Dipole Bending Magnets Research Articles

Pulsed-Mode Magnetic Field Measurements with a Single Stretched Wire System.

In synchrotrons, accurate knowledge of the magnetic field generated by bending dipole magnets is essential to ensure beam stability. Measurement campaigns are necessary to characterize the field. The choice of the measurement method for such campaigns is determined by the combination of magnet dimensions and operating conditions and typically require a trade-off between accuracy and versatility. The single stretched wire (SSW) is a well-known, polyvalent method to measure the integral field of magnets having a wide range of geometries. It, however, requires steady-state excitation. This work presents a novel implementation of this method called pulsed SSW, which allows the system to measure rapidly time-varying magnetic fields, as is often needed, to save power or gain beam time. We first introduce the measurement principle of the pulsed SSW, followed by a combined strategy to calculate the absolute magnetic field by incorporating the classic DC SSW method. Using a bending magnet from the Proton Synchrotron Booster located at the European Organization for Nuclear Research as a case study, we validate the pulsed SSW method and compare its dynamic measurement capabilities to a fixed induction coil, showing thereby how the coil calibration must be adjusted according to the field level. Finally, we assess the method's measurement accuracy using the standard SSW as a reference and present an analysis of the primary noise contributors.

Nitrogen Beams with a National Electrostatics Corporation Alphatross Source and a 5SDH Accelerator

Over the past 15 years, Hope College has been producing hydrogen and helium ion beams with an Alphatross® ion source and 5SDH Pelletron® tandem Van de Graaff accelerator. The manufacturer stated the possibility of creating nitrogen ions from this source, but Hope College has not, up until now, attempted to do so. By mixing approximately 1% nitrogen into hydrogen source gas, imidogen (NH-) and amidogen (NH2-) ions are created and accelerated through the tandem accelerator. Oxygen and hydroxide beams are also present due to residual water vapor in the source after maintenance. Post acceleration, these ion beams were directed into a scattering chamber by a dipole bending magnet for identification. Alternate beams such as these open up new possibilities for future experiments such as nitrogen implantation.

Modeling of Beam Loss Induced Quenches in the LHC Main Dipole Magnets

The full energy exploitation of the Large Hadron Collider (LHC), a planned increase of the beam energy beyond the present 6.5 TeV, will result in more demanding working conditions for the superconducting dipoles and quadrupoles operating in the machine. It is hence crucial to analyze, understand, and predict the quench levels of these magnets for the required values of current and generated magnetic fields. A one-dimensional multi-strand electro-thermal model has been developed to analyze the effect of beam-losses heat deposition. Critical elements of the model are the ability to capture heat and current distribution among strands, and heat transfer to the superfluid helium bath. The computational model has been benchmarked against experimental values of LHC quench limits measured at 6.5 TeV for the Main Bending dipole magnets.

Suitability of Different Quench Protection Methods for a 16 T Block-Type Nb3Sn Accelerator Dipole Magnet

Within the future circular collider study, a 100-km long circular hadron collider is being designed for 100 TeV center-of-mass collision energies. The design of the 16 T Nb 3 Sn bending dipole magnets is carried out within the EuroCirCol collaboration. Three different type of dipole designs have been developed, each aiming to be as compact as possible, accounting for the design criteria. Quench protection a critical aspect of the magnet design and potentially limits the magnet compactness. The EuroCirCol magnets were designed assuming a protection system with significantly improved efficiency compared to the present LHC dipole protection. In this paper, we consider present state-of-the-art quench protection technologies, such as quench heaters and CLIQ, and apply them into the designed 16 T Block-type dipole. Two different simulation models are used to estimate the magnet hotspot temperature and voltages after a quench and consequently estimate the suitability of the different methods.

Longitudinal Gradient Dipole Magnet Prototype for APS at ANL

An upgrade of the Advanced Photon Source is being planned at Argonne National Laboratory (ANL). The main goal of the upgrade is to improve the storage ring performance based on more advanced optics. One of the key magnet system elements is bending dipole magnets having a field strength change along the electron beam path. A prototype of one such longitudinal gradient dipole magnet has been designed, built, and measured in a collaborative effort of ANL and Fermilab. This paper discusses various magnetic design options, the selected magnet design, and the fabrication technology. The prototype magnet has been measured by rotational coils, a stretched wire, and a Hall probe. Measurement results are discussed and compared with simulations.

Layout Study for the Dipole Magnets of the Future Circular Collider Using Nb-Ti and Nb3Sn

With the Large Hadron Collider (LHC) up and running, studies have started for its successor. Under study is the Future Circular Collider (FCC), which has a circumference of about 100 km, aiming at a proton-proton collision energy of 100 TeV. Consequently, the main bending dipole magnets have to operate at a magnetic field of 16 T. As a first step towards its realization, this paper presents the results of a parametric study of the cross-sectional layout for dipole magnets with a field in the range of 13-17 T using Nb-Ti and Nb3Sn superconductors. The principal layouts included are the classical Cosine-Theta, the Canted Cosine-Theta, and the Block type. Conductor cost can be reduced significantly when a graded hybrid solution is chosen. Optimizing such complex magnet layouts requires an iterative algorithm, which arranges the positions of the various blocks of coil windings in the coil cross section, thereby finding the thickness of the coil layers. The iterative algorithm is coupled to an adiabatic quench model, which finds an optimal copper-to-superconductor fraction for each of the layers. Outside the iterative cycle, a pattern search algorithm is applied to find a cost optimal distribution of the magnetic field generated by each coil layer.

Experimental Study of the Mechanical Characteristics of SIS300 Cos–Theta Dipolar Coils

The synchrotron SIS300 is a core component of the FAIR facility, which is under development at GSI. The high intensities of proton and heavy ion beams require the synchrotron to be ramped in a few seconds. In particular, the bending dipole magnets have to be pulsed from the injection magnetic field of 1.5 T up to the maximum field of 4.5 T at the rate of 1 T/s. The fast field ramp together with the particular characteristic to be geometrically curved (the sagitta is 114 mm) make these dipoles critical from design and construction point of views. Aside from the thermal ac losses, the mechanical fatigue is one of the main issues of these 7.8-m long magnets having cos–theta shaped coils with a 100-mm bore. Just the large number of magnetic cycles (107) oriented the mechanical design to the involvement of stiff structures working at a relatively low stress level with respect to the elastic limits. To this aim, the coils are mechanically supported by 3-mm thick laminated stainless steel collars, assembled through keys, and 1-mm thick iron yoke laminations kept together through large stainless steel C-shaped clamps. The mechanical behavior of these challenging dipoles has been studied in detail through several 2 and 3-D finite-element (FE) analyses. In order to assess the soundness of the mechanical analysis, a series of mechanical studies were performed on stacking samples and single poles under compression, comparing FE computations with the results of the mechanical tests. Finally, the collaring of short models was performed and the measured deformations were compared with expectations.

Scanning Properties of Dipole Bending Magnets used in Ion-Therapy Gantries

In modern ion-therapy facilities, there is a trend to develop and use scanning beam delivery systems. One of the most important advantages of scanning systems is that the field-shaping material devices in the beam path are minimized or removed entirely. Scanning systems inherently provide the intensity modulated radiation fields of ion beams that allow for a much greater flexibility in tailoring the dose distribution than in the case of passive delivery systems. A study of scanning properties of dipole bending magnets is published in order to provide engineers the theoretical tool for the early stage of a scanning-system design. This study is focused on scanning properties of dipole bending magnets with pure dipole fields without any gradient. The 90°, 60°, 45° and 30° bending magnets are studied. A two-directional magnetic scanning system with two scanners, one in the horizontal and another one in the vertical plane, is considered. This 2D magnetic scanning system ensures a parallel scanning mode in both transverse planes. The ion-optical properties of 2D magnetic scanning system and the study results for dipole bending magnets mentioned above are discussed.

Measurements and Analysis of the SIS-300 Dipole Prototype During the Functional Test at LASA

The FAIR facility, under construction at GSI, includes the synchrotron SIS300 (300 Tm rigidity). In order to reach the required high intensities of proton and heavy ion beams, the bending dipole magnets (beam tube diameter aperture 100 mm) have to be pulsed from the injection magnetic field of 1.5 T to the extraction field of 4.5 T at the rate of 1 T/s. The first 3.9-m-long model dipole has been built and the tests have been carried out at LASA Lab in 2012. These tests have allowed assessment of the performance of the magnet, also in pulsed regime. The performance limitation in fast ramp condition appeared mostly due not only to the ramp rate, but also to the total variation of the current, suggesting an effect due to induced current in the superconducting strands in a particular zone of the conductor. The paper illustrates the results of the measurements and presents some models to describe the quench during the ramp of the current.

Upgrade of the facility EXOTIC for the in-flight production of light Radioactive Ion Beams

The facility EXOTIC for the in-flight production of light weakly-bound Radioactive Ion Beams (RIBs) has been operating at INFN-LNL since 2004. RIBs are produced via two-body reactions induced by high intensity heavy-ion beams impinging on light gas targets and selected by means of a 30°-dipole bending magnet and a 1-m long Wien filter. The facility has been recently upgraded (i) by developing a cryogenic gas target, (ii) by replacing the power supplies of the middle lenses of the two quadrupole triplets, (iii) by installing two y-steerers and (iv) by placing two Parallel Plate Avalanche Counters upstream the secondary target to provide an event-by-event reconstruction of the position hit on the target. So far, RIBs of 7Be, 8B and 17F in the energy range 3–5MeV/u have been produced with intensities about 3×105, 1.6×103 and 105pps, respectively. Possible light RIBs (up to Z=10) deliverable by the facility EXOTIC are also reviewed.

The Functional Test of the SIS300 Model Dipole at INFN-LASA

The FAIR facility, under construction at GSI, includes the synchrotron SIS300 (300 Tm rigidity). To reach the required high intensities of protons and heavy ion beams, the bending dipole magnets (beam tube diameter aperture 100 mm) have to be pulsed from the injection magnetic field of 1.5 T to the extraction field of 4.5 T at the rate of 1 T/s. The first 3.9-m-long model dipole has been built and the functional tests have been carried out at LASA Lab. These tests have been performed inside a vertical cryostat in boiling helium at 4.2 K, and they were aimed to verify the operation of the magnet, also in pulsed regime. The paper illustrates the commissioning activities of the test station and the results of the magnet tests. The performance of the magnet with respect to quench stability and heat losses in pulsed regime will be compared with the design values.

The Preparation of the LASA Test Station for the SIS300 Model Dipole

The FAIR facility, under development at GSI, includes the synchrotron SIS300 (300 Tm rigidity). In order to reach the required high intensities of proton and heavy ions beams, the bending dipole magnets have to be pulsed from the injection magnetic field of 1.5 T up to 4.5 T maximum field at the rate of 1 T/s in a 100 mm diameter bore. The first 3.9 m long model dipole is in advanced construction and a functional test is foreseen at LASA Lab. This test will be performed inside a vertical cryostat in boiling helium at 4.2 K, and it is aimed to verify the operation of the magnet, also in pulsed regime, and to assess the losses. A final full characterization of the magnet will be performed later in a laboratory equipped for operation at the design conditions, i.e. supercritical helium at 4.7 K. This paper illustrates the design and the installation activity of the test station and its capabilities at LASA.

The Construction of the Model of the Curved Fast Ramped Superconducting Dipole for FAIR SIS300 Synchrotron

The Facility for Anti-proton and Ion Research (FAIR), under development at GSI, includes the synchrotron SIS300, so called because the magnetic rigidity is 300 Tm. In order to reach the required high intensities of proton and heavy ions beams, the bending dipole magnets have to be pulsed from the injection magnetic field of 1.5 T up to 4.5 T maximum field at the rate of 1 T/s. These 7.8 m long magnets have cos θ shaped coils with a 100 mm bore and the particular characteristic to be geometrically curved, with a sagitta of 112.9 mm. These challenging requirements triggered R&D activities, aimed at the development of suitable construction technologies for fast ramped curved coils. The heart of the R&D program is the construction of a 3.9 m long model. The paper discusses the main problems faced during the design and the construction of the cold mass, mainly covering the aspects related to the manufacture.

A Model Dipole for FAIR SIS300: 3D Design of the Mechanical Structure

The FAIR facility, under development at GSI, includes the synchrotron SIS300 (300 Tm rigidity). In order to reach the required high intensities of proton and heavy ion beams, the bending dipole magnets have to be pulsed from the injection magnetic field of 1.5 T up to 4.5 T maximum field at the rate of 1 T/s. These 7.8 m long magnets have cos-theta shaped coils with a 100 mm bore with the particular characteristic to be geometrically curved (the sagitta is 114 mm). The 2D mechanical cross section has been designed in detail: it consists of 3 mm thick laminated stainless steel collars, assembled through keys, and 1 mm thick iron yoke laminations, assembled through large stainless steel C-shaped clamps. This paper analyses some aspects that are intrinsically 3-dimensional: the mechanical behavior of the ends, the effect of the longitudinal pre-stress, the design of the external flange and outer shell.

Bending magnets for the SAGA Storage Ring

The dipole bending magnets (BM) for SR Source Storage Ring (prefecture SAGA, Japan) were designed, manufactured and measured by the Budker INP, Novosibirsk, Russia. The main features of magnetic modeling and magnetic measurements are presented in the paper. The measured basic parameters of the manufactured bending magnets have good agreement with the model simulation.

Sextupole Winding in a Dipole Magnet Gap for a Storage Ring

In special synchrotrons a controllable sextupole field is required in the bending dipole magnets. One of them is NewSUBARU, a 1.5 GeV synchrotron light source. It has inverse dipole (bending) magnets to control the linear momentum compaction factor. It has to have a controllable sextupole at the position of the inverse bend for an independent control of its horizontal chromaticity and its higher order momentum compaction factor while keeping enough dynamic aperture. The inverse bend is a normal conducting C-type magnet whose bending angle, maximum field strength, yoke length and magnet gap are - 8 degrees, 1.554 T, 444 mm and 40 mm, respectively. The height of vacuum chamber in it is 28 mm, smaller than that in a normal bending magnet, while the magnet gaps are the same. This is because the vertical beta function at the inverse dipole is smaller. A pair of water-cooled coil sheets, which produce a sextupole field, are set at the space between the chamber and the pole face. Its thickness, the maximum current and the maximum sextupole field are 4.4 mm, 154 A and 70 T/m/sup 2/, respectively.

Infrared facility at the Canadian light source

The Canadian Light Source (CLS) is constructing two beamlines for Infrared Spectroscopy using synchrotron radiation (IRSR). One will supply mid-Infrared (2–25 μ) light to a Fourier Transform Infrared (FTIR) spectrometer and microscope for biological applications. The second will have a high resolution FTIR spectrometer for gas-phase and surface spectroscopy in the far-Infrared (beyond 25 μ). The Infrared beamlines will use dipole bending magnet radiation from a special bend magnet port design which provides a 50 mrad square acceptance. Issues with the first mirror and photon mask design, as well as the beamline layout and features are discussed.

Design and performance of the infrared beam ports at the Canadian Light Source

The Canadian Light Source is constructing two beamlines for infrared spectroscopy. One will supply mid infrared (2–20 μm) light to a Fourier transform infrared (FTIR) spectrometer and microscope for biological applications. The second will have a vacuum FTIR spectrometer for experiments in the far infrared (beyond 20 μm). Flux and brightness curves for these beam lines are reported. The calculations are made to provide working values for the design, construction, and evaluation of the beamlines. To gauge performance, a comparison is made to other infrared beamlines operating with dipole bending magnets and to a thermal source. Values obtained using standard bend radiation formulas are compared with values obtained using the Synchrotron Radiation Workshop. Issues in the first mirror design are also discussed.

Midinfrared beamline at the National Synchrotron Light Source port U2B

A new infrared beamline has been developed on a conventional dipole bending magnet port of the vacuum ultraviolet ring at the National Synchrotron Light Source. The port provides approximately 12 mrad horizontal and 8 mrad vertical aperture, which limits the useful spectral range to wavelengths less than 20 μm. Though the total flux across the midinfrared is less than that from a globar source, the calculated brightness is at least two orders of magnitude greater. Also, the synchrotron source delivers light in subnanosecond pulses. The developing experimental programs include studies of hydrogen and other materials at extremely high pressures, and time-resolved studies of infrared sensor materials. The measurement results presented here, characterizing the actual brightness advantage and spectroscopic performance, demonstrate the synchrotron’s remarkable advantage for microspectroscopic studies.

Synthesis of the pole shape of the bending magnets for storage rings

A method of pole shape design for a dipole bending magnet is described. The pole shape is derived from the characteristics of the magnet field inside the working region of the magnet aperture. This method is applicable to the design of magnets with large bending radius. A computer code optimizing the parameters of gradient dipole magnets based on the method has been developed. >