Non-invasive measurement of X-ray beam heating on a surrogate crystal sample.
Cryocooling is a technique routinely used to mitigate the effects of secondary radiation damage on macromolecules during X-ray data collection. Energy from the X-ray beam absorbed by the sample raises the temperature of the sample. How large is the temperature increase and does this reduce the effectiveness of cryocooling? Sample heating by the X-ray beam has been measured non-invasively for the first time by means of thermal imaging. Specifically, the temperature rise of 1 mm and 2 mm glass spheres (sample surrogates) exposed to an intense synchrotron X-ray beam and cooled in a laminar flow of nitrogen gas is experimentally measured. For the typical sample sizes, photon energies, fluxes, flux densities and exposure times used for macromolecular crystallographic data collection at third-generation synchrotron radiation sources and with the sample accurately centered in the cryostream, the heating by the X-ray beam is only a few degrees. This is not sufficient to raise the sample above the amorphous-ice/crystalline-ice transition temperature and, if the cryostream cools the sample to 100 K, not even enough to significantly enhance radiation damage from secondary effects.
Snell
Edward H
EH
Hauptman Woodward Medical Research Institute, 700 Elicott Street, Buffalo, NY 14203, USA. esnell@hwi.buffalo.edu
Bellamy
Henry D
HD
Rosenbaum
Gerd
G
van der Woerd
Mark J
MJ
D003198:Computer Simulation; D018360:Crystallography, X-Ray / Q000379:methods*; D004307:Dose-Response Relationship, Radiation; D006358:Hot Temperature; D046911:Macromolecular Substances / Q000737:chemistry* / Q000528:radiation effects*; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation / Q000528:radiation effects; D011829:Radiation Dosage; D013817:Thermography / Q000379:methods*; D014965:X-Rays
D046911:Macromolecular Substances