Speaker
Description
In recent years, transmission electron microscopy (TEM) has increasingly focused on achieving high spatial resolution at lower electron energies. However, higher electron energies remain desirable for the observation of thick specimens and high-density materials, as well as for investigating phenomena and material properties that depend on specimen thickness. Conventional TEMs rely on electrostatic acceleration, which imposes practical limitations on further increases in electron energy.
To overcome this limitation, we are developing an SRF-TEM (Superconducting Radio-Frequency Transmission Electron Microscope), a new TEM concept that applies superconducting radio-frequency (SRF) accelerator technology to electron microscopy. By employing a superconducting RF cavity for beam acceleration, the SRF-TEM has the potential to achieve electron energies beyond the practical range of conventional TEMs in a compact system.
One of the major challenges of RF acceleration is the increase in beam energy spread caused by the time-varying accelerating field. To mitigate this effect, we have developed a unique superconducting cavity, “2-mode cavity”, in which the $\textrm{TM}_{010}$ and $\textrm{TM}_{020}$ modes are simultaneously excited to compensate for the RF-induced energy spread.
At KEK, we are currently developing the key components of the SRF-TEM, including a photocathode electron gun, the 2-mode cavity, and a cryomodule, based on an existing 300 kV TEM platform. This presentation will introduce the SRF-TEM concept and report recent progress toward the construction of a proof-of-principle system.