The Photon Arrival and Length Monitor (PALM), a THz streak camera device developed by PSI for non-destructive hard x-ray measurements of photon pulse length and arrival time versus a pump laser[1], was brought to the SACLA XFEL[2] in Japan in a cross-calibration temporal diagnostics campaign after an initial experiment where only the PALM was being used[3]. The device was used with 9 keV pink beam and a 9.0 and 8.8 keV two-color mode, successfully measuring the temporal ifnromation of the pulses for several different FEL operating conditions. The most interesting achievement is the PALM’s ability to measure two arrival times of the two colorors as tey are shifted against each other by the FEL, opening up new possibilities in temporal accuracy for two-color experiments. SwissFEL will employ two such devices at the end stations for use by both operators and experimenters to improve the operation of the FEL and to better interpret experimental data.
References
[1]P. N. Juranić et. al, Journal of Instrumentation (2014) 9.
[2]T. Ishikawa et. al., Nature Photonics (2012) 6(8).
[3] P. N. Juranić et. al., Optics Express (2014) 22.
SACLA was inaugurated in March 2012 with two beamlines: BL3 for hard X-ray FEL and BL1 for wide range spontaneous emission. To enhance the research opportunities in soft X-ray region, the SCSS test accelerator, which was a prototype linac of SACLA and decommissioned in 2013, was upgraded, relocated to the SACLA undulator hall, and connected to BL1. The commissioning of this upgraded BL1 had been started from September in 2015, and user operation was started from June 2016. Currently, SASE-FEL pulses in the photon energy range of 20 to 150 eV are available and average pulse energy is about 70 μJ at 100 eV. We are developing beam diagnostic systems such as an arrival timing diagnostics between the SXFEL and the synchronized optical laser. We have further upgrade plans of the accelerator and the beamline. In this presentation, I will report the latest status and future upgrade plans of this beamline.
This article reports the progress in the beamlines at the SPring-8 Angstrom Compact free electron LAser (SACLA). The beamline optical and diagnostics systems have been upgraded to further accelerate the scientific applications of X-ray free-electron lasers (XFELs). End-station instruments have also been developed to provide user-friendly experimental platforms which allow efficient data collection. Along with the upgrades of beamlines and experimental stations, we have established reliable and efficient procedures of the beamline operation.
KEYWORDS: Free electron lasers, X-rays, Hard x-rays, Prototyping, Extreme ultraviolet, Electron beams, Synchrotron radiation, X-ray optics, Alternate lighting of surfaces, Current controlled current source
SACLA was inaugurated in March 2012 with two beamlines: BL3 for hard X-ray FEL and BL1 for wide range spontaneous emission. Currently, all user experiments have been performed at BL3 and BL2 that was constructed as the second hard XFEL beamline. To enhance research opportunities with softer X-ray FEL, we decided to relocate the SCSS test accelerator, which was a prototype of SACLA and decommissioned in 2013, to the SACLA undulator hall, to connect to BL1, and to generate EUV and soft X-ray FEL independently of the SACLA linac.
In addition, we started commissioning of the upgraded BL1 in September 2015, and successfully observe SASE lasing at a photon energy of 36 eV in October. We are now constructing the end station, and will start commissioning in June 2016. We will install two C-band accelerator units that increase an electron beam energy up to 750 MeV with a photon energy up to 100 eV in the summer of 2016. In this presentation, I will report the latest status of the beamline.
X-ray free-electron lasers (XFELs) that utilize intense and ultra-short pulse X-rays may damage optical elements. We investigated the damage fluence thresholds of optical materials by using an XFEL focusing beam that had a power density sufficient to induce ablation phenomena. The 1 μm focusing beams with 5.5 keV and/or 10 keV photon energies were produced at the XFEL facility SACLA (SPring-8 Angstrom Compact free electron LAser). Test samples were irradiated with the focusing beams under normal and/or grazing incidence conditions. The samples were uncoated Si, synthetic silica glass (SiO2), and metal (Rh, Pt)-coated substrates, which are often used as X-ray mirror materials.
SwissFEL is the Free Electron Laser (FEL) facility under construction at the Paul Scherrer institute (PSI), aiming to provide users with X-ray pulses of lengths down to 2 femtoseconds at standard operation. The measurement of the length of the FEL pulses and their arrival time relative to the experimental laser is crucial for the pump-probe experiments carried out in such facilities. This work presents a new device that measures hard X-ray FEL pulses based on the THz streak camera concept. It describes the prototype setup called pulse arrival and length monitor (PALM) developed at PSI and tested in Spring-8 Angstrom Compact Free Electron Laser (SACLA) in Japan. Based on the first results obtained from the measurements, we introduce the new improved design of the second generation PALM setup that is currently under construction and will be used in SwissFEL photon diagnostics.
X-ray free electron lasers (XFELs) with intense and ultra-short pulse X-rays possibly induce damage to optical elements.
We investigated the damage thresholds of optical materials by using focusing XFEL beams with sufficient power density
for studying ablation phenomena. 1-μm focusing beams with 10 keV photon energy were produced at the XFEL facility
SACLA (SPring-8 Angstrom Compact free electron LAser). The focusing beams irradiated samples of rhodium-coated
substrate, which is used in X-ray mirror optics, under grazing incident condition.
For chemically amplified EUV resists, secondary electrons derived from ionization events play a critical role
in the sensitization of acid generators. In this study, we show the dependence of acid generation efficiency on
dose rate (fluence per pulse duration) by using 61 nm free-electron laser (FEL) light irradiation. The
wavelength of 61 nm (20.3 eV) is applied because single incident photon induces only single ionization event,
in contrast to the 13.4 nm EUV photon that induces 4.2 ionization events on average. The acid yield
efficiency has enhances with decreasing the dose rate. It is suggested that high density ionization enhances the
multiple spur effect.
The paper is devoted to experimental and theoretical studies of ablation of condensed matter by optical (OL),
extreme ultraviolet (EUV) and X-ray lasers (XRL). Results obtained at two different XRL are compared. The
first XRL is collision Ag-plasma laser with pulse duration τL = 7 ps and energy of quanta hv=89.3 eV, while
the second one is EUV free electron laser (EUV-FEL) and has parameters τL = 0.3 ps and energy of quanta 20.2
eV. It is shown that ablation thresholds for these XRL at LiF dielectric are approximately the same. A theory is
presented which explains slow growth of ablated mass with fluence in case of XRL as a result of transition from
spallative ablation near threshold to evaporative ablation at high fluencies. It is found that the metal irradiated
by short pulse of OL remains in elastic state even in high shear stresses. Material strength of aluminum at very
high deformation rates V/V ~ 109 s-1 is defined.
F2 lasers are the light source of choice for microlithographic tools enabling structures below the 70 nm technology node. Accurate measurements of the spectrum of F2 lasers are therefore very important. We have succeeded in measuring the spectrum of an ultra line narrowed F2 laser using a VUV grating spectrometer calibrated with a 153 nm coherent light source (153CLS). As a first step in the development of a 157 nm coherent light source (157CLS), the less complex 153CLS has been built. Using resonant two-photon processes and four-wave mixing in Xe, this method provided a tunable laser system with high conversion efficiency and a very narrow linewidth, which can be approximated by a (delta) function. The 153CLS included a pulsed, single-mode tunable Ti:sapphire laser (768.0 nm), a third harmonic generation unit (256.0 nm) and an Xe gas cell. The 153CLS had a linewidth of 0.007pm (FWHM) and a power of 0.05mW at 1000 Hz. The VUV grating spectrometer and a Michelson interferometer for F2 lasers have also been developed. The instrument function of the spectrometer has been measured with the 153CLS. Experimental and theoretical instrument functions were in good agreement (FWHM: 0.30pm). The instrument function at 157 nm was therefore estimated to have the theoretical FWHM of 0.31 pm. The spectral linewidth of the line-selected F2 laser has been measured under various laser conditions with the spectrometer as well as with the interferometer. Results show good agreement between both measurements. The spectrum of the ultra line narrowed F2 laser was measured with the VUV grating spectrometer calibrated using the 153CLS. The laser's FWHM of the deconvolved spectrum was 0.29pm. The deconvolved spectral purity containing 95% of the total laser energy is less than 0.84pm.
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