Yassid AyyadUniversity of Santiago de Compostela | USC · IGFAE
Yassid Ayyad
Doctor of Philosophy
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218
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October 2018 - April 2021
January 2017 - October 2018
April 2015 - January 2017
Publications
Publications (218)
Background: The established Gaseous Detector with Germanium Tagging (GADGET) detection system is used to measure weak, low-energy β-delayed proton decays. It consists of the Gaseous Proton Detector equipped with a MICROMEGAS (MM) readout to detect protons and other charged particles calorimetrically, surrounded by the Segmented Germanium Array (SeG...
The (d,He2) reaction in inverse kinematics has been developed for experiments with rare-isotope beams to constrain electron-capture rates needed for astrophysical simulations of processes in dense nuclear environments such as supernovae and neutron star crusts. The first experiment focused on the measurement of the O14(d,He2) and N13(d,He2) reactio...
Static and mobile radiation detectors can be deployed in urban environments for a range of nuclear security applications, including radiological source search-and-tracking scenarios. Modeling detector performance for such applications is challenging, as it does not depend solely on the detector capabilities themselves. Many factors must be taken in...
We report the charge-changing cross sections (σcc) of 24 p-shell nuclides on both hydrogen and carbon at about 900A MeV, of which 8,9Li, 10–12Be, 10,14,15B, 14,15,17–22N and 16O on hydrogen and 8,9Li on carbon are for the first time. Benefiting from the data set, we found a new and robust relationship between the scaling factor of the Glauber model...
We discuss the reconstruction of low-energy nuclear reaction kinematics from charged-particle tracks in solenoidal spectrometers working in Active Target Time Projection Chamber mode. In this operation mode, reaction products are tracked within the active gas medium of the Active Target with a three dimensional space point cloud. We have inferred t...
In the last decades, measurements of spallation, fragmentation and Coulex induced fission reactions in inverse kinematics have provided valuable data to accurately investigate the fission dynamics and nuclear structure at large deformations of a large variety of stable and non-stable heavy nuclei. The collected data were used to constrain dynamic and...
We discuss the reconstruction of low-energy nuclear reaction kinematics from charged-particle tracks in solenoidal spectrometers working in Active Target Time Projection Chamber mode. In this operation mode, reaction products are tracked within the active gas medium of the Active Target with a three dimensional space point cloud. We have inferred t...
We present a measurement of the secondary scintillation yield produced by two-layer Thick Gas Electron Multipliers (M-THGEMs) in pure Tetrafluoromethane (CF 4 ) gas and in Ar mixed with 5% Xe in low-pressures down to 20 Torr. The detector was irradiated with 5.49 MeV alpha particles from a low-rate 241-Am source. The secondary scintillation light g...
We present a two-target measurement method to determine the interaction cross section of hypernuclei with a target nucleus. The method allows to extract from two independent measurements the production cross section of a given hypernucleus as well as its interaction cross section on a specific target. The latter is then further analyzed to deduce t...
For the first time, the (d,He2) reaction was successfully used in inverse kinematics to extract the Gamow-Teller transition strength in the β+ direction from an unstable nucleus. The new technique was made possible by the use of an active-target time-projection chamber and a magnetic spectrometer, and opens a path to addressing a range of scientifi...
Low energy fission of 234,235,236,238U and 237,238Np radioactive beams, provided by the GSI/FRS facility, has been studied using the R³B/SOFIA setup. The latter allows, on an event-by-event basis, to simultaneously identify, in terms of their mass and atomic numbers, the fissioning nucleus in coincidence with both fission fragments after prompt-neu...
We demonstrate a new technique for obtaining fission data for nuclei away from β stability. These types of data are pertinent to the astrophysical r process, crucial to a complete understanding of the origin of the heavy elements, and for developing a predictive model of fission. These data are also important considerations for terrestrial applicat...
We demonstrate a new technique for obtaining fission data for nuclei away from $\beta$-stability. These types of data are pertinent to the astrophysical \textit{r-}process, crucial to a complete understanding of the origin of the heavy elements, and for developing a predictive model of fission. These data are also important considerations for terre...
We present the design, prototype developments and test results of the new time-of-flight detector (ToFD) which is part of the R3B experimental setup at GSI and FAIR, Darmstadt, Germany. The ToFD detector is able to detect heavy-ion residues of all charges at relativistic energies with a relative energy precision $$\sigma _{\varDelta E}/{\varDelta E...
Deuteron elastic scattering from C15 and inelastic scattering reactions to the first excited state of C15 were studied using a radioactive beam of C15 in inverse kinematics. The scattered deuterons were measured using HELIOS. The elastic scattering differential cross sections were analyzed using the optical model. A matter deformation length δd=1.0...
Tracking the evolution of nuclear properties away from stability serves as a valuable test for nuclear models. In the present work, the (p,n) charge-exchange reaction was used to test the extraction of β− Gamow-Teller transition strengths, B(GT), from proton-rich unstable isotopes, and the resulting B(GT) values were compared to shell-model and ab...
Charge-exchange $(d,{}^{2}\text{He})$ reactions in inverse kinematics at intermediate energies are a very promising method to investigate the Gamow-Teller transition strength in unstable nuclei. A simulation and analysis software based on the $\rm{\scriptsize ATTPCROOT}$ package was developed to study these type of reactions with the active-target...
For the first time, the $(d,{}^2\text{He})$ reaction was successfully used in inverse kinematics to extract the Gamow-Teller transition strength in the $\beta^{+}$ direction from an unstable nucleus. The nucleus studied was $^{14}$O, and the Gamow-Teller transition strength to $^{14}$N was extracted up to an excitation energy of 22 MeV. The measure...
Absolute cross sections for the addition of s- and d-wave neutrons to C14 and N14 have been determined simultaneously via the (d,p) reaction at 10 MeV/u. The difference between the neutron and proton separation energies, ΔS, is around −20 MeV for the C14+n system and +8 MeV for N14+n. The population of the 1s1/2 and 0d5/2 orbitals for both systems...
The root mean square radii of the proton density distribution in O16–24 derived from measurements of charge changing cross sections with a carbon target at ∼900A MeV together with the matter radii portray thick neutron skin for O22–24 despite O22,24 being doubly magic. Imprints of the shell closures at N=14 and 16 are reflected in local minima of t...
Deuteron elastic scattering from 15C and inelastic scattering reactions to the first excited state of 15C were studied using a radioactive beam of 15C in inverse kinematics. The scattered deuterons were measured using HELIOS. The elastic scattering differential cross sections were analyzed using the optical model. A matter deformation length {\delt...
The root mean square radii of the proton density distribution in $^{16-24}$O derived from measurements of charge changing cross sections with a carbon target at $\sim$900$A$ MeV together with the matter radii portray thick neutron skin for $^{22 - 24}$O despite $^{22,24}$O being doubly magic. Imprints of the shell closures at $N$ = 14 and 16 are re...
Mean values of the number of protons and neutrons of the primary fission fragments at scission are determined for the asymmetric fission of 16 fissioning isotopes, from Ac219 up to Np238. Our results confirm that the main asymmetric fission mode around the heavier uranium isotopes is indeed characterized by an average atomic number around 〈ZH〉=54 i...
The fragment separator FRS has been used for the first time to measure the (n, p)- and (p, n)-type isobaric charge-exchange cross sections of stable 112,124Sn isotopes accelerated at 1A GeV with an uncertainty of 3% and to separate quasielastic and inelastic components in the missing-energy spectra of the ejectiles. The inelastic contribution can b...
Absolute cross sections for the addition of $s$- and $d$-wave neutrons to $^{14}$C and $^{14}$N have been determined simultaneously via the ($d$,$p$) reaction at 10 MeV/u. The difference between the neutron and proton separation energies, $\Delta S$, is around $-20$ MeV for the $^{14}$C$+$$n$ system and $+8$ MeV for $^{14}$N$+$$n$. The population o...
A narrow near-threshold proton-emitting resonance (E_{x}=11.4 MeV, J^{π}=1/2^{+}, and Γ_{p}=4.4 keV) was directly observed in ^{11}B via proton resonance scattering. This resonance was previously inferred in the β-delayed proton emission of the neutron halo nucleus ^{11}Be. The good agreement between both experimental results serves as a ground to...
The isomeric state of N16 was studied using the N16g,m(d,He3) proton-removal reactions at 11.8 MeV/u in inverse kinematics. The N16 beam, of which 24% was in the isomeric state, was produced using the Argonne Tandem-Linac Accelerator System (ATLAS) in-flight system and delivered to the Helical Orbit Spectrometer (HELIOS), which was used to analyze...
A narrow near-threshold proton-emitting resonance (Ex = 11.4 MeV, J$^{\pi}$ = 1/2$^{+}$ and $\Gamma_{p}$ = 4.4 keV) was directly observed in $^{11}$B via proton resonance scattering. This resonance was previously inferred in the $\beta$-delayed proton emission of the neutron halo nucleus $^{11}$Be. The good agreement between both experimental resul...
The ^{30}P(p,γ)^{31}S reaction plays an important role in understanding the nucleosynthesis of A≥30 nuclides in oxygen-neon novae. The Gaseous Detector with Germanium Tagging was used to measure ^{31}Cl β-delayed proton decay through the key J^{π}=3/2^{+}, 260-keV resonance. The intensity I_{βp}^{260}=8.3_{-0.9}^{+1.2}×10^{-6} represents the weakes...
The $^{30}$P$(p,\gamma)^{31}$S reaction plays an important role in understanding nucleosynthesis of $A\geq 30$ nuclides in oxygen-neon novae. The Gaseous Detector with Germanium Tagging was used to measure $^{31}$Cl $\beta$-delayed proton decay through the key $J^{\pi}=3/2^{+}$, 260-keV resonance. The intensity $I^{260}_{\beta p} = 8.3^{+1.2}_{-0.9...
Recoil imaging entails the detection of spatially resolved ionization tracks generated by particle interactions. This is a highly sought-after capability in many classes of detector, with broad applications across particle and astroparticle physics. However, at low energies, where ionization signatures are small in size, recoil imaging only seems t...
An in-flight beam of ¹⁶N was produced via the single-neutron adding (d, p) reaction in inverse kinematics at the recently upgraded Argonne Tandem Linear Accelerator System (ATLAS) in-flight system. The amount of the ¹⁶N beam which resided in its excited 0.120-MeV Jπ=0− isomeric state (T1/2≈5 μs) was determined to be 40(5)% at a reaction energy of 7...
A challenge preventing successful inverse kinematics measurements with heavy nuclei that are not fully stripped is identifying and tagging the beam particles. For this purpose, the HEavy ISotope Tagger (HEIST) has been developed. HEIST utilizes two micro-channel plate timing detectors to measure the time-of-flight, a multi-sampling ion chamber to m...
An in-flight beam of $^{16}$N was produced via the single-neutron adding ($d$,$p$) reaction in inverse kinematics at the recently upgraded Argonne Tandem Linear Accelerator System (ATLAS) in-flight system. The amount of the $^{16}$N beam which resided in its excited 0.120-MeV $J^{\pi}=0^-$ isomeric state (T$_{1/2}\approx5$ $\mu$s) was determined to...
O( α , γ ) ¹⁹ Ne is regarded as one of the most important thermonuclear reactions in type I X-ray bursts. For studying the properties of the key resonance in this reaction using β decay, the existing Proton Detector component of the Gaseous Detector with Germanium Tagging (GADGET) assembly is being upgraded to operate as a time projection chamber (...
Sensitivity studies have shown that the ¹⁵ O(α, γ) ¹⁹ Ne reaction is the most important reaction rate uncertainty affecting the shape of light curves from Type I X-ray bursts. This reaction is dominated by the 4.03 MeV resonance in ¹⁹ Ne. Previous measurements by our group have shown that this state is populated in the decay sequence of ²⁰ Mg. A si...
The isomeric state of $^{16}$N was studied using the $^{16}$N$^{g,m}$($d$,$^3$He)~proton-removal reactions at \mbox{11.8~MeV/$u$} in inverse kinematics. The $^{16}$N beam, of which 25% was in the isomeric state, was produced using the ATLAS in-fight facility and delivered to the HELIOS spectrometer, which was used to analyze the $^{3}$He ions from...
The fragment separator FRS has been for the first time used to measure the (n,p) and (p,n)-type isobaric charge-exchange cross sections of stable 112,124Sn isotopes accelerated at 1A GeV with an uncertainty of 3% and to separate quasi-elastic and inelastic components in the missing-energy spectra of the ejectiles. The inelastic contribution can be...
We introduce the concept of neutron-proton two-particle units (np-Weisskopf units) to be used in the analysis of the (³He,p) and (p,3He) reactions on nuclei along the N=Z line. These are presented for the conditions relevant to the (n,j,ℓ) orbits expected from ¹⁶O to ¹⁰⁰Sn. As is the case of the Weisskopf units for electromagnetic transitions, the...
Low-energy fission of 234,235 U and 237,238 Np radioactive beams, provided by the Fragment Separator (FRS) of the GSI Helmholtzzentrum für Schwerionenforschung facility (GSI), has been studied using the Reactions with Relativistic Radioactive Beams / Studies on Fission with Aladin (R3B/SOFIA) setup. The latter allows us, on an event-by-event basis,...
We introduce the concept of neutron-proton two-particle units ($np$-Weisskopf units) to be used in the analysis of the ($^3$He,$p)$ and $(p,^3$He) \added{reactions on nuclei} along the N=Z line. These are presented for the conditions relevant to the $(n,j,\ell$) orbits expected from $^{16}$O to $^{100}$Sn. As is the case of the Weisskopf units for...
The discrepancy between observations from γ-ray astronomy of the Fe60/Al26 γ-ray flux ratio and recent calculations is an unresolved puzzle in nuclear astrophysics. The stellar β-decay rate of Fe59 is one of the major nuclear uncertainties impeding us from a precise prediction. The important Gamow-Teller strengths from the low-lying states in Fe59...
A resonant state at 3.21−0.04+0.12MeV, located just above the one-neutron separation threshold, was observed for the first time in Be12 from the Be11(d,p)Be12 one-neutron transfer reaction in inverse kinematics. This state is assigned a spin-parity of 0− according to the systematics of the level scheme of the N=8 isotones and decay-width analysis....
A resonant state at $3.21^{+0.12}_{-0.04}$\,MeV, located just above the one-neutron separation threshold, was observed for the first time in $^{12}$Be from the $^{11}$Be\,$(d,p)^{12}$Be one-neutron transfer reaction in inverse kinematics. This state is assigned a spin-parity of $0^-$, according to the distorted-wave Born approximation (DWBA) and de...
Isobaric charge-exchange reactions induced by beams of 112 Sn have been investigated at the GSI facility using the fragment separator FRS. The high-resolving power of this spectrometer makes it possible to obtain the isobaric charge-exchange cross sections with an uncertainty of 3.5% and to separate quasi-elastic and inelastic contributions in the...
Type-I x-ray bursts can reveal the properties of an accreting neutron star system when compared with astrophysics model calculations. However, model results are sensitive to a handful of uncertain nuclear reaction rates, such as Mg22(α,p). We report the first direct measurement of Mg22(α,p), performed with the Active Target Time Projection Chamber....
Isobaric charge-exchange reactions induced by beams of ¹¹² Sn have been investigated at the GSI facilities using the fragment separator FRS. The high-resolving power of this spectrometer makes it possible to obtain the isobaric charge-exchange cross sections with an accuracy of 3% and to separate quasi-elastic and inelastic contributions in the mis...
Isobaric charge-exchange reactions induced by beams of 112Sn have been investigated at the GSI facilities using the fragment separator FRS. The high-resolving power of this spectrometer makes it possible to obtain the isobaric charge-exchange cross sections with an accuracy of 3% and to separate quasi-elastic and inelastic contributions in the miss...
Isobaric single charge-exchange reaction, changing nuclear charges by one unit but leaving the mass partitions unaffected, have been for the first time investigated by peripheral collisions of ¹¹²Sn ions accelerated up to 1A GeV at the GSI facilities. The high-resolving power of the FRS spectrometer allows us to obtain (p,n)-type isobaric charge-ex...
Taking benefit of the R3B=SOFIA setup to measure the mass and the nuclear charge of both fission fragments in coincidence with the total prompt-neutron multiplicity, the scission configurations are inferred along the thorium chain, from the asymmetric fission in the heavier isotopes to the symmetric fission in the neutron-deficient thorium. Against...
This article aims at covering various themes that can benefit from taking advantage of active target time projection chambers. They are naturally oriented towards the study of short-lived radioactive nuclei, for which high efficiency and thick targets are necessary to boost the luminosity of the experiments due to the weak intensity of the availabl...
Isobaric charge-exchange reactions induced by peripheral collisions of 112Sn ions accelerated up to 1A GeV have been for the first time investigated at the GSI facilities. The high-resolving power of the FRS spectrometer allows to obtain (p, n)-type isobaric charge-exchange cross sections with an uncertainty of 3.5% and to separate quasi-elastic an...
DOI:https://doi.org/10.1103/PhysRevLett.124.129902
Isobaric charge-exchange reactions induced by ions of 112;124Sn at energies of 1AGeV have beeninvestigated at GSI. The high-resolving power of the FRS spectrometer makes it possible to obtainthe isobaric charge-exchange cross sections with an accuracy of 3% and to separate quasi-elasticand inelastic components in the missing-energy spectra of the e...
Type-I X-ray burst (XRB) light curves are sensitive to the model’s nuclear input and consequently affects the model-observation comparisons. 22Mg(α,p)25Al is among the most important reactions which directly impact the XRB light curve. We report the first direct measurement of 22Mg(α,p)25Al using the Active Target Time Projection Chamber. XRB light...
The performance of a novel tracking detector developed for the focal plane of the NSCL/FRIB S800 magnetic spectrometer is presented. The detector comprises a large-area drift chamber equipped with a hybrid Micro-Pattern Gaseous Detector (MPGD)-based readout. The latter consists of a position-sensitive Micromegas detector preceded by a two-layer M-T...
Isobaric charge-exchange reactions induced by beams of 112 Sn have been investigated at the GSI facilities using the fragment separator FRS. The high-resolving power of this spectrometer makes it possible to obtain the isobaric charge-exchange cross sections with an accuracy of 3% and to separate quasi-elastic and inelastic contributions in the mis...
Elastic and inelastic alpha scatterings on C10 were measured using a 68-MeV/u radioactive C10 beam incident on the recently developed MAIKo active target system. The phenomenological effective α−N interaction and the point-nucleon density distribution in the ground state were determined from the elastic scattering data. The cross sections of the in...
Tracking capabilities in Time Projection Chambers (TPCs) are strongly dictated by the homogeneity of the drift field. Ion back-flow in various gas detectors, mainly induced by the secondary ionization processes during amplification, has long been known as a source of drift field distortion. Here, we report on beam-induced space-charge effects from...
The elusive β−p+ decay was observed in Be11 by directly measuring the emitted protons and their energy distribution for the first time with the prototype Active Target Time Projection Chamber in an experiment performed at ISAC-TRIUMF. The measured β−p+ branching ratio is orders of magnitude larger than any previous theoretical model predicted. This...
The elastic and inelastic alpha scatterings on $^{10}$C were measured using a 68-MeV/u radioactive $^{10}$C beam incident on the recently developed MAIKo active target system. The phenomenological $\alpha$-$N$ effective interaction and the point-nucleon density distribution in the ground state were determined from the elastic scattering data. The c...
Tracking capabilities in Time Projection Chambers (TPCs) are strongly dictated by the homogeneity of the drift field. Ion back-flow in various gas detectors, mainly induced by the secondary ionization processes during amplification, has long been known as a source of drift field distortion. Here, we report on beam-induced space-charge effects from...
The elusive β − p + decay was observed in 11 Be by directly measuring the emitted protons and their energy distribution for the first time with the prototype Active Target Time Projection Chamber (pAT-TPC) in an experiment performed at ISAC-TRIUMF. The measured β − p + branching ratio is orders of magnitude larger than any previous theoretical mode...
The neutron-rich isotopes Tl211,213, beyond the N=126 shell closure, have been studied for the first time in isomer γ-ray decay, exploiting the fragmentation of a primary uranium beam at the Fragment Separator-Rare Isotopes Investigation at GSI setup. The observed isomeric states in Tl211,213 show a deviation from the seniority-like scheme of Tl209...
The inverse kinematics technique, applied to radioactive beams and combined to the Coulomb excitation method, is a powerful tool to study low-energy fission. A novel experimental set-up was developped within the R3B/SOFIA (Reactions with Relativistic Radioactive Beams / Studies On FIssion with Aladin) collaboration to identify in mass and atomic nu...
A thick neutron skin emerges from the first determination of root mean square radii of the proton distributions for $^{17-22}$N from charge changing cross section measurements around 900$A$ MeV at GSI. Neutron halo effects are signaled for $^{22}$N from an increase in the proton and matter radii. The radii suggest an unconventional shell gap at $N$...
The reactions 136Xe + p and 136Xe + 12C have been studied in inverse kinematics at 1 A GeV with the SPALADiN setup at GSI. The detection in coincidence of the final-state charged particles (projectile residues, nuclei of charge Z≥2 and neutrons was performed with a big-aperture dipole magnet and large-acceptance detectors. This provided an extended...
Measurement of root-mean-square radii of proton distributions of 17–22 N from charge-changing cross section shows the emergence of thick neutron skin towards the neutron-drip line. Signature of N = 14 shell gap has been found in nitrogen isotopes along with the emergence of neutron halo in ²² N. The measured radii are in good agreement with the she...
we describe a novel gaseous detector concept for heavy-ion tracking and imaging: the Optical Parallel-Plate Avalanche Counter (O-PPAC). The detector consists of two thin parallel-plate electrodes separated by a small (typically 3 mm) gap filled with low-pressure scintillating gas (i.e. CF4). The localization of the impinging particles is achieved b...
The Active Target Time Projection Chamber (AT-TPC) project at the National Superconducting Cyclotron Laboratory (NSCL) is a novel Active Target designed to study nuclear reactions induced by low-intensity exotic beams. The AT-TPC acts as a tracking medium and target at the same time, providing excellent angular (1[Formula presented]) and energy res...
Many nuclear structure studies are presently performed with secondary radioactive beams to explore the nuclear chart far from stability. This entails a large decrease of available intensities, as compared to stable beam experiments, even with the highest power primary beam accelerators. To compensate for this intensity loss, thick targets and high...
The automatic reconstruction of three-dimensional particle tracks from Active Target Time Projection Chambers data can be a challenging task, especially in the presence of noise. In this article, we propose a non-parametric algorithm that is based on the idea of clustering point triplets instead of the original points. We define an appropriate dist...
we describe a novel gaseous detector concept for heavy-ion tracking and imaging: the Optical Parallel-Plate Avalanche Counter (O-PPAC). The detector consists of two thin parallel-plate electrodes separated by a small (typically 3 mm) gap filled with low-pressure scintillating gas (i.e. CF4). The localization of the impinging particles is achieved b...