1 / 23

Measurement of 4 He( 12 C, 16 O) g reaction in Inverse Kinematics

Measurement of 4 He( 12 C, 16 O) g reaction in Inverse Kinematics. Kunihiro FUJITA K. Sagara , T. Teranishi , M. Iwasaki, D. Kodama, S. Liu, S. Matsuda, T. Mitsuzumi , J.Y. Moon, M.T. Rosary and H. Yamaguchi Department of Physics, Kyushu University, Japan

kyrie
Download Presentation

Measurement of 4 He( 12 C, 16 O) g reaction in Inverse Kinematics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Measurement of 4He(12C,16O)greaction in Inverse Kinematics Kunihiro FUJITA K. Sagara, T. Teranishi, M. Iwasaki, D. Kodama, S. Liu, S. Matsuda, T. Mitsuzumi, J.Y. Moon, M.T. Rosary and H. Yamaguchi Department of Physics, Kyushu University, Japan Kyushu University Tandem Laboratory (KUTL)

  2. Evolution of Stars He-burning 3 4He → 12C 4He+12C → 16O+g H-burning 4p → 4He via p-p chain & CNO cycle 12C/16O abundance is determined → affects all of the posterior processes C-burning O-burning Si-burning

  3. Introduction 12C/ 16O ratio after helium burning process evolution of heavy stars – supernova or white dwarf? abundance of element of universe Cross Section of 4He(12C,16O)g very small (~10-8nb) – coulomb barrier varies drastically around stellar energy(0.3MeV) Extrapolation with experimental data our experiment ( 10% accuracy) E1 E2 extrapolation stellar energy

  4. 16O measurement 4He beam + g measurement 16N decay measurement direct 16O measurement with 12C beam and 4He target high efficiency (~ 40%: charge fraction) total S-factor can be obtained necessary components for Ecm=0.7MeV experiment background separation system: NBG/N12C ratio of 10-19 thick gas target : ~25 Torr x 3 cm high intensity beam: ~ 10 pmA Y(16O) ~ 5 counts/day → 1 month experiment for 10% error Cross section (S=const.) 10-5 10-5

  5. Experimental Setup Layout of Kyushu University Tandem Laboratory (KUTL) Tandem Accelerator chopper buncher Blow in windowless 4He gas target 12C beam RMS 12C Sputter ion source Recoil Mass Separator (RMS) Tandem Long-time chopper Final focal plane (mass separation) Ecm = 2.4~0.7 MeV E(12C)=9.6~2.8 MeV E(16O)=7.2~2.1 MeV 16O Detector (Si-SSD)

  6. Windowless Gas Target 3000 l/s 520 l/s 330 l/s DP TMP3 MBP1 RMS beam TMP4 TMP2 TMP5 MBP2 TMP1 520 l/s 350 l/s 520 l/s 330 l/s 1500 l/s • Blow-In Gas Target (BIGT) • windowless & high confinement capability 24 Torr beam SSD: beam monitor Differential pumping system (side view) 4.5cm • center pressure: 24 Torr - post stripper is not necessary • effective length: 3.98 0.12 cm (measured by p+a elastic scattering) • → target thickness is sufficient for our experiment • (limited by energy loss of 12C beam)

  7. BG Reduction and 16O Detection Recoil Mass Separator 12C/16O separation : ratio of 10-11 angular acceptance: 1.9deg 100% 16O can be observed Background 12C charge exchange multiple scattering Background reduction RF deflector (Long-Time Chopper) background reduction ~10-3 movable slits combination with trajectory analysis v dispersion m dispersion

  8. Ecm=1.5 MeV experiment beam: 12C1+, frequency: 3.620MHz energy: 6.0MeV, intensity: 60pnA • target: 4He gas 15.0 Torr x 3.98 cm • observable: 16O3+, 4.5 ± 0.3 MeV • abundance = 40.9 ± 2.1 % = efficiency 95 hours data 16O 208 counts

  9. Charge State Distribution of 16O • Charge state after gas target • 16O has different charge state • Our target is very thick • Equilibrium charge distribution was measured • Comparison with theoretical calculation

  10. Cross Section and S-factor 2.4MeV: 1.5MeV: Background ratio NBG/N12C = 10-16 Next experiment is Ecm=1.20 MeV , 2010 stellar energy Our data (2009, 2010) D. Schurmann et al. Eur. Phys. J. A 26, 301-305 (2005) future plan

  11. Development of Ionization Chamber • BG reduction by 10-3 is necessary for Ecm=0.7MeV measurement Particle Identification by E-DE information →Ionization Chamber • Gas: PR-Gas, 10~30 Torr • Effective area: 40Hx40Wx50tmm2 • Entrance Window: PET foil, 0.5mm, f45mm • Voltage: • Cathode: GND, Grid: 100V, Anode: 150V • Timing resolution of1ns is necessary → install Si-SSD at the end 50mm SSD particle cathode PET foil 40mm f45mm frish grid anode 50mm

  12. Performance test by 12C+a • Test experiment by Ecm=1.5MeV setting • 6.0MeV, 12C beam: ~100nA • Pilot 16O - spontaneity generating from tandem acc. DE [MeV] 16O projection 12C Total E [MeV] DE [MeV] • 16O(4.5MeV) and12C(3~6MeV)was separated by the ratio of 10-3(99.9%) • Energy resolution of Ionization Chamber wasDE/E=9%(FWHM)

  13. Test Experiment of Ecm=1.2MeV • Update of Tandem acc. ~Accelerate Decelerate mode • successfully incremented for beam intensity • Beam: 4.8MeV(1.2MV), 12C2+ • Observable: 3.6MeV, 16O3+ 5 hours data

  14. Summary Direct 16O measurement via 4He(12C,16O)g reaction was proposed to determine 12C/16O abundance ratio in stars Blow-in type windowless gas target was developed, and thickness of 24 Torr x 3.98 cm was achieved Background reduction was performed by using RMS, RF-deflector and movable slits Ecm= 2.4 MeV experiment s= 64.6nb, S-factor = 89.0keV b Ecm= 1.5 MeV experiment s= 0.900nb, S-factor = 26.6keV b Now we start measurement at Ecm=1.2MeV

  15. BACKUP

  16. Charge State Fraction of 16O Our data W. Liu et al. / Nucl. Instr. and Meth. A 496 (2003) 198–214

  17. f1=6.1MHz V1=±24.7kV f2=3×f1 V2=V1/9 V3=23.7kV RF-Deflector (Long Time Chopper) pass only reaction products (16O) which are spread in time. reject BG + pass reaction products Flat-bottom voltage BG(12C) 16O5+ 500events

  18. Trajectory Analysis 12C backgrounds were rejected by slit control based on trajectory analysis slits 12C3+ 6.0MeV 16O3+4.5MeV (Ecm=1.5MeV) ED D1 D2 v dispersion final focal plane (detector) target 12C2+ 3.0MeV

  19. Ecm=2.4MeV experiment beam: 12C2+, frequency: 6.063MHz energy: 9.6MeV , intensity: ~35pnA target: 4He gas ~ 23.9 Torr x 3.98 cm observable: 16O5+ 7.2 ± 0.3 MeV abundance = 36.9 ± 2.1 % = efficiency 29hours data 941 counts 16O

  20. Development of Ionization Chamber • BG reduction by 10-3 is necessary for Ecm=0.7MeV measurement • Additional electric deflector? Or Wien-Filter? → difficult due to space boundary • Upgrade detector DE information by Ionization Chamber 16O (4.5MeV) DE [MeV] Simulation plot of E-DE Ar Gas: 20Torrx5cm 12C (1~6MeV) Total E [MeV]

  21. Resolution of Ionization Chamber Ionization Chamber • Measurement of 16O+12Celastic scattering • Beam: 16O2+, 9.6MeV • Target: 12C(7 mg/cm2) 12C,16O • Detector setting • PR-gas: 20 Torr • Cathode: -150V, Grid: -50V 16Obeam θ 7μg/cm2 C-foil 45.0° 37.5° DE [ch] 16O: 4.75MeV 12C: 5.91MeV 12C: 4.70MeV • Clearly separated for 16O(4.75MeV) and 12C(4.7MeV) • Energy Resolution: DE/E=6%(FWHM) Total E [ch]

  22. Normal operation of tandem accelerator. Accel-decel operation of tandem accelerator. By alternative focus-defocus, Focusing becomes strong, and Beam transmission increases. At low acceleration voltage, focusing becomes weak, and beam transmission decreases.

  23. accel-decel operation normal operation Al shorting bars for accel-decel operation By the accel-decel operation, ・10 times higher beam transmission is obtained by strong focusing. ・17.5 times more intense beam can be injected, due to higher electric power necessary for accel-decel operation. By a large aperture (12f) gas stripper, spread in beam energy and angle is decreased, and beam transport to the target is ~3 times increased. Totally, beam intensity is 300-500 times increased.

More Related