Patent ID: 12219685

DETAILED DESCRIPTION

To facilitate a better understanding of the present disclosure, the following examples of certain embodiments are given. The following examples are not to be read to limit or define the scope of the disclosure. Embodiments of the present disclosure and its advantages are best understood by referring toFIGS.1through4, where like numbers are used to indicate like and corresponding parts.

FIG.1illustrates an example Langmuir probe100coupled to a data acquisition system105. The Langmuir probe100may be configured to measure a parameter of a plasma110. Without limitations the parameter of the plasma110measured by the Langmuir probe100may be density, temperature, or combinations thereof. The Langmuir probe100may comprise a housing115, a plurality of bodies120, and a plurality of double Langmuir probes125aand125b. The housing115may be configured to contain the plurality of bodies120. The housing115may be comprised of any suitable materials, including, but not limited to, metals, nonmetals, ceramics, composites, polymers, and any combinations thereof. In one or more embodiments, the housing115may comprise of aluminum. The housing115may be any suitable size, height, shape, or any combinations thereof. As illustrated, the housing115may be in the shape of a cylindrical rod. The housing115may be operable to be maneuverable by a user (i.e., handheld). The cross-section of the housing115may comprise an inner diameter and an outer diameter, wherein the outer diameter is larger than the inner diameter. The housing115may comprise an internal cavity130defined by the inner diameter of the housing115. As illustrated, the plurality of bodies120may be disposed at least partially within the internal cavity130of the housing115.

The plurality of bodies120may be secured within the internal cavity130by any suitable means. Without limitations, such means may include, adhesives, brazing, welding, suitable fasteners, threading, or any combinations thereof. As illustrated, there may be three of the plurality of bodies120disposed within the housing115, however, the present disclosure is not limited to this number of bodies120. The plurality of bodies120may be configured to contain the plurality of double Langmuir probes125aand125b. The plurality of bodies120may be comprised of any suitable materials, including, but not limited to, metals, nonmetals, ceramics, composites, polymers, and any combinations thereof. In one or more embodiments, each of the plurality of bodies120may comprise of aluminum. The plurality of bodies120may be any suitable size, height, shape, or any combinations thereof. As illustrated, each of the plurality of bodies120may be in the shape of a cylindrical rod. The plurality of bodies120may comprise a set of internal cavities135, wherein the length of each set of internal cavities135is the same as the length of each of the plurality of bodies120. In embodiments, the plurality of bodies120may be disposed so as to abut each other within a grouping. As illustrated, the plurality of double Langmuir probes125aand125bmay be disposed within the set of internal cavities135of each of the plurality of bodies120.

The plurality of double Langmuir probes125aand125bmay be secured within each of the set of internal cavities135by any suitable means. Without limitations, such means may include, adhesives, brazing, welding, suitable fasteners, threading, or any combinations thereof. As illustrated, there may be three sets of the plurality of double Langmuir probes125aand125bdisposed within respective plurality of bodies120, however, the present disclosure is not limited to this number of double Langmuir probes125aand125b. The plurality of double Langmuir probes125aand125bmay be comprised of any suitable materials, including, but not limited to, metals, nonmetals, ceramics, composites, polymers, and any combinations thereof. In one or more embodiments, each of the e or more double Langmuir probes125aand125bmay comprise of tungsten. The plurality of double Langmuir probes125aand125bmay be any suitable size, height, shape, or any combinations thereof. As illustrated, each of the plurality of double Langmuir probes125aand125bmay be in the shape of a wire or thin rod. The plurality of double Langmuir probes125aand125bmay extend past a top end140of each of the plurality of bodies120in order to make direct contact with or be inserted into the plasma110. The plurality of double Langmuir probes125aand125bmay be configured to apply a current to the plasma110at a fixed voltage.

As illustrated, the Langmuir probe100may be coupled to the data acquisition system105. Each of the plurality of double Langmuir probes125a,bmay be electrically connected to the data acquisition system105through a set of leads145aand145b. The data acquisition system105may be operable to determine the relationship between the current applied to the plasma110and the fixed voltage. The data acquisition system105may comprise a power source150(for example, one or more batteries) operable to provide power to each of the plurality of double Langmuir probes125a,b. In one or more embodiments, the power source150may provide different fixed voltages to the plurality of double Langmuir probes125a,b(for example, 1 V, 50 V, and 60 V). The data acquisition system105may transmit measurements and data to an information handling system155, wherein the information handling system155may be operable to determine other parameters such as density and/or temperature based on the current-voltage relationship determined by the data acquisition system105.

FIG.2illustrates an example electrical circuit200used by the Langmuir probe100to determine the current-voltage relationship for each of the plurality of double Langmuir probes125a,125b. In one or more embodiments, the plurality of double Langmuir probes125a,125bmay be independent, and the electrical circuit for each is floating. There may be an equivalent number of electrical circuits200to the number of sets of leads145a,b. As illustrated, the electrical circuit200may include the set of leads145a,bfor one of the plurality of double Langmuir probes125a,b, the power source150, a resistor205, a first amplifier210, and a second amplifier215. In embodiments, each of the components within the electrical circuit200may be electrically coupled to one another. The resistor205may be disposed in series with the power source150, wherein the power source150may be operable to provide a voltage to drive a current across the resistor205. The current may flow through the one of the plurality of double Langmuir probes125a,bwhile inserted into the plasma110(referring toFIG.1). The current may be related to the values of the resistance of the resistor205and the voltage of the power source150. The current may be input into the first amplifier210, wherein the first amplifier210may be an instrumentation amplifier, and wherein the first amplifier210may increase the magnitude of the signal value of the current. The output of the first amplifier210may be an input to the second amplifier215, wherein the second amplifier215may be an isolation amplifier. Both the first amplifier210and the second amplifier215may be any suitable operational amplifiers. The output of the second amplifier215may be sent to the data acquisition system105for further processing.

FIG.3illustrates an example graph300of the current produced by the Langmuir probe100shown inFIG.1. As illustrated, the graph300may comprise of a first data point305, a second data point310, and a third data point315. In embodiments, each of the first data point305, second data point310, and third data point315may be associated with one of the plurality of double Langmuir probes125a,125b(referring toFIG.1) of the Langmuir probe100(referring toFIG.1). Each of the first data point305, second data point310, and third data point315may correspond to a fixed voltage value (for example, voltages provided by the power source150) and a related current value determined by the data acquisition system105(referring toFIG.1). In one or more embodiments, the first data point305, second data point310, and third data point315may be transmitted to the information handling system155(referring toFIG.1) for processing. By processing measurements from each of the plurality of double Langmuir probes125a,125bat fixed voltages, the information handling system155may be operable to process the measurements at a larger time resolution than typical processing of single or double Langmuir probes operating with voltage sweeping (i.e., at a faster rate). In embodiments, the information handling system155may be operable to fit a skewed hyperbolic tangent function to the first data point305, second data point310, and third data point315. The information handling system155may accommodate the ion sheath expansion that occurs when measuring the plasma110(referring toFIG.1) by subtracting the slope between the second data point310and the third data point315from the skewed hyperbolic tangent function, wherein this slope is an approximation. In response, the graph300may comprise a horizontal asymptote320for the skewed hyperbolic tangent function, wherein the ion saturation current (Ii,Sat) is equivalent to the value of the horizontal asymptote320. After subtracting the ion sheath expansion from the skewed hyperbolic tangent function, the graph300may be characterized by Equation 1, shown below.

I=Ii,Sattanh⁡(qe⁢Vbias2⁢kb⁢Te)(1)

Within Equation 1, Ii,Satmay be defined as the ion saturation current at one of the plurality of double Langmuir probes125a,125b; qemay be defined as the electron charge (for example, 1.602E-19 C); Vbiasmay be defined as the bias voltage applied between a set of one of the plurality of double Langmuir probes125a,125b(for example, the fixed voltage supplied by the power source150); kbmay be defined as the Boltzmann's constant (for example, 1.3806E-23 J/K or 1.602E-19 J/eV); and Temay be defined as the electron temperature. The information handling system155may be operable to determine the electron temperature of the plasma110from Equation 1. To determine the electron temperature of the plasma110, Equation 2 shows the derivative of Equation 1 where the value of Vbiasis zero. Then, Equation 3 shows Equation 2 rewritten to solve for the electron temperature, Te.

dIdVbias❘Vbias=0=Ii,Sat2⁢Te(2)

Te=Ii,sat2⁢dI/dVb⁢i⁢a⁢s(3)

The information handling system155may further be operable to determine the electron density of the plasma110from Equation 4, shown below. To determine the electron density of the plasma110, Equation 4 equates the ion saturation current to the Bohm velocity related to the electron density and the area of a singular one of the plurality of double Langmuir probes125a,125b.
Ii,Sat=αAprobenvbohm(4)

Within Equation 4, α may be defined as a reference constant (for example, the value is approximately 0.5); Aprobemay be defined as the area of a singular one of the plurality of double Langmuir probes125a,125bthat is inserted into the plasma110; n may be defined as the electron density of the plasma110; and vbohmmay be defined as the Bohm velocity, shown below in Equation 5. To determine the electron density of the plasma110, Equation 4 may be rewritten to solve for the electron density, n, as shown in Equation 6.

vb⁢o⁢h⁢m=kb⁢Temi(5)n=Ii,Satα⁢Aprobe⁢vbohm(6)

In one or more embodiments, the fixed voltage provided by the power source150for the first data point305may be selected to be less than the anticipated electron temperature of the plasma110to be measured. The second data point310and the third data point315may be selected to be greater than the anticipated electron temperature of the plasma110to be measured. These determinations may provide for a range that would encompass the anticipated electron temperature within the function fit to the first data point305, second data point310, and the third data point315. For example, the first data point305may comprise a voltage value of 1 V, the second data point310may comprise a voltage value of 50 V, and the third data point315may comprise a voltage value of 60 V, wherein the value of the anticipated electron temperature may be between 1 V and 50 V.

Information handling system155may be any processing device that controls the operations of and/or produces data from the Langmuir probe100and the data acquisition system105. Information handling system155may be hard-wired and/or wirelessly connected to the data acquisition system105. Information handling system155may use one or more elements illustrated inFIG.4.

FIG.4illustrates an example of elements400that may be included in information handling system155, according to embodiments. For example, information handling system155may include one or more input/output (I/O) interface(s)405, processing circuitry such as a processor410, memory(ies)415, and/or other suitable element(s). Interface405receives input, sends output, processes the input and/or output, and/or performs other suitable operation. Interface405may comprise hardware and/or software.

Processing circuitry performs or manages the operations of the component. Processing circuitry may include hardware and/or software. Examples of a processing circuitry include one or more computers, one or more microprocessors, one or more applications, etc. In certain embodiments, processing circuitry executes logic (e.g., instructions) to perform actions (e.g., operations), such as generating output from input. The logic executed by processing circuitry may be encoded in one or more tangible, non-transitory computer readable media (such as memory415). For example, the logic may comprise a computer program, software, computer executable instructions, and/or instructions capable of being executed by a computer. In particular embodiments, the operations of the embodiments may be performed by one or more computer readable media storing, embodied with, and/or encoded with a computer program and/or having a stored and/or an encoded computer program.

Memory415(or memory unit) stores information. Memory415may comprise one or more non-transitory, tangible, computer-readable, and/or computer-executable storage media. Examples of memory415include computer memory (for example, RAM or ROM), mass storage media (for example, a hard disk), removable storage media (for example, a Compact Disk (CD) or a Digital Video Disk (DVD)), database and/or network storage (for example, a server), and/or other computer-readable medium.

Herein, a computer-readable non-transitory storage medium or media may include one or more semiconductor-based or other integrated circuits (ICs) (such field-programmable gate arrays (FPGAs) or application-specific ICs (ASICs)), hard disk drives (HDDs), hybrid hard drives (HHDs), optical discs, optical disc drives (ODDs), magneto-optical discs, magneto-optical drives, floppy diskettes, floppy disk drives (FDDs), magnetic tapes, solid-state drives (SSDs), RAM-drives, SECURE DIGITAL cards or drives, any other suitable computer-readable non-transitory storage media, or any suitable combination of two or more of these, where appropriate. A computer-readable non-transitory storage medium may be volatile, non-volatile, or a combination of volatile and non-volatile, where appropriate.

With reference toFIGS.1-4, the method as presented in the present disclosure may be described. An operator may utilize the Langmuir probe100to measure a parameter of the plasma110(for example, density and/or temperature). Specifically, the Langmuir probe100may be at least partially inserted into the plasma110and actuated to apply a current based on a fixed voltage through each of the plurality of double Langmuir probes125a,125b. The electrical circuits200for each of the plurality of double Langmuir probes125a,125bmay float freely to arbitrary floating potentials without reference to a grounding. The current produced by the voltages from each of the plurality of double Langmuir probes125a,125bmay be processed by the data acquisition system105coupled to the Langmuir probe100. The data acquisition system105may determine the current-voltage relationship as the Langmuir probe100measures the plasma110. The information handling system155may receive data for the determined current-voltage relationship, such as the first data point305, second data point310, and third data point315. The information handling system155may be operable to determine the electron temperature of the plasma110and/or the electron density of the plasma110based, at least in part, on the first data point305, second data point310, and third data point315. The information handling system155may further accommodate the ion sheath expansion that occurs when conducting such measurements.

The present disclosure may provide numerous advantages, such as the various technical advantages that have been described with respective to various embodiments and examples disclosed herein. Other technical advantages will be readily apparent to one skilled in the art from the following figures, descriptions, and claims. Moreover, while specific advantages have been enumerated in this disclosure, various embodiments may include all, some, or none of the enumerated advantages.

Herein, “or” is inclusive and not exclusive, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A or B” means “A, B, or both,” unless expressly indicated otherwise or indicated otherwise by context. Moreover, “and” is both joint and several, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A and B” means “A and B, jointly or severally,” unless expressly indicated otherwise or indicated otherwise by context.

The scope of this disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments described or illustrated herein that a person having ordinary skill in the art would comprehend. The scope of this disclosure is not limited to the example embodiments described or illustrated herein. Moreover, although this disclosure describes and illustrates respective embodiments herein as including particular components, elements, feature, functions, operations, or steps, any of these embodiments may include any combination or permutation of any of the components, elements, features, functions, operations, or steps described or illustrated anywhere herein that a person having ordinary skill in the art would comprehend. Furthermore, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative. Although this disclosure describes or illustrates particular embodiments as providing particular advantages, particular embodiments may provide none, some, or all of these advantages.