Inves&ga&on of neutron- rich isotopes: Understanding the r process

Transcription

1 Canada s national laboratory for particle and nuclear physics Laboratoire national canadien pour la recherche en physique nucléaire et en physique des particules Inves&ga&on of neutron- rich isotopes: Iris Dillmann Research Scientist Nuclear Astrophysics TRIUMF Accelerating Science for Canada Un accélérateur de la démarche scientifique canadienne Owned and operated as a joint venture by a consortium of Canadian universities via a contribution through the National Research Council Canada Propriété d un consortium d universités canadiennes, géré en co-entreprise à partir d une contribution administrée par le Conseil national de recherches Canada

2 11 Greatest Unanswered Questions of Physics 2

3 Heavy element nucleosynthesis N = N s + N r + N p Burbidge, Burbidge, Fowler, Hoyle, Revs. Mod. Phys. 29 (1957) 3

4 r-process residuals N r = N - N s N=50 Rare Earth Peak measured well- known Local abundance maxima (and minima) are mirrors of nuclear structure Astrophysical scenario s&ll debated 4

5 Open questions Core collapse supernova? T 1 GK (n,γ)- (γ,n) equilibrium Hot r- process Credit: Hubble Space Telescope Neutron star mergers? T< 0.5 GK liyle photodissocia&on equilibrium β- decays and (n,γ) Cold r- process Credit: Daniel Price (U/Exeter) and Stephan Rosswog (Int. U/Bremen). November 14th, 2013 Inves&ga&on of neutron- rich isotopes: R. Surman 5

6 Nuclear physics input Masses: define reac&on path Half- lives: define shape Shell structure far off stabilty: define posi&on of abundance peaks Neutrons from β- delayed neutron emission or (γ,n): smoothing of abundance curve Need experimental informa&on for isotopes between reac&on path and stability! 6

7 Neutron-rich ISAC ISAC- I: TITAN: Masses GRIFFIN ( ): Decay spectroscopy, Half- lives 3Hen (2014)/ BELEN ( ): β- delayed neutron branching ra&os, half- lives ISAC- II: TIGRESS: In- beam spectroscopy, reac&ons, transi&on rates IRIS, EMMA: (d,p) reac&ons 7

8 Neutron detector setups at TRIUMF 3Hen (Oak Ridge, 2014) BELEN- 48 (Barcelona/ Valencia/ Madrid/ GSI Darmstadt, >2017) 3He long counters En= ev - 2 (5) MeV εn up to 70 % DESCANT (commissioning 2013/14) Canadian funded (CFI) project November 14th, deuterated scin&llators En= 100's kev - 10 MeV Combina&on with GRIFFIN: ε 15 % Inves&ga&on of neutron- rich isotopes: Understanding the r process 8

9 β-delayed neutron emission Important nuclear structure informa&on: Time- dependence of n- emission t 1/2 ( A Z) few ms s ( 87 Br) S n Emission probability P n : β- strength above S n For new isotopes: fastest (easiest?) access to first nuclear proper&es Q β S n < Q β 9

10 βn measurements at TRIUMF β- n( γ) coincidences 3Hen/ BELEN (β ) n γ coincidences GRIFFIN & DESCANT (β )γ γ coincidences GRIFFIN 10

11 Influence on r-process nucleosynthesis Produc&on of addi&onal neutrons: influence on n/seed ra&o at later &mes A. Arcones and G. Mar&nez- Pinedo, PRC83, (2011) November 14th, 2013 Abundance peaks shi5ed R. Surman, M. Mumpower, in prepara&on Inves&ga&on of neutron- rich isotopes: Smoothing of abundance curve Forma&on of Rare- Earth peak Shik of abundance peaks Recent measurements show higher branching ra&os than predicted more neutrons released 11

12 βn database Large discrepancy: need reliable data as basis for ARIEL and other facili&es November 14th, 2013 Inves&ga&on of neutron- rich isotopes: 12

13 IAEA Coordinated Research Project I. Dillmann A.B. Garnsworthy P.E. GarreY C.E. Svensson A. Chen B. Singh Evalua&on of βn- emiyers: half- lives, P n values New TRIUMF: 3Hen, BELEN, GRIFFIN, DESCANT 13

14 Going more neutron-rich βn- emission will become dominant process β- delayed 2- / 3- neutron emiyers Shorter- lived nuclei November 14th, 2013 Inves&ga&on of neutron- rich isotopes: 14

15 Photofission at ARIEL Photo- fission on UC x - target Advantages of photofission: Higher yields around fission peaks Less isobaric contamina&ons 15

16 Summary Nuclear physics measurements will be essen&al to answer the long- standing ques&on of the astrophysical site(s) of the r- process(es) Accurate n- branching ra&os and half- life measurements are needed for the understanding of the solar r- abun- dance distribu&on and to constrain theore&cal models TRIUMF program is part of a 5- year IAEA Coordinated Research Project with measurements + evalua&ons ARIEL beams are essen&al for future r- process program and will enable unique, more neutron- rich research Experimental setups already available 16

17 Canada s national laboratory for particle and nuclear physics Laboratoire national canadien pour la recherche en physique nucléaire et en physique des particules Thank you! TRIUMF: Alberta British Columbia Calgary Carleton Guelph Manitoba McMaster Montréal Northern British Columbia Queen s Regina Saint Mary s Simon Fraser Toronto Victoria Winnipeg York Merci Owned and operated as a joint venture by a consortium of Canadian universities via a contribution through the National Research Council Canada Propriété d un consortium d universités canadiennes, géré en co-entreprise à partir d une contribution administrée par le Conseil national de recherches Canada

18 Backup Slides 18

19 Constrain theory N= 50 N= 50 Nuclear physics input for r- process calcula&ons: Theory + few experimental informa&on N= 82 N= 82 Extrapola&ons into the "Terra Incognita": - A= : few mass units - A>150: mass units N= 126 No data! N= 126 Factors 5-10 difference between models Q. Zhi et al., Phys. Rev. C 87, (2013) November 14th, 2013 Inves&ga&on of neutron- rich isotopes: 19

20 Present yields (September 2013) Picture: P. Kunz (TRIUMF) 20

21 Proton-induced spallation 21

22 Photo-fission 22