Realization of a Cherenkov-Diffraction Radiation based Outcoupling Scheme for Beam Diagnostic Applications

Description

Radiation generated by high-energy particle beams is extensively used for beam diagnostics. This radiation originates from the electromagnetic field bound to the charged particle, which separates from the particle itself. The freely propagating field can be measured at significant distances as radiation across a wide spectral range. The naming of the radiation generation process depends on the mechanism causing the separation of the electromagnetic field. Widely used examples for particle beam diagnostics, primarily to measure beam profiles in the longitudinal and transverse planes, include synchrotron radiation, transition radiation, diffraction radiation, and Smith–Purcell radiation.

In recent years, Cherenkov radiation (ChR) has attracted growing interest due to its high light yield and wide emission angle, which facilitates the separation of radiation from the particle beam. While traditional ChR generation is invasive, an innovative experiment demonstrated a noninvasive beam diagnostic method based on detecting incoherent Cherenkov diffraction radiation (ChDR). This refers to ChR emitted by charged particles traveling near, but not inside, a dielectric material. ChDR combines the advantages of ChR with noninvasive photon generation, making it a promising technique for beam diagnostics.

The goal of this PhD project is to investigate ChDR as a tool for extracting light from the accelerator vacuum system in the visible and infrared spectral regions, with potential applications in bunch length diagnostics and timing measurements. The project will progress in several phases:

1. Simulation and Design: Simulate the properties of ChDR and develop an optimized design for extracting radiation in the desired spectral region, minimizing dispersion broadening effects in the dielectric that could degrade the bunch profile.
2. Prototype Development and Testing: Manufacture and test prototype monitors at DESY linear accelerators, such as FLASH, ARES, or XFEL. These facilities are ideal due to their ultrashort bunch lengths, on the order of tens of femtoseconds, enabling precise evaluation of the time resolution of light extraction.
3. Implementation of Online Monitoring: Develop and test an online bunch length monitor system at the PETRA III storage ring, a third-generation light source. This system will utilize an infrared ChDR extraction port and a fast photodiode for continuous, real-time bunch length diagnostics. A cost-effective, fast readout system, such as a photonic stretched fiber coupled with an oscilloscope, will be implemented to streamline the process.

Conventional bunch length diagnostics in electron storage rings often rely on extracting visible synchrotron radiation (SR) and using a streak camera. However, SR extraction presents challenges, such as (1) increased machine impedance due to a radiation outcoupling mirror near the beam axis, raising the risk of instabilities, and (2) potential damage to the mirror from the SR X-ray component, necessitating expensive absorber systems. A ChDR-based outcoupling scheme for visible and infrared radiation offers a simpler, more robust solution to these issues, enabling diverse beam diagnostic applications.

As a PhD researcher, you will benefit from comprehensive postgraduate training in accelerator science at the Cockcroft Institute and specialized data science training through the University of Liverpool’s LIV.INNO Centre for Doctoral Training. A particularly interesting aspect is that you will get the opportunity to spend years 2 and 3 of your PhD at DESY in Germany, where you will be taking data and carry out experiments. A six-month industry placement will further broaden your research expertise and career skills.

Subject to the usual confirmations, this four-year project is supported by the LIV.INNO Centre for Doctoral Training, the Cockcroft Institute of Accelerator Science and Technology and DESY, Germany. To apply for this position please visit the University of Liverpool PhD programme application page here.