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

Kuwahara, Makoto  ,  Nambo, Yoshito  ,  Aoki, Kota  ,  Sameshima, Kensuke  ,  Jin, Xiuguang  ,  Ujihara, Toru  ,  Asano, Hidefumi  ,  Saitoh, Koh  ,  Takeda, Yoshikazu  ,  Tanaka, Nobuo

109 ( 1 )  , pp.013108 - 013108 , 2016-07 , AIP Publishing
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.

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