H. Ikegami

The QDMDQ magnetic spectrograph “Raiden” (I)-design and construction☆

Abstract A new magnetic spectrograph, named RAIDEN, for charged-particle spectroscopy was constructed and succesfully put into operation in the fall of 1976. The spectrograph principally consists of two dipoles, two quadrupoles and a multipole element arranged in the QDMDQ form. The specifications are: resolving power of p / δp = 2 × 10 4 , maximum acceptance solid angle of 13 msr, and maximum particle rigidity of 24 kG m. Great emphasis was placed on the multipole element to achieve dynamic focusing control.

A FOCAL PLANE COUNTER FOR THE SPECTROGRAPH 'RAIDEN'

Abstract A focal plane counter system at Research Center for Nuclear Physics, Osaka University is described. The position detector is a gas proportional counter of one meter in length. Resistive induction grid wires and the charge division method were used for position determination. The employment of the induction wires mounted on an inclined frame made it possible to realize a fast counter with sub-millimeter position resolution for non-normal incidence (53.5° to the normal) of the particle rays.

A 1.5 m single-wire position-sensitive proportional counter for a magnetic spectrograph with a large dispersion☆

Abstract A 1.52 m single-wire position sensitive proportional counter (SWPC) is described, which has been used as a focal plane detector of the spectrograph RAIDEN installed at RCNP AVF cyclotron facility. A long SWPC system is suitable for detecting light ions with medium position resolution (1–2 mm fwhm) and with good linearity (0.1%). A four-fold counter telescope and a gate control system largely reduced the background and the peak pile-up effects in high counting rate measurements (⪅90 kHz).

Line broadening and Coulomb displacement energies of the hole-state analogs in the A = 111−123 odd-mass Sn isotopes

Abstract Line broadening and orbit dependence of the Coulomb displacement energy have been observed for the 1g 9/2 , 2p 1/2 and 2p 3/2 hole-state analogs in a series of odd- A Sn isotopes. The observed widths are discussed in terms of spreading width with main contributions from mixing with the isovector monopole state as well as the escape width.

Characteristics and construction of charge-division type single-wire position-sensitive proportional counter

Abstract Characteristics and construction of charge-division type single-wire position-sensitive proportional counters are described. Performances of long detectors (1.16, 1.52 and 1.82 m long and 10×30 mm 2 cross section) and short and thin detectors (32 and 43 cm long and 6×14 mm 2 cross section) are discussed.

Two-dimensional focal plane counter with induction readout

Abstract A two-dimensional position sensitive gas proportional counter was constructed as a focal plane counter for a spectrograph with large dispersion. Position information along the focal plane is obtained by the charge division method using induced signals on resistive electrodes placed near the anodes. The vertical incidence position of a particle is determined from the drift time measurement. The usual deterioration of position resolution for non-normal incidence of the lightly ionizing particles is minimized by using a multi-anode design. The “induction readout” makes it possible to realize fast rise time of position pulses as well as of timing signals for the drift time measurement even for a 1.5 m long counter of multi-anode design.

JAERI magnetic spectrograph for heavy-ion research

Abstract The design of a magnetic spectrograph for heavy-ion reaction studies with the JAERI 20 MV tandem accelerator is described. The spectrograph consists of a quadropole (Q), a multipol (M1), a dipole (D1), a multipole (M2), a dipole (D2) and a multipole (M3). In order to obtain a unique mass identification over a wide mass range in combination with the time-of-flight measurement, the pain length difference ΔL is kept small: L/ΔL is designed to be larger than 210 for a horizontal angular spread of 5 mrad. A momentum resolving power P/ΔP of 7000 is obtainable for solid angles up to 16 msr. The M2 magnet is used to correct the kinematic effect in the range from k= −0.4 to 1.0. The dispersion is variable from 10 to 15.5 m along the focal plane for k = 0 by use of the M3 magnet.

Systematic observation of fine structure of the hole-state analogues in Ni isotopes

Abstract Using (p, d) reactions, fine structure of the ground hole-state anlogues in 57, 61, 63 Ni has been investigated with a magnetic spectrograph. The systematic variation of the spectra, including the 59 Ni data in our previous measurement, is interpreted in terms of isospin mixing. It is inferred that the most important contribution to the spreading width comes from the isovector monopole state in these nuclei.

The QDMDQ magnetic spectrograph “RAIDEN” (II) Correction of kinematic line broadening

Abstract Kinematic line broadening of the image was corrected by using multipole magnetic fields for the spectrograph “RAIDEN” at the Research Center for Nuclear Physics (RCNP). Arrival positions of the collimated rays with various angles of incidence were measured at the focal line as a function of strengths of the multipole magnetic fields. Measurements were performed for various values of the kinematic factor of nuclear particles scattered from the target nucleus. Strengths of the multipole fields which achieved the best directional focussing were extracted from the measured results. The strengths were proportional to the kinematic factor and the kinematic line broadening was corrected up to higher order in the median plane.

Hexadecapole strength in the region of the low-energy octupole resonance in 90Zr

Abstract The level structure of 90 Zr has been studied in the region of the low-energy octupole resonance ( E x = 5−9 MeV) by inelastic scattering of 65 MeV protons. The spectra were found to be highly structured; many states with different multi-polarities are excited. A large number of L = 4 states were found exhausting 5.8% of the E4 energy weighted sum rule.