STORAGE RING EXPERIMENTS

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1 STORAGE RING EXPERIMENTS at the Interface of Atomic and Nuclear Physics C. Brandau 1,2, Chr. Kozhuharov 1,3, Yu. A. Litvinov 1,4 1 GSI; 2 EMMI; 3 BfA & VBL; 4 Universität Heidelberg EMMI Workshop The 229m Th Nuclear Isomer Clock GSI Darmstadt, Germany, September 25 27, 2012

2 Why Storage Rings?

3 The Role of Failure You can't possibly get a good technology going without an enormous number of failures. It's a universal rule. If you look at bicycles, there were thousands of weird models built and tried before they found the one that really worked. You could never design a bicycle theoretically. Even now, after we've been building them for 100 years, it's very difficult to understand just why a bicycle works it's even difficult to formulate it as a mathematical problem. But just by trial and error, we 1 found out how to do it, and the error was essential. Freeman Dyson (interview by Stewart Brand) 1 Caveat - cf. also H.M. Enzensberger, Hammerstein oder Der Eigensinn, Suhrkamp, Frankfurt/M, 2008 (footnote by C.K.) Freeman Dyson 2007 (Wikipedia) Institute for Advanced Studies

Present GSI Accelerators Heavy Ion Synchrotron,SIS, 2 AGeV for A/q=2 (1 AGeV U) Heavy Ion Linac UNILAC (<20 MeV/u) - Beams Ion of all (chemical) elements and all stable isotopes: sources from

4 Present GSI Accelerators Heavy Ion Synchrotron,SIS, 2 AGeV for A/q=2 (1 AGeV U) Heavy Ion Linac UNILAC (<20 MeV/u) - Beams Ion of all (chemical) elements and all stable isotopes: sources from hydrogen to uranium - Broad range of energies: from thermal to relativistic energies (2AGeV) - Secondary beams of unstable (radioactive) nuclei; ground state, isomers - Unique beam properties: well-defined charge states, cooled and stored beams - Decelerated and cooled species HITRAP (4 K) - (pions) Fragment Separator FRS Experimental Storage Ring ESR

5 Protonenzahl Z Neutronenzahl N

6 ESR (Photograph by A. Zschau) B. Franzke, NIM B 24/25 (1987) 18

7 Storage Rings: Electron Cooled Ion Beams electron collector electron collector electron gun high voltage platform electron gun magnetic field electron beam high voltage platform ion beam magnetic field electron beam ion beam G.I. Budker, At. En. 22 (1967) 346 G.I. Budker, A.N. Skrinsky et al., IEEE NS-22 (1975) 2093

8 Cooling = narrowing velocity, size and divergence of stored ion beams

9 'Phase transition' to a linear ion chain ESR circumference 10 4 cm For 1000 stored ions, the mean distance amounts to about 10 cm. At mean distances of about 10 cm and larger the intra-beam-scattering disappears. M. Steck et al., PRL 77, 3803 (1996)

10 Recording the Schottky-noise From the FRS To the SIS Dipole magnet Septummagnet Hexapolemagnets Quadrupoletriplet v 0 v Schottky pick-ups Gas-target Electron cooler Schottky Pick-ups amplification summation FFT Quadrupoledublet f ~ 2 MHz 0 Stored ion beam RF-Accelerating cavity Fast kicker magnet Extraction

11 300 khz / 60 MHz Schottky TCAP W Pt mass unknown Tl Bi Au Hg Pt Hg Bi Ir 186 Au Os Pt Ir Po Bi Au 77+ W 184 Pt 77+ Ir X 71+ Tl Pb 81+ Tm68+ Dy Tb Gd Hf 156 Pt Po Ir Os known masses unknown masses Pt q+ q+ Lu 74+ W Er Ho Nd X A Os 75+ Au 78+ Bi 83+ Hg Lu 161 I Gd A 198 Tl 80+ Yb 77+ Ir Re W Hg 80+ Tl 80+ Pt Hg 80+ Ir Pb Bi 82+ Dy Yb Au Pb Re74+ Pr Eu 62+ Sm m,g Bi Pb Dy 65+ Tb Cs Hg Au79+ Ir Pt 78+ Er Os Pt Ta Au Pb 81+ Ho Tl Hg Os Tm Bi Tl 80+ Pb Hf Tl 81+ Po Tb Ta Hg Hg Tl Lu Re Au mass knownpo Hg Ir Er 77+ Pb Pb 80+ Po Pt 20.0 Re Tm Au Pb Bi Pb 82+ Po 84+ Hf Au Po m,g Tl 79+ Pt Bi Hg Au Intensity / arb. units Intensity / arb. units 0 Bi Pb Pb 81+ Tl 80+ Bi 82+ Ta 5 Hf Number of channels 2 Recording time 30 sec Bi Frequency / khz / Frequency Hz

12 ILIMA: Masses and Halflives

13 Two-Body Beta Decay

SCHOTTKY SIGNAL OF THE BOUND-STATE -DECAY 187 Re 75+ 187 Os 75+ 187 Re 75+ primary beam

14 SCHOTTKY SIGNAL OF THE BOUND-STATE -DECAY 187 Re Os Re 75+ primary beam ions 187 Os ions after 5.7 h storage time T 1/2 ( 187 Re 75+ ) = 33(2) y

15 Orbital Electron Capture Conventional EC-theory: W. Bambynek et al., Rev. Mod. Phys. 49, 1977 Gamow-Teller allowed transition S-electron density at the nucleus: f S (0) 2 1/ n 3 P EC (neutral atom) 1/ n 3 = 2.4 P K (H-like) 1 1/ 1 3 = 1 Conclusion: H-Like ion should have 41% longer half-life EC (H-like)/ EC (He-like) 0.5

16 Orbital Electron Capture Decay of Few-Electron Ions

17 Orbital Electron Capture Decay of Few-Electron Ions Expectations: EC (H-like)/ EC (He-like) 0.5 EC (H-like)/ EC (He-like) = 1.49(8) EC (H-like)/ EC (He-like) = 1.44(6) Yu.A. Litvinov et al., Phys. Rev. Lett. 99 (2007) N. Winckler et al., Phys. Lett. B579 (2009) 36

18 Orbital Electron Capture Decay of Few-Electron Ions Gamow-Teller transition µ = µ N I. N. Borzov et al., Phys. At. Nucl. (2009) Theory: (H)/ (He) = (2I+1)/(2F+1) Z. Patyk et al., Phys. Rev. C 77 (2008)

19 F. Nolden et al., Nucl. Inst. Meth. A659 (2011) 69

20 Three Parent He-Like 142 Pm Ions CM e p R cos( ) emitted backward f = ± 3.91 khz (120 ch) recoil Beam direction emitted forward

21 Photorecombination in cosmic plasmas Courtesy D.W. Savin, Columbia Astrophysics Lab (CAL), New York, N.Y. electron ionized (stars, supernovae, galaxies, ) photoionized (radiation field) (PNebulae, x-ray binaries, AGNs, ) High Te DR Low T e DR Sun SNR PN XRBs Galaxies AGNs

22 Radiative Recombination, Dielectronic Recombination and Nuclear Excitation by Electron Capture

24 20 years later - Astrophys. J. 139, 776 (1964) 40 years later J.B..A. Mitchell et al, PRL. 50, 335 (1983), D.S. Belic et al PRL (1983), P.F. Dittner et al. PRL (1983) first experimental observations

25 49 Years later (20 years ago): First GSI-ESR PRL

Experimental Storage Ring injection from SIS/FRS (ESR) electron target electron cooler recombination detector circumf. 108.

26 Experimental Storage Ring injection from SIS/FRS (ESR) electron target electron cooler recombination detector circumf m energies MeV/u ions up to U 92+ extraction to HITRAP / reinjection to SIS Schottky pick-up Cooled ion beams in well-defined ionic states

27 DR-Measurement Merged electron and ion beams Drift-tube defined variation of the relative ion-electron velocities Recombination Separation by the ESR dipol magnet Single particle detection (4π) α(e CM ) vrelσ E 1 1 β β N e i CM Ion R n e L U

28 Dielectronic Recombination of Li-like Gold

29 Li-like Xe51+

30 Li-like Xe 51+ (preliminary) Continuum electron are captures into series of Rydberg state up to the series limit for both types of excitation of the 2s electron: 2s 2s 2p 2p

31 NEEC first mentioned by Goldanskii & Namiot Phys. Lett. 62B (1976) Natural line widths ev Resonance strength 1 bev A. Pálffy, Z. Harman, W. Scheidt, PRA 73(2006)012715

32 Main Idea, Feasibility, Proposal (Challenge - only a few events per minute)

33 What would happen

34 Basic Idea for a NEECx experiment Illustrative Example: 238 U The first excited state in 238 U decays predominantly via L-IC (44.9 kev) Bare uranium ions bombard cold electron target with the appropriate energy an electron is captured into the L shell and the nucleus is excited. K-vacancies in uranium decay in sec, the L-electron goes to the K-shell, i.e. this partial decay width dominates the total one. The competing process of radiative recombination, RR, is very fast. The excited nucleus leaves the RR-background zone The excited nucleus can decay only via gamma emission i.e. slower by the conversion coefficient (270) The gammas can be detected in a background free zone in coincidence with ions which have captured one electron The colder the electrons the better. (The experimental proposal is currently being prepared.)

38 Stochastic Cooling x long. Kicker Pick-up x mean position in phase space transv. Pick-up Combiner- Station transv. Kicker x Kicker long. Pick-up x ESR storage ring Stochastic cooling is in particular efficient for hot ion beams Cooling time τ scales as N ion / bandwith

39 Stochastic cooling (self-correction of trajectory)

40 DR of H-like U 91+ D. Bernhardt et al. Phys. Rev. A (R) (2011) Breit Interaction in dielectronic recombination of hydrogenlike uranium U 91+ 1s + e U 90+ 2l nl j 1 j 2

41 energy spread [ ev ] Energy Resolution at ESR low collision energies (c.m.) high collision energies (c.m.) collision energies from mev to sub MeV present ESR (e-cooling): energy spread from e-beam kt = 120 mev kt = 100 ev Present TSR e-target kt = 2 mev kt = 20 ev present ESR (stochastic cooling) energy spread from ion beam dp/p = (1 ) NESR e-target kt = 5 mev kt = 10 ev NESR ion beam with dp/p = (1 ) electron energy (c.m.) [ ev ] resolution ~10 mev to ~10 ev

42 HITRAP so far built / designed

43 Study Group Norbert Angert Angela Bräuning-Demian Hakan Danared Wolfgang Enders Mats Engström Bernhard Franzke Anders Källberg Oliver Kester Michael Lestinsky Yuri Litvinov Markus Steck Thomas Stöhlker

44 2nd Realistic Scenario for a NEEC Experiment Ph. Walker (19/2 - isomer, 17.7 min), Yu. Litvinov, Th. Stöhlker (CryRing)

45 Basic Idea Ionization IC/BIC Plasma Atom Nucleus DR NEEC/NEET/ DR-NEET IC internal (electron) conversion BIC bound internal conversion DR dielectronic recombination NEEC nuclear excitation by electron capture NEET nuclear excitation by electron transition

46 Nucleus relative contributions to the 2s 1/2-2p 1/2 splitting Why Li-Like Heavy-Ions? Radial density distribution of low-lying electron orbitals in U 91+ 2s 1/2-2p 1/2 Energy Splitting for Li-like Ions experimental uncertainties C. Brandau et al., PRL 91 (2003) (-) nuclear size nuclear charge Z

47 Rate Coefficient [ arb. units ] n = 25 n = 25 n = 24 n = 23 n = 22 n = 21 j = 1/2 n = 20 n = 19 j = 3/2 j > 3/2 n = 18 E( 2s 2p 1/2 ) Low-Energy PR Spectrum of Li-like Neodymium ( 150 Nd 57+ ) Li-like ion ( n = 0) Nd 56+ (1s 2 2p3/2 nl j ) 2 series of resonances: Nd 56+ (1s 2 2p1/2 nl j ) E ( 2s 1/2 2p 1/2 ) = ev n min = x 5 n = and to E ( 2s 1/2 2p 3/2 ) = ev n min = Electron-Ion Collision Energy (c.m.) [ ev ] different overlap of 2s and 2p wavefunctions with the nucleus => shift of a whole pattern of resonances.

48 Rate Coefficient [10-9 cm 3 s -1 ] Li-like 142 Nd 57+ vs. 150 Nd e + A Nd 57+ (1s 2 2s 1/2 ) A Nd 56+ (1s 2 2p 1/2 18l j' ) A = 142 A = 150 j' = 1/2 j' = 3/2 j' > 5/2 j' = 5/ Relative Energy [ ev ] shift 40 mev C. Brandau, et al., PRL 100 (2008)

49 Li-like 142 Nd 57+ vs. 150 Nd 57+ Rate Coefficient [10-9 cm 3 s -1 ] n=19 A Nd 56+ (1s 2 2p 1/2 n l j' ) A Nd 56+ (1s 2 2p 3/2 8 l j' ) j'=1/2 j'=1/ A = 142 A = n= j'=5/2 j'=7/2 j'=3/2 j'=9/2 j'=11/2 j'=13/2 j'=3/2 j'=15/2 n= C. Brandau, et al., PRL 100 (2008) Relative Energy [ev]

50 A Nd 57+ DR-IS and Change in Mean Square Radius from maxima, minima and inflection points: 154 values for 2s 1/2-2p 1/2 E = 40.2 (3)(6) mev 45 values for 2s 1/2-2p 3/2 E = 42.3 (12)(25) mev + full QED calculations + NP 0.3 mev for A=150 r 2 ( ) = 1.36 (1)(3) fm 2 C. Brandau, et al., PRL 100 (2008) Y.S. Kozhedub, et al., PRA 77 (2008) Z. Harman, et al., in preparation.

51 Production of Li-like (!) Exotic Ions U 370 MeV/u in SIS Be-target (1 cm stripping foil = 1850 mg/cm 2 ) Li-like 237 U ~169 MeV/u (total 237 U q+ : ) complexities : + energy loss and straggling in thick target + distribution of charge states + cooling times ~ 1-5 min (for hot fragments far off Cool?) => beam loss due to recombination in cooler (~95 % after 5 min)

52 Preparation of Li-like Exotic Beams in the ESR or: the Storage Ring as an Isotope Separator injection cooling + breeding dbr=1.1 % scraping 237 U 89+ (3e-) 232/87+: 232 Th 87+ (3e-) 238 U 90+ (2e-) 237 U 90+ (2e-) 237 U 89+ (3e-) 237/89+: 237 U 89+ (3e-) 234/88+: 234 Pa 88+ (3e-) 231/87+: 231 Th 87+ (3e-) Time After Injection (min) Revolution Frequency intensities db-scale (log!) C. Brandau, et al., J. Phys.: Conf. Ser. 194 (2009) C. Brandau, et al., Hyperfine Interactions 196 (2010)

Isotope Shift and Hyperfine Effects in the Dielectronic Recombination of In-Flight Synthesized A U 89+ (A=236, 237, 238) rate coefficient [arb. units] 6.

53 Isotope Shift and Hyperfine Effects in the Dielectronic Recombination of In-Flight Synthesized A U 89+ (A=236, 237, 238) rate coefficient [arb. units] 6.0 DR of A U A = 238 A = 237 ( r 2 + HFS) A = 236 ( r 2 ) "0th" analysis (very preliminary) electron-ion collision energy (c.m.) [ev]

54 Rate [ Arb. Units ] Nov 2010 Test Run: Brevium - 234m Pa 10 T0 recombination rate (outer side of ring) - rate (inner side of ring) T2 1 preliminary Time after injection [ min ]

55 Kazimierz Fajans Brevium, 1913 Otto Hahn and Lise Meitner Protoactinium, 1917 (1918) Latin. Man's natural language. Spoils your style. Useful for reading the inscriptions on public fountains. Beware of quotations in Latin: they always conceal something improper. Gustave Flaubert

56 Rate coefficient [ arb. units ] DR of Isomers in 234 Pa 88+ DR of 234 Pa T0: 30 sec after inj. (g.s. + i.s.) T2: 300 sec after inj. (g.s.) T0 - T2: Isomer (?) preliminary x2 n (4+ gs) = 0.66 (P. Walker, priv. comm.) Electron-ion collsion energy [ ev ] preliminary

57 Conclusions A storage ring for high-z ions in well-defined charge states, equipped with electron cooling capabilities for well-defined ion velocities and furnished with some nice instrumentation is a very good tool for nuclear and atomic physics studies. GPAC-accepted 229m Th-LoI and proposal. Beam Time!? PhD students?

Nuclear Excitation via Electron Capture NEEC. Realistic Experimental Scenario at a Storage Ring

Nuclear Excitation via Electron Capture NEEC Realistic Experimental Scenario at a Storage Ring Christophor Kozhuharov GSI Darmstadt Atomic Physics Division Workshop on Nuclear Physics in Hot Dense Plasmas