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This paper presents effects of lithium (Li) and magnesium (Mg) dopants on the dielectric properties of ZnO ceramics with emphasis on ferroelectricity prospects of co-doped samples with Zn0.7Li0.28Mg0.02O compositions. Ceramics with average relative density ∼97% were produced by solid-state-reaction of mechanically activated powder precursors using 1000 °C for 2 h sintering conditions. Room temperature A.C. conductivity σ a . c ( ω ) and temperature-frequency (T-ω) dependence of dielectric permittivity ( e ′ ) and loss ( e ″ ) of the samples are measured within temperature range from −100 to 150 °C in air and in a vacuum cryostat with liquid nitrogen coolant. Undoped ZnO σ a . c ( ω ) data exhibits a nearly insensitive dependence to the ω while that of doped samples show significant ω dependence and higher σ a . c ( ω ) values than undoped ZnO ceramics. Anomalous e ′ and e ″ peaks were observed in Zn0.7Li0.28Mg0.02O specimens around TC of −25 °C during cooling and −10 °C during heating measurements in air. However, dielectric properties of the same Zn0.7Li0.28Mg0.02O ceramics obtained in vacuum cryostat and from undoped ZnO ceramics in air and in vacuum cryostat did not reveal any e ′ and e ″ transition peaks at low temperature.

The DEMO tokamak architecture is based on large vertical breeding blanket (BB) segments that are accessed from a maintenance hall above the tokamak and are vertically replaced through large upper ports of the vacuum vessel (VV). The feasibility of the BB segments mechanical supports is a prerequisite of this vertical segment architecture. Their design directly impacts on the removal kinematics and the remote handling operations required for release and engagement. The supports must withstand large forces acting on the BB in particular due to electromagnetic (EM) loads. At the same time, they must ensure a sufficiently precise positioning of the BB first wall. Their design also takes into account the significant thermal expansion of the blanket segments that are operated at high temperature avoiding excessive support reaction forces. The BB support concept described in this article does not require fasteners or electrical straps to the VV and therefore much reduces the complexity of the BB remote replacement – a valuable characteristic that would make this concept a milestone in meeting one of the goals defined for the DEMO project: to develop a maintainable fusion power plant design [1]. Each blanket segment is individually supported by the VV without any physical contact to the other blankets or in-vessel components. It relies instead on vertical pre-compression inside the VV due to obstructed thermal expansion and radial pre-compression due to the ferromagnetic force acting on the BB material in the toroidal magnetic field. The verification process did not identify show stoppers. Nonetheless, a further evolution of the concept is required including design improvements to mitigate the high stress levels found in the inboard blankets during plasma disruptions. The fact that no excessively high support reaction forces or large BB deflections were found suggests though that the further development of the concept could be successful.

Helium has the lowest boiling point of any element in nature at normal atmospheric pressure. Therefore, any unwanted substance like impurities present in liquid helium will be frozen and will be in solid form. Even if these solid impurities can be easily eliminated by filtering, liquid helium may contain a non negligible quantity of molecular hydrogen. These traces of molecular hydrogen are the cause of a known problem worldwide: the blocking of fine capillary tubes used as flow resistors in helium evaporation cryostats to achieve temperatures below 4.2 K. This problem seriously affects a wide range of cryogenic equipment used in low temperature physics research and leads to a dramatic loss of time and costs due to the high price of helium. Here, we present first the measurement of molecular hydrogen content in helium gas. Three measures to decrease this molecular hydrogen are afterward proposed; (i) improving the helium quality, (ii) release of helium gas in the atmosphere during purge time for the regeneration cycle of the helium liquefier’s internal purifier, and (iii) installation of two catalytic converters in a closed helium circuit. These actions have eliminated all blockages of capillaries at low temperatures now for more than two years.

We present the precision calibration of 35 Hamamatsu R11410-22 photomultiplier tubes (PMTs) with xenon scintillation light centred near 175 nm. This particular PMT variant was developed specifically for the LUX-ZEPLIN (LZ) dark matter experiment. A room-temperature xenon scintillation cell coupled to a vacuum cryostat was used to study the full-face PMT response at both room and low temperature $\textrm{($\sim$ -100$^\circ$C)}$, in particular to determine the quantum efficiency (QE) and double photoelectron emission (DPE) probability in LZ operating conditions. For our sample with an average QE of $\textrm{(32.4$\pm$2.9)%}$ at room temperature, we find a relative improvement of $\textrm{(17.9$\pm$5.2)%}$ upon cooling (where uncertainty values refer to the sample standard deviation). The mean DPE probability in response to single vacuum ultraviolet (VUV) photons is $\textrm{(22.6$\pm$2.0)%}$ at low temperature; the DPE increase relative to room temperature, measured here for the first time, was $\textrm{(12.2$\pm$3.9)%}$. Evidence of a small triple photoelectron emission probability $\textrm{($\sim$0.6%)}$ has also been observed. Useful correlations are established between these parameters and the QE as measured by the manufacturer. The single VUV photon response is also measured for one ETEL D730/9829QB, a PMT with a more standard bialkali photocathode used in the ZEPLIN-III experiment, for which we obtained a cold DPE fraction of $\textrm{(9.1$\pm$0.1)%}$. Hence, we confirm that this effect is not restricted to the low-temperature bialkali photocathode technology employed by Hamamatsu. This highlights the importance of considering this phenomenon in the interpretation of data from liquid xenon scintillation and electroluminescence detectors, and from many other optical measurements in this wavelength region., Comment: 13 pages, 16 figures

The AKARI satellite (formerly known as ASTRO-F) is Japan’s first infrared astronomical satellite. AKARI is equipped with the infrared camera (IRC) and the far-infrared surveyor (FIS), which are cooled below 7 K. The AKARI’s 68.5 cm telescope, which is made of SiC, is also cooled below 7 K. A unique feature of the AKARI cryostat is that it uses both cryogen and mechanical coolers. Using mechanical coolers, the helium lifetime can be greater than one year with 170 L of liquid helium. AKARI was launched on February 21, 2006 (UT), from the Uchinoura Space Center (USC). It has been performing successfully in orbit.

This chapter discusses high-temperature superconducting (HTS) transformers with an emphasis on the technical and cost barriers they must surmount to supplant conventional transformers in the power grid. Requirements for conventional transformers with respect to short circuit current limitation, overload capacity, electrical insulation, voltage regulation, efficiency, and mitigation of fire hazards are reviewed since these constrain the operation of HTS transformers. Salient features of HTS conductors and cryogenic operations and the status and achievements of HTS transformer development worldwide are reviewed. AC loss in HTS transformer windings is considered, especially the use of multiple conductors to attain high currents using transposition at the coil level or as continuously transposed cable. Cryostat and cryocooler technology and progress on achieving transformer performance goals, especially relating to fault current performance and conductor loss, are reviewed. The economic viability of HTS transformers is reviewed from the viewpoint of total cost of ownership.

In ITER, so-called “Irregular” Field Joints (IFJs) are foreseen at the interface between irregular sectors of the Vacuum Vessel (VV), which is located inside the cryostat and houses the in-vessel components. In the IFJs, a peculiar design of the equatorial port, with respect to that adopted in the Regular Field Joints (RFJs), accommodates the irregularities of the adjacent VV sectors. The IFJs are subject to nuclear heating and actively cooled by sub-cooled pressurized water flowing in a dedicated hydraulic loop, which includes the space left open by the borated In-Wall Shielding (IWS). Here we perform the 3D steady state thermal-hydraulic analysis of two different IFJs using the Computational Fluid Dynamics (CFD) software ANSYS-FLUENT®. The water flow field, the pressure drop and the temperature maps are computed. The thermal performance of the IFJs in nominal operation is compared to that of an RFJ and it is shown that also in this case enough cooling capability is available to avoid hot spots above the design limits, while the pressure drop remains acceptably low.

The EURECA (European Underground Rare Event Calorimeter Array) project is aimed at searching for dark matter particles using cryogenic bolometers. The proponents of the present project have decided to pool their strengths and expertise to build a facility to house up to 1000 kg of detectors, EURECA, consisting in the first instance of germanium and CaWO4 crystals. The shielding will be provided through a large water tank in which the cryostat with detectors will be immersed. The EURECA infrastructure will be an essential tool for the community interested in using cryogenic detectors for dark matter searches. Beyond European detectors, it will be designed to host other types of similar cryogenic detectors, requiring millikelvin operating temperatures. In particular, this includes the germanium detectors currently in use by the SuperCDMS team, following the current collaborative work performed by the EURECA and SuperCDMS collaborations. EURECA will have two stages. The first phase aims at a sensitivity of 3 10-10pb and will involve building the infrastructure, cryostat and shielding, and operating 150kg of detectors. The second phase will be completed with 850kg of additional detectors, the relative weight between the different detectors being decided by the collaboration according to the physics reach. A sensitivity of 2.10-11 pb is aimed for atthe second stage. EURECA will ideally benefit from the planned extension of the deepest underground laboratory in Europe - LSM. With a site-independent design, it can also be hosted in other locations at similar or deeper sites such as SNOLAB. © 2014 The Authors.

We have developed a new 50-cm infrared balloon-borne telescope. The first flight of this telescope system is scheduled for September 1998. We used an offset paraboloidal mirror and used its primary focus to reduce the amount of background emission from the telescope itself in order to perform photometric observation with high sensitivity. The structure of the telescope is made of carbon fiber reinforced plastics (CFRP) to reduce its weight and make the optics free from thermal contraction due to low temperatures during observational flights to retain good focusing of the optics. For the detector, we use our newly developed 4 × 8 stressed Ge:Ga array in order to perform 150–180 μm photometry. The detector is installed in a cryostat and cooled by liquid He down to 2 K. The large format of the detector raises the observational efficiency enabling us to survey a wide area of the sky (up to 10° × 10°) with a high spatial resolution of 1.5′ in one observational flight. In the first flight, we plan to survey the Orion region, W51, etc. and to map some external galaxies.

This is an overview of cryogenics in relation to the advances in superconducting engineering and technology. This chapter will discuss the fundamentals of a cryogenics system and its requirements for HTS, wet and dry system cooling methods, cryogenics issues with cooling sources, heat sources and measurement, cryostat construction, practical thermometry in dry/cryogen-free systems, development and applications using cryogenics and HTS, and associated challenges.

Within the European Fusion Technology Programme, the Helium-Cooled Lithium Lead (HCLL) breeding blanket concept is one of the two EU lines to be developed for a long term fusion reactor, in particular with the aim of manufacturing a test blanket module (TBM) to be implemented in ITER. The HCLL-TBM is foreseen to be located in an ITER equatorial port, being housed inside a steel-supporting frame, actively cooled by pressurized water. This supporting frame has been designed to house two different TBMs providing two cavities separated by a dividing plate 20 cm thick. As the nuclear response of HCLL-TBM could vary with the supporting frame configuration and composition, a parametric study has been launched to investigate such an influence. Previous works dealt with the dependence of the nuclear response of HCLL-TBM on the configuration of an homogeneous frame while the present one has been focussed on the investigation of the influence of coolant distribution within the frame. A detailed parametric study of HCLL-TBM nuclear response has been performed by means of 3D-Monte Carlo neutronic and photonic analyses, simulating the frame in a semi-heterogeneous way. Three-dimensional heterogeneous models of HCLL-TBM and of the supporting frame have been set-up considering both the usual poloidal lay-out and a toroidal one and taking into account 9% Cr martensitic steel (EUROFER) as structural material. The models have been inserted into an existing 3D semi-heterogeneous ITER-FEAT one, simulating realistically the reactor lay-out up to the cryostat and providing for a proper D-T neutron source. The analyses have been performed by means of the MCNP-4C code, running a large number of histories (2·108) in such a way that results obtained are affected by statistical uncertainties lower than 1%. The results obtained are reported and critically discussed.

GeMPI, a highly sensitive germanium gamma-spectrometer operated at the Gran Sasso underground laboratory is described. Its complete cryostat system and shield was made from highly selected low activity materials. Radon suppression, also during sample insertion is achieved by an air-lock system combined with an airtight steel casing around the shield, which is pressurised with nitrogen gas. The achieved background level in combination with a large sample capacity of up to 15 l around the 2.2-kg Ge crystal allows measuring concentrations of the gamma-active chain members down to 10−12 g/g of U/Th equivalent (12.3 μBq/kg 238U, 4.06 μBq/kg 232Th) and 10−9 g/g of K (31 μBq/kg 40K). This is demonstrated with some key measurements of Cu and Pb shielding materials. Cosmogenic production rates for 8 radioisotopes have been determined in exposed Cu to range from 50 μBq/kg for 46Sc to 2.1 mBq/kg for 60Co. A possible further background reduction in Ge-spectrometry by operating naked crystals in liquid nitrogen is discussed.

Publisher Summary This chapter reports on developing the basic technology for the HTS transformer, and presents the results of individual tests of the HTS transformer. A three-phase 26kVA (400 V/16 V) HTS transformer, cooled by liquid nitrogen, for the analysis of its fundamental characteristics has been developed. The primary and secondary windings are wound by transposed conductors, which are made from the stainless steel-reinforced multifilamentary Bi2223/Ag tapes fabricated by American superconductor (AmSC). The main aims are improvements in basic technology for application of HTS transformers by analyzing the characteristics of electro-magnetism, insulation, thermodynamics, and stability for the transformer. The structures of primary and secondary windings are solenoid and double-pancake respectively. Fundamental characteristics of the transformer are obtained through no-load and short circuit tests. The gas-cooled current leads of secondary windings are optimally designed. The cryostats are made from electrical insulating materials fiberglass reinforced plastics (FRP), which have excellent heat-preservation. The iron cores are made of common scratched Fe-Si steel and operate at room temperature. The rated primary and secondary voltages are 400V and 16V, and rated currents are 37.5A and 938A respectively. The transformation ratio is 25, short circuit impedance is 2.8%, and the excited current is 1.26%.

Publisher Summary This chapter investigates the working of a new type of cryostat system applying boil-off calorimetry method. The power cable system consists of termination cryostats, high temperature superconducting (HTS) power cable and their cooling system. The current lead located in the termination cryostat is used to transmit the power from the room temperature power cable to the low temperature HTS power cable. Because the current lead is the major heat source of cooling load, the heat load of the current lead has influence of the liquid nitrogen consumption and the refrigeration capacity. For this reason, the design of current lead with smaller heat load is very crucial for the economic refrigeration system. One of the main characteristics of the system is to avoid gas convection cooling effect. A prototype current lead inserted in the system was made of copper. Heat loads through the copper current lead were measured for four different heat load conditions. The experimental results coincide with the numerical ones within 3% error.

Publisher Summary This chapter discusses the design feature of the EAST and its kW/4K cryogenic system. EAST is a Chinese National Project designed to develop scientific and technological basis on the steady state operation of advanced tokamak. The EAST superconducting tokamak is a full superconducting device, which consists of superconducting toroidal field (TF) and poloidal field (PF) magnets, vacuum vessel and in vessel components, thermal shields, and cryostat. The cooled components are TF magnets, PF magnets, support structure, and thermal shields. Dimensions of the EAST device are 10 m (with the main support) in height and 7.6m in diameter. Its total weight is 360 tons. Up to now the device fabrication is going on smoothly, all part of SC Magnet, Cryostat, Vacuum Vessel, and Thermal Shield will be completed this year. One CS coil and 10 of TF coil has been tested, the results show that all of the magnets can meet the design requirement.

Publisher Summary This chapter presents the recent developments performed in Europe in the field of cryocoolers. New markets such as high temperature superconductors applications and space applications are requiring new cooling performances, efficiency, and high reliability for future cryocoolers . New emerging technologies such as flexure bearings and Pulse Tube have demonstrated potentially interesting capabilities for future generations of cryocoolers. New performances and reliability requirements for future HTS devices or space missions have simulated the development of new technologies. European academic institutions and industrial partners have initiated developments of different cryocooler technologies covering a large range of cooling power and cooling temperatures. Commercial products are already proposed by the industry and several demonstrators have demonstrated their performances and potential capability to be shortly industrialized. Challenging developments are also performed for future space missions. GM cryocoolers are essentially integrated in vacuum cryopumps and MRI cryostats. Compact Stifling cryocoolers are widely used in infrared detection modules mostly for military night vision optical systems. JT expansion cryocoolers in open cycles, fed with high pressure gas storage bottles, are mainly integrated in single shoot missile guidance infrared systems. 4K GM cryocoolers, GM type PTC, and dilution fridges are common cooling solutions in experimental devices for physicists in Research Laboratories.

Publisher Summary This chapter describes the focusing solenoid for the proposed Muon Ionization Cooling Experiment (MICE). The nominal design configuration for MICE calls for the focusing solenoids to be operated in the gradient mode, with two coils each carrying 2.01 MA while operating at opposite polarities. When the MICE focus coils are operated in the gradient mode, a large inter-coil force is developed in the direction to push the two coils apart along the magnet axis. This force must be carried by a cold aluminum structure between the two coils. There are configurations of the experiment that call for the two focusing coils to operate at the same polarity. When the magnet operates in the solenoid mode, the inter-coil force pushes the two coils together along the magnet axis. The two coils, which have separate leads, may be operated in the same polarity or at opposite polarity. This report discusses the superconducting magnet design and the cryostat design for the MICE focusing module. Also discussed is how this superconducting magnet can be integrated with a pair of small 4.2 K coolers.

Publisher Summary This chapter validates FE thermal models of the support members for the low temperature components of the Herschel Space Observatory by measurements at 1.8K. The Herschel Space Observatory structure is briefly introduced. The thermal modeling of two designs of support member is discussed and the final designs presented. The cooling of these instruments is to be achieved by placing the optical bench inside a large cryostat which contains a superfluid helium tank at 1.6 K and uses a circulation loop to deliver the superfluid helium to the bench. Conductance is calculated from the heater power divided by the temperature difference observed across the samples, in units of W/K. The design of the validation test rig is described together with details of the experimental method. Observed results are presented and discussed with reference to the thermal model. The model is found to be valid to within 1.5×10-5 W/K in the lateral struts and 3.29×10-5 W/K in the interface struts, at a mean temperature of 6K.

Publisher Summary This chapter describes the development of cryogenic thermal conductivity measurement system, a DC and an AC RRR measurement techniques for niobium quality control. The thermal conductivity, RRR distribution, and microstructure of electron beam welding niobium are investigated, and their correlation is observed by experiments. For controlling niobium properties for the fabrication of superconducting cavity, the systems for quick measurement of Nb thermal conductivity and residual resistivity ratio RRR are created. Thermal conductivity test can be done in a 100 1 transport liquid helium tank. An innovative cryogenic thermal conductivity measurement system based on transport liquid helium cryostat is described. Thermal conductivity distribution of electron beam welding sample is investigated. Below 3K, the thermal conductivities dependence on grain sizes is observed. Thermal break down is one of the main limitations on the way to high gradient superconducting cavity. To avoid thermal break down, high thermal conductivity of niobium is needed.

Publisher Summary The LHC sector helium relief system is designed to recover a simultaneous resistive transition of a magnet sector (sector quench) without releasing helium in the atmosphere. This chapter reviews safety, operational and mechanical aspects of helium relief system added to the Large Hadron Collider (LHC). A simultaneous resistive transition of a LHC magnet sector, which may occasionally occur, will cause rapid helium outflow from magnet cryostats to a special relief system composed of long pipes, buffer volumes, and accessories. The cold buffer constituted by header D can retain up to 46 % of the helium discharged from the magnets. The stresses in quench line (QL) and vent line (VL) pipe wall material have been calculated and they will not exceed 120 MPa. This value is twice lower than the yield strength of the applied material (240 MPa). To fulfill safety requirements, there is also a possibility to discharge the helium from header D via the safety valve (SV) or two bursting disks (BD) and further through the VL, which directly opens to the environment. A set of SV and two BD constitute the connection between header D and the VL. The PV, SV, and BD are located at the cryogenic distribution line (QRL) extremities.

Publisher Summary This chapter investigates the formation and propagation of a normal zone in a 38 turn Bi-2223 pancake coil operating between 35K and 60K. A cryostat for thermal stability and quench propagation studies of HTS pancake coils has been constructed with an operating temperature range between 35K and 65K. The transient thermal response of a test coil to an applied energy pulse has been measured and the minimum energy needed to initiate a quench is presented as a function of temperature and heater length. The formation and propagation of a well defined normal zone has been observed in a HTS coil. The maximum temperature of the initial normal zone (TQ) has been shown to be well below the critical temperature Tc of the superconductor. The lower normal zone temperature TQ

Publisher Summary This chapter presents the tests of a series of He II porous plug liquid-vapor phase separators for bath temperature at 1.5–1.9K. At zero gravity, superfluid helium (He II) liquid–vapor phase separator (LVPS) is a key device that keeps the liquid phase separated from the vapor for He II cryostat, which is used to cool space superconducting component and far infrared detectors of astronomical observation instruments. Based on a fundamental of thermo mechanical (fountain) effect in restricted geometries, helium II is retained in the tank by LVPS. Boil-off helium gas flows through LVPS and cools the He II tank. For one separator, two regions (initial region and hysteresis loop) are observed in the relationship between mass flow rate and temperature (or pressure) difference. For two separators with similar parameters, the repeatability of experimental data can be observed. To prepare theoretical analysis of the separator, the data of cold vapor flow rate is obtained when the He II liquid level is below the porous plug. The repeatability of the flow characteristic through the similar porous plugs can therefore be proven.

Publisher Summary This chapter investigates experimental study cavitation phenomena in both He I and He II flows through the pressure and temperature measurements and the application of optical visualization. The cavitation flow is generated in the downstream region of a Venturi channel driven by contracting the metal bellows. The cavitating flows can be observed through the optical windows of the cryostat. Tests were carried out for both He II and He I. The pressure loss and the temperature drop caused by cavitation are measured in a wide range of the flow velocity. The spatial distribution of the cavitation bubble velocity is also measured by the application of PIV (Particle Image Velocimetry) technique. It is seen that there is a difference in the magnitude of the pressure loss between He I and He II. In the case of He II, the data are almost independent of the temperature, but in the case of He I, temperature dependency is clearly recognized.

Publisher Summary This chapter describes the preliminary design of a cryogenic system of the superconducting (SC) solenoid magnet, including the heat load estimation, the cooling flow scheme, the operation modes, the structural design of the pipes, control dewar, and cryostat of this SC solenoid magnet. The cryogenic system consists of a refrigerator, compressor, buffer tank, recovery tank, liquid nitrogen storage tank, control dewar and SC solenoid magnet, where the refrigerator, compressor, buffer tank, and recovery tank are shared with another superconduting user of Beijing Electron Positron Collider II (BEPC II), a pair of superconducting interaction region quadrupole magnets (SCQ). The solenoid magnet is indirectly cooled by forced, two-phased helium flow during steady state operation and switched to a thermo-syphon mode in case of emergency stop of the refrigerator. The design of the cryogenic system of the superconducting solenoid magnet of BESIII has been done. In this design, the heat load of the whole system has been estimated, the cooling flow scheme and the operation modes determined, and the structural design of the pipes, control dewar and cryostat accomplished.

Publisher Summary Development and detail engineering of the main components of the plasma vessel thermal insulation and the interfaces to adjacent port tubes is finished and production is starting. The chosen MLI system is crinkled Kapton® foils with vapor-deposited aluminium on both sides, and with glass paper as spacers in between. The actively cooled thermal shield consists of epoxy-glass resin panels which contain three copper mesh layers each for sufficient thermal conductivity. The cryostat thermal insulation of the stellarator Wendelstein 7-X (W7-X) is being built by MAN DWE and its main sub-contractor Linde AG. The complex geometry and narrow gaps to the superconducting coils require innovative solutions concerning the multi-layer insulation (MLI) as well as the shield and its supports. The surface facing the coils is covered by adhesive Al-foil to reduce emissivity. Each shield panel is supported by one firm support near the center and several “loose” supports which allow in-plane gliding for thermal contraction compensation. The shield supports consist of Torlon® tubes. They are bolted to the PV, and at the cold ends the panels are clamped between two disks. Each panel is cooled by two cooling pipes which are thermally contacted via flexible copper braids.

Publisher Summary The Spitzer Space Telescope, comprised of the Cryogenic Telescope Assembly (CTA) and the Spacecraft, is operating in an Earth-trailing, solar orbit where the influences of the Earth and Moon on the thermal system performance are negligible. It consists of four subsystems: the 360-liter superfluid helium cryostat; the multiple instrument chamber that is mounted on the helium tank; the bet/Ilium telescope that is mounted and heat sunk to the cryostat vacuum shell; and the outer shell group. The CTA is attached to the Spacecraft with composite supports and miniature electrical cables to control the conducted heat to the telescope and cryostat to a very low level. Shields block radiation from the warm Spacecraft bus and solar panel, which prevent sunlight on any CTA surface at all times. To reject heat the outer shell anti-sun side is coated with black paint which has high emittance at low temperature. Inside the outer shell the outer vaporcooled shield (VCS) surrounds the telescope and cryostat. The Spitzer Space Telescope (formerly called SIRTF) was launched into an Earth-trailing, solar orbit on August 25, 2003. The Cryogenic Telescope Assembly is Spitzer's instrument payload. The design operational lifetime is 5 years, limited by the loss rate from the superfluid helium cryostat that cools the instruments to 1.3 K and the telescope to 5.5 K by vapor cooling.

Publisher Summary This chapter describes an optical cryostat used for fabricating inertial confinement fusion (ICF) cryogenic target. In the ICF technology, one key is to produce a cryogenic target with an evenly distributed liquid fuel layer inside it. Utilizing thermal gradient vertically crossing the target to overcome the gravity is an effective method. The manufactures of this kind of cryogenic target call for a cryostat of a special design, which must satisfy some requirements. First, it can provide a low-temperature environment within 10–40 K. Second, it must hold a target cell, in which an ICF target can be loaded. Third, it must possess a temperature control system that can be utilized to create a desired thermal gradient vertically crossing the target cell. Fourth, it must have optical windows. The cryostat holds a target cell. With the temperature control system, a desired thermal gradient vertically crossing the cell can be formed. The specifications of the optical cryostat are presented.

Publisher Summary The Laser Megajoule facility is the French equipment intended for studies of inertial fusion. Thermonuclear fusion is obtained by focusing 240 laser beams with an energy of 1.8 MJ on a cryotarget. The microballoon implosion, following laser beams impact, generates in its center the ignition conditions of temperature and pressure. The success of implosion strongly depends on the geometrical characteristics of the Deuterium Tritium ice layer: margin 1% for thickness, 1 μm for roughness. The Laser Megajoule requires a high resolution temperature regulation to obtain the cryotarget temperature conditions: a temperature slope of 1 mK/min with ±1 mK to reach the triple point 19.79 K and a regulation at constant temperature with ±1 mK. This regulation required a thermal model elaboration for the target and the process, a regulation module development with a ±50 μK resolution, and a specific algorithm of regulation. It runs on the prototype “Echelle 1,” the Cryotarget Positioner mock-up built at the Service des Basses Temperatures—CEA Grenoble. The temperature stability obtained on the cryostat “Echelle 1” is presented in the chapter.

Publisher Summary Cutting good sections on a cryostat can be the most frustrating part of any in situ hybridization (ISH) protocol. The chapter describeso essential features of a cryostat and general advice on troubleshooting. For cryostat sectioning it is important to avoid water-crystal formation in the tissue when the tissue is frozen. For this liquid nitrogen or dry ice can be used, although dry ice is preferable because with liquid nitrogen the brain cracks easily. It is important to keep the original shape of the brain when freezing to allow easy identification of the anatomical structures. Once completely frozen, the brain can be sectioned directly, after equilibrating to the cryostat-chamber temperature, or stored at −80°C. When kept at −80°C, it is important to prevent dehydration of the brain by covering it with parafilm to form an airtight parcel and then putting it into a tightly closed container. A desiccated brain will give sections that crumble.. The chapter presents some common problems and solutions.

Cryocrystallography, defined as cold crystallography, has been in existence almost as long as crystallography has been there. Early experiments used sealed cryostats, which were essentially dewars with beryllium walls transparent to the scattered X-rays. This method is still used for experiments that must be performed below liquid nitrogen temperatures, 77 K. Later experiments used chillers to cool air to as low as 200 K; however, problems associated with dehumidifying the air and removing carbon dioxide set this as a lower practical limit. One manufacturer has introduced a chiller using room temperature air as input to cool below liquid nitrogen temperatures. Modern cryocrystallography is the general methodology by which the crystal of interest is placed into a protective solution and frozen with minimal damage, resulting in data collection at cryogenic temperatures. Cold, but not solid state, crystallography has a number of special advantages. These include the reduction of thermal motion in the crystal, the ability to slow down enzymatic reactions, and the ability to continually diffuse in fresh substrate to enzymes in crystals.

Publisher Summary This chapter presents an historical overview of high pressure in semiconductor physics. There are two major contributions to the development of apparatus in the post-Bridgman era, which have led to considerable expansion of activity in the field. The first is the introduction of strong, flexible, high-pressure tubing to separate a massive pressure-generating system from the final experimental vessel—which may be at the exit of a spectrometer, between the poles of a magnet, or settled deep in the interior of a cryostat. The second is the advent of the compact diamond anvil cell, which avoids the storage of large energies in compressed fluids. Raman scattering has also been used extensively to map out certain portions of the phase diagram. The pressure dependence of all Raman-active zone-center phonons has been determined as 11 GPa at ambient temperature. Information about zone-edge modes is also found from second- and third-order scattering processes.

Publisher Summary Multilayer insulation (MLI) is a highly effective cryogenic insulation, used in cryogenic systems. The design of MLI insulated cryogenic containers for liquid helium, uses the refrigeration of the outgoing vapor to cool the radiation shields, since the ratio of enthalpy of helium vapor to its latent heat is quite high. The design of liquid helium containers uses both the highly efficient MLI along with vapor cooled shields attached to the neck tube. This chapter describes the demountable liquid helium cryostat of 100 liter capacity to carryout optimization studies on the number of vapor cooled shields, their positions on the neck tube and the number of MLI layers interposed between them. A Kapton film seal between the neck tube and the top dished end provides demount ability between the inner vessel and flanged vacuum jacket. The cryostat is instrumented for measuring temperature profiles of neck tube and the insulation layers. The chapter also discusses the heat transfer analysis for a typical case.

Publisher Summary This chapter helps in designing, building and testing a system for experiments with the 1.3 GHz superconducting cavity. The major part of the system is a horizontal cryostat which includes a helium vessel for the cavity, He-gas and LN2-cooled shields, two nodes for RF couplers, a device for mechanical stretching or squeezing the cavity and a control system. Cooling down to 2.0 K and below is performed with saturated superfluid helium pumped by 500 1/s unit. Operation experience collected up to date is discussed in the chapter. The feature of the control system is the usage of 16 channels cold multiplexer to measure temperatures within the liquid helium vessel. Its components are tested for the radiation environment performance. The obtained results are presented for the various dose values. In the environment combining gamma and neutron radiations and cryogenic temperatures, up to the total doses of approximately 10,000 Gy and 3·l013n/cm2, correspondingly, the cold multiplexer based on the HCMOS PC74HC/4067 chips, can be used successfully. To define these boundaries more exactly, further explorations are needed.

Publisher Summary Japan Atomic Energy Research Institute is studying a thermal shield in a cryostat, whose diameter is 36m and height is 34m, for International Thermonuclear Experimental Reactor(ITER). In ITER, superconducting coils, such as Toroidal Field (TF) coils and Poloidal field (PF) coils are used and the total weight is around 25,000 tones. The thermal shield is cooled by 80-K helium gas. The designed radiation heat leak from room temperature to 4-K superconducting coil and the structure is less than 0.24 W/m2 by using a multi-layer metal plate. Total heat load of thermal shield is 147 kW at 80K. The thermal shield is a segment structure in order to allow a maintenance and replacement by remote handling system. The thermal shields are designed to meet the heat load and cooling condition requirements. Additionally, they are designed to be maintained using remote handling techniques.

Publisher Summary This chapter presents a two stage analytical tool developed to calculate the thermomechanical cooldown behavior of long thin structures cooled from a pipe. The first stage analysis of transient thermal behavior of long thin structures cooled from pipe has proved to simulate accurately the behavior of this type of structure in the CTM, and therefore it is to be used for the design of the thermal shields for the next generation of cryostats. Measurements are to be carried out to corroborate the mechanical part of the model. The second stage calculates displacements of the shield structure due to internal temperature differences. Analytical temperature estimates are compared to measurements performed on the Cryostat Thermal Model (CTM). The most stringent cooldown for the 15 m LHC cryomagnets can take place on the test bench. The thermal shield has to be cooled from room temperature to around 75 K in 15 hours.

Publisher Summary In NMR experiments at very low temperatures, the two points are important––there must be a good thermal contact between a sample and the cryostat. Since thermal contact resistance between two cold bodies increases rapidly as the temperature falls, it becomes increasingly important how to transfer heat from one place to another, and there must be little or no eddy current heating by applied rf pulses. In the presences of some metals, eddy current heating occurs when applying rf pulses in the NMR experiment. Therefore it is advantageous to make cryostat by non-metal substances and to immerse samples directly into cold fluid. In this way good thermal contact between the samples and the fluid is achieved.. This chapter helps in constructing a vortex refrigerator especially designed for NMR measurements around I K. The main parts of the refrigerator have been made by non-metal substances to reduce eddy current heating due to applied rf pulses. The sufficient cooling power for continuous measurements has been obtained. The mutual friction between superfluid component and normal fluid component in He II is also discussed.

Publisher Summary This chapter describes a basic cryostat design for the magnet that is supposed to be 1200 mm in diameter and 1500 mm in height. The total weight of the magnet is 8 tons. The magnet has a peculiarity in its superconducting joints; inner Nb3Sn coils have superconducting joints 400 mm above the upper surface of the coils. It points out problems to be solved for the superfluid helium cryogenic system for an NMR spectrometer. The amount of cryogen in the magnet vessel is designed to be less than 100 L, which ensures cryostat insurance in the case of a magnet quench. Safety of the cryostat involving a magnet with a huge stored energy of 50 MJ has been checked. Precooling of the magnet in the restricted space is a remaining problem. The estimated consumption rate of 708 cc/hr for liquid helium allows the monthly supply system by one 500 L helium Dewar. There still remain other problems to be solved. Precooling of the eight-ton magnet can take more than three weeks. Magnet charging takes a few days. In all processes, including normal operation mode, the cooling system operate automatically and stably. This chapter continues the cryostat design and research and development works to obtain design data.

Publisher Summary Engineering applications of superfluid helium (HeII) has been focused on by cryophysical and cryogenic researcher after the superconducting magnet has been successfully cooled by superfluid helium, several kinds of subcooled superfluid helium cryostat have been successively developed. This chapter discusses the influence of various types of pressures (bath pressure, hydrostatic head, Van-derwaals pressure and fountain pressure) on the heat transfer in a bath of HeII. If the bath pressure is less than λ-Pressure (P λ), special peak heat flux density relations are shown to correlate bath pressure, hydrostatic head and modified pressure items (Van-der-waals pressure and fountain pressure). If the bath pressure is greater than λ –pressure (P>P λ), a generalized formula of peak flux density of pressurized superfluid (HeIIp) bath is addressed in the chapter.

Publisher Summary This chapter discusses the designs and manufacturing of centrifugal cold compressor for TEVATRON lower temperature upgrade. In 1994, Fermilab completed to grade up the refrigeration system including capable of lowering two-phase temperature down to 3.5K with the satellite refrigerators equipped with cold compressors. The apparatus to depressurize liquid helium by directly inhaling evaporated gas and lower its temperature is the cold compressor. In cold compressor the shaft is supported by the dynamic gas bearings in the complete oilfree structure. The motor is air-cooled by a fan to eliminate possible trouble in the cooling water system and to get better maintenance. The cold compressors for Tevatron have been confirmed their reliability for a long operation and become practical machines that can be operated in great numbers at the same time. However, the cryostat vibration must be solved.

Publisher Summary The muon spectrometer of the ATLAS general-purpose pp detector is based on the configuration of large superconducting air-cored toroids and consists of a long barrel toroid (BT) and two inserted End Cap Toroids (ECT's) to generate the large field and strong bending power required. ATLAS Experiment proposed for the Large Hadron Collider uses a toroidal magnet system to achieve high efficiency muon momentum resolution. The End Cap Toroids (ECT's) are designed to provide bending powers in the range 4-8 Tesla-meters over the rapidity span 1.5-2.8 in the important forward or backward regions. Each ECT may have an outer diameter of approximately 11 meters, a length of 5 meters and a weight of 190 tones. They each may have eight separate coils and a single integral radiation shield which can all be contained in a common cryostat.

Publisher Summary This chapter conducts a systematic research to find and compare the heat transfer patterns of superconductor in different coolant baths. It focuses on the influence of the insulation layer of superconductor on heat transfer. A systematic research on NbTi/Cu wires (single core and multi-filaments) has been conducted in HeI, HeIIs, and (pressurized superfluid) HeIIp, separately. The results measured in three baths show a large difference in current sharing zone of a same sample, but a similar wire with insulation layer in HeII baths gives the results like those of bare wire in HeI. It means the insulation of superconductor is the main obstacle of heat transfer. In order to complete the measurement in a small cryostat avoiding destroying sample, a prediction based on the pre-test at room temperature is performed to provide the maximum of resistance and voltage of sample, which makes the measurement high efficient and more reliable.

Publisher Summary The Large Helical Device (LHD) has been being under construction at National Institute for Fusion Science (NIFS) at the Toki site in Gifu prefecture. Due to its size superconducting magnets of LHD need large refrigeration system. As the magnets and the large cryostat for the magnets are still under design or construction, heat load and heat load distribution might be changed from the figures. In order to estimate the plant condition in such cases, the plant performance at off-design condition has to be simulated. Performance at off-design conditions of a large scale helium refrigerator is estimated by the simulation model that has been developed for a study of a standard helium liquefier. The process simulation model is based on characteristics of hardware such as heat exchangers and expansion turbines. Required input data to the simulation model are process variables that can be fixed or controlled. Simulation results of the large refrigerator for LHD, which has 7 expansion turbines and 15 heat exchangers, agree with the data observed at the commissioning. As an extreme off-design condition, performance without 3 upper expansion turbines is studied.

Publisher Summary The ATLAS barrel toroid is a superconducting magnet assembly of eight independent coils supported by a warm mechanical structure. It operates at an average temperature of 4.5 K. This temperature is obtained by a two-phase helium circulation. The vapor quality in the coils is controlled around 10 %. Helium is provided by cryogenic pumps, which deliver a 600 g/s mass flow rate, through a cryogenic ring. This ring supplies helium to all the coils, all the shields at an average temperature of 60 K and contains the bus bar to power the magnet. It is connected to the coils in their central part. The ring is connected to a power cryostat which includes the 20 000 A current leads. This connection is located in the low and straight section between the ring and the main valve box. This part is called main cryogenic line. After a 30 days cool-down, the running mode is based on two 600 g/s cryogenic pumps. The first one delivers this nominal mass flow of subcooled liquid helium and the second one runs slowly in case of default on the running one. In order to avoid a fast dump of the magnet, the rapid commutation of the pumps is necessary.

Publisher Summary The International Thermonuclear Experimental Reactor diagnostic system consists of about 40 individual measurement systems to control and evaluate the ignited plasmas. These measurement systems involve magnetics, neutronics, laser and optical systems, X-Ray to visible spectroscopy, microwaves, probes, pressure gauges and thermocouples. Components are located in several different locations: at main ports, in the vacuum vessel, inside and outside the cryostat, and in buildings. Each area poses its own set of design requirements on the equipment. Although the equipment in the vertical port varies, a standard hole is provided for the plugs of diagnostic equipment required to be installed in the penetrations. Diagnostic sensors, such as magnetic pick-up coils, bolometer cameras, retroreflectors, and antennas are installed in the blanket modules. The modules also require instrumentation, such as thermocouples and strain gauges. Several modules are modified with holes or enlarged edge gaps for diagnostic purposes, although as much use as possible is made of the 20mm gap which exists between modules for installation purposes.

In the framework of the Tore Supra upgrade, one of the final main purpose of the experimental programme is to inject up to 25 MW during up to 1000 seconds and to investigate associated physics and technology issues. Among the latter, development and use of high heat flux components is a central subject, the investigation of which requires a good knowledge of the energy deposition in all parts of the tokamak. Owing to its enclosure into a cryostat, Tore Supra inner vessel and plasma facing components permit precise calorimetric measurements.

Publisher Summary The Satellite Test of the Equivalence Principle (STEP)-satellite is a candidate for ESA's next medium size scientific mission (M3). On STEP the fundamental physical law of the universality of free fall of anybody shall be checked up to an accuracy of 1 into 1017. Squids are foreseen to measure the relative motions of different test mass pairs in an absolute zero-g environment provided by a drag-free satellite control system. Any liquid movement in the required He-cryostat must therefore be avoided. The combination of a supercritical main cryostat with a superfluid shield under equal pressure offers the possibility to meet this requirement due to the avoidance of free liquid surfaces. With an actively cooled Cryostat Vacuum Vessel and equipped with a radiator a hybrid SCHeMe IIcryostat can be realized which provides the necessary quiet environment at < 2 K for the scientific payload of STEP while fulfilling stringent mass and volume requirements and providing a lifetime of over 6 months with 20 % margin.

Publisher Summary A large scale helium refrigeration system was constructed and operated for about 7 years for superconducting RF accelerating cavities (SCC) in TRISTAN electron positron collider at National Laboratory for High Energy Physics (KEK). The 32 x 5 cell 508 MHz SCC in 16 cryostats were installed in TRISTAN electron-positron collider at KEK for further upgrading of the beam energy, from 27 GeV to 32 GeV. This chapter provides a short description of the main components of the cryogenic system together with the operating experience gained during the commissioning and 7 years operation. The total number of failures in the cryogenic system during about 7 year's operation was 85. The experience in long operation of the large cryogenic system shows the compressor is the key component and the regular maintenance of the system including utilities is essential to attain the system reliability.

Publisher Summary The tokamak HT-7 is a reconstructed device from the tokamak T-7. It has the same major radius of 122cm and minor radius of 35cm, but HT-7 has much more and larger ports for heating and diagnosing plasma. In order to add 26 new larger ports the toroidal magnet (TM) is rearranged to a symmetry distribution of 24 two-double-pancake windings, and the plasma chamber, coil cases, 80K shields and cryostat shell has to be modified or rebuilt, so that the heat load at 4.6K zone increases to 130W. The superconducting toroidal magnet of tokamak HT-7 consists of 48 double pancake coils and is cooled with supercritical or two-phase helium flow. The cryogenic system is equipped with two 500W/4.5K refrigerators. During the engineering tests of tokamak the cryogenic system backed up the magnet running at the toroidal field of 1.2-1.5T for a month in 1995. After the problem of helium leak in the cryostat has solved the device can be operated at toroidal fields of 1.6-2.0 T steadily. A plasma current of 140kA amplitude and 1.3s pulse duration was achieved in March 1996.