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![[Figure 1]](il5070fig1mag.jpg)
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Figure 1
Schematic view of the electron-optical pulse picker in a time-of-flight momentum microscope operated at full multi-bunch filling of a storage ring. The depicted example corresponds to the situation at MAX II (100 MHz bunch pattern). The electron-optical system comprises three lens groups which transport and magnify the momentum image from the backfocal plane of the objective lens (left) to the delay-line detector (right). The sample emits a photoelectron pulse train of 100 MHz and each of the pulses (indicated by red triangles) contains the full spectrum. The high-frequency (HF) deflector is located between two narrow beam crossovers (pinholes 1 and 2). The deflector voltage U(t) (inset on top) deflects the electrons originating from the multi-bunch train, except for a short time interval where the voltage is zero, thus transmitting the electrons from the desired individual pulse through the second aperture (pinhole 2). This way, a 5 MHz sub-period of pulses is generated, which is dispersed in time-of-flight τ by the low-energy ToF section. The radial coordinate is strongly exaggerated; the screen shows a W 4f7/2 photoelectron diffraction pattern recorded at hν = 500 eV. Note that each red triangle represents the full 3D array I(kx,ky,τ); in the pinholes the momentum pattern is encoded as angular distribution. |
![[Figure 1]](il5070fig1.jpg)
 | JOURNAL OF SYNCHROTRON RADIATION |
ISSN: 1600-5775
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