1. From ESR to NESR: the EXL experiment at FAIR C. Rigollet - KVI, University of Groningen for the EXL collaboration The EXL collaboration Universität Basel, Switzerland Birmingham University, UK CLRC Daresbury Laboratory, UK TU Darmstadt, Germany GSI, Darmstadt, Germany Institute of Nuclear Research, Debrecen, Hungary Joint Institute of Nuclear Research, Dubna, Russia Edinburgh University, UK Universität Frankfurt, Germany PNPI, Gatchina, and St. Petersburg State University Russia Chalmers Institute, Göteborg, Sweden KVI, University of Groningen, the Netherlands University of Surrey, Guildford, UK Forschungszentrum Jülich, Germany SINP, Kolkata, India University of Liverpool, UK Lund University, Sweden CSIC, Madrid, Spain Universidad Complutense, Madrid, Spain Johannes Gutenberg Universität, Mainz, Germany Universitá da Milano/INFN, Milan, Italy Russian Research Centre, Kurchakov Institute, Moscow, Russia Bhabha Atomic Research Centre, Mumbai, India TU München, Munich, Germany IPN Orsay, France Osaka University, Japan V.G. Khlopin Radium Institute, St. Petersburg, Russia Universidade de São Paulo, São Paulo, Brasil Mid Sweden University, Sundsvall, Sweden University of Tehran, Tehran, Iran The Svedberg Laboratory, Uppsala, Sweden TRIUMF, Vancouver, Canada Spokesperson: Marielle Chartier, University of Liverpool, UK EXL Physics case and Research objectives EXL (EXotic nuclei studied in Light-ion induced reactions at the NESR storage ring) is designed for the study of unstable exotic nuclei using light-ion reactions in inverse kinematics at low momentum transfer. Novel storage-ring techniques in conjunction with a universal detector system providing high-resolution and large angle coverage will give new information on: Nuclear halos, neutron skins (elastic scattering) Properties of N-Z asymmetric matter, proton/neutron deformation, nuclear compressibility (inelastic scattering) Stellar weak interaction rates, Gamow-Teller strengths (charge exchange reactions) Single-particle structure, pairing interaction (transfer reactions) Single-particle structure, nucleon-nucleon and cluster interactions (quasi-free scattering) EXL Design Goals Particles to be detected: ◦ target recoils (p, , n,  ) ◦ forward ejectiles (p, n,  ) ◦ heavy ions High-energy and angular resolution Fully exclusive kinematical measurements High luminosity capability Large solid angle acceptance UHV (< 10 -8 mbar) compatibility High-resolution ToF wall for charged particles and neutrons Phase 1: LAND (  t ~ 300 ps,  x,y,z ~ 7 cm,  n > 90%) – necessitates accommodation of beam pipe between paddles (multi-layered structure of passive converter and active scintillator) Phase 2: NeuLAND (  t ~ 100 ps,  x,y,z ~ 1cm,  n > 90%) – wall of RPC (Resistive Plate Chambers) detectors Th. Blaich et al., NIM A314 (1992) 136 Target recoil,  -ray and slow neutron detector ESPA (EXL Silicon Particle Array) –  E-E system in Ultra High Vacuum EGPA (EXL Gamma and Particle Array) – Scintillators ELENA (EXL Low Energy Neutron Array) ~ half a million electronics channels to instrument! ESPA EGPA EXL/R 3 B demonstrator First step towards the realisation of the full recoil and gamma detectors in the NESR vacuum chamber. The demonstrator represents a key element of the combined ESPA and EGPA arrays (~ 300 channels) located at about 90° relative to the beam direction: 2 DSSDs and Si(Li) in vacuum (10 -7 mbar) Module of 15 CsI crystals outside vacuum UHV compatible feedthroughs VME-based electronics outside vacuum in first phase (2008) FR4 boards with AMS electronics inside vacuum chamber (2009) In-beam tests at KVI: proton beam at 45 and 150 MeV, 100 p/s Test Experiment at the ESR: Elastic proton-Xenon cross-section measured at very small momentum transfer. In-ring heavy-ion spectrometer Ion-optical mode for NESR as fragment spectrometer 3 heavy-ion detector (DSSD) stations for tagging, tracking and possibly imaging Experimental Setup: 136 Xe beam, 350 MeV/u H 2 gas jet target Luminosity ~ 6 x 10 27 cm -2 s -1 Single sided Silicon strip detector in Ultra High Vacuum (UHV) Slow neutron detector Fast neutron and proton detector Forward heavy ion detector S. Ilieva, O. Kiselev, H. Moeini et al., GSI, Uni. Basel, Uni. Mainz, KVI, Uni. Liverpool EXL opens a window onto neutron stars The neutron star (NS) structure is governed by the equation of state (EoS) of nuclear matter. NS properties are closely related to the structure of neutron rich nuclei. The universality of the EXL system makes it possible to study some parameters of the EoS. The neutron skin of a heavy nucleus constrains the density dependence of the symmetry energy, while systematics of the isoscalar Giant Monopole Resonance in heavy nuclei should fix the compression modulus of symmetric nuclear matter. Elastic proton-Xenon cross-sections as a function of 4-momentum transfer squared t. Solid squares represent experimental data and hollow squares the data corrected for 7.5 mm target size compared to theoretical predictions (solid line). ESR NESR