2nd HIE-ISOLDE Physics Workshop 2026, Göteborg, Sweden

19 Aug 2026, 08:25 → 21 Aug 2026, 17:00 Europe/Zurich

Alliansen 1 (Ullevi Restaurang & Konferens)

Annie Dolan, Carlotta Porzio (CERN), Liam Gaffney (University of Liverpool (GB)), Luis M Fraile (CERN), Olof Tengblad (Consejo Superior de Investigaciones Cientificas (CSIC) (ES)), Thorsten Kroell (Technische Universitaet Darmstadt (DE))

The 2nd HIE-ISOLDE Physics Workshop will be held at Ullevi Restaurang & Konferens in Göteborg, Sweden, 19-21 August 2026.

The workshop is jointly organised by the 3 primary HIE-ISOLDE Collaborations, namely: Miniball, the ISOLDE Solenoidal Spectrometer (ISS) and the Scattering Experiments Chamber (SEC).  It will be an opportunity for the individual collaborations to meet, discuss recent results and future plans with a broader outlook on physics opportunities at the facility, with a particular focus on identifying new collaborative endeavours.

The workshop will feature invited talks concerning the HIE-ISOLDE facility and other facilities worldwide.

We strongly encourage contributions from early-career researchers actively analysing data from HIE-ISOLDE.

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Weather information:

• Experimentalist style: Radar and lightning (SMHI)
• Theory style: Weather forecast (SMHI)

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Fees (all including VAT) (on separate page):

• Registration:
  • Seniors: 2375 SEK before June 24th; 2800 SEK after June 24th.
  • Young researchers: 875 SEK before June 24th; 1000 SEK after June 24th.
    (Before PhD degree or post-doctoral researcher)
• Dinner: 1000 SEK per person.

 

Registration deadline: 5. Aug 2026.

Beware of unsolicited offers to 'help' with booking after registering - spammers are known to scan Indico for names and associate with addresses from other sources.
There are no travel agency arrangements. For reduced-rate hotels, see the accommodation page.

 

Link to CERNBOX with photo collection from river cruise: https://cernbox.cern.ch/files/spaces/eos/user/e/ejensen/hie-isolde-workshop-2026

Wednesday 19 August

09:00 → 09:25 Registration

09:25 → 09:30 Welcome

welcome_hie_isolde_2026.pdf

09:30 → 10:00 Light nuclei and reactions, dripline and beyond

09:30 Reaction dynamics and nuclear structure of light exotic nuclei

The presentation explores reaction experiments using low-energy post-accelerated radioactive beams to
examine the influence of halo structures and neutron and proton excess on reaction dynamics and nuclear structure. Results of reactions induced
by neutron-halo and proton-halo nuclei performed at ISOLDE are compared, highlighting differences in the reaction dynamics that
stem from variations in nuclear structure. Additionally, the study addresses neutron-rich nuclei, focusing on the presence clustering and of resonances which can be attributed to the extended surface
layer characteristic of these nuclei. Perspectives for ISOLDE will be discussed.

Speaker: Alessia Francesca Di Pietro (Universita e INFN, Catania (IT))

dipietro_Isolde2026.pdf

dipietro_Isolde2026.pptx

10:00 → 10:30 Fika (break)

10:30 → 10:50 Shell closures and shell evolution

10:30 Does the Seniority Scheme Hold in the N=126 Isotone ²¹⁴Ra?

The nuclear shell model, combined with pairing correlations, offers a straightforward explanation of the low-energy spectra of semi-magic nuclei. In a single high-$j$ orbital with more than two particles, low-lying $J>0$ states arise from recoupling of unpaired nucleons and group into multiplets labeled by seniority $\nu$ -- the number of unpaired particles. The generalized seniority scheme is essentially a truncated shell-model description.

To study how well the seniority picture holds near the $N=126$ shell closure, we carried out a safe Coulomb-excitation experiment on $^{214}$Ra. A post-accelerated $^{214}$Ra beam was directed onto $^{120}$Sn and $^{58}$Ni targets at HIE-ISOLDE, and the resulting $\gamma$ rays were measured with the Miniball spectrometer. The main goal is to extract electromagnetic transition strengths, in particular the $B(E2;2_1^+ \rightarrow 0_1^+)$ value, and compare them with shell-model expectations and trends in neighboring $N=126$ isotones.

The analysis includes particle-$\gamma$ coincidence selection, Doppler correction, extraction of $\gamma$-ray yields, and treatment of feeding contributions. Preliminary results, including observed low-lying states in $^{214}$Ra and their relevance for the seniority scheme near the $N=126$ shell closure, will be presented.

Speaker: Ivan Todorov Anastasov (University of Sofia - St. Kliment Ohridski (BG))

IvanAnastasov_pres.pdf

10:50 → 11:10 Techniques

10:50 Commissioning experiment with the recoil distance Doppler-shift technique at HIE-ISOLDE

The recoil distance Doppler-shift (RDDS) technique is a well-established method for the determination of excited-state lifetimes and electromagnetic transition strengths. The implementation at the MINIBALL plunger extends this capability to post-accelerated radioactive ion beams at HIE-ISOLDE and establishes a new experimental program for lifetime measurements.

The commissioning experiment IS656 employed the incomplete-fusion reaction $^{7}$Li($^{144}$Cs,$^{144}$Ba)$^{4}$He to populate excited states in $^{144}$Ba. Prompt $\gamma$ rays were detected with the MINIBALL spectrometer, while reaction products were identified using a downstream DSSSD detector. The experiment represents the first application of the RDDS technique at HIE-ISOLDE and serves as the starting point for a series of lifetime measurements with radioactive beams.

We present the current status of the data analysis, including particle identification, Doppler correction for different recoil velocities and the separation of shifted and unshifted components for several target--degrader distances. The performance of the experimental setup and the analysis procedure are discussed together with the prospects for extracting excited-state lifetimes. The experience gained from this commissioning experiment provides the basis for future RDDS measurements at HIE-ISOLDE.
Funded by the German BMFTR, Joint Project 05P2024--ISOLDE, Grant No.~05P24PK2.

Speaker: Alina Didik (Universitaet zu Koeln (DE))

isolde_workshop_didik.pdf

11:10 → 11:20 Short break

11:20 → 11:40 Shapes and collectivity

11:20 Probing shape coexistence in the neutron-deficient mercury isotopes with Coulomb-excitation

Shape coexistence in the neutron-deficient lead region around $N \approx 104$ has been discovered in different nuclei especially in the mercury isotopes, where a staggering effect was found between even- and odd-mass nuclei using charge radii measurement [1,2]. In addition the study of the even-even $^{182-188}$Hg isotopes via various reactions showed a mixing of weakly deformed oblate and more deformed prolate configurations which coexists at low excitation energies with the maximum for the mixed $2^+$ states around the mid-shell in $^{182,184}$Hg [3,4,5]. To investigate the shape coexistence in this region in more detail, Coulomb-excitation experiments has been performed in $^{182,184,185}$Hg at HIE-ISOLDE. The use of RILIS offers a unique opportunity to separate the individual isotopes and in particular the complete separation of the ground state and the different deformed isomeric state in $^{185}$Hg. The $^{182,184,185\mathrm{g,m}}$Hg beams were accelerated onto $^{120}$Sn targets and in the case of the $^{185}$Hg isotope additionally onto a $^{48}$Ti target with an energy of 4 MeV/u. The emitted $\gamma$ rays were detected utilising the Miniball array in coincidence to the scattered particles measured in the DSSSD detector. The SPEDE detector is combined with the array to investigate the transition between states of the same spin and parity as $0_1^+ \rightarrow 0_{g.s.}^+$ or $2_2^+ \rightarrow 2_1^+$ in the even-even $^{182,184}$Hg isotopes. Preliminary results of excited states in $^{182,184,185}$Hg will be shown. Excited states in $^{182,184}$Hg were populated and identified up to a spin of $8_1^+$. The second excited states are observed up to a spin of $4_2^+$ and $6_2^+$, respectively, and the intensity of the transitions between the bands show the strong mixing of these states. Preliminary particle gated electron spectra and particle-electron gated $\gamma$-ray coincidences will be presented.

[1] J. Bonn et al., Zeitschrift für Physik A Hadrons and Nuclei 276(3), 203 (1976)
[2] B. Marsh et al., Nature Physics 14, 1163 (2018)
[3] L. P. Gaffney et al., Physical Review C 89, 024307 (2014)
[4] N. Bree et al., Physical Review Letters 112, 162701 (2014)
[5] K. Wrzosek-Lipska et al., The European Physical Journal A 55, 130 (2019)

Speaker: Hannah Kleis (University of Liverpool (GB))

Probing_shape_coexistence_mercury_HK_HIE_ISOLDE.pdf

11:40 → 12:10 During Long Shutdown 3

11:40 HIE-ISOLDE aspects: LS3 - The ISOLDE Improvement Program

Long Shutdown 3 for ISOLDE started already right at the end of the physics run in December 2025 to accommodate the 24 months of work needed for the ISOLDE Beam Dump Replacement project. This period was chosen strategically to have the full ISOLDE facility ready with the restart of the CERN injector chain and the return of protons from the PS Booster to ISOLDE in 2028.

The 2 years of ISOLDE Shutdown is not only used for the Beam Dump Replacement. An impressive ISOLDE Improvement Program is being rolled out during LS3 of which many activities concern the REX and HIE-ISOLDE post-accelerator.

From the consolidation of the REX RF amplifiers to the refurbishment of HIE-ISOLDE Cryomodule 1, this presentation is to cover the aspects related to the ISOLDE post-accelerator improvements and modifications during LS3 and its restart in 2028.

Speaker: Erwin Siesling (CERN)

HIE ISOLDE aspects LS3 ISOLDE Improvement Program _ 2nd HIE ISOLDE workshop Gothenburg Sweden 19_08_26 ES.pptx

12:10 → 13:40 Lunch

13:40 → 14:10 Techniques

13:40 ISS status and updates on 94Kr(d,p) analysis

The ISOLDE Solenoidal Spectrometer (ISS) is used to study transfer reactions in inverse kinematics with the high-energy beams delivered by the HIE-ISOLDE linac. ISS has completed five successful physics campaigns since it was fully commisssioned in 2021. This talk will provide an overview of the experiments performed, developments made since the 2023 HIE-ISOLDE workshop, and future plans for ISS following the long shutdown.

The neutron-rich Kr isotopes exhibit a much more gradual onset of deformation around $N~=~60$ than the neighbouring Sr and Zr isotopes, making them an important testing ground for understanding the underlying shell evolution in the neutron-rich $A~=~100$ region. The $^{92}$Kr$(d,p)$ transfer reaction performed with ISS in 2022 determined the spectroscopic facotr of the $\nu g_{7/2}$ orbital believed to play a key role in driving this deformation. Preliminary analysis of the complementary $^{94}$Kr$(d,p)$ reaction performed in 2025 and the $^{129}$Xe$(d,p)$ reaction will also be presented.

Speaker: Annie Dolan

adolan_hie-isolde_2026.pdf

14:10 → 14:30 Shell closures and shell evolution

14:10 Investigation of coupled states near 208Pb with the Miniball plunger (experiment IS774)

We investigate $^{207}$Tl, the one-proton-hole neighbor of doubly magic $^{208}$Pb — one of the most thoroughly studied doubly magic nuclei, whose first excited state is a well-established octupole phonon vibration. A deep-inelastic experiment has confirmed the existence of a 17/2$^+$ state in $^{207}$Tl [1], previously proposed theoretically to be a particle-octupole vibration coupling (POVC) between the $^{208}$Pb core and a proton hole ($\pi h_{11/2}^{-1} \times 3^-$) [2].

Even though a 17/2$^+$ state has been identified, its lifetime — and hence its B(E3) value — has not been measured. A measurement of the equivalent high-spin state in $^{207}$Pb revealed not only a strong coupling to the single phonon, but also indicated a component of coupling to the proposed 6$^+$ double-phonon state in the $^{208}$Pb core. Measuring the lifetime of the 17/2$^+$ state in $^{207}$Tl will contribute to a better understanding of the interplay between single-particle and collective nuclear excitations in this region of the chart of nuclides.

A Miniball plunger experiment (IS774) was performed at HIE-ISOLDE in July 2025, enabling lifetime analysis of excited states in $^{206}$Tl and $^{207}$Tl. We used a re-accelerated $^{206}$Hg beam impinging on a $^{7}$Li target, inducing the transfer reaction $^{7}$Li($^{206}$Hg,αxn). A Au degrader was employed as the plunger, with a CD+PAD Si detector telescope and the Miniball HPGe array used for particle and gamma-ray detection, respectively.

At the HIE-ISOLDE meeting we will present a report on the ongoing gamma-ray spectroscopy analysis of IS774.

[1] Wilson, E., et al. "Core excitations across the neutron shell gap in 207Tl." Physics Letters B 747 (2015): 88-92.

[2] Rejmund, M., et al. "Particle octupole-vibration coupling near 208Pb." The European Physical Journal A 8.2 (2000): 161-164.

Speaker: Gulla Torvund (University of Oslo (NO))

HIE-ISOLDEworkshop2026_GT.pdf

HIE-ISOLDEworkshop2026_GT.pptx

14:30 → 14:50 Nuclear astrophysics

14:30 Constraining the $^{61}$Ga($p$,$\gamma$) stellar reaction rate via $^{61}$Zn($d$,$p$) transfer

Thermonuclear runaways on the surface of accreting neutron stars, known as Type-I X-ray bursts (XRBs), are powered by the rapid-proton ($rp$) process, a sequence of proton captures and $\beta^{+}$ decays involving nuclei extending toward the proton drip line. Since many of the nuclei involved are experimentally inaccessible, key reaction rates remain poorly constrained, introducing significant uncertainties into models of nucleosynthesis and energy generation in XRBs. In particular, nuclei with low proton-separation energies can establish ($p$,$\gamma$)$-$($\gamma$,$p$) equilibria, producing waiting points that influence both burst energetics and final isotopic abundances.

The astrophysically important $^{61}$Ga($p$,$\gamma$)$^{62}$Ge reaction is expected to influence reaction flow in the $A\approx60$ mass region, yet its rate remains experimentally unconstrained. Existing estimates rely on statistical-model calculations, whose validity is uncertain owing to the low level density near the proton threshold in $^{62}$Ge, $S_p = 2452(38)$ keV.

Here, we report the first experimental study of states relevant to the $^{61}$Ga($p$,$\gamma$)$^{62}$Ge reaction through the $^{61}$Zn($d$,$p$)$^{62}$Zn single-neutron transfer reaction performed at ISOLDE, CERN. Exploiting mirror symmetry between $^{62}$Zn and $^{62}$Ge, we identify key analogue states expected to dominate resonant proton capture under XRB conditions. These results provide the first experimental constraints on the $^{61}$Ga($p$,$\gamma$) reaction rate and its impact on energy generation in Type-I X-ray bursts.

Speaker: C. O'Shea (University of Surrey)

HIE-ISOLDE_WS_CO.pdf

14:50 → 15:10 Fika (break)

15:10 → 15:30 Results from other facilities

15:10 Beta-decay studies at FRIB

While radioactive ion beam facilities in Europe are currently undergoing maintenance and major upgrades, the newly commissioned Facility for Rare Isotope Beams (FRIB) in the U.S. has been providing radioactive beams for nuclear physics experiments for the past four years.

The Gas Stopping Area at FRIB enables thermalisation and momentum compression of in-flight radioactive beams, yielding pure, low-energy beams at high intensity, similar to the ISOL-quality beams extracted from the ISOLDE production targets, but with vastly different beam production constraints.

In this talk, I will present results from the first beta-delayed charged particle emission experiment conducted in the Stopped Beam Area at FRIB, where the mechanism of 2-proton emission from the β2p precursors ²²Al and ²⁶P was investigated.

Pure, low-energy beams of ²¹Mg, ²²Al, ²⁵Si and ²⁶P were implanted in a thin carbon foil surrounded by a compact array of silicon detector telescopes and high-purity germanium detectors. The unprecedented yields of the beams in combination with the employed setup allow for precision decay spectroscopy, revealing a plethora of new insights into this hitherto relatively unexplored region of the nuclear chart.

Speaker: Erik Jensen (Chalmers University of Technology (SE))

erik.pptx

15:30 → 15:50 Fission

15:30 Reaction Induced Fission of 230Ac and 230Th

To be added

Speaker: Tobias Beck (KU Leuven (BE))

15:50 → 16:00 Break

16:00 → 17:00 Closed meeting: Miniball Steering Committee

Thursday 20 August

09:00 → 09:40 New techniques and methods

09:00 Dead-layer measurements of the ISS silicon array

The performance of the silicon detectors used in the ISOLDE Solenoidal Spectrometer depends on an accurate calibration, which requires precise knowledge of these detector dead-layer thicknesses. A mixed alpha source was used to irradiate the ISS silicon array at different incidence angles. Source positions were determined by fitting the measured count distributions with a solid-angle model. By relating the uncalibrated ADC response to the particle entrance angle, detector gain, offset, and dead-layer thickness can be extracted simultaneously. This method has been applied across the full array, providing the first dead-layer measurement for all silicon detector wafers and improving the accuracy of future spectroscopy experiments at ISS.

Speaker: Josh Alex David Curry (University of Liverpool (GB))

Dead_Layer_Measurements_HIE-ISOLDE.pptx

09:20 Improving energy resolution of Miniball, introducing cross-talk corrections

In our recent Coulomb Excitation study of $^{144}$Ba at Miniball we performed a new approach to producing gamma-ray spectra. This was essential to access the weak $3^-\rightarrow2^+$ $\gamma$-ray decay, the key result of this work and Dr Ben Jones PhD thesis. The approach builds upon our previous study of $^{222}$Rn (https://doi.org/10.1103/PhysRevC.105.024323), wherein we energy of a single segment (cathode) as opposed to the standard method of using the core (anode) signals. This method provided superior energy resolution but at the cost lower detection efficiency. In the analysis of $^{144}$Ba, we advance this method by summing the energies of the individual segments. For this, we implemented a procedure for correcting crosstalk between the signals, based on the methods developed by the GRIFFIN collaboration, which allow up to four segment events to be summed together. This method could prove highly effective for experiments which suffer from high instantaneous rates and where high-quality energy resolution is paramount.

Speaker: Pietro Nicola Spagnoletti (University of Liverpool (GB))

HIE-ISOLDE-Presenntation.pdf

09:40 → 10:00 Fission

09:40 Beyond the Barrier - Fission studies at ISS

Where do the heaviest elements in the Universe come from? Gold, platinum,
uranium are not made on Earth, but forged in some of the most violent events in
the cosmos, such as the collisions of neutron stars. There, atomic nuclei
capture neutrons and grow heavier and heavier, until they become so unstable
that they split in two. This splitting, called \textit{nuclear fission}, sets a limit on
how heavy the elements around us can be, and shapes which ones survive to become
part of planets, and of us.

To understand that limit, we need to measure how easily these exotic nuclei
break apart, that is, how high the energy barrier is that holds each one
together. But many of the nuclei that matter most live for only a fraction of a
second and cannot be easily studied in the usual way, because they cannot be
held still as a target.

This thesis develops a new experimental method to reach them, using radioactive
beams produced at CERN and a magnetic spectrometer that catches the fragments
and particles emerging from each fission event. It is a first step towards
recreating, in the laboratory, the physics that builds the elements in the
stars.

Speaker: Maria Vittoria Managlia (Chalmers University of Technology (SE))

HIE_ISOLDE26_MVManaglia.pdf

10:00 → 10:30 Fika (break)

10:30 → 12:10 New infrastructure and developments

Convener: Prof. Luis M Fraile (CERN)

10:30 Expanding the HIE–ISOLDE Physics Programme with ISLS and ISRS

.

The HIE–ISOLDE facility has established a broad programme of nuclear structure and reaction studies with radioactive ion beams, particularly through the Miniball, ISS, and SEC collaborations. Despite these achievements, several physics questions remain challenging due to limitations in sensitivity and selectivity, especially for low-intensity beams and weak reaction channels.

This contribution explores new directions for extending the reaction physics programme at HIE-ISOLDE, building on recent developments within the ISRS collaboration [1, 2]. As an example, in the heavy-mass region, the physics program focuses on the determination of single-particle structure and spectroscopic factors around doubly magic nuclei such as 132Sn, which are essential for understanding r-process nucleosynthesis near the N = 82 shell closure. Multinucleon transfer reactions at near-barrier energies provide a promising route to access neutron-rich nuclei approaching the N = 126 region, of particular relevance for nuclear structure and astrophysics. For light exotic systems, the programme targets the investigation of halo and skin structures through elastic, inelastic, breakup, and transfer reactions, as well as the determination of (α,n) reaction rates relevant to the r-process. Altogether, these selected topics illustrate an ambitious scientific programme spanning nuclear structure, reaction dynamics, and astrophysics.

Realising this programme requires improved capabilities for reaction-product identification at forward angles. Recent developments within the ISRS collaboration have demonstrated substantial progress in the design study of this cutting-edge spectrometer, including advanced reaction modelling, beam-dynamics optimisation, high-resolution focal plane detector arrays, the multi-harmonic buncher, and the successful construction of a cryogen-free superconducting magnet prototype, MAGDEM [3], the building block of the ISRS particle storage ring. A phased approach aligned with the CERN programme is envisaged. In Run 4, initial experiments will be carried out with the ISOLDE Superconducting Linear Spectrometer (ISLS), within the framework of the approved IONTB installation programme at ISOLDE [3]. This will provide improved recoil identification and background suppression, allowing to study weak reaction channels using low-intensity radioactive beams. Based on this experience, subsequent phases will evolve towards the construction of the ISRS spectrometer, leading to an important expansion of the HIE–ISOLDE reaction programme through improved resolution, efficiency, and selectivity.

This contribution is intended as a starting point for discussion, with the aim of identifying scientific priorities, flagship experiments, and fostering new collaborations across the HIE–ISOLDE community, in view of the upcoming CERN roadmap for non-collider physics.
.
References
[1] Design study of a Superconducting Recoil Separator for HIE-ISOLDE
(ISRS), Letter of Intent CERN-INTC-I-228, 2021.
[2] I. Martel et al., An innovative Superconducting Recoil Separator for HIE–
ISOLDE, Nucl. Instrum. Methods B 541 (2023) 176–179.
[3] ISRS Collaboration website, https://www.uhu.es/isrs/.
[4] Installation and commissioning of the ISRS Ion Test-bench and Multi-
Harmonic Buncher at HIE-ISOLDE, Letter of Intent CERN-INTC-283,
2025.

Speaker: Ismael Martel (University of Huelva (ES))

ISRS-Physics.pdf

ISRS-Physics.pptx

10:50 The ISOLDE Superconducting Linear Spectrometer

The ISLS (ISOLDE Superconducting Linear Spectrometer) is a by-product of the ISOLDE Superconducting Recoil Separator (ISRS) project. It integrates MAGDEM (MAGnet DEMonstrator), the fundamental building block of the ISRS particle storage ring.
MAGDEM is an extremely compact, helium-free Nb-Ti CCT superconducting magnet cooled by a single Gifford–McMahon (GM) cryocooler. It incorporates nested quadrupole and dipole functions within a single cryostat. The cryostat features a 200 mm clear aperture for the transport of heavy-ion reaction products and has an overall length of only ~750 mm. The innovative design places a 2.3 T dipole coil inside a 10 T/m quadrupole coil, providing the 36° bend required for ion analysis and storage in the ISRS ring.
The aim of the ISLS is to integrate MAGDEM into an ion-optical system for nuclear reaction studies, thereby demonstrating its performance and validating beam dynamics simulations. The system also includes a reaction chamber for both solid and gas targets, focusing elements, and focal-plane detectors. The main design goals of the ISLS are high transmission (ideally approaching 100%), a compact layout compatible with the XT03 experimental area at HIE-ISOLDE, and high mass dispersion to optimize isotope separation.
The baseline ion-optical design was developed using the codes BMAD, GICOSY, and COSY INFINITY. The beam optics were optimized in the horizontal (x–a) and vertical (y–b) phase spaces, while mass, energy, and momentum deviations (δm, δE, and δp) were treated as parameters. The required focusing condition at the final focal plane is point-to-point imaging in both transverse planes, i.e., (x,a) = (y,b) = (0,0). The proposed ISLS lattice consists of two quadrupole magnets surrounding MAGDEM in a symmetric QMQ configuration. This arrangement minimizes optical aberrations while maintaining a compact footprint and provides mass and energy dispersions of approximately 0.6 cm/% together with a momentum dispersion of approximately 1.2 cm/%.
Commissioning with both stable and radioactive ion beams is foreseen during LS3 to validate the magnet performance and benchmark the beam dynamics simulations relevant to the ISRS over a range of isotopes and beam energies. The expected performance of the ISLS will be presented for representative nuclear reactions involving light- and medium-mass isotopes of interest for nuclear astrophysics.

Speaker: Teresa Kurtukian Nieto (Consejo Superior de Investigaciones Cientificas (CSIC) (ES))

Goteborg_agosto2026_TKN.pdf

11:10 Short break

11:20 Direct neutron-capture on short-lived nuclei: a free-neutron-target opportunity for HIE-ISOLDE

Radiative neutron capture (n,γ) reactions govern the nucleosynthesis of heavy elements in stars through the slow (s-), intermediate (i-), and rapid (r-) neutron capture processes. Despite more than 70 years of experimental effort, direct (n,γ) cross-section measurements have been performed on only ~350 stable nuclei and merely 17 radioactive isotopes.
The difficulty lies in the need to produce a macroscopic sample of the radioactive species of interest, which is not feasible for nuclei with half-lives shorter than ~1 year. As a result, nucleosynthesis calculations for thousands of unstable nuclei rely almost exclusively on theoretical predictions, with uncertainties reaching orders of magnitude away from stability.
A way around this limitation is to measure neutron-induced reactions in inverse kinematics, with the radioactive ions circulating in a low-energy storage ring and interacting with a free-neutron target [1,2]. Each ion passes through the target at revolution frequencies of 100–1000 kHz, effectively replacing the radioactive sample and increasing the reaction rate by 5–6 orders of magnitude compared to conventional experiments. Coupled to an ISOL-type radioactive-ion-beam facility, this would give direct experimental access to more than 1000 nuclei with half-lives of minutes or even seconds. The original concepts relied on a nuclear reactor [1] or a spallation source [2] to provide the free neutrons. A recent conceptual design aimed at cost-efficiency and feasibility proposes a compact, integrable neutron target using a commercial supercompact medical cyclotron driving a ⁹Be(p,xn) free-neutron source [3].
Realizing this capability at CERN is the subject of two Expressions of Interest to the CERN Non-Collider Physics Roadmap: a dedicated low-energy Ion Storage Ring at HIE-ISOLDE, and a free-neutron target coupled to it [4]. The neutron target remains to be demonstrated, and two complementary production technologies would be studied in parallel: the supercompact-cyclotron approach [3] and a spallation-based target building on n_TOF expertise. A first proof-of-concept of the cyclotron approach is proposed at CRYRING@ESR, and an initial demonstration stage has already begun in Spain. This contribution presents the neutron-target concept, its staged demonstration path, and the perspectives it opens for a direct neutron-capture programme at HIE-ISOLDE.

References
[1] R. Reifarth & Y. A. Litvinov, Phys. Rev. ST Accel. Beams 17, 014701 (2014).
[2] R. Reifarth et al., Phys. Rev. Accel. Beams 20, 044701 (2017).
[3] A. Tarifeño-Saldivia, C. Domingo-Pardo, I. Dillmann & Y. A. Litvinov, Phys. Rev. Accel. Beams 29, 061601 (2026), doi:10.1103/5d87-m8bn.
[4] Expressions of Interest, CERN 20-Year Roadmap of the Non-Collider Physics Programme (2026): "Heavy-ion storage ring at ISOLDE" (Yu. A. Litvinov et al.) and "Direct Studies of Neutron-Induced Reactions in Inverse Kinematics" (C. Domingo-Pardo, Y. Litvinov et al.).

Speaker: Ariel Esteban Tarifeno Saldivia (Instituto de Física Corpuscular (IFIC), CSIC-UV, Spain)

ATarifeno_2ndHIEisolde_NRING_LQ.pdf

11:40 Discussion

Speakers: Prof. Luis M Fraile (CERN), Sean John Freeman (The University of Manchester (GB))

12:10 → 13:30 Lunch

13:30 → 14:10 Shell closures and shell evolution

13:30 The quadrupole moments of the $2^{+}_{1}$ state in the even neutron deficient Sn isotopes

Recent Monte Carlo Shell Model (MCSM) calculations made by T. Togashi et. al. [Phys. Rev. Lett. 121, 062501 (2018)] attempt to account for discrepancies observed between measurements and previous theoretical calculations of the reduced transition probability B(E2;$2^{+}_{1}->0^{+}_{1}$) in the neutron deficient Sn isotopes. One of the predictions of the MCSM calculation is that a shape change should occur for the $2^{+}_{1}$ state between ${}^{108}$Sn and ${}^{110}$Sn. In this work we present the first experimental results for the quadrupole moment for this state in ${}^{110}$Sn, along with preliminary results for ${}^{106}$Sn and ${}^{108}$Sn in order to address this question. The measurement results were obtained through a safe Coulomb excitation experiment at HIE-ISOLDE, using the Miniball setup. A novel analysis approach combining GOSIA and GOSIA2 codes with a DSAM measurement was used to calculate both diagonal and transitional matrix elements. Preliminary results are compared to MCSM calculations and observations regarding a shape change in the $2^{+}_{1}$ state are discussed.

Speaker: Rafael Antonio Lopez

13:50 Nuclear Structure and Collectivity of Neutron-Rich Tin Isotopes around $^{132}$Sn

Coulomb excitation of the neutron-rich, even-even isotopes $^{130}$Sn and $^{134}$Sn was performed at the HIE-ISOLDE facility using post-accelerated radioactive ion beams at an energy of 4.4 MeV/u, impinging on $^{206}$Pb and $^{194}$Pt targets. The de-exciting $\gamma$ rays were detected with the refurbished high-efficiency Miniball spectrometer in coincidence with scattered particles, enabling a precise determination of electromagnetic matrix elements. The extracted $B(E2; 0^+_\mathrm{g.s.} \rightarrow 2^+_1)$ transition strengths resolve a long-standing discrepancy between previous experimental results and theoretical predictions of quadrupole collectivity in these isotopes. In addition, the newly determined spectroscopic quadrupole moments are found to be consistent with zero within the experimental uncertainties, supporting a predominantly near-spherical shape for nuclei in the immediate vicinity of the $^{132}$Sn core.

Modern shell-model calculations, including both large-scale diagonalization and Monte Carlo approaches, successfully reproduce the measured $E2$ strengths. The new large-scale calculations further underline the importance of effective nucleon charges and particle-hole core excitations across the $Z=50$ and $N=82$ shell gaps for a quantitative description of the observed collectivity. Overall, these results provide strong experimental evidence for the robustness of the doubly magic character of $^{132}$Sn and help to clarify the evolution of quadrupole collectivity around this key nucleus.

Speaker: Maximilian Paul Droste (Universitaet zu Koeln (DE))

hie-isolde_conference_droste.pptx

14:10 → 14:40 Light nuclei and reactions, dripline and beyond

14:10 The Scattering Experiments Chamber and the Study of Exotic Nuclei: The Case of $^{13}Be$

The Scattering Experiments Chamber (SEC) is the third and final experimental station installed at HIE-ISOLDE on the XT03 beamline. Its large dimensions allow the integration of complex experimental setups combining both charged-particle detectors and scintillator arrays. This flexibility provides an ideal environment for reaction studies over the full angular range, enabling experiments on nuclei ranging from the heaviest isotopes to the lightest systems.

One such case is the investigation of the unbound nucleus $^{13}Be$. Understanding the $^{12}Be-n$ interaction is essential for constraining the structure and formation of the two-neutron halo nucleus $^{14}Be$. Although $^{13}Be$ has been previously studied, the nature of its low-lying resonances remains under debate, in particular the ordering of the $1/2^+$ and $1/2^-$ states.

To address this question, a new experimental approach has been implemented at SEC. The resonant states of $^{13}Be$ are populated through the two-neutron transfer reaction (t,p) in inverse kinematics using a radioactive $^{11}Be$ beam at 5.4 MeV/u incident on a state-of-the-art solid radioactive $^{3}H$ target.

The versatility of SEC allows the combination of several charged-particle detector systems, providing nearly full angular coverage and enabling an exclusive reconstruction of the reaction channel through the detection of the outgoing charged particles. Combined with a new-generation GAGG scintillator array, this setup makes it possible to investigate the decay of $^{13}Be$ into excited states of $^{12}Be$.

In this contribution, we present SEC together with the first preliminary results from the ongoing analysis of the $^{13}Be$ experiment. We also discuss complementary studies of the exotic beryllium isotopes $^{11}Be$ and $^{12}Be$.

Speaker: Sebastian Gomez Garcia (Consejo Superior de Investigaciones Cientificas (CSIC) (ES))

HIE-ISOLDE-sebas-Final.pdf

HIE-ISOLDE-sebas-Final.pptx

14:40 → 15:00 Fika (break)

15:00 → 15:50 Shell closures and shell evolution

15:00 Coulomb excitation of $^{212}$Ra at HIE-ISOLDE

The generalised seniority scheme is a truncated version of the nuclear shell model [1]. It is able to describe the structure of atomic nuclei in the vicinity of shell closures. The number of unpaired nucleons, the seniority $\nu$, is considered a good quantum number.
The region of the even-even Po-Rn-Ra nuclei with $N=124$ exhibits strong signs of seniority-like behaviour. This can be observed, e.g. in the energy spacing between excited yrast states which decreases at higher angular momenta. However, no experimental data is available to confirm or falsify the anticipated parabolically increasing trend in the absolute $E2$ transition strength with the filling of the $j$-shell for the $\Delta\nu=2$ seniority-changing $2_1^+\to0_1^+$ transition [2]. Therefore, a Coulomb-excitation experiment was conducted at HIE-ISOLDE in 2024 in order to obtain the $B(E2; 2_1^+\to0_1^+)$ value of $^{212}$Ra. The $^{212}$Ra beam was impinged on a $^{120}$Sn target with $4.51\,$MeV/u to ensure safe Coulomb excitation. $\gamma$ rays of deexciting $^{212}$Ra nuclei were observed by the high-purity germanium detectors of the Miniball array [3] while ejectiles and recoiling particles were recorded by a double-sided silicon strip detector at forward angles. From the $\gamma$-ray yields the $E2$ strength of the $2_1^+\to0_1^+$ transition can be then deduced. The current state of the analysis will be presented.

[1] I. Talmi, Nucl. Phys. A 172, 1 (1971).
[2] J. J. Ressler et al., Phys. Rev. C 69, 034317 (2004).
[3] N. Warr et al., Eur. Phys. J. A 49, 40 (2013).

Speaker: Hannes Mayr (Technische Universitaet Darmstadt (DE))

HIE-ISOLDE2026_HMayr_public.pdf

15:20 (d,p) measurements with ISS into the Mg island of inversion.

The status of transfer reaction measurements focussed on the Mg island of inversion, which build on the study of 28Mg(d,p) performed in RUN2, will be summarised.

Measurements of the (d,p) reaction on beams of 27Na and 27Mg have been performed with ISS. The cross sections have been analysed using two different reaction models with a high degree of consistency. Comparisons of strength distributions deduced experimentally give good agreement with those expected from shell-model calculations. Distributions of negative-parity strength are well reproduced by interactions optimised for cross-shell excitations whereas the comparison of positive-parity strength highlights aspects of sd interactions that are currently less well constrained.

The analysis of data from 30Mg(d,p) is on-going and an update will be presented.

Speaker: Sean John Freeman (The University of Manchester (GB))

higher-energies.pdf

higher-energies.pptx

15:50 → 15:55 Dinner information (location etc)

15:55 → 16:00 Break

16:00 → 17:00 Closed meeting: ISS Management Meeting

18:45 → 22:00 Dinner

Göta Älv + Southern Archipelago

Friday 21 August

09:00 → 09:30 Results from other facilities

09:00 Overview of the HiCARI project at the RIBF

The High-resolution Cluster Array at the RIBF (HiCARI) was a limited-time installation of segmented high-purity germanium detectors of different types at the RIBF, RIKEN. Three experimental campaigns covering a broad range of physics topics were conducted with HiCARI over a two-year period. The in-beam gamma-ray spectroscopy experiments covered a wide range of the available beams at the RIBF with mid-target energies of ~100-200 MeV/nucleon.

Over the course of the talk, the RIBF will be introduced, the HiCARI array detailed, and recent results discussed. Future perspectives of in-beam gamma-ray spectroscopy experiments at the RIBF will also be briefly presented.

Speaker: Frank Browne (The University of Manchester (GB))

09:30 → 09:50 Shapes and collectivity

09:30 Octupole collectivity in the neutron-rich lanthanides at HIE-ISOLDE

Identifying nuclei that have a stable octupole deformation is crucial to the search for odd mass isotopes with atomic electric-dipole moments (EDMs). Observation of a non-zero atomic EDM at the current levels of experimental precision would indicate $CP$ violation and would imply new physics beyond the standard model. Nuclear mean-field calculations predict that octupole correlations are enhanced for certain nuclei in the actinide and lanthanide regions of the nuclear chart. The magnitude of octupole correlations can be inferred from the structure of nuclear energy levels and enhanced $E1$ transition strengths, although shell effects can complicate the interpretation of such data. The $E3$ moment is the observable that provides the most unambiguous measure of enhanced octupole correlations, being insensitive to single particle effects. Direct measurements of the $E3$ moments in $^{222,224,226}$Ra show they exhibit stable octupole deformation, while $^{228}$Ra behaves as an octupole vibrator~[1]. Current experimental $B(E3)$ data in the lanthanide region however is scarce. Measurements reported for the $B(E3)$ of $^{144,146}$Ba~[2,3] are significantly enhanced over theory and are consistent with octupole deformation, but have very large associated uncertainties.

This talk will discuss a series of complementary experiments performed at HIE-ISOLDE on $^{142,144}$Ba using the techniques of inelastic scattering at ISS and Coulomb excitation at Miniball. The ISS experiment represents the first attempt to measure reactions in the forward going direction and required the whole experiment to be rotated by 180˚, which presented a new set of challenges, particular with respect to beam tuning. The Miniball experiments were performed across 3 different campaigns in 2017, 2018 and 2024 and used both nickel and lead targets to improve the sensitivity to multi-step Coulomb excitation pathways. The results indicate the $B(E3)$ values in the barium isotopes are in line with almost all recent mean-field predictions and are not significantly enhanced as previously indicated. Taken together with recent results in the gadolinium isotopes~[4], experimental evidence is pointing towards the centre of octupole collectivity being at larger Z values than previously thought, prompting a new look at the lanthanide region and a wider programme of experiments to come at HIE-ISOLDE and beyond!

Most of the work being presented is that of Ben Jones, a recently graduated PhD student at the University of Liverpool.

[1] P. A. Butler et al., “Evolution of Octupole Deformation in Radium Nuclei from Coulomb Excitation of Radioactive $^{222}$Ra and $^{228}$Ra Beams”, Physical Review Letters, 124, 042503 (2020), doi:10.1103/PhysRevLett.124.042503.
[2] B. Bucher et al., “Direct Evidence of Octupole Deformation in Neutron-Rich $^{144}$Ba”, Physical Review Letters, 116, 112503 (2016), doi: 10.1103/PhysRevLett.116.112503.
[3] B. Bucher et al., “Direct Evidence for Octupole Deformation in $^{146}$Ba and the Origin of Large $E1$ Moment Variations in Reflection-Asymmetric Nuclei”, Physical Review Letters, 118, 152504 (2017), doi:10.1103/PhysRevLett.118.152504.
[4] S. Pascu et al., “Increasing Octupole Collectivity across the $Z=64$ Isotopic Chain: $B(E3)$ Values in $^{150}$Gd”, Physical Review Letters 134, 092501 (2025), doi:10.1103/PhysRevLett.134.092501

Speaker: Liam Gaffney (University of Liverpool (GB))

HIE-ISOLDE-2026_BaCoulex_Gaffney.pdf

HIE-ISOLDE-2026_BaCoulex_Gaffney.pdf

HIE-ISOLDE-2026_BaCoulex_Gaffney.pptx

HIE-ISOLDE-2026_BaCoulex_Gaffney.pptx

09:50 → 10:20 Fika (break)

10:20 → 10:40 New techniques and methods

10:20 Gain with Millepede Equaliser and Luxury Matching

Double-sided silicon strip detectors (DSSSDs) are used in many experiments.  They provide good position resolution and help reduce the readout capacitance.  However, calibrating many individual strips can be challenging.

A tool that almost automatically performs an internal gain-matched calibration will be presented.  It is based on Millepede II, which is typically used for detector alignment in large-scale experiments, and here utilises correlations between the two sides of the DSSSDs.  These calibrations can use almost any data, i.e., are not limited to alpha source runs.

For the reconstruction phase of analysis, a routine that performs disambiguation of physical multi-hit events and shared-energy deposits in neighbouring strips will also be introduced.  It chooses between many solutions by almost exhaustively considering many permutations of combining shared-energy deposits of the two sides, while keeping evaluation times short.

Speaker: Hakan Johansson (Chalmers University of Technology (SE))

htj_aug2026_gain_match.pdf

10:40 → 11:10 Plans after Long Shutdown 3

10:40 HI-TREX: Next Generation of Transfer-Reaction Experiments at HIE-ISOLDE

HI-TREX is the next-generation silicon detector array for transfer-reaction studies at HIE-ISOLDE. Improved granularity, increased solid-angle coverage, modern ASIC-based readout electronics, and enhanced rate capability will significantly extend the experimental possibilities for charged-particle spectroscopy in combination with the MINIBALL $\gamma$-ray spectrometer.

This contribution will present the current status of the HI-TREX project, including detector development and commissioning, and conclude with an outlook on the broad physics opportunities that the HI-TREX-MINIBALL setup will provide for transfer-reaction studies with radioactive ion beams.

Speaker: Kathrin Wimmer (University of Cologne)

test.pdf

11:10 → 11:20 Short break

11:20 → 12:00 Plans after Long Shutdown 3

11:20 OSCAR at ISOLDE

For the next run period at ISOLDE, the Nuclear Physics group at the University of Oslo are considering proposing a longer experimental campaign with the Oslo SCintillator ARay (OSCAR). The main aims of such a campaign will be to measure the nuclear level density and $\gamma$-ray strength function of key nuclei relevant for nuclear structure and nuclear astrophysics (e.g. i-process nucleosynthesis). Other cases of interest could be spectroscopy of resonances in light exotic nuclei or rare event searches. In addition, we would also invite other interested groups to propose experiments with the setup while it is present at HIE-ISOLDE.

The OSCAR array is the largest LaBr$_3$:Ce detector array in the world (at least in terms of detector volume). It offers exceptional efficiency for high-energy $\gamma$-rays without compromising on either energy or time resolution. It consists of 30 large 3.5x8-inch large volume LaBr3:Ce detectors, an icosahedron frame with six rings covering polar angles from $37.4^\circ$ to $142.6^\circ$. Detectors can be mounted in a distance of 16.3 to 22 cm from the target, resulting in solid angle coverage of 57%. This translates to about 15% full energy efficiency at 1332 keV and close to 5% at 10 MeV in the closest configuration.

In this presentation I will present the physics cases and our preliminary plans for such a campaign.

Speaker: Dr Vetle Wegner Ingeberg (Department of Physics, University of Oslo)

2ndHIEISOLDEWorkshopIngeberg_upload.pdf

2ndHIEISOLDEWorkshopIngeberg_upload.pptx

11:40 Post-accelerated polarized radioactive ion beams? Why and possibly how.

Getting control of an additional degree of freedom of a system is a dream and a challenge for any experimentalist. Experiments with spin-polarized stable beams were done around 1990’s. However, with the change of the paradigm and the advances of Radioactive Ion Beam (RIB) - based nuclear structure studies, this subject of research has been slowly fading away. The questions that we would like to explore are:
i) Is there an interest in doing nuclear structure studies with polarized RIB’s? Can they bring in further sensitivity, not attainable at present?
ii) What could be the different technical approaches for producing polarized post-accelerated RIB’s? How realistic are these, and what are the necessary efforts?
The Tilted-Foils method, which has been previously explored at different facilities, ISOLDE included, will be discussed as one of the options for polarizing radioactive ions. Its advantages, shortcomings, and points of necessary further investigations will be presented.
This talk will be oriented towards initiating the discussion within the community rather than providing the answers.

Speaker: Georgi Georgiev (Université Paris-Saclay (FR))

HIE-ISOLDE_WS_Georgiev.pdf

HIE-ISOLDE_WS_Georgiev.pptx

12:00 → 13:30 Lunch

13:30 → 14:10 Plans after Long Shutdown 3

13:30 Synergy betwen HIE-ISOLDE and LIC Studies of Nuclear Shapes

Here we present the scientific motivation for investigating the shapes of benchmark nuclei at the LHC ($^{12}$C, $^{24}$Mg, $^{48}$Ca, $^{76}$Ge-$^{86}$Kr and $^{136}$Xe-$^{136}$Ba), which can also be studied through low-energy Coulomb-excitation measurements at HIE-ISOLDE. By combining complementary measurements across these two energy regimes, these benchmark nuclei offer a unique opportunity to establish a common framework that links nuclear structure with high-energy collision hydrodynamic models, thereby strengthening the interpretation of experimental results in both fields.

On the one hand, the initial nuclear geometry provides essential experimental constraints for interpreting observables such as nuclear clusters, triaxiality and shape fluctuations in light-ion collisions (LIC) at the LHC, where the overlap geometry or collision centrality, is strongly influenced by the spatial distribution of nuclear matter prior to impact. On the other hand, precise knowledge of these nuclear shapes has important implications for understanding proton–neutron correlations that govern shape coexistence and the collective nuclear behaviour, in general. In fact, their underlying structure remains the subject of contrasting theoretical interpretations, highlighting the need for precision Coulomb-excitation measurements. Such measurements are feasible at HIE-ISOLDE and will form the foundation of a broader research programme on such benchmark nuclei to be discussed and developed within the HIE-ISOLDE collaboration, leading to a detailed Expression of Interest to be submitted to the INTC.

Speaker: Jose Nicolas Orce Gonzalez (University of the Western Cape (ZA))

HIEPhysics_Orce.pdf

13:50 Probing exotic nuclei with an active target in a magnetic field: the AT-TPC at ISS

Direct reactions in inverse kinematics are among the most powerful probes of the structure of exotic nuclei, but their study with post-accelerated radioactive beams is often limited by the trade-off between target thickness and resolution, and by the low intensities available for the most exotic species. We propose to bring the Active Target Time Projection Chamber (AT-TPC) to ISOLDE and to install it inside the ISOLDE Solenoidal Spectrometer (ISS), combining two proven and complementary techniques in a single device.

In the AT-TPC, the gas volume acts simultaneously as target and tracking medium, providing an effectively thick target without loss of resolution, near 4π angular coverage, and the ability to reconstruct the reaction vertex on an event-by-event basis. These features make it exceptionally well suited to beams with intensities down to a few hundred particles per second. Operated inside the solenoidal field of ISS, the magnetic rigidity of the tracked light recoils provides an additional and precise measurement of their momentum, substantially improving the excitation energy resolution and particle identification compared to a purely ionization based measurement.

The combination of HIE-ISOLDE beams with this instrument would open a broad physics programme: single-particle structure via (d,p) and (p,d) transfer, resonant elastic and inelastic scattering, clustering phenomena, and reactions of astrophysical interest, extending the reach of ISS to the most weakly produced beams. In this contribution we will present the scientific case, the conceptual and mechanical integration of the AT-TPC in the ISS magnet bore and the expected performance from previous experiments and realistic simulations.

Speaker: Yassid Ayyad (Universidade de Santiago de Compostela)

ATTPC_HIEISOLDE_v1.0.pdf

ATTPC_HIEISOLDE_v1.0.pptx

14:10 → 16:10 Discussions - Proposals

Convener: Sean John Freeman (The University of Manchester (GB))

fraile_HIE-ISOLDE_EoI_discussion.pdf

14:10 Discussions - Proposals

15:00 Fika (break)

15:20 Discussions - Proposals (cont'd)