Detector Simulation Physicist (EP-SFT-2026-152-GRAP)

In this role, you will develop and improve GPU-accelerated Monte Carlo detector simulation software within the Geant4 team, with a particular focus on optical photon transport. You will contribute to software design and implementation, physics validation against established CPU simulations, performance optimisation, and integration into experimental software frameworks.

Your responsibilities

• Design, develop, and integrate GPU algorithms for optical photon simulation within a Monte Carlo particle-transport framework.
• Compare and validate GPU simulation results against established CPU implementations.
• Develop unit, regression, and physics-validation tests.
• Profile applications, identify performance bottlenecks, and optimise computational performance.
• Collaborate with software teams from the Large Hadron Collider experiments to integrate GPU-enabled particle transport into their simulation frameworks.
• Engage with the international Geant4 collaboration and its user community, particularly in the area of optical photon simulation.
• Contribute to the documentation, maintenance, and long-term quality of the developed software.

Your profile

• Experience in developing scientific or physics-simulation software, preferably using modern C++.
• Experience with GPU programming or software development for heterogeneous computing architectures.
• Experience with software testing, numerical validation, performance profiling, or optimisation.
• Knowledge of Monte Carlo methods or experience with particle-transport simulation would be an advantage, particularly in the area of optical photon transport.
• Experience contributing to collaborative software projects or working within an international scientific environment would be an advantage.

Skills

• Programming languages and technologies: modern C++, CUDA, Python.
• GPU programming, heterogeneous computing, and performance optimisation.
• Git and collaborative software development.
• Unit testing, regression testing, and numerical validation.
• Experience with Monte Carlo particle-transport codes such as Geant4 would be considered an advantage.
• Debugging and profiling tools such as gdb, Compute Sanitiser, perf, Nsight Systems, or Nsight Compute would be considered an advantage.
• Spoken and written English, with a commitment to learn French.

Eligibility criteria:

• You are a national of a CERN Member or Associate Member State.
• You have a professional background in Physics, Computer Science, or a related (or a related field) and have either:
  • a Master's degree with 2 to 6 years of post-graduation professional experience;
  • or a PhD with no more than 3 years of post-graduation professional experience.
• You have never had a CERN fellow or graduate contract before.

Job closing date: 11.10.2026 at 23:59 CEST.

Contract duration: 24 months, with a possible extension up to 36 months maximum.

Working hours: 40 hours per week

Job flexibility: Hybrid

Target start date: 01-January-2027

This position involves:

• Work during nights, Sundays and official holidays, when required by the needs of the Organization.

Job reference: EP-SFT-2026-152-GRAP

Field of work: Applied Physics

Benchmark job: 200140 - Applied Physicist

Global Benefits

• A monthly net stipend of either 6372 or 7004 Swiss Francs per month depending on your degree.
• 30 days of paid leave per year plus 2 weeks annual closure.
• Coverage by CERN’s comprehensive health insurance scheme (for yourself, your spouse and children), and membership of the CERN Pension Fund.
• Family, child and infant monthly allowances depending on your individual circumstances.
• A relocation package (installation grant and travel expenses) depending on your individual circumstances.
• Possibility to extend your contract up to 36 months.
• On-the-job and formal training including language classes.

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