The General-Low-Mass beamline, or GLM, is a central facility for the collection and implantation of radioactive isotopes at ISOLDE. A newly developed implantation chamber modernizes this process. The system features two separately evacuated chambers: an implantation chamber and a lock chamber for sample exchange. Through an exit port, samples can be removed for further experiments or directly coupled to the GLM ion beam. Connected systems include, among others, ASCII as well as Mössbauer and TDPAC spectroscopy setups. The new chamber thus serves as a flexible interface between the production of radioactive isotopes and their application in materials science.

• Yap, I.C.J., Grillo Munoz, J.F., Dorsival, A., Pohl, C., Lupascu, D.C., Hofsäss, H.C., Di Giulio, L., Nagl, M., Beltramello, O., Dang, T.T., Vetter, U. and Heiniger-Schell, J. (2026), ‘The new ion-implantation chamber in the General Low Mass (GLM) area of ISOLDE’, Hyperfine Interactions, vol. 247, article 18. https://doi.org/10.1007/s10751-025-02345-1.
• Yap, I.C.J. (2025), ‘The new ion-implantation chamber in the General Low Mass (GLM) area of ISOLDE’, poster presented at the ISOLDE Workshop and Users Meeting 2025, CERN, Geneva, 3 December 2025. Available at: https://indico.cern.ch/event/1576520/contributions/6762803/

MULTIPAC stands for "Multifunctional Perturbed Angular Correlations." The facility employs time-differential perturbed angular correlation, or TDPAC. In this technique, two successive gamma quanta emitted by an implanted probe atom are detected. From their temporal and angular correlation, local electric and magnetic fields within the material can be determined.

MULTIPAC combines this atomic-scale measurement technique with temperatures ranging from approximately 3 to 375 kelvin and external magnetic fields of up to 8.5 tesla. The detector system consists of six fast LaBr₃(Ce) scintillation detectors coupled to silicon photomultipliers. The facility is particularly well suited to magnetic and multiferroic materials, in which electric and magnetic orders are coupled to one another.

This enables researchers to track how the local structure and macroscopic material properties evolve during a phase transition. MULTIPAC thus opens new avenues for the development of energy-efficient magnetic materials, sensors, and functional materials.

• Lupascu, D.C., Schell, J., Dang, T.T. and Schmuck, M. (2020), MULTIPAC-Setup for γ–γ Perturbed Angular Correlation Experiments in Multiferroic and Magnetic Materials, CERN-INTC-2020-011, INTC-I-212, CERN, Geneva. Available at: https://cds.cern.ch/record/2706092/files/INTC-I-212.pdf.
• Schell, J.H., Lupascu, D.C. et al. (2023), MULTIPAC-Setup for Perturbed Angular Correlation Experiments in Multiferroic and Magnetic Materials: Proof of Concept, CERN-INTC-2023-012, INTC-I-249, CERN, Geneva. Available at: https://cds.cern.ch/record/2845935/files/INTC-I-249.pdf.

PACBit is the software and data-acquisition platform developed specifically for MULTIPAC and other TDPAC facilities. It processes the large data streams from the fast detectors in streaming mode on a central high-performance computer.

The software smooths and corrects the signals, assigns precise timestamps, and identifies coincident gamma quanta. Through parallel processing, the characteristic TDPAC function R(t) can be displayed in real time during the experiment. This enables rapid quality control and reduces the effort required for subsequent data analysis.

PACBit thus bridges detector technology, high-performance computing, and materials science. Together with MULTIPAC, the system constitutes the third generation of digital TDPAC spectrometers at ISOLDE.

• Dörschel, B., Yap, I.C.J., Heiniger-Schell, J. and Lupascu, D.C. (2026), ‘MULTIPAC and PACBit – Third Generation of TDPAC Spectroscopy: Results of Project LOI249’, ISOLDE Newsletter 2026, p. 49, CERN, Geneva. Available at: https://isolde.web.cern.ch/sites/default/files/ISOLDE_Newsletter_2026_0.pdf

GLM, ASCII, eMIL/eMMA, MULTIPAC, and PACBit form an integrated experimental chain: from the controlled implantation of radioactive probes, through measurements under defined temperature and magnetic-field conditions, to automated data analysis.

UDE's involvement links materials-science questions with CERN's unique isotopic diversity and infrastructure. This yields new insights into functional materials — from atomically thin layers and interfaces to magnets and multiferroics for future energy and information technologies.

• Catherall, R. et al. (2017), ‘The ISOLDE facility’, Journal of Physics G: Nuclear and Particle Physics, vol. 44, article 094002. https://doi.org/10.1088/1361-6471/aa7eba.
• Johnston, K., Schell, J., Correia, J.G., Deicher, M., Gunnlaugsson, H.P., Fenta, A.S., David-Bosne, E., Costa, A.R.G. and Lupascu, D.C. (2017), ‘The solid state physics programme at ISOLDE: Recent developments and perspectives’, Journal of Physics G: Nuclear and Particle Physics, vol. 44, article 104001. https://doi.org/10.1088/1361-6471/aa81ac.
• Schell, J., Schaaf, P. and Lupascu, D.C. (2017), ‘Perturbed angular correlations at ISOLDE: A 40 years young technique’, AIP Advances, vol. 7, article 105017. https://doi.org/10.1063/1.4994249.
• CERN Solid State Physics Group (n.d.), ‘Solid State Physics at ISOLDE-CERN’, CERN. Available at: https://ssp.web.cern.ch/ (accessed 20 October 2026).
• CERN Solid State Physics Group (n.d.), ‘Collaborators’, CERN. Available at: https://ssp.web.cern.ch/collaborators/

ASCII stands for "Apparatus for Surface Physics and Interfaces at CERN's Ion Implantation Chamber." This ultra-high-vacuum facility was developed by the University of Göttingen for the study of thin films, surfaces, interfaces, and two-dimensional materials, and is currently operated by the Institute of Materials Science at UDE.

A key feature is implantation at extremely low energies. The ion beam, which initially arrives at up to 60 kiloelectronvolts, can be decelerated to a few tens of electronvolts. This allows the radioactive probes to come to rest precisely in the topmost atomic layers, at an interface, or at a desired depth, while producing very little implantation damage.

This is important, for example, for graphene, other two-dimensional materials, and multiferroic thin films. In the ultra-high vacuum, samples can also be heated or cooled and examined immediately after implantation. Air-sensitive materials and short-lived isotopes can likewise be analyzed in this way, as can quantum-dot structures.

• van Stiphout, K., Lieske, L.-A., Auge, M. and Hofsäss, H. (2022), ‘Introducing ultra-low-energy ion implantation of radioactive isotopes at ISOLDE, CERN for (near-)surface characterisation: The ASPIC and ASCII vacuum chambers’, Crystals, vol. 12, no. 5, article 626. https://doi.org/10.3390/cryst12050626.
• Pereira de Lima, N. et al. (2024), ‘ASCII: The ultra-low-energy ion implantation of radioisotopes for surface characterisation at ISOLDE-CERN’, contribution presented at EURORIB 2024, Merelbeke, Belgium, 2–7 June 2024. Available at: https://indico.fys.kuleuven.be/event/85/contributions/2190/ (accessed 20 October 2026).
• CERN Experimental Physics Department (2025), ‘ASCII – The Apparatus for Surface Physics and Interfaces at CERN’s Ion Implantation Chamber’, contribution to the ISOLDE Workshop and Users Meeting 2025, CERN, Geneva, 3 December 2025. Available at: https://indico.cern.ch/event/1576520/contributions/6762872/

eMIL is a modular emission Mössbauer spectrometer originally developed at the Technical University of Ilmenau. Radioactive Mössbauer probes are implanted directly into the sample via the GLM facility, after which their hyperfine interactions can be investigated. A major advantage over conventional Mössbauer experiments is that the probe ions are implanted, so the material under investigation does not need to contain iron.

The system enables measurements over a wide temperature range of approximately 100 to 1,100 kelvin. Depending on the configuration, measurements can also be performed under light irradiation, in magnetic fields, or in various crystallographic orientations. Interchangeable modules allow rapid switching between experiments on powders, single crystals, and hot or cold samples.

eMMA — the "Emission Mössbauer Magnetic Analyser" — extends eMIL with magnetic measurement capabilities. A variable magnetic field, a sample manipulator, and a vibrating-sample magnetometer link two levels of observation: Mössbauer spectroscopy reveals the local magnetic interactions at the probe atom, while magnetometry simultaneously captures the macroscopic properties of the entire sample. This makes it possible to investigate which atomic mechanisms govern, for example, the hysteresis, coercivity, or phase transitions of novel magnetic materials.

• Zyabkin, D.V., Vetter, U., Linderhof, F.M.A., Gunnlaugsson, H.P. and Schaaf, P. (2020), ‘eMIL: Advanced emission Mössbauer spectrometer for measurements in versatile conditions’, Nuclear Instruments and Methods in Physics Research Section A, vol. 968, article 163973. https://doi.org/10.1016/j.nima.2020.163973.
• Schaaf, P., Zyabkin, D. and Schell, J. (2020), eMMA – Development of an Emission Mössbauer Apparatus at ISOLDE for the Investigation of Magnetic Materials, CERN-INTC-2020-008, INTC-I-211, CERN, Geneva. Available at: https://cds.cern.ch/record/2705975/files/INTC-I-211.pdf.
• Kern, A. et al. (2023), ‘Emission Mössbauer spectrometer from Ilmenau (eMIL): An update’, poster presented at the ISOLDE Workshop and Users Meeting 2023, CERN, Geneva, 29 November 2023. Available at: https://indico.cern.ch/event/1316940/contributions/5639671/

Building on decades of established infrastructure, the instrument systems described above have been funded over the past ten years through several BMFTR projects (05K16PGA, 05K19PGA, 05K22PGA, 05K22PGB, 05K25PGA):

ISOPAC and ISOSOL provided continuous beam time for user groups. During this period, the multifunctional measurement facility MULTIPAC was also developed, enabling measurements at magnetic fields up to 8.5 tesla and temperatures between 5 and 400 kelvin. The PACBit project is developing entirely new software and measurement hardware. A key objective is to unify all measurement stations on a common platform. In addition to integrating state-of-the-art RF electronics, the analysis software is being built on a unified theoretical framework that also allows for the inclusion of external magnetic fields. The semiconductor photodetectors developed in Göttingen also enable operation in high magnetic fields within MULTIPAC. A user-friendly interface is being developed for future users. The ISOLLINK project helps open up the instruments developed by various German research groups to a broader user community.