ELectron-Ion Scattering in a
Storage Ring (eA collider) - ELISe

Spokesperson: H.Simon (H.Simon@gsi.de | WWW)
Deputy: L.V. Chulkov (L.Chulkov@gsi.de)

Schematic view of the proposed electron LINAC with its small storage ring within the NESR (New Experimental Storage Ring)

The planned international accelerator facility at the GSI laboratory at Darmstadt will provide intense, high-quality secondary beams [1] of ions and antiprotons. The basic features of the facility are described in the conceptual design report [2]. A new double synchrotron ring system will provide 10¹² ions/s up to uranium with an energy of 1.5 GeV/u. Intense, secondary ion beams will be produced and separated with the Super-FRS [3]. A system of storage-cooler rings will be used to reduce the emittance and energy spread of secondary beams created via fragmentation or fission reactions. Scattering experiments at internal targets are being planned in the New Experimental Storage Ring (NESR) with radioactive ions at energies up to 740 MeV/u. Additionally, an intersecting electron ion ring (eA collider, [4]) will allow to scatter electrons with an energy of 125-500 MeV off exotic nuclei [5-9]. The eA collider will enable for the first time to perform elastic, inelastic and quasielastic electron scattering off shortlived radioactive isotopes. The collider kinematics has the advantage that it will be possible to detect electrons and target like ejectile in coincidence. One of the most challenging aspects in this context is the design of a high-resolution electron spectrometer [10,11] with large acceptance adapted to the specific demands of an in-ring experiment. Charge distributions, transition form factors in giant resonance or electrofission experiments and spectral functions can be measured with a clean electromagnetic probe.

[1] FAIR web pages
[2] Conceptual Design Report
[3] H. Geissel et al., Nucl. Inst. Meth. B204(2003)71
[4] I.A. Koop et al., BINP-GSI Report 2001
[5] NUSTAR/ELISe - Letter of Intent
[6] NUSTAR/ELISe - Technical Proposal [20050115]
[7] NUSTAR/ELISe - Technical Proposal [20051215]
[8] NUSTAR/ELISe - Baseline Technical Report (2006)
[9] The electron-ion scattering experiment ELISe at the International Facility for Antiproton and Ion Research (FAIR)-A conceptual design study
Nucl. Inst. Meth. A637 (2011) 60-76
[doi:10.1016/j.nima.2010.12.246]
[10] A novel spectrometer for studying excotic nuclei with the electron/ion collider ELISe
Nucl. Inst. Meth. A640 (2011) 123-132
[doi:10.1016/j.nima.2011.02.025]
[11] Constant gap spectrometer design for the Electron/Ion Collider ELISe
Nucl. Inst. Meth. A, in press
[doi:10.1016/j.nima.2011.06.081]