Micro-PIXE on thin plant tissue samples in frozen hydrated state: A novel addition to JSI nuclear microprobe

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Vol. 306; pp. 140 - 143
• Main Authors: Vavpetič, P., Pelicon, P., Vogel-Mikuš, K., Grlj, N., Pongrac, P., Jeromel, L., Ogrinc, N., Regvar, M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-07-2013
• Subjects: Biology; Cold heading; Element quantification; Focused ion beam; Foils; Freezing; Frozen; Frozen hydrated tissue; Goniometers; Micro-PIXE; Plants (organisms); Proton beams; RBS; Silicon nitride; STIM; RBS; Micro-PIXE; STIM; Frozen hydrated tissue; Focused ion beam; Biology; Element quantification
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/j.nimb.2012.12.035

Recently we completed a construction of a cryostat at Jožef Stefan Institute (JSI) nuclear microprobe enabling us to analyze various types of biological samples in frozen hydrated state using micro-PIXE/STIM/RBS. Sample load-lock system was added to our existing setup to enable us to quickly insert a sample holder with frozen hydrated tissue samples onto a cold goniometer head cooled with liquid nitrogen inside the measuring chamber.
Cryotome-cut slices of frozen hydrated plant samples were mounted between two thin silicon nitride foils and then attached to the sample holder. Sufficient thermal contact between silicon nitride foils and sample holder must be achieved, as well as between the sample holder and the cold goniometer head inside the measuring chamber to prevent melting of the samples. Matrix composition of frozen hydrated tissue is consisted mostly of ice. Thinning of the sample as well as water evaporation during high vacuum and proton beam exposure was inspected by the measurements with RBS and STIM method simultaneously with micro-PIXE.
For first measuring attempts a standard micro-PIXE configuration for tissue mapping was used with proton beam cross section of 1.2×1.2μm2 and a beam current of 100pA. The temperature of the cold goniometer head was kept below 130K throughout the entire proton beam exposure. First measurements of thin plant tissue samples in frozen hydrated state show minute sample degradation during the 10h period of micro-PIXE measurements.