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Plasma sparks from an electrical discharge machining (EDM) process were observed using fiber optics positioned in the dielectric oil. Measurement techniques were developed to observe the spark in the extremely noisy environment. Optical data were used along with current pulse wave forms from the EDM machine to study the temporal characteristics of the spark in both the pulse time and the pause time. During the pause time, extinction of the sparks was longer than previously thought—perhaps due to the remaining infrared radiation after the collapse of the spark. Further, an optical pattern was identified that indicated in advance when an arc was being formed instead of a spark. Spectral data of the plasma spark was obtained by using a scanning grating spectrometer in conjunction with crosscorrelation to maximize the signal-to-noise ratio. Average spark temperatures from the spectral data were found to be significantly higher than those previously predicted from energy balances. The results showed a shift in the optical spectra to longer wavelengths during the spark, showing that the spark temperature decreased with time. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The first dedicated PETICT centre in Norway was established at the Norwegian Radiumhospital in Oslo in 2005. Knowing that the introductions of PET-isotopes in nuclear medicine give increased occupational radiation dose to the technicians, a study was carried out in order to map the doses to staff members during different working operations and to see if any dose reducing measures were needed. The results of the study are in good agreement with other studies, and a technician dose of 20-25 nSv per injected MBq of 18F seems to be representative for such centres. For an average injected activity of 350 MBq per patient, the dose limit is reached after handling around 3000 patients annually. For an annual number of less than 500 patients at the centre and rotation of the staff, an annual individual dose for the technicians would realistically be less than 2-3 mSv. Even a major increase in the number of patients will not result in individual doses near the ICRP dose limit. [ABSTRACT FROM AUTHOR]