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ACTAR

ACTAR. Gas – target and working gas of the detector. Low momentum transfers, Short-lived isotopes. ● Elastic (p,p ' ) scattering in inverse kinematics (for nuclei with T 1/2 < 1 s) – ground-state matter distributions ● (3He,t) charge exchange reactions – Gamow-Teller resonances

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ACTAR

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  1. ACTAR Gas – target and working gas of the detector. Low momentum transfers, Short-lived isotopes. ● Elastic (p,p') scattering in inverse kinematics (for nuclei with T1/2 < 1 s) – ground-state matter distributions ● (3He,t) charge exchange reactions – Gamow-Teller resonances ● (α,α') inelastic scattering – ISGM resonances, nuclear matter compressibility PNPI

  2. TPC at PSI IKAR at GSI

  3. Proton elastic scattering at intermediate energy is an efficient tool to study nuclear matter distributions. Previously, the method was successfully used in studies of nuclear matter density distributions in stable nuclei. An advantage of this method: There exists a good multiple-scattering theory of Glauber, which allows one to connect the measured differential cross sections with the density distributions under study. The input in the calculations of the differential cross sections: 1 – elementary nucleon-nucleon amplitudes of free scattering; 2 – phenomenological nuclear density distributions under study.

  4. Scattering from the halo is confined to small scattering angles (small momentum transfers). 2 – contribution to the cross section of the proton scattering from the core. 1 – the cross section including contributions of the scattering from the core and halo. The study of proton scattering at small momentum transfers allows one to determine both sizes of the core and halo (G.D. Alkhazov and A.A. Lobodenko, Pis’ma Zh. Eksp. Teor. Fiz. 55, (1992)).

  5. Sensitivity of the cross sections to the halo structure matter radius Rm - slope of dσ/dt Rm = 2.70 fm Rm = 2.80 fm Rm = 2.90 fm Rm = 2.70 fm Rm = 2.80 fm Rm = 2.90 fm halo structure - curvature of dσ/dt with halo without halo Rm = 2.80 fm with halo without halo Rm = 2.80 fm

  6. Experimental set-up at GSI Darmstadt. IKAR is an ionization chamber (target and proton recoil detector) developed at PNPI. PC1-PC4 – tracking system. ALADIN is the magnet to measure the ejectile momentum.

  7. ACTAR IKAR

  8. IKAR at GSI

  9. p4,6,8He cross sections p6,8,9,11Li cross sections

  10. The same cross sections divided by exponents The t-dependence of the p4,6He, p6,8,9Li cross sections is close to that of an exponential function. The t-dependence of the p8He, p11Li cross section is not consistent with an exponent.

  11. 6He : Rp =Rc=1.88(12) fm, Rh= 3.32(31) fm, Rn= 2.70(20) fm, Rm=2.45(10) fm. 8He : Rp=Rc=1.55(15) fm, Rh=3.21(10) fm, Rn= 2.77(8) fm, Rm=2.53(8) fm. L.B. Wang et al., Phys. Rev. Lett. 93 (2004). Laser spectroscopy experiment: Rp(6He)=1.91(2) fm.

  12. 8,9,11Li matter densities 8He matter density

  13. p14Be cross section 14Be matter distribution Rrms = 3.11 ± 0.14 fm

  14. p12Be cross section 12Be matter distribution Rrms = 2.82 ± 0.12 fm

  15. First step: IKAR chamber It is necessary to exclude a contribution from ionization by the projectile Grid recoiled proton 132Sn beam Cathode Anode A correction on the energy lost in the central dead region

  16. Farouk Aksouh Multiple Coulomb scattering of the projectile: δθs ~ Z/A < 1 mrad. Δx ≈ 1 mm θs < 0.5 mrad Azimuth angle ? – segmented anode p = 10 bar, p = 1 bar. 0.002 < t < 0.01 (GeV/c)2 Ep < 5 MeV σtot ≈ 600 mb (in previous exp. – 60 mb) Detail simulations are needed ROSATOM 1238 k€

  17. Thank you for attention

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