12-15 July 2011
Saint George Hotel
Africa/Johannesburg timezone
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Compression of highly charged electron pulses for single shot femtosecond time-resolved electron diffraction experiments

Presented by Mr. Nicolas ERASMUS on 14 Jul 2011 from 14:15 to 14:30
Type: Oral Presentation
Session: LOS
Track: Track C - Lasers, Optics and Spectroscopy


<p>Obtaining single shot electron diffraction patterns is highly desirable when dealing with samples that are either destroyed or display irreversible structural changes upon photo-excitation. Such single shot measurements demand highly charged pulses that contain in the order of 10<sup>5</sup> – 10<sup>6</sup> electrons. Maintaining femtosecond pulse duration in the presence of the inevitably large Coulomb forces inside such electron bunches is currently a major challenge in the field of ultrafast electron diffraction. One of the suggested solutions is to recompress the pulses. Conventional RF cavity compressors have been successfully constructed and implemented, but factors such as their bulkiness, high cost and difficulty of manufacturing constitute a limit to this approach. Here we present an alternative compressor concept based upon a radio frequency cavity shunted by a pair of gallium arsenide photoconductive semiconductor switches (PCSS). The PCSS’s are triggered by two synchronous femtosecond laser pulses, resulting in a low jitter 5 GHz oscillation of the cavity. We report here results from our prototype device, which has achieved compression of an electron pulse containing 40 000e<sup>-</sup>/pulse from a 14ps down to a 500fs duration, as confirmed by measurements from our in-house developed femtosecond streak camera. We believe that our electron bunch compressor device will be easier to implement and much more cost effective than traditional RF cavities.

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Short Paper



Room: Acro4

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