122018234
Development trends for insertion devices of future synchrotron light sources
The in-vacuum undulator with a permanent magnet at room temperature is a mature technology and is widely used; with a short period length in a medium-energy facility, it can enhance photon brilliance in the hard x-ray region. A cryogenic permanent magnet has been investigated as an in-vacuum undulator; this undulator will become the best prospective device to satisfy the requirements of a photon source with great brilliance in the hard x-ray region. For the further hard x-ray region, a superconducting wiggler can provide great flux with a continuous spectrum, whereas a superconducting undulator will provide great brilliance with a discrete spectrum. High-temperature superconducting wires are highly promising for use in the development of superconducting undulators; unique algorithms for their development with an extremely short period in a small-magnet gap have been devised. Some out-of-vacuum planar undulators with special functions must also be fabricated to enable diverse applications in various light-source facilities. This article describes current and future developments for insertion devices in storage-ring and free-electron-laser facilities and discusses their feasibility for use therein.
25110773
Planning of insertion devices for the 3-GeV Taiwan Photon Source
The Taiwan photon source (TPS) is a 3-GeV storage ring with 24 straight sections for installation of insertion devices (ID), radio-frequency cavities (RF) and electron- beam injection. Most insertion devices are in-vacuum undulators to produce intense X-rays with a brilliance up to 1times1021 photons s-1 mrad-2 mm-2 per 0.1% bw. A superconducting wiggler is also necessary to provide higher energy in the medium-energy range of the TPS. The APPLE II elliptically polarized undulator and a long- period undulator provide a source with circular and any linear polarization and the VUV source. Projects to investigate a superconducting undulator and a cryogenic permanent-magnet undulator are launched for energies in a range 1.5-25 keV.
120445064
Superconducting wiggler with semi-cold beam duct at Taiwan light source
Abstract A 3.2 T superconducting wiggler with a periodic length of 6 cm and 32 poles was designed and fabricated as an X-ray source. The beam duct of this magnet is a semi-cold, ultra-high vacuum chamber that consists of an aluminum and stainless steel taper. The number of poles in this magnet design is even, to minimize the integral strengths of the multipole components. Two measurement systems—involving room-temperature and cryogenic Hall probes—were set up to measure the field of the superconducting wiggler. A cryogenic plant that supplied liquid helium and nitrogen to the superconducting wiggler has already been established. The performance of magnet construction is good and the commissioning of the superconducting wiggler in the storage ring has been successful. No trim coil compensation on the magnet is required to adjust the electron beam orbit. Furthermore, the electron beams exhibit no loss and remain highly stable after the superconducting wiggler has been quenched.
55126258
Design and Development of an Elliptically Polarized Undulator of Length 3.5 m for TPS
An elliptically polarized undulator of length 3.5 m and period length 48 mm (EPU48) is designed to fulfil experiments on spin-polarized PES and inelastic scattering at the Taiwan Photon Source (TPS). EPU48 would be used to produce variously polarized light in the soft X-ray spectral domain 0.4-1.5 keV. To achieve efficient mechanical performance and a high quality of photon source, a new manufacturing method by casting is adopted to fabricate a key component of the carriage of the undulator at National Synchrotron Radiation Research Center (NSRRC). We expect this approach to bestow advantages of decreased assembly error, increased rigidity and highly precise properties. Here we describe details of the design of the magnetic circuit and the mechanical design of the EPU48 based on this new concept of engineering construction. INTRODUCTION With electron energy 3 GeV and beam current 500 mA, Taiwan Photon Source (TPS) is a third-generation experimental facility for synchrotron radiation that is undergoing civil-engineering construction. Various insertion devices, including in vacuum undulators (IU), cryogenic permanent magnet undulators (CPMU), elliptically polarized undulators (EPU) and superconducting undulators (SU) that are being considered for installation into the new storage ring in the TPS commission stage, are being discussed and planned so as to equip the machine to produce great brilliance and intense light to fulfil multidisciplinary experimental requirements. For the undulators adopted at TPS, table 1 and figure 1 show the key parameters and spectral performance estimated with Spectra code [1]. Two EPU of Apple-II type providing all polarized modes for radiation in the soft X-ray spectral range will be built internally [2]. To achieve a high quality and a brilliant light source, the demands of a robust and highly precise mechanical carriage become the most significant subject. For the implementation of this device, various aspects include magnetic-force behaviour, the layout of the structural configuration, the assembly and component selection that require thorough consideration. The entire control instrumentation must otherwise be compatible with the EPCIS system. Here we discuss the recent development and design status of two sets of EPU48. Table 1: Specification of Insertion Devices Adopted at TPS Ee /GeV EPU48 IU22 IU22 U50 3 photon energy /keV HP 0.4-1.5 5-20 5-20 0.08-1.5
30348524
Design of mechanical structure and cryostat for IASW superconducting wiggler at NSRRC
An in-achromatic superconducting wiggler (IASW) was successfully constructed and installed at the Taiwan Light Source (TLS) in January 2006. The cryostat with a 30 L liquid nitrogen aluminum reservoir shielding surrounds the helium vessel, which comprises the cold mass and 100 L liquid helium. The helium vessel is suspended by eight suspension links, which are thermally intercepted at 80 K and can be adjusted by applying tension, such that the center of the cold mass does not move during cooled to 4.2 K. A three-layered stainless tube was designed to prevent the transfer port from freezing and the steam- electricity separation system is designed to supply electricity and return the helium gas to prevent freezing of the power feedthrough.
55667448
SUPERCONDUCTING UNDULATOR WITH VARIABLY POLARIZED LIGHT
This study investigates planar in-vacuo superconducting elliptically polarized undulators with periodic length of 5 cm (SEPU5) producing linearly and circularly polarized infrared rays or x-rays source. The vertically wound racetrack coil is chosen for the coil and pole fabrication of the SEPU5. When the up and down magnetic pole arrays with alternative directions rotated wires in the horizontal plane, an elliptical field radiates elliptically polarized light in the electron storage ring, the free electron laser (FEL), and the energy recovery linac (ERL) facilities. Meanwhile, an un-rotated wire magnet array is constructed together with the rotated wire magnet array on the same undulator is used to switch the linear polarization in horizontal and vertical, as well as the right- and left-circular polarization radiation. This investigation describes the main factors of the planar and helical undulator design for FEL and the concepts concerning the magnet array structures of the superconducting undulators.
119193692
Meson distribution amplitudes in holographic models
We study the wave functions of light and heavy mesons in both hard-wall (HW) and soft-wall (SW) holographic models which use AdS/CFT correspondence. In the case of massless constituents, the asymptotic behaviors of the electromagnetic form factor, the distribution amplitudes, and the decay constants for the two models are the same, if the relation between the dilaton scale parameter and the size of meson is an inverse proportion. On the other hand, by introducing a quark mass dependence in the wave function, the differences of the distribution amplitudes between the two models are obvious. In addition, for the SW model, the dependences of the decay constants of meson on the dilaton scale parameter $\kappa$ differ; especially f_{Qq}\sim \kappa^3/m_Q^2 is consistent with the prediction of the heavy quark effective theory if \kappa\sim m_Q^{1/2}. Thus the parameters of the two models are fit by the decay constants of the distinct mesons; the distribution amplitudes and the \xi-moments are calculated and compared.
53130855
Factorization of the 3 d superconformal index
We prove that 3d superconformal index for general N = 2 U(N) gauge group with fundamentals and anti-fundmentals with/without Chern-Simons terms is factorized into vortex and anti-vortex partition function. We show that for simple cases, 3d vortex partition function coincides with a suitable topological open string partition function. We provide much more elegant derivation at the index level for N = 2 Seiberg-like dualities of unitary gauge groups with fundamantal matters and N = 4 mirror symmetry
117250608
Study of rare $B^+_{c} \to D_{d,s}$ + lepton anti-lepton decays
We study the rare decays of $B_c^+\to D_{q}^{(*)+}l\bar{l}$ ($q=d,s$ and $l=\nu_l,e,\mu,\tau)$ in the standard model. The form factors are evaluated in the light front and constituent quark models, respectively. We find that the decay branching ratios calculated in the two models for $B_c^+\to D^+_q l\bar{l}$ agree well with each other, whereas those for $B_c^+\to D_q^{*+}l\bar{l}$ are different.
118440703
SU(3)symmetry breaking in decay constants and electromagnetic properties of pseudoscalar heavy mesons
In this paper, the decay constants and mean square radii of pseudoscalar heavy mesons are studied in the $SU(3)$ symmetry breaking. Within the light-front framework, the ratios ${f}_{{D}_{s}}/{f}_{D}$ and ${f}_{{B}_{s}}/{f}_{B}$ are individually estimated using the hyperfine splittings in the ${D}_{(s)}^{*}\ensuremath{-}{D}_{(s)}$ and ${B}_{(s)}^{*}\ensuremath{-}{B}_{(s)}$ states and the light quark masses, ${m}_{s,q}$ ($q=u$, $d$), to extract the wave function parameter $\ensuremath{\beta}$. The values ${f}_{{D}_{s}}/{f}_{D}=1.29\ifmmode\pm\else\textpm\fi{}0.07$ and ${f}_{{B}_{s}}/{f}_{B}=1.32\ifmmode\pm\else\textpm\fi{}0.08$ are obtained, which are not only chiefly determined by the ratio of light quark masses ${m}_{s}/{m}_{q}$, but also insensitive to the heavy quark masses ${m}_{c,b}$ and the decay constants ${f}_{D,B}$. The dependence of ${f}_{{B}_{c}}/{f}_{B}$ on $\ensuremath{\Delta}{M}_{{B}_{c}{B}_{c}^{*}}$ with the varied charm quark masses is also shown. In addition, the mean square radii are estimated as well. The values $\sqrt{⟨{r}_{{D}_{s}^{+}}^{2}⟩/⟨{r}_{{D}^{+}}^{2}⟩}={0.740}_{+0.050}^{\ensuremath{-}0.041}$ and $\sqrt{⟨{r}_{{B}_{s}^{0}}^{2}⟩/⟨{r}_{{B}^{0}}^{2}⟩}={0.711}_{+0.058}^{\ensuremath{-}0.049}$ are obtained, and the sensitivities of $⟨{r}_{P}^{2}⟩$ on the heavy and light quark masses are similar to those of the decay constants.
16596210
A Consistent treatment for pion form-factors in space - like and time - like regions
We write down some relevant matrix elements for the scattering and decay processes of the pion by considering a quark-meson vertex function. The pion charge and transition form factors $F_\pi$, $F_{\pi\gamma}$, and $F_{\pi\gamma^*}$ are extracted from these matrix elements using a relativistic quark model on the light-front. We found that, the form factors $F_\pi$ and $F_{\pi\gamma}$ in the space-like region agree well with experiment. Furthermore, the branching ratios of all observed decay modes of the neutral pion, that are related to the form factors $F_{\pi\gamma}$ and $F_{\pi\gamma^*}$ in the time-like region, are all consistent with the data as well. Additionally, $F_\pi$ in the time-like region, which deals with the nonvalence contribution, is also discussed.