Cryogenics

Methanol is a very ubiquitous molecule in space. A previous combined analysis of microwave and millimeter wave spectra of C-13 methanol together with Fourier transform far-infrared spectra was limited to the first two torsional states (i.e. ¢¡ ¤£ ¦¥ and 1 for § values up to 20). a We have recently carried out new millimeter and terahertz measurements for © CH © OH on several different spectrometers in the Cologne laboratory to overcome the limits in frequency and quantum number coverage. The new measurements have been carried out in the frequency windows 34-70 GHz, 75-120 GHz, 240-340 GHz, 370-500 GHz and 1.12-1.35 THz. With the new data, we are extending our previous global treatment to include the first three torsional states (i.e. ¡ £ ¥ , 1 and 2 for § values up to 30). We hope to provide the radio astronomical community with a C-13 methanol database that will have been improved substantially compared to the existing one. b The new database will be available in the Cologne Database for Molecular Spectroscopy, CDMS c , in support of present and future astronomical studies associated with the launch of HIFI (Heterodyne Instrument for the Far-Infrared) on board the Herschel Space Observatory, the flying of SOFIA (Stratospheric Observatory For Infrared Astronomy) and the commissioning of ALMA (Atacama Large Millimeter/Submillimeter Array).

Passive cooling has shown to be a very dependable cryogenic cooling method for space missions. Several missions employ passive radiators to cool down their delicate sensor systems for many years, without consuming power, without exporting vibrations or producing electromagnetic interference. So for a number of applications, passive cooling is a good choice. At lower temperatures, the passive coolers run into limitations that prohibit accommodation on a spacecraft. The approach to this issue has been to find a technology able to supplement passive cooling for lower temperatures, which maintains as much as possible of the advantages of passive coolers. Sorption cooling employs a closed cycle Joule-Thomson expansion process to achieve the cooling effect. Sorption cells perform the compression phase in this cycle. At a low temperature and pressure, these cells adsorb the working fluid. At a higher temperature they desorb the fluid and thus produce a high-pressure flow to the expander in the cold stage. The sorption process selected for this application is of the physical type, which is completely reversible. It does not suffer from degradation as is the case with chemical sorption of, e.g., hydrogen in metal hydrides. Sorption coolers include no moving parts except for some check valves, they export neither mechanical vibrations nor electromagnetic interference, and are potentially very dependable due to their simplicity. The required cooling temperature determines the type of working fluid to be applied. Sorption coolers can be used in conjunction with passive cooling for heat rejection at different levels. This paper starts with a brief discussion on applications of passive coolers in different types of orbits and on the limitations of passive cooling for lower cooling temperatures. Next, the working principle of sorption cooling is summarized. The DARWIN mission is chosen as an example application of sorption and passive cooling and special attention is paid to the reduction of the radiator area needed by the sorption cooler. The application field of this type of sorption cooling in space missions is currently being expanded by examining the performance of alternative working fluids, suitable for different cooling temperatures.

At the University of Twente, a breadboard 4.5 K helium sorption cooler was developed which has no moving parts and, therefore, is essentially vibration-free. Moreover, it has the potential of a very long lifetime. This cooler is a favorite option for future missions such as ESA's Darwin mission, which is a space interferometer consisting of a few free flying telescopes. Because of the optics involved in Darwin, hardly any vibration can be tolerated. The cooler consists of a hydrogen stage cooling from 80K to 14.5K and a helium stage establishing 5 mW at 4.5 K. Both stages use micro-porous activated carbon as the adsorption material. The two cooler stages need about 3.5 W of total input power and are heat sunk at two passive radiators at temperatures of about 50 and 80 K -radiators which are constructed at the cold side of the spacecraft. We developed, built and tested a demonstrator of the helium stage under an ESA-TRP contract. This demonstrator has four sorption compressor cells in two compressor stages. Test experiments on this cooler showed that it performs within all specifications imposed by ESA. The cooler delivered 4.5 mW at 4.5 K with a long-term temperature stability of 1 mK and an input power of 1.96 W. The exported vibrations are much lower than the required 1 μN/√Hz. So far, the cooler has continuously operated for a period of 2.5 months and has not shown any sign of performance degradation.

This paper presents a check valve with integrated filter that can stand gas pressures of more than 100 bar in the closed direction and which has a very low pressure drop at low absolute gas pressures in the forward direction. The check valve is designed as a part of a check valve unit for application in a miniature cooler for cryogenic temperatures (< 120 K). This cooling system, which utilizes several micromachined components, will in this paper be introduced to the MEMS field.

In this chapter an overview is presented of a number of cooling cycles that can be applied in cryocoolers. Emphasis is put on thermodynamic theory, conceptual operation and possible loss mechanisms. The chapter serves as a conceptual framework on cryocooler theory which is referred to throughout this thesis. The following regenerative cooling cycles are discussed: Stirling, Gifford-McMahon, Vuillemier and pulse-tube. A new regenerative cooling cycle is proposed which appears particularly suitable to be applied on micro-scale. Furthermore, the following recuperative cooling cycles are discussed: Vapor compression cycle, Linde-Hampson and Joule-Brayton cycle. Some alternative solid-state cooling cycles are also discussed: thermoelectric cooling, magnetocaloric and optical cooling. * Notice that the cycle is a simplified thermodynamical description. T-S and p-v diagrams cannot be given for all gas simultaneously in a complete cycle, but only for small amounts of moving gas in the system. * Notice that c p should be used to calculate the heat transfer to the regenerator, although the gas movement seems to be a constant volume process! The use of c p is explained by the infinitesimal steps that occur at constant pressure. Some textbooks on coolers erroneously suggest the use of c v for similar regenerating steps. * This is a logic choice for general scaling considerations, but not always appropriate for realistic design considerations. Often, one or two dimensions are fixed due to fabrication constraints (for instance wafer thickness) and only one length or one area can be scaled. Sometimes also other parameters or assumptions that were taken constant in the analysis can be changed with scale. Because of that, these geometric scaling considerations should be used with great care in actual design considerations. Nevertheless, scaling analysis is very useful to obtain qualitative understanding of scaling behaviour. * Scaling per unit of volume is only mentioned if there is a physical meaning of this parameter. Gas-gap heat switch Chapter 5 This chapter discusses the operation of a gas-gap heat switch as well as the fabrication of a thin-film metal hydride layer that can be used to control the hydrogen pressure in the gas gap. First, the heat switch requirements are discussed, based on the design of the sorption compressor. Next, the theory of the heat transfer through the gas gap is described and verified experimentally. In section 5.4 hydrogen absorption by metal hydrides is discussed, a suitable metal hydride is selected, and the actuator behavior is modelled. Finally, the development and characterization is described of ZrNi thin films which are suitable for reversible hydrogen absorption. Miniature Linde-Hampson cold stage Chapter 8 This chapter presents the design and operation of two different miniature cold stages, both employing JT expansion. In section 8.2, a simple but elegant cold stage is discussed that is fabricated of miniature glass tubes. The more sophisticated cold stage presented in section 8.3 employs such glass tubes in combination with MEMS based silicon components, and is designed to be used with a sorption compressor.

This study presents a detailed technical assessment of the proposed Hyperion Transit System, an advanced magnetic levitation transportation network designed to achieve operational speeds of 600-800 km/h through integration of graphene-enhanced superconducting materials, sophisticated control systems, and renewable energy infrastructure. The analysis examines theoretical foundations, engineering challenges, economic viability, and implementation feasibility through rigorous mathematical modeling and experimental validation. Results indicate potential energy consumption reductions of 42% compared to high-speed rail systems and lifecycle carbon emissions of 38.2 g CO₂eq/passenger-km. However, significant technical hurdles remain, including large-scale superconductor manufacturing, cryogenic system reliability, and economic uncertainty. Cost projections range from $26.8-52.1 million per kilometer with a 17.3-year payback period under optimistic ridership scenarios. Critical analysis reveals Technology Readiness Levels ranging from TRL 3-6 for key components, indicating substantial development requirements before commercial viability. This assessment provides a balanced evaluation of the system's potential while highlighting the considerable challenges that must be overcome for successful implementation.

This paper presents a comprehensive study on the corrosion mechanisms affecting aluminum alloy cryogenic heat exchangers at the LNG complex GL1/Z and the associated maintenance and repair methodologies. Special emphasis is given to the types of corrosion, their metallurgical and operational causative factors, and the practical challenges in maintaining equipment integrity under severe cryogenic and chemical conditions. The paper further details in-line schematics and illustrative TikZ diagrams highlighting key corrosion and damage phenomena to support inspection planning and preventive strategies.

Abstract
The SERAPH-BLADE system represents a breakthrough in continental and hemispheric defense by addressing the long-standing physical limitations of ground-based Directed Energy Weapons (DEWs). Conventional DEWs are constrained by atmospheric thermal blooming, weather degradation, and horizon limits, making them inadequate against emerging threats such as hypersonic glide vehicles, hardened satellites, and maneuverable reentry systems. SERAPH-BLADE resolves these constraints through a novel vertical laser uplink architecture: a megawatt-class ground laser injects energy near-vertically into the atmosphere, minimizing distortion, before relaying the beam to a geostationary orbital platform. In orbit, precision optics, adaptive steering mirrors, and gimbaled telescopes condition and redirect the beam at speed-of-light response times to global targets.
The system is designed as a layered defense asset, integrating seamlessly with U.S. and allied missile defense networks, including THAAD, SM-6, and GMD, while adding a persistent orbital shield above midcourse and terminal defense arcs. Strategic targets include hypersonic missiles, ICBMs, anti-satellite weapons, drones, high-value terrestrial sites, and maritime threats. Engagement modeling shows that a constellation of three GEO platforms can provide near-global coverage, enabling rapid intercepts with sub-centimeter precision and one-second dwell times sufficient for burn-through effects.
Beyond performance, SERAPH-BLADE incorporates a sustainment and servicing architecture—pressurized docking enclosures, field-replaceable modules, and robotic or crewed maintenance access—ensuring a 10–20 year orbital life. Power options include high-efficiency solar arrays, thorium micro-reactors, and hybrid buffer systems, while hardened terrestrial bases are designed with bedrock anchoring, EMP shielding, and decoy deception to ensure survivability. Naval integration is also proposed, with Nimitz-class carriers repurposed as mobile uplink sites leveraging nuclear power and unlimited cooling capacity.
The program follows a phased execution plan: atmospheric/balloon prototypes and adaptive optics validation (Years 1–2), a GEO demonstrator with low-power beam handoff (Years 3–4), and full operational deployment of megawatt-class orbital relays (Years 5–7). Current technology readiness levels (TRL 7–9 for adaptive optics, HELIOS-class lasers, and satellite beam control) support an accelerated demonstration path.
Policy analysis concludes that SERAPH-BLADE can be legally advanced under the Outer Space Treaty if framed as a defensive orbital relay rather than an offensive weapon. A parallel diplomatic strategy is recommended to codify norms for defensive orbital beam systems.
In sum, SERAPH-BLADE is a scalable, modular, and survivable architecture that redefines space superiority by combining physics-driven design, near-term technical feasibility, and layered strategic integration. It provides the United States and allies with a persistent orbital shield—an unconquerable deterrent designed not for conquest, but for protection.

~ cryogenic system has been designed fo~ :;~i -1000 superconducting magnets associ-.: 1oith the proposed "energy-doubler" at the ,: .. ~JI Accelerator Laboratory. This paper ;:'on design parameters,cooling concepts, , 1 : :ransfer and pressure drops. Even though . :;~JI Jcsign changes are anticipated, the •" in this work is to complete a refrig-='. :ua design which would accomplish the ::nb necessary for the energy doubler mag-

The X-IFU is the cryogenic spectrometer onboard the future ATHENA X-ray observatory. It is based on a large array of TES microcalorimeters, which work in combination with a Cryogenic AntiCoincidence detector (CryoAC). This is necessary to reduce the particle background level thus enabling part of the mission science goals. Here we present the first joint test of X-IFU TES array and CryoAC Demonstration Models, performed in a FDM setup. We show that it is possible to operate properly both detectors, and we provide a preliminary demonstration of the anti-coincidence capability of the system achieved by the simultaneous detection of cosmic muons.

Austempered ductile iron (ADI) is widely employed in
applications that demand high strength, wear resistance,
and toughness, and its properties can be tailored through
controlled alloying and heat treatment. In this study, the
influence of varying copper content on the microstructure
and mechanical performance of ADI processed via
austempering, deep cryogenic treatment, and tempering
was investigated. Samples were categorized into three
groups: Group A (as-cast), Group B (austempered and
deep cryogenically treated at -196 C for 6 h), and Group
C (austempered, deep cryogenically treated at -196 C for
6 h, followed by tempering at 280 C for 2 h). The
austempering process involved heating samples to 900 C
for complete austenitization, quenching in a salt bath at
300 C, and holding for 2 h. Microstructure of the samples
were characterized using optical microscopy and X-ray
diffraction, while mechanical properties such as hardness,
impact toughness, and tribological performance were
evaluated. The results demonstrated that copper addition
significantly enhances hardness and wear resistance by
promoting the transformation of austenite into ausferrite.
Deep cryogenic treatment further facilitates martensitic
transformation, improving wear resistance by up to
15–20%. Although cryogenic treatment results in a modest
increase in hardness (2–3 HRC), subsequent tempering
slightly reduces hardness (1–5 HRC) but significantly
improves impact toughness by alleviating brittleness. These
results highlighted the critical role of copper alloying and
advanced thermal treatments in optimizing ADI’s
microstructure and mechanical performance for high-performance
applications.

This paper deals with the design, thermal and structural analysis for stopping the proton beam. A conical beam dump is being designed to handle the thermal and structural stresses resulting due to high heat load and hydraulic pressure of coolant, while handling 600 KW proton beam power in CW operation at 20 MeV energy. Pressure drop and heat transfer calculations are done considering spiral channel cooling system. The heat flux has been calculated by using Bi-Gaussian distribution density function of particles in beam. Nickel is selected as the beam dump material because of its favorable properties. In order to understand the thermal performance of beam dump a finite element model has been developed to predict the steady state temperature and stress distributions within the beam stop material.

Now a day with the rapid development in various developing countries, all over the world there is an increase in energy demand with each passing time .The problem of food crisis in most part of the developing countries takes place due to inability to preserve food surpluses rather than low production. This article is concentrated on the solar dryer and the experimentation of different samples (food stuffs).Drying is a process of removal of liquid by evaporation from the food stuffs like apples, grapes etc and other agricultural products. Mechanical methods for separating a liquid from a solid are not generally considered drying. In the following section an attempt is made to provide an overview of the solar dryer (prototype) for agricultural products.In our experiment average dryer efficiency for one day is found to be 13% for different samples while the moisture content for various samples like chilli, grapes and apples is found 64%, 58% and 60% respectively. All the readings are o...

This paper presents the results of an experimental investigation that has been carried out on uncoated carbide inserts of types TTR and TTS against C-40 job comparing with the untreated and deep-cryo-treated inserts. Experiments were carried out to evaluate the cutting forces and tool tip temperature under different machining conditions. Results indicated much improvements in cutting forces and tool tip temperature thereby increasing tool life and cutting performance in deep cryo-treated inserts. It has been observed that cutting forces increase/decrease with increase in cutting feed, depth of cut but decrease/increase with increase in cutting speed.

A crucial step in the mathematical modeling of a gas turbine engine is the characteristic map development of its main components, the compressor and the turbine. Maps can be obtained from manufacturers, although they are generally not available to the user. Furthermore, the construction of these maps through experiments is expensive. Analytical models prove to be economically more advantageous. Compared to other methods, they require little experimental data to be validated. These models are based on physical principles, so the results are more accurate compared to those obtained through numerical simulations or the use of neural networks. This approach allows more flexibility to make changes to the performance characteristics of engine components. These changes may be achieved by modifying certain geometric measurements, this quality could be used in diagnostic and/or engine control systems. In this work the characteristic map of the SR-30 turbojet engine components is analytically...

Joule-Thomson micro cryogenic coolers (MCCs) are a preferred approach for small, low-power cryocoolers. With the same heat lift, a MCC's power input can be as little as 1/10th of a thermoelectric cooler's input, and MCC's size can be as little as 1/10th of a Stirling cooler's size. With futuristic planar MCC and with high frequency MEMS compressors to be developed, its size can be reduced by another order of magnitude. Such -invisible‖ cryocoolers may revolutionize future IR imaging systems. We will review our studies on the feasibility of MCC with an emphasis on: (1) high thermal isolation levels reaching 89,000 K/W; (2) custom-designed gas mixtures with refrigeration capabilities increased by 10X and pressure ratio reduced to only 4:1; (3) compressors with low pressure ratios; and (4) excellent scalability for further size reduction.

Efficiencies of small 4 K cryocoolers are less than 1% of Carnot, whereas 80 K cryocoolers achieve efficiencies of up to almost 20% of Carnot. The primary loss mechanisms in low temperature regenerative cryocoolers are caused by the non-ideal gas properties of the He-4 working fluid and the reduced volumetric heat capacity of the regenerator matrix compared with that of He-4 at these low temperatures. A recently developed model, REGEN3.3, which incorporates the thermodynamic and transport properties of He-3, shows that using He-3 should improve the performance of 4 K regenerators considerably. REGEN3.3 was used to design an optimized test apparatus to measure the performance of a He-3, 4 K regenerator with the warm end precooled by a Gifford-McMahon cryocooler to about 35 K. The test regenerator is designed to operate at 30 Hz and uses a layered matrix of gadolinium oxysulphate (GOS) spheres at the cold end and erbium-praseodymium (ErPr) spheres at the warm end. The experimental test apparatus, testing procedures and the results are presented. In addition, a novel method to improve the phase shifting at the warm end of the small He-3 cold-stage pulse tube is described along with its impact on the cycle performance.

I have found memories of many visits to Japan that first began in 1970, only five years after the formation of the Cryogenic Association of Japan, which recently became the Cryogenics and Superconductivity Society of Japan. My first visit was to attend an IIR meeting in Tokyo and the 12th Low Temperature Physics Conference (LT12) in Kyoto. I was actively involved at that time with dilution refrigerators (DRs) and in the measurement of Kapitza thermal boundary resistance. DRs were very new then, having been invented in the Netherlands and England about five years earlier. At the conference I met many Japanese researchers involved in low temperature physics and cryogenic engineering. Many Japanese laboratories were also beginning work on the development of DRs to extend their research into the millikelvin temperature range. Some long-lasting friendships with Japanese colleagues began at that conference. In particular I want to acknowledge Prof. Nagano at the Solid State Physics

Some cryocooler applications, such as those for military operations dealing with high temperature superconducting (HTS) magnets, motors, or generators, require faster cooldown times than what can normally be provided with a cryocooler designed to accommodate a relatively small steadystate heat load. The current approach to achieve fast cooldown is to use a cryocooler oversized for steady-state operation. This paper proposes a new method applicable only to pulse tube cryocoolers that may decrease cooldown times by a factor of two or three when cooling to temperatures in the range of 50 K to 80 K from room temperature without increasing the size of the cryocooler. Such temperatures are appropriate for HTS magnets, generators, or motors. The proposed method makes use of the resonance phenomenon that occurs with an appropriately sized combination of inertance tube and reservoir volume. With a small reservoir, an LC resonance effect can occur at typical operating frequencies, with C being the compliance (volume) of the reservoir and inertance tube and L being the inertance of the inertance tube. At or near resonance the input acoustic impedance to the inertance tube is low, which allows for a high acoustic power flow at the cold end of the pulse tube for a given pressure amplitude. When the reservoir volume is increased to its normal size, the impedance increases to the value optimized for steady-state operation. A simple ball valve can then be used to change the reservoir volume and to switch from the fast cooldown mode to the steady-state mode. The higher acoustic power flow can be accommodated by the pulse tube and regenerator when they are at or near room temperature. In most cases the higher acoustic power in the fast cooldown mode does not require additional input power to the pressure oscillator because the load impedance is a closer match to that of the oscillator compared to that of the normal load during cooldown.

We describe a method for optimizing the design (shape of the displacer) of low-power Stirling cryocoolers relative to the power required to operate the systems. A variational calculation which includes static conduction, shuttle, and radiation losses, as well as regenerator inefficiency, has been completed for coolers operating in the 300 K to I0 K range. While the calculations apply to tapered displacer machines, comparison of the results with stepped-displacer cryocoolers indicates reasonable agreement.

Cryocooler performance and reliability are continually improving. Consequently, they are more and more frequently implemented by physicists in their laboratory experiments or for commercial and space applications. The five kinds of cryocoolers most commonly used to provide cryogenic temperatures for various applications are the Joule-Thomson, Brayton, Stirling, Gifford-McMahon, and pulse tube cryocoolers. Many advances in all types have occurred in the past 20 years that have allowed all of them to be used for a wide variety of applications. The present state of the art and on-going developments of these cryocoolers are reviewed in this paper. In the past five years new research on these cryocoolers has offered the potential to significantly improve them and make them suitable for even more applications. The general trend of this new cryocooler research is also presented.

Previously we have shown that the lower volumetric heat capacity and more ideal behavior of helium-3 compared with helium-4 at 4 K results in an improved performance for packed sphere regenerators operating with helium-3 between 4 K and 0 K. In this paper we use the NIST numerical software REGEN3.3 to calculate the regenerator loss and the coefficient of performance (COP) of 4 K regenerators with porosities between 0.1 and 0.38 for parallel holes in a rare-earth matrix operating at 30 Hz frequency using either helium-3 or helium-4. A comparison is made with packed spheres at a porosity of 0.38. Calculations were made for average pressures ranging from 0.3 MPa to 1.5 MPa, mostly with a pressure ratio of 1.5. The results show that the regenerator loss decreases and the COP increases as the porosity decreases for all average pressures. For helium-3 the regenerator performance is improved for pressures below 1 MPa, whereas the lower pressures do not benefit helium-4 regenerators. The COP of a helium-3 regenerator with 0.2 porosity operating at 30 Hz and 0.5 MPa average pressure is about 3.8 times higher than a helium-4 regenerator using packed spheres with 0.38 porosity. The effect of regenerator matrix material and the temperature of the heat capacity peak are also investigated.

Lightweight and compact microcoolers are needed for advanced, hand-held infrared systems. A temperature of 150 K is adequate for high sensitivity with some of the latest IR detectors, which simplifies the cooling requirements compared to 80 K detectors. The largest and heaviest component of most gas-cycle cryocoolers has been the compressor. This paper describes how the use of a 150 K, five-stage, cascade Joule-Thomson (JT) cycle significantly reduces the total refrigerant flow rate and total compressor swept volume compared with other types of cryocoolers for this temperature range. The use of vapor compression in each of the five stages results in very high specific refrigeration powers and low flow rates even with no recuperative heat exchangers and with pressure ratios of only about 4:1 Such low pressure ratios are needed for the use of chip-scale compressors. We discuss the thermodynamic design of a five-stage planar polyimide cold head for a range of refrigeration powers up to about 350 mW at 150 K. We compare the use of single-layer and double-layer construction over this range of refrigeration powers. In the double-layer construction, the high-pressure fluid streams are on the bottom and the low-pressure fluid streams are on top. Such construction allows for simple recuperative heat exchangers and leads to a compact planar geometry of about 20 mm by 30 mm for 350 mW refrigeration power at 150 K. The ideal fluid input power for the five-stage system at 150 K with no recuperative heat exchangers is 1.59 W per watt of net refrigeration power. For a heat exchanger ineffectiveness of 0.05 the specific power is 1.29 W/W for an efficiency of 89.2 % of Carnot with perfect compressors. The paper describes the geometry of the condensers, evaporators and Joule-Thomson impedances to achieve the high heat flux required for minimum size.

Abstract: This document contains the proceedings of the Third Cryocooler Conference, held at the National Bureau of Standards, Boulder, CO, on Sept. 17-18, 1984. About 140 people from 10 countries attended the conference and represented industry, government, and academia. A total of 26 papers were presented orally at the conference and all appear in written form in this document. The emphasis in this conference was on small cryocoolers in the temperature range of 4 - 80 K. Mechanical and non-mechanical types were discussed in the various papers. Applications of these small cryocoolers include the cooling of infrared detectors, cryopumps, small superconducting devices and magnets, and electronic devices.

A single-stage pulse tube cryocooler was designed to achieve 50 W of refrigeration power at 50 K when driven by a pressure oscillator that can produce up to 2.8 kW of acoustic power at 60 Hz. Initial experimental data produced no-load temperatures that were considerably higher than expected. Improvements were made to the warm end heat exchanger, aftercooler, and diffusionbonding of the copper screen matrix materials, which produce significant improvements to the lowend temperatures. The primary diagnostic tools utilized were four equidistant azimuthally spaced thermocouples located at the aftercooler exit and at the center planes of the regenerator component and the pulse tube component. The tools provided the information on the temperature distribution throughout the system and how the specific geometry changes throughout the pulse tube cryocooler would affect overall performance. This paper addresses the specific geometry changes to several major components of the cryocooler and their effect on the cryocooler performance. These include the transition piece from the inertance tube where the helium gas is entering and exiting the warm end heat exchanger and the pulse tube. Pulse tubes with various aspect ratios are tested to find the optimum aspect ratio. A major modification to the cold end heat exchanger matrix design will be implemented for more uniform gas flow through the diffusion bonded copper screen stacks. The effect of interspersing various amounts of copper screen along the stainless steel regenerator packing is also investigated.

This article describes an investigation of the transient behavior of a small (2.0 W at 85 K) pulse tube cryocooler operating at 120 Hz with an average pressure of 3.5 MPa, capable of relatively fast cool-down from ambient to about 60 K. In a series of experiments, the cold end temperature was measured as a function of time in a complete cool-down and subsequent warm-up cycle, with no heat load and different quantities of excess mass at the cold end. A transient heat transfer model was developed, that considers the effects of the cooling power extracted at the cold end and that of the heat gain at the warm end on the cool-down time. The heat gain factor was calculated from warm-up data, and found to be approximately the same for all experiments. Using the same model with cool-down data enables a determination of both the gross and net cooling power as functions of time, but more importantly -as functions of the cold end temperature. An expression was derived for the cold end temperature as a function of time for any amount of excess mass, including zero. The cool-down time of the ''lean'' cryocooler (with no excess mass) was found to be less than 50 s. This cool-down/warm-up method for evaluating the cooling power of a cryocooler seems simpler than steady-state experiments with a heater simulating load at the cold end. Use of the heat transfer model with data from one or two good experiments conducted in the above manner, can yield both the gross and net cooling powers of a cryocooler as functions of the cold end temperature, and allow the determination of cool-down time with any amount of excess thermal mass. While the net cooling power during cool-down differs somewhat from that under steady-state operation, the former can serve as a good measure for the latter.

A fundamental requirement of any spacecraft mechanism development is to demonstrate the integrity of the selected lubricant system by means of an appropriate life test. As mechanism lifetimes are often long, and development times compressed some form of accelerated test procedure may be required for programmatic reasons though the strict tribological validity of such tests both for fluid-lubricants and for mechanisms employing solid lubricants or self-lubricating bearing is often a point of concern. This paper discusses the current state of knowledge and limitations regarding accelerated testing, including the influences on lifetime, torque and material wear of the accelerated conditions. The uncertainties of presently available acceleration techniques and limitations of available data and methods are highlighted together with some potential future solutions.

The knowledge of a materials ability to safely sustain a load before breaking has been of paramount importance to man ever since structures were first built. The strength of material under tension has long been regarded as one of the most important characteristics required for design, production quality control and life prediction of industrial plant. In recent years advanced composite materials are increasingly used in almost every industrial branch and the components manufactured from these composite materials are usually subjected to complex loading that leads to multi-axial stresses and strain fields. A bi axial testing machine which describes the mechanical behavior of an isotropic sheet material is presented. Mechanisms controlling each other independently impose a tensile stress on a plus shaped cruciform. The sample design has been optimized to reach the highest possible isotropic biaxial strain field. The isotropic nature of fibrous materials has led us to develop an optica...

Herschel cryogenics instrument (HIFI, PACS, SPIRE) flight models have been delivered to ESA & Prime contractor Thales Alenia Space mid 2007, to be integrated and tested on the Herschel spacecraft, for a launch mid May 2009. The instrument integration and test campaign at spacecraft level was performed between mid 2007 and end 2008 in Astrium GmbH, Immenstadt (Gernany) and later in ESA's test facilities at Estec, Noordwijk (Nederland). The objective of these tests was to demonstrate full operability and performances of the instruments in spacecraft configuration, and their compatibility with the launch and space environment, while maintaining full compliance with the underlying requirements. A set of short functional tests were developed and used repeatedly to quickly check the health of each instrument at key points in the test campaign. Typically, this was after integration of a major component, prior to a major environmental test or before/after movement of the spacecraft. A set of full 1510

ESA has investigated the possibility to merge two of the next scientific missions of its HORIZON 2000 Programme, the fourth cornerstone mission, the Far InfraRed and Sub-millimetre Telescope (FIRST) and the third Medium-sized Mission M3, Planck (formerly Cobras/Samba). FIRST is a multi-user observatory, which targets the infrared and sub-millimetre part of the electromagnetic spectrum, covering approximately the wavelength range from 80 µm to 670 µm. The Planck mission is a survey mission dedicated to mapping the temperature anisotropies of the cosmic background radiation. The merging of the missions was studied in view of the programmatic constraints on both missions, the fact that they use a similar orbit (around the 2 nd Lagrangian libration point L 2 ), the partial parallel development of both missions and the potential cost savings. The decision taken during the ESA Science Programme Committee (SPC) meeting held end of May 98 is that the two missions will be implemented in the so-called "Carrier" solution. Both satellites will designed and launched together, and then will be separated. The cryogenic system of FIRST is based on a Superfluid Helium Dewar at 1.65 K (Infrared Space Observatory -ISO technology) with a design lifetime of more than 3 years. The very low temperature (0.3 K), required in the bolometer instrument will be obtained from a dedicated 3 He-sorption cooler. The cryogenic system of Planck uses a sequence of passive radiator (60 K), H 2 Joule-Thomson (JT) Sorption cooler (20 K), JT mechanical cooler (4 K), and dilution refrigerator (0.1 K).

ability to vary the pressure by varying the temperature, can also be used to design very efficient gas gap heat switches as shown further. The reliability requirement associated with the development of cryocoolers for space applications leads to the rule that a reliable cooler shall be simple, have no friction or better have no moving parts. CEA-SBT has acquired a large experience on both aspects and we present in this paper our past and current cryogenic sorption coolers activities. We will focus in this paper on the helium evaporative sorption coolers. It should be noted that CEA-SBT has also done some developments on the compressor aspects: two Joule Thomson cryocoolers capable of reaching respectively liquid helium and liquid nitrogen temperature were studied, which distinctive feature was the use of adsorption cryogenic thermal compressors (Refs. 1, 2). Adsorption coolers rely on the capability of porous materials to adsorb or release a gas when cyclically cooled or heated. Using this physical process one can design a compressor/pump which by managing the gas pressure in a closed system, can condense liquid at some appropriate location and then perform an evaporative pumping on the liquid bath to reduce its temperature.

Raja Ramanna Centre for Advanced Technology (RRCAT) has developed a 2K vertical Test Stand (VTS) facility for characterization of Superconducting RF (SCRF) cavities, under Indian Institution Fermilab Collaboration (IIFC). The VTS facility comprises of a large size liquid helium (LHe) cryostat, cryogenic system, RF power supply, control and data acquisition system and radiation monitoring system. It will facilitate testing of superconducting cavities of different frequencies ranging from 325 MHz low beta to 650 MHz / 1.3 GHz medium and high beta cavities. The helium vessel has a capacity to store up to 2900 litres of liquid Helium. The cryostat is installed inside a vertical pit. It is equipped with facilities for supply of liquid nitrogen and liquid helium and vacuum system for pumping out helium gas to lower the temperature of liquid helium bath down to 1.8 K. A 200 W, 1.3 GHz RF system has been indigenously developed for testing of the SCRF cavities. The VTS facility has now been ...

This paper proposes a novel architecture for building a large-scale, fault-tolerant quantum computer in outer space. Current quantum computing technologies are limited by cooling challenges, noise, radiation, and scalability. We suggest the design of a Quantum Space Station that leverages the natural cold environment of space (2.7 K) as a pre-cooling layer. The system integrates deionized water for thermal buffering, advanced cryogenic cooling to milliKelvin levels, radiation shielding, and vibration isolation. Ground-based classical control units transmit operations to the space-based processor, and results are returned via optical communication links. This architecture could enable the realization of a million logical qubit quantum computer, which is beyond the feasible capacity of terrestrial cooling systems.

The Small Punch technique is a miniature test used mostly for irradiated materials or when the test material is scarcel y available. The main aim of small specimen mechanics is to figure out the mechanical behavior with a great reduction or small volume of material. This document emphasizes the development of correlations between mechanical characteristics determined from small punch tests and uniaxial tensile tests. Recommended techniques for specimen design, specimen preparation, experimental design, experimental implementation, and data analysis are used according to ASTM SPT 888. The test involves bending the disk symmetrically about the center, producing a simple, axisymmetric stress state. First, the right conditions were simulated via Finite Element Analysis and then stress and deformation analysis were done for all the specimens, and the results were obtained. These equations are applied to all the copper alloys at a temperature of 295 K. The equations can be used to determine the uniaxial tensile stress-strain behavior of copper and its alloys.

Linear gas stopping cells have been used successfully at NSCL to slow down ions produced by projectile fragmentation from the 100 MeV/u to the keV energy range. These 'stopped beams' have first been used for low-energy high precision experiments and more recently for NSCLs re-accelerator ReA. A gas-filled reverse cyclotron is currently under construction by the NSCL to complement the existing stopping cells: Due to its extended stopping length, efficient stopping and fast extraction is expected even for light and mediummass ions, which are difficult to thermalize in linear gas cells. The device is based on a 2.6 T maximum-field cyclotron-type magnet to confine the injected beam while it is slowed down in ≈100 mbar of LN 2 -temperature helium gas. Once thermalized, the beam will be transported to the center of the device by a traveling-wave RF-carpet system, extracted along the symmetry axis with an ion conveyor and miniature RF-carpets, and accelerated to a few tens of keV of energy for delivery to the users.

The dc and ac performance of advanced SiGe:C heterojunction bipolar transistors (HBTs) featuring transit frequency (f T ) and maximum oscillation frequency (f max ) of 300 and 500 GHz was characterized from 298 K down to 4.3 K. At 4.3 K, the transit frequency f T increases by 65% from measured 317 GHz (at 298 K) to 525 GHz. The increase of f T starts to saturate below 73 K. The physical reasons for the temperature variation of the experimental characteristics and simple model extensions for improving existing compact models (CMs) are discussed so that they can be used for estimating circuit design results at cryogenic temperatures (CTs). The model extensions are verified using experimental data. To the best of our knowledge, this is the first demonstration of modeling advanced SiGe:C HBTs for such a wide temperature range from deep cryogenic to room temperature (RT) (4.3-298 K). INDEX TERMS Compact modeling, cryogenic modeling, cutoff frequency, heterojunction bipolar transistor (HBT), HIgh CUrrent Model (HICUM), quantum computing, SiGe, transfer characteristics.

The construction of the new Spiral 2 facility has started in Caen (France) at the National Heavy Ions Accelerator Center (GANIL). The SPIRAL 2 project is based on a multi-beam Superconducting Linac Driver delivering 5 mA deuterons up to 40 MeV and 1 mA heavy ions up to 14.5 MeV/u delivering different Radioactive Isotope Beams (RIB). The LINAC is composed of 2 cryomodule families. The low energy family (cryomodules A) is composed of 12 cryomodules housing a single superconducting cavity at beta=0.07. The "high" energy family (cryomodules B) is composed of 7 cryomodules housing 2 cavities at beta=0.12. In between cryomodules are located the focalisation quadrupoles and the diagnostic boxes. Their multiplication may lead to cavity pollution. Strong believes forbid the use of interceptives diagnostics around superconducting cavities. We simulated the use of wires for diagnostics in the linac, sublimating 14 wires of tungsten, niobium and carbon while operating the cavity B at full performances. The results describe in this paper looks promising.

QUBIC, the QU Bolometric Interferometer for Cosmology, is a novel forthcoming instrument to measure the B-mode polarization anisotropy of the Cosmic Microwave Background. The detection of the B-mode signal will be extremely challenging; QUBIC has been designed to address this with a novel approach, namely bolometric interferometry. The receiver cryostat is exceptionally large and cools complex optical and detector stages to 40 K, 4 K, 1 K and 350 mK using two pulse tube coolers, a novel 4 He sorption cooler and a double-stage 3 He/ 4 He sorption cooler. We discuss the thermal and mechanical design of the cryostat, modelling and thermal analysis, and laboratory cryogenic testing.

Resistance thermometers based on Ge films on GaAs substrates have been developed, manufactured, and studied. The thermometers have a miniature package (diameter 1.2 mm and thickness 0.9 mm) and are designed to operate in various temperature ranges from 1.5 to 300 K, 70 to 400 K, and 200 to 500 K. The manufacturing technology, design, low-temperature conductivity, and behavior of the thermometers in a magnetic field are presented. At low temperatures, the conduction of thermometers is variable-range hopping (VRH) with exponents x of 0.25 and 0.45 for different models. Low-temperature transverse magnetoresistance can be positive or negative depending on the manufacturing conditions of the Ge films. Positive magnetoresistance is large and observed in the presence of VRH conductance with an exponent of 0.25, while negative magnetoresistance can be observed in VRH conductance with an exponent of 0.45 and a magnetic field of 0-3 T. Thermometers designed to operate at high temperatures exhibit two-dimensional percolate transport. The temperature dependence of resistance is described by an exponential dependence with activation energy close to E g /2. Such Ge thermometers can be used up to 500 K.

Composite Overwrapped Pressure Vessels (COPVs) are widely used in fields including aeronautics and by companies such as SpaceX to hold high pressure fluids. They are favored for these applications because they are far lighter than all-metal vessels, although they demand special design, manufacturing, and testing requirements. In this study, finite element modeling was used to conducted stress and damage assessments on a composite overwrapped pressure vessel that has a 4 mm thick aluminum core cylinder. To develop the optimum COPV, the lamina sequences, thickness, and fiber winding angle were considered. The relationship between these variables and the composite-overwrapped structure’s maximum burst pressure bearing capacity was assessed. The ABAQUS composite modeler was used to design and generate 14 models of COPVs from carbon fiber/epoxy plies with a consistent thickness of 6.5 mm and various fiber angle orientations. The effects of the ply stacking order were analyzed by the fini...

This paper describes the development of an alternative technology for vehicular storage of hydrogen. Insulated pressure vessels are cryogenic-capable pressure vessels that can accept cryogenic liquid fuel, cryogenic compressed gas or compressed gas at ambient temperature. Insulated pressure vessels offer advantages over alternative hydrogen storage technologies. Insulated pressure vessels are more compact and less expensive than compressed hydrogen vessels. They have lower evaporative losses and lower energy requirement for fuel liquefaction than liquid hydrogen tanks, and they are lighter than hydrides. The work described in this paper is directed at verifying that insulated pressure vessels can be used safely for vehicular hydrogen storage. The paper describes multiple tests and analyses that have been conducted to evaluate the safety of insulated pressure vessels. Insulated pressure vessels have been subjected to multiple DOT, ISO and SAE certification tests, and the vessels have always been successful in meeting the passing criteria for the different tests. A draft procedure for insulated pressure vessel certification has been generated to assist in a future commercialization of this technology. Ongoing work includes the demonstration of this technology in a vehicle.

In this paper a new method for the electromagnetic modeling of superconductors is presented. It combines the Partial Element Equivalent Circuit methodology for inductance and resistance, with a Floating Random Walk method for modeling capacitive coupling. The method is totally aligned with the physics of superconductivity and is able to account for phenomena such as kinetic inductance and the Meissner effect. The accuracy of the method is demonstrated with comparisons against previously published reference data.We also present preliminary results on the efficiency and the capacity of this method.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

The Jet Propulsion Laboratory (JPL) is currently developing the Low Temperature Microgravity Physics Experiments Facility (LTMPEF), a multiple user and multiple flight facility that will provide a long duration low temperature environment on board the International Space Station. The LTMPEF will be attached to the Japanese Experiment Module (KIBO) Exposed Facility of the International Space Station with an initial flight starting in late 2005. The LTMPF is a self contained, reusable, cryogenic facility containing a 180-liter superfluid helium tank, two experiment packages, and electronics to provide experiment control and telemetry. Two distinct primary experiments will be accommodated during each mission, and secondary experiments requiring no additional hardware beyond that built for the primary experiments will also be accommodated during each mission. Detailed technical capabilities of the Facility will be presented, along with a brief description of the six science investigations currently selected to fly on the first two missions. TABLE OF CONTENTS 1. INTRODUCTION 2. DESCRIPTION 3. DEVELOPMENT 4. OPERATION 5. SCIENCE EXPERIMENTS 6. STATUS AND CONCLUSIONS