arXiv subjects

Felix Ehrler

Publications and source records attributed to Felix Ehrler.

3 recordsLinked to original sources

arXiv2022

A Beam Monitor for Ion Beam Therapy based on HV-CMOS Pixel Detectors

Particle therapy is a well established clinical treatment of tumors. More than one hundred particle therapy centers are in operation world wide. The advantage of using hadrons like protons or carbon ions as particles for tumor irradiation is the distinct peak in the depth dependent energy deposition, which can be exploited to accurately deposit dose in the tumor cells. To guarantee this, high accuracy of monitoring and control of the particle beam is of utmost importance. Before the particle beam enters the patient, it traverses a monitoring system which has to give fast feedback to the beam control system on position and dose rate of the beam while minimally interacting with the beam. The multi-wire chambers mostly used as beam position monitor have their limitations when fast response time is required (drift time). Future developments like MRI-guided ion beam therapy pose additional challenges for the beam monitoring system like tolerance of magnetic fields and acoustic noise (vibrations). Solid-state detectors promise to overcome these limitations and the higher resolution they offer can create additional benefits. This article presents the evaluation of an HV-CMOS detector for beam monitoring, provides results from feasibility studies in a therapeutic beam and summarizes the concepts towards the final large-scale assembly and readout system.

physics.med-ph↗

arXiv2020

Performance of CMOS pixel sensor prototypes in ams H35 and aH18 technology for the ATLAS ITk upgrade

Pixel sensors based on commercial high-voltage CMOS processes are an exciting technology that is considered as an option for the outer layer of the ATLAS inner tracker upgrade at the High Luminosity LHC. Here, charged particles are detected using deep n-wells as sensor diodes with the depleted region extending into the silicon bulk. Both analog and digital readout electronics can be added to achieve different levels of integration up to a fully monolithic sensor. Small scale prototypes using the ams CMOS technology have previously demonstrated that it can achieve the required radiation tolerance of $10^{15}~\text{n}_\text{eq}/\text{cm}^2$ and detection efficiencies above $99.5~\%$. Recently, large area prototypes, comparable in size to a full sensor, have been produced that include most features required towards a final design: the H35demo prototype produced in ams H35 technology that supports both external and integrated readout and the monolithic ATLASPix1 pre-production design produced in ams aH18 technology. Both chips are based on large fill-factor pixel designs, but differ in readout structure. Performance results for H35DEMO with capacitively-coupled external readout and first results for the monolithic ATLASPix1 are shown.

physics.ins-det↗

arXiv2020

Electrical characterization of AMS aH18 HV-CMOS after neutrons and protons irradiation

In view of the tracking detector application to the ATLAS High Luminosity LHC (HL-LHC) upgrade, we have developed a new generation of High Voltage CMOS (HV-CMOS) monolithic pixel-sensor prototypes featuring the AMS aH18 (180 nm) commercial CMOS technology. By fully integrating both analog and digital readout-circuitry on the same particle-detecting substrate, current challenges of hybrid sensor technologies, i.e., larger readout input-capacitance, lower production-yield, and higher production and integration cost, can be downscaled. The large electrode design using high-resistivity substrates actively helps to mitigate the charge-trapping effects, making these chips radiation hard. The surface and bulk damage induced in high irradiation environment change the effective doping concentration of the device, which modulates high electric fields as the reverse-bias voltage increases. This effect can cause high leakage current and premature electrical breakdown, driven by impact ionization. In order to assess the characteristics of heavily irradiated samples, we have carried out dedicated campaigns on ATLASPix1 chips that included irradiations of neutrons and protons, made at different facilities. Here, we report on the electrical characterization of the irradiated samples at different ambient conditions, also in comparison to their pre-irradiation properties. Results demonstrate that hadron irradiated devices can be safely operated at a voltage high enough to allow for high efficiency, up to the fluence of 2E15 neq/cm2, beyond the radiation levels (TID and NIEL) expected in the outermost pixel layers of the new ATLAS tracker for HL-LHC.

physics.ins-det↗