# X-ray-Induced Heating in the Vicinity of the X-ray Interaction Point
## 3 Results
### Temperature Measurement in Glass Capillary  
During X-ray exposure, the change in temperature around the X-ray exposure point was investigated. The tip of the RTD was aligned at a distance of approximately 250-300 \(\upmu\)m from the point where the X-rays were exposed to the quartz capillary filled with water, crystallization solution, or lysozyme crystal suspension (Figure 2). The X-rays were beamed continuously, and temperature changes were observed for 5 min. For water, an X-ray beam path was clearly observed; however, gas bubbles corresponding to radiation damage were  
Figure 1: Observation of X-ray-induced radiation damage at the beamline 7A at PLS-II. Time-lapse view of the radiation damage of (**A**) crystal suspension and (**B**) crystallization solution. The X-ray beam path and the gas bubbles are indicated by blue and yellow arrows, respectively. Scale bar indicates 250 \(\upmu\)m.  
not observed (Figure 2A). The temperature baseline was approximately 23.5 \({}^{\circ}\)C, and began to increase when exposed to X-rays, increasing to 24.0 \({}^{\circ}\)C in approximately 20 s. The rate of increase then slowed as temperature gradually rose by 1 \({}^{\circ}\)C every 100 s (Figure 2A). Afterwards, the temperature remained stable with a deviation in the range of approximately 0.15 \({}^{\circ}\)C (Figure 2A). When the X-ray shutter was closed, the water temperature gradually decreased and approached the initial temperature after approximately 100 s (Figure 2A).  
In the crystallization solution, a number of gas bubbles were clearly observed after 10 s, and the size of the gas bubbles increased with X-ray exposure time (Figure 2A). Although the formation of gas bubbles by radiation damage was a phenomenon that did not occur in water, in terms of temperature change, the crystallization solution showed a trend similar to that of water (Figure 2B).  
Figure 2: X-ray-induced radiation damage and temperature increase. (**A**) Time-lapse of the radiation damage for water, crystallization solution, and crystal suspension. (**B**) Two-dimensional profile of the temperature rising due to X-ray exposure. The gas bubbles corresponding to the radiation damage are indicated by yellow arrows. Scale bar indicates 250 \(\upmu\)m.  
For the lysozyme crystal suspension, the formation of gas bubbles corresponding to radiation damage was also observed on the X-ray beam path, with the gas bubble size increasing as X-ray exposure time increased (Figure 2A). The increase in temperature of the crystal suspension was similar to that of water or crystallization solution, but the temperature remained approximately 0.15 \({}^{\circ}\)C lower after the maximum temperature increase (Figure 2B).  
These results were tentatively attributed to the temperature increase during the X-ray absorption and emission processes as X-rays penetrated the materials. This indicates that the temperature change according to X-ray transmission can be affected by the X-ray absorption of the solutions, as well as the quartz capillary. The thickness of the capillary we used was 10 \(\upmu\)m, indicating that when X-rays pass through both walls of the capillary, the X-ray transmission of a 20 \(\upmu\)m thick quartz capillary was approximately 0.96 at 12.66 keV. Consequently, approximately 4% of the photons (and 1.2 \(\times\) 10\({}^{10}\) phs/s) were absorbed by a quartz capillary with a thickness of 20 \(\upmu\)m. This figure potentially indicates that the capillary may contain the heat generated from the absorption of X-rays. Accordingly, an RTD was inserted into the capillary without solution. When X-rays were transmitted through the capillary, the temperature of the RTD rose to a maximum of 24.3 \({}^{\circ}\)C and then showed a change of 24 \({}^{\circ}\)C \(\pm\) 0.1 \({}^{\circ}\)C. This indicates that the temperature change of approximately 0.6 \({}^{\circ}\)C in the capillary includes both the heat generated from the capillary and the material inside.