J. Lerendegui-Marco

Pulse processing routines for neutron time-of-flight data

A pulse shape analysis framework is described, which was developed for n_TOF-Phase3, the third phase in the operation of the n_TOF facility at CERN. The most notable feature of this new framework is the adoption of generic pulse shape analysis routines, characterized by a minimal number of explicit assumptions about the nature of pulses. The aim of these routines is to be applicable to a wide variety of detectors, thus facilitating the introduction of the new detectors or types of detectors into the analysis framework. The operational details of the routines are suited to the specific requirements of particular detectors by adjusting the set of external input parameters. Pulse recognition, baseline calculation and the pulse shape fitting procedure are described. Special emphasis is put on their computational efficiency, since the most basic implementations of these conceptually simple methods are often computationally inefficient.

First tests of the applicability of γ-ray imaging for background discrimination in time-of-flight neutron capture measurements

In this work we explore for the first time the applicability of using gamma-ray imaging in neutron capture measurements to identify and suppress spatially localized background. For this aim, a pinhole gamma camera is assembled, tested and characterized in terms of energy and spatial performance. It consists of a monolithic CeBr3 scintillating crystal coupled to a position-sensitive photomultiplier and readout through an integrated circuit AMIC2GR. The pinhole collimator is a massive carven block of lead. A series of dedicated measurements with calibrated sources and with a neutron beam incident on a Au-197 sample have been carried out at n_TOF, achieving an enhancement of a factor of two in the signal-to-background ratio when selecting only those events coming from the direction of the sample

On the role of secondary pions in spallation targets

Abstract.We use particle-transport simulations to show that secondary pions play a crucial role for the development of the hadronic cascade and therefore for the production of neutrons and photons from thick spallation targets. In particular, for the n_TOF lead spallation target, irradiated with 20 GeV/c protons, neutral pions are involved in the production of

A direct method for unfolding the resolution function from measurements of neutron induced reactions

\sim 90\%

Geant4 Simulations for the Analysis of (n, \gamma ) Measurements at n_TOF

∼90% of the high-energy photons; charged pions participate in

GEANT4 simulations of the n_TOF spallation source and their benchmarking

\sim 40\%

Geant4 simulation of the n_TOF-EAR2 neutron beam: Characteristics and prospects

∼40% of the integral neutron yield. Nevertheless, photon and neutron yields are shown to be relatively insensitive to large changes of the average pion multiplicity in the individual spallation reactions. We characterize this robustness as a peculiar property of hadronic cascades in thick targets.

New measurement of the 242Pu(n,γ) cross section at n_TOF

Abstract The paper explores the numerical stability and the computational efficiency of a direct method for unfolding the resolution function from the measurements of the neutron induced reactions. A detailed resolution function formalism is laid out, followed by an overview of challenges present in a practical implementation of the method. A special matrix storage scheme is developed in order to facilitate both the memory management of the resolution function matrix, and to increase the computational efficiency of the matrix multiplication and decomposition procedures. Due to its admirable computational properties, a Cholesky decomposition is at the heart of the unfolding procedure. With the smallest but necessary modification of the matrix to be decomposed, the method is successfully applied to system of 1 0 5 × 1 0 5 . However, the amplification of the uncertainties during the direct inversion procedures limits the applicability of the method to high-precision measurements of neutron induced reactions.

Prospects for direct neutron capture measurements on s-process branching point isotopes

At the n_TOF facility at CERN, the (n, \(\gamma \)) experiments are usually carriedout with a set of C\(_{6}\)D\(_{6}\) scintillators, a simple setup characterized by a low neutron sensitivity. The drawback of this simple detection setup is an elaborated analysis procedure, the so called Pulse Height Weighting Technique, that requires a manipulation of the experimental detector response. The modeling of the detector response can just be done with help of Monte Carlo (MC) simulations. The goal of this work is to provide an overview of the analysis technique focusing on the detailed simulations performed with the Geant4 toolkit.