Signal formation in irradiated silicon detectors

Baldassarri, B.; Cartiglia, N.; Cenna, F.; Sadrozinski, H. F-W.; Seiden, A.

doi:10.1016/j.nima.2016.06.010

Cited by 8 publications

(8 citation statements)

References 7 publications

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“…We have developed a full simulation program, Weightfield2 (WF2) [17], [22], [23], with the specific aim of assessing the timing capability of silicon sensors with internal gain. The program has been validated by comparing its predictions for MIP and alpha particles with both measured signals and TCAD Sentaurus simulations, finding excellent agreement in both cases.…”

Section: Discussionmentioning

confidence: 99%

4D tracking with ultra-fast silicon detectors

2017

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The evolution of particle detectors has always pushed the technological limit in order to provide enabling technologies to researchers in all fields of science. One archetypal example is the evolution of silicon detectors, from a system with a few channels 30 years ago, to the tens of millions of independent pixels currently used to track charged particles in all major particle physics experiments. Nowadays, silicon detectors are ubiquitous not only in research laboratories but in almost every high-tech apparatus, from portable phones to hospitals. In this contribution, we present a new direction in the evolution of silicon detectors for charge particle tracking, namely the inclusion of very accurate timing information. This enhancement of the present silicon detector paradigm is enabled by the inclusion of controlled low gain in the detector response, therefore increasing the detector output signal sufficiently to make timing measurement possible. After providing a short overview of the advantage of this new technology, we present the necessary conditions that need to be met for both sensor and readout electronics in order to achieve 4D tracking. In the last section, we present the experimental results, demonstrating the validity of our research path.

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Section: Discussionmentioning

confidence: 99%

4D tracking with ultra-fast silicon detectors

2017

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“…In this section, the capability of the simulation program WF2 to reproduce the key features shown above is explored. WF2 includes the effects of radiation on charge trapping, as explained in [26], and acceptor removal and acceptor creation via deep traps, as explained in chapter 5 of [1]. The carriers drift velocities and the impact ionization mechanism, and their dependences on the electric field and temperature, are included in WF2 using parameterizations taken from the Synopsis Sentaurus manual [27] and from [28].…”

Section: Comparison With Wf2 Simulationmentioning

confidence: 99%

Properties of HPK UFSD after neutron irradiation up to 6e15 n/cm2

Galloway

Fadeyev

Freeman

et al. 2019

Nuclear Instruments and Methods in Physics Research Section A:

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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/cm 2 . The UFSD used in this study are circular 50 µm thick Low-Gain Avalanche Detectors (LGAD), with a 1.0 mm diameter active area. They have been produced by Hamamatsu Photonics (HPK), Japan, 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 90 Sr β-source. The leakage current, internal gain and the timing resolution were measured as a function of bias voltage at -20 o C and -30 o 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; the highest gain decreases from 70 before radiation to 2.6 after a fluence of 6e15 n/cm 2 . 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 found to be in agreement.

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“…The change of the LGAD pulse shape due to trapping after irradiation can be studied with WF2, of which version 3.5 incorporates trapping [6]. Since the characteristic trapping time is about 0.5 ns (corresponding to a trapping length of ~ 50 µm), on comparing the signals from thin and thick detectors shown in Fig 1.b one would expect that the longer pulses of thick detector will be effected much more by trapping than the short ones from thin LGAD.…”

Section: Lgad Pulse Shapesmentioning

confidence: 99%

Ultra-fast silicon detectors (UFSD)

Sadrozinski

Anker

Chen

et al. 2016

Nuclear Instruments and Methods in Physics Research Section A:

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Abstract-We report on measurements on Ultra-Fast Silicon Detectors (UFSD) which are based on Low-Gain Avalanche Detectors (LGAD). They are n-on-p sensors with internal charge multiplication due to the presence of a thin, low-resistivity diffusion layer below the junction, obtained with a highly doped implant. We have performed several beam tests with LGAD of different gain and report the measured timing resolution, comparing it with laser injection and simulations. For the 300μm thick LGAD, the timing resolution measured at test beams is 120ps while it is 57ps for IR laser, in agreement with simulations using Weightfield2. For the development of thin sensors and their readout electronics, we focused on the understanding of the pulse shapes and point out the pivotal role the sensor capacitance plays.

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Signal formation in irradiated silicon detectors

Cited by 8 publications

References 7 publications

4D tracking with ultra-fast silicon detectors

4D tracking with ultra-fast silicon detectors

Properties of HPK UFSD after neutron irradiation up to 6e15 n/cm2

Ultra-fast silicon detectors (UFSD)

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