Radiation Hardness of Silicon Detectors
- Paper number
IAC-05-C2.5.04
- Author
Mr. Ilias Tsagkas, University of Strathclyde in Glasgow, United Kingdom
- Year
2005
- Abstract
Introduction
Silicon detectors are widely used in spacecraft applications and system control. It is well worth to know the effect of cosmic radiation on silicon detectors, as it may result on degradation of their performance, limitation of their lifetime and as a consequence rise of their cost.
Background
The experiments, which are being described below are part of my experience as a trainee student at the Institute of Nuclear Physics of the National Center for Scientific Research "Demokritos" in Greece. During my training, I was involved in the Institute’s works for the program, called "Research and development On Silicon for future Experiments" (R.O.S.E). The ROSE collaboration was consisted of 38 international groups, working on detectors for particle physics experiments at the Large Hadrons Collider (L.H.C) of the European Centre for Nuclear Research (C.E.R.N) and it aimed the development of radiation hard silicon detectors that can operate beyond the limits of present devices.
Experiment
The main goal of the experiments at the Institute of Nuclear Physics in "Demokritos" was the study of the silicon detectors behaviour after their exposure to radiation. The radiation of the silicon detectors was done using proton beams, which were produced by the Institute’s 5 MV Tandem accelerator. First we irradiated the silicon detector, being at reverse bias and fully depleted, with a very small intensity beam of 7.5 MeV protons and we measured the Integrated Charge Collection signal, using the Data Acquisition system. We used an appropriate set-up, which deflected the main part of the beam into a different direction, so that the silicon detector was radiated by a very small number of protons. After completing the above work, we irradiated the silicon detector with a high intensity proton beam (up to 1nA), produced by the accelerator. We measured then again, at low intensity as previously, the performance of the detector. This measurement proved the degradation of the silicon detector to a very high degree. In the last part of the experiment the detector was cooled at 77 oK and the low intensity test was repeated. The silicon detector recovered its functionality and its signal was about 80
Results-Conclusion
A silicon detector was irradiated with an intense 7.5 MeV proton beam (1nA) with a total dose of 8.04x1013 protons/cm2. Based on the measurements that we performed, we concluded that the crystal’s structure suffered serious damage. Further research has proved that if the silicon detector is cooled in liquid nitrogen temperature (77 K) after its radiation, it regains its initial properties approximately by 80It’s obvious that the results of the above project are of special interest to space research due to the wide usage of silicon detectors in space systems.
- Abstract document