About Me
I am a Physics major at the University of California, Santa Barbara in the class of 2024. I think particle accelerators are pretty neat.
Elevator Pitch
Over the last ten weeks, I have developed a user interface for data analysis on beam emittance - a parameter pertaining to phase coherence or “quality” of the beam. Emittance is an important parameter for making electron/positron beams useful in applications such as free-electron lasers or synchrotron x-ray sources.
Dipole Spectrometer
Dipole spectrometers of the kind diagramed in the cartoon below are used to collect the data that will be inputted into the Emittance GUI.
- Higher energies are more “rigid” meaning they are bent less by the dipole while lower energies are bent more - this gives a profile the transverse size of the beam as a function of the area.
- Beam shape on screen is a magnified image of the beam at plasma exit.
Emittance GUI
My GUI is designed to be an aid for the scientists to easily and quickly analyze beam profile data from the dipole spectrometers.
By loading the experiment and data set ID, the GUI searches the NAS to find the available cameras for the selected data set. Once the camera and image number have been selected, other various parameters auto-populate by drawing from the DAQ metadata as well as pre-loaded camera information of the selected image including:
- pixel to position conversion in mm
- proper pixel calibration for previously selected regions of interest already present in dataset
- image orientation such that the energy spread axis is always along the y-axis of the plot (which can be overridden in case of changes to camera orientation)
and for calibrating position in mm to energy in GeV:
- dipole strength (loaded upon pressing the "Auto Populate" button, will update if specified for a given dataset, otherwise automatically set to 10 GeV)
- nominal dispersion from the top of the spectrometer screen to the infinite energy axis
- 10 GeV beam position
In the case that any pre-loaded value is for some reason incorrect or does not match user expectations they can be manually updated by the user.
The Emittance GUI is able to provide three plots pertaining to the spectrometer data, the first of which being the actual profile monitor of the beam energy spread. This allows the user to see the densities of energies present within the particle bunch with reference to their transverse position. Next is the charge plot which makes a vertical projection of the beam profile into an easily legible graph that can be expressed in either energy or position versus charge. This plot allows the user to better identify what energies are represented in beam and in what densities. This is especially useful in determining the specific ROI for the last plot; the beam energy versus beam width. This plot takes a gaussian of along each energy "slice" of the beam profile then compiles a plot of each energy value versus the width of the gaussian for the respective energy "slice." This provides correlated vectors for beam width as a function of energy and energy which can be used in the equation specified in the "remaining steps" to output a specific value for emittance. However, this plot also stands alone as a valuable insight into the phase coherence of the particle bunch.
Recommended GUI Workflow
- Select experiment, enter specific dataset ID and press "Load DataSet" button.
- Select camera from the preloaded options, enter image for analysis and press "Plot" button.
- Press the "Charge Plot" button.
- Select the "Auto-Populate" button and make sure all calibration values are correct
- Specify desired number of energy tick marks, note that for cameras with larger ROIs such as LFOV, less tick marks are required than for cameras with smaller ROIs such as DTOTR
- Press "Toggle ECal" button - note that this button is a toggle and can be reversed to return to position values - if for some reason energy values are incorrectly spaced, try toggling and un-toggling ECal.
- Use energy calibrated charge plot to enter minimum and maximum energies to apply to beam width plot, note that energy decreases from left to right, min E and max E should still be entered accordingly.
- Note that the gaussian plot is especially sensitive to noise as it takes a series of gaussians - as such it is important to choose the energy ROI carefully to ensure the plot does not get overwhelmed by useless and noise, number of tick marks on energy axis can be increased to ensure precise choice of ROI.
- Press "Plot Gaussian" button.
Remaining Steps
- Use outputted values for beam energy vs. beam width (which have already been stored as correlated vectors) to calculate transport matrix elements and plug into the following equation to output an actual value for emittance (epsilon_n):
alpha and beta are twiss parameters at plasma exit, gamma is Lorentz factor.
- Update the "Print to Logbook" button such that it actually prints graphed data to logbook, currently just a copy-and-paste of the DAN version of the button.
Code
Includes Matlab App Designer file for GUI and all necessary Matlab support scripts. Make sure everything is in the same path for proper function. All code written in Matlab version 2020a
- App: Emit_GUI.mlapp
- App support script (links matlab scripts to appdesigner): AppSupportTemplate.m
- Data acquisition script: getDataSet.m
- Data processing script: read_img.m
- Plotting script: plot_img.m