Slide 1

CYCLOTRON INSTITUTE Nuclear reactions - experiment for nuclear structure, reaction mechanisms and nuclear astrophysics Livius Trache l-trache@tamu.edu Cyclotron Institute, Texas A&M University and Institute for Physics and Nuclear Engineering Bucharest, Romania Exotic Beam Summer School 2012 ANL Aug 5-10, 2012 l-trache@tamu.edu Slide 2 CYCLOTRON INSTITUTE Summary 1.Introduction Nuclear reactions: vocabulary/definitions 2.Rare Isotope Beams RIB production RIB reaction specifics 3.Types of reactions a)Elastic scattering b)Inelastic scattering c)Direct reactions: one nucleon transfer, few nucleons d)Breakup at intermediate energies e)Resonant elastic scattering TTIK method f)In-flight decay spectroscopy g)multifragmentation 4.Instrumentation 5.Applications to Nuclear Astrophysics Slide 3 CYCLOTRON INSTITUTE Nuclear reactions Reactions are basic tools to study nuclei (nuclear structure) and nuclear forces Other tools: Mass measurements Decay studies Measurement at lab energies Comparison with (reaction) calculations Extract (nuclear structure) information Need good additional knowledge (data). Reliable absolute values 1 Slide 4 Nuclear reactions Projectile + target -> reaction product(s)+ r. residue(s) Scattering: 1+2-> 1+2 Two-body reactions: 1+2 ->3*+4* Multifragmentation r: 1+2 -> 3+4+5+ Kinematic conditions: incident energy, scattering (react) angle Normal kinematics: Mp Mt E lab -> E cm = (Mt/(Mp+Mt))E lab (non-relativistic) Measure cross section: =nr detected/incident p per area/nr target nuclei Spectra: =f(Q fi ) (reveal states of quantum system(s)) Angular distributions: d /d = f( ) (info on space charact of inter region) Excitation functions: =f(E inc ) (info on time charact of interaction) Momentum distributions (info on size) + projectile target detector Residue (recoil) product beforeafter 4 Slide 5 CYCLOTRON INSTITUTE Typical measurements 21 Na(p,p) 21 Na Energy spectrum: 13 C( 14 N, 13 C) 14 NAngular distribution 13 C( 7 Li, 8 Li) 12 C Excitation fct: =f(E inc )Momentum distrib: d /dp 23 Al-> 22 Mg+p Slide 6 CYCLOTRON INSTITUTE 2. Exotic nuclear Beams EB or RIB (Rare Isotope Beams) RIB production ISOL technique: prod by reactions -> separation -> reacceleration In-flight: reaction prod separated -> secondary beams Fragmentation reactions (E/A> 25-50 MeV/u) Reactions in inverse kinematics (fusion-evaporation, direct reactions) RIB specifics Lower intensities Stable beams: 1-100 pnA => 10 9 10 11 pps RIB: 1-10 7 pps Lower resolutions: energy, angle Large background Imply: Detectors w higher efficiency (4 coverage?!) Clean data with coincidences ( -part, part-part, etc) Beam identification Full kinematics reconstruction New instruments, new experimental methods 6 Slide 7 CYCLOTRON INSTITUTE 3.Types of reactions a)Elastic scattering b)Inelastic scattering c)Direct reactions: one nucleon transfer, few nucleons d)Breakup at intermediate energies e)Resonant elastic scattering TTIK method f)In-flight decay spectroscopy g)Multifragmentation 3 Slide 8 1+21+2 Elastic scattering: no energy transf to internal excit good, sensitive probe of surface and (sometimes!) of interior of nuclei Angular distributions measured on a large range: small angles probe surface Larger angles probe more toward interior Described with Optical Model Potentials (OMP) Phenomenological Semi-microscopic: double folding Figura Di Pietro here Excitation function reveal resonances in CN 8 Elastic scattering 3 a) Slide 9 CYCLOTRON INSTITUTE Elastic scattering, if well understood and used, can give important information about the structure of the two partners and about the reaction mechanism. Example (by A. Bonaccorso) for 9,10,11 Be on 64 Zn. From A di Pietro et al, PRL 2010. Elastic scattering is used to extract Optical Model Potentials needed in DWBA 9 FIG. 1: Color on line. Elastic-scattering angular distributions on 64 Zn: 9 Be(triangles), 10 Be (diamonds) and 11 Be (squares). The lines represent the OM calculations for 9 Be(dot dashed), 10 Be (dashed) and 11 Be (full line). The inset shows the mea- sured AD (symbols) and OM fit (full line) for the 11 Be+ 64 Zn system together with the result of the OM calculation for the inelastic excitation of 11 Be( 1/2 , Ex=0.32 MeV) (dashed line). Slide 10 CYCLOTRON INSTITUTE OMP: wide systematics loosely bound stable p-shell nuclei 10 Slide 11 CYCLOTRON INSTITUTE Semi-microscopic double folding potentials for nucleus-nucleus collisions HFB densities (to best match the surfaces) tried various effective interactions (M3Y, DDM3Y, JLM, etc) Settled for JLM Smearing w. range parameters t V =1.2 fm, t W =1. 75 fm Renormalizations needed N v, N w JLM - uses eff inter of Jeukenne, Lejeune and Mahaux (PRC 16, 1977) n-nucleus Bauge ea (PRC 58, 1998): energy and density dependent independent geometry for real and imaginary potentials normalization independent of partners reproduce ELASTIC and TRANSFER data Checked for loosely bound p-shell nuclei stable beams ~ 10 MeV/u Found N v =0.37(2) N w =1.0(1), t V =1.20 fm, t W =1. 75 fm Extended to RNB: 7 Be, 8 B, 11 C, 12 N, 13 N, 17 F on 12 C, 14 N targets Double folding procedure: 11 Slide 12 CYCLOTRON INSTITUTE Works for transfer reactions JLM works for a range of energies E/A=15-50 MeV/u JLM works for elastic & transfer 12 Slide 13 CYCLOTRON INSTITUTE 13 7 Be on melamine TAMU exps @ 12 MeV/u ORNL exps @ 10 MeV/u G. Tabacaru ea, PRC 73, 025808 (2006) J. Blackmon ea, PRC 73, 034606 (2005) A. Banu ea, PRC 79, 2009. Optical Model Potentials for Nucleus-Nucleus collisions for RNBs Essential to make credible DWBA calc needed in transfer studies Have established semi-microscopic double folding using JLM effective interaction: Established from exps with stable loosely bound p-shell nuclei: 6,7 Li, 10 B, 13 C, 14 N @ 10 MeV/u Independent real and imaginary parts, energy and density depend. Parameters: renormalization coeff. (Nv~0.4-0.5, Nw=1.0) Predicts well elastic scatt for RNBs: 7 Be, 8 B, 11 C, 12 N, 13 N, 17 F Good results for transfer reactions (tested where possible) L. Trache ea, PRC 61 (2000) F. Carstoiu ea, PRC 70 (2004) F. Carstoiu & LT, PRC 85 (2012) 12 N on melamine Slide 14 3 b Inelastic scattering 1+2 -> 1+2* Selective to collective excitations Quadrupole excitations E2: 0 + 2 + Octupole excitations E3: 0 + 3 - Extract B(E2), B(E3) actually G IS (L=2,3) Slide 15 Transfer and nucleon-removal reactions Give information about the single particle (fermionic) degrees of freedom in nuclei Single nucleon transfer Multinucleon transfer Alpha transfer measure angular distributions Determine: njl, spec factor, ANC Pair transfer info on pairing vibrations = collective mode Breakup (nucleon-removal) at intermediate energies: measure momentum distributions Determine: njl, spec factor, ANC 3 c,d Slide 16 Spectroscopic factors and ANCs Spectroscopic factors definition ANC Overlap integrals I A Bp and their asympt behavior For transfer: For break-up: C 2 nlj =S nlj *b 2 nlj, where b nlj is the s.p. ANC With (some) assumptions, we get, for major comp. and one-step: Slide 17 CYCLOTRON INSTITUTE As used in shell model calculations Slide 18 CYCLOTRON INSTITUTE Spectroscopic factors and ANCs Spectroscopic factors definition ANC Overlap integrals I A Bp and their asympt behavior For transfer: For break-up: C 2 nlj =S nlj *b 2 nlj, where b nlj is the s.p. ANC With (some) assumptions, we get, for major comp. and one-step: Slide 19 CYCLOTRON INSTITUTE 19 ANC in peripheral reactions: radiative proton capture, transfer and breakup Shape in asymptotic region given by Whittaker fct. Only normalization (ANC) unknown and needed! (p, ) happens here transfer happens here breakup happens here Slide 20 20 c) Transfer reactions: the ANC method Transfer reaction B+dA+a peripheral (absorption) Transfer matrix element: NA: proton-nucleus also peripheral ANC - independent on binding potential geometry! OMP knowledge crucial for reliable absolute values! Semi-micr proc. JLM interaction (LT ea, PRC, 2000) (Christy and Duck, 1963 Parker and Tombrello, 1964) Depend on geom (r 0,a) of proton-binding potential < 20-40% Depend on OMP * n Factors !!! Slide 21 CYCLOTRON INSTITUTE 21 From MARS group at Texas A&M University Transfer reactions. Major results: ANC technique firmly established for transfer reactions Proton transfer for radiative proton capture in Nucl Astrophysics 7 Be(p, 11 C(p, ) 12 N, 12 N(p, ) 13 O, 13 N(p, ) 14 O, 9 Be(p, ) 10 B, 13 C(p, ) 14 N, 14 N(p, ) 15 O, 15 N(p, ) 16 O Use of neutron transfer and mirror symmetry for ANC proposed and tested: ( 7 Li, 8 Li) for ( 7 Be, 8 B) 7 Be(p, ) 8 B ( S 17 ) ( 22 Ne, 23 Ne) for ( 22 Mg, 23 Al) 22 Mg(p, ) 23 Al ( 17 O, 18 O) for ( 17 F, 18 Ne) 17 F(p, ) 18 Ne Optical Model Potentials for nucleus-nucleus collisions from double-folding procedure using JLM eff inter. Needed in DWBA. Established with stable beams and tested for RNBs: 7 Be, 8 B, 11 C, 12 N, 13 N, 17 F, Slide 22 CYCLOTRON INSTITUTE 22 Cross sections for (p, ) from p-transfer reactions with RNB from MARS 12 C N Melamine target (Faraday Cup) E-det. (PSSD) Er-det. 12 C N Melamine target (Faraday Cup) E-det. (PSSD). 12 C @23 MeV/u H 2 cryotarget 12 N @12 MeV/u 99% pure, 4 mm dia Melamine target Four telescope system (the cross): E PSD 65, 110 m E 500 m Slide 23 CYCLOTRON INSTITUTE 23 Example 12 N @12 MeV on N 6 C 3 H 6 and C Primary beam: 12 C @ 23 MeV/u 150 pnA Secondary beam: 12 N @12 MeV/u 2x10 5 pps Elastic cm =8-60 deg. Fit OMP from folding JLM no param adjust! Transfer 14 N( 12 N, 13 O) 13 C fit w. DWBA extract ANC 12 N(p, ) 13 O rate evaluated from ANC C 2 p1/2 ( 13 O g.s.)=2.530.30 fm -1 Slide 24 CYCLOTRON INSTITUTE 24 Transfer & elastic @12 MeV/u TAMU MARS 12 N beam 2 10 5 pps 14 N( 12 N, 13 O) proton-transfer react 12 N(p, ) 13 O (rap proc) A. Banu et al, Phys Rev C 79, 025805 (2009) ANC, S-factor 0-2 MeV Reaction rate dependence on the geometry of proton binding potential (r 0,a) b nlj Slide 25 CYCLOTRON INSTITUTE 25 Neutron transfer 14 N( 7 Li, 8 Li) 13 C Study mirror reaction neutron transfer with stable beam to obtain information on 8 Li Use charge symmetry 8 Li - 8 B Results: C 2 tot ( 8 B)= 0.455 0.047 fm -1 & Mixing ratio C 2 (p 1/2 )/C 2 (p 3/2 )=0.13(2) LT e.a., PRC 67, June 2003 Slide 26 CYCLOTRON INSTITUTE 26 Problem: 14 C(n, ) 15 C Slide 27 CYCLOTRON INSTITUTE 27 Slide 28 CYCLOTRON INSTITUTE MDM spectrometer Raytrace reconstruction allows good angular resolution (~0.2 deg) with a Large angle covering 4 deg (lab) 28 Slide 29 CYCLOTRON INSTITUTE 29 Slide 30 CYCLOTRON INSTITUTE TECSA d( 14 C,p) 15 C results BT Roeder et al, NIM A634 (2011)71 30 Slide 31 CYCLOTRON INSTITUTE 31 Slide 32 CYCLOTRON INSTITUTE Results 14 C(n, ) 15 C 32 ANC 14 C(n, ) 15 C exp-theory Matthew McCleskey, thesis, TAMU, Aug 2011 14 C+ 13 C elastic Slide 33 CYCLOTRON INSTITUTE 33 Breakup (one-nucleon removal r.) Momentum distributions nlj Cross section ANC (only!!!) Gamma rays config mixing Need: V p-target & V core-target and reaction mechanism Calc: F. Carstoiu; Data: see later 3 d Slide 34 CYCLOTRON INSTITUTE 34 One-nucleon removal = spectroscopic tool Example of momentum distributions all types! E. Sauvan et al. PRC 69, 044503 (2004). Cocktail beam: 12-15 B, 14- 18 C, 17-21 N, 19-23 O, 22-25 F @ 43-68 MeV/nucleon. normal halo 2s 1/2 Config mixing Slide 35 CYCLOTRON INSTITUTE 35 Example: Summary of the ANC extracted from 8 B breakup with different interactions Data from: F. Negoita et al, Phys Rev C 54, 1787 (1996) B. Blank et al, Nucl Phys A624, 242 (1997) D. Cortina-Gil e a, EuroPhys J. 10A, 49 (2001). R. E. Warner et al. BAPS 47, 59 (2002). J. Enders e.a., Phys Rev C 67, 064302 (2003) All available breakup cross sections on targets from C to Pb and energies 27-1000 MeV/u give consistent ANC values! Summary of results: LT ea, PRL 87, 2001 LT ea, PRC 67, 2004 Slide 36 CYCLOTRON INSTITUTE Calc w various effective interactions A. Glauber model with folded potentials 1) JLM -uses the G-matrix effective interaction of Jeukenne, Lejeune and Mahaux ( PRC 16, 1977) tested before because: independent geometry for imaginary part normalization independent of partners and energy reproduces ELASTIC and TRANSFER data for loosely bound p-shell nuclei with experimentally determined renormalizations ( 7 Be, 8 B, 11 C and 13 N on 12 C, 14 N) found no renorm for imaginary pot Nw=1.0 at 10 MeV/u. Assumed correct at all energies !!! 2) the free t-matrix NN interactions of Franey and Love (PRC 31, 1985) Slide 37 CYCLOTRON INSTITUTE Various effective interactions (contd) B. Glauber model calc in the optical limit Use three ranges for interactions, to check the sensitivity: 3) zero-range 0 4) standard =1.5 fm for all terms 5) Ray, ranges for each term, as determined by L. Ray (PRC 20, 1979) Test how the calculations reproduce other observables: reaction cross-sections (p, 7 Be and 8 B on a 12 C target) and total cross sections (p on 12 C). No new parameters!!! Slide 38 CYCLOTRON INSTITUTE 32 S primary beam 444 183 95 MeV/u, ~ 400 W MCP LDC Trifoil Gamma-ray detectors: 8 EXOGAM clovers 4% effic. 12 NaI crystals 6% effic. E491 exp. @ GANIL Cocktail beam (mid-target energies): 24 Si 53 MeV/u 23 Al 50 MeV/u 22 Mg 47 MeV/u 21 Na 43 MeV/u 20 Ne 39 MeV/u large angular acceptances: 4 (horiz. & vertic. planes) broad momentum acceptance: p/p = 7% A.Banu et al., NIC10 2008 & PRC 84, 015803 (2011) 38 Slide 39 CYCLOTRON INSTITUTE 39 23 Al 22 Mg+p Proton removal (sought) GANIL E491 exp 12 C( 22 Mg, 22 Na) 12 N Charge exchange (new & unexpected) Slide 40 CYCLOTRON INSTITUTE 40 Results from 23 Al breakup config. mixing of 23 Al ground state 4 2 + -> 4 1 + 1 2 + -> 0 + 4 1 + -> 2 + 22 Mg 0+ 2+ 41+41+ 42+42+ 1247 2061 1985 ( 23 Al)~200 MeV/c and J =5/2 + If b 2 is s.p. ANC: C 2 =b 2 exp / calc =3.90 0.44 10 3 fm 1 Slide 41 CYCLOTRON INSTITUTE 41 Complementarities: Coulomb and nuclear dissociation Similar results from mirror system: 22 Ne+n-> 23 Ne 13 C( 22 Ne, 23 Ne) 12 C n-transfer @12MeV/u assuming S n =S p Slide 42 CYCLOTRON INSTITUTE Results from 24 Si breakup C 2 ( 24 Si gs ) = 62.4 7.1 fm -1 SF = 2.5 -2.9 Note: exp made with 30 pps! 22 Mg(p, ) 23 Al(p, ) 24 Si seq. 2p capture imp in XRB A. Banu et al, PRC 85 (2012) Slide 43 43 Resonant elastic scattering: TTIK method Standard excitation functions: measure, change energy and measure again Thick Target Inverse Kinematics (TTIK) method: scattering on p gas =>measure the excitation function for elastic scattering (at 180 o ) in one single measurement. Can study the properties (level structure) of the compound nucleus 43 E in E in - E 1 E in - E 2 beam stops K.P.Artemov et al., Sov. J. Nucl. Phys. 52, 408 (1990) 3e Slide 44 (N,Z) Resonance scattering in the valley of stability and at the drip line Stable nucleus case Drip line nucleus case Level density is too high Too close to the threshold Cannot be populated in resonance scattering (N,Z-1)+p (N,Z) (N,Z-1)+p threshold 4 4 4 44 Slide 45 45 Motivation 14 F, 15 F are unbound; 2-3 nucleons beyond proton-dripline Have not been previously studied (difficult to access). Study of light, exotic nuclei provides a good test of ab-initio (NCSM) shell model calculations. Addition of a single nucleon can significantly change properties of a light nucleus (e.g. proton separation E) Search for 14,15 F with 13,14 O+p resonant elastic scattering. 19 F +7.9 18 O +15.9 17 O +13.8 16 O +12.1 16 F 0.54 18 F +5.6 17 F +0.6 15 O +7.3 14 O +4.6 14 F ? 13 O +1.5 20 Ne +12.8 19 Ne +6.4 18 Ne +3.9 17 Ne +1.5 16 Ne 1.4 12 O 1.8 15 F 1.5 Proton Dripline Black Stable Pink EC or + Decay Yellow p Decay Orange 2p Decay Slide 46 46 Experiments Search for 14,15 F 13 O beam ~ 5000 pps from p( 14 N, 13 O)2n (Q =-29.1 MeV). Purity 80%, main contaminants 10 C (10%), 8 B (4 %). 14 O beam ~ 10 4 pps from p( 14 N, 14 O)n Purity 80%, main contaminant 7 Be (20%). 30 MeV/u 13 O 80% pure 14 N Beam 38 MeV/u Slide 47 47 Experiment 13 O+p 14 F Figure : G.G. Chubarian 13 O beam from MARS; E in =149 MeV CH 4 pressure: 13.6 psi and 15.0 psi. 13 O beam stops in CH 4 gas, scatters protons. Check calibration with 14 O+p 15 F (measured before). Check/subtract carbon bkg. with 13 O+CO 2 13 O 14 F 15 F: V. Goldberg et al. PRC 69, 031302(R) (2004) 14 F: ibidem, PL B692, 307 (2010) TTIK method ( < 10 MeV/u) Slide 48 CYCLOTRON INSTITUTE 48 14 O+p 15 F we slowed down 14 O beam from 30 MeV/u to ~11 MeV/u. The excitation function was measured E cm =0.8-5 MeV. V. Goldberg et al. PRC 69, 031302(R) (2004)W.A. Peters et al. PRC 68, 034607 (2003) 1/2 + 5/2 + Slide 49 CYCLOTRON INSTITUTE 49 Expectations: R-matrix calculations Evident resonant structures in the spectrum. R-matrix parameters for expected single-particle structure. Slide 50 CYCLOTRON INSTITUTE TTIK method Scattering Chamber/Target 14 O Beam 57 MeV ~2*10 5 Hz 14 O 32.5 MeV Helium ~0.8atm 50 Slide 51 CYCLOTRON INSTITUTE 3.Types of reactions a)Elastic scattering b)Inelastic scattering c)Direct reactions: one nucleon transfer, few nucleons d)Breakup at intermediate energies e)Resonant elastic scattering TTIK method f)In-flight decay spectroscopy g)Multifragmentation 3 Slide 52 CYCLOTRON INSTITUTE 3f) In flight decay spectroscopy from R. Charity (Wash Univ) at CSSP12, Sinaia, Romania, June 24-July 7, 2012 Slide 53 CYCLOTRON INSTITUTE Basics of method Slide 54 CYCLOTRON INSTITUTE 2p decay of nuclei (gs) and states Slide 55 CYCLOTRON INSTITUTE (some) results Slide 56 CYCLOTRON INSTITUTE A. Steiner et al, Phys. Rept. 411 (2005) 325 Nuclear Equation of State (from atomic nuclei to neutron stars) 3g) Multifragmentation from SJ Yennello, CSSP12 Slide 57 CYCLOTRON INSTITUTE phase diagram of water Heat Input Temperature Ice (Solid) Water (Liquid) Steam (Gas) Ice & Water Water & Steam caloric curve of water nuclear matter Slide 58 CYCLOTRON INSTITUTE Large granularity arrays: NIMROD 228 modules Si/CsI Some Si/Si/CsI Ion Chambers 14 rings 3.6 o -167 o Neutron Ball S. Wuenschel et al. NIMA doi:10.1016/j.nima.2009.03.187 Slide 59 CYCLOTRON INSTITUTE 4. Instrumentation (very incomplete!) High efficiency detector systems Example HIRA (MSU, WU, IU) Complex systems: measure different types of reaction products (charged part, neutrons, gammas) e.g. SAMURAI @ RIBF high granularity detector systems HIRA, ORRUBA, ANASEN, TUDA, TECSA at TAMU Large amount of data to handle => fast, compact analog and digital electronics, acq and data handling computers 59 Slide 60 CYCLOTRON INSTITUTE S800 focal plane detectors Quadrupoles HiRA With 20 Identical detectors HiRA is highly configurable for different physics experiments. Slide 61 CYCLOTRON INSTITUTE 10 C experiments at TAMU set of 4 dE (64 um) - E (1500 um) Si telescopes ~ 400 Si ch ASICs Outside vacuum From L. Sobotka, WU in St. Louis Slide 62 CYCLOTRON INSTITUTE 62 Slide 63 CYCLOTRON INSTITUTE The TECSA detector system (Texas-Edinburgh-Catania Silicon Array) Specifications: 16 Micron Semiconductor type YY1 silicon detectors. 2 planes x 8 dets/each possible, or 8 telescopes in one plane. 16 strips per detector sector (256 channels total) Detectors are 300 m thick. 2 plates & 2 possible configurations flat and lampshade. Forward and backward angles Intended for (d,p) experiments in inverse kinematics & others 63 Slide 64 CYCLOTRON INSTITUTE 64 Slide 65 CYCLOTRON INSTITUTE Conclusions 65 Reactions with RIBs are the future of nuclear physics studies ISOL or in-flight production techniques Specificities: low rates and relatively poor beam characteristics large background Need instrumentation efforts: large facilities complex detection systems handling of large amount of data Need new interpretation theories & approximations Support data from experiments with stable beams Slide 66 CYCLOTRON INSTITUTE Collaborators R.E. Tribble, A. Banu *, CA Gagliardi, AM Mukhamedzhanov, M McCleskey, E Simmons, A. Spiridon, B. Roeder Texas A&M University F. Carstoiu IFIN-HH Bucharest E491 exp: TAMU &: N. Orr et al. (LPC Caen), P. Chomaz et al. (GANIL Caen), W. Catford et al. (Univ of Surrey), M. Chartier et al. (Univ of Liverpool), R. Lemmon, M. Labiche (Daresbury), M. Freer et al. (Univ of Birmingham), F. Negoita (IFIN Bucharest) L. Sobotka, R Charity et al (Washington Univ, St. Louis, MO) 66