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Cryogenic Systems for Sensors and Detectors

Description:

Scope Title:

High-Efficiency Cryocoolers

Scope Description:

Low-temperature coolers:

NASA seeks improvements to multistage low-temperature spaceflight cryocoolers. Coolers are sought with the lowest temperature stage typically in the range of 4 to 10 K, with cooling power at the coldest stage larger than currently available and with high efficiency. The desired cooling power is application specific, but includes a range of approximately 50 to 200 mW at 4 K. Devices that produce extremely low vibration, particularly at frequencies below a few hundred hertz, are of special interest. System- or component-level improvements that improve efficiency and reduce complexity and cost are desirable. Examples of target missions include several concepts currently under study for far-infrared and x-ray probe-class observatories recommended in the 2020 Astrophysics Decadal Survey. In addition to the large coolers, there has recently been interest in small, low-power (~10-mW) 4 K coolers for quantum communication and sensing instruments. 

 

Miniature coolers:

NASA seeks miniature, high-efficiency cryocoolers for instruments on Earth and planetary missions. A range of cooling capabilities is sought. Two examples include 0.2 W at 30 K with heat rejection at 300 K and 0.3 W at 35 K with heat rejection at 150 K. For both examples, an input power of ≤5 W and a total mass of ≤400 g is desired. The ability to fit within the volume and power limitations of a SmallSat platform would be highly advantageous. Cryocooler electronics are also sought in two general categories: (1) low-cost devices that are sufficiently radiation hard for lunar or planetary missions, and (2) very low cost devices for a relatively short term (~1 year) in low Earth orbit. The latter category could include controllers for very small coolers, such as tactical and rotary coolers.
 
  
Heterodyne techniques can achieve very high to extremely high spectral resolution for far-IR spectrometers. Advanced heterodyne receivers operating at 20 K, well above operating temperatures of other superconducting detectors, have been demonstrated. The mixer and low-noise amplifiers in these future advanced heterodyne sensors typically require 50 to 100 mW of cooling at 15 to 20 K, and the local oscillator requires 1 to 2 W cooling power at 80 to 120 K. NASA is seeking advanced multistage cryocooler technologies that will enable these sensors to operate in a SmallSat platform. The cryocooler input power must be compatible with available power in the SmallSat platform, which is typically several tens of watts. 
 
It is desirable that the cooler can efficiently operate over a wide heat sink temperature range, from -50 to 70 ºC.

Expected TRL or TRL Range at completion of the Project: 2 to 5

Primary Technology Taxonomy:

  • Level 1 08 Sensors and Instruments
  • Level 2 08.1 Remote Sensing Instruments/Sensors

Desired Deliverables of Phase I and Phase II:

  • Prototype
  • Hardware

Desired Deliverables Description:

Phase I: Proof-of-concept demonstration.

Phase II: Desired deliverables include coolers and components, such as electronics, that are ready for functional and environmental testing.

State of the Art and Critical Gaps:

Low-temperature coolers:
Current spaceflight cryocoolers for this temperature range include hybrid coolers with a lower Joule-Thompson stage precooled by linear-piston-driven Stirling or pulse-tube upper stage at about 20 K. One such state-of-the-art cryocooler, the
Mid-Infrared Instrument (MIRI) cooler on the James Webb  Space Telescope (JWST), provides about 55 mW of cooling at 6 K. For large future space observatories, large cooling power and much greater efficiency will be needed. For cryogenic instruments or detectors on instruments with tight pointing requirements, orders-of-magnitude improvement in the levels of exported vibration will be required. Some of these requirements are laid out in the "Advanced cryocoolers" Technology Gap in the latest (2017) Cosmic Origins Program Annual Technology Report.

Miniature coolers:
Present state-of-the-art cryocoolers can achieve Carnot efficiency above 13% and specific mass lower than 0.75 kg/W of cooling at 77 K for cooling capacity under 1 W at 77 K. 
 
Cryocoolers enable the use of highly sensitive detectors, but current coolers cannot operate within the tight power constraints of outer planetary missions.  There are no lightweight cryocoolers (<3 kg) that can provide cooling below 20 K. Cryocooler power could be greatly reduced by lowering the heat rejection temperature, but presently there are no spaceflight systems that can operate with a heat rejection temperature significantly below ambient.

 

Relevance / Science Traceability:

Science traceability (from NASA's Strategic plan): 

  • Goal 1: Expand the frontiers of knowledge, capability, and opportunity in space.
  • Objective 1.6: Discover how the universe works, explore how it began and evolved, and search for life on planets around other stars.


Low-temperature cryocoolers are listed as a "Technology Gap" in the latest (2017) Cosmic Origins Program Annual Technology Report. Future missions that would benefit from this technology include the far-infrared- and X-ray-probe-class observatories recommended by the 2020 Astrophysics Decadal Survey, as well, in the more distant future, far-infrared and x-ray flagships.

 

NASA is moving toward the use of small, low-cost satellites to achieve many of its Earth science and some of its planetary science goals. The development of cryocoolers that fit within the size and power constraints of these platforms will greatly expand their capability, for example, by enabling the use of infrared detectors.

 

In planetary science, progress on cryogenic coolers will enable the use of far- to mid-infrared sensors with orders-of-magnitude improvement in sensitivity for outer planetary missions. These will allow thermal mapping of outer planets and their moons.

References:

  • Examples of mission concepts for the far-IR probe include: 

    • PRIMA (Probe Far-Infrared Mission for Astrophysics, which is based on the Galaxy Evolution Probe (GEP); see Moore et al.: "Thermal architecture of the galaxy evolution probe mission concept," Proc. SPIE, 10698, 1069858, 2018, doi.org/10.1117/12.2314237)

    • SPICE (Space Interferometer for Cosmic Evolution, which is based on the Space Infrared Interferometric Telescope (SPIRIT) concept; see DiPirro, M. et al.: "The SPIRIT thermal system," Proc. SPIE, 6687, 66870D, 2007, doi.org/10.1117/12.734140)

  • Example of Astrophysics flagship mission concepts include:

Scope Title:

Actuators and Other Cryogenic Devices

Scope Description:

NASA seeks devices for cryogenic instruments, including:

 

  • Small, precise motors and actuators, preferably with superconducting windings, that operate with extremely low power dissipation. Devices using standard NbTi conductors, as well as devices using higher temperature superconductors that can operate above 5 K, are of interest.
  • Cryogenic heat pipes for heat transport within instruments. Heat pipes using hydrogen, neon, oxygen, argon, and methane are of interest. Length should be at least 0.3 m.  Devices that have reduced gravitational dependence and that can be made low profile, or integrated into structures such as radiators, are of particular interest.
  • Reliable solid-state conductors with variable thermal conductance ranging from 0.05 W/K to 0.005 W/K to allow one cryocooler to efficiently provide cooling for two or more targets operating at significantly different temperatures, maintaining them at their calibration temperatures even when their heat load ratios deviate significantly from design values. This technology would eliminate the need to iteratively alter the conductors to tune their conductance ratio during cryogenic instrument calibration stage, significantly reducing cryogenic infrared (IR) spectrometer integration and testing cost. 
     

Expected TRL or TRL Range at completion of the Project: 3 to 4

Primary Technology Taxonomy:

  • Level 1 08 Sensors and Instruments
  • Level 2 08.1 Remote Sensing Instruments/Sensors

Desired Deliverables of Phase I and Phase II:

  • Prototype
  • Hardware

Desired Deliverables Description:

Phase I: Proof-of-concept test on a breadboard-level device.

Phase II: Working prototypes ready for testing in the relevant environments.

State of the Art and Critical Gaps:

Motors and actuators: Instruments often have motors and actuators, typically for optical elements such as filter wheels and Fabry-Perot interferometers. Current cryogenic actuators are typically motors with resistive (copper) windings. Although heat generation is naturally dependent on the application, an example of a recent case is a stepper motor used to scan a Fabry-Perot cavity; its total dissipation (resistive + hysteric) is ~0.5 W at 4 K.  A flight instrument would need heat generation of at least 20× less.

Cryogenic heat pipes: Heat transport in cryogenic instruments is typically handled with solid thermal straps, which do not scale well for larger heat loads. Currently available heat pipes are optimized for temperatures above ~120 K. They have limited capacity to operate against a gravitational potential, which complicates ground testing. 

Current conductors with a thermal switch can only operate in the ON or OFF mode, but not in a mode where its thermal conductance can be varied continuously with negligible (<50 mW) active control power in the temperature range of 120 to 180 K.

Relevance / Science Traceability:

Science traceability: NASA Strategic plan 2018, Objective 1.1: Understand The Sun, Earth, Solar System, and Universe.

Almost all instruments have motors and actuators for changing filters, adjusting focus, scanning, and other functions. On low-temperature instruments, for example on mid- to far-IR observatories, dissipation in actuators can be a significant design problem.

References:

For more information on earlier low-temperature heat pipes:

Scope Title:

Sub-Kelvin Cooling Systems

Scope Description:

Future NASA missions will require sub-Kelvin coolers for extremely low temperature detectors. Systems are sought that will provide continuous cooling with high cooling power (>5 µW at 50 mK), and high heat rejection temperature (10 K), while maintaining high thermodynamic efficiency and low system mass.

 

 

Improvements in components for adiabatic demagnetization refrigerators are also sought. Specific components include:

 

(1) High-cooling-power-density magnetocaloric materials. Examples of desired materials include GdLiF4, Yb3Ga5O12, GdF3, and Gd elpasolite. High-quality single crystals are preferred because of their high conductivity at low temperature, but high-density polycrystals are acceptable in some forms. Total volume must be >40 cm3. For polycrystalline materials, this could be composed of smaller sections.

 

(2) Compact, lightweight, low-current superconducting magnets capable of producing a field of at least 4 tesla (T) while operating at a temperature of at least 10 K, and preferably above 15 K. Desirable properties include:

  • A high engineering current density (including insulation and coil packing density), preferably >300 A/mm2.
  • A field/current ratio of >0.5 T/A, and preferably >0.66 T/A.
  • Low hysteresis heating. 
  • Bore diameters ranging between 22 and 40 mm, and lengths ranging between 50 and 100 mm, depending on the application. 

 

(3) Shielding requirements include: 

  • Lightweight active/passive magnetic shielding (for use with 4-T magnets) with low hysteresis and eddy current losses as well as low remanence. Shields should reduce stray field to <0.1 mT at 100 mm from the outer surface.  In addition to simple cylinders, toroidal and other self-shielding geometries will be considered. 
  • Lightweight, highly effective outer shields that reduce the field outside an entire multistage device to <5 µT. Outer shields must operate at 4 to 10 K and must have penetrations for low-temperature, noncontacting heat straps.  

 

(4) Heat switches with on/off conductance ratio >30,000 and actuation time of <10 s.  Switches are sought to cover the temperature range 20 K > T > 0.03 K, though the hot/cold temperature ratio for any one switch is typically <5.  They should have an on-state conductance of >(500 mW/K) x (T/4.5 K).  Devices with no moving parts are preferred.  

 

(5) Suspensions with the strength and stiffness of Kevlar®, but lower thermal conductance from 4 to 0.050 K.

Expected TRL or TRL Range at completion of the Project: 2 to 4

Primary Technology Taxonomy:

  • Level 1 08 Sensors and Instruments
  • Level 2 08.1 Remote Sensing Instruments/Sensors

Desired Deliverables of Phase I and Phase II:

  • Prototype
  • Hardware

Desired Deliverables Description:

Phase I: For components, a subscale prototype that proves critical parameters. For systems, a proof-of-concept test.

Phase II: For components, functioning hardware that is directly usable in NASA systems. For systems, a prototype that demonstrates critical performance parameters.

State of the Art and Critical Gaps:

The adiabatic demagnetization refrigerator in the Soft X-ray Spectrometer instrument on the Hitomi mission represents the state of the art in spaceflight sub-Kelvin cooling systems. The system is a 3-stage, dual-mode device. In the more challenging mode, it provides 650 µW of cooling at 1.625 K, while simultaneously absorbing 0.35 µW from a small detector array at 0.050 K. It rejects heat at 4.5 K. In this mode, the detector is held at temperature for 15.1-h periods, with a 95% duty cycle. Future missions with much larger pixel count will require much higher cooling power at 0.050 K or lower, higher cooling power at intermediate stages, and 100% duty cycle. Heat rejection at a higher temperature is also needed to enable the use of a wider range of more efficient cryocoolers.

Relevance / Science Traceability:

Science traceability: NASA Strategic plan 2018, Objective 1.1: Understand The Sun, Earth, Solar System, And Universe.

Sub-Kelvin coolers are listed as a "Technology Gap" in the latest (2017) Cosmic Origins Program Annual Technology Report.

Missions that would benefit from this technology include several concepts presently under development for the far-infrared and X-ray probe-class missions recommended in the 2020 Astrophysics Decadal Survey, as well as future far-infrared and X-ray flagship missions.

References:

For a description of the state-of-the-art sub-Kelvin cooler in the Hitomi mission:

  • Shirron, et al.: "Thermodynamic performance of the 3-stage ADR for the Astro-H Soft-X-ray Spectrometer instrument," Cryogenics, 74, pp. 24-30, 2016, and references therein.

 

For articles describing magnetic sub-Kelvin coolers and their components:

  • Cryogenics, 62, pp. 129-220, July 2014 special issue.

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