Edmond Turcu

X-ray lithography using a KrF laser-plasma source at h v ≈ 1 keV

Abstract Laser-plasma X-ray sources suitable for lithography with 1–2μm thick silicon-substrate masks are generated by focussing a low energy, repetitive, commercial KrF laser onto targets at irradiances ⩾ 10 13 W/cm 2 . Conversion efficiency from laser light to X-rays at hν ≈ 1 keV has been measured as a function of target irradiance and target atomic number. The best quantitatively measured conversion efficiency of 0.3% is obtained using a Ni target (Z = 28). A repetitive (2Hz) Ag target X-ray source is used to demonstrate microlithography by printing 0.5 μm lines and spaces into EBR-9 resist.

Enhancement of high harmonics generated by field steering of electrons in a two-color orthogonally polarized laser field

We demonstrate enhancement by 1 order of magnitude of the high-order harmonics generated in argon by combining a fundamental field at 1300 nm (10(14) W cm(-2)) and its orthogonally polarized second harmonic at 650 nm (2 × 10(13) W cm(-2)) and by controlling the relative phase between them. This extends earlier work by ensuring that the main effect is the combined field steering the electron trajectory with negligible contribution from multiphoton effects compared to the previous schemes with 800/400 nm fields. We access a broad energy range of harmonics (from 20 eV to 80 eV) at a low laser intensity (far below the ionization saturation limit) and observe deep modulation of the harmonic yield with a period of π in the relative phase. Strong field theoretical analysis reveals that this is principally due to the steering of the recolliding electron wave packet by the two-color field. Our modeling also shows that the atto chirp can be controlled, leading to production of shorter pulses.

Biosystem response to soft-X-rays irradiation: non-monotonic effects in the relevant biological parameters of yeast cells

SummarySoft-X-rays irradiation of yeast cells allows selective interference with different cellular structures. The monitoring of different physical parameters leads to substantial variations in the response to X-rays showing that monotonicity should not be taken for granted.

An ensemble of new techniques to study soft-X-ray-induced variations in cellular metabolism

An ensemble of new techniques has been developed to study cell metabolism. These include: CO2 production monitoring, cell irradiation with soft X rays produced with a laser-plasma source, and study of oscillations in cell metabolic activity via spectral analysis of experimental records. Soft X-rays at about 0.9 keV, with a very low penetration in biological material, were chosen to produce damages at the metabolic level, without great interference with DNA activity. The use of a laser-plasma source allowed a fast deposition of high doses. Monitoring of CO2 production allowed us to measure cell metabolic response immediately after irradiation in a continuous and non invasive way. Also a simple model was developed to calculate X-ray doses delivered to the different cell compartments following a Lambert-Bouguet–Beer law. Results obtained on Saccharomyces cerevisiae yeast cells in experiments performed at Rutherford Appleton Laboratory are presented.

Ultrafast Tr-ARPES with Artemis XUV Beamline

A new HHG XUV beamline at Artemis, user open-access facility at CLF, offers unique capabilities optimised for Tr-ARPES. Current result on ultrafast melting of Mott and charge order in TaS2 will be presented.

Monochromatised XUV Pulses for Ultrafast Science at the Artemis Facility

XUV pulses produced through high harmonic generation can probe electron dynamics in complex solid materials and in gas-phase atoms and molecules. This is demonstrated in gas-phase and condensed matter experiments at the Artemis facility.

Yield enhancement in multicolour high-order harmonic generation: Superposition of multiple un-related frequencies

We report observations and analysis of high harmonic generation driven by a superposition of fields at 1290 nm and 780 nm. These fields are not commensurate in frequency, as in previous experiments such as Ref. [1], and the superposition leads to an increase in the yield of the mid-plateau harmonics of more than two orders of magnitude compared to using the 1290 nm field alone. Significant extension of the cut-off photon energy is seen even by adding only a small amount of the 780 nm field. Fig. 1 plots the observed yield enhancements against harmonic energy and scanned over the temporal delay between the peaks of the two pulse envelopes. The figure shows two different intensity ratios, as stated in the caption. In both cases yield enhancement of up to two orders of magnitude is seen below 40 eV, together with smaller enhancements up to 80 eV, the limit of the MCP detector. This is a promising route to provide a greater photon number in attosecond pulse production [2], for applications in XUV imaging and time-resolved experiments [3].