Abstract
Brightness is a key figure of merit for charged particle beams, and time-resolved brightness measurements can elucidate the processes involved in beam creation and manipulation. Here we report on a simple, robust, and widely applicable method for the measurement of beam brightness with temporal resolution by streaking one-dimensional pepperpots, and demonstrate the technique to characterize electron bunches produced from a cold-atom electron source. We demonstrate brightness measurements with 145 ps temporal resolution and a minimum resolvable emittance of 40 nm rad. This technique provides an efficient method of exploring source parameters and will prove useful for examining the efficacy of techniques to counter space-charge expansion, a critical hurdle to achieving single-shot imaging of atomic scale targets.
Highlights
Charged particle beams are integral to many applications from the Large Hadron Collider at CERN to radiotherapy and other forms of medical treatment [1,2]
We present a technique for measuring time-resolved brightness by combining pepperpot emittance measurements with beam streaking, and demonstrate the method with electrons generated from a cold-atom electron source (CAES)
Electron bunches produced by field ionization are known to have a duration of order 10 μs as the electrons slowly tunnel across the barrier formed by the Stark-shifted Coulomb potential [38], whereas bunches produced from above-threshold direct ionization had a duration determined by the blue ionization laser pulse duration of 5 ns
Summary
Charged particle beams are integral to many applications from the Large Hadron Collider at CERN to radiotherapy and other forms of medical treatment [1,2]. We present a technique for measuring time-resolved brightness by combining pepperpot emittance measurements with beam streaking, and demonstrate the method with electrons generated from a cold-atom electron source (CAES). Time-resolved brightness measurements of a CAES can provide information on the effects of techniques to counter space-charge expansion [21], details of the varying ionization processes involved [22], and on beam coherence which is important for potential application to ultrafast electron diffraction (UED). The streaked pepperpot method presented here allows the transverse velocity spread of the liberated electrons to be measured as a function of time, which can illuminate the underlying atomic ionization processes and provide a diagnostic which could allow optimization of electron bunch brightness in the future
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