TY - JOUR
T1 - Properties of HPK UFSD after neutron irradiation up to 6e15 n/cm2
AU - Galloway, Z.
AU - Fadeyev, V.
AU - Freeman, P.
AU - Gkougkousis, E.
AU - Gee, C.
AU - Gruey, B.
AU - Labitan, C. A.
AU - Luce, Z.
AU - McKinney-Martinez, F.
AU - Sadrozinski, H. F.W.
AU - Seiden, A.
AU - Spencer, E.
AU - Wilder, M.
AU - Woods, N.
AU - Zatserklyaniy, A.
AU - Zhao, Y.
AU - Cartiglia, N.
AU - Ferrero, M.
AU - Mandurrino, M.
AU - Staiano, A.
AU - Sola, V.
AU - Arcidiacono, R.
AU - Cindro, V.
AU - Kramberger, G.
AU - Mandić, I.
AU - Mikuž, M.
AU - Zavrtanik, M.
N1 - Publisher Copyright:
© 2019 Elsevier B.V.
PY - 2019/10/1
Y1 - 2019/10/1
N2 - In this paper we report results from a neutron irradiation campaign of Ultra-Fast Silicon Detectors (UFSD) with fluences of 1e14, 3e14, 6e14, 1e15, 3e15 and 6e15 neq/cm2. The UFSD used in this study are circular 50 μm thick Low-Gain Avalanche Detectors (LGAD), with a 1.0 mm diameter active area. Hamamatsu Photonics (HPK), Japan, produced the UFSD with pre-irradiation internal gain in the range 5–70 depending on the bias voltage. The sensors were tested pre-irradiation and post-irradiation with minimum ionizing particles (MIPs) from a 90Sr β-source. The leakage current, internal gain and the timing resolution were measured as a function of bias voltage at −20 °C and −30 °C. The timing resolution of each device under test was extracted from the time difference with a second calibrated UFSD in coincidence, using the constant fraction discriminator (CFD) method for both. The dependence of the gain upon the irradiation fluence is consistent with the acceptor removal mechanism; at −20 °C the highest gain decreases from 70 before radiation to 2 after a fluence of 6e15 n/cm2. Consequently, the timing resolution was found to deteriorate from 20 ps to 50 ps. The results indicate that the most accurate time resolution is obtained varying with fluence the CFD value used to determine the time of arrival, from 0.1 for pre-irradiated sensors to 0.6 at the highest fluence. Key changes to the pulse shape induced by irradiation, i.e. (i) the contribution of charge multiplication not limited to the gain layer zone, (ii) the shortening of the rise time and (iii) the reduced pulse height, were compared with the WF2 simulation program and were found to be in agreement.
AB - In this paper we report results from a neutron irradiation campaign of Ultra-Fast Silicon Detectors (UFSD) with fluences of 1e14, 3e14, 6e14, 1e15, 3e15 and 6e15 neq/cm2. The UFSD used in this study are circular 50 μm thick Low-Gain Avalanche Detectors (LGAD), with a 1.0 mm diameter active area. Hamamatsu Photonics (HPK), Japan, produced the UFSD with pre-irradiation internal gain in the range 5–70 depending on the bias voltage. The sensors were tested pre-irradiation and post-irradiation with minimum ionizing particles (MIPs) from a 90Sr β-source. The leakage current, internal gain and the timing resolution were measured as a function of bias voltage at −20 °C and −30 °C. The timing resolution of each device under test was extracted from the time difference with a second calibrated UFSD in coincidence, using the constant fraction discriminator (CFD) method for both. The dependence of the gain upon the irradiation fluence is consistent with the acceptor removal mechanism; at −20 °C the highest gain decreases from 70 before radiation to 2 after a fluence of 6e15 n/cm2. Consequently, the timing resolution was found to deteriorate from 20 ps to 50 ps. The results indicate that the most accurate time resolution is obtained varying with fluence the CFD value used to determine the time of arrival, from 0.1 for pre-irradiated sensors to 0.6 at the highest fluence. Key changes to the pulse shape induced by irradiation, i.e. (i) the contribution of charge multiplication not limited to the gain layer zone, (ii) the shortening of the rise time and (iii) the reduced pulse height, were compared with the WF2 simulation program and were found to be in agreement.
KW - Charge multiplication
KW - Fast silicon sensors
KW - Radiation damage
KW - Thin tracking sensors
KW - Time resolution
UR - https://www.scopus.com/pages/publications/85066338390
U2 - 10.1016/j.nima.2019.05.017
DO - 10.1016/j.nima.2019.05.017
M3 - Article
SN - 0168-9002
VL - 940
SP - 19
EP - 29
JO - Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
JF - Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
ER -