Microwave TM010 cavities as versatile 4D electron optical elements

Pasmans, P.L.E.M.; Ham, G.B. van den; Conte, Stefano Dal; Geer, S.B. van der; Luiten, O.J.

doi:10.1016/j.ultramic.2012.07.011

Cited by 32 publications

(39 citation statements)

References 18 publications

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“…The beam diameter changed by about ±5%, corresponding to a change of divergence by ∼0.3 mrad. This is similar to what is expected [31]. By calculating the change in longitudinal velocity acquired by electrons on diverging trajectories due to the measured lens effect [13], and noting that no rotational motion takes place in the cavity, we estimate the timing difference across the beam profile to be less than 1 fs.…”

Section: Spatial Distortionssupporting

confidence: 79%

“…In addition, the cavity's electric fields have radial components outside of the cavity's center that provide additional contributions to spatial focusing/defocusing. For non-relativistic beams, the magnetic effect is negligible [31]. It was recently calculated that electron lenses can produce temporal distortions on femtosecond scales [13].…”

Section: Spatial Distortionsmentioning

confidence: 99%

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Compression of single-electron pulses with a microwave cavity

Gliserin¹,

Apolonski²,

Krausz³

et al. 2012

New J. Phys.

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Few-femtosecond to attosecond electron pulses are required for advancing ultrafast diffraction and microscopy to the regime of electrons in motion. Here, we report the combination of a single-electron source with a microwave cavity for pulse compression. In such an arrangement, the electron pulses can become significantly shorter than the laser pulses used for electron generation. This comes at the expense of an increase in energy spread. We report the use of an energy analyzer for characterizing microwave-compressed singleelectron pulses. Phase effects, linearity, focal distances, incoming pulse durations and laser-microwave jitter are measured for three different synchronization approaches. The results demonstrate the applicability of a microwave cavity in the single-electron regime and identify jitter as the current limitation on the way to few-femtosecond, eventually attosecond pulses of single electrons.

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Section: Spatial Distortionssupporting

confidence: 79%

Section: Spatial Distortionsmentioning

confidence: 99%

Compression of single-electron pulses with a microwave cavity

Gliserin¹,

Apolonski²,

Krausz³

et al. 2012

New J. Phys.

View full text Add to dashboard Cite

show abstract

“…As a result, the relative timing jitter at the cavity position transfers to arrival timing jitter at the sample position. According to the analytical expression from Pasmans [36], the electron pulse arrival timing jitter at the sample position is equal to the RF phase jitter (i.e. relative timing jitter, which can be transformed to the RF phase jitter) under the condition of optimal compression (j=π/2) and full compression where the space-charge force can be neglected.…”

Section: Electron Pulse Duration and Jitter-amplification Effect Analmentioning

confidence: 99%

“…Taking the amplitude of the field E 0 and phase j 0 into the formula, we get the analytical temporal focus distance from the compression cavity d anal =13 cm as shown in figure 4(b). According to the analytical resolution in [36], for this distance, the arrival timing jitter is equal to the RF phase jitter (i.e. the relative timing jitter).…”

Section: Analytical Model For Coulomb Interaction-induced Jitter-amplmentioning

confidence: 99%

Coulomb interaction-induced jitter amplification in RF-compressed high-brightness electron source ultrafast electron diffraction

Pei

et al. 2017

New J. Phys.

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“…As a result, in recent years, much effort has been invested in techniques to correct for the spatial aberrations (Cs) of objective lenses in high resolution electron microscopy. For pulsed electron sources, such as those required for ultrafast transmission electron microscopy (UTEM), an alternative strategy for Cs aberration correction is possible through the use of the dynamic lensing properties of RF cavities [2] that, when operated in the appropriate oscillation mode, can possess negative spherical aberration [3]. For single-shot imaging UTEM, which requires ~ 10 8 electrons/pulse, simulations indicate that a large numerical aperture (NA > 0.1) objective lens will also be required to mitigate against deleterious space-charge effects [4] -effectively by minimizing the time electrons experience a high charge density.…”

mentioning

confidence: 99%

Circumventing Scherzer's Theorem: Large Numerical Aperture Objective Lenses for Pulsed Electron Microscopy

Rickman

Schroeder

2014

Microsc Microanal

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Scherzer's theorem states that all static round magnetic and electro-static electron lenses possess positive spherical aberration [1]. As a result, in recent years, much effort has been invested in techniques to correct for the spatial aberrations (Cs) of objective lenses in high resolution electron microscopy. For pulsed electron sources, such as those required for ultrafast transmission electron microscopy (UTEM), an alternative strategy for Cs aberration correction is possible through the use of the dynamic lensing properties of RF cavities [2] that, when operated in the appropriate oscillation mode, can possess negative spherical aberration [3]. For single-shot imaging UTEM, which requires ~ 10 8 electrons/pulse, simulations indicate that a large numerical aperture (NA > 0.1) objective lens will also be required to mitigate against deleterious space-charge effects [4] -effectively by minimizing the time electrons experience a high charge density. Here, we present a theoretical analysis of the possibility of using the focusing properties of RF cavities to compensate for the spherical aberration of large NA objective lenses for pulsed electron microscopy.Round (i.e., cylindrically symmetric) magnetic lenses focus an incident electron beam through a net radial force whose magnitude may be written in a power series; F r (r) = c 1 r + c 3 r 3 + . . . , where the coefficients c n are dependent upon the spatial distributions of the radial and axial lens fields. For the case of a perfect lens, where all parallel incident electrons no matter how far off axis are focused to the same axial point, c 3 and all higher coefficients are zero. Figure 1(a) shows a 50kV electron trajectory simulation for a simple, large-aperture, 10mm focal length, static magnetic lens (a coil with no pole pieces) which clearly indicates the expected positive spherical aberration in the focal region (c 3 > 0). In contrast, the spherical aberration is negative (c 3 < 0) for the spatial focusing action of a suitably synchronized cylindrical RF cavity oscillating on the transverse magnetic TM 01 o mode (Figure 1(b)). This is due to the J 1 (r) Bessel function variation of the azimuthal magnetic Βφ field which results in , where a is the radius of the RF cavity. A 'doublet' lens consisting of these two electron lenses may then be envisaged with a net zero value of c 3 . Figure 1 (c) shows the 50kV electron trajectory simulation for such a 10mm focal length doublet lens which exhibits excellent focusing properties over a NA of 0.1 (i.e., a focused beam semi convergence angle of 100mrad).The TM 010 RF cavity mode is also expected to exhibit spatial lensing due to the divergence of the oscillating axial electric field at the entrance and exit beam apertures [4], which suggests that the TM 011 RF mode, with zero oscillating electric field strength at the apertures, may be a more prac-tical. Other cylindrical RF cavity modes, such as the transverse electric (TE 01q ) modes commonly used in the telecommunications, are also expected to possess focusing p...

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Microwave TM010 cavities as versatile 4D electron optical elements

Cited by 32 publications

References 18 publications

Compression of single-electron pulses with a microwave cavity

Compression of single-electron pulses with a microwave cavity

Coulomb interaction-induced jitter amplification in RF-compressed high-brightness electron source ultrafast electron diffraction

Circumventing Scherzer's Theorem: Large Numerical Aperture Objective Lenses for Pulsed Electron Microscopy

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