# Description of radiation damage in diamond sensors using an effective defect model

## TL;DR

This paper models radiation damage in diamond sensors used in high-energy physics experiments, linking microscopic defect levels to macroscopic charge collection efficiency loss under high particle rates.

## Contribution

It introduces an effective defect model using TCAD simulations to explain the non-linear rate-dependent polarization and charge collection efficiency loss in diamond sensors.

## Key findings

- Effective defect levels fit experimental data
- Simulation reproduces non-linear polarization effects
- Predicts signal loss at high particle rates

## Abstract

The BCML system is a beam monitoring device in the CMS experiment at the LHC. As detectors poly-crystalline diamond sensors are used. Here high particle rates occur from the colliding beams scattering particles outside the beam pipe. These particles cause defects, which act as traps for the ionization, thus reducing the CCE. However, the loss in CCE was much more severe than expected. The reason why in real experiments the CCE is so much worse than in laboratory experiments is related to the rate of incident particles. At high particle rates the trapping rate of the ionization is so high compared with the detrapping rate, that space charge builds up. This space charge reduces locally the internal electric field, which in turn increases the trapping rate and hence reduces the CCE even further. In order to connect these macroscopic measurements with the microscopic defects acting as traps for the ionization charge the TCAD simulation program SILVACO was used. Two effective acceptor and donor levels were needed to fit the data. Using this effective defect model the highly non- linear rate dependent diamond polarization as function of the particle rate environment and the resulting signal loss could be simulated.