211124417
MAGNET FIELD CROSSTALK EFFECT OF TPS STORAGE RING MAGNETS
The free space between magnets of Taiwan Photon Source (TPS) storage ring is slight, especially the space between the quadrupole and sextupole magnets. The minimum space between the yokes of quadrupole and sextupole magnets is about 150 mm, but the space between coils is only 10 mm. Accordingly, significant distortions of the magnetic field can have an impact on the performance of the machine. A comparison between two magnets and an individual magnet was simulated with TOSCA 3D. The crosstalk effect shows that the sextupole component normalized to the quadrupole field at x=0.03 m increases from 4 10 to 4 10 in the quadrupole magnet and the quadrupole component increases from 8 10 to 6 10 in the sextupole magnet. We discuss this crosstalk effect and how to decrease the effect with appropriate shielding. INTRODUCTION The TPS will be a highly brilliant synchrotron x-ray source for multidisciplinary experimental research in Taiwan. The most visible feature of the complex will be a 3~3.3GeV electron-storage ring having circumference 518 m. The TPS storage ring consists of approximately 460 magnetic elements, including 48 dipoles, 240 quadrupoles, 168 sextupoles etc [1]. The main parameters of the magnet design are listed in Table 1. Various of these magnets will be placed with an axial spacing between them smaller than in any other machine. The interference harmonics due to the proximity of magnets should be accurately known for ease of commissioning and reliable performance of the machine. CROSSTALK EFFECT BETWEEN QUADRUPOLE AND SEXTUPOLE The minimum distance between the yokes of quadrupole and sextupole magnets is about 150 mm, shown in Fig. 1. The beam is along the z-axis and the cross section of the magnet is in the xy plane. To compare the quadrupole gradient field (B1) with and without the sextupole, from a simulation we plot the vertical component of the field (By) as a function of z at x=40 mm and y=0 in three cases in Fig. 2. The red line results from only the quadrupole magnet in the space in the calculation of the field distribution; the green line is only from the sextupole magnet in the space, whereas the black line shows the two magnets in the space and both magnets powered. The field decreases to zero at z=236 mm between the two magnets, and the two magnets were separated by this point in this discussion. Figure 1: One tight case of the TPS quadrupole and sextupole magnets for study of the crosstalk effect. Table 1: Specifications of Storage-Ring Magnets Type Dipole Quadrupole Sextupole Quantity 48 192/48 168 Length (m) 1.1 0.3/0.6 0.25 Field strength(T,T/m,T/m) 1.191 17/15.63 478 Full gap (mm) 46 74 78 Good field region (mm) 40×30 ±30 ±32 Turns/pole 36 54/48 26 Conductor(mm) 16×16 8×8/9×9 8×8 Coolant diameter (mm) 7 4/4.5 4 Current (A) 640 188/187 135 Power/magnet (kW) 8.53 2.56/2.86 0.77 Water circuit number 4 4 2 Water velocity (m/s) 1.23 1.2/1.34 0.73 ___________________________________________ kuo.cy@nsrrc.org.tw Proceedings of IPAC’10, Kyoto, Japan MOPEB022 07 Accelerator Technology T09 Room-Temperature Magnets 325 0 100 200 300 400 500 600 700 800 900 -0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
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.
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
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.
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.
118545912
Two-photon and two-gluon decays of p-wave heavy quarkonium using a covariant light-front approach
In this paper, a study of two-photon and two-gluon decays in the context of p-wave heavy quarkonia is presented. Within the covariant light-front framework, the annihilation rates of scalar and tensor quarkonium states are derived. In the absence of free parameters in this case, the results for the charmonium decay widths are consistent with the experimental data. However, in comparison to other theoretical calculations, there are large discrepancies in our results regarding bottomonia.
17389081
Lepton pair decays of the K L meson in the light-front model
We analyze ${K}_{L}$ lepton pair decays of ${K}_{L}\ensuremath{\rightarrow}{l}^{+}{l}^{\ensuremath{-}}\ensuremath{\gamma}$ and ${K}_{L}\ensuremath{\rightarrow}{l}^{+}{l}^{\ensuremath{-}}{l}^{\ensuremath{'}+}{l}^{\ensuremath{'}\ensuremath{-}}(l,{l}^{\ensuremath{'}}=e,\ensuremath{\mu})$ within the framework of the light-front QCD approach (LFQA). With the ${K}_{L}\ensuremath{\rightarrow}{\ensuremath{\gamma}}^{*}{\ensuremath{\gamma}}^{*}$ form factors evaluated in a model with the LFQA, we calculate the decay branching ratios and find that our results are all consistent with the experimental data. In addition, we study ${K}_{L}\ensuremath{\rightarrow}{l}^{+}{l}^{\ensuremath{-}}$ decays. We point out that our prediction for ${K}_{L}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}$ is about $20%$ smaller than that in chiral perturbation theory. We also discuss whether one could extract the short-distance physics from ${K}_{L}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}.$
119482056
Light front approach for heavy pentaquark transitions
Assuming the two diquark structure for the pentaquark state as advocated in the Jaffe-Wilczek model, there exist exotic parity-even anti-sextet and parity-odd triplet heavy pentaquark baryons. The theoretical estimate of charmed and bottom pentaquark masses is quite controversial and it is not clear whether the ground-state heavy pentaquark lies above or below the strong-decay threshold. We study the weak transitions of heavy pentaquark states using the light-front quark model. In the heavy quark limit, heavy-to-heavy pentaquark transition form factors can be expressed in terms of three Isgur-Wise functions: two of them are found to be normalized to unity at zero recoil, while the third one is equal to 1/2 at the maximum momentum transfer, in accordance with the prediction of the large-Nc approach or the quark model. Therefore, the light-front model calculations are consistent with the requirement of heavy quark symmetry. Numerical results for form factors and Isgur-Wise functions are presented. Decay rates of the weak decays Theta_b+ to Theta_c0 pi+ (rho+), Theta_c0 to Theta+ pi- (rho-), Sigma'_{5b}+ to Sigma'_{5c}0 pi+ (rho+) and Sigma'_{5c}0 to N_8+ pi- (rho-) with Theta_Q, 
Sigma'_{5Q} and N_8 being the heavy anti-sextet, heavy triplet and light octet pentaquarks, respectively, are obtained. For weakly decaying Theta_b+ and Theta_c0, the branching ratios of Theta_b+ to Theta_c0 pi+, Theta_c0 to Theta+ pi- are estimated to be at the level of 10^{-3} and a few percents, respectively.
14344162
Consistent treatment for valence and nonvalence configurations in semileptonic weak deacys
Abstract We discuss the semileptonic weak decays of P → P ( P denotes a pseudoscalar meson). In these timelike processes, the problem of the nonvalence contribution is solved systematically as well as the valence one. These contributions are related to the light-front quark model (LFQM), and the numerical results show the nonvalence contribution of the light-to-light transition is larger than of the heavy-to-light one. In addition, the relevant CKM matrix elements are calculated. They are consistent with the data of Particle Data Group.
13346210
Charge and Transition Form Factors of Light Mesons with Light-Front Quark Model
The charge and transition form factors of pion (Fπ, Fπγ , and Fπγ∗) are studied with the light-front quark model. We find that our results for Fπ and Fπγ agree very well with experimental data. Furthermore, the decay constants of η and η are evaluated. We also calculate Fηγ and Fη′γ and compare with the experimental data. PACS numbers: 12.39.Ki, 13.40.Gp Typeset using REVTEX