## 3 Results and Discussion
### Isotope Production Irradiation  
Two main isotope production experiments were conducted. In the first irradiation, the FBG-based temperature probe was inserted such that the tip of the probe touched the target-body wall diametrically opposed to its insertion port. At the start of the irradiation, the temperature probe reported a value of 22.2 \({}^{\circ}\)C which agreed with the expected temperature of the target body when water cooled. The beam current was increased in small steps and increases in temperature and pressure as reported by the FBG-based sensors were observed. The increasing current corresponded to increases in fluid temperature and consequently pressure associated with heating of the fluid within the enclosed target body. The observed increases in temperature and pressure occurred almost instantaneously with the increase in beam current. The FBG temperature probe produced a signal that appeared to exhibit attenuated dynamics compared to what was expected. Further, considering that the water pressure is physical coupled to its temperature in this enclosed volume, it was expected that the FBG temperature probe would report a temperature signal similarly dynamic to that of the FBG-based and reference pressure transducers. It was concluded that since the temperature probe was inserted such that its tip was in contact with the aluminum wall of the target body, it was not measuring exclusively the fluid temperature but also the temperature of the target body, which attenuated the fluctuations in observed temperature. At the full beam current of 20 \(\mu\)A, the observed temperature rose to 47.67 \({}^{\circ}\)C. It was concluded that this reading was lowered by the temperature of the target-body wall and therefore it was not representative of the temperature of the target fluid exposed to the full beam current. The beam current decreased at around 400 s and the pressure and temperature measurements decreased as well. The observed data is illustrated in Figure 6.  
Figure 6: Results from the first isotope production experiment illustrating the results of an irradiation of naturally abundant purified water. The black curve shows the proton beam current. The red curve represents the readings of the reference pressure transducer attached to the target body. The green curve shows the readings of the Fibos FBG-based pressure transducer. The blue curve illustrates the readings of the Fibos FBG-based temperature probe in contact with the target body wall. The unit of the individual signals is listed in the legend. During the first isotope production experiment, the FBG-based pressure transducer reported a fluid pressure in agreement with the reference pressure transducer readings for the first \(\sim\)300 s of the test. Beyond the 300 s mark, the FBG-based transducer began to report pressure readings that were lower than those of the reference pressure transducer--a disagreement that continued to increase between the two signals. Investigation into this behavior suggested that the difference in time constants between the strain FBG and the temperature FBG inside the pressure transducer caused errors in the temperature compensation scheme. The temperature compensating FBG in the pressure transducer was separated from the strain FBG by a thermal mass. Based on the signals recorded, it was concluded that the pressure transducer was overcompensating for temperature. It had originally been calibrated under steady-state temperature and pressure conditions and the changing temperature during the experiment exacerbated the device's sensitivity to transient conditions in the temperature compensation scheme. Further analysis and recalibration of the pressure transducer may be required to also accommodate transient temperature conditions. The divergence from the reference pressure reading that occurred beyond 300 s may be due to the delay between the actual rise of the temperature in the liquid and the response of the temperature compensation by the FBG inside the pressure transducer.