Thermal and mechanical study of a parametrised cryostat model for optical characterisation of upcoming CMB experiments

Abstract

Current and future experiments observing the cosmic microwave background require a detailed understanding of optical performance at cryogenic temperatures. Pre-deployment analysis of optics can be performed in custom-engineered cryogenic test beds, such as Mod-Cam, a first light camera for the CCAT project. This work presents studies of the mechanical and thermal performance of CryoSim, a model of a generic cylindrical 4-K cryostat cooled with a commercial pulse tube cryocooler that can be used to characterise optical components and full reimaging optical systems. CryoSim is extensively parametrised, allowing the joint analysis and optimisation of mechanical and thermal performance via finite element methods. Results from this model are validated against measured cooldown data of the Mod-Cam cryostat. Due to the extensive parametrisation of the model, significant modifications of the cryostat geometry may be implemented to be representative of any system the scientific community may desire, and validation of thermal and mechanical performance can be carried out rapidly.

Thomas Gascard

Postdoc

In the hope to contribute to the current efforts of the Cosmology comunity to unveil the early stages of the Universe and its evolution, I did a PhD. in instrumentation for cosmology applications at Cardiff University, which covers design methods, fabrication and experimental characterisation of a Metamaterial-based Lenslet (MetaL) prototype coupled to an antenna fed detector plane. I then joined the CMBeam group to carry on experimental characterisation and qualification of optics for futur cosmology experiments.

Rustam Balafendiev

PhD Student

Rustam Balafendiev received the M.Sc. degree in radiophysics from the School of Physics and Engineering, ITMO University, Saint Petersburg, Russia, in 2021 and his first PhD degree at the same university in 2025. His current research interests include metamaterial applications in CMB instrumentation as well as the use of wire metamaterials in holography experiments.

Jón E. Guðmundsson

Professor

Professor of astrophysics at the University of Iceland and senior research scientist at Stockholm University.