The accuracy of the predictions of the γ flux produced by a classical nova during the first hours after the outburst is limited by the uncertainties on several reaction rates, including the 18F(p,α)15O one. Better constraints on this reaction rate can be obtained by determining the spectroscopic properties of the compound nucleus 19Ne. This was achieved in a new inelastic scattering method using a 19Ne radioactive beam (produced by the GANIL-SPIRAL 1 facility) impinging onto a proton target. The experiment was performed at the VAMOS spectrometer. In this article the performances (excitation energy range covered and excitation energy resolution) and limitations of the new technique are discussed. Excitation energy resolution of σ = 33 keV and low background were obtained with this inverse kinematics method, which will allow extracting the spectroscopic properties of 19Ne

Achouri, N. L.

Acosta, L

Bastin, B.

Borcea, C

Boulay, F.

Ciemala, M.

Davinson, T

de France, G

De Oliveira Santos, F.

Delahaye, P.

Estrade, A.

Grinyer, J.

Jacquot, B.

Kamalou, O.

Laird, A.

Lemasson, A.

Margerin, V.

Marquinez-Duran, G.

Mrazek, J.

Negoita, F

Ramos, D.

Rejmund, M.

Rodriguez-Tajes, C.

Rotaru, F.

Schmitt, C.

Sorlin, O

Stanoiu, M

Sánchez-Benítez, A. M.

Séréville, N. de

Thomas, J. C.

Traykov, E.

Ujic, P.

Woods, P. J.

Journal of Physics : Conference Series

International audienceThe accuracy of the predictions of the γ flux produced by a classical nova during the first hours after the outburst is limited by the uncertainties on several reaction rates, including the 18F(p,α)15O one. Better constraints on this reaction rate can be obtained by determining the spectroscopic properties of the compound nucleus 19Ne. This was achieved in a new inelastic scattering method using a 19Ne radioactive beam (produced by the GANIL-SPIRAL 1 facility) impinging onto a proton target. The experiment was performed at the VAMOS spectrometer. In this article the performances (excitation energy range covered and excitation energy resolution) and limitations of the new technique are discussed. Excitation energy resolution of σ = 33 keV and low background were obtained with this inverse kinematics method, which will allow extracting the spectroscopic properties of 19Ne

de Oliveira Santos, F.

Davinson, T.

Sanchez-Benitez, A.M.

Achouri, L.

Acosta, L.

Borcea, C.

De France, G.

Negoita, F.

De Séréville, N.

Sorlin, O.

Stanoiu, M.

Thomas, J.C.

Woods, P.J.

Hal-Diderot

Measurement of $^{19}$Ne spectroscopic properties via a new method of inelastic scattering to study novae

HAL Descartes

The accuracy of the predictions of the γ flux produced by a classical nova during the first
hours after the outburst is limited by the uncertainties on several reaction rates, including the
18F(p,α)15O one. Better constraints on this reaction rate can be obtained by determining the
spectroscopic properties of the compound nucleus 19Ne. This was achieved in a new inelastic
scattering method using a 19Ne radioactive beam (produced by the GANIL-SPIRAL 1 facility)
impinging onto a proton target. The experiment was performed at the VAMOS spectrometer. In
this article the performances (excitation energy range covered and excitation energy resolution)
and limitations of the new technique are discussed. Excitation energy resolution of σ=33
keV and low background were obtained with this inverse kinematics method, which will allow
extracting the spectroscopic properties of 19Ne

Oliveira Santos, F. de

Marquínez Durán, Gloria

Arias Montano: Institutional Repository of the University of Huelva

World Research Journal of Applied Physics

Measurement of 19Ne spectroscopic properties via a new method of inelastic scattering to study novae.

F. Boulay

B. Bastin

F. de Oliveira Santos

T. Davinson

A. Lemasson

P. Ujic

J. Mrazek

A. M. Sánchez-Benítez

E. Traykov

D. Ramos

L. Achouri

L. Acosta

C. Borcea

M. Ciemala

P. Delahaye

A. Estrade

G. de France

J. Grinyer

B. Jacquot

O. Kamalou

A. Laird

V. Margerin

G. Marquinez-Duran

F. Negoita

M. Rejmund

C. Rodriguez-Tajes

F. Rotaru

C. Schmitt

N. de Séréville

O. Sorlin

M. Stanoiu

J.C. Thomas

P.J. Woods

Crossref

Journal of Physics Conference Series

Measurement of <sup>19</sup>Ne spectroscopic properties via a new method of inelastic scattering to study novae

de France, G.

de Séréville, N.

HAL - Normandie Université

HAL-IN2P3

HAL-CEA

White Rose Research Online

This is a repository copy of Measurement of 19Ne spectroscopic properties via a new method of inelastic scattering to study novae.White Rose Research Online URL for this paper:http://eprints.whiterose.ac.uk/128315/Version: Published VersionArticle:Boulay, F., Bastin, B., De Oliveira Santos, F. et al. (30 more authors) (2018) Measurement of 19Ne spectroscopic properties via a new method of inelastic scattering to study novae. Journal of Physics: Conference Series. 012003. ISSN 1742-6596 https://doi.org/10.1088/1742-6596/940/1/012003eprints@whiterose.ac.ukhttps://eprints.whiterose.ac.uk/Reuse This article is distributed under the terms of the Creative Commons Attribution (CC BY) licence. This licence allows you to distribute, remix, tweak, and build upon the work, even commercially, as long as you credit the authors for the original work. More information and the full terms of the licence here: https://creativecommons.org/licenses/ Takedown If you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. Journal of Physics: Conference SeriesPAPER • OPEN ACCESSMeasurement of 19Ne spectroscopic properties via a new method ofinelastic scattering to study novaeTo cite this article: F. Boulay et al 2018 J. Phys.: Conf. Ser. 940 012003 View the article online for updates and enhancements.This content was downloaded from IP address 144.32.225.234 on 07/03/2018 at 10:311Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distributionof this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.Published under licence by IOP Publishing Ltd1234567890 ‘’“”Nuclear Physics in Astrophysics Conference (NPA VII) IOP PublishingIOP Conf. Series: Journal of Physics: Conf. Series 940 (2018) 012003  doi :10.1088/1742-6596/940/1/012003Measurement of 19Ne spectroscopic properties via anew method of inelastic scattering to study novae.F. Boulay1, B. Bastin1, F. de Oliveira Santos1, T. Davinson2, A.Lemasson1, P. Ujic3, J. Mrazek4, A. M. Sánchez-Beńıtez5,1, E.Traykov1, D. Ramos6, L. Achouri7, L. Acosta5, C. Borcea8, M.Ciemala9, P. Delahaye1, A. Estrade2, G. de France1, J. Grinyer1, B.Jacquot1, O. Kamalou1, A. Laird10, V. Margerin2, G.Marquinez-Duran5, F. Negoita8, M. Rejmund1, C. Rodriguez-Tajes1,F. Rotaru8, C. Schmitt1, N. de Séréville11, O. Sorlin1, M. Stanoiu8,J.C. Thomas1, P.J. Woods21GANIL Caen, 2University of Edinburgh, 3 INS Vinca Belgrade, 4Nuclear Physics Institute ofRez, 5University of Huelva, 6Universidade de Santiago de Compostela, 7LPC Caen, 8IFIN-HHBucharest, 9Institute of Nuclear Physics Krakòw, 10University of York, 11IPN OrsayE-mail: florent.boulay@ganil.frAbstract.The accuracy of the predictions of the γ flux produced by a classical nova during the firsthours after the outburst is limited by the uncertainties on several reaction rates, including the18F(p,α)15O one. Better constraints on this reaction rate can be obtained by determining thespectroscopic properties of the compound nucleus 19Ne. This was achieved in a new inelasticscattering method using a 19Ne radioactive beam (produced by the GANIL-SPIRAL 1 facility)impinging onto a proton target. The experiment was performed at the VAMOS spectrometer. Inthis article the performances (excitation energy range covered and excitation energy resolution)and limitations of the new technique are discussed. Excitation energy resolution of σ=33keV and low background were obtained with this inverse kinematics method, which will allowextracting the spectroscopic properties of 19Ne.1. IntroductionThe classical description of a nova consists of an explosion that occurs in a binary system ofstars. Typically, the outer layer of a main sequence star is accreted by gravitational attractiononto the surface of a companion white dwarf star (WD), where nuclear reactions are occurring.The surface temperature increases and can reach several hundreds of millions degrees dependingon the mass and the type (either ONe or CO) of the WD. At these critical temperatures, theelectronic degeneracy of the WD surface matter that prevents the expansion of the gas is liftedgiving rise to the explosion and expulsion of matter into the interstellar medium.Some of the nuclei produced via proton capture reactions are radioactive. The detectionof their characteristic γ-lines, by a satellite such as INTEGRAL, would allow to constrain thescenario of the explosion, with the proviso of knowing very well the reaction rates. According tomodels [1], the 18F nucleus 511 keV decay transition should dominate the low-energy γ spectrum(≤ 2 MeV) during the first hours after the outburst. 18F has a reasonable half-life (110 min)21234567890 ‘’“”Nuclear Physics in Astrophysics Conference (NPA VII) IOP PublishingIOP Conf. Series: Journal of Physics: Conf. Series 940 (2018) 012003  doi :10.1088/1742-6596/940/1/012003and is predicted to be sufficiently produced to be a good candidate for observation. To date,the evaluation of the 18F(p,α)15O reaction rate at the relevant astrophysics energy range, calledGamow window (GW) is mainly based on the spectroscopic properties of the compound nucleus19Ne (18F+p). The lack of direct measurements within the GW is explained by the low beamintensities of 18F available at the current radioactive ions beam facilities and the low cross section.The existing uncertainties on the 18F(p,α)15O reaction rate covers several orders of magnitudeat typical novae temperatures [2]. To better constrain this reaction rate, a new investigation ofthe 19Ne spectroscopic properties was performed at GANIL using a novel experimental setup.2. Method and experimental setupThe inelastic scattering reaction 19Ne(p,p’)19Ne∗ was used to populate the 19Ne states of interest,located around the proton threshold Sp=6.41 MeV (Sα=3.528 MeV). The advantage of such areaction mechanism is the statistical and non-selective feeding of all states. States that are notaccessible via selective reactions like transfer reactions were indeed seen in this experiment. Thekinematics of the protons p’ allowed to reconstruct the excitation energy spectrum of 19Ne∗ andto study the states of interest. These states, located in the GW region, can decay followingthree different channels. The γ decay channel has a very low probability. Thus no dedicateddetector was used to measure them. The two main decay channels correspond to chargedparticle emissions (19Ne → 18F + p” or 19Ne → 15O + α). The angular distribution of theemitted charged particles (α or p”) can be used to reconstruct the spin of the 19Ne states in amodel independent way. The coincidence between the proton p’ and the emitted particles canbe used to extract the individual branching ratios.Figure 1. General layout of theexperimental setup. The differentdetectors used in the experimentare indicated.The 19Ne radioactive beam was produced at the GANIL-SPIRAL 1 facility. It was acceleratedto 10 MeV/u by the CIME cyclotron and sent onto a 1 µm thin polyethylene target (CH2)n. Thebeam intensity was up to 1×108 pps with a purity of 100 %. During the experiment, severalbeam cuts were applied in the accelerator section to improve as much as possible the beamposition and its energy resolution. In those conditions the average incident 19Ne flux on targetwas of 2×107 pps. In inverse kinematics, the proton p’ has to be detected at zero degree to getthe best energy resolution. The large acceptance VAMOS spectrometer [3] was used to rejectthe incident beam ions and to ensure the p’ energy measurement of the protons with an energyresolution up to 1500(see Fig. 1). VAMOS was used for the first time to detect protons. The αparticles and protons p” were identified and characterized with a silicon ∆E-E telescope calledCD-PAD [4] located at 10 cm downstream the target.31234567890 ‘’“”Nuclear Physics in Astrophysics Conference (NPA VII) IOP PublishingIOP Conf. Series: Journal of Physics: Conf. Series 940 (2018) 012003  doi :10.1088/1742-6596/940/1/0120033. Analysis and preliminary results3.1. Excitation energyThe large magnetic rigidity acceptance of VAMOS allowed measuring coincidences of p’ scatteredparticles with α and p” decay particles in a wide excitation energy range from 4.5 to 8.5 MeV(see Fig. 2) and from 7 to 8.5 MeV respectively. With this setup resolutions of 44 keV at 4.5MeV to 33 keV at 8.1 MeV were achieved. The amplitude of the excitation energy spectrumwas normalized to the beam time and corrected relative to the contribution of the carbon in thetarget. To perform this correction, measurements with a 0.4 µm thick carbon target (during 15% of the experiment) were realized (see Fig. 2) and pointed out a background level compatiblewith zero (observed counts in the spectrum are compatible with an hydrogen contaminationusually present in thin carbon targets).Excitation energy (MeV)4.5 5 5.5 6 6.5 7 7.5 8Amplitude (a.u.) (14 keV/bin)24681012 Figure 2. Excitation energy spectrumof 19Ne reconstructed by the VAMOSspectrometer with protons p’ detected at0o in coincidence with alpha particlesrecorded with the CD-PAD ∆E-E telescopelocated behind the target (open squares).States are populated through the inelasticreaction mechanism 19Ne(p,p’)19Ne∗. Incircles, the spectrum obtained when the(CH2)n target was substituted with a thincarbon target.3.2. Drawback of the methodA source of contamination was observed in the data, it is related to 15O and 18F coming from thedecay of 19Ne∗. They are kinematicaly forward focused in the laboratory frame with a magneticrigidity difference of about 20 % with respect to the dipole nominal value set for the experiment.The large acceptance of VAMOS allows thus a simultaneous detection of some of these particleswith the proton p’. The heavy ions have a much higher energy deposit in the VAMOS driftchambers. Therefore, they produced saturation of the signals collected on the strips of the driftchambers leading to the destruction of the proton p’ signal of interest.Excitation energy (MeV)4.5 5 5.5 6 6.5 7 7.5 8Absolute efficiency00.10.20.30.40.50.60.70.8O15Without O15With Figure 3. Absolute efficiency as a functionof the excitation energy deduced froma simulation in the case the proton p’is detected by VAMOS in coincidencewith decaying α particles recorded inthe CD-PAD (black curve). The curvein red illustrates the loss of statisticsand efficiency due to the heavy ionssaturation effect on the drift chamber.Both simulations error bars include theuncertainty on the angular momentumdistributions.In order to correct these losses induced by heavy ions, a simulation that includes the fullkinematics, the geometry of the CD-PAD, the angular and the magnetic rigidity acceptances41234567890 ‘’“”Nuclear Physics in Astrophysics Conference (NPA VII) IOP PublishingIOP Conf. Series: Journal of Physics: Conf. Series 940 (2018) 012003  doi :10.1088/1742-6596/940/1/012003of the VAMOS spectrometer was developped and used. Figure 3 shows the absolute detectionefficiency simulated as a function of the excitation energy reconstructed via the p’ scatteredparticles measured in VAMOS in coincidence with an α decay particle detected in the CD-PAD.Same work has been completed in the case of coincidences of p’ with p” decay particles.3.3. Benchmarking of the new techniqueTable 1 provides a comparison between the properties (excitation energy, proton to alpha widthratio, total width) extracted in this experiment and the ones from the literature [5] for the wellknown 32+state located at Ex=7.074 MeV. There is a good agreement between these values. Theuncertainties in excitation energy given in the literature are better than ours as determined froma compilation of several experiments. Our resolution is however the best achieved up to nowfor this type of experiment in inverse kinematics. The current limitation in energy resolutionis mainly due to the target thickness. The resolution for the partial widths is degraded in thisexperiment because of the efficiency correction that has to be applied due to the heavy ionscontamination. The spin of this state has not been assigned yet because additionnal correctionshas to be applied (a precise knowledge of the beam position is needed for instance).Properties This experiment Literature [5]Excitation energy 7.076(3) MeV 7.074(2) MeVΓtot 35(4) keV 39(2) keVΓpΓα0.64(5) 0.638(5)Table 1. Summary of the 7.074MeV state properties measured in thisexperiment and from the literature [5].4. ConclusionsThanks to the performances of the VAMOS spectrometer, we realized a new spectroscopic studyof 19Ne with a high energy resolution (σ = 44 to 33 keV) for an inverse kinematics measurement.The heavy ions coming from the decay of 19Ne∗, 15O and 18F, induced statistics losses. Acorrection function was defined through a simulation of this experiment and applied to the data.It allowed us to extract relevant spectroscopic properties such as the total width, as well as theproton and the α partial widths ratio. A comparison of the results obtained from this workfor the well-known state at 7.074 MeV with the values given in the literature has been madeand pointed out the power and accuracy of our method. New spectroscopic properties will beextracted for all the states located around the GW. For future experiments, a thin layer ofaluminium could be used after the VAMOS dipole in order to stop the heavy ions. Its thicknessshould not impact too much the protons energy and angular resolution.4.1. AcknowledgementsThis work has been supported by the European Community FP7 - Capacities - IntegratedInfrastructure Initiative - contract ENSAR no 262010. This work was also supported by theFrance-Romanian IN2P3-IFIN-HH collaboration no 03-33, by the France-Czech LEA NuAGcollaboration and the NAVI collaboration. The authors would also like to thank the technicalteams of GANIL for their strong implications in this experiment.References[1] Jordi José and Margarita Hernanz. Journal of Physics G : Nuclear and Particle Physics, 34(12) :R431, (2007)[2] C. Iliadis, R. Longland, A.E. Champagne, A. Coc, R. Fitzgerald, Nuclear Physics A, 841, 1, 31-250, (2010)[3] M. Rejmund, B. Lecornu, A. Navin, et al. Nucl. Instrum. Methods A, 646(1) :184-191, (2011)[4] A.N Ostrowski, S. Cherubini, T. Davinson, et al. Nucl. Instrum. Methods A, 480(23) :448-455, (2002)[5] D. W. Bardayan, J. C. Blackmon, W. Bradfield-Smith, et al. Phys. Rev. C, 63 :065802, (2001)

Measurement of 19Ne spectroscopic properties via a new method of inelastic scattering to study novae

The accuracy of the predictions of the γ flux produced by a classical nova during the first hours after the outburst is limited by the uncertainties on several reaction rates, including the 18F(p,α)15O one. Better constraints on this reaction rate can be obtained by determining the spectroscopic properties of the compound nucleus 19Ne. This was achieved in a new inelastic scattering method using a 19Ne radioactive beam (produced by the GANIL-SPIRAL 1 facility) impinging onto a proton target. The experiment was performed at the VAMOS spectrometer. In this article the performances (excitation energy range covered and excitation energy resolution) and limitations of the new technique are discussed. Excitation energy resolution of σ = 33 keV and low background were obtained with this inverse kinematics method, which will allow extracting the spectroscopic properties of 19Ne.</p

de Oliveira Santos, Francois

Ramos, Daniel

Acosta, Jorge L.

Schmitt, Christian

Edinburgh Research Explorer

     Edinburgh Research Explorer                                      Measurement of 19Ne spectroscopic properties via a newmethod of inelastic scattering to study novaeCitation for published version:Boulay, F, Bastin, B, de Oliveira Santos, F, Davinson, T, Lemasson, A, Ujic, P, Mrazek, J, Sánchez-Benítez,AM, Traykov, E, Ramos, D, Achouri, L, Acosta, JL, Borcea, C, Ciemala, M, Delahaye, P, Estrade, A, DeFrance, G, Grinyer, J, Jacquot, B, Kamalou, O, Laird, A, Margerin, V, Marquinez-Duran, G, Negoita, F,Rejmund, M, Rodriguez-Tajes, C, Rotaru, F, Schmitt, C, De Séréville, N, Sorlin, O, Stanoiu, M, Thomas, JC& Woods, PJ 2018, 'Measurement of 19Ne spectroscopic properties via a new method of inelastic scatteringto study novae' Paper presented at Nuclear Physics in Astrophysics VII, York, United Kingdom, 18/05/15 -22/05/15, . DOI: 10.1088/1742-6596/940/1/012003Digital Object Identifier (DOI):10.1088/1742-6596/940/1/012003Link:Link to publication record in Edinburgh Research ExplorerDocument Version:Publisher's PDF, also known as Version of recordGeneral rightsCopyright for the publications made accessible via the Edinburgh Research Explorer is retained by the author(s)and / or other copyright owners and it is a condition of accessing these publications that users recognise andabide by the legal requirements associated with these rights.Take down policyThe University of Edinburgh has made every reasonable effort to ensure that Edinburgh Research Explorercontent complies with UK legislation. If you believe that the public display of this file breaches copyright pleasecontact openaccess@ed.ac.uk providing details, and we will remove access to the work immediately andinvestigate your claim.Download date: 08. Jul. 2019Journal of Physics: Conference SeriesPAPER • OPEN ACCESSMeasurement of 19Ne spectroscopic properties via a new method ofinelastic scattering to study novaeTo cite this article: F. Boulay et al 2018 J. Phys.: Conf. Ser. 940 012003 View the article online for updates and enhancements.This content was downloaded from IP address 85.17.24.66 on 18/06/2019 at 12:021Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distributionof this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.Published under licence by IOP Publishing Ltd1234567890 ‘’“”Nuclear Physics in Astrophysics Conference (NPA VII) IOP PublishingIOP Conf. Series: Journal of Physics: Conf. Series 940 (2018) 012003  doi :10.1088/1742-6596/940/1/012003Measurement of 19Ne spectroscopic properties via anew method of inelastic scattering to study novae.F. Boulay1, B. Bastin1, F. de Oliveira Santos1, T. Davinson2, A.Lemasson1, P. Ujic3, J. Mrazek4, A. M. Sa´nchez-Ben´ıtez5,1, E.Traykov1, D. Ramos6, L. Achouri7, L. Acosta5, C. Borcea8, M.Ciemala9, P. Delahaye1, A. Estrade2, G. de France1, J. Grinyer1, B.Jacquot1, O. Kamalou1, A. Laird10, V. Margerin2, G.Marquinez-Duran5, F. Negoita8, M. Rejmund1, C. Rodriguez-Tajes1,F. Rotaru8, C. Schmitt1, N. de Se´re´ville11, O. Sorlin1, M. Stanoiu8,J.C. Thomas1, P.J. Woods21GANIL Caen, 2University of Edinburgh, 3 INS Vinca Belgrade, 4Nuclear Physics Institute ofRez, 5University of Huelva, 6Universidade de Santiago de Compostela, 7LPC Caen, 8IFIN-HHBucharest, 9Institute of Nuclear Physics Krako`w, 10University of York, 11IPN OrsayE-mail: florent.boulay@ganil.frAbstract.The accuracy of the predictions of the γ ﬂux produced by a classical nova during the ﬁrsthours after the outburst is limited by the uncertainties on several reaction rates, including the18F(p,α)15O one. Better constraints on this reaction rate can be obtained by determining thespectroscopic properties of the compound nucleus 19Ne. This was achieved in a new inelasticscattering method using a 19Ne radioactive beam (produced by the GANIL-SPIRAL 1 facility)impinging onto a proton target. The experiment was performed at the VAMOS spectrometer. Inthis article the performances (excitation energy range covered and excitation energy resolution)and limitations of the new technique are discussed. Excitation energy resolution of σ=33keV and low background were obtained with this inverse kinematics method, which will allowextracting the spectroscopic properties of 19Ne.1. IntroductionThe classical description of a nova consists of an explosion that occurs in a binary system ofstars. Typically, the outer layer of a main sequence star is accreted by gravitational attractiononto the surface of a companion white dwarf star (WD), where nuclear reactions are occurring.The surface temperature increases and can reach several hundreds of millions degrees dependingon the mass and the type (either ONe or CO) of the WD. At these critical temperatures, theelectronic degeneracy of the WD surface matter that prevents the expansion of the gas is liftedgiving rise to the explosion and expulsion of matter into the interstellar medium.Some of the nuclei produced via proton capture reactions are radioactive. The detectionof their characteristic γ-lines, by a satellite such as INTEGRAL, would allow to constrain thescenario of the explosion, with the proviso of knowing very well the reaction rates. According tomodels [1], the 18F nucleus 511 keV decay transition should dominate the low-energy γ spectrum(≤ 2 MeV) during the ﬁrst hours after the outburst. 18F has a reasonable half-life (110 min)21234567890 ‘’“”Nuclear Physics in Astrophysics Conference (NPA VII) IOP PublishingIOP Conf. Series: Journal of Physics: Conf. Series 940 (2018) 012003  doi :10.1088/1742-6596/940/1/012003and is predicted to be suﬃciently produced to be a good candidate for observation. To date,the evaluation of the 18F(p,α)15O reaction rate at the relevant astrophysics energy range, calledGamow window (GW) is mainly based on the spectroscopic properties of the compound nucleus19Ne (18F+p). The lack of direct measurements within the GW is explained by the low beamintensities of 18F available at the current radioactive ions beam facilities and the low cross section.The existing uncertainties on the 18F(p,α)15O reaction rate covers several orders of magnitudeat typical novae temperatures [2]. To better constrain this reaction rate, a new investigation ofthe 19Ne spectroscopic properties was performed at GANIL using a novel experimental setup.2. Method and experimental setupThe inelastic scattering reaction 19Ne(p,p’)19Ne∗ was used to populate the 19Ne states of interest,located around the proton threshold Sp=6.41 MeV (Sα=3.528 MeV). The advantage of such areaction mechanism is the statistical and non-selective feeding of all states. States that are notaccessible via selective reactions like transfer reactions were indeed seen in this experiment. Thekinematics of the protons p’ allowed to reconstruct the excitation energy spectrum of 19Ne∗ andto study the states of interest. These states, located in the GW region, can decay followingthree diﬀerent channels. The γ decay channel has a very low probability. Thus no dedicateddetector was used to measure them. The two main decay channels correspond to chargedparticle emissions (19Ne → 18F + p” or 19Ne → 15O + α). The angular distribution of theemitted charged particles (α or p”) can be used to reconstruct the spin of the 19Ne states in amodel independent way. The coincidence between the proton p’ and the emitted particles canbe used to extract the individual branching ratios.Figure 1. General layout of theexperimental setup. The diﬀerentdetectors used in the experimentare indicated.The 19Ne radioactive beam was produced at the GANIL-SPIRAL 1 facility. It was acceleratedto 10 MeV/u by the CIME cyclotron and sent onto a 1 μm thin polyethylene target (CH2)n. Thebeam intensity was up to 1×108 pps with a purity of 100 %. During the experiment, severalbeam cuts were applied in the accelerator section to improve as much as possible the beamposition and its energy resolution. In those conditions the average incident 19Ne ﬂux on targetwas of 2×107 pps. In inverse kinematics, the proton p’ has to be detected at zero degree to getthe best energy resolution. The large acceptance VAMOS spectrometer [3] was used to rejectthe incident beam ions and to ensure the p’ energy measurement of the protons with an energyresolution up to 1500(see Fig. 1). VAMOS was used for the ﬁrst time to detect protons. The αparticles and protons p” were identiﬁed and characterized with a silicon ΔE-E telescope calledCD-PAD [4] located at 10 cm downstream the target.31234567890 ‘’“”Nuclear Physics in Astrophysics Conference (NPA VII) IOP PublishingIOP Conf. Series: Journal of Physics: Conf. Series 940 (2018) 012003  doi :10.1088/1742-6596/940/1/0120033. Analysis and preliminary results3.1. Excitation energyThe large magnetic rigidity acceptance of VAMOS allowed measuring coincidences of p’ scatteredparticles with α and p” decay particles in a wide excitation energy range from 4.5 to 8.5 MeV(see Fig. 2) and from 7 to 8.5 MeV respectively. With this setup resolutions of 44 keV at 4.5MeV to 33 keV at 8.1 MeV were achieved. The amplitude of the excitation energy spectrumwas normalized to the beam time and corrected relative to the contribution of the carbon in thetarget. To perform this correction, measurements with a 0.4 μm thick carbon target (during 15% of the experiment) were realized (see Fig. 2) and pointed out a background level compatiblewith zero (observed counts in the spectrum are compatible with an hydrogen contaminationusually present in thin carbon targets).Excitation energy (MeV)4.5 5 5.5 6 6.5 7 7.5 8Amplitude (a.u.) (14 keV/bin)24681012 Figure 2. Excitation energy spectrumof 19Ne reconstructed by the VAMOSspectrometer with protons p’ detected at0o in coincidence with alpha particlesrecorded with the CD-PAD ΔE-E telescopelocated behind the target (open squares).States are populated through the inelasticreaction mechanism 19Ne(p,p’)19Ne∗. Incircles, the spectrum obtained when the(CH2)n target was substituted with a thincarbon target.3.2. Drawback of the methodA source of contamination was observed in the data, it is related to 15O and 18F coming from thedecay of 19Ne∗. They are kinematicaly forward focused in the laboratory frame with a magneticrigidity diﬀerence of about 20 % with respect to the dipole nominal value set for the experiment.The large acceptance of VAMOS allows thus a simultaneous detection of some of these particleswith the proton p’. The heavy ions have a much higher energy deposit in the VAMOS driftchambers. Therefore, they produced saturation of the signals collected on the strips of the driftchambers leading to the destruction of the proton p’ signal of interest.Excitation energy (MeV)4.5 5 5.5 6 6.5 7 7.5 8Absolute efficiency00.10.20.30.40.50.60.70.8O15Without O15With Figure 3. Absolute eﬃciency as a functionof the excitation energy deduced froma simulation in the case the proton p’is detected by VAMOS in coincidencewith decaying α particles recorded inthe CD-PAD (black curve). The curvein red illustrates the loss of statisticsand eﬃciency due to the heavy ionssaturation eﬀect on the drift chamber.Both simulations error bars include theuncertainty on the angular momentumdistributions.In order to correct these losses induced by heavy ions, a simulation that includes the fullkinematics, the geometry of the CD-PAD, the angular and the magnetic rigidity acceptances41234567890 ‘’“”Nuclear Physics in Astrophysics Conference (NPA VII) IOP PublishingIOP Conf. Series: Journal of Physics: Conf. Series 940 (2018) 012003  doi :10.1088/1742-6596/940/1/012003of the VAMOS spectrometer was developped and used. Figure 3 shows the absolute detectioneﬃciency simulated as a function of the excitation energy reconstructed via the p’ scatteredparticles measured in VAMOS in coincidence with an α decay particle detected in the CD-PAD.Same work has been completed in the case of coincidences of p’ with p” decay particles.3.3. Benchmarking of the new techniqueTable 1 provides a comparison between the properties (excitation energy, proton to alpha widthratio, total width) extracted in this experiment and the ones from the literature [5] for the wellknown 32+state located at Ex=7.074 MeV. There is a good agreement between these values. Theuncertainties in excitation energy given in the literature are better than ours as determined froma compilation of several experiments. Our resolution is however the best achieved up to nowfor this type of experiment in inverse kinematics. The current limitation in energy resolutionis mainly due to the target thickness. The resolution for the partial widths is degraded in thisexperiment because of the eﬃciency correction that has to be applied due to the heavy ionscontamination. The spin of this state has not been assigned yet because additionnal correctionshas to be applied (a precise knowledge of the beam position is needed for instance).Properties This experiment Literature [5]Excitation energy 7.076(3) MeV 7.074(2) MeVΓtot 35(4) keV 39(2) keVΓpΓα0.64(5) 0.638(5)Table 1. Summary of the 7.074MeV state properties measured in thisexperiment and from the literature [5].4. ConclusionsThanks to the performances of the VAMOS spectrometer, we realized a new spectroscopic studyof 19Ne with a high energy resolution (σ = 44 to 33 keV) for an inverse kinematics measurement.The heavy ions coming from the decay of 19Ne∗, 15O and 18F, induced statistics losses. Acorrection function was deﬁned through a simulation of this experiment and applied to the data.It allowed us to extract relevant spectroscopic properties such as the total width, as well as theproton and the α partial widths ratio. A comparison of the results obtained from this workfor the well-known state at 7.074 MeV with the values given in the literature has been madeand pointed out the power and accuracy of our method. New spectroscopic properties will beextracted for all the states located around the GW. For future experiments, a thin layer ofaluminium could be used after the VAMOS dipole in order to stop the heavy ions. Its thicknessshould not impact too much the protons energy and angular resolution.4.1. AcknowledgementsThis work has been supported by the European Community FP7 - Capacities - IntegratedInfrastructure Initiative - contract ENSAR no 262010. This work was also supported by theFrance-Romanian IN2P3-IFIN-HH collaboration no 03-33, by the France-Czech LEA NuAGcollaboration and the NAVI collaboration. The authors would also like to thank the technicalteams of GANIL for their strong implications in this experiment.References[1] Jordi Jose´ and Margarita Hernanz. Journal of Physics G : Nuclear and Particle Physics, 34(12) :R431, (2007)[2] C. Iliadis, R. Longland, A.E. Champagne, A. Coc, R. Fitzgerald, Nuclear Physics A, 841, 1, 31-250, (2010)[3] M. Rejmund, B. Lecornu, A. Navin, et al. Nucl. Instrum. Methods A, 646(1) :184-191, (2011)[4] A.N Ostrowski, S. Cherubini, T. Davinson, et al. Nucl. Instrum. Methods A, 480(23) :448-455, (2002)[5] D. W. Bardayan, J. C. Blackmon, W. Bradﬁeld-Smith, et al. Phys. Rev. C, 63 :065802, (2001)

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