Soft collective excitations in weakly bound nuclei studied with ELI-NP A.Krasznahorkay Inst. of Nuclear Research of the Hung. Acad. of Sci. (ATOMKI)

ELI Attosecond Light Pulse Source 1)To generate X-UV and X-ray fs and atto pulses, … ATTOSECOND section 2)To contribute to the technological development towards 200PW… High-intensity section

1.High resolution study of the soft dipole resonances 2.Determination of the strengths of the pigmy dipole resonances

Grand Raiden with complete dispersion matching techniques. The relative energy resolution is the best in the world (ΔE/E ≈ ). The spectrometer was set at 0° and 2.5° with an opening angle of ±20 mrad horizontally and ±20 mrad vertically defined by a slit at the entrance of the spectrometer. Research Center for Nuclear Physics (RCNP), Osaka University. ( 3 He,t) charge exchange reaction. 400 MeV 3 He on 40 Ca, 42 Ca, 44 Ca and 48 Ca targets. Previus experiment

We determined the precise level energies for each isotopes and deduced their intensities by fitting the energy spectra. Identification of new excited states Energy (MeV) Counts

0 -,1 -, , E*=7096 keV E*=1404 keV Angular distributions (deg.)

Low-lying dipole strengths

Super fluid vibrations? Alpha condensate? B. Cederwall et al., Nature 469, (2011) Nature 469, (2011)

RPA calculations The theoretical description (RPA of the distribution is in progress (Elena Litvinova, GSI)

Theoretical description (RPA) Elena Litvinova, GSI

Comparison of the experimental and theoretical results

A new step with ELI-NP Pure electromagnetic probe for exciting exclusively the dipole strengths γ-beam combined with the chrystal spectrometer (GAMS4 from ILL Grenoble) Ultimately high energy resolution (ppm) allows to measure the natural widths (Γ) of the levels and determine the absolute strengths for a large number of transitions for the first time! A new experimental window will be opened to discover new phenomena in nuclear structure physics!

Constraining the symmetry energy of the EoS by precise neutron-skin thickness measurements Accepted SIS18 experiment (S408), Spokeperson: A. Krasznahorkay Furnstahl, Nucl. Phys. A706 (2002) 85

The symmetry energy in nuclear matter

Dipole strengths exited in (p,n) reactions in inverse kinematics

Study of pigmy resonances Constraints on the symmetry energy and neutron skins from pygmy resonances in 68 Ni and 132 Sn (PRC 81, (R) (2010)) S(ρ)| ρ=ρ0 = L/3ρ 0

Experimental requirements High resolution (10 -6 ) tunable photon beam Detectors with very high counting rate capabilities Flesh ADCs with high (1-2 GHz) sampling rate Good collimators and very well shielded beam dump

The GAMS4 flat crystal facility (E.G. Keller et al., NIM A457 (2001) 187.) Michael Jentschel

Advantages of LaBr 3 scintillators Best energy resolution Fast emission High count rate capabilities Excellent radiation hardness Wavelength of emission max. [nm] 380 Primary decay time [ns] 16 Light yield [% of NaI(Tl)] (for γ-rays) 165 M. Ciemala., … A. Krasznahorkay et al., NIM A608 (2009) 76. Fast anti-coincidence shield is needed to get better response at high energy !!!

Energy resolution and efficiency Typical time resolution: 250 ps (for large detectors) Spacial resolution <80 cm !!! Scattered background could be reduced

Experimental arrangement E7 8x8 m E8 5x8 m GAMS 4 3x4 m Shilded beam dump 4 pcs of 3”x3” AC LaBr 2 detectors Cost estimates for detectors: 4x40 k€ + acquisition system: ~ 40 k€

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