6982155
Neutrino-photon scattering and its crossed processes in a background magnetic field
Abstract We study the neutrino-photon processes such as γγ→ν ν , νγ → νγ , and ν ν →γγ in a background magnetic field smaller than the critical magnetic field B c ≡ m e 2 / e . Using Schwinger's formalism, we extract leading magnetic-field contributions to the above processes. Our result is valid throughout the kinematic regime where both neutrino and photon energies are significantly smaller than m W . We briefly discuss the astrophysical implications of our result.
118628184
Model-independent analysis for determining mass splittings of heavy baryons
We study the hyperfine mass differences of heavy hadrons in the heavy quark effect theory. The effects of one-gluon exchange interaction are considered for the heavy mesons and baryons. Based on the known experimental data, we predict the masses of some heavy baryons in a model-independent way.
1152504
Weak-field expansion for processes in a homogeneous background magnetic field
The weak-field expansion of the charged fermion propagator under a uniform magnetic field is studied. Starting from Schwinger's proper-time representation, we express the charged fermion propagator as an infinite series corresponding to different Landau levels. This infinite series is then reorganized according to the powers of the external field strength B. For illustration, we apply this expansion to $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}}\ensuremath{\nu}\overline{\ensuremath{\nu}}$ and $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\nu}}\ensuremath{\nu}\ensuremath{\gamma}$ decays, which involve charged fermions in the internal loop. The leading and subleading magnetic-field effects to the above processes are computed.
12196534
Mesonic form factors and the Isgur-Wise function on the light front
Within the light-front framework, form factors for P{r_arrow}P and P{r_arrow}V transitions (P denotes a pseudoscalar meson, V a vector meson) due to the valence-quark configuration are calculated directly in the entire physical range of momentum transfer. The behavior of the form factors in the infinite quark mass limit are examined to see if the requirements of heavy-quark symmetry are satisfied. We find that the Bauer-Stech-Wirbel-type light-front wave function fails to give a correct normalization for the Isgur-Wise function at zero recoil in P{r_arrow}V transition. Some of the P{r_arrow}V form factors are found to depend on the recoiling direction of the daughter mesons relative to their parents. Thus the inclusion of the nonvalence contribution arising from quark-pair creation is mandatory in order to ensure that the physical form factors are independent of the recoiling direction. The main feature of the nonvalence contribution is discussed. {copyright} {ital 1997} {ital The American Physical Society}
204174153
Combined chiral dynamics and MIT bag model study of strong Sigma(*) Q-->LambdaQpi decays
11335733
Charge radii of light and heavy mesons
Abstract. We calculate the electromagnetic (EM) form factors of the pseudoscalar mesons in the light-front framework. Specifically, these form factors are directly extracted from the relevant matrix elements, instead of choosing the Breit frame. The results show that the charge radius of the meson is related to both the first and second longitudinal momentum square derivatives of the momentum distribution function. The static properties of the EM form factors and the heavy quark symmetry of the charge radii are checked analytically in the heavy quark limit. In addition, we use the Gaussian-type wavefunction to obtain the numerical results.
54200358
Control system for the superconducting insertion devices of NSRRC
To enhance hard X-ray production in the 1.5 GeV storage ring of NSRRC to serve the rapidly growing X-ray user community in Taiwan, the storage ring are planed to install up to five superconducting insertion devices. A 6 Tesla superconducting wavelength shifter was installed in mid-2002. A 3.2 Tesla superconducting multipole wiggler will be installed in the fall of 2003. The project for the other three multipole wigglers is launched. The control system had been implemented to support the operation of the superconducting insertion devices. The control system play a role to coordinate the operation of the main power supply and the trimming power supplies to charge/discharge the magnet and provide interlock protection for the magnet coils and vacuum ducts. A friendly user interface and various application programs are used to support routine operation. Design considerations and details of the implementation are also presented.
125960180
Auto-field Shimming Algorithm for an Elliptically Polarized Undulator
115015433
Effectiveness of a Shielding Cabinet on the Storage-Ring Septum Magnet of Taiwan Light Source
Abstract To avoid a parasitic magnetic field in the stored beam, the pulsed-magnet system of Taiwan Photon Source (TPS) requires the stray field to be minute: the stray field from the storage-ring (SR) injection septum is required to be less than 0.1 % of the main field in the gap. The most common method to protect against a parasitic magnetic field is to use a highly permeable and conductive material, such as mu-metal. A 300-ms half-sine-wave pulse up to a current maximum 9922 A is supplied to a septum and results in an eddy-current loss in a magnet and a conductor during rapid charging of a magnet. Competition between an eddy-current effect and the magnetic permeability would produce a complicated phenomenon inside the magnetic-shielding screen and affect the shielding performance. We examined the performance of magnetic shielding of a shielding screen with OPERA 2D for varied geometry and thickness of the screen.
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
55509579
Design of a revolving helical staggered undulator
This investigation proposes a revolving helical staggered undulator with 10-mm and 15-mm period lengths for free electron laser operation. The helical staggered structure with a 10-mm period length is designed to produce vertical and horizontal field strength of 0.625 T at a phase shift of 90 degrees, by driving a longitudinal solenoid field of 0.7 T with a 3-mm gap. Three-dimensional magnetic field analysis was performed using RADIA computer code. An optimized magnetic structure was studied over various operating field ranges. A revolving helical undulator is equipped with two helical magnetic arrays to switch the helicity of radiation and broad radiation spectrum. Accordingly, the design of a helical staggered undulator is outlined.