Investigating timing properties of modern digitizers utilizing interpolating CFD algorithms and the application to digital fast-timing lifetime measurement

The performance of two implementations of digital real-time interpolating constant fraction discriminator algorithms with respect to fast-timing lifetime measurements are investigated. The implementations integrated in two different digitizers were evaluated in terms of the effects of tuning parameters of the digital CFDs and the influence of different input amplitudes on the time resolution and time walk characteristics. Reference is made to the existing analog standard of fast-timing techniques. The study shows, that the timing performance of both modules is comparable to established fast-timing setups using analog constant fraction discriminators, but with the added benefit of digital processing. Both digitizer modules were found to be highly effective and user-friendly instruments for modern fast-timing requirements.Comment: 13 pages, 16 figure

Fast-timing measurements in ⁹⁶Pd:improved accuracy for the lifetime of the 4⁺₁ state

Direct lifetime measurements via γ–γ coincidences using the FATIMA fast-timing LaBr3(Ce) array were performed for the excited states below previously reported isomers. In the N = 50 semi-magic 96Pd nucleus, lifetimes below the I π = 8+ seniority isomer were addressed as a benchmark for further analysis. The results for the I π = 2+ and 4 + states confirm the published values. Increased accuracy for the lifetime value was achieved for the 4 + state.peerReviewe

Broken seniority symmetry in the semimagic proton mid-shell nucleus ⁹⁵Rh

Lifetime measurements of low-lying excited states in the semimagic ( N = 50 ) nucleus 95Rh have been performed by means of the fast-timing technique. The experiment was carried out using γ -ray detector arrays consisting of LaBr3(Ce) scintillators and germanium detectors integrated into the DESPEC experimental setup commissioned for the Facility for Antiproton and Ion Research (FAIR) Phase-0, Darmstadt, Germany. The excited states in 95Rh were populated primarily via the β decays of 95Pd nuclei, produced in the projectile fragmentation of a 850 MeV/nucleon 124Xe beam impinging on a 4 g / cm2 9Be target. The deduced electromagnetic E2 transition strengths for the γ -ray cascade within the multiplet structure depopulating from the isomeric Iπ = 21 / 2+ state are found to exhibit strong deviations from predictions of standard shell model calculations which feature approximately conserved seniority symmetry. In particular, the observation of a strongly suppressed E2 strength for the 13 / 2+ → 9 / 2+ ground state transition cannot be explained by calculations employing standard interactions. This remarkable result may require revision of the nucleon-nucleon interactions employed in state-of-the-art theoretical model calculations, and might also point to the need for including three-body forces in the Hamiltonian

Lifetime measurements of the low-lying excited states of ²⁰⁸Po

In this study we present the preliminary results about the lifetimes of the 2₂⁺, 4₁⁺ states of ²⁰⁸Po and the upper limit of the lifetime of the 2₁⁺ state. For measuring the lifetimes of the 2₁⁺ and 4₁⁺ states the Recoil Distance Doppler Shift (RDDS) method and for the lifetime of the 2₂⁺ state the Doppler Shift Attenuation method (DSAM) were used. The resulting absolute transition strength B(M1 ; 2₂⁺ → 2₁⁺) ≥ 0.122(20) μN² reveals the predominant isovector nature of the 2₂⁺ state of ²⁰⁸Po

Lifetime measurements in <math><mmultiscripts><mi>Mo</mi><mprescripts/><none/><mn>92</mn></mmultiscripts></math>: Investigation of seniority conservation in the <math><mrow><mi>N</mi><mo>=</mo><mn>50</mn></mrow></math> isotones

International audienceExcited states in the yrast and negative parity bands in Mo92 were populated in two different experiments using the Zr90(α,2n)Mo92 and Nb93(p,2n)Mo92 fusion-evaporation reactions at the Cologne FN Tandem accelerator and measured using a hybrid setup of high purity germanium and lanthanum bromide detectors. Lifetimes of the excited 21+, 41+, 61+, 81+, 51−, 71−, and 91− states were measured using the γ-γ fast-timing technique. The newly measured lifetime of the 41+ state differs from the recently published value measured using the recoil distance Doppler shift method. Experimental B(E2) strengths of excited states in Mo92 are used to predict theoretical B(E2) values in the N=50 isotones from Tc93 up to Rh95 using semiempirical calculations in the single-j orbital 0g9/2 for the protons

Lifetime measurements in <math><mmultiscripts><mi>Mo</mi><mprescripts/><none/><mn>92</mn></mmultiscripts></math>: Investigation of seniority conservation in the <math><mrow><mi>N</mi><mo>=</mo><mn>50</mn></mrow></math> isotones

International audienceExcited states in the yrast and negative parity bands in Mo92 were populated in two different experiments using the Zr90(α,2n)Mo92 and Nb93(p,2n)Mo92 fusion-evaporation reactions at the Cologne FN Tandem accelerator and measured using a hybrid setup of high purity germanium and lanthanum bromide detectors. Lifetimes of the excited 21+, 41+, 61+, 81+, 51−, 71−, and 91− states were measured using the γ-γ fast-timing technique. The newly measured lifetime of the 41+ state differs from the recently published value measured using the recoil distance Doppler shift method. Experimental B(E2) strengths of excited states in Mo92 are used to predict theoretical B(E2) values in the N=50 isotones from Tc93 up to Rh95 using semiempirical calculations in the single-j orbital 0g9/2 for the protons

Triaxiality in the mid-shell nucleus Pd-112

Lifetimes of low-spin excited states in Pd-112 were measured using the recoil-distance Doppler-shift technique. The nucleus of interest was populated in a (110)pd(O-18, O-16)Pd-112 reaction using the Cologne FN Tandem accelerator. Three lifetimes of ground-state band members and one lifetime of the y band were measured. From these lifetimes reduced transition probabilities were extracted and compared to interacting boson model, gamma-soft calculations, and Davydov calculations. The lifetime of the 2(gamma)(+) gives some insights on the nuclear shape and structure of the gamma band. The deduced transition rates show an indicator for a rigid triaxial nucleus as well as more indicators for a gamma-soft nucleus

gamma-gamma fast timing at X-ray energies and investigation on various timing deviations

We report on systematic gamma-gamma fast-timing measurements by using four cylindrical 1.5 '' x 1.5 '' LaBr3(Ce) scintillator detectors which were installed in compact geometry around the focal plane of the Lohengrin fission-fragment separator at the Institut Laue-Langevin in Grenoble, France. Unconventional gamma-ray sources as Os-185 and W-187 were produced by thermal-neutron activation to provide nearly prompt low-energy gamma and K-X rays with average gamma- and X-ray multiplicity equal to two. Due to practically no contribution of Compton background, highly precise results of time-walk measurements down to 40 keV are presented. Timing deviations related to different phenomena have been investigated, such as the geometry of an extended gamma-ray source and the detector arrangement, long-term timing shifts and the timing contributions of the Compton background and the inter-detector Compton-scattering. The geometrical timing deviations are shown to be minimized using a multi-element detector array with a centrally symmetric arrangement relative to the center of the focal plane. Time-correction formula are proposed as analytical corrections for long-term time shifts, the time contributions of the Compton background and the position-dependent change of the time walk for cases where the calibration source cannot be placed at the center of the focal plane