Compact and efficient continuous adiabatic demagnetization refrigerator for line emission mapper

Self Cite

.The line emission mapper (LEM) is a probe-class mission concept that is designed to detect x-ray emission lines from hot ionized gas (T > 106 K) that will enable us to test galaxy evolution theories. It will permit us to study the effects of stellar and black-hole feedback and flows of baryonic matter into and out of galaxies. The key to being able to study the hot gases that are otherwise invisible to current imaging x-ray spectrometers is that the energy resolution is sufficient to use cosmological redshift to separate extragalactic source lines from foreground Milky Way emission. LEM incorporates a large-format microcalorimeter array instrument called the LEM microcalorimeter spectrometer (LMS) with a light-weight x-ray optic with 10” half power diameter angular resolution. The LMS microcalorimeter array has pixels with 15″ pixel pitch over a 33′ field of view (FOV) optimized for the 0.3 to 2 keV energy band. The central 7′ region of the array has an energy resolution of 1.3 eV at 1 keV and the rest of the FOV has 2.5 eV energy resolution at 1 keV. The array will be read out with state-of-the-art time-division multiplexing. We present an overview of the LMS instrument, including details of the entire detection chain, the focal plane assembly, as well as the cooling system and overall mechanical and thermal design. For each of the key technologies, we discuss the current technology readiness level and the plan to advance them to be ready for flight. We also describe the current system design and our estimate for the mass, power, and data rate of the instrument. The design details presented concentrate primarily on the unique aspects of the LMS design compared with prior missions and confirm that the type of microcalorimeter instrument needed for LEM is not only feasible but also technically mature.

Section: Filter Wheel Assemblymentioning

confidence: 99%

Line emission mapper microcalorimeter spectrometer

Bandler,

Adams,

Amatucci

et al. 2023

Self Cite

“…The LMS CADR is a highly efficient, compact, and reliable magnetic cooler that offers continuous cooling at 350 and 40 mK, anchored at the 4 K stage of the LMS four-stage pulse tube cryocooler. 4 The system consists of two configurations in series. (A) Four CADR stages are configured as a parallel pair of two serial stages, working together to continuously provide cooling at T1 ¼ 350 mK, with heat rejected to the 4 K cryocooler.…”

Section: Continuous Adiabatic Demagnetization Refrigeratormentioning

confidence: 99%

“…At 4 K, the parasitic heat load margin is 100%, and the 14 mW CADR allocation contains 100% margin at the 40 and 350 mK stages. 4 At 50 K, parasitic heat load includes 50% margin due to the temperature requirements of the HTS cables (which can still operate at somewhat higher temperature).…”

Section: Thermal Analysismentioning

confidence: 99%

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Line emission mapper cryogenic system design

Osborne,

Olson,

Jacoby

et al. 2023

The line emission mapper x-ray microcalorimeter instrument requires a 4 K cryogenic system to precool a continuous adiabatic demagnetization refrigerator enabling high-resolution x-ray spectroscopy. The cryogenic system described in this work provides the required structural and thermal environments using mature cooling and structural technologies. The system is comprised of a dewar design based on heritage manufacturing processes and an efficient four-stage pulse tube cryocooler with supporting control electronics.

“…We describe the key components of the mission but defer presentation of the finer details of the LMS to other contributions in this JATIS special section. [2][3][4][5][6][7] In Sec. 2, we describe the mission, including the spacecraft design, choice of orbit, and operational modes.…”

mentioning

confidence: 99%

Line Emission Mapper: an X-ray probe mission concept to study the cosmic ecosystems and the physics of galaxy formation

Patnaude,

Kraft,

Kilbourne

et al. 2023

In the 2020 Astrophysics Decadal Survey, the National Academies identified cosmic feedback and structure formation as a key question that should drive research in the upcoming decade. In response to this recommendation, NASA released a call for X-ray and IR probe-class missions, with a $1B cost cap. The line emission mapper (LEM) is a mission concept designed in response to this call. LEM is a single-instrument X-ray telescope that consists of a Wolter-Schwarzschild type I X-ray optic with a 4 m focal length, coupled with an X-ray microcalorimeter with a 30′ field of view (FoV), 15″ angular resolution, and 2.5 eV energy resolution [full-width half maximum (FWHM)], with a 1.3 eV FWHM energy resolution central subarray. The high throughput X-ray mirror combined with the large FoV and excellent energy resolution allows for efficient mapping of extended emission-line dominated astrophysical objects from megaparsecs to sub-pc scales to study cosmic ecosystems and unveil the physical drivers of galaxy formation.