Missions

The postdoctoral scholar will work on one or more of the following topics:
1. Development of an optical test bench to measure the response and the bandpass of detectors. An external Fourier Transform Spectrometer will be used together with a dilution fridge equipped with a window and optical filters. The precision of this
testbench will have to be consistent with the requirements of CMB-S4.
2. CMB-S4 simulation and data analysis to evaluate the scientific impact of instrumental and pipeline design choices and optimize the instrumental efficiency of CMB-S4.
3. Design and characterization of readout electronics using Application Specific Integrated Circuit (ASIC) and S4 sample detectors. A prototype of this detection chain will be installed and tested at APC in a dilution fridge.
The post-doc will work with the CMB-S4 project and collaboration, and in particular with Aritoki Suzuki, John Groh, Jacques Delabrouille and Reijo Keskitalo at LBNL in Berkeley, Adrian Lee at UCB, Damien Prêle and Michel Piat at the APC laboratory in Paris.

Activities

Essential
• Collect and characterize the essential properties of the CMB-S4 detection chain, as measured in the lab
• Implement corresponding models of instrumental systematics in the CMB-S4 simulation pipeline
• Interact with CMB-S4 collaboration instrumental working groups to assist them with providing simulations in response to the needs of the CMB-S4 science analyses.
• Contribute simulation tools to regular CMB-S4 software releases, including validation and documentation.
• Contribute to the operations of the simulation pipeline at NERSC to generate mock data for CMB-S4 data challenges.
• Independently plan and complete projects within CMB-S4 Data Management.
• Contribute to larger collaborative efforts with others from the CMB-S4 Project, and in particular the Instrument and Data Management team.
• Conduct original research independently and in collaboration, interacting with APC, CPB, LBNL and other investigators on similar or related scientific problems.
• Prepare research papers for publication and present results at seminars and conferences.

Marginal
• May mentor or oversee Ph.D. students.
• Other duties as assigned.

Skills

Essential
• Recent Ph.D. or equivalent in physics, astronomy, or a closely related field
• Experience in cosmology or astronomy research
• Experience with sub-millimeter/millimeter instruments
• Experience with data processing on Linux clusters and/or High Performance Computing systems
• Python programming skills
• Knowledge of astronomical data processing methods
• Ability to work as a team member
• Excellent written and oral communication skills

Marginal
• git code versioning, including branches and pull requests
• Databases
• Ability to mentor students

Work Context

The precise measurement of polarized fluctuations of the Cosmic Microwave Background (CMB) emission is a major objective of modern observational cosmology. So-called primordial B modes of CMB polarization, thought to have been generated in an early phase of cosmic inflation, would provide unique information about the origin of the Universe and fundamental laws of physics at very high energies. The faint amplitude of the expected signals, of order of a few nK, requires highly sensitive observations together with exquisite control of instrumental systematic errors that can be higher by a few orders of magnitude.
CMB-S4 (Stage 4) is a 4th generation ground-based instrument aiming at observing these signals with ultimate sensitivity. To that effect, the experiment will deploy a total of about 500 000 cryogenic detectors in 85 optics tubes distributed in a few small (SAT) and large (LAT) aperture telescopes, which will observe from Chile and Antarctica. This will make it the largest and most advanced CMB observatory ever constructed. The required sensitivity, precision and accuracy of the observations requires precise understanding of the instrument and optimization of the data analysis pipeline. CMB-S4 has recently been ranked as the top priority for the next decade by the US Particle Physics Project Prioritization Panel (P5).

Constraints and risks

The postdoc will be based at the Centre Pierre Binetruy (CPB, Berkeley) and is expected to share work between APC (Paris), CPB and LBNL (Berkeley) as a function of project needs.