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![Temperature dependence of the muon spin relaxation rates from zero field measurements and from the bulk static susceptibilities measured in an applied field of 0.01 T for YbMgGaO 4 [25].](publication/328794958/figure/fig2/AS:690512793182212@1541642487942/Temperature-dependence-of-the-muon-spin-relaxation-rates-from-zero-field-measurements-and.png)
Temperature dependence of the muon spin relaxation rates from zero field measurements and from the bulk static susceptibilities measured in an applied field of 0.01 T for YbMgGaO 4 [25].
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A muon facility—EMuS (Experimental Muon Source)—at China Spallation Neutron Source (CSNS) has been studied since 2007. CSNS, which is designed to deliver a proton beam power of 100 kW at Phase-I, and will serve multidisciplinary research based on neutron scattering techniques, has just completed construction, and is ready to open to general users f...
Citations
... The upgrading project (CSNS-II), which will start construction in 2023, will boost the beam power to 500 kW by means of higher beam intensity. The Experimental Muon Source (EMuS) was proposed to be constructed at CSNS-II for muon science [17,18], which will be a standalone pulsed muon facility and uses about 5% (or 25 kW) of the total proton beam power. Two different schemes for the EMuS have been studied, the so-called simplified scheme [19] which was planned to be built first and the baseline scheme as the upgrade. ...
A new muon beam facility, called the Experimental Muon Source (EMuS), was proposed for construction at the China Spal-lation Neutron Source (CSNS). The design of the complex muon beamlines for the EMuS baseline scheme, which is based on superconducting solenoids, superferric dipoles and room-temperature magnets, is presented herein. Various muon beams, including surface muons, decay muons and low energy muons, have been developed for multipurpose applications. The optics design and simulation results of the trunk beamline and branch beamlines are presented. With a proton beam power of 25 kW at a standalone target station that consists of a conical graphite target and high-field superconducting solenoids, the muon beam intensity in the trunk beamline varies from 10 7 /s for surface muons to 10 10 /s for high-momentum decay muons. And at the endstations, these values vary from 10 5 /s for surface muons to 10 8 /s for decay muons.
... The upgrading project (CSNS-II), which will start construction in 2023, will boost the beam power to 500 kW by means of higher beam intensity. The Experimental Muon Source (EMuS) was proposed to be constructed at CSNS-II for muon science [17,18], which will be a standalone pulsed muon facility and uses about 5% (or 25 kW) of the total proton beam power. Two different schemes for the EMuS have been studied, the so-called simplified scheme [19] which was planned to be built first and the baseline scheme as the upgrade. ...
A new muon beam facility, called the Experimental Muon Source (EMuS), was proposed for construction at the China Spallation Neutron Source (CSNS). The design of the complex muon beamlines for the EMuS baseline scheme, which is based on superconducting solenoids, superferric dipoles and room-temperature magnets, is presented herein. Various muon beams, including surface muons, decay muons and low energy muons, have been developed for multipurpose applications. The optics design and simulation results of the trunk beamline and branch beamlines are presented. With a proton beam power of 25 kW at a standalone target station that consists of a conical graphite target and high-field superconducting solenoids, the muon beam intensity in the trunk beamline varies from 10 ⁷ /s for surface muons to 10 ¹⁰ /s for high-momentum decay muons. And at the endstations, these values vary from 10 ⁵ /s for surface muons to 10 ⁸ /s for decay muons.
... A muon source was proposed in Phase II of China Spallation Neutron Source (CSNS) [8][9][10][11][12]. Approximately 4% of the proton beam power (500 kW, 1.6 GeV, 25 Hz) will be assigned to the muon source. ...
A new muon source has been proposed to conduct muon spin rotation/relaxation/resonance ($\mu$SR) measurements at China Spallation Neutron Source (CSNS). Only 1 Hz of the CSNS proton beams (25 Hz in total) will be allocated for muon production. To make better use of muons in every pulse, an ultrahigh-array $\mu$SR spectrometer (UHAM) with thousands of detector channels is under design. Due to such a high granularity of detectors, multiple counting events generated from particle scattering or spiral motions of positrons in a strong longitudinal field should be carefully considered in the design. Six different structures were modeled and simulated based on two types of angular orientations (parallel arrangement and pointing arrangement) and three kinds of spectrometer geometries (cylinder, cone and sphere). A quality factor, $Q$, was proposed to evaluate the performance of these structures by integrating their impacts on the overall asymmetry, the counting rate and the percentage of multiple counts. According to the simulation, the conical structure with detectors pointing to the sample has the highest $Q$ in both zero field and longitudinal field. The results also show that all kinds of structures cannot be operated under strong longitudinal fields with a strength over 2 T. The full simulation of a $\mu$SR spectrometer can provide good guidance for the construction of the UHAM in the upcoming upgrade of CSNS.
... In Switzerland, PSI is investigating new high-intensity muon beams (HIMBs) with a surface muon rate up to 10 10 =s based on its new target M (so-called target H) [22][23][24]. In China, the first muon source experimental muon source (EMuS) is going to is going to use solenoids to transport high-intensity surface muon and pion beams in the baseline scenario [25]. ...
The μE4-LEM beamline at Paul Scherrer Institute (PSI, Switzerland) is a special muon beamline combining the hybrid-type surface muon beamline μE4 with the low-energy muon (LEM) facility and delivers μ^{+} with tunable energy up to 30 keV for low-energy muon spin rotation (LE-μSR) experiments. We investigate a possible upgrade scenario for the surface muon beamline μE4 by replacing the last set of quadrupole triplets with a special solenoid to obtain 1.4 times the original beam intensity on the LEM muon moderator target. In order to avoid the muon beam intensity loss at the LEM spectrometer due to the stray magnetic field of the solenoid, three kinds of solenoid models have been explored and the stray field of the solenoid at the LEM facility is finally reduced to the magnitude of the geomagnetic field. A more radical design, “Super-μE4,” has also been investigated for further increasing the brightness of the low-energy muon beam, where we make use of the current μE4 channel and all sets of quadrupole triplets are replaced by large aperture solenoids. Together with the new slanted muon target E, at least 2.9 times the original muon beam intensity can be expected in the Super-μE4 beamline. Our work demonstrates the feasibility of upgrading surface muon beamlines by replacing quadrupole magnets with normal-conducting solenoids, resulting in higher muon rates and smaller beam spot sizes.
... EMuS was foreseen initially to take place at China Spallation Neutron Source phase-I and then at phase-II (CSNS-II) [1,2]. At CSNS-II, the total proton beam power available for the spallation target and the EMuS project is increased from 100 kW to 500 kW and from 5 kW to 25 kW, respectively. ...
... where m − i Γ 2 ik is a 2 × 2 Hamiltonian (mass matrix) with non-zero off-diagonal terms originating from the ∆L = 2 interactions. CPT-invariance dictates that the masses and widths of the muonium and anti-muonium are the same, so m 11 = m 22 , Γ 11 = Γ 22 . In what follows, we assume CP-invariance of the ∆L µ = 2 interaction. ...
... A 100 kW pulsed proton accelerator with the beam energy of 1.6 GeV and the repetition frequency of 25 Hz has been running at China Spallation Neutron Source (CSNS) in the YGA Bay area since 2018. An upgrade of the beam power toward 500 kW has been approved with a working package specifically reserved for the construction of an experimental muon source (EMuS) [22]. Meanwhile, China Initiative Accelerator Driven sub-critical System (CiADS) will offer continous proton beam with the power at the Megawatt level. ...
The spontaneous muonium to antimuonium conversion is one of the interesting charged lepton flavor violation processes. It serves as a clear indication of new physics and plays an important role in constraining the parameter space beyond Standard Model. MACE is a proposed experiment to probe such a phenomenon and expected to enhance the sensitivity to the conversion probability by more than two orders of magnitude from the current best upper constraint obtained by the PSI experiment two decades ago. Recent developments in the theoretical and experimental aspects to search for such a rare process are summarized.
... For example, at the China Spallation Neutron Source (CSNS) where the main applications are based on neutron scattering techniques, the rapid cycling synchrotron (RCS) delivers a proton beam of two bunches per pulse, and the full bunch length at the extraction is about 105 ns. However, the other experimental platforms, such as the Back-n white neutron source [1] and the EMuS muon source [2], demand shorter bunches. Therefore, a theoretical study to produce a proton beam with shorter bunches was carried out during the construction period of the CSNS facility [3]. ...
Short bunch proton beams are of great significance for the applications of white neutron beams and muon beams. The accelerator complex of the China Spallation Neutron Source (CSNS) was designed to support the applications mainly based on neutron scattering techniques where the proton pulse length is not very sensitive. Some theoretical and experimental studies have been performed to see if one can extract a short-bunch proton beam by bunch rotation from the rapid cycling synchrotron (RCS) at CSNS. The experimental results at RCS have evidently displayed the bunch lengthening and rotation process, which demonstrates the effectiveness of this method even with a very short available time for the rf gymnastic processes and a high-intensity beam. With a beam power of 50 kW and normal longitudinal emittance at the injection, the proton beam with a bunch length of about 53% with respect to the one in the normal operation mode was obtained and transported to the spallation target. With a reduced longitudinal emittance at injection and the beam power of 30 kW, the shortest extraction bunch length obtained is about 26% of the one in the normal operation mode. Different machine settings have also been tested to show the impact of the desynchronization between the rf and magnetic fields, the influence of the nonadiabatic rise time, and the adiabatic decay time of the rf voltage on the extraction bunch length. The experimental results are well consistent with the theoretical and simulated ones. It is interesting to observe that space charge has a beneficial effect on the bunch lengthening which will result in a shorter bunch at the extraction with the later bunch rotation. The controlled desynchronization method between the rf and magnetic fields in an RCS was also proven successful.
... Due to the lack of powerful proton accelerator before, there is no muon source in China. The Experimental Muon Source (EMuS) project [2][3] at China Spallation Neutron Source (CSNS) [4] in Dongguan is planned to develop its first muon source in China. It will be designed to provide both a low energy surface muon beam and a high energy decay muon beam for muon science and especially Muon Spin Rotation (µSR) experiments. ...
... The proton beam can be exploited for generating muons and fast neutrons, which can be applied to fundamental research on nuclear and materials sciences. The experimental muon source (EMuS) is proposed at the CSNS in order to explore mainly muon science and especially muon spin rotation/relaxation/resonance (μSR) experiments for material science, and secondary for low energy neutrino cross sections [2]. In addition, the EMuS can provide a platform for accelerator and targetry R&D of the next-generations high proton beam power muon and neutrino beams facilities. ...
The EMuS project foreseen for muon science and neutrino physics is utilizing a superconducting solenoid for muon and pion capture, and is proposed at China Spallation Neutron Source (CSNS). For the optimal particles collection efficiencies, an adiabatic magnetic field from 5 T to 2.2 T along the central axis of the solenoid is produced by the solenoid. The superconducting solenoid is composed of four windings and an iron yoke. The iron yoke is arranged for flux returning and magnetic field shielding. Two conductor options for the windings, the aluminum stabilized NbTi Rutherford cable and the NbTi monolith wire are compared from the mechanical structure and radiation performance. The results of the mechanical analysis from ANSYS show that the excitation stress is suitable. But the results of the radiation analysis from FLUKA monte-carlo show that the recovery of the Residual Resistivity Ratios (RRR) is necessary for the superconductor's stabilizers. The recovery cycle of the aluminum stabilizer and the monolith wire solenoids are three months and one year respectively. However, the RRR of copper for the monolith wire magnet will be less than 50, after 12 years continuous running, which is shorter than the EMuS lifetime of 30 years. Therefore, the aluminum stabilized NbTi Rutherford cables are chosen to fabricate the windings.
... This proves again that the discovery of new concepts goes in parallel with combining different methods or the use of new methods. This is reviewed in [1], showing how muons with high intensity from a new muon source at the Chinese spallation source will bring new insights in the field of magnetic materials and magnetism. By combining atom probe tomography (APT) with quasielastic neutron scattering using N(R)SE, the evolution of the spin glass phase in the presence of ferro-and antiferromagnetic clusters in the cluster spin glass Fe17.8Cr82.2 has been characterized in [2]. ...
Welcome to the special issue of Quantum Beam Science on “Magnetic Materials and Magnetism” [...]
