Physics opportunities with the AT-TPC D. Bazin NSCL/MSU at ReA - PowerPoint PPT Presentation

Physics opportunities with the AT-TPC D. Bazin NSCL/MSU at ReA

Reaction studies at ReA ❖ Radioactive beams are used in inverse kinematics ❖ Target is now the (usually light) probe nucleus ❖ Scattered particles have low energies ❖ Beam intensities are small (from 1 to 10 8 pps) ❖ High luminosity needed: large acceptances, thick targets ❖ New types of instruments needed ❖ Active Target Time Projection Chamber (AT-TPC) ❖ Gas is both target and detector medium: thick target without loss of resolution ❖ Vertex determination, virtually 4 π angular coverage, very low energy threshold ❖ Excitation functions from beam slow down and vertex determination D. Bazin, ReA3 upgrade workshop, August 20, 2015

AT-TPC physics program at ReA ❖ Resonant scattering for nuclear cluster structure studies ❖ Inverse kinematics proton scattering for single-particle structure studies via IAS population ❖ Fusion cross sections with neutron-rich isotopes below the Coulomb barrier ❖ Inverse kinematics transfer reactions for single-particle structure such as (d,p), (p,d), (p,t), ( 3 He,d), … ❖ Excitation functions of reactions of astrophysical interest such as ( α ,p) for instance ❖ Exotic radioactive decays (3 α decay from 12 C Hoyle state, 2p radioactivity, …) ❖ ReA3 upgrade is crucial to access the full potential of these reaction tools D. Bazin, ReA3 upgrade workshop, August 20, 2015

Principle of operation Insulator ¡gas ¡volume ¡(N 2 ) Field ¡shaping ¡rings Cathode: ¡-­‑ ¡100 ¡kVDC ¡(1kV/cm) Pad ¡plane ¡and ¡ electron ¡ amplifica$on ¡ e -­‑ e -­‑ e -­‑ e -­‑ e -­‑ device ¡ (Micromegas) e -­‑ e -­‑ e -­‑ e -­‑ e -­‑ e -­‑ e -­‑ Beam e -­‑ d l fi e Posi%on ¡ ¡ i c t r c e E l -­‑>(x, ¡y) Ac$ve ¡gas ¡volume ¡ z > ¡ ¡ -­‑ e m % 1 ¡ i D r He, ¡H 2 , ¡D 2 ¡… D. Bazin, ReA3 upgrade workshop, August 20, 2015

AT-TPC setup ❖ Straight and tilted (7°) Yoke configurations ❖ Tilt relative to beam axis to increase accuracy for TPC Beam small angles ❖ Placed inside 2 Tesla solenoid (increase range and measure Brho) ❖ 250 liters (1 m by 55 cm) active volume ❖ Financed by NSF-MRI D. Bazin, ReA3 upgrade workshop, August 20, 2015

Pad plane and electronics ❖ 10,240 triangular pads ❖ Central region density x4 for small angle scattering ❖ GET (General Electronics for TPC) ❖ Digital readout instrumentation of each pad ❖ Internal trigger generation using multiplicity signals ❖ Data filtering (partial readout, zero suppression, …) D. Bazin, ReA3 upgrade workshop, August 20, 2015

Visualization of nuclear reactions in 3D ❖ Last commissioning in December 2014 ❖ Beam: 4 He at 3 MeV/u ❖ Target: He(90%) + CO 2 (10%) @ 100 Torr ❖ Magnetic field: 2 Tesla ❖ Event displays ❖ Right: hit pattern on pad plane, orange region is trigger exclusion zone ❖ Top left: integrated time projection ❖ Bottom left: 3D reconstruction of event D. Bazin, ReA3 upgrade workshop, August 20, 2015

Prototype AT-TPC D. Bazin, ReA3 upgrade workshop, August 20, 2015

Prototype AT-TPC Scattering 6 He + α at Twinsol • 2000 pps 6 He • Confirm strong α -cluster state in 10 Be. Suzuki et al. PRC 2013 D. Bazin, ReA3 upgrade workshop, August 20, 2015

Prototype AT-TPC Scattering 6 He + α at Twinsol • 2000 pps 6 He • Confirm strong α -cluster state in 10 Be. Fusion 10 Be + P10 (Ar/Methane) • Sub-barrier fusion with low-intensity RIBs. (200 cps) J. Kolata A. Howard Suzuki et al. PRC 2013 (Notre Dame) D. Bazin, ReA3 upgrade workshop, August 20, 2015

Cluster states in 14 C ❖ Resonant scattering of 4 MeV/u 90 90 10 80 10 Be 10 Be beam (TWINSOL) on 4 He 70 5 Radius [cm] 60 60 θ ( 10 Be,lab) 10 Be θ ( 10 Be) 50 0 θ ( α ) 40 ❖ Observed 2 + and 4 + resonances 30 30 α -5 0 + 20 match linear chain calculations -10 10 2 + 0 0 0 30 60 90 (AMD) Time [µs] 0 10 20 30 40 50 60 70 80 90 40 0 θ ( α ,lab) ❖ A. Fritsch et al., submitted to PRC 10 60 A B + E c.m. [MeV] 40 A - 4 - 9 5 5 + 50 2 (III) triaxially deformed [mb/sr] - - - 3 7 5 8 ρ p ρ n ρ p - ρ n [MeV] 40 30 8 4 + 7 4 + [1/fm 3 ] 6 2 + 4 6 30 5 + 2 + 6 + Ω 20 2 0 + c.m. 4 + 4 + 5 0 d (IV) linear chain 20 3 + / -2 2 + 4 + E σ 4 0 + -4 10 2 + d 2 + 10 -6 3 0 + -8 2 0 0 (I) (II) (III) (IV) 40 40 60 60 80 100 120 140 80 100 120 140 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 10 [degree] E [MeV] θ c.m. c.m. D. Bazin, ReA3 upgrade workshop, August 20, 2015

Proton scattering to IAS resonances ❖ Evolution of neutron orbitals in A Z can be studied via the A Z(d,p) A+1 Z transfer reaction or by populating T > analog states of A+1 Z in A+1 Z+1 via the A Z(p,p’) reaction ❖ Spectroscopic factors for excited states in A+1 Z can be deduced reliably from cross sections of resonances observed in A+1 Z+1 D. Bazin, ReA3 upgrade workshop, August 20, 2015

Inverse kinematics in AT-TPC ❖ 40 Ar beam from ReA3 at 4.5 MeV/u ❖ Gas target: 20 Torr of C 4 H 10 ❖ Excitation function from incident energy to 0 (beam stopped) ❖ Next experiment: 46 Ar at 4.2 MeV/u from ReA3 + CCF (9/2015) ❖ Higher beam energies would allow reaching higher energy states D. Bazin, ReA3 upgrade workshop, August 20, 2015

Inverse kinematics in AT-TPC ❖ 40 Ar beam from ReA3 at 4.5 MeV/u ❖ Gas target: 20 Torr of C 4 H 10 ❖ Excitation function from incident energy to 0 (beam stopped) ❖ Next experiment: 46 Ar at 4.2 MeV/u from ReA3 + CCF (9/2015) ❖ Higher beam energies would allow reaching higher energy states D. Bazin, ReA3 upgrade workshop, August 20, 2015

Transfer reactions ❖ ReA3 energies too low for most cases (Q-value, momentum matching) ❖ AT-TPC can provide highest luminosity, can detect both light and heavy particles with close to 4 π coverage and good resolution ❖ Elastic cross section of entrance channel measured simultaneously ❖ H 2 and D 2 gas targets can be made significantly thicker than CH 2 and CD 2 foils ❖ Reaction energy known for each event (vertex), allows to sum angular distributions measured at different energies D. Bazin, ReA3 upgrade workshop, August 20, 2015

Example: 38 S(d,p) ❖ Study shell quenching between N=20 and N=28 below the Z=20 closure ❖ Simulations show 200 keV resolution achievable D. Bazin, ReA3 upgrade workshop, August 20, 2015

Example: 38 S(d,p) ❖ Study shell quenching between N=20 and N=28 below the Z=20 38 S(d,p) 6 closure 5 f 7/2 5 MeV/u 4 f 7/2 4 MeV/u ❖ Simulations show 200 keV f 7/2 3 MeV/u Cross section (mb/sr) 3 resolution achievable f 7/2 2 MeV/u ❖ Angular distributions from 2 different energies can be cumulated 1 9 8 7 6 0 100 200 300 400 Θ c.m. x √ E D. Bazin, ReA3 upgrade workshop, August 20, 2015

Example: 38 S(d,p) ❖ Study shell quenching between N=20 and N=28 below the Z=20 38 S(d,p) 6 closure 5 f 7/2 5 MeV/u 4 f 7/2 4 MeV/u ❖ Simulations show 200 keV f 7/2 3 MeV/u Cross section (mb/sr) 3 resolution achievable f 7/2 2 MeV/u ❖ Angular distributions from 2 different energies can be cumulated ❖ Meaningful experiments can be 1 9 achieved with only 1,000 pps! 8 7 6 0 100 200 300 400 Θ c.m. x √ E D. Bazin, ReA3 upgrade workshop, August 20, 2015

Example: 38 S(d,p) ❖ Study shell quenching between N=20 and N=28 below the Z=20 38 S(d,p) 6 closure 5 f 7/2 5 MeV/u 4 f 7/2 4 MeV/u ❖ Simulations show 200 keV f 7/2 3 MeV/u Cross section (mb/sr) 3 resolution achievable f 7/2 2 MeV/u ❖ Angular distributions from 2 different energies can be cumulated ❖ Meaningful experiments can be 1 9 achieved with only 1,000 pps! 8 7 ❖ Energy should be 10-12 MeV/u! 6 Needs ReA12! 0 100 200 300 400 Θ c.m. x √ E D. Bazin, ReA3 upgrade workshop, August 20, 2015

Outlook ❖ ReA3 upgrade to energy range 10-15 MeV/u would open great opportunities for experiments with the AT-TPC ❖ The AT-TPC can provide high luminosity without compromising resolution ❖ This is paramount because of the low intensities of re- accelerated radioactive beams ❖ Simple transfer reactions such as (d,p), (p,d), (d, 3 He) are of particular interest D. Bazin, ReA3 upgrade workshop, August 20, 2015

AT-TPC collaboration ❖ NSCL team ❖ D. Bazin, W. Mittig, W. Lynch, S. Beceiro-Novo, Y. Ayyad, J. Bradt, L. Carpenter, J. Manfredi, S. Rost, M. Cortesi, J. Yurkon ❖ Other institutions ❖ T. Ahn, J. Kolata, Z. Chajecki, D. Suzuki, U. Garg, R. Kanungo D. Bazin, ReA3 upgrade workshop, August 20, 2015