The CMB-S4 experiment will require a large number of working superconducting connection flexes. We present here our two years work toward this objective based on cables previously designed at CEA/Irfu. The progress achieved in a collaboration including APC/In2p3/CNRS AstroParticule & Cosmology (APC), French National Centre for Scientific Research (CNRS), SLAC National Accelerator Laboratory (SLAC), and the Cosmic microwave background (CMB) project is reported here. The fabrication process, quality improvements, controlled cleanroom conditions, and production verification required to meet the strict specifications are presented.

Cryogenic low-noise amplifiers (LNAs) are critical components for the readout of cryogenic sensors. Placing readout circuitry in close proximity to the detector at cryogenic temperatures minimizes the length of interconnections prior to the first amplification stage. Low-temperature operation can also significantly enhance LNA performance. However, microelectronics foundries do not typically provide device models for cryogenic operation. Therefore, characterization and validation of the technology at these temperatures are required before designing a full integrated circuit. This article proposes a conceptual design for a cryogenic LNA optimized for the readout of a superconducting quantum interference device. To manage power dissipation at cryogenic temperatures, the LNA is also designed for operation at intermediate temperatures. Consequently, the target operating temperature range is from $\bm 77-300 K. The design focuses on a fully differential voltage amplifier to achieve high common-mode noise rejection. The LNA's first stage is based on a differential pair of SiGe heterojunction bipolar transistors (HBTs), selected for their low-noise and high-speed characteristics. Operating HBTs at cryogenic temperatures enhances both transconductance and current gain. The design is implemented in IHP's 130 nm SiGe BiCMOS technology. Key cryogenic measurements, including current gain (beta) and transconductance efficiency ( g(m) / I-c), are presented and discussed.

Large arrays of sensors operating at millikelvin temperatures are desirable for applications including X-ray satellites missions. Proposed designs for these arrays often rely on multiplexing methods, which read out many sensors while requiring less than one additional wire for every additional sensor. Here, we consider the possibility of nonmultiplexed readout of a 10 000-pixel sensor array, where each pixel has an individual DC superconducting quantum interference devices (SQUID) read out with an individual analog feedback circuit. We focus on the total power dissipation of a nonmultiplexed readout. We present an application-specific-integrated-circuit-compatible SQUID feedback circuit that meets the proposed noise and bandwidth requirements, dissipating only 10 mW per channel, or a total of 100 W for 10 000 channels. We show that total power consumption cannot be reduced by operating this circuit at the 75 K temperature stage of a cryostat. We predict the power load from 60 000 wires running to the base temperature of a cryostat, and show that with resistances compatible with the feedback circuit and feasible with current commercial capabilities, the power loads are below the cooling capacity of a cryostat proposed for an X-ray satellite mission.

Flux jumps occur in the readout electronics of Transition Edge Sensor (TES) detectors coupled to Superconducting Quantum Interference Devices (SQUIDs), as a consequence of the periodic transfer function of SQUIDs in the superconducting regime. These events manifest as discontinuities in the Time Ordered Data (TOD) and can significantly degrade the quality of the measured signals. In this work, we present an automated pipeline to identify and correct flux jumps in the calibration data of the QUBIC (Q & U Bolometric Interferometer for Cosmology) instrument, designed to measure the B-mode polarization of the Cosmic Microwave Background (CMB). Using data from multiple observation campaigns, we characterize the statistical properties of flux jumps and compare them with expectations based on the electronic configuration of the instrument. The proposed pipeline successfully corrects these events, allowing the recovery of affected data and enabling their use in subsequent CMB analysis.

The Athena mission entered a redefinition phase in July 2022, driven by the imperative to reduce the mission cost at completion for the European Space Agency below an acceptable target, while maintaining the flagship nature of its science return. This notably called for a complete redesign of the X-ray Integral Field Unit (X-IFU) cryogenic architecture towards a simpler active cooling chain. Passive cooling via successive radiative panels at spacecraft level is now used to provide a 50 K thermal environment to an X-IFU owned cryostat. 4.5 K cooling is achieved via a single remote active cryocooler unit, while a multi-stage Adiabatic Demagnetization Refrigerator ensures heat lift down to the 50 mK required by the detectors. Amidst these changes, the core concept of the readout chain remains robust, employing Transition Edge Sensor microcalorimeters and a SQUID-based Time-Division Multiplexing scheme. Noteworthy is the introduction of a slower pixel. This enables an increase in the multiplexing factor (from 34 to 48) without compromising the instrument energy resolution, hence keeping significant system margins to the new 4 eV resolution requirement. This allows reducing the number of channels by more than a factor two, and thus the resource demands on the system, while keeping a 4' field of view (compared to 5' before). In this article, we will give an overview of this new architecture, before detailing its anticipated performances. Finally, we will present the new X-IFU schedule, with its short term focus on demonstration activities towards a mission adoption in early 2027.

In the context of future ground-based or space-borne cryogenic instruments using transition-edge sensors (TES), the location of the front-end electronics (FEEs) is an important aspect of instrument design. The main functions of the FEE are to provide biasing currents for TES and superconducting quantum interference devices (SQUIDs) and to amplify the output signals of the SQUID arrays (the last SQUID stage). Room temperature FEE has several advantages compared to cryogenic FEE: more power available, characterized commercially available devices, easier to develop and test, etc. On the other hand, it usually means having a longer cryo-harness before large signal amplification and more complex cryostat interfaces to preserve small signal integrity. Moreover, it is generally assumed that cooling the readout improves the intrinsic noise in addition to avoid interference in the cryo-harness. In this paper, we present a conceptual design of an application-specific integrated circuit (ASIC) for TES front-end readout operating at cryogenic temperatures (50–70 K) using ST-130 nm technology. We discuss the necessary steps for the development of such ASICs. Indeed, another ASIC integrating elementary components has already been developed with this technology and has been tested at cryogenic temperatures. The measurements as function of temperature are useful to determine the correct operating points for low-temperature optimal performances of an FEE. Finally, the impacts of cryogenic operations on noise are discussed.

ATHENA will be ESA's next generation X-ray space observatory. The X-ray integrated field unit (X-IFU) instrument will be ATHENA's cryogenic spectro-imager. In this work, we present total ionizing dose (TID) tests performed on an application specific integrated circuit (ASIC) designed for X-IFU's warm front-end electronics (WFEE). In particular, space environment ionizing particles could cause an increase of flicker noise, affecting the performances of such a detection chain readout. We present low frequency noise measurements of the main components of the WFEE (low noise amplifier and slow current DAC) and the effect of total ionizing dose (TID). Five ASICs were irradiated up to 200 krad with a Co-60 source. We discuss the impact on the noise of such radiation effects beyond the life-time of a space mission as ATHENA.

The Line Emission Mapper (LEM) is a Probe mission concept developed in response to NASA's Astrophysics Probe Explorer (APEX) Announcement of Opportunity. LEM has a single science instrument composed of a large-area, wide-field X-ray optic and a microcalorimeter X-ray imaging spectrometer in the focal plane. LEM is optimized to observe low-surface-brightness diffuse X-ray emission over a 30' equivalent diameter field of view with 1.3 and 2.5 eV spectral resolution in the 0.2- 2.0 keV band. Our primary scientific objective is to map the thermal, kinetic, and elemental properties of the diffuse gas in the extended X-ray halos of galaxies, the outskirts of galaxy clusters, the filamentary structures between these clusters, the Milky Way star-formation regions, the Galactic halo, and supernova remnants in the Milky Way and Local Group. The combination of a wide-field optic with 18'' angular resolution end-to-end and a microcalorimeter array with 1.3 eV spectral resolution in a 5' x 5' inner array (2.5 eV outside of that) offers unprecedented sensitivity to extended low-surface-brightness X-ray emission. This allows us to study feedback processes, gas dynamics, and metal enrichment over seven orders of magnitude in spatial scales, from parsecs to tens of megaparsecs. LEM will spend approximately 11% of its five-year prime science mission performing an All-Sky Survey, the first all-sky X-ray survey at high spectral resolution. The remainder of the five-year science mission will be divided between directed science (30%) and competed General Observer science (70%). LEM and the NewAthena/XIFU are highly complementary, with LEM's optimization for soft X-rays, large FOV, 1.3 eV spectral resolution, and large grasp balancing the NewAthena/X-IFU's broadband sensitivity, large effective area, and unprecedented spectral resolving power at 6 keV. In this presentation, we will provide an overview of the mission architecture, the directed science driving the mission design, and the broad scope these capabilities offer to the entire astrophysics community.

The ATHENA space mission will be the next generation X-ray observatory. The X-ray integral field unit (X-IFU) is ATHENA's cryogenic spectro-imager, observing the sky with thousands of superconducting micro-calorimeters.(1) The detectors are based on transition edge sensors (TES) in time-division multiplexing (TDM). A warm front-end electronics (WFEE) demonstrator model (DM) has been developed for the low noise biasing and readout of X-IFU's cryogenic detection chain. After extensive testing, it has been delivered to the French space agency (CNES) for integration in the full detection chain DM. The WFEE DM is capable of reading out and biasing 8 TDM channels. Different configurations were chosen for some of the channels in order to find the best performance after testing of the whole demonstrator readout chain. Design and measured noise performances are discussed.

This paper gives a review of the ASIC design evolutions of the WFEE in the context of the ATHENA mission. The development follows the evolutions of the X-IFU instrument detection chain and secures the ASIC technology access continuity by using an ST SiGe 130 nm technology instead of the previous use of an AMS SiGe 350 nm node. First ASIC prototypes based on this ST 130 nm SiGe technology have been developed to answer these technical challenges and meet the new requirements. This paper will give a brief review of these ASICs dedicated to the WFEE.

Current cryogenic instruments require an increasingly high number of superconducting detectors. Large multiplexing factors are thus needed, increasing the bandwidth of the readout signals. In the specific case of transition edge sensors (TES), a cold amplification stage using superconducting quantum interference devices is usually coupled to a room temperature low-noise amplifier (LNA). A resistive harness up to a few meters long connects these two stages carrying signals with bandwidth of up to a few tens of MHz. In this context, it is reasonable to consider the possibility of impedance matching at the input of the LNA. In this paper, we present the impact of such impedance matching for the ATHENA X-IFU instrument, which uses TES in time-division multiplexing (Barret in Exp Astron 55:373–426 2023).

CNES (French Space Agency) is in charge of the development of the X-ray Integral Field Unit (X-IFU) instrument for Athena, the high resolution X-ray spectrometer of the ESA Athena X-ray Observatory. X-IFU will deliver spectra from 0.2 to 12 keV with a spectral resolution in the range of 2.5 eV up to 7 keV on a 5′′ pixels, with a field of view > 4′ equivalent diameter. The main sensor array detection chain is a key part of the instrument, being by far the main contributor to its performance. It involves major partners: NASA GFSC, NIST, SRON, VTT, APC, and IRAP. The cryo-harness interconnecting the Focal Plane Assembly cold interface to the Warm Front End Electronics is under CNES responsibility. The different technical solutions are the loom technology and the shielded twisted pair technology. Characterizations have been performed on breadboards to assess the crosstalk performances for each solution. The results of these analysis are a driver to perform the trade-off between the available cryo-harness technologies.

Antenna-coupled microwave kinetic inductance detectors are emerging as a compelling solution for the next generation of cosmic microwave background (CMB) experiments, which require focal plane arrays with a substantial increase in the number of detectors and multi-band observation capabilities. We present the design and fabrication of multichroic pixels using this architecture, optimized for B-mode polarization observation. The pixel incorporates an improved dual bowtie slot antenna placed at the second focus of an elliptical lens, covering an octave frequency range from 100 GHz to 300 GHz. We aim to achieve bandwidths exceeding 20% for two CMB-atmospheric transparent subbands at 150 GHz and 220 GHz while maintaining adequate linear polarization sensitivity with a cross-polarization level below -17 dB across the entire range. The captured signal is then passed through a superconducting microstrip low-pass filter to remove excessive colors before being fed into the diplexer, where the two bands are separated. These bands are then coupled to the inductive section of MKIDs, effectively modifying the resonant frequency and quality factor of the corresponding resonators. The demonstration sample is fabricated using five photomask layers, employing niobium and aluminum as the superconducting materials, and is currently undergoing testing.

The X-ray Integral Field Unit (X-IFU) is the high-resolution X-ray spectrometer to fly on board the Athena Space Observatory of the European Space Agency (ESA). It is being developed by an international Consortium led by France, involving twelve ESA member states, plus the United States. It is a cryogenic instrument, involving state of the art technology, such as micro-calorimeters, to be read out by low noise electronics. As the instrument was undergoing its system requirement review (in 2022), a life cycle assessment (LCA) was performed to estimate the environmental impacts associated with the development of the sub-systems that were under the responsibility of the X-IFU Consortium. The assessment included the supply, manufacturing and testing of sub systems, as well as involved logistics and manpower. We find that the most significant environmental impacts arise from testing activities, which is related to energy consumption in clean rooms, office work, which is related to energy consumption in office buildings, and instrument manufacturing, which is related to the use of mineral and metal resources. Furthermore, business travels is another area of concern, despite the policy to reduced flying adopted by the Consortium. As the instrument is now being redesigned to fit within the new boundaries set by ESA, the LCA will be updated, with a focus on the hot spots identified in the first iteration. The new configuration, consolidated in 2023, is significantly different from the previously studied version and is marked by an increase of the perimeter of responsibility for the Consortium. This will need to be folded in the updated LCA, keeping the ambition to reduce the environmental footprint of X-IFU, while complying with its stringent requirements in terms of performance and risk management.

Lens antenna-coupled detectors have emerged as a prominent technology for millimeter-wave astronomy over recent decades. The future ground-based cosmic microwave background (CMB) observations that target B-modes require the receiver to operate across multiple frequency bands while maintaining effective polarization selectivity. In this context, we have reconfigured the conventional broadband bowtie slot antenna into a dual-flare angle design, exclusively targeting the CMB emission wavelength at two bands centered at 150 GHz and 220 GHz. This antenna design facilitates partial independent tuning of resonant frequencies, leading to improved impedance-matching bandwidth,that achieves a return loss of ( S_11 < -10 dB) spanning over an octave from 100 to 300 GHz. Simultaneously, it maintains effective linear polarization sensitivity, with cross-polarization remaining below −15 dB at both sub-bands when coupled with a dielectric lens. The integration of on-chip band-pass filters enables the effective separation of antenna signals to microwave kinetic inductance detectors. This results in a compact, polarization-selective, multichroic pixel solution that perfectly aligns with the demands of CMB B-mode observation.

In the context of the ATHENA X-ray space mission,1 the X-ray Integral Field Unit's (X-IFU) Warm Front-End Electronics (WFEE) is a multichannel differential readout sub-system. As part of the verification of the performance several measurements are carried out, initially on the demonstrator model of X-IFU's WFEE, and later for the production models. The transfer function from the 8 channels included in a demonstrator are measured, for excitation from a few tens of Hz up to 50 MHz. Over the same frequency range, the inter-channel coupling and cross-talk are measured at a level below -80 dB. We can also measure the power supply rejection ratio. For these purposes, a lock-in amplifier is used in differential mode, especially to extract the small cross-talk signals which are at the same frequency as the input excitation. We discuss the design of the demonstrator model, mitigating cross-talk, and our measurement of the residual coupling between differential channels.

The X-ray Integral Field Unit (X-IFU) instrument is the high-resolution X-ray spectrometer of the ESA Athena X-ray Observatory. X-IFU will deliver spectra from 0.2 to 12 keV with a spectral resolution requirement of 4 eV (3 eV design goal) up to 7 keV from 5" pixels, with a hexagonal field of view of 4' equivalent diameter. The main sensor array and its associated detection chain is one of the major functional chains of the X-IFU instrument, and is the main contributor to X-IFU performance. CNES (Centre National d'Etudes Spatiales) is the prime contractor for the X-IFU and leads the project development and procurement aspects within the X-IFU Consortium; additional major partners of the main detection chain are NASA-GFSC, SRON, VTT, APC, NIST, IRAP, and IAP. The detection chain design for X-IFU has evolved in the past few years in order to secure the performances and development costs, in the frame of the New Athena mission. New TES pixels are implemented with slower time constant and a reduced sensitivity to magnetic field. The slower time constant directly allows an increase of the MUX factor and a reduction of the number of channels, together with the decrease of the number of proximity electronics boxes, or warm front end electronics (WFEE). The cryostat outer vessel temperature is now a 50 K thermal interface, cooled passively thanks to L-shaped thermal shield (L-grooves). This has a direct impact of the cryo-harness between the 4 K core interface and the WFEE interface. In the past years, we have performed early demonstration on the critical components in order to secure the detection chain design and performances. This paper presents the progress done on early demonstrations (warm electronics, cryo-harness breadboarding,...), while providing an update to the detection-chain design description.