Investigating Limits of Ultra-low Emittance Photocathodes

Description
Producing a brighter electron beams requires the smallest possible emittance from the cathode with the highest possible current. Several materials like ordered surface, single-crystalline metal surfaces, ordered surface, epitaxially grown high quantum efficiency alkali-antimonides, topologically non-trivial Dirac semimetals, and nano-structured

Producing a brighter electron beams requires the smallest possible emittance from the cathode with the highest possible current. Several materials like ordered surface, single-crystalline metal surfaces, ordered surface, epitaxially grown high quantum efficiency alkali-antimonides, topologically non-trivial Dirac semimetals, and nano-structured confined emission photocathodes show promise of achieving ultra-low emittance with large currents. This work investigates the various limitations to obtain the smallest possible emittance from photocathodes, and demonstrates the performance of a novel electron gun that can utilize these photocathodes under optimal photoemission conditions. Chapter 2 discusses the combined effect of physical roughness and work function variation which contributes to the emittance. This is particularly seen in polycrystalline materials and is an explanation for their higher than expected emittance performance when operated at the photoemission threshold. A computation method is described for estimating the simultaneous contribution of both types of roughness on the mean transverse energy. This work motivates the need for implementing ordered surface, single-crystalline or epitaxially grown photocathodes. Chapter 3 investigates the effects of coulomb interactions on electron beams from theoretically low emittance, low total energy spread nanoscale photoemission sources specifically for electron microscopy applications. This computation work emphasizes the key role that image charge effects have on such cold, dense electron beams. Contrary to initial expectations, the primary limiter to beam brightness for theoretically ultra-low emittance photocathodes is the saturation current. Chapters 4 and 5 describe the development and commissioning of a high accelerating gradient, cryogenically cooled electron gun and photoemission diagnostics beamline within the Arizona State University Photoemission and Bright Beams research lab. This accelerator is unique in it's capability to utilize photocathodes mounted on holders typically used in commercial surface chemistry tools, has the necessary features and tools for operating in the optimal regime for many advanced photocathodes. A Pinhole Scan technique has been implemented on the beamline, and has shown a full 4-dimensional phase space measurement demonstrating the ability to measure beam brightness in this gun. This gun will allow for the demonstration of ultra-high brightness from next-generation ultra-low emittance photocathodes.
Date Created
2023
Agent

Complex Baseband State Space Modeling of Radio Frequency Standing Wave Cavities

Description

Three models have been created to visualize and characterize the voltage response of a standing wave accelerating cavity system. These models are generalized to fit any cavity with known values of the quality factor, coupling factor, and resonant frequency but

Three models have been created to visualize and characterize the voltage response of a standing wave accelerating cavity system. These models are generalized to fit any cavity with known values of the quality factor, coupling factor, and resonant frequency but were applied to the Arizona State Universities Compact X-ray Free Electron Laser. To model these systems efficiently, baseband I and Q measurements were used to eliminate the modeling of high frequencies. The three models discussed in this paper include a single standing wave cavity, two cavities coupled through a 3dB quadrature hybrid, and a pulse compression system. The second model on two coupled cavities will demonstrate how detuning will impact two cavities with the same RF source split through a hybrid. The pulse compression model will be used to demonstrate the impact of feeding pulse compression into a standing wave cavity. The pulse compressor will demonstrate more than a 50\% increase of the voltage inside the cavity.

Date Created
2023-05
Agent

Measuring Beam Energy and Energy Jitter on the Compact X-Ray Light Source

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Description

For this thesis, the energy of the CXLS electron beam was measured and the beam’s energy jitter was calculated. It is essential to characterize the beam’s en- ergy and energy jitter in order to ensure that the powerful x-rays produced

For this thesis, the energy of the CXLS electron beam was measured and the beam’s energy jitter was calculated. It is essential to characterize the beam’s en- ergy and energy jitter in order to ensure that the powerful x-rays produced by CXLS will be of a consistent and desirable energy. The energy of the electrons within the electron beam can be calculated through utilizing basic physics prin- ciples and the geometry of the beamline. The energy of the beam for the data collected was found to be 3.426 MeV at POP module 1 and 12.3 MeV at POP module 9. The energy jitter of the beam was determined for four different angle settings of the VPSPD for linac 1 and found to be lowest when the linac 1 VPSPD was set to an angle of 97°. The energy jitter of the beam was 1.50e-03 MeV when the VPSPD for linac 1 was set to 97°.

Date Created
2022-05
Agent

CXFEL Screens

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Description

X-ray phase contrast imaging (XPCI) is a novel imaging method that utilizes phase information of X-rays in order to produce images. XPCI allows for highly resolved features that traditional X-ray imaging modalities cannot discern. The objective of this experiment was

X-ray phase contrast imaging (XPCI) is a novel imaging method that utilizes phase information of X-rays in order to produce images. XPCI allows for highly resolved features that traditional X-ray imaging modalities cannot discern. The objective of this experiment was to model initial simulations predicting the output signal of the future compact x-ray free electron laser (CXFEL) XPCI source. The signal was reported in tonal values (“counts”), where MATLAB and MATLAB App Designer were the computing environments used to develop the simulations. The experimental setup’s components included a yttrium aluminum garnet (YAG) scintillating screen, mirror, and Mako G-507C camera with a Sony IMX264 sensor. The main function of the setup was to aim the X-rays at the YAG screen, then measure its scintillation through the photons emitted that hit the camera sensor. The resulting quantity used to assess the signal strength was tonal values (“counts”) per pixel on the sensor. Data for X-ray transmission through water, air, and polyimide was sourced from The Center for X-ray Optics’s simulations website, after which the data was interpolated and referenced in MATLAB. Matrices were an integral part of the saturation calculations; field-of-view (FOV), magnification and photon energies were also necessary. All the calculations were compiled into a graphical user interface (GUI) using App Designer. The code used to build this GUI can be used as a template for later, more complex GUIs and is a great starting point for future work in XPCI research at CXFEL.

Date Created
2022-05
Agent

Dela Rosa Final Project (Spring 2022)

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Description

X-ray phase contrast imaging (XPCI) is a novel imaging method that utilizes phase information of X-rays in order to produce images. XPCI allows for highly resolved features that traditional X-ray imaging modalities cannot discern. The objective of this experiment was

X-ray phase contrast imaging (XPCI) is a novel imaging method that utilizes phase information of X-rays in order to produce images. XPCI allows for highly resolved features that traditional X-ray imaging modalities cannot discern. The objective of this experiment was to model initial simulations predicting the output signal of the future compact x-ray free electron laser (CXFEL) XPCI source. The signal was reported in tonal values (“counts”), where MATLAB and MATLAB App Designer were the computing environments used to develop the simulations. The experimental setup’s components included a yttrium aluminum garnet (YAG) scintillating screen, mirror, and Mako G-507C camera with a Sony IMX264 sensor. The main function of the setup was to aim the X-rays at the YAG screen, then measure its scintillation through the photons emitted that hit the camera sensor. The resulting quantity used to assess the signal strength was tonal values (“counts”) per pixel on the sensor. Data for X-ray transmission through water, air, and polyimide was sourced from The Center for X-ray Optics’s simulations website, after which the data was interpolated and referenced in MATLAB. Matrices were an integral part of the saturation calculations; field-of-view (FOV), magnification and photon energies were also necessary. All the calculations were compiled into a graphical user interface (GUI) using App Designer. The code used to build this GUI can be used as a template for later, more complex GUIs and is a great starting point for future work in XPCI research at CXFEL.

Date Created
2022-05
Agent

Image Intensity Calculations for XPCI Simulations Using a MATLAB GUI

Description
X-ray phase contrast imaging (XPCI) is a novel imaging method that utilizes phase information of X-rays in order to produce images. XPCI allows for highly resolved features that traditional X-ray imaging modalities cannot discern. The objective of this experiment was

X-ray phase contrast imaging (XPCI) is a novel imaging method that utilizes phase information of X-rays in order to produce images. XPCI allows for highly resolved features that traditional X-ray imaging modalities cannot discern. The objective of this experiment was to model initial simulations predicting the output signal of the future compact x-ray free electron laser (CXFEL) XPCI source. The signal was reported in tonal values (“counts”), where MATLAB and MATLAB App Designer were the computing environments used to develop the simulations. The experimental setup’s components included a yttrium aluminum garnet (YAG) scintillating screen, mirror, and Mako G-507C camera with a Sony IMX264 sensor. The main function of the setup was to aim the X-rays at the YAG screen, then measure its scintillation through the photons emitted that hit the camera sensor. The resulting quantity used to assess the signal strength was tonal values (“counts”) per pixel on the sensor. Data for X-ray transmission through water, air, and polyimide was sourced from The Center for X-ray Optics’s simulations website, after which the data was interpolated and referenced in MATLAB. Matrices were an integral part of the saturation calculations; field-of-view (FOV), magnification and photon energies were also necessary. All the calculations were compiled into a graphical user interface (GUI) using App Designer. The code used to build this GUI can be used as a template for later, more complex GUIs and is a great starting point for future work in XPCI research at CXFEL.
Date Created
2022-05
Agent

Jitter Measurement of Compact X-ray Light Source Radio Frequency System

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Description
The Compact X-ray Light Source is an x-ray source at ASU that allows scientists to study the structures and dynamics of matter on an atomic scale. The radio frequency system that provides the power to accelerate electrons in the Compact

The Compact X-ray Light Source is an x-ray source at ASU that allows scientists to study the structures and dynamics of matter on an atomic scale. The radio frequency system that provides the power to accelerate electrons in the Compact X-ray Light Source must operate with a high degree of precision. This thesis measures the precision with which that system performs.
Date Created
2022-05
Agent