Optimum operating regimes of common paramagnetic refrigerants

Wikus, P.; Burghart, G.; Figueroa‐Feliciano, E.

doi:10.1016/j.cryogenics.2011.07.001

Cited by 18 publications

(15 citation statements)

References 10 publications

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“…Here we give a brief account of it, noting that the cooling is possible due to the magnetocaloric effect in certain paramagnetic materials that possess a large magnetic entropy at low temperatures. Assuming FAA to be a collection of noninteracting magnetic dipoles, one obtains the dependence of its magnetic entropy on the temperature T and the external field B 52 as: Here n is the number of moles of FAA in the ADR pill, R is the ideal gas constant, µ B is the Bohr magneton, g is the g-factor of an electron, k B is the Boltzmann constant, and J=5/2 is the total angular momentum of the paramagnetic ions in FAA 52 .…”

Section: Adr Cyclementioning

confidence: 99%

A millikelvin scanning tunneling microscope in ultra-high vacuum with adiabatic demagnetization refrigeration

Esat,

Borgens,

Yang

et al. 2021

Preprint

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We present the design and performance of an ultra-high vacuum (UHV) scanning tunneling microscope (STM) that uses adiabatic demagnetization of electron magnetic moments for controlling its operating temperature in the range between 30 mK and 1 K with the accuracy of up to 7 µK. The time available for STM experiments at 50 mK is longer than 20 h, at 100 mK about 40 h. The single-shot adiabatic demagnetization refrigerator (ADR) can be regenerated automatically within 7 hours while keeping the STM temperature below 5 K. The whole setup is located in a vibrationally isolated, electromagnetically shielded laboratory with no mechanical pumping lines penetrating through its isolation walls. The 1K pot of the ADR cryostat can be operated silently for more than 20 days in a single-shot mode using a custombuilt high-capacity cryopump. A high degree of vibrational decoupling together with the use of a specially-designed minimalistic STM head provides an outstanding mechanical stability, demonstrated by the tunneling current noise, STM imaging, and scanning tunneling spectroscopy measurements all performed on atomically clean Al(100) surface.

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Section: Adr Cyclementioning

confidence: 99%

A millikelvin scanning tunneling microscope in ultra-high vacuum with adiabatic demagnetization refrigeration

Esat,

Borgens,

Yang

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…For reviews of low temperature refrigerants, their cooling capabilities and selection guidelines, see [2,3]. Here we note that the goal is typically to obtain the highest cooling capacity per volume in the salt pill, although some consideration must be given to the chemical properties and, hence, how the material must be packaged.…”

Section: Selection Of Refrigerantmentioning

confidence: 99%

“…The interdependence of these parameters means that many design solutions are possible that achieve the same cooling capacity, but with potentially large variations in total stage mass. In general, though, the choice of refrigerant is guided by relatively straightforward selection rules [2,3], and, as will be seen, it is possible to develop analytic expressions for the optimal magnetic field as a function of the ADR's operating temperature range, which can then be used to compute the refrigerant mass needed to obtain the desired cooling capacity. When applied to single ADR stages, these yield designs for which the cooling capacity per unit mass is maximized.…”

Section: Introductionmentioning

confidence: 99%

Optimization strategies for single-stage, multi-stage and continuous ADRs

Shirron

2014

Cryogenics

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“…There are many magnetic materials that can be used in ADR systems. A review of the most common ones can be found in reference [86].…”

Section: Adiabatic Demagnetization Refrigerationmentioning

confidence: 99%

“…The characteristic parameters of the two salt pills are shown in Table 5.1: Properties of paramagnetic refrigeration salts used in this work [86].…”

Section: Principle Of Magnetic Coolingmentioning

confidence: 99%

Development of Metallic Magnetic Calorimeters for Nuclear Safeguards Applications

Bates

2015

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Many nuclear safeguards applications could benefit from high-resolution gamma-ray spectroscopy achievable with metallic magnetic calorimeters. This dissertation covers the development of a system for these applications based on gamma-ray detectors developed at the University of Heidelberg. It demonstrates new calorimeters of this type, which achieved an energy resolution of 45.5 eV full-width at half-maximum at 59.54 keV, roughly ten times better than current state of the art high purity germanium detectors. This is the best energy resolution achieved with a gamma-ray metallic magnetic calorimeter at this energy to date. In addition to demonstrating a new benchmark in energy resolution, an experimental system for measuring samples with metallic magnetic calorimeters was constructed at Lawrence Livermore National Laboratory. This system achieved an energy resolution of 91.3 eV full-width at half-maximum at 59.54 keV under optimal conditions. Using this system it was possible to characterize the linearity of the response, the count-rate limitations, and the energy resolution as a function of temperature of the new calorimeter. With this characterization it was determined that it would be feasible to measure 242 Pu in a mixed isotope plutonium sample. A measurement of a mixed isotope plutonium sample was performed over the course of 12 days with a single two-pixel metallic magnetic calorimeter. The relative concentration of 242 Pu in comparison to other plutonium isotopes was determined by direct measurement to less than half a percent accuracy. This is comparable with the accuracy of the best-case scenario using traditional indirect methods. The ability to directly measure the relative concentration of 242 Pu in a sample could enable more accurate accounting and detection of indications of undeclared activities in nuclear safeguards, a better constraint on source material in forensic samples containing plutonium, and improvements in verification in a future plutonium disposition treaty.

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Optimum operating regimes of common paramagnetic refrigerants

Cited by 18 publications

References 10 publications

A millikelvin scanning tunneling microscope in ultra-high vacuum with adiabatic demagnetization refrigeration

A millikelvin scanning tunneling microscope in ultra-high vacuum with adiabatic demagnetization refrigeration

Optimization strategies for single-stage, multi-stage and continuous ADRs

Development of Metallic Magnetic Calorimeters for Nuclear Safeguards Applications

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