G. Rolando

Design of a 56-GJ Twin Solenoid and Dipoles Detector Magnet System for the Future Circular Collider

An aggressive low-mass and high-stress design of a very large detector magnet assembly for the Future Circular Collider (FCC-hh), consisting of a “twin solenoid” and two dipoles, is presented. The twin solenoid features two concentric solenoids. The inner solenoid provides 6 T over a free bore of 12 m and a length of 20 m, enclosing the inner particle trackers and electron and hadron calorimeters. The outer solenoid reduces the stray field of the inner solenoid and provides additional bending power for high-quality muon tracking. Dipoles are included, providing 10 T · m of bending power in a 6-m mean free bore covering the forward directions for η ≥ 2.5 particles. The overall length of this magnet assembly is 43 m. The presence of several separate magnets in the system presents a challenge in terms of forces and torques acting between them. A rigid support structure, part of the cold mass, holds the inner and outer solenoids of the twin solenoid in place. The dipoles are equipped with lateral coils so that the net force and torque are reduced to zero. The second challenge is the substantial conductor and support structure mass used for containing the magnetic pressure. A doped aluminum stabilized and reinforced conductor is proposed, allowing minimal overall mass of the system. The result is a system consisting of a 53-GJ twin solenoid and two 1.5-GJ dipoles. The cold mass and the vacuum vessel mass of the twin solenoid are 3.2 and 2.4 kt, respectively; and the dipole cold mass weighs 0.38 kt. Various properties of the magnet system are discussed such as magnetic, mechanical and thermal properties, quench behavior, and assembly.

Minimum quench power dissipation and current non-uniformity in international thermonuclear experimental reactor type NbTi cable-in-conduit conductor samples under direct current conditions

The level of current non-uniformity in NbTi cable-in-conduit conductors (CICCs) sections near the joints in combination with the magnetic field profile needs attention in view of proper joint design. The strand joule power and current distribution at quench under DC conditions of two samples of ITER poloidal field coil conductors, as tested in the SULTAN facility, and of the so called PFCI model coil insert, have been analyzed with the numerical cable model JackPot. The precise trajectories of all individual strands, joint design, cabling configuration, spatial distribution of the magnetic field, sample geometry, and experimentally determined interstrand resistance distributions have been taken into account. Although unable to predict the quench point due to the lack of a thermal-hydraulic routine, the model allows to assess the instantaneous strand power at quench and its local distribution in the cable once the quench conditions in terms of current and temperature are experimentally known. The analysis points out the relation of the above mentioned factors with the DC quench stability of both short samples and coils. The possible small scale and local electrical-thermal interactions were ignored in order to examine the relevance of such effects in the overall prediction of the CICC performance. The electromagnetic code shows an excellent quantitative predictive potential for CICC transport properties, excluding any freedom for matching the results. The influence of the local thermal effects in the modeling is identified as being marginal and far less than the generally accepted temperature margin for safe operation.

Electromechanical Design of a 16-T CCT Twin-Aperture Dipole for FCC

Canted-cosine-theta (CCT) technology has been studied for its suitability for a future-circular-collider (FCC) main dipole in terms of magnetic and mechanical performance, electrothermal protectability, as well as efficiency. In this paper, we present lessons learnt from our search for efficient CCT solutions by means of two-dimensional (2-D) magnetic and mechanical simulations, discuss the 3-D periodic mechanical model, as well as 3-D electromagnetic analysis of the end regions. Temperature and voltage distributions during a quench under simplifying assumptions are discussed, and the magnets efficiency is compared to that of other contenders in the FCC design study. The results qualify the CCT design as a contender for the FCC main dipole.

New and Optimized Magnetization Scheme for the Baby Magnetized Iron Neutrino Detector at J-PARC

The Baby-MIND (magnetized iron neutrino detector) collaboration is building a muon detector to be installed downstream of the WAGASCI experiment at J-PARC (Japan). Due to the challenging timeline and space constraints for the installation in the ND280 pit, an innovative magnetization scheme has been developed for the iron plates. The magnetization scheme optimizes flux return for minimum stray field and operating current, while maximizing the useful tracking area with

Analysis of ITER PF Coil Joint Design Under Reference Operating Scenario

B > 1.5

Preliminary Conductor Layouts for the Detector Magnets of the Future Circular Collider

T. The 33 iron plates of the detector are individually magnetized by coils wound on their surface by “sewing” an aluminum conductor through slits cut in the plates. In this paper, we present the details of the magnetization scheme and coil winding procedure as well as the results of magnetization tests performed on a prototype module and the first eighteen detector plates.

Superconducting magnet with the reduced barrel yoke for the hadron Future Circular Collider

One of the critical components of the ITER poloidal field (PF) coils is the electrical joint connecting two conductor lengths. The lap “shaking hands” joints will operate under variable field, causing parasitic-induced currents in superconducting strands and temperature rise of the strands. Previously, some design changes for decreasing the induced currents in the joints were proposed and assessed with the JackPot-ACDC model. In this paper, we use the same model to compare the behavior of two designs under the reference operation cycle of the PF coils. It is concluded that the joints with the proposed design changes will have sufficient stability margin against thermal and electromagnetic disturbances.

Baby MIND: A magnetised spectrometer for the WAGASCI experiment

For the Future Circular Collider (FCC) presently under the conceptual design at the European Council for Nuclear Research (CERN), very large conductors are needed for the detector magnets. The requested critical current is an order of magnitude higher than that of the previous generation, corresponding to about 250 kA at 4.2 K and 5 T. Characteristic conductor layouts, particularly the type and fraction of structural materials, are reviewed in order to extrapolate to the most promising designs and adapt those to the requirements imposed for the FCC detector magnets. The nominal currents required at characteristic operating conditions of 6.5 T and 4.6 K, conductor dimensions, production unit lengths and mass are investigated for defining the design of the conductor. For comparing various conductor layout options, and as a first step in the conductor R&D, it is proposed to study the conductor sizing according to relevant material characteristics.

The Baby MIND spectrometer for the J-PARC T59(WAGASCI) experiment

The conceptual design study of a hadron Future Circular Collider (FCC-hh) with a center-of-mass energy of the order of 100 TeV in a new tunnel of 80-100 km circumference assumes the determination of the basic requirements for its detectors. A superconducting solenoid magnet of 12 m diameter inner bore with the central magnetic flux density of 6 T is proposed for a FCC-hh experimental setup. The coil of 24.518 m long has seven 3.5 m long modules included into one cryostat. The steel yoke with a mass of 21 kt consists of two barrel layers of 0.5 m radial thickness, and 0.7 m thick nose disk, four 0.6 m thick end-cap disks, and three 0.8 m thick muon toroid disks each side. The outer diameter of the yoke is 17.7 m; the length without the forward muon toroids is 33 m. The air gaps between the end-cap disks provide the installation of the muon chambers up to the pseudorapidity of ±3.5. The conventional forward muon spectrometer provides the measuring of the muon momenta in the pseudorapidity region from ±2.7 to ±4.6. The magnet modeled with Cobhams program TOSCA. The total Ampere-turns in the superconducting solenoid coil are 127.25 MA-turns. The stored energy is 43.3 GJ. The axial force onto each end-cap is 480 MN. The stray field at the radius of 50 m off the coil axis is 14.1 mT and 5.4 mT at the radius of 100 m. All other parameters presented and discussed.

Superconducting Magnet with a Minimal Steel Yoke for the Future Circular Collider Detector

The WAGASCI experiment being built at the J-PARC neutrino beam line will measure the ratio of cross sections from neutrinos interacting with a water and scintillator targets, in order to constrain neutrino cross sections, essential for the T2K neutrino oscillation measurements. A prototype Magnetised Iron Neutrino Detector (MIND), called Baby MIND, has been constructed at CERN and will act as a magnetic spectrometer behind the main WAGASCI target. Baby MIND will be installed inside the WAGASCI cavern at J-PARC in the beginning of 2018. Baby MIND will be able to measure the charge and momentum of the outgoing muon from neutrino charged current interactions, to enable full neutrino event reconstruction in WAGASCI. During the summer of 2017, Baby MIND was operated and characterised at the T9 test beam at CERN. Results from this test beam will be presented, including charge identification performance and momentum resolution for charged tracks. These results will be compared to the Monte Carlo simulations. Finally, simulations of charge-current quasi-elastic (CCQE) neutrino interactions in an active scintillator neutrino target, followed by the Baby MIND spectrometer, will be shown to demonstrate the capability of this detector set-up to perform cross-section measurements under different assumptions.