ISS: The Isolde Solenoidal Spectrometer
14 Sep 2023



The Isolde Solenoidal Spectrometer (ISS) is an experimental setup for nuclear physics research, installed and operated at the radioactive ion beam accelerator HIE-ISOLDE at CERN.




The front entrance of the ex-MRI superconducting magnet 

reconverted for blue sky nuclear physics research

​The ISS is a recently built experimental setup for precision nuclear structure studies using inelastic scattering and transfer reactions induced by radioactive ion beams. 

The system comprises a set of movable silicon position-sensitive detectors and a target-changing mechanism, cleverly positioned along the beam axis inside a superconducting solenoid magnet. Under the presence of the magnetic field, the light-charged particles (protons, deuterons, tritons, alphas) emitted in the nucleon transfer reactions are directed into a silicon position-sensitive array. The latter provides a precise measurement of the distance detection position-to-target and the energy of the light ions. This collected information together with the known parameters of the reactions (incoming beam energy, magnetic field intensity, target thickness, etc.) allows physicists to reconstruct the angular distribution of these light-emitted ions, which then reveals characteristics of the nuclear structure of the incoming ions.  

The detector bed and support, target-changing mechanism, and the primary silicon position sensitive detector, designed and assembled at STFC Daresbury Laboratory prior to shipping to CERN. Three sides of the hexagonal shape primary detectorarevisible at the top-centre of the left picture. 

Four groups from the Technology Department at Daresbury Laboratory were involved in this project. They include:  

  • Projects and Mechanical Engineering - for mechanical engineering and design, construction and assembly test of the silicon array and target changing mechanism
  • Mechanical, Metrology, and Technical Engineering
  • Electrical Engineering- for the installation and test of the motorisation control system
  • Nuclear Physics - for experiment design simulations, assembly and vacuum test, magnet safety and operation at CERN, electronics and data acquisition system, and commissioning plus exploitation. 


Geometry of the target holder, the detector bed and support, and the primary detector defined in a GEANT4 

simulation. Four transfer reaction events have been simulatedThe tracks of the light particles emitted in

 backward direction related to the beam are displayed in blue.

An animation showing simulated light charged particles event-by-event

Further information

​Learn more about the ISS:

​Written by Marc Labiche, Nuclear Physics ​group leader.​