Post on 10-Feb-2021
transcript
Spectroscopic Study of 39Ca for Classical Nova Endpoint
Nucleosynthesis
Johnson Liang
McMaster University
Overview
● General goals● Astrophysics background+motivation● Experimental setup● Data analysis● Preliminary results
General goal
● Correctly model and understand the nucleosynthesis in a classical nova
● Predict the abundances of elements produced in a classical nova and match it to observations
Classical Nova
● White dwarf (WD) in binary with hydrogen rich star
● WD siphons material from companion star
Classical Nova
● White dwarf (WD) in binary with hydrogen rich star
● WD siphons material from companion star
● Layer of nuclear fuel forms on surface
● Degenerate material cannot expand – thermonuclear runaway ensues
Classical Nova Nucleosynthesis
● Nucleosynthesis pathway, endpoint A~40
Denissenkov et. al., MNRAS 442 3, 2014
Understanding Classical Novae
● Discrepancy between predicted abundances and observed abundances of ejecta
Important Nuclear Inputs
● [1] Iliadis et. al, Astrophys. J. Suppl. Ser. 142 (2002) 105.
● Nuclear reaction rates play a large role in abundances of ejecta
● Sensitivity study [1] shows that varying 38K(p,g)39Ca reaction rate by it’s uncertainty (factor of 100 up, 100 down) changes abundances of:
– 38Ar by a factor of 25– 39K by a factor of 136– 40Ca by a factor of 58
Understanding Classical Novae
● Discrepancy between predicted abundances and observed abundances of ejecta
● Need better nuclear reaction parameters: Reaction cross section/rate
+
38K(p,g)39Ca reaction rate
Proton 38K 39Ca
● Dependent on resonant reactions in the Gamow window
● Need energy levels of 39Ca
+
38K(p,g)39Ca reaction rate
Proton 38K 39Ca
39Ca Energy Levels
39Ca
+
38K(p,g)39Ca reaction rate
Proton 38K 39Ca
1/2+ 3+
● L = 0 transfer reactions are strongest
39Ca Energy Levels
39Ca
Most Recent Direct Measurement
● 38K(p,g)39Ca measured using DRAGON at TRIUMF [2]
● Measured resonance strengths of important resonances in 39Ca (in keV):
– 6157(10)– 6286(10)– 6451(2)
● [2] Lotay et al. Phys. Rev. Lett. 116 (2016) 132701
Most Recent Direct Measurement
● Measured using DRAGON at TRIUMF [2]● Measured resonance strengths of important
resonances in 39Ca (in keV):
– 6157(10)– 6286(10)– 6451(2)
● Able to measure the resonance strength in the 6451(2) state and obtain upper limits of others.
● Reduced uncertainty in rate of 38K(p,g)39Ca● [2] Lotay et al. Phys. Rev. Lett. 116 (2016) 132701
Understanding Classical Novae
● Discrepancy between predicted abundances and observed abundances of ejecta
● To measure reaction rate, need precise resonance energies of 39Ca
● Need better nuclear reaction parameters: Reaction cross section/rate
Experiment : 40Ca (d,t) 39Ca
● Goal: Measure resonances using the 40Ca(d,t)39Ca reaction
● Beam energy: 22 MeV
Experiment : 40Ca (d,t) 39Ca
● Goal: Measure resonances using the 40Ca(d,t)39Ca reaction
● Beam energy: 22 MeV● 2 Targets used:
– CaF2 production target
● 30 μg/cm2 CaF2 on 10 μg/cm2 enriched 12C foil
– 32S calibration target● 11.7 μg/cm2 32S implanted in 40 μg/cm2 enriched
12C foil
● Experiment was done at the MaierLeibnitz Laboratory (MLL) in Munich, Germany
● 14 MV MPTandem and Quadrupole 3x Dipole Magnetic Spectrograph (Q3D)
Figure: MP Tandem in Munich (source: http://www.pro-physik.de/Phy/Images/News/ TUM_Tandem_350.jpg)
Q3D Setup
Quadrupole Magnet
Focuses in the verticalDefocuses in the horizontal
Q3D Setup
Dipole Magnets
*Separates reaction products by momentum to charge ratio on the focal plane
Q3D Setup
Focal Plane
● Problem: How do we separate different species of particles?
Detectors
Direction of Recoils
Direction of Recoils
Detectors
Direction of Recoils
Detectors
Particle Identification
● Plot energy losses: E (xaxis) , ΔE (yaxis).
Particle Identification
● Select particles of interest (tritons)
Position Spectrum
● Cathode strip detector● 255 strips, each 3.5 mm wide
(Preliminary) Position Spectrum
● Plot position (energy) vs. Counts
Excitation Energy in 39Ca
32S Target Calibration Spectrum
● 31S position spectrum
● Focal plane simulation
● Convert Position axis to energy of residual nucleus
● Plot position (energy) vs. Counts
6161 keV6475 keV
6299 keV
(Preliminary) Position Spectrum
Excitation Energy in 39Ca
Comparison with Previous values
EX 15 degrees
(keV)
EX 20 degrees
(keV)
EX 25 degrees
(keV)
EX 30 degrees
(keV)
EX NNDC (keV)
6471(5) 6475(2) 6474(2) 6475(3) 6451(2)
6302(1) 6299(1) 6302(2) 6286(10)6162(2) 6161.3(7) 6162(3) 6159.5(6) 6157(10)
● Statistical error only● Preliminary*
Summary
● Nuclear reaction rates are important in modeling classical novae
● Nuclear reaction rates depend on resonance energies within the Gamow window
● Methodology of instruments at the MLL Q3D● 40Ca(d,t)39Ca preliminary results look to be self
consistent
Acknowledgments
McMaster University
A. Chen, J. Liang, A. Psaltis
NSCL/MSU Department of Physics and Astronomy
C. Fry, P. Tiwari, C. Wrede
Technical University of Munich
M. Anger, S. Bishop, T. Faestermann, D. Seiler
LudwigMaximiliansUniversität München
R. Hertenberger, H. Wirth
Fitting
Fitting
Fitting
Experiment : 40Ca (d,t) 39Ca
● Goal: Measure resonances using the 40Ca(d,t)39Ca reaction
● Choice of beam energy: 22 MeV
– QValue to GS: 9.386 MeV (Endothermic)– Energy state desired: 6.4 MeV– Coulomb barrier: 4.4 MeV– Total: 20.686 MeV
Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40