Cold Mass Design Research Articles

Numerical Assessment of the Inhomogeneous Temperature Field and the Quality of Heat Extraction of Nb3Sn Impregnated Magnets for the High Luminosity Upgrade of the LHC

The High Luminosity upgrade of the Large Hadron Collider (HL-LHC) at CERN foresees the installation of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn-based quadrupole magnets at selected interaction points of the accelerator. The precise knowledge of each magnet's thermal characteristics and heat extraction performance in response to power depositions during both nominal and ultimate conditions is essential in determining safe operating margins. A 2D numerical framework has been developed to systematically assess the temperature distribution in the combined magnet structure-superfluid He system of each magnet and enveloping cold mass using open-source software. Here a full cross-section of a magnet cold mass is modelled, under the power density distribution expected at the most exposed longitudinal position during accelerator operation at an instantaneous luminosity of 5.0x10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">34</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , corresponding to the nominal conditions for HL-LHC. Temperature maps and margins are presented for the inner triplet magnets (MQXF) for both horizontal and vertical beam crossing conditions, along with the validation of the design of cold mass cooling channels for heat extraction.

Mechanical Design and Analysis of the Baby-IAXO Magnet Cold Mass, Cryostat and Support System

According to the so-called Primakoff effect, axions and axion-like particles can transform into photons in the presence of a strong magnetic field. To continue the search for these hypothetical particles, a new helioscope called the International Axion Observatory IAXO, and its subscale but fully functional demonstrator Baby-IAXO, are being designed. To increase the detector's sensitivity by a factor of 10 compared to the present CAST helioscope, the experiment needs a stronger magnetic field and in a much larger volume. The superconducting magnet of Baby-IAXO features two 10 m long flat racetrack coils spaced by 0.8 m, arranged in a common coil configuration and generating an average magnetic field of 2.1 T in the two 700 mm detection bores positioned in between the coils. The cold mass structure based on using mainly Al6061-T651, is designed to guarantee pre-stress of the coils during curing and sustain the magnetic loads by the Lorentz force. At ultimate current of 12 kA, the repelling force between the two coils is 33 MN. Furthermore, the supporting structure has to keep the coils in position as they are in an unstable equilibrium in the plane parallel to the racetracks. To support the cold mass in the cryostat, an arrangement of rods was chosen in order to minimize the cryogenic load. The system is composed of 16 titanium rods, which in addition to supporting the expected force loads also keeps the magnet centered. The total mass of the magnet is 35 t comprising an 18 t cold mass and a 15 t cryostat. The magnet is installed on an elevated 360° rotating platform further constraining the cryostat design. Here the mechanical design of cold mass, cold mass supporting system and cryostat of the Baby-IAXO magnet are presented.

Superconductor and Cold Mass Design of the 2 T Solenoid for the PANDA Detector at FAIR

The PANDA experiment at the Facility for Anti-proton and Ion Research (FAIR) in Darmstadt, Germany, relies on a superconducting solenoid surrounding the interaction point. The magnet is designed to provide a magnetic field of 2 T over a length of about 4 m in a bore of 1.9 m. The main technical challenges are related to the need of relatively tight magnetic field uniformity (±2%) over the tracker region and to insert a warm target feed pipe transversely to the solenoid axis. To meet the given requirements while balancing the magnetic forces, the magnet is split in three interconnected coil modules. Starting from the baseline design detailed to some extent in the Technical Design Report (TDR), the conductor and cold mass layouts have been thoroughly reassessed in the last two years to increase conductor stability and to simplify coil winding and cold mass assembly, as well as cost efficiency. In this paper, the main features and updates of the conductor, cold mass design, and assembly are reviewed.

Cylindrical boiloff calorimeters for testing of thermal insulation systems

Cryostats have been developed and standardized for laboratory testing of thermal insulation systems in a cylindrical configuration. Boiloff calorimetry is the measurement principle for determining the effective thermal conductivity (ke) and heat flux (q) of a test specimen at a fixed environmental condition (boundary temperatures, cold vacuum pressure, and residual gas composition). Through its heat of vaporization, liquid nitrogen serves as the energy meter, but the design is adaptable for various cryogens. The main instrument, Cryostat-100, is thermally guarded and directly measures absolute thermal performance. A cold mass assembly and all fluid and instrumentation feedthroughs are suspended from a lid of the vacuum canister; and a custom lifting mechanism allows the assembly and specimen to be manipulated easily. Each of three chambers is filled and vented through a single feedthrough for minimum overall heat leakage. The cold mass design precludes direct, solid-conduction heat transfer (other than through the vessel's outer wall itself) from one liquid volume to another, which is critical for achieving very low heat measurements. The cryostat system design details and test methods are discussed, as well as results for select thermal insulation materials. Additional cylindrical boiloff calorimeters and progress toward a liquid hydrogen apparatus are also discussed.

Design of Cold Mass Supports for a Superconducting Undulator Prototype at SINAP

A superconducting undulator (SCU) prototype with a period of 16 mm and a magnetic gap of 8 mm has been under design and fabrication at the Shanghai Institute of Applied Physics in China since late 2013. The SCU prototype is aimed at obtaining the magnetic field of 0.88 T at the beam axis. A set of support systems was designed to support the cold masses, including superconducting coils, a beam chamber, and thermal shields. A set of self-centering cold mass supports are adopted for the superconducting magnet for the purpose of self-alignment at low temperature. The beam chamber is supported by G-10 spacers against the magnet. The nonmetallic tension rods and spacers are used to support the 60- and 20-K thermal shields, respectively. The heat loads conducted to the cold masses through the supports need to be minimized. This paper presents the design details of the support system.

Structural Analyses of the Cold Mass for High Field Dusty Plasma Experiment

A magnet to study the properties of dusty plasmas in the presence of a magnetic field has been proposed. This magnet has four operating modes to vary the experimental test region and target magnetic field values. The design of the cold mass for the high field magnetized dusty plasma experiment is presented and analyzed. The cold mass includes four coils, ground insulation covering the winding packs, and coil cases used to safely support the coils. Dimensions of the four coils are specified by the magnetic design, and the equipment used to view the dusty plasma apply spatial constraints to the cold mass design. The design also considers the manufacturing process for the cold mass and the stresses resulting from electromagnetic loads coupled with thermal loads. Only one operating mode is considered in this analysis as the others produce significantly lower electromagnetic forces. Resulting stresses compare favorably to failure criteria at critical locations.

Cold Mass Design of the Superconducting Outsert for the 40-T Hybrid Magnet

A 40-T hybrid magnet is under construction at the High Magnetic Field Laboratory, Hefei Institutes of Physical Science, Chinese Academy of Sciences (CHMFL), Hefei, China. It includes a superconducting outsert magnet that can provide a central field of 11 T and a warm bore of Ø 800 mm for the insertion of a water-cooled magnet. This superconducting magnet has three superconducting coils, all of which are wound with Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn cable-in-conduit conductors (CICCs). The structural design of the superconducting outsert's cold mass has been worked out starting from the design of the conductors and the configuration of the coils. In this paper, we present the considerations and designs for the major components of the cold mass, i.e., the winding pack, the preload structure, the CICC lead support structures, and the cooling circuit. In addition, the design of the support structure of the coils is introduced and discussed. This is a key element and a special component with the function to support the cold mass and to transfer the fault loads from the coils to the base plate of the cryostat while its heat load to the cryogenic side remains as low as possible.

The Final Design of the R3B-GLAD Cold Mass Assembly and Manufacturing Status

The R3B-GLAD (GSI Large Acceptance superconducting Dipole) magnet provides the magnetic field needed for the R3B (Reaction studies with Radioactive Relativistic Beams) experiment which will be implemented on the future FAIR Facility (Facility for Antiproton and Ion Research). There are six trapezoidal racetrack coils for the R3B-GLAD magnet. Two main coils and four lateral coils are connected in series in a butterfly-like shape. The total weight of the six coils is 5.2 t. The cold mass assembly consists of coils, coil-casings, structural linking components and other non-structural components. The cold mass assembly weighs 22 t with envelope dimensions of 3.1 m (L) × 4.6 m (W) × 2.8 m (H). It is supported by the three cold to warm cryogenic supports. The magnet configuration was finalized in June 2008. The final cold mass design was accomplished end of July 2008. The manufacturing of the cold mass assembly has been launched since January 2009. The cold mass will be ready for test in the test station at CEA Saclay by the end of 2010. This paper gives an overview on the final design of the R3BGLAD cold mass assembly and manufacturing status.

The Design and Construction of the MICE Spectrometer Solenoids

The purpose of the MICE spectrometer solenoid is to provide a uniform field for a scintillating fiber tracker. The uniform field is produced by a long center coil and two short end coils. Together, they produce 4T field with a uniformity of better than 1% over a detector region of 1000 mm long and 300 mm in diameter. Throughout most of the detector region, the field uniformity is better than 0.3%. In addition to the uniform field coils, we have two match coils. These two coils can be independently adjusted to match uniform field region to the focusing coil field. The coil package length is 2544 mm. We present the spectrometer solenoid cold mass design, the powering and quench protection circuits, and the cryogenic cooling system based on using three cryocoolers with re-condensers.

Thermal analysis of the superconducting outsert of the NHMFL 45-T hybrid magnet system

Thermal analyses of the NHMFL 45-T hybrid magnet system reported includethree aspects important for magnet design and operation: 1) cooldown of the superconducting outsert from ambient to operating temperature; 2) reaction of the cryogenic system to the quench in the magnet and the resulting requirements to the cold mass design; 3) calculation of AC losses during the charge of the superconducting outsert.

Status of the SSC superconducting magnet program

The Superconducting Super Collider (SSC) is a proposed proton-proton collider designated to achieve collisions with 20 TeV per beam. In the SSC, protons are accelerated and stored in two storage rings that are stacked one on top of the other in an underground tunnel 83 km in circumference. In each collider ring the protons are kept in a roughly elliptical orbit by two types of magnets: dipoles, which bend the proton orbit into a closed loop, and quadrupoles, which deflect the protons back toward the central orbit when they diverge from it. Both types of magnets use high-current superconducting coils to meet the SSC design requirements. A dipole field of 6.6 T was chosen as a compromise between the need for the highest practical field and the limits of superconducting technology. The author reviews the work done on the SSC dipole. Topics discussed are cable development and production, cryostat design, cold mass design, and model magnet testing. >