From ESR to NESR: the EXL experiment at FAIR

C. Rigollet - KVI, University of Groningen for the EXL collaboration

The EXL collaboration

Universität Basel, SwitzerlandBirmingham University, UK

CLRC Daresbury Laboratory, UKTU Darmstadt, Germany

GSI, Darmstadt, GermanyInstitute of Nuclear Research, Debrecen, Hungary

Joint Institute of Nuclear Research, Dubna, RussiaEdinburgh University, UK

Universität Frankfurt, GermanyPNPI, Gatchina, and St. Petersburg State University Russia

Chalmers Institute, Göteborg, SwedenKVI, University of Groningen, the Netherlands

University of Surrey, Guildford, UKForschungszentrum Jülich, Germany

SINP, Kolkata, IndiaUniversity of Liverpool, UK

Lund University, SwedenCSIC, Madrid, Spain

Universidad Complutense, Madrid, SpainJohannes Gutenberg Universität, Mainz, Germany

Universitá da Milano/INFN, Milan, ItalyRussian Research Centre, Kurchakov Institute, Moscow, Russia

Bhabha Atomic Research Centre, Mumbai, IndiaTU München, Munich, Germany

IPN Orsay, FranceOsaka University, Japan

V.G. Khlopin Radium Institute, St. Petersburg, RussiaUniversidade de São Paulo, São Paulo, Brasil

Mid Sweden University, Sundsvall, SwedenUniversity 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 coveragewill 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 VacuumEGPA (EXL Gamma and Particle Array) – ScintillatorsELENA (EXL Low Energy Neutron Array)

~ half a million electronics channels to instrument!

ESPA

EGPA

EXL/R3B 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:

• 136Xe beam, 350 MeV/u• H2 gas jet target• Luminosity ~ 6 x 1027 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) structureis 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 systemmakes 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