The Boersch effect in a picosecond pulsed electron beam emitted from a semiconductor photocathode

• Published in: Applied physics letters Vol. 109; no. 1
• Main Authors: Kuwahara, Makoto, Nambo, Yoshito, Aoki, Kota, Sameshima, Kensuke, Jin, Xiuguang, Ujihara, Toru, Asano, Hidefumi, Saitoh, Koh, Takeda, Yoshikazu, Tanaka, Nobuo
• Format: Journal Article
• Language: English
• Published: 04.07.2016
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.4955457

The space charge effect has been clearly observed in the energy distributions of picosecond pulse beams from a spin-polarized electron microscope, and was found to depend upon the quantity of charge per pulse. The non-linear phenomena associated with this effect have also been replicated in beam simulations that take into account of a three-dimensional space charge. The results show that a charge of 500 aC/pulse provides the highest brightness with a 16-ps pulse duration, a 30-keV beam energy, and an emission spot of 1.8 μm. Furthermore, the degeneracy of the wave packet of the pulsed electron beam has been evaluated to be 1.6 × 10−5 with a charge of 100 aC/pulse, which is higher than that for a continuously emitted electron beam despite the low beam energy of 30 keV. The high degeneracy and high brightness contribute to the realization of high temporal and energy resolutions in low-voltage electron microscopy, which will serve to reduce radiolysis damage and enhance scattering contrast.