arXiv subjects

Olivier Bourrion

Publications and source records attributed to Olivier Bourrion.

11 recordsLinked to original sources

arXiv2026

CONCERTO : Optimization of readout electronics

The CONCERTO millimeter-wave spectral-imaging instrument was deployed on the Atacama Pathfinder EXperiment (APEX), where it acquired science data between April 2021 and May 2023. The instrument features two focal-plane arrays, each composed of 2400 Microwave Kinetic Inductance Detectors (MKIDs). Each array is divided into six feedlines containing 400 MKIDs each, with each feedline read out by a dedicated FPGA-based board, KID_READOUT. The next-generation instrument aims to double the detector count per feedline, increasing it from 400 to 800 MKIDs. Achieving this requires a substantial scaling of the readout architecture and poses two key challenges for KID_READOUT: maintaining readout signal integrity and constraining firmware resource usage, as a direct upscaling of the existing design would exceed the available FPGA capacity. To overcome these limitations, we developed a Python-based, cycle-and bit-accurate digital twin of the full FPGA digital signal processing chain. This model enabled a detailed investigation of internal signal behavior and provided quantitative guidance for firmware optimization. Leveraging these insights, we identified the source of two spurs present in CONCERTO data and significantly reduced their amplitudes. At the same time, we achieved substantial reductions in firmware resource usage-39.0%pt in LUTs, 20.3%pt in flip-flops, and 28.98%pt in DSP slices-without degrading readout performance. The resulting architecture supports more than 800 MKIDs per feedline on the same hardware platform while preserving readout signal quality, offering a scalable and resource-efficient solution for future high-resolution millimeter-wave astronomical instruments.

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arXiv2026

A Digital Twin of the FPGA Digital Signal Processing Chain for MKIDs Readout: Root-Cause Analysis and Mitigation of Spurs

The KID_READOUT board, developed for the CONCERTO millimeter-wave astronomy instrument, implements FPGA-based digital frequency multiplexing to read out large arrays of Microwave Kinetic Inductance Detectors (MKIDs). The complexity of the implemented multirate DSP chain, which combines tones synthesis, interpolation, digital frequency translation, polyphase filter-bank (PFB) channelization, and digital down-conversion (DDC), makes analytical performance optimization difficult. To address this, we developed a cycle-and bitaccurate, Python-based digital twin of the FPGA readout firmware DSP chain. Using this model, we identified the origin of previously measured and unexplained spurs in the readout channels, tracing them to periodicity mismatches between the excitation and analysis paths and to insufficient suppression of negative-frequency components by the DDC filters. Based on these insights, we implemented a mitigation strategy that aligns the periodicities and improves the DDC filter characteristics, effectively eliminating the spurs with a minor increase in FPGA resource usage.

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arXiv2025

High-precision polarization measurements with Lumped Element Kinetic Inductance Detectors

This work aims to demonstrate that two arrays of Lumped Element Kinetic Inductance Detectors (LEKIDs), when employed in filled array configuration and separated by an external linear polarizer oriented at 45 degrees, can achieve the precision required by next-generation cosmological experiments. The focus here is on validating their ability to meet stringent uncertainty requirements, in particular for polarization angle reconstruction. To achieve this, the uncertainties in the reconstruction of the polarization angle have been characterized in the laboratory using a dedicated closed-circuit 100 mK dilution cryostat. This is optically coupled to a Martin-Puplett interferometer and a custom-designed sky simulator equipped with both photometric and polarized sources, allowing one to reproduce realistic ground-based observation conditions. This experimental setup allows us to generate intensity and polarization maps with diffraction-limited resolution, allowing us to determine the polarization angles and their associated uncertainties. The results show performance in line with expectations for the next generation CMB experiments. The polarization angle was reconstructed with an uncertainty of 6.5 arcmin.

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arXiv2024

The PolarKID project: polarization measurements with KIDs for the next generation of CMB telescopes

The goal of the PolarKID project is testing a new method for the measurement of polarized sources, in order to identify all the possible instrumental systematic effects that could impact the detection of CMB B-modes of polarization. It employs the KISS (KIDs Interferometer Spectrum Survey) instrument coupled to a sky simulator and to sources such as point-like black bodies (simulating planets), a dipole (extended source) and a polarizer. We use filled-arrays Lumped Element Kinetic Inductance Detectors (LEKIDs) since they have multiple advantages when observing both in a photometry and in a polarimetry configuration

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arXiv2024

CONCERTO: Instrument model of Fourier transform spectroscopy, white-noise components

Modern astrophysics relies on intricate instrument setups to meet the demands of sensitivity, sky coverage, and multi-channel observations. An example is the CONCERTO project, employing advanced technology like kinetic inductance detectors and a Martin-Puplett interferometer. This instrument, installed at the APEX telescope atop the Chajnantor plateau, began commissioning observations in April 2021. Following a successful commissioning phase that concluded in June 2021, CONCERTO was offered to the scientific community for observations, with a final observing run in December 2022. CONCERTO boasts an 18.5 arcmin field of view and a spectral resolution down to 1.45 GHz in the 130-310 GHz electromagnetic band. We developed a comprehensive instrument model of CONCERTO inspired by Fourier transform spectrometry principles to optimize performance and address systematic errors. This model integrates instrument noises, subsystem characteristics, and celestial signals, leveraging both physical data and simulations. Our methodology involves delineating simulation components, executing on-sky simulations, and comparing results with real observations. The resulting instrument model is pivotal, enabling a precise error correction and enhancing the reliability of astrophysical insights obtained from observational data. In this work, we focus on the description of three white-noise noise components included in the instrument model that characterize the white-noise level: the photon, the generation-recombination, and the amplifier noises.

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arXiv2023

CONCERTO: instrument and status

CONCERTO (CarbON CII line in post-rEionization and ReionizaTiOn) is a low-resolution Fourier transform spectrometer dedicated to the study of star-forming galaxies and clusters of galaxies in the transparent millimeter windows from the ground. It is characterized by a wide instantaneous 18.6 arcmin field of view, operates at 130-310 GHz, and was installed on the 12-meter Atacama Pathfinder Experiment (APEX) telescope at 5100 m above sea level. CONCERTO's double focal planes host two arrays of 2152 kinetic inductance detectors and represent a pioneering instrument to meet a state-of-the-art scientific challenge. This paper introduces the CONCERTO instrument and explains its status, shows the first CONCERTO spectral maps of Orion, and describes the perspectives of the project.

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arXiv2022

CONCERTO : Digital processing for finding and tuning LEKIDs

We describe the on-line algorithms developed to probe Lumped Element Kinetic Inductance Detectors (LEKID) in this paper. LEKIDs are millimeter wavelength detectors for astronomy. LEKID arrays are currently operated in different instruments as: NIKA2 at the IRAM telescope in Spain, KISS at the Teide Observatory telescope in Tenerife, and CONCERTO at the APEX 12-meter telescope in Chile. LEKIDs are superconducting microwave resonators able to detect the incoming light at millimeter wavelengths and they are well adapted for frequency multiplexing (currently up to 360 pixels on a single microwave guide). Nevertheless, their use for astronomical observations requires specific readout and acquisition systems both to deal with the instrumental and multiplexing complexity, and to adapt to the observational requirements (e.g. fast sampling rate, background variations, on-line calibration, photometric accuracy, etc). This paper presents the different steps of treatment from identifying the resonance frequency of each LEKID to the continuous automatic control of drifting LEKID resonance frequencies induced by background variations.

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arXiv2022

CONCERTO: a breakthrough in wide field-of-view spectroscopy at millimeter wavelengths

CarbON CII line in post-rEionization and ReionizaTiOn (CONCERTO) is a low-resolution spectrometer with an instantaneous field-of-view of 18.6 arcmin, operating in the 130-310 GHz transparent atmospheric window. It is installed on the 12-meter Atacama Pathfinder Experiment (APEX) telescope at 5100 m above sea level. The Fourier transform spectrometer (FTS) contains two focal planes hosting a total of 4304 kinetic inductance detectors. The FTS interferometric pattern is recorded on the fly while continuously scanning the sky. One of the goals of CONCERTO is to characterize the large-scale structure of the Universe by observing the integrated emission from unresolved galaxies. This methodology is an innovative technique and is called line intensity mapping. In this paper, we describe the CONCERTO instrument, the effect of the vibration of the FTS beamsplitter, and the status of the CONCERTO main survey.

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arXiv2017

The NIKA2 large field-of-view millimeter continuum camera for the 30-m IRAM telescope

Millimeter-wave continuum astronomy is today an indispensable tool for both general Astrophysics studies and Cosmology. General purpose, large field-of-view instruments are needed to map the sky at intermediate angular scales not accessible by the high-resolution interferometers and by the coarse angular resolution space-borne or ground-based surveys. These instruments have to be installed at the focal plane of the largest single-dish telescopes. In this context, we have constructed and deployed a multi-thousands pixels dual-band (150 and 260 GHz, respectively 2mm and 1.15mm wavelengths) camera to image an instantaneous field-of-view of 6.5arc-min and configurable to map the linear polarization at 260GHz. We are providing a detailed description of this instrument, named NIKA2 (New IRAM KID Arrays 2), in particular focusing on the cryogenics, the optics, the focal plane arrays based on Kinetic Inductance Detectors (KID) and the readout electronics. We are presenting the performance measured on the sky during the commissioning runs that took place between October 2015 and April 2017 at the 30-meter IRAM (Institut of Millimetric Radio Astronomy) telescope at Pico Veleta. NIKA2 has been successfully deployed and commissioned, performing in-line with the ambitious expectations. In particular, NIKA2 exhibits FWHM angular resolutions of around 11 and 17.5 arc-seconds at respectively 260 and 150GHz. The NEFD (Noise Equivalent Flux Densities) demonstrated on the maps are, at these two respective frequencies, 33 and 8 mJy*sqrt(s). A first successful science verification run has been achieved in April 2017. The instrument is currently offered to the astronomical community during the coming winter and will remain available for at least the next ten years.

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arXiv2016

Lumped Element Kinetic Inductance Detectors for space applications

Kinetic Inductance Detectors (KID) are now routinely used in ground-based telescopes. Large arrays, deployed in formats up to kilopixels, exhibit state-of-the-art performance at millimeter (e.g. 120-300 GHz, NIKA and NIKA2 on the IRAM 30-meters) and sub-millimeter (e.g. 350-850 GHz AMKID on APEX) wavelengths. In view of future utilizations above the atmosphere, we have studied in detail the interaction of ionizing particles with LEKID (Lumped Element KID) arrays. We have constructed a dedicated cryogenic setup that allows to reproduce the typical observing conditions of a space-borne observatory. We will report the details and conclusions from a number of measurements. We give a brief description of our short term project, consisting in flying LEKID on a stratospheric balloon named B-SIDE.

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arXiv2012

Kinetic inductance detectors for millimeter and submillimeter astronomy / Détecteurs à inductance cinétique pour l'astronomie millimétrique et sub-millimétrique

We present recent developments in Kinetic Inductance Detectors (KID) for large arrays of detectors. The main application is ground-based millimeter wave astronomy. We focus in particular, as a case study, on our own experiment: NIKA (Néel IRAM KID Arrays). NIKA is today the best in-the-field experiment using KID-based instruments, and consists of a dual-band imaging system designed for the IRAM 30 meter telescope at Pico Veleta. We describe in this article, after a general context introduction, the KID working principle and the readout electronics, crucial to take advantage of the intrinsic KID multiplexability. We conclude with a small subset of the astronomical sources observed simultaneously at 2 mm and 1.4 mm by NIKA during the last run, held in October 2010. Nous décrivons les récents développements concernant les grandes matrices de détecteurs à inductance cinétique (KID) dont l'application principale est l'astronomie millimétrique au sol. Nous détaillons en particulier notre propre caméra : NIKA (Néel IRAM KID Arrays) qui est aujourd'hui l'instrument le plus abouti mettant en oeuvre des KIDs. NIKA est une caméra bi-bande conçue pour le radiotélescope de 30 mètres de l'IRAM à Pico Veleta. Aprés avoir décrit le contexte instrumental dans lequel ils s'inscrivent, nous expliquerons le principe de fonctionnement des KIDs et de leur électronique de lecture, cruciale pour pouvoir tirer parti de leur potentiel de muliplexage. Pour finir, nous présentons quelques exemples d'observations effectuées par NIKA dans les bandes de 2 mm et 1,4 mm au cours de la dernière campagne d'observation en octobre 2010.

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