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Charge collection efficiency of scCVD diamond detectors at low temperatures

The charge collection efficiency (CCE) in electronic grade, single crystal chemical vapor deposition (scCVD) diamond detector was studied using different ions of the MeV energy range from room temperature down to 47 K. The measurements were performed by using the ion beam induced charge (IBIC) technique, with 0.8 MeV H+, 3 MeV He2+, 5.6 MeV Li2+, and 12.8 MeV C4+ ion beams. The total accumulated charge as a function of temperature was extracted from the measured pulse height spectra. A similar decreasing trend of the detector CCE with temperature was observed for all ion species. A plateau was observed from room temperature to 145 K followed by a sharp, step like, decrease in the temperature range of 65 K < T < 145 K. Below 65 K, the CCE reaches another plateau with small variations down to 47 K. The decrease in collected charge was observed in the same temperature window for each ion. However, the level of the CCE decrease varied. For He, Li and C, the CCE decreased to 24.7 ± 0.4 %, 23.6 ± 1.3 %, 25.9 ± 0.8 % respectively while 39.3 ± 0.8 % for H. The reduction of the CCE is in agreement with earlier reported results obtained by alpha particles which was associated with the changes in lifetime of excitons in diamond.

sc-CVD diamond ; IBIC ; Cryogenic temperature ; Ionizing radiation

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