Sha Bai

Study of CEPC performance with different collision energies and geometric layouts

The Circular Electron-Positron Collider (CEPC) is one of the largest projects planned for high energy physics in China. It would serve first as a Higgs factory and then upgrade to a hadron collider. In this paper we give the 50 km and 100 km design for both single ring and double ring schemes, including Z boson, W boson and Higgs boson, by using an optimized method. Also, we give the potential of CEPC running at the Z and W poles. We analyse the relationship of luminosity with circumference and filling factor, which gives a way to evaluate the choice of geometry, and compare the nominal performances of CEPC-SPPC, LHC and FCC.

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.

CEPC partial double ring scheme and crab-waist parameters

In order to avoid the pretzel orbit, CEPC is proposed to use partial double ring scheme in CDR. In this paper, a general method of how to make an consistent machine parameter design of CEPC with crab-waist by using analytical expression of maximum beam–beam tune shift and beamstrahlung beam lifetime started from given IP vertical beta, beam power and other technical limitations were developed. FFS with crab sextupoles will be developed and the arc lattice will be redesigned to acheive the lower emittance for crab-waist scheme.

Second Sound Quench Detection on Superconducting Cavities

Second sound is an effective way to detect the quench position on superconducting cavity. A second sound quench site detection system is under developing for the PAPS. High gradient is very important for super conducting cavity, however it may be limited by quench on the cavity high field region. Quench can be caused by various reasons. To locate the position is the key to reveal the mysteries of quench. Now we are developing the quench position detection system by RTD sensors such as Cernox and OST sensors. INTRODUCTION Second sound is an effective way to detect the quench position on superconducting cavity. It was first used to detect the quench position on the SC split-ring resonators at ANL by a germanium resistor sensor [1]. Oscillating Superleak Transducers (OST) were used to locate the quench site of the 1.3 GHz 9-cell cavity at Cornell University [2]. Later after that second sound quench site detection of SC cavity by OST was widely used on the world. Second sound detection was also used in standard dressed TESLA-Shape SRF cavity at DESY [3]. Other types of sensor were also developed to detect second sound. For example, transition edge sensors was used in second sound test [4, 5]. A second sound quench site detection system is under developing for the PAPS. We chose the highly sensitive thermometers such as germanium bare chip resistor or Cernox bare chip resistor and OST as the second sound detection sensors. Tests with SC cavity and heater in liquid helium at 2K were taken.

Beam loss background and collimator design in CEPC double ring

The Circular Electron Positron Collider (CEPC) is a proposed Higgs factory with center of mass energy of 240GeV to measure the properties of Higgs boson and test the standard model accurately. Beam loss background in detectors is an important topic at CEPC. Radiative Bhabha scattering and beamstrahlung effects are dominant mechanism of the beam induced backgrounds at CEPC due to the beam lifetime. In this paper, we evaluated the beam loss background in simulation and designed a series of collimators to suppress the radiation level on the machine and the detector.

Lattice design for the CEPC double ring scheme

A future Circular Electron Positron Collider (CEPC) has been proposed by China with the main goal of studying the Higgs boson. Its baseline design, chosen on the basis of its performance, is a double ring scheme; an alternative design is a partial double ring scheme which reduces the budget while maintaining an adequate performance. This paper will present the collider ring lattice design for the double ring scheme. The CEPC will also work as a W and a Z factory. For the W and Z modes, except in the RF region, compatible lattices were obtained by scaling down the magnet strength with energy.

Optics design for CEPC double ring scheme

The CEPC is a future Circular Electron and Positron Collider proposed by China to mainly study the Higgs boson. Its baseline design is a double ring scheme and an alternative design is a partial double ring scheme. This paper will present the optics design for the main ring of the double ring scheme. The CEPC will also work as a W and Z factory. Compatible optics designs for a W and a Z modes will be presented as well.

100 km CEPC parameters and lattice design

In this paper, a consistent calculation method for the CEPC parameter choice with a crab waist scheme is reported. A crosscheck of luminosity with beam–beam simulations has been done. With this new scheme, a higher Higgs luminosity (+170%) can be reached while keeping Pre-CDR beam power or the beam power (19 MW) can be reduced while keeping the same Pre-CDR luminosity. CEPC is compatible with W and Z experiment. The luminosity for Z is at the level of 1035cm−2s−1. Requirement for energy acceptance of Higgs has been reduced to 1.5% by enlarging the ring to 100 km. The arc optics and the Final Focus System (FFS) with crab sextupoles have been designed, and also some primary Dynamic Aperture (DA) results were introduced.

CEPC booster design study

In September 2012, Chinese scientists proposed a Circular Electron Positron Collider (CEPC) in China at 240 GeV center-of-mass energy for Higgs studies. The booster provides 120 GeV electron and positron beams to the CEPC collider for top-up injection at 0.1 Hz. The design of the full energy booster ring of the CEPC is a challenge. The ejected beam energy is 120 GeV and the injected beam energy is 6 GeV. In this paper we describe two alternative schemes, the wiggler bend scheme and the normal bend scheme. For the wiggler bend scheme, we propose to operate the booster ring as a large wiggler at low energy and as a normal ring at high energy to avoid the problem of very low dipole magnet fields. For the normal bend scheme, we implement the orbit correction to correct the earth field.

Design study of CEPC Alternating Magnetic Field Booster

The CEPC is a next generation circular e+ ecollider proposed by China. The design of the full energy booster ring of the CEPC is especially challenging. The ejected beam energy is 120 GeV, but that of the injected beam is only 6 GeV. In a conventional approach, the low magnetic field of the main dipole magnets creates problems. We propose operating the booster ring as a large wiggler at low beam energies and as a normal ring at high energies to avoid the problem of very low dipole magnet fields.