Humboldt-Universität zu Berlin - Mathematisch-Naturwissen­schaft­liche Fakultät - Experimentelle Elementarteilchenphysik

Research towards building a novel (Digital) Calorimeter

Calorimeters in particle physics are used to detect particles and measure their energy. This happens by absorbing the particle and in that process measuring its energy. An example of such a calorimeter is the liquid argon calorimeter of the ATLAS experiment: Here, a particle is absorbed and converted within lead-steel absorbers to a shower of low-energetic particles. These shower particles then create so-called scintillation light in the liquid argon which is interleaved with the absorbers. By measuring the “amount” (i.e. energy sum) of that light, one can deduce the energy of the incident particle.


Developing Digital Calorimeters


The fundamental difference of a digital calorimeter is that it measures the number of particles instead of their energy. As the deposited energy in the detector can naturally fluctuate due to the nature of quantum mechanics, it might be advantageous to not measure the energy itself but just count particles and deduce their energy. This is what we are studying in collaboration with DESY Zeuthen and research groups in the UK.

Our research today: the DECAL sensor


In our current project, we are investigating a depleted monolithic active pixel sensor (DMAPS) device called DECAL. This sensor is designed to measure the passing of all shower particles as they create electron-hole pairs in the sensor’s silicon. It has a very fine granularity, but its electronic readout intelligently combines the information to be able to handle the data rates expected in future particle physics experiments.

Our laboratory


At Humboldt-Universität, we have multiple test stands where we are measuring the characteristics of the DECAL sensors. We have stations that allow for electric tests, measure signals through induced laser radiation, or use radioactive sources to test the properties of the sensors. Our readout system uses field programmable gate arrays (FPGAs). The communication happens through software written in C++.

Previous Studies performed by Master/Bachelor students


Previous thesis projects consisted of characterization of the bias voltage of the sensor, its energy calibration, or investigating the impact of the signal readout at high occupancy.

The students also learned and developed the basic operation of silicon sensors such as tuning the sensor so that every pixel unit of the sensor reacts the same to identical signals.

These studies were accomplished also through the usage of radioactive sources and X-rays.

Potential projects for bachelor and master theses or internships

All projects require basic programming knowledge. The readout software is written in C++ using CERN’s ROOT package. For all tasks, you will be required to manipulate the software and write new functions to perform the required studies. In the time planning of all projects, we have allocated time for you to learn the necessary skills. For example, in a previous bachelor project, the student knew only basic Python programming and was able to learn the necessary skills to perform the bachelor project without issues.

You will find a list of potential projects under this link. This list can be extended and further projects can be developed depending on the student’s skills and interests. If you are interested in working with us, please contact Dr Hannsjörg Weber (, Prof. Cigdem Issever (, or Prof. Steven Worm (