111325925
Reduction of ripple fields in DC magnet using an auxiliary winding
This paper presents a simple method to achieve 10−6 level of ripple fields in a large current DC magnet which is excited by a power supply of moderate ripple current content (10−4–10−5). A theory of the ripple field in a magnet with an auxiliary winding is derived and the conditions for ripple field reduction are obtained. When the resistance of the auxiliary circuit is much smaller than the reactance of that circuit, the ripple field bucking ratio is proportional to the quality factor of the auxiliary winding. To compare the theory with the experiment, a dipole magnet with an auxiliary winding was used. The auxiliary winding was either short-circuited or loaded with a resistor and the ripple fields were measured with a pickup coil placed in the magnet gap. When the auxiliary winding was short-circuited, a ripple field bucking ratio greater than 40 was achieved with a high output impedance power supply. This experimental result agrees well with the theory, and indicates that an auxiliary winding of a large cross-sectional area, instead of a large turn-number, is desired for an efficient ripple field reduction.
67819097
Fast beam-ion instability driven longitudinal damping
In the Pohang Light Source storage ring, we empty 68 buckets of total 468 buckets to cure the conventional ion trapping. However, the fast beam-ion instability is occasionally generated at higher beam current. Immediately after the strong vertical beam shaking due to the fast beam-ion instability, the longitudinal coupled bunch mode instabilities are substantially damped down without any active feedback system. We have described the fast beam-ion instability driven longitudinal damping and its mechanism in the Pohang Light Source storage ring.
54856298
Low frequency longitudinal relaxation oscillation
From the recent data analysis of the longitudinal feedback system and the streak camera, we have found a longitudinal relaxation beam oscillation whose frequency is a multiple of 36 Hz. When the relaxation oscillation is generated, horizontally oscillating wide beams are observed at the diagnostic beamline, and the beam lifetime is fluctuated. The strength of the longitudinal coupled bunch mode instabilities is also modulated sinusoidally. We have described the observed longitudinal relaxation oscillation in the Pohang Light Source storage ring.
56441588
RF noise driven dipole mode parametric resonance
In the Pohang Light Source (PLS) storage ring, we have occasionally experienced the abnormal spontaneous beam. lifetime reduction and strong longitudinal damping. Due to the abnormal beam lifetime reduction, available beam time is reduced substantially. From the recent data analysis of the PLS longitudinal feedback system (LFS) and the streak camera, we have found that the abnormal phenomena can be generated by the RF noise via the dipole mode parametric resonance of the RF phase modulation. We describe the observation of the dipole mode parametric resonance driven by the RF noise and compare it with a simulation result in the PLS storage ring.
122988282
A method of closed orbit correction under constraint conditions
We have developed the correction algorithm of the closed orbit distortion (COD) under the constraint condition where beam positions at particular points are not changed. The new algorithm is based on the modified PSINOM algorithm including the regularization process in order to avoid the inversion problem of the ill-posed response matrices. We have confirmed that the COD is well corrected with no orbit leak in the simulation and is in good agreement with the experiment.
26940755
Ultra-low noise single-photon detector based on Si avalanche photodiode.
We report operation and characterization of a lab-assembled single-photon detector based on commercial silicon avalanche photodiodes (PerkinElmer C30902SH, C30921SH). Dark count rate as low as 5 Hz was achieved by cooling the photodiodes down to -80 °C. While afterpulsing increased as the photodiode temperature was decreased, total afterpulse probability did not become significant due to detector's relatively long deadtime in a passively-quenched scheme. We measured photon detection efficiency >50% at 806 nm.
119414218
Covariant Harmonic Oscillators and Diffractive Excitations
We use convariant harmonic-oscillator wave functions to describe quark- model hadrons in Glauber's model of diffractive scattering. It is shown that the Glauber model can be constructed in the center-of-mass system in terms of fully covariant quantities. For elastic scattering, the covariant model gives the same result as that using nonrelativistic harmonic-oscillator wave functions. For the transition from the n = 0 to n = 2 states, which includes the diffractive excitations to the N (1470) and N (1690) resonances, the relativistic effect is simply a multiplication of the nonrelativistic amplitude by the factor (1- $alpha$$sup 2$), $alpha$ being the velocity difference between the incoming nucleon and the final-state resonance. We discuss the effects of these results on the existing nonrelativistic calculations.
14454392
Does Lorentz Boost Destroy Coherence
It is shown that the time-energy uncertainty relation can be combined into the position-momentum uncertainty relation covariantly in the quark model of hadrons. This leads to a Lorentz-invariant form of the uncertainty relations. This model explains that the quark model and the parton model are two different manifestations of the same covariant model. In particular, this covariant model explains why the coherent amplitudes in the quark model become incoherent, after a Lorentz boost, in the parton model. It is shown that this lack of coherence is consistent with the present form of quantum mechanics.
37376282
Finite-temperature corrections in the dilated chiral quark model
We calculate the finite-temperature corrections in the dilated chiral quark model using the effective potential formalism. Assuming that the dilaton limit is applicable at some short length scale, we interpret the results to represent the behavior of hadrons in dense and hot matter. We obtain the scaling law, f{sub {pi}}(T)/f{sub {pi}} = m{sub Q}(T)/m{sub Q} {approx_equal} m{sub {sigma}}(T)/m{sub {sigma}}while we argue, using PCAC, that pion mass does not scale within the temperature range involved in our Lagrangian. It is found that the hadron masses and the pion decay constant drop faster with temperature in the dilated chiral quark model than in the conventional linear sigma model that does not take into account the QCD scale anomaly. We attribute the difference in scaling in heat bath to the effect of baryonic medium on thermal properties of the hadrons. Our finding would imply that the AGS experiments (dense and hot matter) and the RHIC experiments (hot and dilute matter) will ``see`` different hadron properties in the hadronization exit phase.
118268883
Feynman's Branes and Feynman's Oscillators
Based on Feynman’s lifetime efforts on quantum mechanics and relativity, it is concluded that the basic difference between field theory and string theory is that field theory is based on running waves while string theory should deal with standing waves in the Lorentz-covariant regime. At the 1970 spring meeting of the American Physical Society held in Washington, DC, R. P. Feynman stunned the audience by proposing harmonic oscillators for relativistic bound states, instead of Feynman diagrams. His talk was later published in the paper of Feynman, Kislinger, and Ravndal [Phys. Rev. D, Vol. 3, 2706 (1971)]. These authors noted that the hadron mass spectra can be predicted by the degeneracy of the three-dimensional harmonic oscillators. In so doing, they started with the Lorentz-invariant differential equation for the harmonic oscillator, and obtained Lorentz invariant solutions. However, their solutions are not normalizable in the time-separation variable and cannot carry probability interpretation. It is pointed out that there are solutions normalizable in the time-separation variable within the framework � � ,
59372197
BEAM SIMULATION OF SQQ INJECTION SYSTEM IN KIRAMS-30 CYCLOTRON ∗
The injection system of KIRAMS-30 cyclotron consists of a doublegap buncher,an SQQ, and a spiral inflector. Initial beam with 100 mmmrad has been generated by random Gaussian function in the transverse plane and random uniform function in the longitudinal direction. Using the 3D electric and magnetic fields of a buncher, SQQ, inflector, and return-yoke bore, the characteristics of the beam injected into the KIRAMS-30 cyclotron’s central region has been obtained. This paper presents the results of its beam characteristics and parameters of each beam element.