56298522
Operational experience of the insertion devices and expectation of the future superconducting wigglers at NSRRC
Since 1995, we have continuously installed five insertion devices (IDs) in the 1.5 GeV storage ring TLS at NSRRC. They include three undulators (U5, U9 and EPU5.6), one 1.8 Tesla wiggler (W20) and one 6 Tesla superconducting wavelength shifter (SWLS). All these five IDs are located in the long straight sections. The real time orbit correction and betatron tune compensation routine have been successfully operated. With these IDs, the machine emittance reduces substantially. We plan to install four more superconducting multi-pole wigglers (SMPWs), one in the long straight and three in the archromat sections. These devices therefore can offer more beam time for the hard X-ray community. The impacts of these IDs on the beam dynamics effects are reported in this paper.
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.
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.
36542122
Construction and Performance of Superconducting Magnets for Synchrotron Radiation
Two superconducting magnets, one wavelength shifter with a field of 6 T and one wiggler with a field of 3.2 T, were constructed and routinely operated at Taiwan Light Source to generate synchrotron X-rays. Additionally, three short multipole wigglers with the same field of 3.1 T are under construction and will be installed in the three achromatic short straight sections. A warm beam duct with an inner gap of 20 mm and a 1.5 W GM type cryo-cooler were used in the wavelength shifter to achieve cryogen-free operation. For the 3.2 T wiggler, a cold beam duct with an inner gap of 11 mm was kept at 100 K temperature and no trim coil compensation is necessary for its operation. Meanwhile, no beam loss was observed when it was quenched. The design concept, magnetic field quality, and the commissioning results of these magnets will be presented.
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.
14073034
Electromagnetic properties of heavy mesons in heavy quark limit
Abstract The electromagnetic (EM) form factors of the pseudoscalar and vector mesons are calculated in the light-front framework. We extract these form factors from the relevant matrix elements directly, instead of choosing the Breit frame. The results show that the charge radius of the meson are related to both the first and second longitudinal momentum square derivative of the momentum distribution function. In addition, the static properties of the EM form factors and the heavy quark symmetry of the charge radii are checked analytically when we take the heavy quark limit.
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.
204174153
Combined chiral dynamics and MIT bag model study of strong Sigma(*) Q-->LambdaQpi decays
119485274
Covariant Light-Front Approach for s-wave and p-wave Mesons: Its Application to Decay Constants and Form Factors
We study the decay constants and form factors of the ground-state s-wave and low-lying p-wave mesons within a covariant light-front approach. Numerical results of the form factors for transitions between a heavy pseudoscalar meson and an s-wave or p-wave meson and their momentum dependence are presented in detail. In particular, form factors for heavy-to-light and B → D ∗∗ transitions, where D ∗∗ denotes generically a p-wave charmed meson, are compared with other model calculations. The experimental measurements of the decays B − → D ∗∗ π − and B → DD ∗∗ are employed to test the decay constants of D ∗∗ and the B → D ∗∗ transition form factors. The heavy quark limit behavior of the decay constants and form factors is examined and it is found that the requirement of heavy quark symmetry is satisfied. The universal Isgur-Wise (IW) functions, one for s-wave to s-wave and two for s-wave to p-wave transitions, are obtained. The values of IW functions at zero recoil and their slope parameters can be used to test the Bjorken and Uraltsev sum rules.
2656324
Radiative leptonic decays of heavy mesons in heavy quark limit
We study the radiative leptonic decays of heavy mesons within the covariant light-front model. Using this model, both the form factors FV and FA have the same form when the heavy quark limit is taken. In addition, the relation between the form factor FV and the decay constant of a heavy meson FH is obtained. The hadronic parameter β can be determined by the parameters appearing in the wave function of the heavy meson. We find that the value of β is not only quite smaller than the one in the non-relativistic case, but also insensitive to the value of the light quark mass mq. These results mean that the relativistic effects are very important in this work. We also obtain that the branching ratio of B→lνlγ is about (1.40–1.67)×10-6, in agreement with the general estimates in the literature.