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Results on fabrication and experimental characterization of wire scanners (WS) with submicrometer spatial resolution are presented. Independently fabricated at PSI and FERMI by means of nanolithography, the proposed WS solutions consist of 900 and 800 nm wide free-standing stripes ensuring a geometric resolution of about 250 nm. The nanofabricated WS were tested successfully at SwissFEL where low-charge electron beams with a vertical size of 400–500 nm were characterized. Further experimental tests at 200 pC confirmed the resilience to the heat-loading of the structures. With respect to conventional WS consisting of a metallic wire stretched onto a frame, the nanofabricated WS allow for an improvement of the spatial resolution from the micrometer to the submicrometer level as well as of beam invasiveness thanks to an equivalent reduction of the impact surface of the scanning stripe. The present work represents an important milestone toward the goal—that PSI and FERMI are pursuing—to realize a standard WS solution with minimal invasiveness and submicrometer resolution.

SwissFEL is a x-rays free electron laser (FEL) driven by a 5.8 GeV linac under construction at Paul Scherrer Institut. In SwissFEL, wire scanners (WSCs) will be complementary to view-screens for emittance measurements and routinely used to monitor the transverse profile of the electron beam during FEL operations. The SwissFEL WSC is composed of an in-vacuum beam-probe—motorized by a stepper motor—and an out-vacuum pick-up of the wire signal. The mechanical stability of the WSC in-vacuum hardware has been characterized on a test bench. In particular, the motor induced vibrations of the wire have been measured and mapped for different motor speeds. Electron-beam tests of the entire WSC setup together with different wire materials have been carried out at the 250 MeV SwissFEL Injector Test Facility (SITF, Paul Scherrer Institut, CH) and at FERMI (Elettra-Sincrotrone Trieste, Italy). In particular, a comparative study of the relative measurement accuracy and the radiation-dose release of Al(99)∶Si(1) and tungsten (W) wires has been carried out. On the basis of the outcome of the bench and electron-beam tests, the SwissFEL WSC can be qualified as a high resolution and machine-saving diagnostic tool in consideration of the mechanical stability of the scanning wire at the micrometer level and the choice of the wire material ensuring a drastic reduction of the radiation-dose release with respect to conventional metallic wires. The main aspects of the design, laboratory characterization and electron beam tests of the SwissFEL WSCs are presented.

FERMI is a seeded free-electron laser (FEL) facility located at the Elettra laboratory in Trieste, Italy, and is now in user operation with its first FEL line, FEL-1, covering the wavelength range between 100 and 20 nm. The second FEL line, FEL-2, a high-gain harmonic generation double-stage cascade covering the wavelength range 20-4 nm, has also completed commissioning and the first user call has been recently opened. An overview of the typical operating modes of the facility is presented.