TY - CONF AU - Wu, J. AU - Qin, Q. AU - Zhang, Y. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - Diffusion Map Analysis in High Energy Storage Ring Based e⁺/e⁻ Collider J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - In a very high energy e⁺/e⁻ storage ring collider, e.g. Circular Electron Positron Collider (CEPC), the dynamic aperture is limited by the strong synchrotron radiation especially in the vertical direction. Some tracking results also shows that the beam lifetime does not correspond well to the dynamic aperture. Here we develop a method called diffusion map analysis, aiming to describe the beam distribution diffusion in transverse amplitude space by tracking less turns. The diffusion may come from quantum fluctuation of SR, beamstrahlung effect and nonlinearity. Comparing cases with different configuration of sextupoles, the diffusion map analysis presents good consistency with beam lifetime that needs much more turns of tracking. Constraints based on the diffusion map is applied to our dynamic aperture optimization, which could help us achieve enough long beam lifetime. PB - JACoW Publishing CP - Geneva, Switzerland SP - 203 EP - 205 KW - dynamic-aperture KW - radiation KW - synchrotron-radiation KW - collider KW - synchrotron DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-MOPGW051 UR - http://jacow.org/ipac2019/papers/mopgw051.pdf ER - TY - CONF AU - Zhang, Y. AU - Lin, C.T. AU - Wang, N. AU - Yu, C.H. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - Crosstalk of Beam-Beam Effect and Longitudinal Impedance at CEPC J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - In conventional e⁺e⁻ storage ring colliders, we only use lengthend bunch length in beam-beam simulation instead of considering impedance directly. It is no problem since the longitudinal dynamics is not sensitive to beam-beam interaction. But it is different since the bunch will also be lengthend during beam-beam interaction by beamstrahlung effect. It is very natural and more self-consistent to consider the longitudinal impedance in the beam-beam simulation. The simulation shows that the working point region of stable collision is slightly shifted by the longitudinal impedance. It is found that the vertical coherent oscillation may decreases the beam-beam limit with impedance at some working point. PB - JACoW Publishing CP - Geneva, Switzerland SP - 247 EP - 249 KW - impedance KW - simulation KW - luminosity KW - collider KW - factory DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-MOPGW068 UR - http://jacow.org/ipac2019/papers/mopgw068.pdf ER - TY - CONF AU - Bai, S. AU - Gao, J. AU - Geng, H. AU - Wang, D. AU - Wang, Y. AU - Yu, C.H. AU - Zhang, Y. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - Beam-Gas and Beam-Thermal Photon Scattering in CEPC J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - The Circular Electron Positron Collider (CEPC) is a proposed Higgs factory with center of mass energy of 240 GeV to measure the properties of Higgs boson and test the standard model accurately. Beam loss background in detectors is an important topic at CEPC. Beam-Gas scattering (BG) and Beam-Thermal photon scattering (BTH), although not so serious as Radiative Bhabha scattering (RBB) and Beamstrahlung (BS), are also important components of the beam induced backgrounds at CEPC due to the beam lifetime. In this paper, we evaluated the beam-gas and beam-thermal photon scattering in simulation and designed collimators to suppress the radiation level on the machine and the detector. PB - JACoW Publishing CP - Geneva, Switzerland SP - 626 EP - 629 KW - scattering KW - photon KW - background KW - detector KW - factory DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-MOPRB024 UR - http://jacow.org/ipac2019/papers/moprb024.pdf ER - TY - CONF AU - Lu, L. AU - He, T. AU - Xing, C.C. AU - Yang, L. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - Design and Low Power Test of a Prototype HOM LINAC J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - A 325MHz HOM (higher order mode) type linac was proposed and studied for proton or heavy ion acceleration in medium energy region. The cavity was finished the fabrication already by using copper and aluminum material. We will report results of low power test of the HOM linac in this paper. PB - JACoW Publishing CP - Geneva, Switzerland SP - 1001 EP - 1004 KW - DTL KW - HOM KW - cavity KW - linac KW - impedance DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-MOPTS063 UR - http://jacow.org/ipac2019/papers/mopts063.pdf ER - TY - CONF AU - Wang, L. AU - Fang, W. AU - Hirshfield, J.L. AU - Jiang, Y. AU - Shchelkunov, S.V. AU - Zhao, Z.T. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - 1st+2nd Harmonic Photocathode Bimodal Gun R&D J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - A novel Bimodal Electron Gun is designed to apply microwaves at two harmonically-related frequency in a 0.6 cell RF gun to increase the RF breakdown threshold and enhance the beam quality. This stratagem is intended to allow the RF gun structure to support a high accelera-tion gradient as well as to manipulate the emittance evolution in the half cell. By selecting a proper ampli-tude ratio and phase relationship between the first and second harmonic RF field components in the gun cavity, the superposition of the harmonic field components can provide a flat-top like RF profile to omitting the RF emittance component in the gun, while increase the RF breakdown threshold. The recent status of the Bimodal Electron Gun R&D is presented, including the designs of the novel two frequency RF structure and the simulation of the beam dynamic. PB - JACoW Publishing CP - Geneva, Switzerland SP - 2054 EP - 2057 KW - gun KW - emittance KW - cathode KW - electron KW - cavity DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-TUPTS054 UR - http://jacow.org/ipac2019/papers/tupts054.pdf ER - TY - CONF AU - Fang, W. AU - Wang, L. AU - Zhao, Z.T. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - Design Study of 3.6-cell C-band Photocathode Electron Gun J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - A C-band photocathode injector composed of a 3.6-cell C-band photocathode RF gun and two 1.8-meter C-band accelerating structures is proposed. The injector is a low emittance electron source for Free Electron Lasers (FEL) and other compact light sources. The RF structure of the cavities is designed with 2D SUPERFISH simulation. The Beam dynamic study in ASTRA helps rectify the 2D RF simulation. To feed the cavities, a design of extra coaxial coupler with RF gun structure is presented. With compact focusing solenoids, for 0.25nC bunch charge, the final energy can reach 6.9 MeV energy and the 95% emittance can be as low as 0.23 mm mrad (95%). All the details of RF design and beam dynamics studies are presented in this paper. PB - JACoW Publishing CP - Geneva, Switzerland SP - 2121 EP - 2123 KW - gun KW - emittance KW - simulation KW - FEL KW - cathode DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-TUPTS085 UR - http://jacow.org/ipac2019/papers/tupts085.pdf ER -