Studies for a 72.75 MHz Four Vanes CW-RFQ for ECOS-LINCE Project

Presented at the XXXIV Mazurian Lakes Conference on Physics, Piaski, Poland, September 6–13, 2015.The ECOS is considering the construction of a new facility for accelerating high intensity stable beams with energies at and above the Coulomb barrier, the LINCE light and heavy ion accelerator. This facility could be based on a normal conducting CW-RFQ and a superconducting linac, working at 72.75 MHz. This paper presents a design study for the RFQ system which is able to achieve 500 keV/u output for A=Q = 7 ions in only 5 m length

Observation and Spectroscopy of New Proton-Unbound Isotopes 30Ar and 29Cl: An Interplay of Prompt Two-Proton and Sequential Decay

Previously unknown isotopes Ar30 and Cl29 have been identified by measurement of the trajectories of their in-flight decay products S28+p+p and S28+p, respectively. The analysis of angular correlations of the fragments provided information on decay energies and the structure of the parent states. The ground states of Ar30 and Cl29 were found at 2.25+0.15−0.10 and 1.8±0.1  MeV above the two- and one-proton thresholds, respectively. The lowest states in Ar30 and Cl29 point to a violation of isobaric symmetry in the structure of these unbound nuclei. The two-proton decay has been identified in a transition region between simultaneous two-proton and sequential proton emissions from the Ar30 ground state, which is characterized by an interplay of three-body and two-body decay mechanisms. The first hint of a fine structure of the two-proton decay of Ar∗30(2+) has been obtained by detecting two decay branches into the ground and first-excited states of the S28 fragment.A. G., S. K., S. R., and P. S. were supported by the Helmholtz Association Grant No. IK-RU-002. L. V. G. was partly supported by the Ministry of Education and Science of the Russian Federation Grant No. NSh- 932.2014.2. A. F., A. G., L. V. G., S. K., P. S., and R. S. were partly supported by the Russian Foundation for Basic Research Grant No. 14-02-00090-a. This work was partly supported by the Polish National Science Center under Contract No. UMO-2011/01/B/ST2/01943. A. A. C. acknowledges support by the Polish Ministry of Science and Higher Education by Grant No. 0079/DIA/ 2014/43 (Grant Diamentowy). M. P. and X. X. are grateful for a support from the Helmholtz International Center for FAIR (HIC for FAIR). Y. L. was supported by the Helmholtz-CAS Joint Research Group Grant No. HCJRG- 108. J. M. E. acknowledges support from the FPA2009- 08848 contract (MICINN, Spain

\b{eta}-delayed three-proton decay of 31Ar

The beta decay of 31Ar, produced by fragmentation of a 36Ar beam at 880 MeV/nucleon, was investigated. Identified ions of 31Ar were stopped in a gaseous time projection chamber with optical readout allowing to record decay events with emission of protons. In addition to \b{eta}-delayed emission of one and two protons we have clearly observed the beta-delayed three-proton branch. The branching ratio for this channel in 31Ar is found to be 0.07(2)%.Comment: 5 pages, 3 figures, submitted to Physical Rev.

ECOS-LINCE : a high-intensity heavy-ion facility for nuclear structure and reactions

Presented at the XXXIV Mazurian Lakes Conference on Physics, Piaski, Poland, September 6–13, 2015During the last years, the ECOS working group has been considering the construction of a new high-intensity accelerator of stable ion beams for the next Long-Range Plan of the nuclear physics community in Europe. The new facility (LINCE) will be a multi-user facility dedicated to ECOS science: fundamental physics, astrophysics, nuclear structure and reaction dynamics. In this paper, we summarize preliminary design studies of the low-energy part of this facility based on the use of a multi-ion supercon- ducting linac.Work partially supported by the Spanish Government under the grant Feder-Interconnecta “Aceltec” ITC-20111070. The authors are also grateful to the companies Alter Technology-Tüv, Avs, Cibernos, Elitt Energy, Faysol, Idom, and Tti Norte for partial funding of this work and active participation in the design and prototyping carried-out in this study

Study of an Ion Beam Accelerator for the LINAC Research Center in Spain

This thesis focuses on the study of an ion beam accelerator for the LINAC Research Center (LINCE) in Spain. The proposed superconducting LINAC operates at 72.75MHz and is designed to accelerate, in a first phase, light and heavy ions with mass-to-charge ratio in the range A/Q = 1 to 7 and beam energies from 500 keV/n to about 8MeV/n for heavy ions, and 40MeV for protons. LINCE developed from a previous project, the Linac Research Facility (LRF), an initiative to install a high-intensity, light- and heavy-Ion accelerator in the University of Huelva (Spain). The facility would be dedicated to basic nuclear research and multidisciplinary applications, notably using a high-intensity proton beam for radioisotope production of medical interest. Therefore, the main challenge of this thesis has been to devise a multi-ion LINAC accelerator capable of producing both high-intensity protons and heavy-ions with large A/Q. LINCE and LRF gathered a wide community of nuclear physicists and industrial shareholders from Spain and abroad, which contributed to different R&D activities coordinated by the local team at the University of Huelva. This thesis details the beam dynamics of the LINAC and the design of selected accelerator elements, with special emphasis in a key element of the facility: the radiofrequency quadrupole (RFQ). The codes TRACK, DESRFQ and MAD-X have been used for particle tracking simulations, COMSOL MULTIPHYSICS for radio-frequency (RF), thermal and structural analysis, and AUTOCAD INVENTOR for the mechanical design. This document is presented in seven chapters that cover beam dynamics studies, the design of accelerator elements, geometry models, RF simulations, and engineering studies of the structure including heating, cooling and mechanical displacements.En el presente trabajo, se propone un acelerador superconductor LINAC que utilice tecnología punta para producir haces de iones pesados de alta intensidad de hasta alrededor de 8MeV/n y de protones de aproximadamente 40MeV. Se estudia la dinámica del haz de dicho acelerador y, en particular, se ha prestado especial atención al desarrollo de un nuevo diseño para un inyector cuadrupolo de radiofrecuencia (RFQ) a temperatura ambiente para el LINAC propuesto. Los cuadrupolos de radiofrecuencia (RFQ) son componentes esenciales de los aceleradores modernos de alta intensidad; se utilizan para agrupar, pre-acelerar y optimizar las características del haz antes de ser inyectadas en cavidades aceleradoras de radio frecuencia. Esta tesis presenta los estudios teóricos y el modelado de una RFQ de cuatro vanos que opera en 72.75MHz, diseñada para acelerar iones en el rango de relación masa/carga AIQ = 1 - 1/7, de 40 keV/u a 500 keV/u. La primera parte de este estudio se enfocó en el estudio de la dinámica de haz para el acelerador en general, desde la fuente de iones hasta ras cavidades superconductoras, utilizando una selección de iones y energías, y los parámetros del haz (intensidad, emitancia transversal y longitudinal, longitud, etc.) requeridos por el programa científico. Esto define el diseño de la instalación y las características principales de las líneas de transporte de haz y los elementos de aceleración, como por ejemplo la RFQ y las cavidades superconductoras de radio frecuencia. Las características del haz en la fuente de iones se obtuvieron del modelo Supernanogam de Pantechnik, una fuente de iones múltiples de alta intensidad ampliamente utilizada en aceleradores de iones pesados. Después de haber establecido las características principales y los rangos de los parámetros para los haces a la entrada/salida de la RFQ, fa tesis continúa con un estudio electromagnético y técnico detallado, que incluye deformaciones térmicas y análisis de errores de mecanizado. El diseño se llevó a cabo utilizando los códigos TRACK y DESRFQ y MAD-X para las simulaciones de seguimiento y transporte de iones, COMSOL MULTIPHYSIC para los análisis térmicos, estructurales y de radiofrecuencia e INVENTOR para el diseño mecánico. El estudio para el diseño del acelerador se compaginó con la contribución de determinadas mediciones de física nuclear en las principales instalaciones de aceleradores de la UE (LNL, HIE-ISOLDE y GSI). Esto brindó la oportunidad de aprender aspectos relevantes de la operación y puesta en marcha de un LINAC, así como la posibilidad de familiarizarse con los principales parámetros de los detectores y las características de haz solicitadas por los físicos nucleares. Esta información fue extremadamente útil para definir los parámetros de diseño de ECOS-LINCE y, en particular, para el sistema de RFQ. La tesis se presenta en siete capítulos; una breve descripción de su contenido es presentado a continuación. El Capítulo 1 contiene una introducción del proyecto LINCE y sus aplicaciones, donde se presta especial atención a la investigación en medicina. Los principales parámetros y requisitos de diseño para LINCE se presentan en el Capitulo 2. En el Capitulo 3 se describen los fundamentos de los aceleradores de radiofrecuencia y de la RFQ, así como la metodología y las herramientas utilizadas para realizar el estudio. El estudio de dinámica de haz para todo el acelerador se presenta en el Capitulo 4. Se incluyen los parámetros relevantes del mis[Ylo y un estudio detallado de aceleración de protones e iones pesados a través de LINCE. El capitulo 5 está dedicado al diseño de la RFQ. Las primeras tres secciones contienen el estudio específico de dinámica de haz, el modelado electromagnético, y los análisis térmicos y estructurales para el modelo de cuatro vanos de 72.75MHz. Este estudio incluye el diseño de los canales de refrigeración, y los resultados para la transmisión de calor, stress mecánico, deformaciones y cambios de frecuencia. La última sección está dedicada al diseño de una RFQ de cuatro barras de 200MHz para la aceleración de protones e iones ligeros (A/Q = 3). En el capitulo 6 se presenta el proceso seguido para la construcción de los prototipos. Este capítulo describe el proceso de fabricación de los modelos de aluminio y cobre, y los resultados de las pruebas de radiofrecuencia. Finalmente, se presenta un resumen de la tesis junto con las conclusiones más importantes en el capítulo 7

Towards the Limits of Existence of Nuclear Structure: Observation and First Spectroscopy of the Isotope 31K by Measuring Its Three-Proton Decay

The most remote isotope from the proton dripline (by 4 atomic mass units) has been observed: 31K. It is unbound with respect to three-proton (3 p ) emission, and its decays have been detected in flight by measuring the trajectories of all decay products using microstrip detectors. The 3 p emission processes have been studied by the means of angular correlations of 28S +3 p and the respective decay vertices. The energies of the previously unknown ground and excited states of 31K have been determined. This provides its 3 p separation energy value S3 p of -4.6 (2 ) MeV . Upper half-life limits of 10 ps of the observed 31K states have been derived from distributions of the measured decay vertices.This work was supported in part by the Helmholtz International Center for FAIR (HIC for FAIR); the Helmholtz Association (Grant No. IK-RU-002); the Russian Science Foundation (Grant No. 17-12-01367); the Polish National Science Center (Contract No. UMO2015/17/B/ST2/00581); the Polish Ministry of Science and Higher Education (Grant No. 0079/DIA/2014/43, Grant Diamentowy); the Helmholtz-CAS Joint Research Group (Grant No. HCJRG-108); the Ministry of Education & Science, Spain (Contract No. FPA2016-77689- C2-1-R); the Hessian Ministry for Science and Art (HMWK)through the LOEWE funding scheme; the Ministry of Education, Youth and Sports, Czech Republic (Projects LTT17003 and LM2015049); the JustusLiebig-Universit¨at Giessen (JLU) and the GSI under the JLU-GSI strategic Helmholtz partnership agreement; DGAPA-PAPIIT UNAM IA103218. This work was carried out in the framework of the Super-FRS Experiment Collaboration. This article is a part of the Ph.D. thesis of D. Kostyleva

Spectroscopy of excited states of unbound nuclei 30Ar and 29Cl

Several states of proton-unbound isotopes 30Ar and 29Cl were investigated by measuring their in-flight decay products, 28S + proton + proton and 28S + proton, respectively. A refined analysis of 28S-proton angular correlations indicates that the ground state of 30Ar is located at 2.45+0.05-0.10 MeV above the two-proton emission threshold. The investigation of the decay mechanism of the 30Ar ground state demonstrates that it has the transition dynamics. In the “transitional” region, the correlation patterns of the decay products present a surprisingly strong sensitivity to the two-proton decay energy of the 30Ar ground state and the one-proton decay energy as well as the one-proton decay width of the 29Cl ground state. The comparison of the experimental 28S-proton angular correlations with those resulting from Monte Carlo simulations of the detector response illustrates that other observed 30Ar excited states decay by sequential emission of protons via intermediate resonances in 29Cl. Based on the findings, the decay schemes of the observed states in 30Ar and 29Cl were constructed. For calibration purposes and for checking the performance of the experimental setup, decays of the previously known states of a two-proton emitter 19Mg were remeasured. Evidences for one new excited state in 19Mg and two unknown states in 18Na were found.This work was supported in part by the Helmholtz International Center for FAIR (HIC for FAIR), the Helmholtz Association (grant IK-RU-002), the Russian Ministry of Education and Science (grant No. NSh- 932.2014.2), the Russian Science Foundation (grant No. 17-12-01367), the Polish National Science Center (Contract No. UMO-2011/01/B/ST2/01943), the Polish Ministry of Science and Higher Education (Grant No. 0079/DIA/2014/43,Grant Diamentowy), the Helmholtz- CAS Joint Research Group (grant HCJRG-108), the FPA2009-08848 contract (MICINN, Spain), the Justus- Liebig-Universit¨at Gießen (JLU) and GSI under the JLUGSI strategic Helmholtz partnership agreement. This article is a part of PhD thesis of X.-D. Xu. The authors acknowledge the help of D. Kostyleva in the preparation of the manuscript.This work was supported in part by the Helmholtz International Center for FAIR (HIC for FAIR), the Helmholtz Association (Grant No. IK-RU-002), the Russian Ministry of Education and Science (Grant No. NSh-932.2014.2), the Russian Science Foundation (Grant No. 17-12-01367), the Polish National Science Center (Contract No. UMO-2011/01/B/ST2/01943), the Polish Ministry of Science and Higher Education (Grant No. 0079/DIA/2014/43, Grant Diamentowy), the Helmholtz-CAS Joint Research Group (Grant No. HCJRG-108), the FPA2009-08848 contract (MICINN, Spain), and the Justus-Liebig-Universitat Giessen (JLU) and GSI under the JLU-GSI strategic Helmholtz partnership agreement. This article is a part of the Ph.D. thesis of X.-D. Xu. The authors acknowledge the help of D. Kostyleva in the preparation of the manuscript

Spectroscopy of excited states of unbound nuclei 30^{30}Ar and 29^{29}Cl

Several states of proton-unbound isotopes $^{30}$Ar and $^{29}$Cl were investigated by measuring their in-flight decay products, $^{28}$S+proton+proton and $^{28}$S+proton, respectively. A refined analysis of $^{28}$S-proton angular correlations indicates that the ground state of $^{30}$Ar is located at $2.45^{+0.05}_{-0.10}$ MeV above the two-proton emission threshold. The theoretical investigation of the $^{30}$Ar ground state decay demonstrates that its mechanism has the transition dynamics with a surprisingly strong sensitivity of the correlation patterns of the decay products to the two-proton decay energy of the $^{30}$Ar ground state and the one-proton decay energy as well as the one-proton decay width of the $^{29}$Cl ground state. The comparison of the experimental $^{28}$S-proton angular correlations with those resulting from Monte Carlo simulations of the detector response illustrates that other observed $^{30}$Ar excited states decay by sequential emission of protons via intermediate resonances in $^{29}$Cl. Based on the findings, the decay schemes of the observed states in $^{30}$Ar and $^{29}$Cl were constructed. For calibration purposes and for checking the performance of the experimental setup, decays of the previously-known states of a two-proton emitter $^{19}$Mg were remeasured. Evidences for one new excited state in $^{19}$Mg and two unknown states in $^{18}$Na were found

Deep excursion beyond the proton dripline. II. Toward the limits of existence of nuclear structure

Prospects of experimental studies of argon and chlorine isotopes located far beyond the proton dripline are studied by using systematics and cluster models. The deviations from the widespread systematics observed in $^{28,29}$Cl and $^{29,30}$Ar have been theoretically substantiated, and analogous deviations predicted for the lighter chlorine and argon isotopes. The limits of nuclear structure existence are predicted for Ar and Cl isotopic chains, with $^{26}$Ar and $^{25}$Cl found to be the lightest sufficiently long-living nuclear systems. By simultaneous measurements of protons and $\gamma$-rays following decays of such systems as well as their $\beta$-delayed emission, an interesting synergy effect may be achieved, which is demonstrated by the example of $^{30}$Cl and $^{31}$Ar ground state studies. Such synergy effect may be provided by the new EXPERT setup (EXotic Particle Emission and Radioactivity by Tracking), being operated inside the fragment separator and spectrometer facility at GSI, Darmstadt.Comment: 10 pages, 9 figures. Chapter added, language and some figures correcte