Ultrashort electron bunches are becoming increasingly important for applications such as free-electron lasers, time-resolved electron diffraction/microscopy, and advanced accelerator concepts. We ...report femtosecond electron bunch generation with a unique rf gun and its precise measurement using a transverse deflecting cavity. A bunch length of323±13fswith 120 pC (∼7.5×108electrons) was achieved at a distance of just 3 m from the cathode. A longitudinal phase space distribution was also achieved, and we successfully experimentally confirmed the linearly energy chirped electron bunch generation and self-compression by the velocity difference.
We present a new design for a rf electron gun to be used in ultrashort (∼1ps ) electron bunch generation. Using both simulation and measurement we evaluated the principle of this new type rf gun and ...were able to confirm an ultrashort bunch generation. During simulation, a bunch length of less than 100 fs(rms) with a 100pC/bunch charge was confirmed at the optimum operating condition. The principle is to produce a linearly distributed longitudinal phase space by using an attached output cell specially designed for energy chirping. Such phase space distribution can be rotated by the velocity difference in the bunch. We already fabricated an energy chirping cell attached rf gun and successfully observed 0.2 THz coherent synchrotron radiation, which corresponds to less than 500 fs bunch. Such an electron gun can be used as a compact THz light source and a new electron injector with an ultrashort bunch.
The coherent radiation spectrum extends into the far-infrared/THz region when the electron bunch is shorter than 1ps (0.3mm). Such ultra-short electron bunches can be produced using a variety of ...bunching schemes in electron accelerators. We have designed a photocathode RF electron gun, named ECC RF gun, specifically for ultra-short bunch generation. ECC stands for energy chirping cell. This paper describes the brief principle of the ECC RF gun, CTR (coherent transition radiation) observation using Schottky barrier diodes (SBD) and spectrum measurement using interferometry with SBDs. We have successfully confirmed the generation of 0.05–0.3THz high peak power pulsed CTR.
A cryogenic C-band 2.6-cell photocathode RF electron gun has been studied at Nihon University in collaboration with KEK for future use in a compact electron-accelerator based monochromatic X-ray ...source. The cold model cavity with an input coupler was fabricated at KEK in 2016 by ultraprecision machining and diffusion bonding techniques. The RF characteristics of the cavity obtained at cryogenic measurements have been in agreement with the result of the CST Studio simulation. The unloaded quality factor of ∼73000 has been obtained at the cavity temperature of 20 K, which is 5.5 times higher than that at room temperature and consistent with the simulation taking into account the anomalous skin effect of the cavity surface resistance. The input coupling coefficient of approximately 20 at 20 K has well reproduced the design value. The shift in the accelerating n-mode resonant frequency due to the cavity temperature change from 296.65 to 20 K has been 19.02 MHz, being 0.12 MHz greater than the value based on the linear expansion coefficients for copper by NIST.
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