117037168
Testing of TRISTAN insertion quadrupole magnet in superfluid helium
42191029
Multipole analysis for absolute magnetic field measured by multi-probe pulsed-NMR method
For accelerator dipole magnets, the study on multipole coefficients in a local region is useful for understanding magnet characteristics and checking construction procedure. The multi-probe pulsed-NMR method is a candidate for measurement of the local multipole coefficients. For the absolute fields measured by the multi-probe pulsed-NMR method, a rigorous application of the Fourier expansion is found to yield multipole coefficients. It is made clear that the direction of the dipole field is unable to be determined by the Fourier expansion alone. For estimating alignment accuracy of pulsed-NMR probes, the relationship between errors of multipole coefficients and those of probe position is derived by the Fourier expansion method. For applying of multi-probe pulsed-NMR method to accelerator dipole magnets, we designed and fabricated a field measuring system using two probes. The probes had NMR coils wound around glass ampoules with a diameter of about 1.4 mm. The NMR signal was processed with a phase lock loop circuit to produce the NMR frequency. Dipole field uniformity and multipole coefficients were measured at 0.35 T for a 1.5 m long dipole magnet. It was confirmed that the field data by this NMR system had an accuracy of 10/sup -6/.
123873319
Experimental observations of the ion-related coupled bunch instability in a bunch train in TRISTAN AR
An experiment was carried out in TRISTAN AR for the search of the fast beam-ion instability (FBII). A train of 100 bunches with 2 ns spacing was stored with the help of the transverse bunch feedback system. The nitrogen gas was intentionally leaked into the inside of the vacuum duct to enhance the ion effect. The oscillation patterns were recorded by the beam position monitor system which is capable of storing the transverse position of every bunch up to 1600 turns. The spectra of the bunch oscillations were also measured by a spectrum analyzer. This paper describes the results of the experiment and also discusses the possible explanation of them in terms of the FBII.
120566869
The TOPAZ inner drift chamber
We have constructed a cylindrical drift chamber with anode and cathode delay-line readouts, which is the innermost tracking device of the TOPAZ detector. This inner drift chamber (IDC) is used for the tracking of charged particles in both rφ and rz planes. Fast track-finding logics have been developed for the event triggering. We describe the design, the construction and the performances of the IDC in the first beam run.
523124
Development of a 56 mm aperture superconducting dipole model magnet for LHC
A 56 mm single aperture superconducting dipole model magnet, which is one of the frameworks of the LHC collaboration between KEK and CERN, has been developed. A central field of 8.65 T is provided at a load line ratio of 90% with a 5 block coil wound with NbTi superconducting cables. The magnet has a straight section of 0.8 m and a total length of 1.2 m. The distinctive features of the magnet are a magnetically symmetrical configuration being applicable to the twin aperture magnet and mechanical consideration sharing the magnetic forces with a high manganese steel collar and a horizontally split iron yoke. The magnet showed almost no training at 4.4 K. The first quench current at 1.8 K was 91% of the short sample I/sub c/ and the magnet reached a central magnetic field of 8.8 T. Finally it could be excited with the current of more than 99% of the short sample limit which corresponds to a central field of 9.63 T.
116197080
Test results of TRISTAN insertion quadrupole magnet in superfluid Helium
117749765
Experimental Study on the Scaling Law of a Self-Modulated Laser Wakefield Accelerator
We performed experiments to obtain an empirical scaling of a self‐modulated laser wakefield accelerator (SMLWFA) by using laser pulses at a laser power of 2–6 TW and pulse duration of 50 fs. By decreasing the electron density from 1.5 × 1020 cm−3 to 4 × 1019 cm−3 and increasing the laser power, the energy of quasimonoenergetic components increased from 7 MeV to 25 MeV. We obtained the scaling law, according to which the energy gain is inversely proportional to the electron density and proportional to the laser power when the acceleration length is greater than the dephasing length of acceleration. Satellite peaks in the forward‐scattering spectrum suggested that the excitation of a nonlinear wakefield was closely related to the quasimonoenergetic acceleration of electrons.
17039539
Resonant Excitation of Disk Oscillations in Two-Armed-Deformed Disks and Application to High-Frequency QPOs
In previous papers we showed that in one-armed deformed disks, p-mode and g-mode oscillations are resonantly excited by horizontal resonance, and applied it to high-frequency quasi-periodic oscillations (QPOs) observed in lowmass X-ray binaries. In that model, the observed time variation of kHz QPOs is regarded as being the result of a timedependent precession of the deformation. In this paper we consider another possible cause of the time variation of kHz QPOs. That is, we demonstrate that in two-armed deformed disks, p-mode and g-mode oscillations are excited by a vertical resonance, not by a horizontal resonance (horizontal resonance dampens them). Furthermore, we show that in the case of a vertical resonance, the frequencies of excited disk oscillations can vary with time if the vertical disk structure changes with time. A brief application of these results to the time variation of observed kHz QPOs is discussed.
118498018
An Attempt to Describe Frequency Correlations among kHz QPOs and HBOs by Two-Armed Nearly Vertical Oscillations
We examine whether the two-armed ($m=2$) vertical p-mode oscillations trapped in the innermost region of magnetized accretion disks with finite disk thickness can describe kHz QPOs and HBOs in LMXBs. First, we derive the frequency-frequency correlation of the two basic oscillations (both are fundamental modes in the vertical direction, but one is the fundamental and the other the first overtone in the radial direction), and compare it with the observed frequency correlation of twin kHz QPOs. Results show that the calculated frequency correlation can well describe observed correlation with reasonable values of parameters. Second, we examine whether the observed frequency correlation between kHz QPOs and HBO can be described by regarding HBO as the first overtone oscillation in the vertical direction (and the fundamental in the radial direction). The results suggest that i) innermost parts of disks on the horizontal branch are strongly diminished in their vertical thickness (presumably by hot coronae) and ii) the branch is roughly a sequence of variations of magnetic fields or disk temperature.
121162987
Polarization of recoil protons from proton Compton scattering in the region of the second πN resonance
Abstract The polarization of recoil protons from proton Compton scattering has been measured at an angle of 90° c.m.s. in the region of the second nucleon resonance. The scattered photons were detected by a telescope which consisted of a lead plate converter, scintillation-counter hodoscopes and a Cerenkov counter, The angles and momenta of recoil protons were analyzed by a magnet with four spark chambers. The polarization of protons was obtained from the asymmetry in the elastic scattering of protons on carbon in a spark chamber. The polarization of recoil protons from proton Compton scattering are − 0.36 ± 0.29 and − 0.13 ± 0.29 at incident photon energies of 700 ± 50 and 800 ± 50 MeV, respectively. The polarization of recoil protons from neutral pion photoproduction is also obtained and the results are in good agreement with the previous data. A calculation of the polarization of recoil protons in the proton Compton scattering has been made by using an isobar model. The results of the calculation are consistent with the experimental data.
124431523
Strong-interaction form factor of proton in high-energy proton-proton elastic scattering
SummaryAn analysis of high-energy proton-proton elastic-scattering data is made in terms of one-particle exchange type amplitude. The results show that the proton form factor is constant at large momentum transfer. This may be interpreted as evidence for the existence of a pointlike core in the proton.RiassuntoSi esegue un'analisi dei dati dello scattering elastico protone-protone di alte energie in termini dell'ampiezza del tipo dello scambio di una particella. I risultati mostrano che il fattore di forma del protone è costante a grande trasferimento di impulso. Questo può essere interpretato come prova dell'esistenza di un nocciolo puntiforme nel protone.РезюмеВ терминах амплитуды с одно-частичным обменом проводится анализ данных по протон-протонному упругому рассеянию при высоких энергиях. Полученные результаты показывают, что протонный форм-фактор является постоянным при больших передаваемых импульсах. Это можно интерпретировать, как подтверждение существования точечной сердцевины в протоне.