Characterisation of irradiated thin silicon sensors for the CMS phase II pixel upgrade

Abstract

The high luminosity upgrade of the Large Hadron Collider, foreseen for 2026, necessitates the replacement of the CMS experiment's silicon tracker. The innermost layer of the new pixel detector will be exposed to severe radiation, corresponding to a 1 MeV neutron equivalent fluence of up to eq = 2×10 16 cm −2 , and an ionising dose of ≈5 MGy after an integrated luminosity of 3000 fb −1 . Thin, planar silicon sensors are good candidates for this application, since the degradation of the signal produced by traversing particles is less severe than for thicker devices. In this paper, the results obtained from the characterisation of 100 and 200 µm thick p-bulk pad diodes and strip sensors irradiated up to fluences of eq = 1.3 × 10 16 cm −2 are shown.

Increase of the photoconductivity quantum yield in silicon irradiated by neutrons to extremely high fluences

“…[8,10], had proved their dependences on the deep level densities in the samples irradiated to various neutron fluences. The intrinsic photocurrent, according to equation (1), should also be dependent on the lifetime and mobility of the charge carriers; however, they do not contribute to the spectral dependencies in the samples with passivated surfaces. It is seen in figure 4 that the quantum yield starts to grow well above the bandgap as indicated by the thin arrows in the samples irradiated to 1 × 10 15 and 3 × 10 16 n cm −2 .…”

“…Silicon particle detectors, which play the central role in high energy physics research, suffer from a reduction of efficiency due to radiation damage. The challenge of retaining the required efficiency in these detectors with increasing irradiation fluences can be addressed either by increasing the bias voltage following irradiation [1] or by sophisticated detector designs, as e.g. demonstrated for the Low Gain Avalanche Diode (LGAD) technology [2,3], in which an implanted ion * Author to whom any correspondence should be addressed.…”

EUTelescope: A modular reconstruction framework for beam telescope data

“…The ALiBaVa cluster data stream is then merged with the clustered telescope data using the AlibavaMerger processor. Subsequently, the analysis chain as exemplified in section 3 is followed and detailed in references [36,37].…”

Increase of the surface recombination velocity at high bias voltage in silicon irradiated by neutrons to extremely high fluences

“…The challenges of its application in HEP are related to the necessity to increase the range of fluence at which radiation detectors retain the required sensitivity. This can be realized by increasing the bias voltage, adjusted to the irradiation fluence [2] or by the novel design and engineering of sophisticated detectors such as, e.g. a low gain avalanche detector (LGAD) [3][4][5], in which an implanted layer of ions creates an effective multiplication of the non-equilibrium carriers.…”