10 research outputs found
A simulation suite for readout with SMuRF tone-tracking electronics
We present the details of a simulation suite for modeling the effects of
readout with SLAC Microresonator RF (SMuRF) electronics. The SMuRF electronics
are a warm readout and control system for use with superconducting microwave
resonator-based detector systems. The system has been used with the BICEP/Keck
program and will be used on the upcoming Simons Observatory and BICEP Array
experiments. This simulation suite is a software implementation of the main
SMuRF algorithms for offline analysis, modeling, and study. The
firmware-implemented algorithms for calibration, resonator frequency
estimation, and tone tracking present sources of potential bias or errors if
not modeled properly. The simulator takes as input true detector signal,
realistic resonator properties, and SMuRF-related user-controlled readout
settings. It returns the final flux ramp-demodulated output of a detector
timestream as would be passed to the experiment data acquisition system,
enabling the analysis of the impact of readout-related parameters on the final
science data. It is publicly available in Python with accompanying Jupyter
notebooks for user tutorials.Comment: 12 pages + references, 7 figures. Proceedings for SPIE Astronomical
Telescopes and Instrumentation 2022. Code at
https://github.com/cyndiayu/babysmur
The Simons Observatory: Characterizing the Large Aperture Telescope Receiver with Radio Holography
We present near-field radio holography measurements of the Simons Observatory
Large Aperture Telescope Receiver optics. These measurements demonstrate that
radio holography of complex millimeter-wave optical systems comprising
cryogenic lenses, filters, and feed horns can provide detailed characterization
of wave propagation before deployment. We used the measured amplitude and
phase, at 4K, of the receiver near-field beam pattern to predict two key
performance parameters: 1) the amount of scattered light that will spill past
the telescope to 300K and 2) the beam pattern expected from the receiver when
fielded on the telescope. These cryogenic measurements informed the removal of
a filter, which led to improved optical efficiency and reduced side-lobes at
the exit of the receiver. Holography measurements of this system suggest that
the spilled power past the telescope mirrors will be less than 1% and the main
beam with its near side-lobes are consistent with the nominal telescope design.
This is the first time such parameters have been confirmed in the lab prior to
deployment of a new receiver. This approach is broadly applicable to millimeter
and sub-millimeter instruments.Comment: in proces
Simons Observatory large aperture receiver simulation overview
The Simons Observatory (SO) will make precision temperature and polarization
measurements of the cosmic microwave background (CMB) using a series of
telescopes which will cover angular scales between one arcminute and tens of
degrees, contain over 60,000 detectors, and sample frequencies between 27 and
270 GHz. SO will consist of a six-meter-aperture telescope coupled to over
30,000 detectors along with an array of half-meter aperture refractive cameras,
which together couple to an additional 30,000+ detectors. SO will measure
fundamental cosmological parameters of our universe, find high redshift
clusters via the Sunyaev-Zeldovich effect, constrain properties of neutrinos,
and seek signatures of dark matter through gravitational lensing. In this paper
we will present results of the simulations of the SO large aperture telescope
receiver (LATR). We will show details of simulations performed to ensure the
structural integrity and thermal performance of our receiver, as well as will
present the results of finite element analyses (FEA) of designs for the
structural support system. Additionally, a full thermal model for the LATR will
be described. The model will be used to ensure we meet our design requirements.
Finally, we will present the results of FEA used to identify the primary
vibrational modes, and planned methods for suppressing these modes. Design
solutions to each of these problems that have been informed by simulation will
be presented.Comment: 14 pages, 10 figures, Proceedings of SPI
Simons Observatory Large Aperture Telescope Receiver Design Overview
International audienceThe Simons Observatory (SO) will make precision temperature and polarization measurements of the cosmic microwave background (CMB) using a series of telescopes which will cover angular scales between one arcminute and tens of degrees and sample frequencies between 27 and 270 GHz. Here we present the current design of the large aperture telescope receiver (LATR), a 2.4m diameter cryostat that will be mounted on the SO 6m telescope and will be the largest CMB receiver to date. The cryostat size was chosen to take advantage of the large focal plane area having high Strehl ratios, which is inherent to the Cross-Dragone telescope design. The LATR will be able to accommodate thirteen optics tubes, each having a 36 cm diameter aperture and illuminating several thousand transition-edge sensor (TES) bolometers. This set of equipment will provide an opportunity to make measurements with unparalleled sensitivity. However, the size and complexity of the LATR also pose numerous technical challenges. In the following paper, we present the design of the LATR and include how we address these challenges. The solutions we develop in the process of designing the LATR will be informative for the general CMB community, and for future CMB experiments like CMB-S4
Studies of systematic uncertainties for Simons Observatory: detector array effects
International audienceIn this proceeding, we present studies of instrumental systematic effects for the Simons Obsevatory (SO) that are associated with the detector system and its interaction with the full SO experimental systems. SO will measure the Cosmic Microwave Background (CMB) temperature and polarization anisotropies over a wide range of angular scales in six bands with bandcenters spanning from 27 GHz to 270 GHz. We explore effects including intensity-to-polarization leakage due to coupling optics, bolometer nonlinearity, uncalibrated gain variations of bolometers, and readout crosstalk. We model the level of signal contamination, discuss proposed mitigation schemes, and present instrument requirements to inform the design of SO and future CMB projects
The Simons Observatory: Design, integration, and testing of the small aperture telescopes
International audienceThe Simons Observatory (SO) is a cosmic microwave background (CMB) survey experiment that includes small-aperture telescopes (SATs) observing from an altitude of 5,200 m in the Atacama Desert in Chile. The SO SATs will cover six spectral bands between 27 and 280 GHz to search for primordial B-modes to a sensitivity of , with quantified systematic errors well below this value. Each SAT is a self-contained cryogenic telescope with a 35 field of view, 42 cm diameter optical aperture, 40 K half-wave plate, 1 K refractive optics, and TES detectors. We describe the nominal design of the SATs and present details about the integration and testing for one operating at 93 and 145 GHz
The Simons Observatory: Design, integration, and testing of the small aperture telescopes
International audienceThe Simons Observatory (SO) is a cosmic microwave background (CMB) survey experiment that includes small-aperture telescopes (SATs) observing from an altitude of 5,200 m in the Atacama Desert in Chile. The SO SATs will cover six spectral bands between 27 and 280 GHz to search for primordial B-modes to a sensitivity of , with quantified systematic errors well below this value. Each SAT is a self-contained cryogenic telescope with a 35 field of view, 42 cm diameter optical aperture, 40 K half-wave plate, 1 K refractive optics, and TES detectors. We describe the nominal design of the SATs and present details about the integration and testing for one operating at 93 and 145 GHz
The Simons Observatory: Instrument Overview
International audienceThe Simons Observatory (SO) will make precise temperature and polarization measurements of the cosmic microwave background (CMB) using a set of telescopes which will cover angular scales between 1 arcminute and tens of degrees, contain over 60,000 detectors, and observe at frequencies between 27 and 270 GHz. SO will consist of a 6 m aperture telescope coupled to over 30,000 transition-edge sensor bolometers along with three 42 cm aperture refractive telescopes, coupled to an additional 30,000+ detectors, all of which will be located in the Atacama Desert at an altitude of 5190 m. The powerful combination of large and small apertures in a CMB observatory will allow us to sample a wide range of angular scales over a common survey area. SO will measure fundamental cosmological parameters of our universe, constrain primordial fluctuations, find high redshift clusters via the Sunyaev-Zel`dovich effect, constrain properties of neutrinos, and trace the density and velocity of the matter in the universe over cosmic time. The complex set of technical and science requirements for this experiment has led to innovative instrumentation solutions which we will discuss. The large aperture telescope will couple to a cryogenic receiver that is 2.4 m in diameter and nearly 3 m long, creating a number of technical challenges. Concurrently, we are designing the array of cryogenic receivers housing the 42 cm aperture telescopes. We will discuss the sensor technology SO will use and we will give an overview of the drivers for and designs of the SO telescopes and receivers, with their cold optical components and detector arrays
Electrical characterization and tuning of the integrated POLARBEAR-2a focal plane and readout (Conference Presentation)
International audiencePOLARBEAR is a cosmic microwave background (CMB) polarization experiment located in the Atacama desert in Chile. The science goals of the POLARBEAR project are to do a deep search for CMB B-mode polarization created by inflationary gravitational waves, as well as characterize the CMB B-mode signal from gravitational lensing. POLARBEAR-1 started observations in 2012, and the POLARBEAR team has published a series of results from its first two seasons of observations, including the first measurement of a non-zero B-mode polarization angular power spectrum, measured at sub-degree scales where the dominant signal is gravitational lensing of the CMB. The Simons Array expands POLARBEAR to include an additional two telescopes with next-generation POLARBEAR-2 multi-chroic receivers, observing at 95, 150, 220, and 270 GHz.The POLARBEAR-2A focal plane has 7,588 transition-edge sensor bolometers, read out with frequency-division multiplexing, with 40 frequency channels within the readout bandwidth of 1.5 to 4.5 MHz. The frequency channels are defined by a low-loss lithographed aluminum spiral inductor and interdigitated capacitor in series with each bolometer, creating a resonant frequency for each channel's unique voltage bias and current readout. Characterization of the readout includes measuring resonant peak locations and heights and fitting to a circuit model both above and below the bolometer superconducting transition temperature. This information is used determine the optimal detector bias frequencies and characterize stray impedances which may affect bolometer operation and stability. The detector electrical characterization includes measurements of the transition properties by sweeping in temperature and in voltage bias, measurements of the bolometer saturation power, as well as measuring and removing any biases introduced by the readout circuit. We present results from the characterization, tuning, and operation of the fully integrated focal plane and readout for the first POLARBEAR-2 receiver, POLARBEAR-2A, during its pre-deployment integration run