Determina)on of astrophysical thermonuclear rates with a bubble chamber: The 12C(α,γ)16O reac)on case
Claudio Ugalde, for
12C(α,γ)16O Reac5on Key reac)on for nucleosynthesis in massive stars, progenitors of Type Ia SN, WD ages.
Affects the synthesis of most of the elements of the periodic table
Sets the C to O ra)o in the universe
Determines the minimum mass a star requires to become a core collapse supernova
Determines whether for a given ini)al mass, a star will become a black hole or a neutron star
Affects the constraints on the age of stellar popula)ons from White Dwarfs
The varia)on of the C/O ra)o in the progenitor might be a cause of the varia)on of SNIa brightness
However, σ ~ 1 x 10-‐17 barns at astrophysical temperatures.
Rolfs and Rodney, 1988
S(300)
Kunz 2001, Matei 2006
Yield ~ N1N2σg
0 < g < 1 g = ε *(1-‐bkgd/signal)
€
NA συ = NA8
πµ kT( )3σ E( )
0
∞
∫ E exp − EkT(
) *
+
, - dE
N1
N2 From experiments
Yield
Kunz 2001 (Stu_gart)
• 4 MV Dynamitron, 480 µA 4He beam • 12C implanted targets on gold substrate • 4 large HPGe, with ac)ve BGO shield
Ec.m. = 0.95 -‐ 2.80 MeV
α + 12C --> 16O + γ beam target signal
N1= 2x1018 Carbon implanted par)cles N2= 0.5 mA = 3.12 x 1015 α-‐par)cles/s in 1 year (Gamow window) N1 N2 = 1.97 x 1041 Yield = 2 events in one year
Experiment record Kunz et al. 2001 (100% error bar)
σ ~ 1 x 10-‐17 barn He burning
Yield ~ N1N2σg
12C
α
16O
γ
New approach: Inverse reac5on + Bubble chamber + γ ray beam
γ + 16O --> 12C + α beam target signal
Monochroma)c γ beam from HIγS ~ 107-‐8 γ/s Bremsstrahlung from JLab ~ 1010-‐12 γ/s
H2O bubble chamber
• Extra gain (x100) by measuring )me inverse reac)on • The target density up to x106 higher than conven)onal targets. • Superheated water will nucleate from α and 12C recoils • The detector is insensi)ve to γ-‐rays (at least 1 part in 1011) • Prototype tested at HIγS
(STAR) Claudio Ugalde 10
Acceptance window size is tunable by varying P and T (amount of superheat)
C4F10
Ranges in water
Δt = 10 ms
(STAR) Claudio Ugalde 13
Superhea)ng of liquids Water
(STAR) Claudio Ugalde 14
Superhea)ng of liquids Water
Very challenging engineering
Test feasibility with a liquid requiring
technical simplicity (C4F10)
(STAR) Claudio Ugalde 15
HIγS Photon Beam
E (electron) ~ 500 MeV +
2 x10-‐10 torr vacuum
Strong bremsstrahlung background component
γ-‐ray beam @ 8.7 -‐ 10.0 MeV
Counted for ~1 hr per data point
Experiment performed in two 12 hour sessions
Proof of principle: as predicted, photodisintegra5on does induce nuclea5on
• Event distribu5on from 1 hour of beam. • 2% of events appear outside the beam region. • No surface nuclea5on problems.
To keep the bubble chamber count rate at 0.1Hz levels, the beam intensity had to be reduced from 1x107 to 5x103 γ/s.
Ugalde et al. 2013
15N(α,γ0)19F
Bremsstrahlung beams at Jefferson Lab
CEBAF 12 GeV
Injector
(STAR) Claudio Ugalde 19
(STAR) Claudio Ugalde 20
Bremsstrahlung radiator + collimator
Geant 4. Courtesy of A. El Alaoui
electrons
First water experiment HIγS Scheduled April 2013
Kunz 2001 N1= 2x1018 Carbon implanted par)cles N2= 0.5 mA = 3.12 x 1015 α-‐par)cles/s in 1 year N1 N2 = 1.97 x 1041 Yield = 2 events in one year
Outlook 10 years
Kunz 2001 N1= 2x1018 Carbon implanted par)cles N2= 0.5 mA = 3.12 x 1015 α-‐par)cles/s in 1 year N1 N2 = 1.97 x 1041 Yield = 2 events in one year
LUNA-‐MV (Gran Sasso) N1= 2x1018 Carbon implanted par)cles N2= 0.5 mA = 3.12 x 1015 α-‐par)cles/s in 1 year N1 N2 = 1.97 x 1041 Yield = 2 events in one year
Outlook 10 years
Kunz 2001 N1= 2x1018 Carbon implanted par)cles N2= 0.5 mA = 3.12 x 1015 α-‐par)cles/s in 1 year N1 N2 = 1.97 x 1041 Yield = 2 events in one year
DIANA + JENSA (DUSEL) N1= 1x1019 helium par)cles gas target N2= 10 mA =6.24 x 1016 carbon part/s in 1 year N1 N2 = 1.97 x 1043 Yield = 200 events in one year
LUNA-‐MV (Gran Sasso) N1= 2x1018 Carbon implanted par)cles N2= 0.5 mA = 3.12 x 1015 α-‐par)cles/s in 1 year N1 N2 = 1.97 x 1041 Yield = 2 events in one year
Outlook 10 years
Kunz 2001 N1= 2x1018 Carbon implanted par)cles N2= 0.5 mA = 3.12 x 1015 α-‐par)cles/s in 1 year N1 N2 = 1.97 x 1041 Yield = 2 events in one year
DIANA + JENSA (DUSEL) N1= 1x1019 helium par)cles gas target N2= 10 mA =6.24 x 1016 carbon part/s in 1 year N1 N2 = 1.97 x 1043 Yield = 200 events in one year
Bubble + HIγS2 N1= 3.35x1023 par)cles in liquid target N2= 2 x 1010 γ/s in 1 year N1 N2 = 2.11 x 1041 Reciprocity -‐> x100 Yield = 200 events in one year
LUNA-‐MV (Gran Sasso) N1= 2x1018 Carbon implanted par)cles N2= 0.5 mA = 3.12 x 1015 α-‐par)cles/s in 1 year N1 N2 = 1.97 x 1041 Yield = 2 events in one year
Outlook 10 years
Next genera)on light sources
ELI-‐NP, Romania 2015
Phase 1 Very intense (1013 γ/s), brilliant γ-‐ray beam, 0.1 % bandwidth, with E= 19 MeV Phase 2 (2018-‐2020) -‐> 1015 γ/s
V. Zamfir 2011
Bubble + ELI-‐NP (Phase 1) N1= 3.35x1023 par)cles in liquid target N2= 1 x 1013 γ/s in 1 year N1 N2 = 2.11 x 1044 Reciprocity -‐> x100 Yield = 200,000 events in one year
Conclusions We completed both the first test of the prototype of the bubble chamber detector and the characteriza5on of the main sources of background for the experiments. We have provided a proof of principle of opera5on as a low rate counter and proposed a scheme for higher count rates. The thin glass vessel appears to be the best design for a water-‐based bubble chamber. Bremsstrahlung from the electrons in the ring manifests mainly as neutrons. Par5cle ID would help separa5ng these events from the α-‐par5cle + heavy ion signal. A Bremsstrahlung beam scheme with low energy electrons would solve the problem. In the long run, the success of the project will depend on beam intensity, the level of deple5on of water, and par5cle ID.
Top Related