Development and characterization of a laser-plasma soft X-ray source for contact microscopy

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Vol. 411; pp. 35 - 43
• Main Authors: Ayele, M.G., Wachulak, P.W., Czwartos, J., Adjei, D., Bartnik, A., Wegrzynski, Ł., Szczurek, M., Pina, L., Fiedorowicz, H.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.11.2017
• Subjects: Contact microscopy; Gas-puff target; Laser-produced plasma; Water-window; Gas-puff target; Contact microscopy; Laser-produced plasma; Water-window
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/j.nimb.2017.03.082

In this work, we present a compact laser-produced plasma source of X-rays, developed and characterized for application in soft X-ray contact microscopy (SXCM). The source is based on a double stream gas puff target, irradiated with a commercially available Nd:YAG laser, delivering pulses with energy up to 740mJ and 4ns pulse duration at 10Hz repetition rate. The target is formed by pulsed injection of a stream of high-Z gas (argon) into a cloud of low Z-gas (helium) by using an electromagnetic valve with a double nozzle setup. The source is designed to irradiate specimens, both in vacuum and in helium atmosphere with nanosecond pulses of soft X-rays in the “water-window” spectral range. The source is capable of delivering a photon fluence of about 1.09×103photon/μm2/pulse at a sample placed in vacuum at a distance of about 20mm downstream the source. It can also deliver a photon fluence of about 9.31×102photons/µm2/pulse at a sample placed in a helium atmosphere at the same position. The source design and results of the characterization measurements as well as the optimization of the source are presented and discussed. The source was successfully applied in the preliminary experiments on soft X-ray contact microscopy and images of microstructures and biological specimens with ∼80nm half-pitch spatial resolution, obtained in helium atmosphere, are presented.