B. M. Nyakó

The first candidate for chiral nuclei in the A~80 mass region: 80Br

Abstract Excited states of 80Br have been investigated via the 76Ge(11B, α 3 n ) and 76Ge(7Li, 3n) reactions and a new Δ I = 1 band has been identified which resides ∼ 400 keV above the yrast band. Based on the experimental results and their comparison with the triaxial particle rotor model calculated ones, a chiral character of the two bands within the π g 9 / 2 ⊗ ν g 9 / 2 configuration is proposed, which provides the first evidence for chirality in the A ∼ 80 region.

Detailed spectroscopy of the normally deformed states in 132Ce

Abstract High-spin states have been studied in 132 Ce produced in the 100 Mo( 36 S,4nγ) reaction using the EUROGAM II spectrometer. The structure of the normally deformed states ( β 2 ∼ 0.2) has been investigated. Eight ΔI = 2 bands and three ΔI = 1 bands have been identified and the level scheme extended up to spin and parity (40 + ) at an excitation energy 19.79 MeV. The results are interpreted with the aid of Woods-Saxon cranking calculations, which suggest a variety of triaxial (γ) shapes in this nucleus stabilised by specific active quasiparticle orbitals.

Particle discriminator for the identification of light charged particles with CsI(Tl) scintillator + PIN photodiode detector

Abstract A particle discriminator exploiting the ballistic deficit effect for pulse shape discrimination has been developed for CsI(Tl) scintillator + PIN photodiode charged-particle detectors. The method is theoretically investigated and it is shown that the figure of merit of the particle separation is mainly governed by the absolute value of the differential quotient of the rise time dependent ballistic deficit. As the actual particle discriminator contains shaping amplifiers, baseline restorer, pile-up rejector and analog-to-digital converters, it directly accepts signals from a charge-sensitive preamplifier, and its outputs deliver the type and the energy of the particles in the form of eight-bit digital codes. The performance of the particle discriminator is characterised by the figure-of-merit measured as a function of the particle energy.

Evidence for multiple band terminations in 102Pd

Abstract The level structure of 102 Pd has been investigated using data collected with the Eurogam 2 array. Several cascades of γ-rays have been established up to high spins. Termination of rotational bands has been observed at I π = 28 − and 32 + , and tentatively at I π = 38 + and 42 + . The nucleus 102 Pd is the first case where rotational bands built on valence space configurations are followed from spin close to zero up to termination and, at higher spins, a smooth rotational band which appears to terminate is built on core excited configurations.

High-spin study of 128Ce and systematics of quasiparticle pair alignment

Abstract High-spin states have been studied in 128 Ce, produced in the 100 Mo( 32 S,4n) reaction, using the Euroball γ -ray spectrometer. A quadruples analysis ( γ 4 ) of the data has extended several bands to high spin. Systematics of quasiparticle alignments in cerium isotopes and relevant isotonic chains are discussed and compared to Woods–Saxon cranking calculations.

Measurement of transition quadrupole moments of high-spin states in the N=74 isotones 133Pr, 132Ce and 131La

Abstract The Doppler-Shift Attenuation Method has been used to extract transition quadrupole moments of high-spin bands in the N=74 isotones 133 Pr, 132 Ce and 131 La, produced in the 37 Cl + 100 Mo reaction. The results appear to be configuration dependent and, for 133 Pr and 132 Ce, the involvement of Ω=1/2 νh 9/2 and νf 7/2 intruder orbitals appears to enhance the collectivity at high spin ( I>25 ℏ ).

Low-lying levels and high-spin band structures in 102Rh

Abstract Levels in 102 Rh have been populated in the reaction 70 Zn+ 36 S at 130 MeV. The level structure of 102 Rh has been investigated using the EUROGAM II array. Low-lying states and four high-spin bands have been identified. The configurations of low-lying levels and two-quasiparticle bands are interpreted in the frame of the interacting boson-fermion-fermion model. The four observed band structures are also compared with cranked shell model calculations using a modified oscillator potential.

Realization of charge sensitive preamplifiers using current feedback operational amplifier

Abstract A simple charge sensitive preamplifier circuit has been designed, which uses a CFOPA. Despite its simplicity the preamplifier exhibits good noise and speed parameters.

OPTIMIZATION OF THE PARTICLE DISCRIMINATOR BASED ON THE BALLISTIC DEFICIT METHOD USING DELAY-SWITCHED GATED INTEGRATOR

Abstract The particle discriminator we developed for CsI(Tl) elements of an ancillary detector array planned to be used together with large γ-ray detector systems utilizes the ballistic deficit effect for particle discrimination. This technique applies a low-ballistic-deficit long-time-constant unipolar semi-Gaussian shaper and a large-ballistic-deficit short-time-constant bipolar shaper. To match the signal processing time of our discriminator with that of the standard electronics for Ge detectors the long-time-constant semi-Gaussian shaper was substituted with the so-called delay-switched gated integrator. The experimental tests of the new arrangement show that the pulse processing time can be significantly shortened. The figure of merit of the particle discrimination improves with increasing the total integration time of the delay-switched gated integrator up to 12 μs, above which the improvement is negligible. Therefore, this 12 μs integration time is considered as a good compromise as for the figure of merit and the dead time of the new arrangement.

ON THE NOISE PERFORMANCE OF A NOVEL DELAY-SWITCHED GATED INTEGRATOR

Abstract For trapezoidal filtering, widely used for diminishing the harmful effect of the ballistic deficit, a modified version of the gated integrator is suggested. In this delay-switched gated integrator the true integration is delayed with respect to the beginning of the pulse, and for the delay period the true integration process is approximated with a low-pass filter. The paper theoretically compares the noise behavior of the delay-switched gated integrator and that of the gated integrator. The noise calculations are based on the concept of the step- and delta-noise residual functions and they are performed in three cases. In the first case the standalone shaping circuits are analyzed, in the second case they are preceded by a fast baseline restorer and in the third case they are preceded by a baseline restorer of finite time constant. It is shown that the novel delay-switched gated integrator preceded by a baseline restorer can be a good alternative to gated integrators.