I wrote my master thesis at the Department of Physics between May and November 2003. My thesis is mostly a literature based study but I also made some research on my own.
If you are interested you can download my thesis in portable
document format: [PDF].
Unfortunately my thesis is written in finnish. For those without the
knowledge of finnish language I have here the abstract of the work in
english:
The electronics used in space applications may easily be damaged by the high energy particles of space radiation. Therefore the semiconductor devices used in space must be tested in laboratory before use. In the University of Jyväskylä Department of Physics (JYFL) there is a test site for irradiation studies. In JYFL accelerator laboratory the cyclotron is used to produce high energy particles to simulate the space radiation. The tests are carried out at the RADEF station (Radiation Effects Facility).
During the last few years the electronics industry has started using SMD (Surface Mount Device) technology in all semiconductors. The irradiation study of these devices is different from traditional semiconductor devices because the SMDs can not be irradiated from the front-side of the devices. Because the SMDs are radiated from the back-side of the devices, the particles must travel through the substrate of the semiconductor before they reach the active areas of the device. According to irradiation standards set by ESA (European Space Agency) the penetration range of the particles used in irradiation has to exceed the value of 100 um.
For the range to be enough the energy of the particles must be over 10.3 MeV/u. To achieve this with the JYFL K-130 cyclotron the irradiation should be done with particles having mass-to-charge ratio of less than 3.55. During the year 2003 some research was done to produce higher charge states with the ECR ion source. It has been planned that a TWTA amplifier will be used to the ion source to make two-frequency heating possible. Though the TWTA will improve the production of higher charge states dramatically, the intensity of the highest mass ions needed will still be weak. To detect this low intensity beam after the cyclotron, the beam diagnostics of the laboratory had to be improved. A new integrating ammeter was designed.
A new ion cocktail has been designed to be used after the TWTA amplifier is acquired. According to our calculations the best ion cocktail for RADEF consists of the following ions: 14N4+, 28Si8+, 56Fe16+, 84Kr24+ and 129Xe37+. The mass-to-charge ratio of the cocktail is 3.49 and the energy of the ions is 10.7 Mev/u. Range of the ions in silicon is over 100 um. With this new ion cocktail irradiation studies of SMDs can be done at the RADEF station in the future.