Damage observed in silicon diodes after low energy pion irradiation

Damage induced by pions in silicon detectors

“…The stable damage constant measured 200 days after irradiation was found to be α = (3.5±0.2) × 10 -17 Acm -1 which is in good agreement with measurements made by others [5,9,10]. The average value is approximately 25% higher than the commonly accepted value for 1 MeV neutrons.…”

“…The long-term value of α presented here is in good agreement with the values presented in Ref. [5] of 3.6 × 10 -17 to 4.1 × 10 -17 Acm -1 which was measured 50 days after irradiations with momenta from 200 to 400 MeV/c. Dortmund report a value of (3.56±0.04) × 10 -17 Acm -1 [9], and Hamburg an average value of 3.9 × 10 -17 Acm -1 [10], both in good agreement with our data.…”

“…This value is slightly systematically lower than other values reported by Dortmund [9] and Aarnio et al [5], however, the annealing corrected value of α is notoriously sensitive to exact irradiating conditions and measurement procedure due to rapid early annealing. There was no difference observed between positive and negative pions.…”

“…The table also shows the values obtained by Aarnio et al [5] after a pion irradiation at PSI in the same running period. They fitted more exponentials owing to a longer measurement time, but, the three smallest time constants for both sets of data are in good agreement.…”

“…In addition, it appears that the damage caused by these pions is very similar to that caused by 1 MeV neutrons, where damage constants of the order of 8 × 10 -17 Acm -1 are reported, albeit with a spread of values [8]. Aarnio et al [5] report slightly higher pion damage constants of α = (10.4±0.7) × 10 -17 Acm -1 , α = (12.2±0.5) × 10 -17 Acm -1 , and α = (10.7±0.7) × 10 -17 Acm -1 for pion momenta of 200, 300 and 400 MeV/c, respectively, and Dortmund reports a value of 10.5 × 10 -17 Acm -1 [9]. So it appears that independent measurements vary a little; however, the damage-constant value corrected for self-annealing is very sensitive to the irradiation and measurement conditions and is of somewhat academic interest, therefore the emphasis is usually placed on the long-term, or stable damage constant, described next.…”