CN117038427A - Method for adjusting beam stability of double plasma ion sources - Google Patents
Method for adjusting beam stability of double plasma ion sources Download PDFInfo
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- CN117038427A CN117038427A CN202311051667.XA CN202311051667A CN117038427A CN 117038427 A CN117038427 A CN 117038427A CN 202311051667 A CN202311051667 A CN 202311051667A CN 117038427 A CN117038427 A CN 117038427A
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- 238000000034 method Methods 0.000 title claims abstract description 37
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 79
- 239000001301 oxygen Substances 0.000 claims abstract description 79
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 79
- 238000010884 ion-beam technique Methods 0.000 claims abstract description 36
- 230000009977 dual effect Effects 0.000 claims description 13
- 230000008859 change Effects 0.000 claims description 8
- 230000008569 process Effects 0.000 claims description 7
- 238000004364 calculation method Methods 0.000 claims description 4
- 230000003044 adaptive effect Effects 0.000 claims description 3
- 238000004891 communication Methods 0.000 claims description 3
- 238000001514 detection method Methods 0.000 claims description 3
- 238000013178 mathematical model Methods 0.000 claims description 3
- 239000007789 gas Substances 0.000 abstract description 3
- 238000001004 secondary ion mass spectrometry Methods 0.000 abstract description 2
- 230000009466 transformation Effects 0.000 abstract 1
- 239000000523 sample Substances 0.000 description 8
- 238000010586 diagram Methods 0.000 description 4
- 230000009471 action Effects 0.000 description 3
- 238000005299 abrasion Methods 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000004949 mass spectrometry Methods 0.000 description 1
- 238000001819 mass spectrum Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/26—Mass spectrometers or separator tubes
- H01J49/34—Dynamic spectrometers
- H01J49/42—Stability-of-path spectrometers, e.g. monopole, quadrupole, multipole, farvitrons
- H01J49/426—Methods for controlling ions
- H01J49/4265—Controlling the number of trapped ions; preventing space charge effects
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/02—Details
- H01J49/10—Ion sources; Ion guns
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- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
Abstract
The invention belongs to the technical field of secondary ion mass spectrometry, and discloses a method for adjusting the beam stability of a double-plasma ion source, which comprises the following steps: s1: changing the existing pure manual adjusting oxygen concentration adjusting valve into a mass flow controller; s2: when the oxygen mass flow is changed due to interference or other factors, the mass flow controller automatically adjusts the opening of the valve, so that the oxygen source beam is stable; s3: when the set oxygen mass flow is insufficient to ensure the concentration of oxygen in the source and the stability of primary ion beam current, the set value of the oxygen mass flow is optimally adjusted based on an intelligent control algorithm of the LabVI EW system. The control system and the algorithm can provide a reference example for the transformation of the ion source control system of the mass spectrometer equipped with the double plasma gas sources, and the implementation of the system reduces the workload of operators of the instrument, improves the automation level of the instrument and improves the beam quality of primary ion beams.
Description
Technical Field
The invention belongs to the technical field of secondary ion mass spectrometry, and particularly relates to a method for adjusting beam stability of a double-plasma ion source.
Background
When the secondary ion probe analyzes an electronegative sample, a primary ion beam is generated by a double-plasma ion source, the magnetic field intensity and the discharge current in three parameters affecting the performance of the primary ion beam are usually fixed values, and the oxygen pressure, namely the oxygen concentration in the ion source cavity, becomes a main parameter affecting the beam stability of the ion source.
At present, the secondary ion probe is generally used for realizing stable output of the primary ion beam current by using an oxygen source (namely, a double plasma ion source, and the medium gas is oxygen), the adjustment of the oxygen concentration in the oxygen source is controlled by a high-precision needle valve, and the needle valve adjustment is manually completed by an instrument operator according to the values of an oxygen pressure gauge of the oxygen source and the primary ion beam current feedback (measured by a picoampere meter). When the ion source operates, oxide impurities are generated in the oxygen source due to high temperature, and part of the oxide is accumulated in an oxygen inlet channel of the oxygen source, so that the oxygen inlet channel of the oxygen source is narrowed, or the concentration of oxygen in the oxygen source is influenced by factors such as temperature change of working environment and the like.
In the secondary ion mass spectrum work, in order to ensure the stable oxygen concentration in the 'oxygen source', the oxygen inlet pressure needs to be changed by manually adjusting the needle valve at intervals, meanwhile, in the adjusting process, if the pressure fluctuation in the 'oxygen source' is too large, the intensity and stability of the primary ion beam and the precision of experimental results are influenced, and the experimental results are invalid and even are interrupted when serious, so that the method for adjusting the beam stability of the double plasma sources is provided.
Disclosure of Invention
The invention aims to provide a method for adjusting the beam stability of a dual plasma ion source, which aims to solve the problems in the background technology.
In order to achieve the above object, the present invention provides the following technical solutions: a method for adjusting the beam stability of a double-plasma ion source comprises the following steps:
s1: changing the existing pure manual adjusting oxygen concentration adjusting needle valve into a mass flow controller;
s2: when the oxygen mass flow is changed due to interference or other factors, the mass flow controller automatically adjusts the opening of the valve, so that the oxygen source beam is stable;
s3: when the set oxygen mass flow is insufficient to ensure the concentration of oxygen in the source and the stability of primary ion beam, the set value of the oxygen mass flow is optimally adjusted based on an intelligent control algorithm of a LabVIEW system.
Preferably, in the step S1 of beam stability adjustment of the dual plasma ion source, the mass flow controller is a selected mass flow meter, which has a serial communication interface, and may be connected with a serial port of a computer, a monitoring program developed based on LabVIEW in the computer directly adjusts a set value of the mass flow controller, and at the same time, the monitoring program based on LabVIEW may acquire the beam intensity of the oxygen source from the picoampere meter through the serial port according to a certain sampling frequency, and adjust the valve opening of the mass flow controller according to an error between the beam intensity and a target value, so as to complete closed-loop control of the oxygen source.
Preferably, in the step S2 of adjusting the beam stability of the dual plasma ion source, the stability of the oxygen source beam is measured by using the sample variance of the primary ion beam through the controlled index, the oxygen source beam is maintained for a period of time after the mass flow of oxygen is adjusted, and after the oxygen concentration of the oxygen source and the primary ion beam are both stable, the calculation is performed to determine whether further adjustment is needed.
Preferably, the relationship between the controlled index 'stability of primary ion beam' and oxygen mass flow is difficult to describe by an accurate mathematical model, the characteristics change along with the change of external conditions, and an intelligent control algorithm is developed for the controlled object without the model and is realized based on a LabVIEW system;
the controlled index uses the sample variance of the primary ion beam current (current) to measure its stability, i.e. n samples c of the primary ion beam current c i (i=1,., n), the average value is as follows:
the standard deviation is:
preferably, the oxygen mass flow q is heuristically increased by Δq 1 After waiting for t time, the system is stable and reaches the point B, if the standard deviation sigma of the primary ion beam current of the point B is larger than the set high limit sigma max Then Δq is further increased 2 . After multiple adjustment, the x point is reached, at the moment, the x point coincides with the intersection point O or is positioned on the right side of the intersection point O, the standard deviation sigma of the primary ion beam reaches the requirement, and in the adjustment process, each step delta q is calculated i Before outputting the new oxygen mass flow q, checking whether the adjustable flow high limit q is exceeded max If the regulation is exceeded, the regulation cannot be continued, and the alarm indicates that the regulation valve has no regulation allowance;
obtaining Δq using adaptive step size method i I.e. start to make a heuristic adjustment first, at a known point a coordinates (q A ,σ A ) And B point coordinates (q B ,σ B ) Then, a straight line passing through A, B points and a set high limit sigma can be obtained max The intersection point of the lines, the adjustment formula is:
preferably, the sigma A To sigma B Before the percentage increment of (a) is smaller than a certain value, the method of self-adapting step length is used for adjusting, and the method is used for adjusting the percentage increment of (a) at sigma A To sigma B After the percentage increment of the (C) is smaller than a certain value, a fixed step length method is replaced, the step length in the last adjustment is used as the fixed step length, and finally the X point is adjusted.
Preferably, in the step S3 of adjusting the beam stability of the dual plasma ion source, in the LabVIEW system based on the intelligent control algorithm of the LabVIEW system, the control of the oxygen source is completed based on the detection of the primary ion beam c by the monitoring program and the adjustment of the newly added set value of the oxygen mass flow q by the intelligent control algorithm.
The beneficial effects of the invention are as follows:
1. according to the invention, stable control of the oxygen source beam flow is realized by a method of cascade control of a mass flow controller and an intelligent control algorithm, when the oxygen mass flow is changed due to interference, the mass flow controller automatically adjusts the valve opening to ensure that the oxygen source beam flow is stable, when the set oxygen mass flow is insufficient to ensure the concentration of oxygen in a source and the stability of primary ion beam flow, the intelligent control algorithm based on a LabVIEW system optimally adjusts the oxygen mass flow set value so as to ensure the performance of a secondary ion probe mass spectrometry experiment, the steady state feedback control algorithm overcomes the problems of the existing rapid dynamic feedback control algorithm, such as hysteresis in a valve switch, hysteresis in standard deviation calculation and nonlinearity in an oxygen concentration increasing process, system oscillation and continuous abrasion of a valve adjustment, and the control system and algorithm can provide a reference example for the reconstruction of a mass spectrometer ion source control system provided with a double plasma gas source.
Drawings
FIG. 1 is a diagram of the annotation of the algorithm variable symbols of the present invention;
FIG. 2 is a schematic diagram of a qualitative relationship algorithm between the oxygen mass flow q and the primary ion beam standard deviation sigma;
FIG. 3 is a block diagram of the LabVIEW system intelligent control algorithm of the present invention;
FIG. 4 is a block diagram of the LabVIEW system of the present invention storing historical data for calculation.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
As shown in fig. 1 to 4, the embodiment of the present invention provides a method for adjusting beam stability of a dual plasma ion source, wherein the steps of beam stability adjustment of the dual plasma source are as follows:
s1: changing the existing pure manual adjusting oxygen concentration adjusting needle valve into a mass flow controller;
s2: when the interference causes the change of the oxygen mass flow, the mass flow controller automatically adjusts the opening of the valve, so that the oxygen source beam is stable;
s3: when the set oxygen mass flow is insufficient to ensure the concentration of oxygen in the source and the stability of primary ion beam, the set value of the oxygen mass flow is optimally adjusted based on an intelligent control algorithm of a LabVIEW system.
As shown in the figure, in one embodiment, in the step S1 of beam stability adjustment of the dual plasma source, the mass flow controller is a selected mass flow meter, which has a serial communication interface, and may be connected to a serial port of a computer, and the set value of the mass flow controller is directly adjusted from the computer based on a LabVIEW monitoring program.
As shown in the figure, in one embodiment, in the step S2 of dual plasma ion source beam stability adjustment, the stability of the oxygen source beam is measured by the controlled index by using the sample variance of the primary ion beam, the oxygen source beam is maintained for a period of time after the oxygen mass flow is adjusted, and after the oxygen source oxygen concentration and the primary ion beam are both stable, it is calculated and determined whether further adjustment is needed.
As shown in the figure, in one embodiment, the relationship between the controlled index of 'the stability of the primary ion beam' and the oxygen mass flow is difficult to describe by an accurate mathematical model, the characteristics change along with the change of external conditions, and an intelligent control algorithm is developed for the controlled object without the model and is realized based on a LabVIEW system;
the controlled index uses the sample variance of the primary ion beam current to measure its stability, i.e. the primary ion beam currentcA kind of electronic devicenSubsampling i c(i＝1,..,n)，The average value is as follows:
the standard deviation is:
as shown, in one embodiment, the oxygen mass flow q is increased heuristically by Δq 1 After waiting for t time, the system is stable and reaches the point B, if the standard deviation sigma of the primary ion beam current of the point B is larger than the set high limit sigma max Then Δq is further increased 2 . After multiple adjustment, the x point is reached, at the moment, the x point coincides with the intersection point O or is positioned on the right side of the intersection point O, the standard deviation sigma of the primary ion beam reaches the requirement, and in the adjustment process, each step delta q is calculated i Before outputting the new oxygen mass flow q, checking whether the adjustable flow high limit q is exceeded max If the regulation is exceeded, the regulation cannot be continued, and the alarm indicates that the regulation valve has no regulation allowance;
obtaining Δq using adaptive step size method i I.e. start to make a heuristic adjustment first, at a known point a coordinates (q A ,σ A ) And B point coordinates (q B ,σ B ) Then, a straight line passing through A, B points and a set high limit sigma can be obtained max The intersection point of the lines, the adjustment formula is:
as shown, in one embodiment, σ A To sigma B Before the percentage increment of (a) is smaller than a certain value, the method of self-adapting step length is used for adjusting, and the method is used for adjusting the percentage increment of (a) at sigma A To sigma B After the percentage increment of the (C) is smaller than a certain value, a fixed step length method is replaced, the step length in the last adjustment is used as the fixed step length, and finally the X point is adjusted.
As shown in the figure, in one embodiment, in the LabVIEW system based on the intelligent control algorithm of the LabVIEW system in the step S3 of adjusting the beam stability of the dual plasma ion source, the control of the oxygen source is completed based on the detection of the primary ion beam c by the monitoring program and the adjustment of the newly added set value of the oxygen mass flow q by the intelligent control algorithm.
It is noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (7)
1. The method for adjusting the beam stability of the double-plasma ion source is characterized by comprising the following steps of:
s1: changing the existing pure manual adjusting oxygen concentration adjusting valve into a mass flow controller;
s2: when the oxygen mass flow is changed due to interference or other factors, the mass flow controller automatically adjusts the opening of the valve, so that the oxygen source beam is stable;
s3: when the set oxygen mass flow is insufficient to ensure the concentration of oxygen in the source and the stability of primary ion beam, the set value of the oxygen mass flow is optimally adjusted based on an intelligent control algorithm of a LabVIEW system.
2. The method of claim 1, wherein: in the step S1 of beam stability adjustment of the dual plasma ion source, the mass flow controller is a selected mass flow meter, which is provided with a serial communication interface, can be connected with a serial port of a computer, and can directly adjust a set value of the mass flow controller based on a LabVIEW monitoring program in the computer.
3. The method of claim 1, wherein: in the step S2 of the dual-plasma ion source beam stability adjustment, the stability of the ion source beam is measured by adopting a sample variance of primary ion beam through a controlled index, the ion source beam stability is that after the mass flow of oxygen is adjusted, the ion source beam is kept for a period of time, and after the oxygen concentration of the plasma source and the primary ion beam are stable, the calculation is carried out to judge whether further adjustment is needed.
4. A method of beam stability adjustment for dual plasma ion sources as defined in claim 3, wherein: the relation between the controlled index 'stability of primary ion beam' and oxygen mass flow is difficult to describe by an accurate mathematical model, the characteristics change along with the change of external conditions, an intelligent control algorithm is developed for the controlled object without the model, and the intelligent control algorithm is realized based on a LabVIEW system;
the controlled index uses the sample variance of the primary ion beam current (current) to measure its stability, i.e. n samples c of the primary ion beam current c i (i=1,., n), the average value is as follows:
the standard deviation is:
5. a method of beam stability adjustment for dual plasma ion sources as defined in claim 3, wherein: the oxygen mass flow q is heuristically increased by deltaq 1 After waiting for t time, the system is stable and reaches the point B, if the standard deviation sigma of the primary ion beam current of the point B is larger than the set high limit sigma max Then Δq is further increased 2 . After multiple adjustment, the x point is reached, at the moment, the x point coincides with the intersection point O or is positioned on the right side of the intersection point O, the standard deviation sigma of the primary ion beam reaches the requirement, and in the adjustment process, each step delta q is calculated i Before outputting the new oxygen mass flow q, checking whether the adjustable flow high limit q is exceeded max If the regulation is exceeded, the regulation cannot be continued, and the alarm indicates that the regulation valve has no regulation allowance;
obtaining Δq using adaptive step size method i I.e. start to make a heuristic adjustment first, at a known point a coordinates (q A ,σ A ) And B point coordinates (q B ,σ B ) Then, a straight line passing through A, B points and a set high limit sigma can be obtained max The intersection point of the lines, the adjustment formula is:
6. a method of beam stability adjustment for dual plasma ion sources as defined in claim 3, wherein: the sigma A To sigma B Before the percentage increment of (a) is smaller than a certain value, the method of self-adapting step length is used for adjusting, and the method is used for adjusting the percentage increment of (a) at sigma A To sigma B After the percentage increment of the (C) is smaller than a certain value, a fixed step length method is replaced, the step length in the last adjustment is used as the fixed step length, and finally the X point is adjusted.
7. The method of claim 1, wherein: in the intelligent control algorithm LabVIEW system based on the LabVIEW system in the step S3 of the dual-plasma ion source beam stability adjustment, the intelligent control algorithm is compiled between the detection of the primary ion beam c based on a monitoring program and the adjustment of the newly added set value of the oxygen mass flow q, so that the control of the ion source beam stability is completed.
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