Jingyu Tang

MOMENT: a muon-decay medium-baseline neutrino beam facility

Neutrino beam with about 300 MeV in energy, high-flux and medium baseline is considered a rational choice for measuring CP violation before the more powerful Neutrino Factory will be built. Following this concept, a unique neutrino beam facility based on muon-decayed neutrinos is proposed. The facility adopts a continuous-wave proton linac of 1.5 GeV and 10 mA as the proton driver, which can deliver an extremely high beam power of 15 MW. Instead of pion-decayed neutrinos, unprecedentedly intense muon-decayed neutrinos are used for better background discrimination. The schematic design for the facility is presented here, including the proton driver, the assembly of a mercury-jet target and capture superconducting solenoids, a pion/muon beam transport line, a long muon decay channel of about 600 m and the detector concept. The physics prospects and the technical challenges are also discussed.

CEPC partial double ring lattice design and SPPC lattice design

In this paper, we introduce the layout and lattice design of Circular-Electron-Positron-Collider (CEPC) partial double ring scheme and the lattice design of Super-Proton-Proton-Collider (SPPC). The baseline design of CEPC is a single beam-pipe electron positron collider, which has to adopt pretzel orbit scheme and it is not suitable to serve as a high luminosity Z factory. If we choose partial double ring scheme, we can get a higher luminosity with lower power and be suitable to serve as a high luminosity Z factory. In this paper, we discuss the details of CEPC partial double ring lattice design and show the dynamic aperture study and optimization. We also show the first version of SPPC lattice although it needs lots of work to do and to be optimized.

Status of CSNS Project

The China Spallation Neutron Source (CSNS) accelerator is designed to accelerate proton beam pulses to 1.6 GeV at 25 Hz repetition rate, striking a solid metal target to produce spallation neutrons. The accelerator provides a beam power of 100 kW on the target in the first phase and then 500 kW in the second phase by increasing the average beam intensity 5 times while raising the linac output energy. The project construction has been formally launched in 2011 and it is planned to complete the project in March 2018. It is one of the high intensity proton accelerator projects in the world and it imposes a great challenge to Chinese accelerator community. This presentation will cover the status and challenges of the CSNS project.

Rapid Cycling Synchrotrons and Accumulator Rings for High-Intensity Hadron Beams

Boosted by the needs in high-energy physics and nuclear physics and also multidisciplinary applications, high-intensity proton synchrotrons and accumulator rings have been developed quickly around the world over the last 30 years. New projects and plans are proposed with even higher beam power. The proton beam power has increased from less than 10 kW in the 1970s to about 1 MW level today, and the required beam power in the coming decade is a few MW. This article reviews the achievements in designing and constructing rapid cycling synchrotrons (RCSs) and accumulator rings (ARs) and the future development trends, principally on proton beams but also including heavy ion beams. It presents the evolution of RCS and AR machines, todays design philosophy, relevant accelerator physics, and also state-of-the-art accelerator technology.

Resonant Slow Extraction in Synchrotrons by Using Anti-symmetric Sextupole Fields

Abstract This paper proposes a novel method for resonant slow extraction in synchrotrons by using special anti-symmetric sextupole fields, which can be produced by a special magnet structure. The method has potential in applications demanding very stable slow extraction from synchrotrons. Our studies show that slow extraction at the half-integer resonance by using an anti-symmetric sextupole field has some advantages compared to the standard sextupole field, which is widely used in the slow extraction method. One advantage is that it can work at a more distant tune from the resonance, so that it can reduce significantly the intensity variation of the extracted beam which is mainly caused by the ripples of magnet power supplies. Studies by both the Hamiltonian theory and numerical simulations show that the stable region near the half-integer resonance by anti-symmetric sextupole field is much smaller and flatter than the one by standard sextupole field at the third-order resonance. The particles outside the region will be driven out in two possible directions in quite a short transit time but with spiral steps similar to the third-order resonant extraction. By gradually increasing the field strength, the beam can be extracted with intensity more homogeneous than by the usual third-order resonant method, because of both smaller intensity variation and spike in the beginning spill. With the same field strength and tune distance to the resonance, the change in the stable region area due to the working point variation in the case of the anti-symmetric sextupole is about 1/14 of the one for the standard sextupole. Detailed studies including beam dynamic behaviors near other resonances, expression of the field in polynomial expansion, influence of 2-D field error, half-integer stop-band, and resonant slow extraction using a quadrupole field are also presented.

Transverse profile expansion and homogenization at target for the injector Scheme- I test stand of China-ADS*

For the injector Scheme- I test stand of the China-ADS (Accelerator Driven subcritical System), a beam with the maximum power of 100 kW will be produced and transported to the beam dump. To solve the very high thermal load problem at the dump, two measures are taken to deal with the huge power density at the target. One is to enlarge the contact area between the beam and the target, and this is to be accomplished by expanding the beam profile at the target and using slanted target plates. The other is to produce a more homogenous beam profile at the target to minimize the maximum power density. Here the beam dump line is designed to meet the requirement of beam expansion and homogenization at 3 different energies (3.2 MeV, 5 MeV and 10 MeV), and the step-like field magnets are employed for the beam spot homogenization. Taking into account the fact that the space charge effects,are very strong at such low beam energies, the simulations have included space charge effects and errors which show that the beam line can meet the requirements very well. In the meantime, the alternative beam design using standard multipole magnets is also presented.

Design and Prototyping of a Step-Like Field Magnet

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.

Beamline design of EMuS - the first Experimental Muon Source in China

We report the beamline design of the Experimental Muon Source (EMuS) project in China. Based on the 1.6 GeV/100 kW proton accelerator at the Chinese Spallation Neutron Source (CSNS), EMuS will extract one bunch from every 10 double-bunch proton pulses to hit a stand-alone target sitting in a superconducting solenoid, and the secondary muons/pions are guided to the experimental area. The beamline is designed to provide both a surface muon beam and a decay muon beam, so that various experiments such as muSR applications and particle/nuclear physics experiments can be conducted. In this work we present the conceptual design and simulation of the beamlines, and discuss the future aspects of the project.

Muon-decay medium- baseline neutrino beam facility, Phys. Rev. ST Accel. Beams

Neutrino beam with about 300 MeV in energy, high-flux and medium baseline is considered a rational choice for measuring CP violation before the more powerful Neutrino Factory will be built. Following this concept, a unique neutrino beam facility based on muon-decayed neutrinos is proposed. The facility adopts a continuous-wave proton linac of 1.5 GeV and 10 mA as the proton driver, which can deliver an extremely high beam power of 15 MW. Instead of pion-decayed neutrinos, unprecedentedly intense muon-decayed neutrinos are used for better background discrimination. The schematic design for the facility is presented here, including the proton driver, the assembly of a mercury-jet target and capture superconducting solenoids, a pion/muon beam transport line, a long muon decay channel of about 600 m and the detector concept. The physics prospects and the technical challenges are also discussed.