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Geant4 Jobs in California (NOW HIRING)

Nuclear Engineer

San Leandro, CA · On-site

$105K - $155K/yr

Develop and apply Monte Carlo simulations such as MCNP, Geant4, or FLUKA for particle transport, shielding, dose assessment, and detector performance. * Design and optimize radiation shielding for ...

Experience with radiation transport tools such as MCNP, FLUKA, or Geant4 . * Experience supporting DOE, national laboratory, or similar regulated environments . * Experience with installation ...

Familiarity with radiation transport and shielding analysis tools (NOVICE, FASTRAD, GEANT4). * Familiarity with circuit simulation tools such as LTSpice or PSpice. * Familiarity with space charging ...

New

Use computational tools (e.g., GEANT4, MCNPX, NOVICE, SpaceRad, CREME) to model radiation transport through spacecraft shielding * Root-Cause Analysis:Investigate radiation-induced anomalies and ...

Radiation Engineer II

Long Beach, CA · On-site

$95K - $130K/yr

Familiarity with radiation transport and shielding analysis tools (NOVICE, FASTRAD, GEANT4) * Familiarity with circuit simulation tools such as LTSpice or PSpice * Familiarity with space charging ...

MCNP, NOVICE, FASTRAD, GEANT4, OLTARIS) * Familiarity with the following: * radiation assessments and mitigation for human space crews * radiation effects on spacecraft materials * laboratory ...

Geant4 information

What is Geant4?

Geant4 is a software toolkit for the simulation of the passage of particles through matter, widely used in high energy physics, nuclear experiments, and medical physics. It allows scientists and engineers to model how particles interact with complex geometries and materials, helping to design detectors and optimize experiments. Written in C++, Geant4 provides a flexible and extensible framework for simulating physics processes such as electromagnetic, hadronic, and optical interactions. The toolkit is developed by an international collaboration and is open-source, making it accessible to researchers around the world.

What are the key skills and qualifications needed to thrive as a Geant4 simulation developer?

To thrive as a Geant4 Simulation Developer, you need strong proficiency in C++ programming, a solid background in physics or engineering, and experience with Monte Carlo particle transport simulations. Familiarity with the Geant4 toolkit, scientific computing libraries, and version control systems like Git is typically required, and advanced degrees or certifications in physics or related fields are highly beneficial. Analytical thinking, problem-solving skills, and effective collaboration are essential soft skills for excelling in this role. These competencies are crucial for developing accurate simulations, troubleshooting complex issues, and supporting research or engineering projects in scientific and medical domains.

What are some common challenges faced by Geant4 developers when integrating simulations into larger research projects?

One common challenge Geant4 developers encounter is ensuring seamless integration of complex simulations into multidisciplinary research environments, which often involve collaboration with scientists, engineers, and software teams. This typically requires adapting simulation outputs to match the data formats and analysis workflows of the broader project, as well as maintaining code compatibility with evolving software dependencies. Effective communication and a solid understanding of project requirements are crucial to address these challenges and to contribute meaningful results to the team’s goals.

What is the difference between Geant4 vs Medical Physicist?

AspectGeant4Medical Physicist
Required CredentialsPhysics or engineering degree, programming skillsPhysics or medical physics degree, certification (e.g., ABR)
Work EnvironmentResearch labs, simulation developmentHospitals, clinics, radiation therapy centers
Industry UsageParticle physics, radiation simulationMedical imaging, radiation therapy, diagnostics

While Geant4 focuses on developing and implementing physics simulations for research, Medical Physicists apply physics principles to diagnose and treat patients using radiation. Both roles require strong physics backgrounds, but their work environments and applications differ significantly.

What cities in California are hiring for Geant4 jobs?

Cities in California with the most Geant4 job openings:

Infographic showing various Geant4 job openings in California as of August 2026, with employment types broken down into 92% Full Time, and 8% Contract. Highlights an 92% In-person, and 8% Remote job distribution.

Nuclear Engineer

Fuse

San Leandro, CA • On-site

$105K - $155K/yr

Full-time

Medical, Dental, Vision, PTO

Re-posted 28 days ago


Job description

About Fuse

We are building one of the most potentially consequential companies of the century. Our mission is to accelerate the world's transition to fusion energy while safeguarding humankind. This is not a normal company. This is not a normal job. We are committed for the long term to win. 

About the Role

As a Nuclear Engineer at Fuse, you'll bring expertise in particle transport, Monte Carlo simulation, radiation shielding, and radiation diagnostics to our fusion facility.

You'll develop and implement radiation diagnostics for facility operations and experimental characterization and work closely with physicists and engineers to advance our diagnostic capabilities.

Core Responsibilities
  • Implement and optimize neutron and gamma diagnostic systems for radiation characterization in fusion experiments and conduct experimental validation of neutron and gamma detection systems.

  • Analyze radiation data to support experimental campaigns, including source characterization, spectral unfolding, and spatial/temporal diagnostics.

  • Perform radiation-transport analysis to improve system performance and safety.

  • Develop and maintain radiation test environments for detector calibration and material testing.

  • Develop and apply Monte Carlo simulations such as MCNP, Geant4, or FLUKA for particle transport, shielding, dose assessment, and detector performance.

  • Design and optimize radiation shielding for mixed neutron and gamma environments.

  • Support meteorological assessments related to radiation dispersion and environmental safety.

  • Analyze radiation data for operational safety, shielding effectiveness, and compliance with regulatory requirements.

  • Collaborate with multidisciplinary teams on fusion technology development and radiation-safety initiatives.

Minimum Qualifications
  • Master's or PhD in Nuclear Engineering, Physics, or a related field.

  • Strong experience in Monte Carlo particle-transport simulations using MCNP, Geant4, FLUKA, or similar tools.

  • Hands-on experience with neutron and gamma detection techniques.

  • Knowledge of radiation shielding, dose calculations, and safety assessments.

  • Experience in radiation metrology and calibration techniques.

  • Proficiency in data analysis and programming using Python, MATLAB, C++, or similar tools.

  • Familiarity with regulatory frameworks including CNSC, NRC, and IAEA standards.

Preferred Qualifications
  • Experience working in fusion/fission facilities or similar combined neutron-gamma radiation environments.

  • Background in high-energy neutron/gamma transport and shielding.

  • Knowledge of advanced radiation-detection technologies.

What We Value
  • Give a shit. Build things you're proud of.

  • Take responsibility. If something is broken and you can fix it, fix it. See things through.

  • Move fast. Make decisions, learn quickly, and keep moving forward.

  • Think bigger. Simplify relentlessly. Don't default to the safe answer.

  • Disagree and commit. The best idea wins. Once a decision is made, we move.

  • Desire to win. This is hard. Expect intensity. We are here to win.

  • Plan B is to make Plan A work.

Additional Requirements
  • Must be able to travel and work extended hours/weekends as needed.

  • Security Clearance

  • This role may require the ability to obtain and maintain a U.S. government security clearance.

Benefits
  • Medical, dental, and vision coverage.

  • Relocation assistance for roles that require it.

  • Flexible time off. Take what you need, no accrual tracking.

  • 2 weeks of paid time off built into the end of each year, subject to team and business needs.

  • Supportive leave of absence policies.

  • Paid leave for new parents.

ITAR Requirements

To conform to U.S. Government technology export regulations, including the International Traffic in Arms Regulations (ITAR), you must be a U.S. citizen, lawful permanent resident of the U.S., protected individual as defined by 8 U.S.C. 1324b(a)(3), or eligible to obtain the required authorizations from the U.S. Department of State.

Equal Opportunity

Fuse is an Equal Opportunity Employer; employment with Fuse is governed on the basis of merit, competence, and qualifications and will not be influenced by race, color, religion, gender, national origin/ethnicity, veteran status, disability status, age, ancestry, immigration status, sexual orie

Compensation Range: $105K - $155K