Future High-energy Accelerators Research Articles

Conceptual Design of a 20 T Hybrid Cos-Theta Dipole Superconducting Magnet for Future High-Energy Particle Accelerators

High energy physics research will need more and more powerful circular accelerators in the next decades. It is therefore desirable to have dipole magnets able to produce the largest possible magnetic field, in order to keep the machine diameter within a reasonable size. A 20 T dipole is considered a desired achievement since it would allow the construction of an 80 km machine, able to circulate 100 TeV proton beams. In order to reach 20 T, a hybrid Low-Temperature Superconductor (LTS) - High-Temperature Superconductor (HTS) magnet is needed, since LTS technology is presently limited to ∼16 T for accelerator magnet applications. In this paper, we present the design of a 6 layers 20 T hybrid dipole magnet using Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn (LTS) and Bi2212 (HTS). We show that it is possible to achieve this magnetic field with accelerator field quality, with sufficient margin on a realistic conductor, keeping the stresses within safe limit, avoiding conductor degradation.

Study of hydrodynamic-tunnelling effects induced by high-energy proton beams in graphite

The design and assessment of machine-protection systems for existing and future high-energy accelerators comprises the study of accidental beam impact on machine elements. In case of a direct impact of a large number of high-energy particle bunches in one location, the damage range in the material is significantly increased due to an effect known as hydrodynamic tunnelling. The effect is caused by the beam-induced reduction of the material density along the beam trajectory, which allows subsequent bunches to penetrate deeper into the target. The assessment of the damage range requires the sequential coupling of an energy-deposition code, like FLUKA, and a hydrodynamic code, like Autodyn. The paper presents the simulations performed for the impact of the nominal LHC beam at 7 TeV on a graphite target. It describes the optimisation of the simulation setup and the required coupling workflow. The resulting energy deposition and the evolution of the target density are discussed.

A Preliminary Study on a New Epoxy Resin IR-3 for High-Field Superconducting Magnet Applications

Epoxy resins are commonly used in high field superconducting magnets for electrical insulation and mechanical reinforcement. However, many of the epoxy systems for vacuum pressure impregnation (VPI) techniques show drawbacks like easy cracking at low temperatures, short pot life, and/or low glass transition temperatures <formula><tex>$(T_g)$</tex></formula>. High-field dipole magnets are under development at the Institute of High Energy Physics (IHEP) for the pre-study of future high-energy accelerators. Finding the most appropriate epoxy is critically important. Herein, a new epoxy resin (named IR-3) is developed. Its potting properties including thermal shock, viscosity, <formula><tex>$T_g$</tex></formula>, and mechanical strength before and after radiation are presented and were compared with CTD-101K which is mostly used in accelerator magnets. Additionally, the thermal and electrical characteristics of high-temperature superconductor (HTS) coils encapsulated with these epoxies were also investigated. The results show that IR-3 is a promising encapsulating material for impregnating HTS coils and has the potential application in high field accelerator magnets

First performance test of the iron-based superconducting racetrack coils at 10 T

Iron-based superconducting (IBS) racetrack coils were firstly fabricated by using 100-m 7-filamentary Ba1-xKxFe2As2 (Ba122) tapes at the Institute of High Energy Physics, Chinese Academy of Sciences (IHEP, CAS). The IBS tape was wound in parallel with stainless steel tape to withstand the high tensile hoop stress under high magnetic field. After the heat treatment, the coils were impregnated with epoxy resin. Then the IBS coils were tested in a low-temperature superconducting Common-Coil dipole magnet which provided a maximum background field of 10 T at 4.2 K. Most importantly, the best IBS racetrack coil quenched at 4.2 K and 10 T with an operating current of 65 A, which is still as high as 86.7% of critical current of the short sample at 10 T. The details of the fabrication process and performance test results were presented in this paper. The performance test demonstrated the IBS conductor is a promising candidate for the application of high field magnets especially for future high-energy accelerators.

Cooling Hadron Beams with Electron Pulses

Pulsed electron beams can be used to cool beams of ions and protons circulating in a hadron storage ring—a promising development for future high-energy accelerators.

Biomedical Research Programs at Present and Future High-Energy Particle Accelerators.

Biomedical applications at high-energy particle accelerators have always been an important section of the applied nuclear physics research. Several new facilities are now under constructions or undergoing major upgrades. While the main goal of these facilities is often basic research in nuclear physics, they acknowledge the importance of including biomedical research programs and of interacting with other medical accelerator facilities providing patient treatments. To harmonize the programs, avoid duplications, and foster collaboration and synergism, the International Biophysics Collaboration is providing a platform to several accelerator centers with interest in biomedical research. In this paper, we summarize the programs of various facilities in the running, upgrade, or construction phase.

Energy dependence of the efficiency of high-energy negatively charged particle beam deflection by planar channeling in a bent crystal

The study of planar channeling of high-energy negatively charged particles in bent crystals was carried out. The value of the critical radius of planar channeling in the Doyle–Turner approximation for the atomic potential is determined. The dependence of the maximum angle at which a given fraction of beam particles could be deflected by means of planar channeling in a bent crystal on the particle energy was found. We identified the ideal parameters for the exploitation of planar channeling for negatively charged particle beam deflection by planar channeling in a bent crystal at current and future high-energy accelerators, e.g., SLAC, MAMI, ILC or muon colliders.

Impact of Flux Jumps on High-Precision Powering of Nb3Sn Superconducting Magnets

Nb3Sn superconducting magnets represent a technology enabler for future high-energy particle accelerators. A possible impediment, though, comes from flux jumps that, so far, could not be avoided by design unlike for NbTi technology. However, the impact of flux jumps on the magnet powering has not been properly investigated to date. Flux jumps appear during current ramps at relatively low value of current and tend to disappear towards nominal current. They are usually detected as voltage jumps between different magnet coils but they might also produce overall voltage jumps across the magnet electrical terminals. Such jumps might perturb the power converter feedback control loop and therefore potentially jeopardize its precision performance during energy ramps. This work aims at: (i) presenting preliminary experimental test results on some HL-LHC Nb3Sn model and prototype magnets, and (ii) attempting to build a simplified electrical model of the flux jumps, with focus only at its interaction with the power converter feedback control loop. Such a work is a starting point for outlining possible power converters control strategies able to minimize flux jumps impact on high-precision powering of Nb3 Sn superconducting magnets.

On the compatibility of porous surfaces with cryogenic vacuum in future high-energy particle accelerators

Recently, pulsed laser processing of Cu samples has been demonstrated to produce rough surfaces whose structuring at the nanoscale ensures an impressive reduction of the secondary electron yield. This feature has an undoubted appealing for applications in future high energy particle accelerators. However, the effective application of such laser treated surfaces in this context requires a rigorous evaluation of their vacuum behavior, especially when used at cryogenic temperatures. To this aim, here, we compare thermal programmed desorption between 20 and 70 K by dosing Ar multilayers of different thicknesses on a laser treated copper substrate and on its flat counterpart. Our results highlight that the spongelike structural features confer to the laser treated sample's non-negligible effects due to the gas-substrate interaction. This results in a much vaster and higher desorption temperature range with respect to what is observed from the flat substrates. This evidence could render it very difficult to find temperature intervals for which detrimental vacuum transients could be avoided in the cryogenic beam pipes. On these bases, although the electron cloud mitigation efficiency has been settled, before definitely including porous surfaces in any cryogenic machine design, all the consequences of having a rough rather than a flat wall should be carefully evaluated.

Comprehensive study of beam focusing by crystal devices

This paper is devoted to an experimental study of focusing and defocusing positively charged particle beams with the help of specially bent single crystals. Four crystals have been fabricated for this purpose. The studies have been performed at the CERN SPS in 400 GeV/c proton and 180 GeV/c pion beams. The results of measurements of beam envelopes are presented. The rms size of the horizontal profile at the focus was 5–8 times smaller than at the exit of the crystals. The measured focal lengths were 4–21 m. The results of measurements are in good agreement with calculations. Possible applications of focusing crystals in present and future high energy accelerators are discussed.5 MoreReceived 30 June 2017DOI:https://doi.org/10.1103/PhysRevAccelBeams.21.014702Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBeam optics transportAccelerators & Beams

Mechanical Effects of the Nonuniform Current Distribution on HTS Coils for Accelerators Wound With REBCO Roebel Cable

Future high-energy accelerators will need very high magnetic fields in the range of 20 T. The EuCARD-2 WP10 Future Magnets collaboration is aiming at testing HTS-based Roebel cables in an accelerator magnet. The demonstrator should produce around 17 T, when inserted into the 100-mm aperture of Feather-M2 13-T outsert magnet. HTS Roebel cables are assembled from meander-shaped REBCO-coated conductor tapes. In comparison with fair level of uniformity of current distribution in cables made out of round Nb-Ti or Nb 3 Sn strands, current distribution within the coils wound from Roebel cables is highly nonhomogeneous. It results in nonuniform electromagnetic force distribution over the cable that could damage the very thin REBCO superconducting layer. This paper focuses on the numerical models to describe the effect of the nonhomogeneous current distribution on stress distribution in the demonstrator magnet designed for the EuCARD-2 project. Preliminary results indicate that the impregnation bonding between the cable glass fiber insulation and layer-to-layer insulation plays a significant role in the pressure distribution at the cable edges. The stress levels are safe for Roebel cables. Assuming fully bonded connection at the interface, the stresses around the edges are reduced by a large factor.

Partially Insulated Twisted Stacked Cable for HTS Insert of a Particle Accelerator

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.

Critical Current Characterization of Commercial REBCO Coated Conductors at 4.2 and 77 K

Superconducting magnets with magnetic fields of approximately 20 T will be needed for future high-energy accelerators, such as the future circular collider at CERN and/or the Muon Collider in the United States. Such field strengths exceed the levels achievable using low-temperature superconductors, such as Nb 3 Sn or Nb 3 Al. Only high-temperature superconductors can currently achieve such high field strengths. However, there has been a little research published on the electrical transport properties of REBCO coated conductors in high-field low-temperature magnet applications. Thus, we have started the critical current characterization of commercially available REBCO-coated conductors in fields of up to 18 T at 4.2 K. This paper reports some of the critical current measurement results at 4.2 and 77 K for conductors from four different manufacturers: Fujikura Ltd.; SuNAM Co. Ltd.; SuperOx Japan LLC; and SuperPower Inc.

Influence of incoherent scattering on stochastic deflection of high-energy negative particle beams in bent crystals

An investigation on stochastic deflection of high-energy negatively charged particles in a bent crystal was carried out. On the basis of analytical calculation and numerical simulation it was shown that there is a maximum angle at which most of the beam is deflected. The existence of a maximum, which is taken in the correspondence of the optimal radius of curvature, is a novelty with respect to the case of positively charged particles, for which the deflection angle can be freely increased by increasing the crystal length. This difference has to be ascribed to the stronger contribution of incoherent scattering affecting the dynamics of negative particles that move closer to atomic nuclei and electrons. We therefore identified the ideal parameters for the exploitation of axial confinement for negatively charged particle beam manipulation in future high-energy accelerators, e.g., ILC or muon colliders.

Systematical study on superconducting radio frequency elliptic cavity shapes applicable to future high energy accelerators and energy recovery linacs

Elliptic cavities at medium- and high-$\ensuremath{\beta}$ range are receiving broader use in the particle accelerator applications. Optimizing the shape of these cavities is a complex and demanding process. In this paper we propose an optimization approach to minimize the ratio of peak magnetic field to the acceleration field ${H}_{\text{pk}}/{E}_{\text{acc}}$ while keeping the ratio of peak surface electric field to the accelerating field ${E}_{\text{pk}}/{E}_{\mathrm{acc}}$, aperture radius and wall slope angle $\ensuremath{\alpha}$ at some permitted values. We show that it is possible to substantially vary the cavity geometry without violating the constraints or deteriorating the objective of the optimization. This gives us freedom in designing the geometry to overcome problems such as multipactor while maintaining the minimal ${H}_{\text{pk}}/{E}_{\mathrm{acc}}$. The optimization is then performed to find a set of optimized geometries with minimum ${H}_{\text{pk}}/{E}_{\mathrm{acc}}$ for different $\ensuremath{\beta}$'s ranging from 0.4 to 1, different peak surface electric fields, wall slope angles and aperture radii. These data could be generally used as a suitable starting point in designing elliptic cavities.

Accelerator-Quality HTS Dipole Magnet Demonstrator Designs for the EuCARD-2 5-T 40-mm Clear Aperture Magnet

Future high-energy accelerators will need very high magnetic fields in the range of 20 T. The Enhanced European Coordination for Accelerator Research and Development (EuCARD-2) Work Package 10 is a collaborative push to take high-temperature superconductor (HTS) materials into an accelerator-quality demonstrator magnet. The demonstrator will produce 5 T stand alone and between 17 and 20 T when inserted into the 100-mm aperture of a Fresca-2 high-field outsert magnet. The HTS magnet will demonstrate the field strength and the field quality that can be achieved. An effective quench detection and protection system will have to be developed to operate with the HTS superconducting materials. This paper presents a ReBCO magnet design using a multistrand Roebel cable that develops a stand-alone field of 5 T in a 40-mm clear aperture and discusses the challenges associated with a good field quality using this type of material. A selection of magnet designs is presented as the result of the first phase of development.

Instrumental developments for in situ breakdown experiments inside a scanning electron microscope

Electrical discharges in accelerating structures are one of the key issues limiting the performance of future high energy accelerators such as the Compact Linear Collider (CLIC). Fundamental unders ...

Effect of temperature on ion motion in future plasma wakefield accelerators

We study the effect of plasma temperature on ion motion in a plasma wakefield accelerator with parameters typical of a future high-energy accelerator. We show that the collapse of the plasma ions caused by the extremely high fields of ultradense electron bunches can be prevented only by a very high plasma ion temperature.

Laser acceleration and its future

Laser acceleration is based on the concept to marshal collective fields that may be induced by laser. In order to exceed the material breakdown field by a large factor, we employ the broken-down matter of plasma. While the generated wakefields resemble with the fields in conventional accelerators in their structure (at least qualitatively), it is their extreme accelerating fields that distinguish the laser wakefield from others, amounting to tiny emittance and compact accelerator. The current research largely falls on how to master the control of acceleration process in spatial and temporal scales several orders of magnitude smaller than the conventional method. The efforts over the last several years have come to a fruition of generating good beam properties with GeV energies on a table top, leading to many applications, such as ultrafast radiolysis, intraoperative radiation therapy, injection to X-ray free electron laser, and a candidate for future high energy accelerators.

The DREAM project—Towards the ultimate in calorimetry

High-precision jet spectroscopy will be increasingly important in future high-energy accelerator experiments, particularly at a linear e + e - collider. The dual-readout technique makes it possible to meet and exceed the requirements on calorimeter performance in experiments at such a collider. The DREAM Collaboration is exploring the limits of the possibilities offered by this technique, by systematically eliminating the limiting factors, one after the other. Powerful tools in this context are the simultaneous measurement of scintillation light and Cherenkov light generated in the shower development process, and a detailed measurement of the time structure of the signals. In this talk, the latest results of this generic detector R&D project are presented. In particular, I report on the first tests of a hybrid dual-readout calorimeter system, in which a BGO crystal matrix served as the electromagnetic section.