Franklin Miller

A helium based pulsating heat pipe for superconducting magnets

Working Paper Department of Mechanical Engineering, University of Wisconsin - Madison, Estados Unidos

Modeling and development of a superfluid magnetic pump with no moving parts

Current state of the art sub Kelvin Superfluid Stirling Refrigerators and Pulse tube Superfluid Refrigerators use multiple bellows pistons to execute the cycle. These types of displacers can be replaced by a newly introduced pump, a Superfluid Magnetic Pump, with no moving parts. Integration of this pump in the Pulse tube Superfluid Refrigeration system will make it a sub Kelvin Stirling refrigeration system free of any moving parts that is suitable for use in space cooling applications. The Superfluid Magnetic Pump consists of a canister that contains Gadolinium Gallium Garnet particles that is surrounded by a superconducting magnetic coil. The driving mechanism of this pump is the fountain effect in He II. A qualitative description of one cycle operation of the Superfluid Magnetic Pump is presented followed by a numerical model for each process of the cycle.

Development of a Numerical Model of a Superfluid Magnetic Pump for Space Science Applications

A superfluid magnetic helium pump that requires no moving parts is described. The pump consists of a canister filled with Gadolinium Gallium Garnet particles surrounded by a superconducting magnetic coil. This pump is capable of driving thermodynamic refrigeration cycles that provide cooling for space science detectors at temperatures below 100mK. A numerical model that predicts pump performance is presented. This model has been used to design a prototype superfluid magnetic pump.

Novel 4He Circulator for Cooling of Large Space Superconducting Magnets

Large superconducting magnets are used in various space science applications (that is, particle detectors designed to search for antimatter, dark matter, and the origin of cosmic rays in space). To prevent or recover from a potential magnet quench, it is extremely important to control the operating temperature of superconducting magnets. One effective method for maintaining superconducting coils at sufficiently low temperatures while in application is to exchange heat with He-II, which exhibits an abnormally high, effective thermal conductivity (≥80,000  W/m·K) under certain conditions. In this work, a novel superfluid magnetic pump with no moving parts is discussed as a new method for maintaining magnet coils below their superconducting transition temperature Tc. Unlike traditionally used thermomechanical pumps, the superfluid magnetic pump will have minimal superfluid helium depletion and will be able to provide flow rates that enable maintaining of the superconducting magnet coils at low temperatures.

Economic assessment and optimal operation of CSP systems with TES in California electricity markets

The economics and performance of concentrated power (CSP) systems with thermal energy storage (TES) inherently depend on operating policies and the surrounding weather conditions and electricity markets. We present an integrated economic assessment framework to quantify the maximum possible revenues from simultaneous energy and ancillary services sales by CSP systems. The framework includes both discrete start-up/shutdown restrictions and detailed physical models. Analysis of coinci-dental historical market and meteorological data reveals provision of ancillary services increases market revenue 18% to 37% relative to energy-only participation. Surprisingly, only 53% to 62% of these revenues are available through sole participation in the day-ahead market, indicating significant opportunities at faster timescales. Motivated by water-usage concerns and permitting requirements, we also describe a new nighttime radiative-enhanced dry-cooling system with cold-side storage that consumes no water and offers higher effciencies than traditional air-cooled designs. Operation of this new system is complicated by the cold-side storage and inherent coupling between the cooling system and power plant, further motivating integrated economic analysis.The economics and performance of concentrated power (CSP) systems with thermal energy storage (TES) inherently depend on operating policies and the surrounding weather conditions and electricity markets. We present an integrated economic assessment framework to quantify the maximum possible revenues from simultaneous energy and ancillary services sales by CSP systems. The framework includes both discrete start-up/shutdown restrictions and detailed physical models. Analysis of coinci-dental historical market and meteorological data reveals provision of ancillary services increases market revenue 18% to 37% relative to energy-only participation. Surprisingly, only 53% to 62% of these revenues are available through sole participation in the day-ahead market, indicating significant opportunities at faster timescales. Motivated by water-usage concerns and permitting requirements, we also describe a new nighttime radiative-enhanced dry-cooling system with cold-side storage that consumes no water and offers high...

Pulsed HTS Coil Performance

HTS coils designed to carry pulsed currents have been built and tested demonstrating fast charge and discharge times on the order of a second. Gaseous Helium from 40 to 80 K is used as a coolant. Losses due to ac, hysteresis, and transport currents associated with current entry into and exiting from HTS are small and do not produce thermal transients that induce current sharing or normal transitions for reasonable margins and operating temperatures. Short lengths of HTS and small coils show current sharing before normal transitions, whereas current sharing voltages are not identified in large coils since current sharing voltages are small compared to inductive and resistive voltages. Pulse shape, duration, and frequency are varied with no degradation in performance.

Construction and experimental validation of a simple, compact, resealable, and reliable Vycor® superleak assembly for use at low temperatures

A new method of constructing a superleak assembly for use in experiments involving (4)He or (3)He-(4)He mixtures at very low temperatures is described. Superleaks are made of a porous medium with very small pores and channels. Superleaks are often incorporated in thermomechanical pumps, superfluid magnetic pumps, dilution refrigerators, and superfluid helium transfer systems. We used several cylindrical pieces of Vycor, a permeable glass with average pore diameter of 40 Å and porosity of 28%, as a candidate to be used in our superleak assembly. Our design is simple and compact. Our superleak assembly can be disassembled and easily reassembled for reuse. We successfully tested and validated this device at temperatures between 1.4 K and 2.7 K. We experienced no superfluid leaks into the surrounding vacuum. We also report that thermal cycling caused no performance degradation. It is our goal to share the design and construction techniques of this new superleak assembly.

OPTIMIZATION OF A TWO‐STAGE ADR FOR THE SOFT X‐RAY SPECTROMETER (SXS) INSTRUMENT ON THE ASTRO‐H MISSION

NASA/Goddard Space Flight Center has begun developing the Soft X‐ray Spectrometer (SXS) instrument that will be flown on the Japanese Astro‐H mission. The SXS’s 36‐pixel detector array will be cooled to 50 mK using a two‐stage adiabatic demagnetization refrigerator (ADR). A complicating factor for its design is that the ADR will be integrated into a superfluid helium dewar at 1.3 K that will be coupled to a 1.8 K Joule‐Thomson (JT) stage through a heat switch. When liquid helium is present, the coupling will be weak, and the JT stage will act primarily as a shield to reduce parasitic heat loads. When the liquid is depleted, the heat switch will couple more strongly so that the ADR can continue to operate using the JT stage as its heat sink. A two‐stage ADR is the most mass efficient option and it has the operational flexibility to work well with a stored cryogen and a cryocooler. The stages are operated independently, and this opens up a very large parameter space for optimizing the design. This paper discusses the optimization process and most relevant trades considered in the design of the SXS ADR, and its expected performance.