# RBS Channeling MATLAB Application for Automated Measurement Control and Evaluation for 6MV Tandetron Accelerator

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## Abstract

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^{4}He+-beam directed on a Si (100) substrate. The channeling effect is seen as channeling dips of a lower signal in an otherwise rather homogeneous plane. Implemented application significantly facilitates the RBS/C measurement and analysis of the experiments, and also extends the ion beam analysis portfolio of Advanced Technologies Research Institute. Finally, software is ready-to-use for any Tandetron based ion beam facility with the ARGUS software for accelerator control.

## 1. Introduction

^{4}He+ primary beam in energy ranges from hundreds of keV to several MeV, the sample surface layer of up to 1 µm can be analyzed. The ions penetrate deeply into the crystal without substantially perturbing the lattice [1,2,3,4].

#### 1.1. Accelerator and Ion Beam Analysis

^{−7}mbar).

#### 1.2. Motivation

## 2. Preliminaries

#### 2.1. RBS/C Measurement Procedure

_{ROI}vs. the angle of tilting (e.g., Figures 14 and 15). In this way, the channeling spectrum was created. The channeling spectrum represents the dependency of Yield

_{ROI}on the angle of rotation, and the position of dips represent intersections with one of the crystal axes or planes.

_{ROI}which is fitted, and positions of the minima of dips were determined. By connecting the minima of corresponding dips, the projections of crystal planes were generated (e.g., Figures 14 and 15). The intersection of planes represents the angular position which is an offset of the major crystal axis (Figure 16). After entering this offset to the goniometer control, the alignment of the crystal was done. The accuracy of the alignment can be enhanced by repeating this procedure.

_{ROI}, the minimum value of the dip, denoted as χ

_{min,}and the angular width, were the two main parameters of the channeling spectrum that are determined (e.g., Figure 17).

#### 2.2. Issues

- Mechanical backslash of the goniometer could have negative influence on the accuracy of the measurement.
- Measured data are processed manually (which is time consuming); ARGUS doesn’t support an automatic mode for the measurements.
- An evaluation module for RBS/C in ARGUS is not available (not even an automated one).

## 3. Software and Experiment

^{4}He+ ions directed on a Si (100) at energy 2 MeV.

#### 3.1. Design and Architecture

- Data extraction from * mpa files into * dat files while data processing.
- Setting region of interests for measured RBS spectra.
- Fitting the data and locate minima.
- Determining planar axes rotation and getting coordinates of the axial axis (offset).
- Generating control configuration (BTC files) for fine measurement.

#### 3.2. RBS/C Measurement

#### 3.3. Coarse and Fine Evaluation

#### 3.4. Implemented Features for Automated Measurement and Analysis

#### 3.4.1. Batch File Generator (BFG)

- mode A; The measurement starts in the first step by increasing the theta angle (quadrant 1). When the angle reaches its maximum, increasing of the tilt angle is performed (quadrant 2). Then, the theta angle is decreasing (quadrant 3) down to its minimum. The last movement is performed in quadrant 4, when the tilt angle is decreasing down to its minimum.
- mode B; Before the measurement starts, the goniometer is moved into the starting position and in the step after that into the first measuring position. The measurement is performed from the lowest to the highest angle incrementally.

#### 3.4.2. Load and Convert Data Function

#### 3.4.3. Analysis Features and Evaluation Tools Demonstrated in Experiment: ^{4}He+ Beam Directed on a Si (100)

_{min}marked as Yield

_{min}(presents a minimum decrease value) and angular width. The angular width value was deducted as the full width at half maximum (FWHM) of the dip, where the half maximum (${\mathsf{\chi}}_{\mathrm{HM}}$) is calculated as follows:

## 4. Results and Discussion

- In Figure 18 there are scattered intersections of planar axes (calculated based on the intersection positions of main axes of the crystallographic planes displayed in Figure 16 and their distance from the origin of coordinate system), where we can see the dispersion of points for both modes of generating steps.
- We calculated the dispersion for the intersection points of planes as it is shown in Table 3.

_{min}= 0.32 ± 0.03) was determined from the normalized angular plot (Figure 17). Designed application automates numerous measurements and automatically sets the position of the goniometer, the functionality of which we verified on the experiment and sample.

## 5. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**Layout of the 6 MV tandem accelerator: (1) Ion sources; (2) Mass analyzing magnet; (3) Focusing system in front of the accelerator; (4) Tandem accelerator tank; (5) Quadrupole triplet lens; (6) Switching magnet; (7) Modification chamber; (8) Ion beam analysis end-station.

**Figure 17.**Normalized yield of a fine measurement with measured and calculated values. The channeling dip features a reduction in ROI counts by a factor 0.32 with a FWHM width of 0.90°.

**Figure 18.**Points of intersections of planar axes measured by both mode A (blue points) and B (red points).

Axis of Rotation | Notation in Argus | Notation in MATLAB |
---|---|---|

X-Rotation (tilt-horizontal) | tiltPos = X-Tilt | Tilt |

Y-Rotation (azimuthal) | thetaPos = theta | Theta |

Z-Rotation (incoming beam) | PhiPos = phi | Phi |

Parameter | Value | Description | |
---|---|---|---|

StepNr | 11 | Step identifier | |

PhiPos | 0.00 | Sample holder rotation | |

ThetaPos | −2.20 | Horizontal axe | |

TiltPos | −4.00 | Vertical axe | |

LiftPos | 0.00 | Sample holder vertical shift | |

FoilPos | 1 | Foil identifier (for detector R2) | |

ConfigFile | …/config.mpa | Configuration file for a multichannel analyzer | |

MaxTime | 0 | Time limit | A measurement stops if one of these values is reached. Zero is ignored. |

Dose | 0.20 | Dose limit (µC) | |

RoiCounts | 0 | Integral limit | |

RoiDetector | 1 | Detector identifier | |

OutputFile | …/data_11.mpa | A file, where measured spectrum is saved. | |

Convert_Det1 | Fixed RBS | Define, which detector is used to measure a spectrum under the specific Det. | |

Convert_Det2 | None | ||

Convert_Det3 | None | ||

Convert_Det4 | None |

Mode | Dispersion | |
---|---|---|

Theta Angles | Tilt Angles | |

mode A | 0.253 ± 0.103 | 0.284 ± 0.116 |

mode B | 0.072 ± 0.029 | 0.073 ± 0.030 |

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**MDPI and ACS Style**

Stremy, M.; Horvath, D.; Vana, D.; Kebisek, M.; Gaspar, G.; Bezak, P.; Riedlmajer, R. RBS Channeling MATLAB Application for Automated Measurement Control and Evaluation for 6MV Tandetron Accelerator. *Appl. Sci.* **2021**, *11*, 3817.
https://doi.org/10.3390/app11093817

**AMA Style**

Stremy M, Horvath D, Vana D, Kebisek M, Gaspar G, Bezak P, Riedlmajer R. RBS Channeling MATLAB Application for Automated Measurement Control and Evaluation for 6MV Tandetron Accelerator. *Applied Sciences*. 2021; 11(9):3817.
https://doi.org/10.3390/app11093817

**Chicago/Turabian Style**

Stremy, Maximilian, Dusan Horvath, Dusan Vana, Michal Kebisek, Gabriel Gaspar, Pavol Bezak, and Robert Riedlmajer. 2021. "RBS Channeling MATLAB Application for Automated Measurement Control and Evaluation for 6MV Tandetron Accelerator" *Applied Sciences* 11, no. 9: 3817.
https://doi.org/10.3390/app11093817