Research at FSU, using RESOLUT facility Development of and research with two new detector-systems

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1 Nuclear Astrophysics and Structure Research with Radioactive Beams Research at FSU, using RESOLUT facility Development of and research with two new detector-systems ResoNeut: Low-energy neutron detector-array ANASEN: Active target detector system Experiments with the (d,n) reaction to study proton-resonance nucleosynthesis Experiments with (d,p) reaction for orbital spectroscopy of exotic nuclei Experiments with (α,p) reaction for x-ray burst nucleosynthesis Experiment for Big-bang nucleosynthesis Detectors and programs for FRIB

2 RESOLUT: a radioactive beam facility at FSU Magnetic Spectrograph Solenoid 2 RF-Resonator Magnetic Spectrograph Mass selection slits Solenoid 1 Target Position RF-Resonator Experiment In-flight production of radioactive beams in inverse kinematics, Li(d,3He) 6He MeV ~1 104 pps (40% pure) 7 Li(p,n) 7Be MeV ~2 105 pps (80% pure) 7 Li(d,p)8Li MeV ~5 104 pps (90% pure) 7 Li(3He,n)8B MeV ~1 104 pps (10% pure) 7 Li(3He,n)10N MeV ~1 103 pps (10% pure) 18 O(d,n)17F 80 MeV ~2 105 pps (80% pure) 18 O(d,p)19O 95 MeV ~5 104 pps (90% pure) 18 O(3He,n)18Ne 70 MeV ~2 104 pps (25% pure) 24 Mg(d,n)25Al 98 MeV ~2 104 pps (35% pure) Beams can be purified off-line by tracking / rf-correlations 7 Production target

3 How to develop (d,n)-reaction as a surrogate for (p,γ) Q-value -2.2 MeV at proton threshold for all nuclei It is good for l=0 p-transfer to low-lying p-resonances l=0: neutron-yield is at backward angles, low energies kev E c m = 4 M e V /u E DWBA calculation (d,n) reaction E l= E E l= E E l= E E

4 First Generation experimental Setup

5 Al(d,n) Al(d,n)26Si-> 25Al + p, Grad. Student J. Baker 25 Observe three resonances 380(40) kev (40) kev 2+/ (40) kev cross sections (2) mb (4) mb (4) mb Coincident Recoil detection: low efficiency, but same states observed Compare to 422, 950, 1266 kev resonances from Matic et al. (p,t) experiment Counts / 50 kev

6 Simulation: (d,n) in inverse kinematics RESONEUT n kev Al 25 CD2 25 cm Beam: 25Al, 4 MeV/u, 2*104 pps Target: CD2, 0.2 mg/cm2 ResoNeut with 12 detectors, 50 kev threshold total efficiency <600 kev: ~10 % resolution: ~80 kev Expect 5 ev/h for 380 kev 26Si resonance

7 The ResoNeut Setup Optimized for (d,n) experiments studying astrophysical rp-process resonances Array of 12 para-terphenyl scintillators with <60 kev n-threshold and γ / n discrimination 8 detectors from NSF MRI (RUI) to U. North Florida +20 NaI detectors +DSSD-telescopes +Recoil Ion-chamber (J. Blackmon, C. Deibel, LSU)

8 Detector-performance: (n/γ (n/γ) discrimination Gated integration pulse-shape analysis 5ns / 25 ns charge-ratio (x-axis) vs charge (y-axis) Neutrons (left) 60 kev separated almost down to threshold Add X-ray absorbers for total separation

9 First results: 24Mg(d,n) Sean Kuvin, Jessica Baker Test experiment for the 25Al(d,n) Left: protons decaying from 2 resonances Right: Neutrons in coincidence with 790 kev peak Efficiency of detectors ~70% of simulation

10 Next experiments with ResoNeut F(d,n)18Ne Measure angular distribution, compare to 3+ resonance to ORNL (p,γ); additional resonances? Thesis-experiment Sean Kuvin Al(d,n)26Si Measure cross section, resonance energies Thesis-experiment Jessica Baker P(d,n)30S, compare to spectrum (3+) (2+), (3-) K. Setoodehnia et al. PRC C 82, (R) (2010), measured with (p,t) at Yale Alg(d,n)27Si, compare to 188 kev measured (p,γ) at TRIUMF, others resonances Alm(d,n)27Si, compare to spectrum 445, 627 kev resonances, established using (p,t) at Yale Deibel et al. Phys. Rev. C 80, (2009)

11 ANASEN Concept Array for Nuclear Astrophysics Studies with Exotic Nuclei Extended active gas target/detector Cylindrical proportional counter surrounding beam axis 19 anodes 7µm diam carbon fiber High Gain Target gas =Detector gas p RIB ---> Beam enters through window recoil Light charged particles detected by Si+CsI E in PC particle identification 2. Position Si + Position PC lab 3. Energy Si + lab Ecm Entire excitation function simultaneously measured

12 (α,p) studies: e.g. 18Ne(α Ne(α,p)21Na Ne(,p)21Na at LLN 18 Indirect studies: e.g. 24Mg(p,t)22Mg Matic et al., PRC (2009). 30 MeV Ni (2 mg/cm2) 18Ne 0.2 mg/cm2 Au Groombridge et al., PRC (2002). 0.5 atm He E 67 m (48x48) 0.3 mm pitch 21 Na(p, )18Negs Up to 25x smaller than Groombridge p TRIIUMF-Edinburgh Collab (TUDA) Salter et al., PRL (2012). E E1 E2 E 470 m (16x16) 3 mm pitch Large discrepancies/uncertainties Only upper limits below Ecm=1.7 MeV Statistical model reliability questionable

13 He(14N,p)17O with ANASEN 4 Stable beam test of (,p) approach Configuration same as for 6He+ Stable 14N beam from FSU tandem at 30 MeV (Ecm=6.7 MeV) He gas (1% CO2) 350 Torr E-E particle ID p LSU Graduate Student Kevin Macon J.C. Blackmon

14 F excitation function measured with ANASEN 18 ΔEcm(FWHM) as small as 70 kev 6 hr of data <106 ions/s Forward detectors Resolution slightly worse in rings J.C. Blackmon Middle Ring Next: Analyzing 18 Ne(,p)21Na Measured with RESOLUT at FSU (Ecm+4.4MeV)

15 Nuclear Astrophysics program at FSU The RIB program at FSU is used for measurement in resonant reactions of exotic nuclei. Surrogate (d,n) reactions for (p,γ) Direct measurments of (α,p) using thick, active target detector ANASEN Detector development: RESONEUT, ANASEN Synergy with Split-pole spectrograph program Connection to ReA-3