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Particle accelerators foresee the use of Nb3Sn in the next generation of dipole magnets. A common design strategy is to grade the coil, i.e., to optimize the quantity of superconductor in the turns with respect to the magnetic field intensity. As a consequence, the magnet winding consists of different Nb3Sn Rutherford cables that must be connected in series through splices having sufficiently low electrical resistance. In previous works, the Swiss Plasma Center designed and tested in the SULTAN facility bent diffusion-bonded splices for wind-and-react dipole magnets to develop an internal splice, i.e., to be embedded in the winding pack. The global splice resistance met the requirement. Such splices consist of hundreds of parallel resistive diffusion-bonded spots, located at the cross-over of the two overlapped Rutherford cables. In this manuscript, samples of single diffusion-bonded spots are manufactured and electrically tested to assess their resistance. The results are in line with the expectations, despite the scattering of the experimental data. Moreover, the network of strands and spots is recreated in an electrical model to interpret the resistance-field characteristic assessed from the measurements of splices between Nb3Sn Rutherford cables. [ABSTRACT FROM AUTHOR]

The installation of a superconducting radio-frequency (SRF) cavity can improve the beam lifetime via increasing the electron bunch length. A prototype 1.5-GHz SRF passive harmonic cavity working at 4.5 K was designed for The Taiwan Photon Source (TPS). As the beam might become unstable because of the coupled-bunch instability resulting from Higher Order Modes (HOMs) of the SRF harmonic cavity, HOMs damping of this cavity is an important issue. Ferrite absorbers placed in the beam tubes are designed to damp the HOMs. A theoretical calculation for the instability threshold for the HOMs is given. A tracking method is used to simulate the instabilities for operation with this HOMs-damped SRF harmonic cavity. The design and optimization of the HOMs damper, as well as the results of instability studies for this SRF harmonics cavity, are presented here. [ABSTRACT FROM AUTHOR]

High temperature superconductors, including Bi:2212, are being considered for high magnetic field magnets to be used in particle accelerators. A knowledge of HTS magnetization properties are needed for calculating field errors in such accelerator magnets. Here we present magnetic measurements of a 17 strand Bi:2212 Rutherford cable. The Bi:2212 strand was a Bruker OST PMM170123 non-twisted wire wound into a cable with dimensions 1.46 mm x 7.8 mm and cable pitch of 50.8 mm. M-H loop measurements were made with a Hall probe at 4.2 K. Two calibration methods were compared, (i) a flux exclusion approach, and (ii) a Ni replacement technique. The latter was found to be more reliable in this case. An effective filament diameter of 358 μm was calculated for the strand at 4.2 K and a perpendicular applied field of 3.33 T, significantly larger than the diameter of the filament bundle. Magnetization values at 1 T on the shielding branch were seen to be 100 kA/m when normalized to the total strand in the cable volume. The penetration field ≅ 0.4 T. [ABSTRACT FROM AUTHOR]

Coating of surfaces facing particle beams with high-temperature superconductors (HTS) for reducing the beam coupling impedance is being considered for the next generation of hadron colliders, such as the FCC-hh at CERN, where HTS would be exposed to the high-frequency wakefields generated by the particle bunches and to the strong field of the steering magnets. In this frame, we present a simple model for the calculation of the microwave response of HTS exposed to a strong external magnetic field, which takes into account the nonlinearity of the pinning potential of the vortex lattice. The equation of motion of the vortex lattice is solved in first-order approximation, and we calculate the amplitude of the third-harmonic components in the electric field produced by vortex oscillation. We deduce the time-dependent surface impedance, which could serve as a boundary condition in the simulation codes for the calculation of beam-stability phenomena in particle accelerators. Finally, time-integration of the surface impedance allows exploring the dependence of the surface impedance on surface currents, useful for analyzing the experimental results obtained using simple resonators in terms of our model. [ABSTRACT FROM AUTHOR]

Long standing data from niobium thin-film accelerating cavities will be revisited and analyzed by a modified London model of radio-frequency (RF) superconductivity. First, the applicability of this model is explored using the data of the Bardeen–Cooper–Schrieffer (BCS) surface resistance and its dependence on the RF magnetic field, temperature, and mean free path. Second, the RF losses from the trapped magnetic flux are analyzed with regard to their dependence on these same parameters. [ABSTRACT FROM AUTHOR]

Superconducting radio frequency (SRF) cavities are often limited by thermal quench, which is an excessive electromagnetic heating that occurs in the high magnetic field area and expands thereafter forcing the cavity to lose its superconducting state. In this article, we demonstrate how the quench phenomena can be modeled using a coupled electromagnetic thermal analysis. The proposed model takes into account the nonlinearity of the material properties at cryogenic temperature and the effect of Kapitza resistance. The proposed approach is used to compute the thermal quench field of a 3.9-GHz 9-cell accelerating cavity, a 2.815-GHz deflecting cavity, and a 1.3-GHz 9-cell accelerating cavity. The computed values of quench field are in good agreement with the measured ones observed during vertical testing at 2 K. Without loss of generality, the proposed methodology can be applied to other cavity geometries. [ABSTRACT FROM AUTHOR]

Accelerator magnets for future particle accelerators are designed to work with as high energy densities as possible to achieve high fields and compact magnet designs. A key factor limiting the energy density is given by the protection in case of a quench: If a quench occurs, the stored energy must be first absorbed by the windings, and the magnet temperature shall not exceed a given limit. In this paper, we present a back-of-the-envelope method for estimating the magnet's maximum temperature after a quench based on its stored energy. The method combines the existing concepts of MIIT (Mega*current*current*time), time margin, and protection delay to allow for an easy and direct calculation of the hot-spot temperature. We apply the proposed method to several ${\text{Nb}}_{3}{\text{Sn}}$ dipole and quadrupole magnets developed for the high luminosity Large Hadron Collider and the Future Circular Collider for hadron–hadron collisions and compare the results to a more detailed simulation. The proposed energy density method is a useful tool for fast feedback in the early magnet design phase to ensure that the magnet is not impossible to protect. [ABSTRACT FROM AUTHOR]

For reaching very high magnetic fields in fully superconducting magnets, beyond 16 T for particle accelerators dipoles and beyond 23 T for solenoids, the use of high-temperature superconductors (HTS) is unavoidable. Due to the high minimum quench energy in HTS these coils are much more difficult to protect against quenches using conventional methods, such as quench heaters or coupling loss induced quench (CLIQ). Although it is possible to use a dump resistor on a short HTS magnet, extracting the energy externally, this does not provide a solution for longer magnets or magnets operated in a string, because the extraction voltage becomes unacceptably high. Here, a method named E3SPreSSO (External Energy Extraction Symbiotic Protection System for Series Operation) is proposed that allows for fast energy extraction in HTS magnets. The E3SPreSSO comprises of units with a near-zero self-inductance superconducting circuit, connected in series with the main magnet. When the protection is triggered, these devices are turned resistive, using quench heaters, overcurrent or CLIQ, causing them to absorb the energy of the system. The units can be located outside the main magnet and do not generate magnetic field. Therefore, it is possible to use relatively cost-efficient and robust Nb–Ti or possibly MgB $_2$ (at higher temperatures). This paper introduces the concept and provides an analytical method weighing the different options for designing the E3SPreSSO units themselves. [ABSTRACT FROM AUTHOR]

The Q-factor of superconducting accelerating cavities can be substantially improved by a special heat treatment under N2 atmosphere (N-doping). Recent experiments at Fermi National Laboratory investigated the dependence of Q on the RF frequency and showed, unexpectedly, both an increase and a decrease with the RF field amplitude. This paper shall explain this finding by extending a previously proposed model founded on the two fluid model of RF losses, percolation, and the proximity effect in a disordered composite. [ABSTRACT FROM AUTHOR]

Superconducting coils limit current is usually measured on unloaded short samples of strands extracted from the same cable used to wound the coil. However, the critical current density of Nb3Sn strands is strongly dependent on the applied strain. This dependence is well reproduced by the so-called exponential scaling laws on strands subject to uniaxial loading. Unfortunately, no standard procedure exists to apply these laws under the complex stress condition experienced by the strands inside Rutherford cables for particle accelerator magnets. As a consequence, an empirical limit from magnet tests was set in the past: 150-200 MPa of maximum equivalent stress within the coil, considered as a block of uniform material. It is not clear how this number relates with the actual stress/strain state in the strands and if it is possible in magnet applications to infer the coil degradation from single strands tests. In this context, this paper presents a model to estimate the critical current degradation of superconducting coils as a function of the applied strain. The model results were compared against the critical current degradation measured on impregnated cable stacks subject to transverse pressure. [ABSTRACT FROM AUTHOR]

The Nuclotron-based Ion Collider fAcility (NICA) accelerator complex is scheduled to be put into operation in full configuration in 2023 at JINR. This facility comprising the existing Nuclotron together with two newly created superconducting accelerators--booster and collider--will require additional refrigerating capacity at 4.5 and 77K.The helium cryogenic system of the NICA complex will be constructed as a result of the modernization of the existing equipment for cryogenic supply of the Nuclotron, but the liquid nitrogen plant will be completely new. Itwill be based on a 1300 kg/h nitrogen liquefier and two 500 kg/h recondensers of nitrogen vapors. This report describes the schematic diagram of the system of liquid nitrogen that will be used for refrigerating the thermally insulating shields of the cryostats at 77 K and at the first stage of cooling down three accelerator rings with the total length of about 1 km and the "cold" mass of 290 t. We demonstrate the status and recent development of the nitrogen cryogenic system: location, basic parameters, and design of major components and discuss their phased commissioning. [ABSTRACT FROM AUTHOR]

The CERN SRF infrastructure was originally set up for Nb on Cu-coated cavities for large electron positron collider (LEP) and later for large hadron collider (LHC). Today, Superconducting RF has become a vital technology not only for LHC but also for high intensity and energy upgrade of isotope separator on line device (HIE-ISOLDE) and the high luminosity (HL)-LHC project. More superconducting cavities will be needed for a potential high energy (HE)-LHC or for any of the future circular collider options, which are currently under study. To meet these demands, CERN has improved its SRF infrastructure over the recent years and has started several R&D lines including improved thin film coating techniques, high-power couplers, cold-test diagnostics, etc. This paper will give an overview of CERN's SRF activities today, and the challenges of future projects. [ABSTRACT FROM AUTHOR]

Superconducting magnets have been widely used in medical devices for several decades, primarily in thousands of MRI systems worldwide. More recently superconducting magnets have begun to have a small but growing impact on a newer field of medical devices, namely cyclotron accelerators for hadron therapy. This is a form of radiation treatment that uses ionized particle beams (instead of X-rays) to treat a wide variety of cancerous tumors, being particular effective for certain types of pediatric cancer. Although there is growing interest and demand in the medical community for hadron therapy systems, growth in this form of treatment system has been hampered by the very large infrastructure required by conventional accelerator and beam delivery systems, and their concomitant high capital costs. This issue is being addressed by the use of high field superconducting cyclotrons, which offer much more compact accelerators with reduced footprints, along with lower operating costs. In this paper, we describe the background and history of superconducting cyclotrons, and provide a survey of recent developments in this field of application. We also describe the design of a novel, ironless superconducting cyclotron being studied at the Massachusetts Institute of Technology (MIT), Cambridge, MA, USA, and how this technology could be a path towards significantly more widespread deployment of this form of cancer treatment. [ABSTRACT FROM AUTHOR]

Nuclotron-based IonCollider fAcility (NICA) is a new accelerator collider complex currently under construction at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia. The facility includes a new superconducting booster synchrotron whose layout includes 40 dipole and 48 quadrupole superferric magnets. Booster magnets are under serial production, assembling and testing at the new test facility at JINR, Dubna. The designs of NICA magnets are based on the Nuclotron magnet design. The dipole magnets for the NICA booster have a length of 2.14 m, an aperture of 128/165 mm, and a curved yoke with bending radius of 14.1 m. Two quadrupole magnets are connected together to form a doublet. Measurement of the magnetic field parameters are assumed for each booster magnet. 80% of the dipole magnets and 10% of the doublets have successfully passed the tests. We present the cold test results that were obtained from the magnetic measurements of dipole magnets and compare them with the requirements of the specification. Preliminary results of cold magnetic measurements of the first serial doublets are summarized here. [ABSTRACT FROM AUTHOR]

For the high-luminosity upgrade of the Large Hadron Collider (HL-LHC), the development of the 11-T Nb3Sn dipole (MBH) is progressing. At present, one double-aperture and five single-aperture short-model magnets have been built and tested. Magnetic measurements have been performed both at ambient and cryogenic temperatures. In addition, a double-aperture short model and the first full-length collared-coil assemblies have been produced andmeasured at ambient temperature. In this paper, the measurement results collected so far are presented and discussed. The geometrical field multipoles, the iron saturation effects, as well as the effects of persistent currents are summarized. Experimental data are compared with the magnetic calculations using the CERN field computation program ROXIE and discussed in view of the construction of the final magnets. In addition, based on the measured field errors, beam dynamics simulations have been carried out by taking into consideration different scenarios with and without MBH magnets installed in the accelerator. [ABSTRACT FROM AUTHOR]

The high-luminosity upgrade of the large hadron collider (HL-LHC) requires new high-field and large-aperture quadrupole magnets for the low-beta inner triplets (MQXF). CERN and LARP are currently collaborating to develop a 150-mm-aperture quadrupole based on Nb3Sn superconducting cables for the coils, and an aluminum shell with the bladder-key technology for the support structure. This paper presents the test setup for magnetic measurements, both at ambient and cryogenic temperatures, and the instrumentation being used for the first two short-models of MQXF built and tested at CERN. Finally, the measurement results, in terms of field quality, effects of persistent currents, and iron saturation are reported and discussed. [ABSTRACT FROM AUTHOR]

Started in January 2015, a 230-MeV superconducting cyclotron is under construction in the China Institute of Atomic Energy for proton therapy. A compact main magnet design with warm iron yokes and a superconducting coil system is adopted to reduce the size, construction, and operation cost of the cyclotron. In this paper, the field calculations of the main magnet are briefly described; then, the R&D of the superconducting coil system are outlined in detail, including the cryogenics design of the system, the forces, and stress analysis of the superconducting coil and support links, the power supply and quench protection design. Some preliminary test results are also presented. [ABSTRACT FROM AUTHOR]

For the applications of proton therapy and proton irradiation, and based on theR&Dstarting from2009, a construction project of a 230-MeV superconducting cyclotron (CYCIAE-230) was launched at the China Institute of Atomic Energy in January 2015. A compact main magnet design with warm iron yokes and a superconducting coil system is adopted to reduce the size and, consequently, to lower the construction and operation cost of the cyclotron. In this paper, the physics design, along with the mechanical design of the main magnet, including the structure of the main magnet is described in detail; then, the construction progress and the B-H curve measurement results of the warm iron over the magnetic saturation region are outlined; the R&D of the superconducting coils system and the design of the field mapping system are also briefly introduced. [ABSTRACT FROM AUTHOR]

A proton therapy facility with two 360° gantry treatment rooms and one fixed beamline is under development in the Huazhong University of Science and Technology, which is based on the isochronous superconducting cyclotron scheme. This paper presents the beam optics and main magnetic elements including dipoles, quadrupoles, and fast scanning magnets of the gantry beamline. In addition, the energy selection system will be introduced, which enables fast energy modulation of proton beam between 70 and 240 MeV. [ABSTRACT FROM AUTHOR]

Superconducting magnets often experience premature quenches, requiring a training phase to reach the desired current. Mechanical disturbances are considered the main causes of such a behavior. A prestress is applied in order to limit these disturbances, compressing the coil against the winding pole. Measurements show that the prestress is continuously reduced by the electromagnetic forces. In some cases, a further increase of the current does not produce any variation on the measured stress. This is considered a sign that no further prestress is available, and was intuitively associated in the past to the detachment of the coil from the pole. This paper attempts to study this phenomenon, reproducing the stresses measured during training by means of a numerical model. Cohesive elements were used to simulate the detachment at the pole/coil interface. Numerical results were compared with the experimental data from the recent test of MQXFS1, the first short model of the triplet quadrupole for the Large Hadron Collider Hi-Luminosity upgrade. [ABSTRACT FROM AUTHOR]

We revisit the classical rigid-fluxon model which describes the effect of an applied magnetic flux on the RF surface resistance of a superconductor and discuss explicit formulations for a few limit cases. As an application, we discuss the role of magnetic flux on the enhanced surface resistance of RF accelerating cavities based on niobium, depending on its material properties. We also assess the conditions for the use of high-temperature superconductors for carrying the beam image RF currents in future high-energy circular hadron colliders such as the future circular collider being studied at CERN. [ABSTRACT FROM PUBLISHER]

High Tc superconducting (HTS) insert in combination with low Tc superconducting (LTS) outsert is the only possibility today to go above 16 T for future high-energy particle accelerator dipoles. These HTS inserts will feature large operating current (≥ 10 kA) and high background fields (≥ 13 T) leading to severe operating conditions. In our 46-turns HTS insert, a 4 × 4 mm twisted stacked cable composed of 20 tapes and carrying 10.4 kA is used. It is simple to manufacture and enables a partial transposition. The designed insert can generate 5 T with good field homogeneity, assuming a homogeneous current density in the cable. However, a half twist per turn applied in the magnet ends of a 15-m-long insert makes it difficult to obtain both low magnetization and uniform current distribution in the cable. Three twisted stacked cables solutions are numerically studied: noninsulated cable, insulated cable, and partially insulated cable. The simulated HTS insert is first submitted to the external field of the outsert then the current is ramped up to nominal value. The partially insulated twisted stacked cable compounds both advantages of noninsulated and insulated cables, and thus appear to be the best solution for the HTS insert. [ABSTRACT FROM PUBLISHER]

High-field superconducting magnets are the key components of the high-energy particle accelerators. The Institute of High Energy Physics, Beijing, China, has been working on the related R&D since 2014. In parallel with the baseline R&D roadmap with common coil configuration, preliminary electromagnetic design of a 20-T 2-in-1 dipole magnet with cos-theta configuration has been carried out as an option for the model magnet R&D in future. Totally six layers of coils are required for each aperture of this dipole with the high temperature superconductor for the inner two layers and the low temperature superconductor for the outer four layers. Graded coil design is selected to increase the efficiency of the conductor utilization. For each aperture, the clear bore diameter is 50 mm. Asymmetric coil configuration has been adopted to obtain a good geometrical field quality. After optimization, the field uniformity of 10−4 within 2/3 of the aperture is achieved. The coil ends of the dipole magnet have also been designed and optimized. The detailed magnetic analysis and the main characteristics of this magnet are presented. [ABSTRACT FROM PUBLISHER]

A multilayer high field dipole magnet has been designed for future particle accelerators. The magnet has eight layers of a \Nb3\Sn outsert coil and four layers of a Bi-2212 insert coil (see Figs. 1 and 2). The layers are graded, delivering a short-sample field of 17.7 T in a 40-mm bore. The coil layers are of a canted cosine–theta design—with ribs and spars that guide and support the coil windings, shape the field, intercept Lorentz forces, and minimize conductor prestress. We present a general overview of the concept and report on the magnetic and mechanical design including an initial cost estimate and construction plan. [ABSTRACT FROM PUBLISHER]

Magnetic field harmonics (multi-pole component of magnetic field) were measured in a 24-layer coil for a dipole magnet wound with NbTi round wires by using the surface winding technology (direct winding technology). The coil was wound layer by layer, and the magnetic field measurements were carried out by using rotating pick-up coil system, when the 4 layers, 10 layers, 16 layers, 20 layers, and 24 layers of the coil were wound. The measured magnetic field harmonics were compared with theoretical values. The error, which is the difference between the measured value and theoretical one, does not increase substantially with increasing number of wound layers when measured at the center of the coil. Larger errors measured near the coil end should have been caused by the position errors of wires, which was observed visually. [ABSTRACT FROM PUBLISHER]

The Facility for Rare Isotope Beams (FRIB) calls for magnets with fields with varying multipole content. Magnets of this type can be fabricated with either conventional or superconducting windings. Many of these magnets will be located in regions with very high levels of neutron radiation. The radiation can cause heating in the conductor and any iron that is around the conductor. This report describes a magnet that is a combined sextupole and octupole. Because of the high radiation environment this magnet will see, the magnet designs presented here use conventional copper conductors. Three coil and iron designs are presented in this paper. Since FRIB is a single pass machine, the design field requirements for this magnet are not as stringent as they would be for a typical circular accelerator. [ABSTRACT FROM PUBLISHER]

We have developed the most upstream dipole magnet K1.1D1 for a new secondary beam line at the hadron experimental hall in J-PARC. It is placed downstream of a production target and is close to the K1.8D1 magnet. Indirectly cooled coils using mineral insulation cables have been adopted for high radiation resistance. The coils have a slanting saddle shape in order to minimize the interference of the magnetic field between the two magnets. It has been operated during the beam time in the autumn of 2010 without any problems. [ABSTRACT FROM PUBLISHER]

The accelerator complex FAIR consists out of two superconducting synchrotrons, several storage rings and beam lines. Therefore there are many injection and extraction areas where septum magnets are necessary. Some of them have to be designed under crucial conditions, which may be difficult to accomplish with a conventional C-shape iron septum magnet. An alternative concept of a truncated, iron-yoked cosine theta magnet is proposed in this paper. Design studies for the FAIR septum magnets are presented as well. [ABSTRACT FROM PUBLISHER]

Most of today's particle accelerators are used in industry or for medical applications, for example, in radioisotope production and cancer therapy. One important factor for these applications is the size of the accelerator, which ideally should be as small as possible. In this respect, fixed-field alternating-gradient accelerators (FFAGs) can be an attractive alternative, which combine the best features of conventional synchrotrons and cyclotrons: FFAGs deliver better performance than synchrotrons while retaining flexibility. Of particular interest are accelerators for protons of moderate energy (0.25–1 GeV) and light ions such as carbon (up to 400 MeV per nucleon), for example, for proton/carbon-ion charged particle therapy or potential future applications such as accelerator-driven subcritical reactors. Due to high magnetic rigidity, a compact machine can be only achieved by using high field superconducting magnets. A disadvantage of FFAGs is that the magnetic elements can be very challenging. Quite often, complicated multipole fields are required, in combination with stringent geometric constraints. In this paper, we demonstrate the advantages of helical coil technology by means of an accelerator for proton therapy. [ABSTRACT FROM AUTHOR]

The incident in the LHC in September 2008 occurred in an interconnection between two magnets of the 13 kA dipole circuit. This event was traced to a defect in one of the soldered joints between two superconducting cables stabilized by a copper busbar. Further investigation revealed defective joints of other types. A combination of (1) a poor contact between the superconducting cable and the copper stabilizer and (2) an electrical discontinuity in the stabilizer at the level of the connection can lead to an unprotected quench of the busbar. Once the heating power in the unprotected superconducting cable exceeds the heat removal capacity a thermal run-away occurs, resulting in a fast melt-down of the non-stabilized cable. We have performed a thorough investigation of the conditions upon which a thermal run-away in the defect can occur. To this aim, we have prepared heavily instrumented samples with well-defined and controlled defects. In this paper we describe the experiment, and the analysis of the data, and we summarize the main results which are relevant to delimit the conditions of safe operation for the LHC. The results obtained, and specifically a controlled replica of the September 2008 incident demonstrate the necessity to re-work all main-circuit interconnects in the LHC in order to operate safely at the nominal energy. [ABSTRACT FROM AUTHOR]

The construction of the 1st phase Japan Proton Accelerator Research Complex (J-PARC) was completed. Three major experimental facilities, which have been utilized by users, are instrumented with the superconducting magnet systems; a muon transport solenoid in Materials and Life Science Experimental Facility, a superconducting spectrometer in Hadron Experimental Facility, and a 150 m superconducting beam line in Neutrino Experimental Facility. There are also several superconducting magnet systems proposed as part of future experiments at J-PARC. The paper briefly summarizes the current status of the superconducting magnet systems currently in operation, and introduces the superconducting magnet systems associated with the new proposals. [ABSTRACT FROM AUTHOR]

Following the development of Nb3Sn and niobium based solution alloys in 1961 the field of High Energy Physics has witnessed a continual development of magnets and devices for the generation, beam handling and analysis of particle beams and their interactions. This paper will examine the technology development of these devices from the earliest bubble chambers through the development of theories of stability and on to the construction of superconductivity based particle accelerators and their associated detectors. The latest advances in superconducting radio frequency accelerating cavities will be considered within this R&D model. This development of technology was accomplished by universities, national laboratories and industry working in a most cooperative way. [ABSTRACT FROM AUTHOR]

The new muon beamline, MuSIC, is being constructed at the Research Center for Nuclear Physics (RCNP) at Osaka University in Japan. The project utilizes superconducting solenoid magnets to collect pions and to transport muons with the ultimate efficiency by putting pion-production target inside the solenoid magnet. This is the first of such a novel method to produce intense muon beams. All the superconducting coils are cooled with conduction cooling using Gifford-McMahon cryocoolers. A large superconducting coil with the diameter of 90 cm encloses the pion-production target and thick shielding to protect the coil against severe radiation from the target, so that energy deposit by particles on the coil should be less than 1 W. Pions are captured in a 3.5 T magnetic field and are injected into the subsequent toroidal magnets with the magnetic field of 2 T. Superconducting dipole coils are equipped on each solenoid coil of the transport solenoid to correct the particle trajectory in the toroidal field. The design and construction status of the solenoid channel are described in this paper. [ABSTRACT FROM AUTHOR]

A fundamental limitation towards achieving high quality factors in superconducting radio-frequency cavities is the so-called residual resistance. Understanding and controlling the residual resistance has important implications towards improving the efficiency and reduce the operating cost of continuous wave superconducting linear accelerators. In this contribution we will report on the residual resistance values obtained from measurements of the quality factor of a large set of cavities, with resonant frequency between 805 MHz and 1.5 GHz, all of them processed and tested at Jefferson Lab. Surface treatments included both buffered chemical polishing and electropolishing. The results indicate an approximate value of the residual resistance of about 7–10 n\Omega. [ABSTRACT FROM AUTHOR]

The high energy sections of the Fermilab HINS R&D proton linac will utilize superconducting spoke resonator (SSR) RF cavities. These will be assembled into cryomodules with strong solenoid focusing lenses closely interleaved with the cavities. A design for lenses has been made for the lower (SSR1) and higher (SSR2) energy ranges of the SSR-section. Prototype lenses for both SSR1 and SSR2 sections have been built and the SSR1 has been tested. Shielding is needed to reduce the solenoid fringe field on the cavity wall below the 10 \muT level, and a preliminary design was built and tested with the SSR1 prototype lens. We discuss the design requirements and challenges, and the results from quench testing and magnetic measurements of the SSR1 prototype lens. [ABSTRACT FROM AUTHOR]

Conceptual designs of a superconducting dipole magnet for a storage ring of a muon collider with a 1.5 TeV center of mass (c.o.m.) energy and an average luminosity of 10^34\ cm^-2s^-1 are presented. In contrast to proton machines, the dipoles for the muon collider should be able to handle \sim0.5 kW/m of dynamic heat load from the muon beam decays. The magnets are based on Nb3Sn superconductor and designed to provide an operating field of 10 T in the 20-mm aperture with the critical current margin required for reliable machine operation. The magnet cross-sections were optimized to achieve the best possible field quality in the aperture occupied by beams. The developed mechanical structures provide adequate coil prestress and support at the maximum level of Lorentz forces in the coil. Magnet parameters are reported and compared with the requirements. [ABSTRACT FROM AUTHOR]

A new radioactive ion beam project, Beijing Radioactive Ion-beam Facility (BRIF), has been started at CIAE since 2004. In this project, a 100 MeV H- cyclotron, CYCIAE-100, is selected as the driving accelerator providing 75-100 MeV, 200-500 µA proton beam. CYCIAE-100 is consisting of the main magnet, RF system, ion source and injection system, dual beam extraction system, etc. The progress of this machine had been reported elsewhere. The main magnet is the most critical part and had been numerically simulated and delicately designed. The techniques for main magnet construction are investigated in detail. The construction of this compact style, 450 ton cyclotron magnet has been started since 2007. The imperfection control of the large scale casting steel, the deformation and fabrication tolerance, etc., have all posed a challenge to the capacity limitation of cyclotron lab at CIAE for magnet design, mapping and shimming, and of industry for steel production/machining in the world. The design highlight of the magnet will be briefly introduced and the emphasis in this paper will be given to the construction progress. [ABSTRACT FROM AUTHOR]

Many applications using accelerator beams require a nearly uniform beam distribution at the target. A nested structure magnet producing a step-like magnet field has been proposed to transform an originally Gaussian or even irregular distribution into a more-or-less uniform one at targets. In this paper, the prototyping of a step-like field magnet is presented, which is based on the application in the China Spallation Neutron Source where the magnets are used to obtain a uniform beam profile from an initially irregular distribution at the spallation target. It includes the magnet design, 3D magnetic field calculation, prototype fabrication and field measurement. The prototyping confirms the technical feasibility of the magnet structure and the magnetic field quality consistent with the field calculations. The design improvements are discussed from the prototyping experience. [ABSTRACT FROM AUTHOR]

Magnets of the synchrotron which extracts the accelerated beams are excited by a pulse operation power supply, and then the load fluctuation should be a severe problem. An energy storage system, such as superconducting magnetic energy storage (SMES), fly-wheel generator so far, will be required for compensating the pulse electric power, and reducing the disturbances of the connected power line. The system is expected to protect the instantaneous voltage drop and the load fluctuation. Present status of R & D and the features for the energy storage systems are discussed. The application of the energy storage systems to synchrotrons for the medical use is described. The compensation of the typical pulse electric power of the synchrotron for the cancer therapy is studied, and the operation cost saving and the cost performance of the SMES system are discussed. [ABSTRACT FROM AUTHOR]

For compact cyclotrons, it is a common practice to avoid using adjusting coils to assist the formation of field distribution. However, it is necessary to employ the adjusting coil system in some special cases, as for CYCIAE-100, a high intensity compact cyclotron under construction at CIAE. To limit the cost for the main magnet, the casting steel is used for the top/bottom and return yokes. The imperfection should not be ignored and the harmonic coils on the return yokes will enable the field to reach the requirements easier during the shimming. During the beam commissioning, centering coils are always needed for this compact machine with ~400 turns' acceleration. When the machine is in operation, the field distribution will be changed by several factors, e.g. the thermal deformation, and the trim coils will probably be used to adjust the isochronism. In this paper, the effects of various adjusting coils, including 2 sets of centering coils on the hills in the central region, 8 sets of trim coils in the valleys and 1 set of trim coils on the hills right outside the centering coils, and 1 set of harmonic coils on the 4 return yokes, have been investigated. Then the detail configuration of the adjusting coils, the mechanical design and installation simulation from the coils to the outlet inside the compact machine, will be introduced in the paper. Some experiments, including those for the conductor inside the high vacuum tank, the insulator for high radiation field, and special feed through for high current and high vacuum, etc., are tested and the results will be given as well. [ABSTRACT FROM AUTHOR]

A number of compact cyclotrons accelerating H- ions to energies between 10 MeV and 100 MeV have recently been constructed for research and medical diagnostics/therapy in several countries. However limitations in extracted beam intensity are brought up by inadequate injection efficiency from the ion source into the machine. To improve the optics matching from the external source to machine acceptance, a specially designed small doublet has been developed to replace the traditionally used solenoid in the vertical injection line before the spiral inflector. Due to the narrow space inside the compact cyclotron, the doublet is designed based on the following special consideration: 1) To use the central plug of the main magnet as a part of the return yoke of the doublet; 2) To use the capillary water-cooling conductor for the coil to keep the doublet sufficiently small; 3) To adopt an integral design of the two quadrupoles into one assembly so that they could be installed in the channel of the central plug in high vacuum environment. In this paper, the design of the doublet is introduced. The outer diameter of 118 mm is precisely fit to the central plug of the Verification Facility of High Intensity Cyclotron at CIAE. Its inner diameter is 50 mm for beam injection. It can provide a maximal magnetic field gradient of 2.6 T/m from the measurement. Various kinds of detailed techniques for the doublet fabrication, e.g. the enwinding of capillary water-cooling conductor with outer diameter of 3 mm and inner diameter of 2 mm, the poles and yoke assembling, will be presented. The beam test results will be given as well. [ABSTRACT FROM AUTHOR]

Korea Institute of Radiological & Medical Sciences (KIRAMS) has been developing a superconducting cyclotron since 2007. This paper is concentrated on the design of the superconducting magnet system. The superconducting magnet for a cyclotron consists of an iron yoke and a superconducting coil system. This paper presents the designed spiral sector for beam stability and the design results of the superconducting coil system. Additional test results of the superconducting coils are described. [ABSTRACT FROM AUTHOR]

A polyhedral cavity design is being developed for particle accelerators, with particular potential application to future linac colliders. In essence it is a polyhedral analog of a multi-cell cavity, but the beam's eye view ofthe boundaries is a polyhedron instead of a figure of revolution. A multi-cell cavity string is formed as a Roman arch assembly of polyhedral wedges; each wedge has its inner surface contoured to form the ellipsoidal shape desired for the accelerating mode. The polyhedral cavity design has been studied numerically and several significant results are reported. Its Q should be comparable to that of a TESLA cavity. The joints between wedge segments offer the possibility to internally suppress all dipole-type higher-order modes by intercepting and terminating azimuthal currents. The Nb surface is provided as a thin foil bonded to a solid copper wedge machined to the desired contour. The wedge provides stiff support so Lorentz detuning is largely eliminated, and the superfluid refrigeration could be integrated within the wedges so no pool cryostat is required. [ABSTRACT FROM AUTHOR]

Current installation of the Large Hadron Collider (LHC) particle accelerator at CERN has required the use of a harmonic coil magnetic measurement system to quantify the magnetic field harmonic quality of the superconducting, twin aperture LHC dipoles. Current and future needs for measuring fast changing magnetic fields necessitates the use of a rotating unit (RU) and associated electronics to drive this long shaft with increased speed and measurement bandwidth. Therefore, the Fast Magnetic Measurement Equipment (FAME) project has been launched to deliver such a system. A primary obstacle to achieving the goals of the FAME project is the possibility of amplifying mechanical vibrations due to increased speeds. This paper presents the methodology and results of an experimental investigation conducted to estimate mechanical vibrations of the long shaft within a cold-bore mounted anti-cryostat at various rotational speeds using magnetic measurements. [ABSTRACT FROM AUTHOR]

The High-Energy Storage Ring (HESR) to be established as a part of the future Facility for Antiproton and Ion Research (FAIR) at Geseflschaft für Schwerionenforschung (GSI) in Darmstadt (Germany) will be dedicated to studies with antiprotons in the momentum range from 1.5 GeV/c to 15 GeV/c. It will comprise 32 superconducting dipole magnets based on the RHIC DO design, yet with a radius of curvature of 15.279 m. The introduction of a finite radius is motivated by considerations both of field homogeneity along the particle path and available space for the HESR. On the other hand field distortions arise due to the curvature, which may compromise the advantage of the improved exploitation of the good-field region. This detrimental effect on our magnets has been quantified in this publication. [ABSTRACT FROM AUTHOR]

Following the successful adoption of high temperature superconductors (HTS) in over a thousand current leads that will feed 3 MA from warm to cold in the Large Hadron Collider (LHC), the use of HIS has been generally accepted as suitable technology for the design of efficient leads feeding cryo-magnets. We now consider the extension of the technology to the interconnection of strings of superconducting magnets and their connection to feed-boxes through which the excitation current is fed. It is proposed to use HIS material for this application instead of low-temperature superconductor or normal-conducting material. The implications of adopting this technology are discussed with regard to the choice of materials, highlighting the differences with more conventional schemes. Examples are given of how this approach could be applied to the consolidation and upgrade of the LHC. [ABSTRACT FROM AUTHOR]

The recent paper is devoted to design, manufacturing and testing the permanent magnet system to be used for Positron Emission Tomography (PET) cyclotron. The using permanent magnet material instead of copper coils allows essential electric power savings during PET cyclotron operation, though it comes to some increasing construction cost. The main problem why until now permanent magnets were not used for PET cyclotron magnet system is huge magnetic force, making cyclotron assembling/disassembling and isochronous magnetic field adjustment very difficult. For presented magnet system that problem is solved by applying rotating system providing the magnetic field switch-off (reduction to practically zero level inside working aperture). It makes assembling and adjustment easy at force free conditions. The main parameters of permanent magnet system are as follows: the average field is 1.4 T, pole radius is 375 mm and weight is 900 kg. As it shown in paper the magnetic properties of constructed permanent magnet system does satisfy to specification for magnet system of typical 10 MeV cyclotron for PET radioisotope production. [ABSTRACT FROM AUTHOR]

FAGs accelerators re-appeared fifteen years ago to be of interest for new accelerator projects. These synchrotrons allow fast acceleration because of the fixed field magnets. To compensate the beam trajectory radius increase, the radial magnetic gradient follows a non-linear law. Bo (r/Ro )k. In the frame of the RACCAM (Recherche en Accélérateur et Application Médicales) project in France, a scaling spiral FFAG ring is developed for medical applications. Magnets have spiral edges to make beam focusing. Here is described the dipole design study with flat horizontal poles which allow a low variation of the vertical tune. This study presents how to produce Bo (r/Ro ) k with distributed polar conductors. [ABSTRACT FROM AUTHOR]

Various proposals for high energy physics experiments at future facilities, such as the ILC, include large superconducting solenoids for magnetic spectroscopy. It is now established technology to use indirectly cooled windings of aluminum-stabilized Nb-Ti superconductor for such magnets, but for the size and strength of field being considered it is essential to reinforce the pure aluminum stabilizing material. Technologies for strengthening the conductor, which were first developed for some space science and high energy physics detector magnets, have continued to progress, and economic conductors and windings based on the most recent experience are proposed for the next generation of spectrometers. An explanation will be given of the far-reaching technical and cost implications implied in surpassing the intrinsic limits of what can be achieved with this approach to the design of detector magnets. [ABSTRACT FROM AUTHOR]