments of this invention, the magnet 60 has a length which is at least twice as large as its width and/or height (more preferably at least three times as large, and possibly at least four times as large). It has been determined that the dimensions and numbers of magnets as disclosed herein tend to produce ion beams which may be diffused, collimated or focused as desired. The dimensions, numbers and/or chemistry of the magnets may be varied to change the ion beam produced, as required by, for example, the particular application for which the ion source is being used.
An example advantage of magnet 60 shown in FIG. 6 relates to its simple design. More particularly, magnet 60 is more basic and easier to produce than are the stacks of magnets forming a cylinder conventionally required. The simpler design of magnet 60 reduces difficulties during the machining of the magnets and when creating the bores. The rectangular prism shape of the magnet 60 also reduces the amount of material lost during machining, compared to the cylindrical shapes of the conventional systems. Thus, costs can be reduced because of, for example, the reduced amount of material required for, and reduced amount of waste resulting from, the machining of the magnets and bores.
Rather than boring a large number of holes as shown in FIGS. 4-5 and depositing stacks of magnets therein, certain example embodiments provide a yoke system configured to hold a smaller number of larger magnets of the type shown in FIG. 6. More particularly, FIG. 7 illustrates a sample lower yoke 70 in accordance with an example embodiment of this invention. Lower yoke 70 may be configured to receive three magnets like magnet 60, although the number and/or shapes of the magnets may vary in different embodiments of this invention. For purposes of example and without limitation, an example set of dimensions for lower yoke 70 is 12.838×0.752×0.548″. However, it will be appreciated that both the dimensions of the yokes and magnets are provided by way of example and without limitation, and either or both may be varied in different embodiments of this invention. The yokes may be made out of 1008 mild steel in certain example embodiments of this invention, although other materials may instead be used in certain other instances.
Between and abutting each magnet 60, screw plates 72a, 72b having screw holes 74a, 74b may be provided. For purposes of example only and without limitation, the screw plates 72am 72b may be about 0.392″ wide in certain example instances. Additionally, the screw plates 72am 72b may be slightly raised relative to the main part of yoke 70. Thus, small, well-defined areas are formed into which each magnet 60 may be placed as shown in FIGS. 7-8. In certain example embodiments, an additional screw plate may be provided at one or both of the outer ends of lower yoke 70 and/or the upper yoke.
The substantially rectangular magnets 60a, 60b, 60c may be cemented in and/or adhered, glued, or otherwise connected to the yokes as shown in FIG. 8 using any suitable material. In particular, FIG. 8 shows magnets 60a-c placed on a lower yoke in accordance with an example embodiment of this invention, between and/or adjacent plates 72a, 72b. The three simplified magnets 60a-c are placed in areas delineated by one or more plates 72a, 72b.
FIG. 9 is an exploded view of magnets within a magnet yoke in accordance with an example embodiment of this invention, and FIG. 10 is a view of a yoke assembly 1000 in accordance with an example embodiment of this invention. FIG. 11 shows yoke assembly 1000 being placed into an ion source in accordance with an example embodiment of this invention. As perhaps best shown in FIG. 11, the complete yoke assembly 1000 may be placed in the ion source in a single bore 27 in the area where the bores 27a-f conventionally were located so that the yoke assembly 1000 is surrounded by the anode 25 as viewed from above. For existing ion sources, this area may be completely machined out so that the magnets and/or yoke assemblies may be inserted therein for retrofitting. For new ion sources, a large recession or bore 27 may be formed so as to receive the magnets and/or the yoke assembly 1000. In certain example embodiments, the bottom of the inner cathode may rest on top of the upper yoke. In certain example embodiments, the area receiving the yoke assembly may be thought of as a single, large bore 27.
FIG. 9 and FIG. 10 illustrate lower yoke 70a and upper yoke 70b. Upper yoke 70b may be constructed similar to lower yoke 70a as described above in certain example embodiments of this invention. Magnets 60a-c may be adhered to upper yoke 70b similar to the process used for adhering them to lower yoke 70a, as described above.
In certain example embodiments, screw or other fastener plates 72a, 72b and screw or other fastener holes 74a, 74b in lower yoke 70a may differ from screw or other fastener plates 78a, 78b and screw or other fastener holes 76a, 76b in upper yoke 70b. In certain example embodiments, screw plates 72a-b and screw holes 74a-b in lower yoke 70a may be threaded, whereas screw plates 78a-b and screw holes 76a-b in upper yoke 70b may not be threaded. Bolts (not shown) may be fed through the upper holes 76a, 76b in a non-threaded manner, and threaded through the bottom holes 74a, 74b, respectively. This may help reduce problems (e.g. breakage, accumulation of dirt or debris, etc.) during shipment and installation. When the assemblies are installed, the bolts or other fasteners may be removed in certain example instances.
Having only one set of threaded screw plates and screw holes may be advantageous during removal of the yoke assembly. For example, once threaded through the holes, a bolt may push against the source, forcing the magnets and yoke assembly from the source. More particularly, to remove an installed assembly, when only the lower yoke has threaded holes, the bolts may push against the bottom of the source as they are turned, thereby pushing the full assembly out of the source. However, it will be appreciated that multiple sets of threaded screw plates and screw holes may be provided in certain embodiments of this invention.
Example embodiments disclosed herein provide several example advantages. In general, a single magnet yoke assembly including a number of magnets is easy to handle during initial installation. It also is easy to handle when the ion source is serviced, thereby resulting in improved efficiency. Thus, temporary removal and replacement of the magnet assembly may be easier than with certain conventional techniques. In certain example embodiments, only one large piece needs to be removed, compared to a large number of small, free-floating cylindrical magnets typical of conventional systems. Also, because the magnets may be cemented or otherwise adhered to one or both of the yokes, the magnets will not move around very much within the yoke, and the yoke will not significantly move inappropriately within the ion source. Thus, the chance of damage to the magnet(s) may be reduced. Also, the amount of foreign material and/or debris (e.g. small shards of broken magnets, dirt, and the like) becoming lodged between the magnets, the magnets and the yoke, and between the surface of the yoke and the other parts of ion source, may be reduced. As noted above, this is advantageous because it reduces both the chance of damage to the magnets as well as potentially adverse effects on the magnetic flux density (e.g. as caused by an air gap being formed by the debris). Reducing accumulation of debris also may reduce cleaning and maintenance requirements, saving time and/or money.
Although the example embodiments herein have been described as relating to multiple magnets being placed within a magnetic yoke, the invention is not so limited. For example, in certain example embodiments, the larger, simpler magnets may be placed in the ion source without the yoke. In certain other example embodiments, each ion source may include several yoke assemblies, with each yoke assembly include one or more magnets. According to such embodiments, the magnets within the yoke assemblies could be replaced with different magnets having different chemistries. Alternatively, or in addition, one or more pre-configured yoke assemblies may be provided to replace an entire yoke assembly. Accordingly, the resulting ion beam may be altered. For example, multiple yoke assemblies having different magnets included therewith could produce variable magnetic flux densities to change the resulting ion beam. In other example alternative embodiments, only one magnet may be used.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
Patent Application
20080048127
