Cryogenic Facility for Prototyping ET-LF Payloads Using Conductive Cooling

We present the design and commissioning of a cryogenic low-vibration test facility that measures displacement noise from a gram-scale silicon cantilever at the level of 10-16m/Hz at 1kHz. This sensitivity is necessary for future tests of thermal noise models on cross sections of silicon suspension samples proposed for future gravitational-wave detectors. A volume of ∼36 l is enclosed by radiation shields cooling an optical test cavity that is suspended from a multi-stage pendulum chain providing isolation from acoustic and environmental noise. This 3kg test cavity housing a crystalline silicon cantilever is radiatively cooled to 123K in 41h and held at that temperature over many months with a relative temperature stability of ±1 mK. The facility housing the test cavity is sensitive to cavity length changes, which can resolve thermal fluctuations at the desired sensitivity. It is capable of interferometrically measuring temperature-dependent broadband displacement noise directly between 50Hz and 10kHz, where current and future ground-based gravitational wave observatories are the most sensitive. With a suitable cantilever design, the cryogenic facility we describe here will allow for the measurement of broadband thermal noise in crystalline silicon at 123K. This will guide the design of suspensions in planned future cryogenic ground-based gravitational-wave detectors such as LIGO Voyager and may have implications for suspensions in the Einstein Telescope. This facility is also suitable for the testing of new mirror coatings at cryogenic temperatures.

A concept is presented for a national cryogenic optics test facility capable of optical characterization of 1.25-m-diameter optics having focal lengths up to 6.2 m at temperatures from 300 K to near 4 K. The facility will be comprised of a large Dewar with a phase-shift interferometer, a two-stage vacuum system employing a turbomolecular pump, and an integral vibration isolation system. The entire facility will be housed in a concrete site with a massive floor to assist in reducing vibration during optical tests. By providing interchangeable sections, the overall height of the Dewar can be adjusted to provide for testing of shorter focal length optics. This paper discusses the background for the facility, the facility location, and the requirements and the performance considerations which drive the Dewar design with respect to the vibration isolation system, vacuum system, and optical interferometry.

A thermal model of the dewar and optical system of the Cryogenic Optical Test Facility at NASA-Ames Research Center was developed using the computer codes SINDA and MONTE CARLO. The model was based on the geometry, boundary conditions, and physical properties of the test facility and was developed to investigate heat transfer mechanisms and temperatures in the facility and in test mirrors during cryogenic optical tests. A single-arch, fused-natural-quartz mirror was the first mirror whose thermal loads and temperature distributions were modeled. From the temperature distribution, the thermal gradients in the mirror were obtained. The model predicted that a small gradient should exist for the single arch mirror. This was later verified by the measurement of mirror temperatures. The temperatures, predicted by the model at various locations within the dewar, were in relatively good agreement with the measured temperatures. The model is applicable to both steady-state and transient cooldown operations.

Controlling the Stark perturbation from ambient thermal radiation is key to advancing the performance of many atomic frequency standards, including state-of-the-art optical lattice clocks (OLCs). We demonstrate a cryogenic OLC that utilizes a dynamically actuated radiation shield to control the perturbation at 1.7×10^{-20} fractional frequency, a factor of ∼40 beyond the best OLC to date. Our shield furnishes the atoms with a near-ideal cryogenic blackbody radiation (BBR) environment by rejecting external thermal radiation at the part-per-million level during clock spectroscopy, overcoming a key limitation with previous cryogenic BBR control solutions in OLCs. While the lowest BBR shift uncertainty is realized with cryogenic operation, we further exploit the radiation control that the shield offers over a wide range of temperatures to directly measure and verify the leading BBR Stark dynamic correction coefficient for ytterbium. This independent measurement reduces the literature-combined uncertainty of this coefficient by 30%, thus benefiting state-of-the-art Yb OLCs operated at room temperature. We verify the static BBR coefficient for Yb at the low 10^{-18} level.

The JWST (James Webb Space Telescope) primary mirror consists of 18 hexagonal mirror segments each approximately 1.5 meters point to point. The mirror segments are constructed from a lightweight beryllium substrate with both a radius-of-curvature actuation system and a six degree-of-freedom hexapod actuation system. The manufacturing process for each individual mirror assembly takes approximately six years due to limitations dealing with the number of segments and manufacturing & test facilities. In order to catch any manufacturing or technology roadblocks, as well as to streamline specific processes, an Engineering Development Unit (EDU) was built to lead the mirror manufacturing flow. This development unit has all of the same requirements as the flight units and is actually considered to be one of the flight spare mirrors. The EDU was manufactured with a lead time of approximately six months over the other mirrors to assure adequate time to optimize each step in the manufacturing process. Manufacturing and tests occurred at six locations across the U.S. with multiple trips between each. The EDU recently completed this arduous process with the final cryogenic performance test of the mirror assembly taking place at Marshall Space Flight Center's (MSFC) X-Ray & Cryogenic Facility (XRCF). Testing included survivability tests to 25 Kelvin, hexapod & radius-of-curvature actuation systems testing, and cryogenic figure & prescription testing. Presented here is a summary of the tests performed along with the results of that testing.

This paper describes the Optical Ground Support Equipment (OGSE) that is being developed for the payload level testing of the Ariel Space Telescope. Ariel has been adopted as ESA’s “M4” mission in its Cosmic Visions Programme and will launch in 2029 to the second Earth-Sun Lagrange point. During four years of operation the Ariel payload (PL – the cryogenic payload module plus warm units) will perform precise transit spectroscopy of approximately 1000 known exoplanetary atmospheres using a 1.1 m × 0.7 m telescope coupled to two instruments: the Fine Guidance Sensor (FGS) and the Ariel Infrared Spectrometer (AIRS). These instruments provide three spectrometric channels that cover 1.0 to 7.8 μm wavelength range and three photometric channels between 0.5 and 1.1 μm. The Ariel OGSE will verify the optical and radiometric performance of the integrated Ariel PL under vacuum and cryogenic (<40 K) test conditions within the limitations of operation under Earth’s gravity and vibration environments. To achieve these verification requirements the OGSE is integrated with the main Ariel ground test 5 m thermal vacuum chamber. The test chamber contains a cryogenic enclosure (the Cryogenic Test Rig) that surrounds the PL and the OGSE itself comprises of four subsystems. (1) A cryogenic vacuum chamber and integrating sphere illumination module that is fed by visible, near infrared and thermal infrared sources. The illumination module is mounted external to the Ariel test chamber and coupled via a vacuum feedthrough that relays a 22 mm diameter test beam into the Cryogenic Test Rig. The test beam is then relayed using (2) an injection module that steers the beam to maintain alignment during cool-down and scan the Ariel telescope field of view. The beam is then expanded to partially illuminate the Ariel telescope primary mirror using an (3) ~0.3 m diameter target projector collimating mirror. The final optical component of the OGSE is a (4) beam expander placed on the Ariel common optical bench to compensate for the sub-aperture illumination of the primary and to ensure that the spectrometer modules provide illumination with correct cone angles during ground testing. It is planned to use the OGSE in 2026 for a full range of calibration and verification tests of the end-to-end telescope and instrument performance, including detectors, field of view and alignment. These tests will then ensure that Ariel meets it challenging photometric and spectral performance requirements.

The Super Cryogenic Dark Matter Search (SuperCDMS) experiment at SNOLAB explores dark matter candidates in the mass range of 1-10 $\mathrm{GeV/c^2}$. The experiment will deploy a total of 24 detectors with silicon and germanium substrates, 2 km deep underground in SNOLAB, Canada. The detectors are arranged in four towers, combining the low-threshold sensitivity of high-voltage (HV) phonon detectors with the excellent background discrimination of phonon-charge (iZIP)detectors. The combination will give SuperCDMS a world-leading edge in the search for low-mass, low-cross-section dark matter candidates. Over the past year, SuperCDMS completed testing a single HV tower at the Cryogenic Underground TEst facility (CUTE). The CUTE run, which concluded in February 2024, demonstrated the ability to conduct in-situ operations including characterization, calibration, and exploration of Neganov-Trofimov-Luke (NTL) phononamplification. This contribution will highlight key results from CUTE, along with the current status and prospects of the first SuperCDMS science run.

This paper extends the previously reported results of cryogenic optical testing (SPIE Volume 2543, 1995) by including the results of further reduction of the test data for the 170-mm-diameter silicon carbide mirror and the 178-mm- diameter aluminum mirror. Both mirrors were manufactured by the Vavilov State Optical Institute, St. Petersburg, Russia, for infrared applications and were loaned to LMMS for these tests. Optical tests were performed in the Lockheed Martin cryogenic optical test facility at liquid helium temperatures, using a Zygo Mark II interferometer. The initial surface figures were 0.18 waves and 0.08 waves for the aluminum and the SiC mirrors, respectively, with figure error being given as rms wavefront error at 0.6328-micron wavelength at room temperature. It was found that the maximum change in shape after cooling was between 0.007 and 0.036 waves for the SiC mirror and between 0.017 and 0.062 waves for the aluminum mirror.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The dynamic losses in fast ramped super ferric magnets will create the main part of the expected heat losses in the superconducting synchrotron SIS100 – the primary accelerator in the Facility for Antiproton and Ion Research (FAIR). The data measured on dipole models at the cryogenic magnet test facility at GSI allow to predict the static and dynamic losses in the superconducting magnets for different operation modes of the SIS100 synchrotron. The calculations of the expected mass flow rates in the cooling channels of the superconducting magnets together with the analysis of the cooling system for different operation modes of the synchrotron will be presented.

As a coating made of highly porous zeolite materials, the Molecular Adsorber Coating (MAC) was developed to capture outgassed molecular contaminants, such as hydrocarbons and silicones. For spaceflight applications, the adsorptive capabilities of the coating can alleviate on-orbit outgassing concerns on or near sensitive surfaces and instruments within the spacecraft. Similarly, this sprayable paint technology has proven to be significantly beneficial for ground based space applications, in particular, for vacuum chamber environments. This paper describes the recent use of the MAC technology during Pathfinder testing of the Optical Ground Support Equipment (OGSE) for the James Webb Space Telescope (JWST) at NASA Johnson Space Center (JSC). The coating was used as a mitigation tool to entrap persistent outgassed contaminants, specifically silicone based diffusion pump oil, from within JSC's cryogenic optical vacuum chamber test facility called Chamber A. This paper summarizes the sample fabrication, installation, laboratory testing, post-test chemical analysis results, and future plans for the MAC technology, which was effectively used to protect the JWST test equipment from vacuum chamber contamination.

Cryostar announces new cryogenic pump testing facility

This study uses a secondary liquified natural gas (LNG) high-pressure pump with a large mass motor and thin, long pump units as the experimental model. There are certain limitations in controlling the amplitude of the pump unit with two-plane balancing considering the vibration response due to the imbalance in the conventional motor unit. Balancing techniques are required to effectively reduce the vibration response due to an imbalance in the motor unit and mode of the pump unit. Therefore, in this study, four sensors were added to the pump unit to consider their effects on the motor unit and mode to determine dedicated balancing techniques using the impact coefficient method after data acquisition.

A 15.5 T superconducting magnet and a variable temperature insert (VTI) system were installed at a radiation control area in Oarai center in Tohoku University to investigate the superconducting properties of activated superconducting materials by fast neutron. The superconductivity was measured at cryogenic temperature and high magnetic field. During these tests, some inconvenient problems were observed and the additional investigation was carried out. The variable temperature insert was designed and assembled to perform the superconducting property tests. without the liquid helium. To remove the heat induced by radiation and joule heating, high purity aluminum rod was used in VTI. The thermal contact was checked by FEM analysis and an additional support was added to confirm the decreasing the stress concentration and the good thermal contact. After the work for improvement, it was affirmed that the test system works well and all troubles were resolved. In this report, the improved technical solution is described and the first data set on the irradiation effect on Nb3Sn wire is presented.

To ensure proper forced flow cooling of superconducting magnetsin nuclear fusion reactor, sufficient mass flow rate with proper pressure head of cryogen is one of the critical parameters with respect to the operation scenarios involved. Under this condition, the role of cold circulating pump (CCP) is vital as it operates across the operation spectrum often without any redundancy. Consequently, a test is proposed in cryogenic test facility at Japan to simulate the thermo-hydraulic conditions with CCP, before actual operational deployment. Essential components for test are housed in a Cold Valve Box (CVB). Internal piping system of CVB is prone to experience random vibration during transport and installation in addition to ground acceleration during seismic event. The paper presents conceptual design as well as the associated seismic and random vibration analysis of CVB to ensure design safety within the relevant response spectrum likely to occur during its operational life.

A new 4.5K cold box at Jefferson Lab (JLab) Cryogenic Test Facility (CTF) was recently installed and commissioned to upgrade the existing 4.5 K refrigeration system and work in parallel with the existing 4.5 K cold box. This new 4.5 K cold box is equipped with two turbo-expanders and, at its maximum capacity condition, it is expected to support at least 6.6 g/s of helium liquefaction or 650 W of refrigeration at 4.5 K. It can also handle up to 10 g/s 30 K return flow for 2 K refrigeration recovery that supports cryo-module and superconducting cavity testing. Performances of the cold box at its maximum capacity conditions as well as several other operating modes were tested for acceptance. We will briefly review the new 4.5 K cold box design features and discuss the commissioning and performance testing results.