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The 4m DAG telescope is under construction at East Anatolia Observatory in Turkey. DIRAC, the " DAG InfraRed Adaptive optics Camera", is one of the facility instruments. This paper describes the design of the camera to meet the performance specifications. Adaptive and auxiliary optics relay the telescope F/14 input 1:1 into DIRAC. The camera has an all refractive design for the wavelength range 0.9 - 2.4 micron. Lenses reimage the telescope focal plane 33 x 33 as (9 x 9 mm) on a 1k x 1k focal plane array. With magnification of 2x, the plate scale on the detector is 33 mas/pixel. There are 4 standard filters (Y, J, H, K) and 4 narrowband continuum filters. A 12 position filter wheel allows installation of 2 extra customer filters for specific needs; the filter wheel also deploys a pupil viewer lens. Optical tolerancing is carried out to deliver the required image quality at polychromatic Strehl ratio of 90% with focus compensator. This reveals some challenges in the precision assembly of optics for cryogenic environments. We require cells capable of maintaining precision alignment and keeping lenses stress free. The goal is achieved by a combination of flexures with special bonding epoxy matching closely the CTE of the lens cells and crystalline materials. The camera design is very compact with object to image distance

HgCdTe detectors with longer wavelength cutoffs were created for extending the lifetime of space-based applications because of their higher operating temperatures compared to arsenic doped silicon (Si:As) detectors. In addition to lower dark currents, the HgCdTe detectors also have higher quantum efficiencies compared to Si:As detectors. We are testing a HgCdTe detector with a 12.8 micron cutoff presented in Cabrera et al 2019 using HAWAII electronics in fast read-out mode to understand this array’s viability in instruments behind future ELT s that will directly image Earth-like planets. An f/100 system is required to operate the detector on a thirty meter diameter telescope without saturating, therefore we are the same f# system on the modified cryostat used to test and characterize the detector. We will present initial results on the detector’s quantum efficiency from 2 to 12 microns, read noise, dark current, and ability to tolerate flux levels that would be seen on future ELTs.

Superconducting qubits based on Josephson junctions are one of the leading candidates for building a largescale quantum information processor. There have been significant advances in the performance of superconducting qubits over the past decade and there is currently rapid progress in the development of systems with up to tens of qubits. In order to build to yet larger systems, new techniques will need to be developed to address the overhead requirements for room-temperature electronics hardware and cryostat wiring for controlling and reading out large numbers of qubits. One approach to this challenge involves implementing more of the qubit control and readout in the low-temperature environment. I will describe our efforts on integrating superconducting classical digital circuitry with superconducting qubits for coherent control and readout.

With its first flight in 2018, Micro-X became the first program to fly Transition-Edge Sensors and their SQUID readouts in space. The science goal was a high-resolution, spatially resolved X-ray spectrum of the Cassiopeia A Supernova Remnant. While a rocket pointing error led to no time on target, the data was used to demonstrate the flight performance of the instrument. The detectors observed X-rays from the on-board calibration source, but a susceptibility to external magnetic fields limited their livetime. Accounting for this, no change was observed in detector response between ground operation and flight operation. This paper provides an overview of the first flight performance and focuses on the upgrades made in preparation for reflight. The largest changes have been upgrading the SQUIDs to mitigate magnetic susceptibility, synchronizing the clocks on the digital electronics to minimize beat frequencies, and replacing the mounts between the cryostat and the rocket skin to improve mechanical integrity. As the first flight performance was consistent with performance on the ground, reaching the instrument goals in the laboratory is considered a strong predictor of future flight performance.

The B-BOP instrument for the SPICA mission will use a brand new generation of submillimeter bolometers. An ultra-low background testbed for these bolometers has been developed for phase A of ESA. Inside the test cryostat lies a submillimeter light source designed to emit different flux, each of them with the same spectrum, at high temperature. To make sure the light arriving on the bolometers is faint, we use an inversed telescope to dilute the light. This allowed us to perform the first measurements on bolometer arrays produced by CEA-Leti.

We have developed a prototype half-wave plate (HWP) based polarization modulator (PMU) for Cosmic Microwave Background polarization measurement experiments. We built a 1/10 scaled PMU that consists of a 50 mm diameter five-layer achromatic HWP with a moth-eye broadband anti-reflection sub-wavelength structure mounted on a superconducting magnetic bearing. The entire system has cooled below 20 K in a cryostat chamber that has two millimeter-wave transparent windows. A coherent source and the diode detector are placed outside of the cryostat and the millimeter-wave goes through the PMU in the cryostat. We have measured the modulated signal by the PMU, analyzed the spectral signatures, and extracted the modulation efficiency over the frequency coverage of 34-161 GHz. We identified the peaks in the optical data, which are synchronous to the rotational frequency. We also identified the peaks that are originated from the resonance frequency of the levitating system. We also recovered the modulation efficiency as a function of the incident electromagnetic frequency and the data agrees to the predicted curves within uncertainties of the input parameters, i.e. the indices of refraction, thickness, and angle alignment. Finally, we discuss the implication of the results when this is applied to the LiteBIRD low-frequency telescope.

The ASTEROID project is a H2020-COMPET EU project whose main goal is to provide Europe with the capability to manufacture high performance infrared focal plane arrays (FPA) devoted to scientific and astronomical space and ground telescope missions. The european consortium is composed by key research institutions (CEA-Leti, CEA-Saclay and IFAE) and industrial partners (Lynred, EVG and ADDL) being the resulting detector a SWIR hybridized MCT (mercury-cadmium-telluride) FPA of 2k x 2k pixels and 15 μm of pixel pitch. The project also looks for the validation of a thermo-mechanical model for large FPAs by reducing the stress build up in the ROIC and wafer bonded structures, both resulting in better detector reliability. On this framework, a cryo-vacuum system has been developed at the IFAE mechanical workshop with capabilities to perform low temperature thermal cycles in the MCT detector range and up to ~50K. The large volume cryostat (~120 liters) is cooled by a helium compressor and a single stage cold head, hosting the detector and its preamplification stage to provide a suitable light path and radiation shield for thermal background control. Most of the inner light path parts has been developed using off-the-shelf optomechanical components which allow us to modify the incoming light performance with standard 1 or 2-inches optical components. The cryostat design, configuration and the whole system performance will be reported on this paper with the aim to test the hybridized FPA to assess the reliability at operating temperature after several thermal cycles..

International audience; We present a new development for the measurement of the Quantum Efficiency (QE) of a Mercury Cadmium Telluride (HgCdTe or MCT) detector array in the long wave infrared (LWIR) spectral band. To measure the incident photon flux on the detector, CEA-LETI has designed and produced a calibrated MCT photodiode which, under the test setup conditions used for the QE measurement, delivers a total (dark plus photonic) current of 1nA at 60K. The readout of such a low level of current makes a standard room temperature amplifier inconvenient due to the length of the wires between the focal plane (FP) at cold and the outside of the cryostat (>2m in the current cryostat). A much better approach is to use High Electron Mobility Transistors (Cryo-HEMTs), optimized by CNRS/C2N laboratory for ultra-low noise at very low temperatures (

CYRA (CrYogenic solar spectrogRAph) is a facility instrument of the 1.6-meter Goode Solar Telescope (GST) at the Big Bear Solar Observatory (BBSO). CYRA focuses on the study of the near-infrared solar spectrum between 1 and 5 microns, a under explored region which is not only a fertile ground for photospheric magnetic diagnostics, but also allows a unique window into the chromosphere lying atop the photosphere. CYRA is the first ever fully cryogenic spectrograph in any solar observatory with its two predecessors, on the McMath-Pierce and Mees Telescopes, being based on warm optics except for the detectors and order sorting filters. CYRA is used to probe magnetic fields in various solar features and the quiet photosphere. CYRA measurements will allow new and better 3D extrapolations of the solar magnetic field and will provide more accurate boundary conditions for solar activity models. Superior spectral resolution of 150,000 and better allows enhanced observations of the chromosphere in the carbon monoxide (CO) spectral bands and will yield a better understanding of energy transport in the solar atmosphere. CYRA is divided into two optical sub-systems: The Fore-Optics Module and the Spectrograph. The Spectrograph is the heart of the instrument and contains the IR detector, grating, slits, filters, and imaging optics all in a cryogenically cooled Dewar (cryostat). The detector a 2048 by 2048 pixel HAWAII 2 array produced by Teledyne Scientific & Imaging, LLC. The interior of the cryostat and the readout electronics are maintained at 90 Kelvin by helium refrigerant based cryo-coolers, while the IR array is cooled to 30 Kelvin. The Fore-Optics Module de-rotates and stabilizes the solar image, provides scanning capabilities, and transfers the GST image to the Spectrograph. CYRA has been installed and is undergoing its commissioning phase., 11 pages, 9 figures, 2 tables. Prepared for SPIE conference proceedings

A compact front-end system is presented for a dual-linear polarization cryogenic Q-band receiver. This receiver will be used to demonstrate the high frequency performance of the Dish Verification Antenna 2 (DVA-2) composite reflector telescope between 35–50 GHz and is a technology demonstrator with possible application to the National Radio Astronomy Observatory’s Next Generation Very Large Array (ngVLA). A vacuum vessel and a two-stage Gifford-McMahon cryopump system are used for the cryogenic environment. The second stage of the cryostat is cooled to 16 K and includes a small choke ring feed horn, a low-loss noise calibration module (NCM) integrated with orthogonal mode transducer (OMT), and two cryogenically cooled mHEMT MMIC low-noise amplifiers (LNAs). Using a noise diode as the noise source on the 300 K stage inside the cryostat helps to protect the cooled components from signals outside of the cryostat, and also lessen the heat on the second stage since a noise diode normally produce a power dissipation of several hundred mW. The OMT design is an optimized version of the design used in the ALMA Band 1 cartridge with two integrated directional couplers and excellent performance. The cascaded noise analysis of the receiver shows a receiver noise temperature of 19.4 K.

The ngVLA Front End concept has six separate cryogenically-cooled, dual polarization receiver bands, each with an integral feed horn. The upper five bands (2–5) are co-located within a single compact cryostat, while the lowestfrequency band (1) occupies a second cryostat of similar volume and mass. For optimum performance at higher frequencies, waveguide-bandwidth (~1.66:1) receivers are used above 12 GHz, with axially-corrugated feed horns for high aperture efficiency and low spillover. Below 12 GHz, wideband (~3.5:1) receivers and feed horns are used to reduce receiver count, total mass, and cost, with modest trades in sensitivity. Ongoing work includes development of wideband feed horns, windows, low-noise amplifiers (LNAs) and couplers for Bands 1–2, design or procurement of orthomode transducers (OMTs) and LNAs for Bands 3–6, and detailed mechanical design of the conceptual Front End cryostats and receiver/feed/window subassemblies. Accurate simulations of sensitivity (AEFF/TSYS) versus frequency and antenna elevation will be shown, based on modeled or measured component data and the simulated performance of the antenna optics.

The X-ray Integral Field Unit (X-IFU) of the ATHENA space observatory is based on a 3 kilo-pixels array of superconducting micro-calorimeters, that is read out with the Warm Front-End Electronics (WFEE) and then followed by the Digital Readout Electronics (DRE) outside the cryostat. We have developed low-noise/lowdrift amplifiers for this readout as well as performed simulations and measured the noise, bandwidth, linearity, harmonic distortion and thermal drift. Here we are presenting a realistic model of these parameters. These characterizations and models of the WFEE are necessary in order to get a full ATHENA X-IFU readout chain simulator. Impact of the WFEE low-frequency noise and its limited bandwidth on the entire X-IFU detection chain in Time Domain Multiplexing will be introduced.

The Support Structure for the Thirty Meter Telescope (TMT) Infrared Imaging Spectrograph (IRIS) consists of 18 carbonfiber reinforced polymer (CFRP) struts, a CFRP ring and a metal interface frame. This ultra-stiff, lightweight structure suspends the five-ton IRIS Science Cryostat and Rotator below the Narrow Field Infrared Adaptive Optics System (NFIRAOS). Through comprehensive design and analysis driven by requirements for stiffness, optical alignment, adjustability, manufacturability, weight and space, much headway was made to bring this design to fruition. This work presents the current state of design, including material down-selection, adjuster design and strategies for fabrication, alignment and testing. It summarizes methodologies and simulation results examining stiffness, seismic and thermal loads and transmission of vibration between NFIRAOS and IRIS. A prototype strut is being developed and will undergo dynamic mechanical testing to characterize its performance.

Since the start of full science operations from 2004, the Submillimeter Array has been implementing plans to expand IF bandwidths and upgrade receivers and cryostats. Metal mesh low-pass filters were designed to block infrared (IR) radiation to reduce the thermal load on the cryostats. Filters were fabricated on a quartz wafer through photolithography and coated with anti-reflection (AR) material. The filters were tested from 200 to 400 GHz to verify their passband performances. The measurement results were found to be in good agreement with EM simulation results. They were tested in the far-infrared (FIR) frequency range to verify out-of-band rejection. The IR reflectivity was found to be approximately 70%, which corresponded to the percentage of the area blocked by metal., 9pages, 14 figures

VIRUS2 is a new NSF-funded facility instrument on the McDonald Observatory Harlan J Smith 2.7m Telescope. The instrument is a fiber-fed multiplexed integral field spectrograph consisting of 6 units, each with 4 spectral channels, to provide large on-sky area coverage coupled with broad spectral coverage. A novel beam switch module is implemented in the fiber feed which separates light into the pass bands of the four spectral channels. This paper details the mechanical design of the spectrograph, cryostat, and the beam switch module. A unique method for precise six degree of freedom positioning of the CCD detectors is presented, along with process for determination of required adjustments. Results from prototype testing and first article production is included.

We present the optomechanical design of the Potsdam Arrayed Waveguide Spectrograph (PAWS), which is the first on-sky demonstrator of an integrated photonic spectrograph specifically designed and optimized for astronomy. The instrument is based on an arrayed waveguide grating (AWG) that was designed by and custom fabricated for the innovation center innoFSPEC Potsdam. The commissioning of the instrument is planned at the Calar Alto 2:2m Telescope in southern Spain. The core of the instrument is the AWG-chip as the primary dispersive element. The AWG device is coupled to the telescope module via a single-mode fibre (SMF). The spectral image on the output facet of the AWG is a superposition of multiple spectral orders due to the cyclic dispersive behavior of the waveguide array. The output of the AWG is fed into a free-space optical system housed inside a cryostat via an infinity-corrected microscope objective. The overlapping spectral orders are separated by a second dispersion stage using a ruled grating as a cross-dispersive element, and the resulting echellogram is projected onto a Teledyne 2k x 2k H2RG near-infrared array. The requirement of sub-micron accuracy of the fibre-chip alignment has led to an advanced photonic packaging method. In order to avoid on-site alignment procedures during the on-sky testing, the AWG mount, fibre-support, and microscope objective were integrated into a single monolithic module. Optical and thermal simulations and the design of the cryostat were realized by Andes Scientific. The read-out electronics and the compatible operating software for the detector was provided by the Max Planck Institute for Astronomy (MPIA). Data analysis is performed using the open-source data reduction software P3D, which provides functionality for the removal of the instrument signature, extraction of the spectra, correction for the blaze function, wavelength calibration, and processed data file export.

In this paper we discuss the mechanical design of the GIRMOS Cryostat. GIRMOS is an adaptive optics fed multi-object Integral-Field Spectrograph with a parallel imaging capability and will be installed at the Gemini North Observatory. This instrument includes four separate identical spectrograph channels arranged symmetrically around the central axis of the instrument which provide it its multiplexing capability. Each spectrograph channel starts off at the object selection mechanism. The object selection mechanism contains four motorized fold mirror assemblies which scan the incoming light from the telescope to look at four separate objects simultaneously or combine their efforts to look at a single object in a tiled mode. Each of the four individual beams from the object selection system are then directed into the instrument dewar via separate entrance windows. Within the dewar each IFS beam moves through an anamorphic relay, an optical image slicer assembly and eventually makes it to a Spectrograph unit. All of these assemblies are located on a single cold bench within the dewar. The instrument imager is located along the central axis of the dewar and is housed in the cold bench as well. In this paper we will provide some details regarding the Cryostat design, the mechanical packaging of the IFS and imager along with some of the thermal load mitigation techniques employed. We will also discuss some key performance requirements that were expected from the Cryostat and the design choices we made in order to achieve them.

We present the current design status of the cryostat of the Mid-infrared ELT Imager and Spectrograph (METIS) instrument to be operated at ESO’s Extremely Large Telescope (ELT). The cryostat provides the cold optics of the instrument with the required cryo-vacuum environment. The radiation shields of the cryostat are cooled with liquid nitrogen and the cold optics is cooled via pulse-tube coolers down to temperatures around 35 K. The cold-warm interface is provided with G10 blades that build together with the top part of the cryostat vessel the structural interface to the cold optics, the warm support structure and the warm calibration source. The cryostat development is currently in its final design phase which is planned to conclude in summer 2022. We present in this paper the current design status, the key design considerations and the cooling concept.

We present an update of the design of the Central Wheel Mechanism (CWM), a subsystem of the MICADO instrument for the Extremely Large Telescope (ELT)1. The CWM consists of a Filter Wheel Mechanism (FWM) with two Filter wheels, the Pupil Wheel Mechanism (PWM) with one Pupil wheel and the Atmospheric Distortion Corrector (ADC). The CWM has a diameter of about 1.5 meter. Challenges in the mechanical design work are focused on fitting all the components in the available design volume and ensuring that the accuracy and repeatability requirements are met. The mechanisms should work in a cryogenic environment for an intended lifetime of 10 years and survive transport and seismic conditions. Additionally the system has to cool and warm-up properly. The most noticeable update since the PDR2 is a self-contained ring assembly of a connected FWM and PWM that is suspended to the MICADO instrument using flexible supports. The arrangement of these supports creates a point of shrinkage at the optical position which is off-axis from the cryostat center. An alignment tool will guarantee a position accuracy within 50 μm for both the ADC as well as the Pupil masks that are mounted after the system is integrated into the instrument. The most sensitive bearings are protected from shock loads by a system that limits their load carrying capability by transferring the excess load to bumpers. These bumpers do not affect the repeatability of the system.

The HIgh-Resolution Mid-infrarEd Spectrometer (HIRMES) is the 3rd Generation Instrument for the Stratospheric Observatory For Infrared Astronomy (SOFIA). The HIRMES cryostat is comprised of several cooling stages (300K, 65K, 4K, 800mK, 400mK, and 70mK), which are essential to achieve the required sensitivity on the mid-infrared waveband in which HIRMES observes (25 um-122um). The science application of the HIRMES instrument is the study of proto-planetary systems that contain water-vapor, water-ice, deuterated hydrogen, and neutral oxygen. In this paper, we discuss the use of a He3 stage coupled to an Adiabatic Demagnetization Refrigerator (ADR) stage in order to achieve the required temperature of 70mK on the Focal Plane Assembly (FPA). HIRMES' FPA contains two Transitioning Edge Sensor (TES) bolometric detector arrays that can provide a combination of four primary observing modes; High Resolution (R ~ 100,000), Mid-Resolution (R ~ 10,000), Low-Resolution (R ~ 600) spectroscopy, and Spectral Imaging (R ~ 2000).1 Moreover, we discuss the operations of the detector readout, in combination of a grating-dispersive spectroscopy mechanism, and a host of Fabry-Perot tunable narrow-band filters to achieve HIRMES' unmatched sensitivity in all four modes.

For miniaturized optical fiber coupled MOEMS systems, fiber coupling on chip level is necessary. Therefore a silicon chip based optical fiber coupling with high position accuracy is introduced. In this paper, we present the fiber chip coupling on two examples: A superconducting single photon detector (SSPD) and a miniaturized fiber Bragg grating sensor. In case of the SSPD position accuracy between SSPD and optical fiber of ± 1 μm is necessary. In this paper we show the developed alignment system and the proof of the position accuracy on silicon test chips. Further, we show first experiments of a fiber coupled superconducting test structure in a closed cycle cryostat with regard to stability of the chip stack and thermal connectivity to the cryostat. The fiber coupling of the fiber Bragg grating sensor is used to miniaturize the sensor overall construction. The fiber Bragg sensor consists of two stacked Silicon photodiodes. The top photodiode is fabricated in a cavity within a remaining 50 μm Silicon membrane and therefore detects only the shorter wavelength range. The bottom photodiode detects the transmitted longer wavelengths. The fiber coupling chip is mounted on top of the photodiode stack. This leads to a compact chip stack with included fiber coupling, without the need for large fiber connectors or ferrule holders. Further, we demonstrate the mounting of the fiber Bragg sensor on a flexible PCB and its performance.

The Leonardo SAPHIRA is a HgCdTe linear avalanche photodiode array enabling high frame rate, high sensitivity, low noise, and low dark current imaging at near-infrared wavelengths. The ANU utilised the Leonardo SAPHIRA to develop a high cadence “Lucky Imager” which was successfully tested on sky at Siding Spring Observatory. The cryogenic electronics and cryostat were designed and built by the ANU. The cryostat was cooled with a compact Stirling cycle cryocooler with active vibration damping. Various detector control systems were tested, including an ESO 'NGC' system and also a 32 channel ARC SDSU Series III. Images were ultimately captured at a windowed frame rate of 2.2 kHz with the ESO NGC controller.

TolTEC is an imaging polarimeter that will be mounted on the 50m diameter Large Millimeter Telescope (LMT) in Mexico. This camera simultaneously images the focal plane at three wavebands centered at 1.1, 1.4, and 2.0mm. TolTEC combines polarization-sensitive Kinetic Inductance Detectors (KIDs) with the LMT to produce 5-10 arcmin resolution maps of the sky in both total intensity and polarization. The light from the telescope is coupled to the TolTEC instrument using three room temperature mirrors. Before entering the cryostat, the light passes through a rapid-spinning achromatic half-wave plate, and once inside it passes through a 1 K Lyot stop that controls the telescope illumination. Inside the cryostat, a series of aluminum mirrors, silicon lenses, and dichroic filters split the light into three wavelength bands and direct each band to a different detector array. We will describe the design, and performance of the optics before installation at the telescope.

The COMPASS-U tokamak (Bt = 5 T, Ip = 2 MA, R = 0.894 m, a = 0.27 m) is currently under design at IPP CAS (Institute of Plasma Physics of the Czech Academy of Sciences). One of the design challenges is to design sufficiently strong foundations to support even the highest forces that are generated during plasma disruption events. The worst, found up to now, scenario has been considered in order to simulate the response of the main tokamak components and to calculate the force transmitted to the foundations. A 3D model has been built in the ANSYS Workbench software including the cryostat support, the vacuum vessel, the poloidal field coils and their supports. The forces have been calculated via global electromagnetic model. Integrated values of the forces and torques have been spread onto surfaces of the parts. The modal superposition method has been utilized for the integration, based on the first 100 vibration modes. Rayleigh damping model with the fraction of critical damping of 2% was used. The reaction forces transmitted to the foundations have been obtained providing input for the civil design work.

The Double Quarter Wave (DQW) Crab Cavity was designed to rotate the colliding bunches and in consequence to increase the luminosity of the LHC machine. Prior to launching series production detailed RF validation tests, both without and with beam, were performed at CERN. For the cavity preparation and RF performance validation before installation in the cryomodule, a comprehensive programme of RF surface preparation and cavity performance evaluation in liquid helium temperatures were carried out. Due to the unusual geometry of the DQW cavity there were a number of challenges both in preparation and RF testing that had to be addressed. The results and conclusions of the preparation process and cavity performance in the vertical test cryostat are presented in this paper in the form of a short technical report.

A 11.5 J at 40 ns output has been obtained from a diode-pumped cryo-cooled Yb:YAG ceramics active-mirror laser amplifier system. The system consists of two amplifier heads which has four Yb:YAG ceramic disks and two pump LD modules. The Yb:YAG ceramics are cooled by conventional cryostat from rear side and are pumped by LD modules from front-side. A pump pulse is delivered to Yb:YAG ceramics coaxially with a seed pulse to reduce damage risk at a dielectric coating of Yb:YAG ceramics due to simplified coating design. To realize this system design, a LD module has been developed to keep a rectangle pattern with side length of around 37 mm among imaging depth of about 10cm at working distance of about 410 mm. As an experimental result of two pass amplification, a 11.5 J pulse energy was obtained with input energy of 1.0 J and total pump energy of 90.2 J. Then, an optical-to-optical conversion efficiency was 11.6% and an extraction efficiency was estimated to be 42%. In our knowledge, this is the highest output energy with nano second pulse duration in cryo-cooled Yb:YAG active-mirror laser amplification scheme. A repetition rate of 0.05 Hz depends on a limitation of a repetition rate of the seed pulse. A dependence of small-signal-gain on pumping repetition rate of the active-mirror laser head was experimentally evaluated. From the experimental result, we have estimated a feasible repetition rate of over 5 Hz. A 10 Hz operation will be demonstrated to reduce a thermal resistance between Yb:YAG ceramics and cryostat. Finally, this laser amplifier system is installed to a 100-J class laser system as preamplifier.

MICADO will equip the ELT with a first light capability for diffraction limited imaging at near-infrared wavelengths. The instrument's observing modes focus on various flavours of imaging, including astrometric, high contrast, and time resolved. There is also a single object spectroscopic mode optimised for wavelength coverage at moderately high resolution.(1) Due to ESO's technology standards evolution from VLT to ELT, MICADO will manifest the combined, PLC based soft- and hardware control. The evolution of ESO's technology design guidelines is on the one hand triggered by the ongoing developments in modern days industry and consumer technology. On the other hand, ELT's sheer dimensions request increasingly complex and smart solutions onwards controlling and monitoring such huge instruments. ESO's control concept is based on a two layer approach: PLCs are responsible for low-level hardware control (in a real-time fashion, if necessary), while software running on a Linux workstation implements the astronomic business logic of the control system. Development is eased by the fact that ESO delivers libraries for the control of many standard hardware components. A very interesting feature of this approach is the possibility to run C++ code natively inside a PLC real-time environment. This will be used for the control of complex mechanisms like the MICADO Atmoshperic Dispersion Corrector (ADC). This contribution provides an overview of the key functionality of the instrument focusing on the mechanisms inside the cryostat, and an overview of the cryogenic control. Because of hardware and cryogenic safety reasons, the cryostat control PLC system will be designed as a closed PLC based control system. Hence commands will only be accepted from a human machine interface located next to the cryostat itself. All cryostat parameters and according sensor readings will be published via OpcUA, allowing for full remote cryostat monitoring. In contrast, the instrument control PLC system will interact with the higher level software using the advantages of the industrial OpcUA communication standard and will therefore allow for remote control. Further configuration and commissioning of those mechanisms is made conveniently accessible via this approach. All this is based on ESO's concept for Line replaceable Units (LRU), which utilizes Beckhoff PLC units to ensure maintainability, availability.

The InfraRed Imaging Spectrograph (IRIS) is a first-light instrument for the Thirty Meter Telescope (TMT). It combines a diffraction limited imager and an integral field spectrograph. This paper focuses on the electrical system of IRIS. With an instrument of the size and complexity of IRIS we face several electrical challenges. Many of the major controllers must be located directly on the cryostat to reduce cable lengths, and others require multiple bulkheads and must pass through a large cable wrap. Cooling and vibration due to the rotation of the instrument are also major challenges. We will present our selection of cables and connectors for both room temperature and cryogenic environments, packaging in the various cabinets and enclosures, and techniques for complex bulkheads including for large detectors at the cryostat wall., Ground-based and Airborne Instrumentation for Astronomy VII, June 10-15, 2018, Austin, United States, Series: Proceedings of SPIE; no. 10702

Over half of the light incident on the Earth from the Universe falls within the Far-Infrared (FIR) region of the spectrum. Due to the deleterious effects of the Earth's atmosphere and instrument self-emission, astronomical measurements in the FIR require space-borne instrumentation operating at cryogenic temperatures. These instruments place stringent constraints on the mechanical and thermal properties of the support structures at low temperatures. With high stiffness, tensile strength, strength-to-mass ratio, and extremely low thermal conductivity, carbon fibre reinforced polymers (CFRPs) are an important material for aerospace and FIR astronomical applications, however, little is known about their properties at cryogenic temperatures. We have developed a test facility for exploring CFRP properties down to 4 K. We present results from our ongoing study in which we compare and contrast the performance of CFRP samples using different materials, and multiple layup configurations. Current results include an evaluation of a cryostat dedicated for materials testing and a custom cryogenic metrology system, and preliminary cryogenic thermal expansion measurements. The goal of this research is to explore the feasibility of making CFRP-based, lightweight, cryogenic astronomical instruments.

The Prime Focus Spectrograph (PFS) of the Subaru Measurement of Images and Redshifts (SuMIRe) project for Subaru telescope includes four identical spectrograph modules fed by 600 fibers each. This paper presents the integration, alignment and test procedures for the first spectrograph module composed by an optical entrance unit that creates a collimated beam and distributes the light to three channels, two visible and one near infrared. In particular, we present the performance of the single Red channel module. Firstly, we report on the measured optical performance: optical quality and ghost analysis. We also report on the thermal performance of the visible camera cryostat. Finally, we describe the software used to control and monitor the instrument.

MICADO, the Multi AO Imaging Camera for Deep Observations, is one of the first light instruments for the ELT, currently under construction by the European Southern Observatory (ESO) on Cerro Armazones in Chile. It is built by a huge consortium with partners from the Netherlands, Austria, France, Italy, Finland and Germany under the lead of the Max-Planck-Institute for extraterrestrial Physics in Garching. The instrument will operate in the NIR wavelength range, thus is developed as a cryogenic instrument to work under vacuum conditions. It can be used as an imaging camera in a high and low resolution mode, a spectrometer and also as a coronagraph. For calibration purposes a so called ”pupil imager” mode will also be implemented. To switch between the operational modes MICADO will use the MSM to insert different optical modules to the fixed components of the High Resolution Imager (HRI) inside the cryostat. All moving parts have to operate under vacuum and at cryogenic temperatures. The MSM consists of a rotating platform, where the optical modules are mounted on. To lower the friction inside the mechanism we decided to use several small bearings to support the platform instead of a central big one. The small bearings are placed in a way, that the movement of the platform is limited to a rotation. Some of the bearings will be preloaded by springs to take also CTE differences or temperature gradients during the cool down and warm up phases into account. The mechanism will be driven by a cryogenic Phytron stepper motor with an integrated planetary gear box. Switches will be used to limit the rotation of the platform to the necessary range. Because of the challenging requirements on repositioning of the optical modules inside the science beam, we will use an indent mechanism. We are still investigating if the indent mechanism has to be actively driven or can be implemented as a passive version. The necessary optics to switch between the operational modes are designed as individual pre-aligned modules, each with a defined mechanical and thermal interface to the rotating platform. The Low Resolution Imager (LRI) consists of two flat mirrors, blocking some of the fixed components of the HRI. The spectrometer will use two reflective gratings, one acting as the main and one as a cross disperser. The cross disperser separates the overlaying orders on the focal plane array. The pupil viewer consists like the LRI module of two flat mirrors and an additional lens imaging the pupil to the focal plane. In this paper we will present the current mechanical design and first results of the structural and thermal FEM analyses we performed. We will also highlight first ideas on integration and alignment. A second paper (A. Monna et al., same proceedings) concentrates on the cryogenic setups we perform inside a cryostat to proof proper functionality of the chosen components and designs.

We present the new LN2 continuous- ow test cryostat of the Universitats-Sternwarte Munchen, procured within the context of the Multi-Adaptive Optics Imaging Camera for Deep Observations (MICADO) for the Extremely Large Telescope. The cryostat will be used to perform tests of mechanical, optical and electronic components at high vacuum condition and cryogenic temperature, for the development of the cryogenic Main Selection Mechanism of the MICADO instrument. In this paper we give an overview of the cryostat design and we report about the temperature stability the cryostat can achieve, as well as the temperature gradient over its cold plate. We also report about the impact of adding extra loads on the system after integrating a cold curved shutter in the cryostat and on characterizing the thermal coupling of cryogenic assemblies.

We present the preliminary design of the calibration unit of the future E-ELT instrument METIS. This independent subunit is mounted externally to the main cryostat of METIS and will function both as calibration reference for science observations, as well as verification and alignment tool during the AIT phase. In this paper, we focus on describing its preliminary layout and foreseen functionalities, based on the performance requirements defined at system level and the constraints imposed by warm IR background. We discuss the advantage of employing an integrating sphere as common radiation emitter, leading to a novel and versatile design, where the source's spatio-spectral properties can be varied with high fidelity and repeatability. By combining only few tuneable sources and mechanisms we show how a large instrument such as METIS can be calibrated and tested, without the need of a complex cold calibration unit.

The X-ray Integral Field Unit (X-IFU) is an imaging microcalorimeter being developed for ESA's Athena X-ray observatory to providing high spectral resolution imaging between 0.2-12 keV, with moderate count-rate capability and a large field-of-view. The X-IFU focal plane assembly (FPA) will contain the instrument's large-format transition edge sensor (TES) microcalorimeter array and its superconducting readout electronics, plus a second TES detector, located behind the main sensor array, is used to detect high-energy cosmic rays and secondary particles passing through the sensor array and enable the rejection of false events that they generate in the sensor array's event list. A Kevlar thermal suspension is used to isolate the detectors at 55 mK from the 2 K environment of the X-IFU instrument cryostat's cold stage, while three layers of shielding are used to allow the detector's to achieve their low-noise performance in the expected on-ground and in-flight electromagnetic and microvibration environment. This paper will describe the preliminary design concept of the X-IFU focal plane assembly and its critical technology building blocks.

HARMONI is a visible and near-infrared (0.47 to 2.45 μm) integral field spectrograph, providing the ELT's core spectroscopic capability at first light. A pre-optics subsystem provides four selectable spatial pixel scales, in addition to other beam conditioning functions such as shutter and pupil masks. For the validation of the mechanisms in charge of these functions (fast shutter and the plane mask wheel) we have planned some prototypes to test the design solutions. The focal plane mask wheel sits in the input focus of the cryostat. It provides 16 user-selectable positions for masks (28x40 mm) used in observation. The key driver for this mechanism is the high repeatability (±2.5 μm) required, equivalent to ∼1mas in the input focal plane. The IAC has previously designed, manufactured, tested and put in operation cryogenic wheels with high repeatability; however, the challenge of obtaining a wheel with such repeatability requires testing new concepts of detent positioning systems. The shutter allows for exposures shorter than the minimum read time of the near-IR detectors and is needed for any CCD observations with the visible cameras. A dual shutter design is needed to achieve the necessary open/close times (

Zwicky Transient Facility is an integrated, multi-band astronomical survey system optimized for sensitivity, observing cadence, and efficiency. The key subsystem consists of a 600 megapixel CCD focal plane mounted in a flat-fielding vacuum cryostat, located at the prime focus of the 1.2-meter Samuel Oschin Telescope at Palomar Observatory. Supporting subsystems include a new 2.4-meter optical shutter assembly, a 1.35-meter diameter aspheric corrector plate, a cryostat stabilizing hexapod, a commercial robotic arm-based exchanger, three 440 millimeter width filters, four guide/focus CCDs, and dedicated optics compensating individual field curvature over each of sixteen 6k x 6k science CCDs.To optimize ZTF efficiency, all telescope and dome drives were upgraded for higher speed and acceleration, fast readout electronics were implemented, and a sophisticated robotic control system has been implemented. We present for the first time on-sky results from the recently completed ZTF including its realized optical image quality, CCD noise, and observing efficiency performance and discuss engineering challenges that have been overcome. Early scientific results from the ZTF survey are also included.

A single feed cryogenic Q-band (35 – 50 GHz) dual-linear polarization receiver is under development at the NRC, primarily to establish the antenna performance parameters of the Dish Verification Antenna 2 at its high-frequency limit and as a possible receiver system for the National Radio Astronomy Observatory’s Next Generation Very Large Array (ngVLA). The cryostat houses a corrugated feed horn cooled to 16 K with a wide opening half-angle of 55°. The linear orthomode transducer (OMT) was redesigned to incorporate noise injection couplers and the power dividing function thus reducing the amount of components, connections, and thermal mass. The low noise (T LNA = 12 K) amplifier (LNA) was also redesigned to replace coaxial ports with WR-22 waveguide ports. The specifications, receiver design, measured farfield feed horn beam patterns from a near-field planar scanner, simulated OMT results, and sub-20 K receiver noise analysis is presented, along with future plans for production and installation.

The ASTE (Atacama Submillimeter Telescope Experiment) is a 10-m submillimeter telescope located near the ALMA (Atacama Large Millimeter/submillimeter Array) site in Chile. Recently, the ASTE heterodyne receiver system has been upgraded with a new cryostat and two sub-mm-wave heterodyne receivers. The cryostat has three receiver ports. Its cooling capacity is improved with new design compared to a previous three-cartridge cryostat. The two new receivers are dual polarization Superconductor-Insulator-Superconductor (SIS) sideband-separating receivers in 345 GHz and 460 GHz bands. The 345 GHz band receiver has 55 GHz bandwidth. The single-sideband noise temperature TSSB measured in the laboratory is between 62 K and 440 K. The 460 GHz band receiver was originally an engineering qualification model of the ALMA Band 8 cartridge. The design of SIS mixer devices has been optimized for full coverage of ALMA Band 8 frequency (385-500 GHz). TSSB of the receiver is between 98 K and 257 K. The receiver system was installed on ASTE in March 2017. We have started to provide it for open-use observations after our CSV (Commissioning and Science Verification) activities.

The Tomographic Ionized-carbon Mapping Experiment (TIME) utilizes grating spectrometers to achieve instantaneous wideband coverage with background-limited sensitivity. A unique approach is employed in which curved gratings are used in parallel plate waveguides to focus and diffract broadband light from feed horns toward detector arrays. TIME will measure singly ionized carbon fluctuations from 5 < z < 9 with an imaging spectrometer. 32 independent spectrometers are assembled into two stacks of 16, one per polarization. Each grating has 210 facets and provides a resolving power R of ~ 200 over the 186–324 GHz frequency range. The dispersed light is detected using 2-D arrays of transition edge sensor bolometers. The instrument is housed in a closed-cycle 4K–1K–300mK cryostat. The spectrometers and detectors are cooled using a dual-stage 250/300 mK refrigerator.

In this paper the authors present a concept, design, implementation and results of a vacuum and cryogenic system for the ESPRESSO VLT instrument. The system is comprised of two major control functionalities: vacuum and cryogenics. The Vacuum system is a shared manifold for five chambers, and includes a pre-pump and a turbo molecular pump as vacuum sources. The Cryogenic System is based on a continuous circulation of Liquid Nitrogen (LN2). One shared LN2 line is used for supply and control of the cool down of two detector cryostats and two sorption pumps (also called cryopumps). The Cryopumps are a passive vacuum pumps to compensate for the outgassing of the big vacuum chamber (volume approx.10 m 3 ), minimizing vibrations during operation. The control of the Vacuum System is PLC-based, whereas the Cryogenic is PPC (Program and Process Control) and Lakeshore 336 based. There is special emphasis on the temperature stability of the detector cryostat (goal

Copyright 2018 Society of Photo-Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. The X-IFU instrument of the ATHENA mission requires a set of thermal filters to reduce the photon shot noise onto its cryogenic detector and to protect it from molecular contamination. A set of five filters, operating at different nominal temperatures corresponding to the cryostat shield temperatures, is currently baselined. The knowledge of the actual filter temperature profiles is crucial to have a good estimation of the radiative load on the detector. Furthermore, a few filters may need to be warmed-up to remove contaminants and it is necessary to ensure that a threshold temperature is reached throughout the filters surface. For these reasons, it is fundamental to develop a thermal modeling of the full set of filters in a representative configuration. The baseline filter is a polyimide membrane 45 nm thick coated with 30 nm of highpurity aluminum, mechanically supported by a metallic honeycomb mesh. In this paper, we describe the implemented thermal modeling and report the results obtained in different studies: (i) a trade-off analysis on how to reach a minimum target temperature throughout the outer filter, (ii) a thermal analysis when varying the emissivity of the filter surfaces, and (iii) the effect of removing one of the filters.

Microwave Kinetic Inductance Detectors, or MKIDS, have the ability to simultaneous resolve the wavelength of individual photons and time tag photons with microsecond precision. This opens up a number of exciting new possibilities and efficiency gains for optical/IR astronomy. In this paper we describe a plan to take the MKID technology, which we have demonstrated on the Palomar, Lick, and Subaru Telescopes, out of the realm of private instruments usable only by experts. Our goal is to incorporate MKIDs into a facility-class instrument at the Keck 1 Telescope that can be used by a large part of the astronomical community. This new instrument, the Keck Radiometer Array using KID ENergy Sensors (KRAKENS), will be a 30 kpix integral field spectrograph (IFS) with a 42.5” x 45” field of view, extraordinarily wide wavelength coverage from 380-1350 nm, and a spectral resolution R=λ/uλ > 20 at 400 nm. Future add on modules could enable polarimetry and higher spectral resolution. KRAKENS will be built using the same style MKID arrays, cryostat, and similar readout electronics to those used in the successful 10 kpix DARKNESS instrument at Palomar and 20 kpix MEC instrument at Subaru, significantly reducing the technical risk.

The Bench for Optical Testing (BOT) is a test stand that will be used for metrology and optical testing of the Large Synoptic Survey Telescope (LSST) Camera CCD sensors, immediately after the integration step where the sensors are installed into the Cryostat to form the LSST’s 3.2 gigapixel, 640mm diameter focal plane. The BOT uses existing methods to economically verify sensor performance, including measurement of focal plane flatness, CCD sensor spacing, gain stability, cross-talk, flat field images, response in each filter band, and dark level. This paper describes the requirements, design, and preliminary test results for the BOT test equipment.

The Immersion GRating INfrared Spectrometer (IGRINS) was designed for high-throughput with the expectation of being a visitor instrument at progressively larger observing facilities. IGRINS achieves R∼45000 and > 20,000 resolution elements spanning the H and K bands (1.45-2.5μm) by employing a silicon immersion grating as the primary disperser and volume-phase holographic gratings as cross-dispersers. After commissioning on the 2.7 meter Harlan J. Smith Telescope at McDonald Observatory, the instrument had more than 350 scheduled nights in the first two years. With a fixed format echellogram and no cryogenic mechanisms, spectra produced by IGRINS at different facilities have nearly identical formats. The first host facility for IGRINS was Lowell Observatory’s 4.3-meter Discovery Channel Telescope (DCT). For the DCT a three-element fore-optic assembly was designed to be mounted in front of the cryostat window and convert the f/6.1 telescope beam to the f/8.8 beam required by the default IGRINS input optics. The larger collecting area and more reliable pointing and tracking of the DCT improved the faint limit of IGRINS, relative to the McDonald 2.7-meter, by ∼1 magnitude. The Gemini South 8.1-meter telescope was the second facility for IGRINS to visit. The focal ratio for Gemini is f/16, which required a swap of the four-element input optics assembly inside the IGRINS cryostat. At Gemini, observers have access to many southern-sky targets and an additional gain of ∼1.5 magnitudes compared to IGRINS at the DCT. Additional adjustments to IGRINS include instrument mounts for each facility, a glycol cooled electronics rack, and software modifications. Here we present instrument modifications, report on the success and challenges of being a visitor instrument, and highlight the science output of the instrument after four years and 699 nights on sky. The successful design and adaptation of IGRINS for various facilities make it a reliable forerunner for GMTNIRS, which we now anticipate commissioning on one of the 6.5 meter Magellan telescopes prior to the completion of the Giant Magellan Telescope.

Copyright 2018 Society of Photo-Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. The X-ray Integral Field Unit (X-IFU) is one of the two instruments of the Athena astrophysics space mission approved by ESA in the Cosmic Vision 2015-2025 Science Programme. The X-IFU consists of a large array of transition edge sensor micro-calorimeters that will operate at 100 mK inside a sophisticated cryostat. A set of thin filters, highly transparent to X-rays, will be mounted on the opening windows of the cryostat thermal shields in order to attenuate the IR radiative load, to attenuate radio frequency electromagnetic interferences, and to protect the detector from contamination. Thermal filters are critical items in the proper operation of the X-IFU detector in space. They need to be strong enough to survive the launch stresses but very thin to be highly transparent to X-rays. They essentially define the detector quantum efficiency at low energies and are fundamental to make the photon shot noise a negligible contribution to the energy resolution budget. In this paper, we review the main results of modeling and characterization tests of the thermal filters performed during the phase A study to identify the suitable materials, optimize the design, and demonstrate that the chosen technology can reach the proper readiness before mission adoption.

In order to accommodate new instrumentation arriving in early 2018, the Canada-France-Hawaii Telescope (CFHT) converted one of its coude spectrograph rooms into a cleanroom. The new instrumentation required ISO 8 conditions with a desired performance of ISO 7. The turn-key solutions available all provide much higher levels of performance at prices well outside the budget of the project, so we modified the room using a more cost effective in-house approach. We discuss the requirements of the new instrumentation, new administrative rules and procedures, changes made to the room and new equipment, and the resulting performance.

We present the mechanical device used to install the Raft Tower Modules (RTMs) into the cryosat of the camera for the Large Synoptic Survey Telescope (LSST). In an RTM, the charge-coupled devices (CCDs) are packaged into a 3 x 3 Raft Sensor Assembly (RSA) and coupled to a Raft Electronics Crate (REC). An RTM weighs ~10 kg, is roughly 500 mm tall, and has a 126.5 mm-square footprint at the CCDs. The grid array which supports the RTM in the cryostat has a center-to-center distance of 127 mm. One of the key challenges for installing the RTMs in the 500 μm gap between CCDs of adjacent modules - contact between adjacent CCDs is strictly forbidden.

Single-photon avalanche diodes (SPADs) must be integrated on modern highly-scaled process nodes to achieve high array fill factors and imager pixel counts. Integration also enables applications where rapid, complex data processing needs to be co-located with these detectors and other photonic components. In this work we implement 5μm, 10μm, and 15μm-diameter circular SPADs using a p+/n-well structure and an STI guard ring in a 90nm bulk CMOS process, and in contrast to previous work on silicon SPADs carry out detailed study of dark count rate (DCR) and afterpulsing at cryogenic temperatures. With passive quenching these SPADs are saturated by dark counts at room temperature and by afterpulsing at cryogenic temperatures, motivating the development of an active quenching circuit (AQC) to characterize and ultimately suppress the processes responsible for these non-idealities. A novel AQC topology based on a linear output stage, able to detect avalanches and drive SPADs connected by a coaxial cable faster than previously-demonstrated circuits, is proposed and demonstrated. This circuit enables device testing using a coaxial microprobe inside a Helium cryostat. To quantify the SPADs’ performance, we operate them in free-running mode and collect histograms of the pulse interarrival times from which we extract the DCR and afterpulsing probability. We use this technique to measure these parameters with varying temperature and overbias voltage, showing there is an optimal temperature for operating each SPAD. With active quenching we achieve 100Hz-level DCR, 10% 405nm quantum efficiency at 140K, and are presently characterizing the photon detection probability.

Superconducting single photon detectors are promising candidates for cutting-edge applications like space-to-ground communication and quantum-key-distribution. The challenge is to transfer the assembly technology from university research to industrial processes. Especially the positioning of the optical fiber with respect to the active area of the superconducting detector are open questions. We demonstrate the operation of a superconducting nanowire single photon detector (SNSPD) in a closed cycle cryostat. The thermal coupling between superconducting detector chip and closed-cycle cryostat is investigated. The possibility to mount the optical fiber in an RIE-ICP-etched hole in a silicon carrier wafer is demonstrated. Different illumination wavelength and intensities are used to validate the SNSPD assembly in the closed cycle cryostat. Further, an advanced package of the silicon carrier wafer and the SNSPD-chip is introduced. In this package, the SNSPD-chip is mounted via flip-chip technology on the silicon carrier wafer. The striven flip-chip position accuracy of ± 1 μm ensures the accurate coupling between optical fiber and active area of the SNSPD.