-ray detector CATANA for E1 response of neutron-rich nuclei Tokyo - PowerPoint PPT Presentation

γ -ray detector CATANA for E1 response of neutron-rich nuclei Tokyo Institute of Technology Yasuhiro Togano 10 March, ELPH calorimeter workshop

E1 response of n-rich nuclei nuclei B(E1) strength Pygmy: Ex~10 MeV Giant: Ex~80A -1/3 MeV ~5% of TRK sum ~100% of TRK sum Sn Light ( γ ) Excitation energy [MeV] • Giant dipole resonance (GDR): all stable nuclei • Pygmy dipole resonance (PDR): n-rich nuclei ( 208 Pb, 132 Sn etc…) • Oscillation of neutron skin? • EOS of neutron matter → neutron star • Structure is not yet known

Measurements of PDR N=82 D. Savran et al., Prog. Part. Nucl. Phys. 70, 210 (2013). Z=50 Z=40 Z=28 Z=20

Measurements of PDR N=82 D. Savran et al., Prog. Part. Nucl. Phys. 70, 210 (2013). Z=50 Z=40 Z=28 Z=20 Measurement of PDR in 48,50,52 Ca@RIBF Di fg erence of Fermi surface

Experimental procedure E γ 1 E rel 51 Ca β ~0.6 virtual photon absorption E γ 2 E γ 1 52 Ca n E γ 2 52 Ca 51 Ca+ n S n Pb 52 Ca ~2% γ branch 52 Ca 52 Ca E γ E γ 52 Ca Pb 52 Ca

Experimental setup CATANA n CsI(Na) array 51 Ca 52 Ca 250 MeV/nucleon in 2016

CATANA • CAesium iodide array for γ -ray Transitions in Atomic Nuclei at high isospin Asymmetry • Crystal: CsI(Na), 20 crystals per ring • High e ffj ciency: ~60% for 1 MeV gamma Beam

Structure of CATANA • Doppler shift & Lorentz boost • • Forward focus 9 cm t 15 cm t 20 cm θ 40 cm Angular resolution: ~9 deg

CATANA の結晶 • CsI(Na) • Better time response • Fit PMT’s spectral response • hygroscopic: housing

Supporting frame Beam

Supporting frame

R11265 R580 R580 R11265 PMT • R11265 • Length: 3.5 cm: less space • Metal package ← magnetic field • B-field@SAMURAI target area • 30 G R580 R11265 Cathode e fg ective 34 mm Φ 23 area Photocathode Bialkali Super Bialkali material Number of 10 12 dynodes 1.1 1 Gain 3 nA 0.4 nA Dark current Rise / Transit 2.7 / 37 ns 0.6 / 5.1 ns time

Test of prototypes Position: light collection e ffj ciency 1275 keV 511 keV Calorimetric property � � polished � Etched surface etched

channel Test of prototypes Response to 8.99 MeV γ ray polyethylene 10 x 20 mm 2 blue: w Ni plate red: w/o Ni plate 252 Cf Ni plate 58 Ni + n 8.99 MeV 59 Ni

Schedule • ~Mar. 2015: Design of supporting frames • ~Dec. 2015: 100 crystals • Apr. 2016?:Measurement of E1 response in 48,50,52 Ca by combining NaI(Tl) and LaBr3

Summary • New γ -ray detector array CATANA • CATANA + SAMURAI → E1 response of n-rich nuclei. • Prototype test: finished • Ca experiment: April 2016?