Novel approach to push the limit of temporal resolution in ultrafast electron diffraction accelerators

Ultrafast electron diffraction techniques that employ relativistic electrons as a probe have been in the spotlight as a key technology for visualizing structural dynamics which take place on a time scale of a few femtoseconds to hundreds femtoseconds. These applications highly demand not only extreme beam quality in 6 D phase space such as a few nanometer transverse emittances and femtosecond duration but also equivalent beam stability. Although these utmost requirements have been demonstrated by a compact setup with a high gradient electron gun with state of the art laser technologies, this approach is fundamentally restricted by its nature for compressing the electrons in a short distance by a ballistic bunching method. Here, we propose a new methodology that pushes the limit of timing jitter beyond the state of the art by utilizing consecutive RF cavities. This layout already exists in reality for energy recovery linear accelerator demonstrators. Furthermore, the demonstrators are able to provide MHz repetition rates, which are out of reach for most conventional high gradient electron gun

Electron optics based on quadrupole multiplets for dark field imaging and diffraction with MeV electron beams

Ultrafast electron probing techniques offer unique experimental tools for investigating the tructural dynamics of ultrafast photo induced processes in molecular and condensed phase systems. In this work, we propose using the SEALAB Photoinjector s exceptional and versatile electron beam parameters to develop a state of the art facility for ultrafast electron diffraction and imaging UED and UEI experiments with high sensitivity in space, energy, and time. We first address the design of an electron lens based on quadrupoles that enables easy switching between diffraction and direct imaging modes with minimal system changes. We compare the performance of the quadrupole based lens with a simpler solenoid based lens with similar functionality by calculating their respective aberration coefficients. Furthermore, we introduce the necessary beam line modifications for enabling dark field imaging in the SEALAB Photoinjector. This development is crucial to achieve high resolution imaging and enable the study of a wide range of material system

High Resolution Interferometric Beam Size Monitor For Low Intensity Beams

Plasma based accelerator technology is reaching a mature state, where applications of the beam for medical sciences, imaging, or as an injector for a future large scale accelerator driven light source become feasible. Particularly, the requirements for beam injection into a storage ring based light source are very strict with regards to beam quality and reliability. A non invasive diagnostics greatly helps to reduce the commissioning time of the machine. We present a device suitable for online, non destructive monitoring of the transverse spot size of the injected beam. In order to measure lateral beam sizes with a few micrometer resolution, the technique uses an interferometric regime of coherent synchrotron radiation that is enabled by a sub femtosecond short bunch length. Simulations of the photon flux and the retrieval of the beam spot size are performed for different bandwidth filters in order to define the bandwidth acceptance. Results show the potential of the proposed system that achieves precise retrieval of the complex degree of coherence at an extremely low photon intensity similar to those expected towards the plasma acceleration injector

Monitoring the size of low intensity beams at plasma wakefield accelerators using high resolution interferometry

Plasma based accelerators are on the brink of a development stage, where applications of the beam for medical sciences, imaging, or as an injector for a future large scale accelerator driven light source become feasible. The requirements on electron beams for injection into a storage ring are stringent regarding beam quality and reliability. Here, we propose a beam diagnostic technique for measuring lateral beam sizes with a few amp; 956;m resolution by applying a state of art single photon camera to coherent synchrotron radiation that affords by a sub femtosecond short bunch length property. A sophisticated image processing algorithm enables the technique down to 5 photons pixel for the visibility of 0.132. Results show the potential of the proposed system that achieves precise retrieval of the complex degree of coherence at an extremely low photon intensity similar to those expected towards the plasma acceleration injector

Prospects of Ultrafast Electron Diffraction Experiments at Sealab

Ultrafast Electron Diffraction UED is a pump probe experimental technique that aims to image the structural changes that happen in a target structure due to photo excitation. Development of MeV UED capabilities is one of the main objectives at Sealab, a superconducting RF accelerator facility being commissioned in Helmholtz Zentrum Berlin. In order to perform UED experiments, the optimization of temporal resolution is of the utmost importance. The composition of the SRF Photoinjector, currently the main beam line in Sealab, offers superb flexibility to manipulate the longitudinal phase space of the electron bunch. At the same time, the CW operation of the accelerator provides an enhanced beam stability compared to warm guns, together with MHz repetition rates. This work aims to show the capacity of the SRF Photoinjector in Sealab to reach the required temporal resolution and explain the development and current status of the necessary tools to perform UED experiments at the facilit

bERLinPro Becomes SEALab Status and Perspective of the Energy Recovery Linac at HZB

Since end of the year 2020 the energy recovery linac ERL project bERLinPro of Helmholtz Zentrum Berlin has been officially completed. But what is the status of this facility, the next scientific goals in the framework of accelerator physics at HZB, what are the perspectives? To reflect the continuation of this endeavor and the broadening of applications of this machine from high current SRF based energy recovery concept up to an ultrafast electron diffraction UED facility producing shortest electron pulses, the facility is now named Sealab, Superconducting RF Electron Accelerator Laboratory. In this contribution, an overview of lessons learned so far, the status of the machine, the coming set up and commissioning steps with an outlook to midterm and future applications will be given. In summary, Sealab will expand, including the ERL application, and become a general accelerator physics and technology test machine to employ UED as a first study case and will also be an ideal testbed to investigate new control schemes based on digital twins or machine learning method

Feasibility Study for a storage ring to search for an Electric Dipole Moment of charged particles

The proposed method exploits charged particles confined as a storage ring beam (proton, deuteron, possibly 3He) to search for an intrinsic electric dipole moment (EDM) aligned along the particle spin axis. Statistical sensitivities can approach $10^{29}$ e.cm. The challenge will be to reduce systematic errors to similar levels. The ring will be adjusted to preserve the spin polarization, initially parallel to the particle velocity, for times in excess of 15 minutes. Large radial electric fields, acting through the EDM, will rotate the polarization. The slow rise in the vertical polarization component, detected through scattering from a target, signals the EDM. The project strategy is outlined. It foresees a step-wise plan, starting with ongoing COSY activities that demonstrate technical feasibility. Achievements to date include reduced polarization measurement errors, long horizontal-plane polarization lifetimes, and control of the polarization direction through feedback from the scattering measurements. The project continues with a proof-of-capability measurement (precursor experiment; first direct deuteron EDM measurement), an intermediate prototype ring (proof-of-principle; demonstrator for key technologies), and finally the high precision electric-field storage ring.The proposed method exploits charged particles confined as a storage ring beam (proton, deuteron, possibly helium-3) to search for an intrinsic electric dipole moment (EDM) aligned along the particle spin axis. Statistical sensitivities could approach 10$^{-29}$ e$\cdot$cm. The challenge will be to reduce systematic errors to similar levels. The ring will be adjusted to preserve the spin polarisation, initially parallel to the particle velocity, for times in excess of 15 minutes. Large radial electric fields, acting through the EDM, will rotate the polarisation. The slow rise in the vertical polarisation component, detected through scattering from a target, signals the EDM. The project strategy is outlined. It foresees a step-wise plan, starting with ongoing COSY (Cooler Synchrotron, Forschungszentrum J\"ulich) activities that demonstrate technical feasibility. Achievements to date include reduced polarisation measurement errors, long horizontal-plane polarisation lifetimes, and control of the polarisation direction through feedback from the scattering measurements. The project continues with a proof-of-capability measurement (precursor experiment; first direct deuteron EDM measurement), an intermediate prototype ring (proof-of-principle; demonstrator for key technologies), and finally the high precision electric-field storage ring

Feasibility Study for an EDM Storage Ring

This project exploits charged particles confined as a storage ring beam (proton, deuteron, possibly $^3$He) to search for an intrinsic electric dipole moment (EDM, $\vec d$) aligned along the particle spin axis. Statistical sensitivities can approach $10^{-29}$e$\cdot$cm. The challenge will be to reduce systematic errors to similar levels. The ring will be adjusted to preserve the spin polarization, initially parallel to the particle velocity, for times in excess of 15 minutes. Large radial electric fields, acting through the EDM, will rotate the polarization ($\vec d \times\vec E$). The slow rise in the vertical polarization component, detected through scattering from a target, signals the EDM. The project strategy is outlined. It foresees a step-wise plan, starting with ongoing COSY activities that demonstrate technical feasibility. Achievements to date include reduced polarization measurement errors, long horizontal-plane polarization lifetimes, and control of the polarization direction through feedback from the scattering measurements. The project continues with a proof-of-capability measurement (precursor experiment; first direct deuteron EDM measurement), an intermediate prototype ring (proof-of-principle; demonstrator for key technologies), and finally the high precision electric-field storage ring

Storage Ring to Search for Electric Dipole Moments of Charged Particles -- Feasibility Study

The proposed method exploits charged particles confined as a storage ring beam (proton, deuteron, possibly helium-3) to search for an intrinsic electric dipole moment (EDM) aligned along the particle spin axis. Statistical sensitivities could approach 10$^{-29}$ e$\cdot$cm. The challenge will be to reduce systematic errors to similar levels. The ring will be adjusted to preserve the spin polarisation, initially parallel to the particle velocity, for times in excess of 15 minutes. Large radial electric fields, acting through the EDM, will rotate the polarisation. The slow rise in the vertical polarisation component, detected through scattering from a target, signals the EDM. The project strategy is outlined. It foresees a step-wise plan, starting with ongoing COSY (Cooler Synchrotron, Forschungszentrum J\'ulich) activities that demonstrate technical feasibility. Achievements to date include reduced polarisation measurement errors, long horizontal-plane polarisation lifetimes, and control of the polarisation direction through feedback from the scattering measurements. The project continues with a proof-of-capability measurement (precursor experiment; first direct deuteron EDM measurement), an intermediate prototype ring (proof-of-principle; demonstrator for key technologies), and finally the high precision electric-field storage ring