Abstract:
A charged particle analyzer electrode assembly of miniaturized physical size and photolithographic process element fabrication capability. The provided electrode assembly is made of conductive materials including semiconductor materials and metal materials. Individual electrodes in the assembly are made of for example plural layers of semiconductor or metal held in place by discrete insulator layers. Bandpass particle energy selection characteristics are achieved in the analyzer through a combination of analyzer particle path geometry configuration and the particle acceleration electrical potential selection. Selected particles are allowed to pass through the analyzer under these influences and non selected particles are excluded. Assembly of individual analyzer electrode assemblies into a multiple element analyzer array usable for example on an aircraft or spacecraft is included. Both millimeter sized and micrometer sized arrangements of the invention are contemplated.

Description:
RIGHTS OF THE GOVERNMENT 
     The invention described herein may be manufactured and used by or for the Government of the United States for all governmental purposes without the payment of any royalty. 
    
    
     BACKGROUND OF THE INVENTION 
     Charged particles including electrons and ions are often encountered in the technical laboratory as well as in space endeavors and other natural environments. In the former instance, ionized particles are for example used in many semiconductor device-processing arrangements including impurity implantations, surface cleaning procedures and small object viewings. In the latter instance, charged particles often appear in vehicle extraterrestrial environments, in vehicle propulsion arrangements and in other plasma related situations including for example the Aurora Borealis phenomenon. 
     An energy analysis of the electron and ion particles found in these situations is often desirable in order to offset or accommodate the effects of charged particles on sensitive equipment encountering the particles. This analysis has heretofore been accomplished by sizable elements establishing particle controlling electrical fields capable of steering received particles into a predictable trajectory with electronic lens elements. A charged particle electrode assembly or lens assembly built around a plurality of machined analyzer electrodes disposed with the use of conventional hardware, e.g. fastener hardware passing through the electrodes, has been used in the past for such charged particle electrode assemblies or lens assemblies. In the lens assembly particles of a given energy are steered to different physical locations depending on the speed and direction with which they enter the device. The analyzer electrodes may be disposed in a variety of different patterns, patterns comprising either an energy high pass apparatus or an energy band pass apparatus. As suggested in this paragraph, an attempt is made herein to use the word “assembly” in referring to charged particle energy analyzer electrodes or collections of these electrodes into a single charged particle energy analyzer and subsequently to use the word “array” in referring to a plurality of charged particle energy analyzers joined together in a common group. 
     Energy analysis of charged particles is thus typically performed by some form of an electrostatic lens, hence the term electrostatic analyzer. Various arrangements of electrodes produce electric fields in such a device so that particles of a given energy are steered through the device. The number of possible electrode configurations used to accomplish this process is myriad; nonetheless each of these configurations falls into the categories of high-pass devices, in which charged particles of less than a given energy are rejected and only those with energy greater than a certain threshold are passed, and band-pass devices in which a narrow range of particle energies Is allowed to pass through the analyzer while particles with energies outside this range, both on the high and low ends of an energy range, are rejected. The present invention charged particle energy analyzer falls into the second category of devices and is regarded as a band-pass energy filter device. 
     The shapes of electrodes used in a charged particle energy analyzer can be simple (e.g. cylinders, spheres, etc.) or complex; such electrodes are usually machined from metal using conventional machining techniques such as milling or lathe turning. The machining techniques applied often limit the degree to which the size of these electrodes can be reduced, as do the size of the fasteners, such as machine screws, used to assemble the electrodes. Some devices, notably the planar retarding potential analyzer, employ fine metal screens to establish electrostatic potentials. Such screens can be made relatively fine using electro-chemical milling, at the expense of their being fragile. The charged particle energy analyzer of the present invention however is arranged so that it can be made quite small without sacrificing its ruggedness or its precision. 
     SUMMARY OF THE INVENTION 
     The present invention provides a charged particle electrostatic analyzer electrode assembly capable of low cost, accurate, repeatable micro-sized realization. 
     It is therefore an object of the present invention to provide a charged particle energy electrostatic analyzer that is small in physical size and capable of use in aircraft, spacecraft or other confined locations. 
     It Is another object of the invention to provide a charged particle electrostatic analyzer having internal electrodes of accurately controlled physical dimensions. 
     It is another object of the invention to provide a charged particle electrostatic analyzer electrode assembly that can be accurately reproduced in any desired quantity. 
     It is another object of the invention to provide a charged particle electrostatic analyzer electrode assembly that is compatible with fabrication using integrated circuit technology. 
     It is another object of the invention to provide a charged particle electrostatic analyzer electrode array comprising a plurality of charged particle energy analyzer electrode assemblies and capable of low-cost, accurate, repeatable micro-sized realization. 
     It is another object of the invention to provide a charged particle electrostatic analyzer of increased measurement accuracy capability by way of having precisely located and sized component electrodes. 
     It is another object of the invention to provide a charged particle electrostatic analyzer having a laminated internal electrode structure. 
     It is another object of the invention to provide a charged particle electrostatic analyzer electrode assembly comprised of layers of doped silicon semiconductor material. 
     It is another object of the invention to provide a charged particle electrostatic analyzer comprised of stacked etched through silicon semiconductor material layers. 
     It is another object of the invention to provide a miniaturized charged particle electrostatic analyzer in which electric fields within the analyzer steer charged particles of a selected energy range between input and output ports of the analyzer. 
     It is another object of the invention to provide a miniaturized charged particle electrostatic analyzer in which electrical potential applied to one or more analyzer electrodes is used to control the particle energy filtering characteristics of the analyzer. 
     It is another object of the invention to provide a charged particle energy analyzer that is improved in certain ways over the analyzers disclosed in my prior U.S. Pat. No. 5,506,413 and 5,541,409; each of these prior patents is however incorporated by reference herein. 
     It is another object of the invention to provide a charged particle electrostatic analyzer in which miniaturized particle steering electrodes are used to enable reduction of the charged analyzer electrodes to the 50-100 nanometer physical size range. 
     These and other objects of the invention will become apparent as the description of the representative embodiments proceeds. 
     These and other objects of the invention are achieved by miniaturized charged particle plasma analysis apparatus comprising the combination of: 
     a first conductive material electrode having circular apertures photolithographically disposed therein; 
     a second conductive material electrode having slot apertures, selectively aligned with said first conductive material electrode circular apertures, photolithographically disposed therein; 
     a third conductive material electrode having photolithographically disposed slot apertures, selectively aligned with said first conductive material electrode circular apertures and said second conductive material electrode slot apertures, located therein; 
     said first, second and third conductive material electrodes being assembled into a multiple electrode plasma analysis stack of physically isolated electrodes wherein said second conductive material electrode is also electrically isolated from a common interconnection of said first and third conductive material electrodes; 
     a source of selected electrical potential connected between said second conductive material electrode and said common interconnection of said first and third conductive material electrodes; and 
     a particle collection electrode member located adjacent said third conductive material electrode and connected via a current measuring element with a particle collection energy source. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The accompanying drawings incorporated in and forming a part of the specification, illustrate several aspects of the present invention and together with the description serve to explain the principles of the invention. In the drawings: 
     FIG. 1 shows a representative scene in which the present invention charged particle energy analyzer may be useful. 
     FIG. 2 shows significant elements of a charged particle energy analyzer element electrode stack according to the present invention. 
     FIG. 3 shows a representative charged particle flow in a charged particle energy analyzer element according to the present invention. 
     FIG. 4 shows detailed elements of a charged particle energy analyzer array according to the present invention. 
     FIG. 5 shows charged particle energy analyzer elements disposed in a larger array device. 
     FIG. 6 shows the bandpass filter characteristics of a charged particle energy analyzer electrode stack. 
     FIG. 7 shows the relationship between beam electron energy and beam voltage in a charged particle energy analyzer electrode stack according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present charged particle energy analyzer invention allows a user to determine the energy of charged particles (e.g., ions and electrons) such as those found in laboratory plasmas and in the ionosphere. It uses electric fields, the configuration of which are determined by the geometry of the device&#39;s electrodes, to modify the trajectories of particles moving within the device. Only particles entering the energy analyzer with energies in a given range, proportional to the voltage applied to the device&#39;s inner electrodes, will be steered so as to exit the device. The charged particle energy analyzer thus operates as a charged particle energy filter. 
     The arrangement of the present charged particle energy analyzer is believed distinguished from other such devices in that the electrodes are not machined conventionally, but rather consist of patterned holes etched in thin sheets of conductive material, separated by thin sheets of an insulating material. A significant characteristic of this arrangement is that it is inherently adaptable to miniaturization. A variety of materials may be used in fabricating the electrodes. 
     The present invention charged particle energy analyzer is believed usable in a number of technical endeavors, including for example, measurement of ionospheric plasma in order to predict plasma impact on military and other satellite operations. The present device is also usable in the measurement of perturbations to the local space plasma environment in the vicinity of spacecraft using electric propulsion systems in order to assess and predict the effects of propulsion system function on spacecraft operations. The device may also be used in the measurement of plasma parameters in plasma processing systems in order to assess impacts on processing quality and to predict the inputs available for control loop operation. 
     FIG. 1 in the drawings therefore shows a scene in which a charged particle energy analyzer according to the present invention may be useful. In the FIG. 1 drawing a spacecraft such as the U.S. space shuttle craft  100  is shown to be approaching a region  104  of charged particles in the course of a return to earth  106  following a space mission. For present purposes it is assumed that the spacecraft  100  is yet disposed in a flight configuration allowing entry of charged particles from the region  104 , by way of an open port  102 , into a charged particle energy analyzer apparatus located within the spacecraft  100  but not shown in the FIG. 1 drawing. Subsequent closure of the port  102  or another arrangement precluding entry of earth&#39;s atmosphere reentry byproducts into the spacecraft and the charged particle energy analyzer apparatus is presumed in the FIG. 1 scene. Other uses of the present invention may of course intentionally collect charged particle samples originating in the atmospheric reentry sequence for use in the charged particle energy analyzer of spacecraft  100 . The relatively small size and weight penalties associated with a charged particle energy analyzer according to the present invention is notably useful in spacecraft and aircraft uses of the invention, especially in instances wherein smaller craft than the represented space shuttle  100  are involved. 
     FIG. 2 in the drawings shows the fundamental elements of a charged particle energy analyzer  200  made according to the present invention. As shown in this drawing the analyzer  200  consists of three stacked, conducting or semiconducting layers  202 ,  204  and  206  with patterns of holes and slots cut in each. These layers  202 ,  204  and  206  are separated by layers of insulating material, which for clarity are not shown in FIG.  2 . The patterns in each conducting layer  202 ,  204  and  206  are preferably etched into the material of the layer by photolithography. Such photolithographic etching is preferably used in both a semiconductor and a metallic (e.g. stainless steel) layer arrangement of the present invention. The photolithographic etching may be accomplished in the manner common in the semiconductor industry to fabricate integrated circuits and microelectromechanical systems (or MEMS) devices; additional details regarding such etching are included in the documents identified subsequently herein. 
     In the FIG. 2 charged particle energy analyzer the top electrode or plate  202  is patterned with a series of holes, while the middle and bottom electrodes or plates  204  and  206  are patterned with slots, the bottom plate slot being smaller in area than the slot of the middle plate; As is indicated by the dotted lines  216  in FIG. 2 the holes or apertures  212 ,  214  and  216  in the top plate  202  extend entirely through the plate  202  in substantially uniform cross section, a condition also indicated at  220  and  221  for the other plates in FIG. 2. A voltage V 1  (often ground potential, unless it is desirable to pre-accelerate particles in the device) is applied to both the top and bottom plates  202  and  206  by way of the leads  224  and  226 . A different voltage V 2  is applied to the middle plate  204  by way of the lead  228 . The sign of the voltage V 2  is chosen so as to be repelling to the species of charged particle under analysis (a negative voltage for electrons, a positive voltage for ions). Because the voltage V 2  is repelling, selected electron particles are steered through the FIG. 2 device by the electric fields within it. Only particles of a given kinetic energy level, entering within a certain solid angle, are steered from the entrance holes or apertures  210 ,  212  and  214  in the top plate  202  to the exit aperture  222  in the bottom plate  206  and thereby arrive at the particle collection electrode  208 . 
     The particle collection electrode  208  is operated at some additional voltage level V 3 , a voltage that is made to be attractive to the species of charged particle under analysis. The V 3  voltage is thus made to be positive for analyzing electron charged particles and negative for analyzing positively charged ion particles. A current measuring device as is represented by the meter  230  may be used to indicate the quantity of charged particles having the correct energy level and course of travel to reach the particle collection electrode  208 . In a refined embodiment of the invention the meter  230  may of course be replaced with a current sensing resistance or other current responsive element in order to process the current flow signal from collection electrode  208  electronically. The magnitude of the voltage V 3  is selected to assure capture of all charged particles exiting from the aperture  222  but small enough to be of little influence on particle kinetics; a voltage in the range of 10 V or greater is preferred. 
     FIG. 3 in the drawings shows a flow of selected charged particles being steered in the desired manner through the configured path of a prototype charged particle energy analyzer electrode assembly  301 . The flow  310  of charged particles shown in FIG. 3 enters one or more apertures  303  in the “top” plate  302  from the source  300 , traverses the aperture  312  in the middle plate  304  and the smaller aperture  316  in the lower plate  306  to finally reach the collection electrode  308 . The charged particles emerging from the aperture  316  in the FIG. 3 particle energy analyzer are of course those which entered the one or more apertures  303  with the appropriate combination of kinetic energy and charge so as to thread the path through the three apertures  303 ,  312  and  316  under the influence of the repelling potential applied to the middle plate  304 ; other particles are excluded from this select group and in fact primarily collide with one or more of the aperture  303 ,  312  and  316  or adjacent surfaces. This charged particle behavior in the FIG. 3 particle energy analyzer is in fact a demonstration of the bandpass energy filtering action of the present invention. The twisting and flow-shaping action of the particle stream  310  shown at  314  in FIG. 3 is representative of the mechanism achieving this electric field induced band-pass energy filtering action. 
     The plates  302  and  306  in the FIG. 3 charged particle energy analyzer are normally operated at the same electrical potential, usually ground potential, however in certain instances, wherein it is desirable to pre accelerate the particle under examination into or away from the FIG. 3 apparatus, it can be advantageous to operate one or more of plates  302  and  306  at some different potential. Grounded operation of plates  302  and  306  provides the additional advantage of human safety in operating and maintaining the charged particle energy analyzer. The surfaces of the three apertures  303 ,  312  and  316  in FIG. 3 are shown to be of a non planar or irregular texture because the etching process used in the prototype, namely etching of a metal such as stainless steel, leaves a non-planar edge on the etched holes and slots, as a result of undercutting by the chemical etchant during the etching process. As the FIG. 3 drawing implies, the charged particle energy analyzer configuration illustrated in the previously discussed FIG. 2 drawing is notional rather than being to scale. In reality the relative dimensions of the openings in each of the analyzer plates can be adjusted, within broad parameters, to tailor the acceptance energy range and acceptance angle of the present invention charged particle energy analyzer to specific applications. 
     Generally in order for the charged particle energy analyzer of the present invention to function most efficiently, the sizes of the entrance and exit apertures should be made smaller than the opening in the middle plate. The entrance and exit apertures are also radially offset in opposite directions, relative to the center of the opening in the middle plate, so that particles passing through the device undergo the “s-turn” trajectory depicted at  314 . Although It is not strictly necessary, it Is desirable to make the aspect ratio (the ratio of the length to the diameter or width of the opening) for both the entrance and the exit apertures of the charged particle energy analyzer large enough to preclude existence of a direct path through the device, a direct path that may be traversed by light or high-energy charged particles. 
     When a chemical etching process is used to pattern holes in metallic material-embodied plates for the charged particle energy analyzer the aspect ratio of a hole in any given metallic plate can be limited by etching restrictions to being less than one. In such a situation several individual patterned metallic laminations may be combined to form one or more plates in the analyzer in order to increase the effective aspect ratio of the assembled metallic plate. Such a plurality of laminations plate arrangement is shown in the drawing of FIG. 4 herein. A similar laminated plate arrangement may also be used when one or more of the plates in a FIG.  1  through FIG. 4 type charged particle energy analyzer assembly is fabricated from a semiconductor material such as Silicon. 
     FIG. 4 in the drawings therefore shows a cross-section of a fabricated charged particle energy analyzer  400  made according to the present invention using either semiconductor or metallic plate compositions. In the FIG. 4 drawing the top plate element appears at  402  and the middle plate at  406 ; in the FIG. 4 apparatus each of the plates are fabricated from either a metal such as stainless steel or a semiconductor material such as Silicon. In the FIG. 4 arrangement of the invention a stack of three individual photolithographically-etched laminations  4085   410  and  412  are used to assemble the middle plate  406 . This layered or laminated plate arrangement in fact provides the basis for the term “laminated” used in the title of the present patent document. Since the achievable aspect ratio of the openings in each layer shown in FIG. 4 is often limited by the etching technology several individual laminations are stacked together to achieve each of the FIG. 4 energy analyzer plates  406  and  416 . The plate  416  is the bottom plate in the FIG. 4 apparatus; as shown in FIG. 4 a stack of six laminations  415 ,  417   418 ,  419 ,  420  and  421  is used to assemble this bottom plate  416 . 
     Notably in a charged particle energy analyzer assembly fabricated from semiconductor or silicon laminations, as the FIG. 4 drawing herein may be considered to represent, higher lamination opening aspect ratios can also be obtained more expediently in each lamination by using, for example, plasma etching techniques and taking advantage of the crystalline structure of the semiconductor material itself. This may be accomplished by optimally orienting the lamination opening with respect to the crystal orientation of the semiconductor material while shaping an individual lamination or plate opening and thereby taking advantage of the known faster etching rates occurring in some directions of the semiconductor material. 
     Thin Teflon® or like material spacers appear at  404  and  414  in the FIG. 4 charged particle energy analyzer. A thick Teflon® spacer appears at  422  below the bottom plate of the FIG. 4 stack. The printed circuit (PC) board upon which the FIG. 4 analyzer is mounted appears at  424  in the FIG. 4 drawing. Metallization received on the PC board  424  appears at  437  and  438 ; this includes the top collector surface  440  corresponding to the collection electrodes  208  and  308  shown in the FIG.  2  and FIG. 3 drawings herein. This top collector surface  440  is connected to current multiplying and/or metering circuitry by way of the extended metallization at  438  which may include a plated-through hole or other top to bottom surface electrical connection as is represented at  439  in FIG.  4 . The portion of the of the printed circuit board at  426  remains electrically insulating in nature and may be used for analyzer mounting purposes. 
     The charged particle energy analyzer of the present invention can be fabricated singly or in analyzer arrays. The FIG. 4 drawing in fact shows an array of three such charged particle energy analyzer devices, the devices having upper plate openings at  428 ,  430  and  432  in FIG.  4 . Arrays larger than the FIG. 4 three-element array are of course possible and are desirable in for example natural phenomenon-related uses of the invention. The charged particle path for the centermost of the FIG. 4 analyzer assembly is indicated at  434  in the FIG. 4 drawing. The overall thickness dimension of the FIG. 4 analyzer array is indicated at 436 to be 2.4 millimeters. This 2.4 millimeters dimension is considered to represent a scaled-up embodiment of the invention that is convenient for initial concept and early development uses, uses in for example an academic environment where student assistance and less than state of the art fabrication facilities are most convenient. Refined versions of the invention, especially versions contemplated for use in space applications, and made according to later states of the semiconductor fabrication art, are viewed as desirably having an overall height dimension of 50 to 100 micrometers in lieu of this 2.4 millimeters. These refined versions are contemplated to include corresponding reductions of dimensions along the other two axes of the array. Individual charged particle energy analyzer assemblies according to this smaller array size are of course also contemplated to come within the scope of the invention. 
     FIG. 5 in the drawings shows a somewhat larger array  500  of charged particle energy analyzer devices etched into approximately 25 cm 2  of detector array surface; the FIG. 5 array includes a total to 1920 individual analyzer elements disposed in a 5 centimeter by 5 centimeter area. In the FIG. 5 drawing 120 individual analyzer elements are located in each of the illustrated 16 clusters  504 ; four such clusters are disposed in each horizontal row  506  and four clusters are disposed in each vertical column  508 . Twelve individual analyzer elements are located in each of the 10 rows of a cluster  504  in the FIG. 5 array. A twenty-five cent U.S. coin appears at  510  in the FIG. 5 drawing (which represents an actual photograph) for size reference purposes. The FIG. 5 drawing represents a Patent Draftsman&#39;s rendition of an actual photograph. Conventional current sensing electronics may be used to measure the charged particle current passing through the FIG. 5 charged particle energy analyzer; this is in lieu of a more complex charge multiplication scheme as may be advantageous with smaller array sizes. In instances where charge multiplication can be used, a single analyzer element stack or a small array of analyzer stacks can accomplish similar measurement to the larger array represented in the FIG. 5 drawing. 
     A charged particle energy analyzer may be tested by placing it in a highly monoenergetic beam of electrons and observing its response—that is, by measuring the current of electrons passing through the device as a function of the voltage applied to the middle plate electrode of the device. The results of such a test are shown in the drawing of FIG. 6 herein. The beam employed in the FIG. 6 test has a full width half maximum (FWHM) value of 0.66 eV for beam energies of 10-25 electron volts. Compared to the range of energies that the device will pass, this value is small, so that FIG. 6 accurately represents the response of the device. FIG. 6 presents the response normalized to the beam voltage. In other words, we would expect that if the beam voltage was set at 10 V, the device would have a maximum response with 7 V applied to the center electrode. If the beam voltage were 20 V, the maximum response of the device would be with 14 V applied, etc. The FIG. 7 drawing shows response of the charged particle energy analyzer as a result of this electron beam as a function of the voltage applied to the middle plate of the analyzer. As predicted, the charged particle energy analyzer operates as a bandpass energy filter. The tail of the FIG. 6 response for V app /V beam  being less than 0.5 is a result of the relatively wide entrance aperture chosen for the tested charged particle energy analyzer configuration, a configuration selected to increase sensitivity in detecting plasma depletions in the ionosphere. 
     Continuing with FIG. 6, this drawing thus shows the expected behavior of a band-pass energy filter for the tested charged particle energy analyzer; this response is strongly peaked at a given applied voltage i.e., at a ratio of applied voltage to beam voltage of about 0.75 in the case of the tested charged particle energy analyzer geometry. The drawing of FIG. 6 shows the response of the device with the applied voltage normalized to the beam energy. The FIG. 6 relative response is the same over a wide range of beam energies, meaning that the response of the device is linear with the applied voltage. This linear response is shown in the relationship of the FIG. 7 drawing. 
     FIG. 7 shows that the response of the present invention analyzer to various energy electron beams is linear, as appears In this plot of the beam voltage versus the applied voltage at which the detector response is maximized. The analyzer constant of this configuration is 1.35. In other words, if the response of the device is maximized at 10 V, we may assume that the input is peaked at 13.5 V. Since the response of the device is linear, then we may relate the input to the output via a simple multiplication, as shown in this example, rather than through a more complex mathematical unfolding. 
     The processing of semiconductor and metal materials in order to achieve the charged particle energy analyzer electrode assembly of the present invention may be accomplished in accordance with processes that are known in the semiconductor and metal fabrication arts. With respect to the fabrication of silicon charged particle controlling electrodes or layers or plates, processes or combinations of processes such as are disclosed in the U.S. Pat. Nos. 4,089,103; 4,370,192; 4,753,896; 5,168,071; 5,217,564; 5,256,563 and 5,310,624 may for examples be used for present invention purposes. Additionally processes of the type disclosed in the standard reference texts “Silicon Processing for the VLSI Era” by Stanley Wolf and Richard Tauber, Lattice Press, 1986, and in “VLSI Technology” by S.M. Sze editor, McGraw-Hill, 1986, may be included in this list. Each of these patent and text references is hereby incorporated by reference herein. 
     With respect to the fabrication of stainless steel charged particle controlling electrodes or plates, processes or combinations of processes such as are disclosed in the U.S. Pat. Nos. 3,931,454; 4,528,070; 4,902,607 5,104,480; and 5,374,338 may for examples be used. Additionally techniques of the type disclosed in the publications “Micro-EDM” by Li, H. and Masaki, T., Society of Manufacturing Engineers Technical Paper, MS 91-485; “Micro-Electro-Discharge Machining” by T. Masaki, K Kawata, T. Sato, T. Mizutani, K. Yonemoti, A. Shibuya and T. Masuzawa, Proceedings of International Symposium for Electro-Machining, pp. 26-29, 1989; “Micro EDMing Excites the High Tech Community” EDM Today, pp. 32, 34, 46, March/April 1991; “Micro Electro-Discharge Machine Brochure” Panasonic Matsushita Research Institute, May 1990; “Electrical Discharge Machining” by Dr. Hong Li, SME, presented at the Society of Manufacturing Engineers and the Machining of SME, Sep. 17-18, 1991, may be included in this list. Each of these patent and publication references is also hereby incorporated by reference herein. 
     The charged particle energy analyzer of the present invention is thus compatible with MEMS fabrication techniques, in which layers of silicon and silicon dioxide are deposited and patterned on the microscopic level. The photolithographic etching of the metal plates used in constructing one arrangement of the invention is also believed a novel fabrication method for a charged particle device that is still macroscopic in scale. In space-borne applications of the invention where size and mass relate directly to the cost to launch a payload, the achieved high levels of miniaturization are a distinct advantage of the present charged particle energy analyzer. The advantage of miniaturization is also significant in laboratory and manufacturing plasma environment uses of the described energy analyzer, since the smaller the probe, the smaller the perturbation it induces into the system being monitored. A charged particle energy analyzer according to the invention is being prepared for space launch as the primary scientific payload of the U.S. Air Force Academy FalconSat-2 satellite. 
     The present invention therefore provides an improved charged particle energy analyzer in which electrodes of the device are laminated and therefore, for what is believed to be the first time, can be fabricated with the accuracy and repeatability of photolithography. Moreover because the charged particle energy analyzer can be so fabricated with photolithography, it can also be miniaturized to a high degree and is more suited to use in space applications. 
     The foregoing description of the preferred embodiment has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiment was chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally and equitably entitled.