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Managed by UT-Battelle for the Department of Energy Radioactive beams from e-beam driven photofission TRIUMF Users Workshop Jim Beene ORNL August 1-3 2007.

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Presentation on theme: "Managed by UT-Battelle for the Department of Energy Radioactive beams from e-beam driven photofission TRIUMF Users Workshop Jim Beene ORNL August 1-3 2007."— Presentation transcript:

1 Managed by UT-Battelle for the Department of Energy Radioactive beams from e-beam driven photofission TRIUMF Users Workshop Jim Beene ORNL August

2 2Managed by UT-Battelle for the Department of Energy Presentation_name Outline Some comments on HRIBF & our n-rich research program The photofission reaction: some advantages, some disadvantages An investigation of properties and capabilities of a e-beam driven facility

3 3Managed by UT-Battelle for the Department of Energy Presentation_name Recoil Mass Spectrometer (RMS) Injector for Radioactive Ion Species 1 (IRIS1) 25MV Tandem Electrostatic Accelerator Daresbury Recoil Separator (DRS) Oak Ridge Isochronous Cyclotron (ORIC) On-Line Test Facility (OLTF) High Power Target Laboratory (HPTL) Stable Ion Injector (ISIS) Enge Spectrograph HRIBF 2006

4 4Managed by UT-Battelle for the Department of Energy Presentation_name HRIBF Post-accelerated Beams 175 RIB species available (+26 more unaccelerated) 32 proton-rich species 143 neutron-rich species Post-accelerated Intensity Beam list increased by ~50% since 2003

5 5Managed by UT-Battelle for the Department of Energy Presentation_name The first transfer measurements on N=82 nuclei on / near r-process path yields, angular distributions of low-lying states measured first observation of p 1/2 state in 133 Sn three other states in 133 Sn measured, calibrated with 130 Te(d,p) evidence for numerous states in 131 Sn never seen before evidence that the f 5/2 level in 135 Te is at a significantly higher energy 132 Sn(d,p) 133 Sn K. Jones 130 Sn(d,p) 131 Sn - R. Kozub et al. 132 Sn(d,p) 133 Sn - K.L. Jones et al. 134 Te(d,p) 135 Te - S.D. Pain et al.

6 Decay spectroscopy of exotic nuclei -decay studies around 78 Ni with postaccelerated (3 MeV/u) pure neutron-rich RIBs Winger et al. Absolute beta-delayed neutron branching ratios for Cu and Ga Identification of new excited states in 77 Zn, 78 Zn, 82 Ge, 83 Ge, and 84 Ge Systematics of single particle levels (e.g. neutron s 1/2 ) near doubly magic 78 Ni Range out unwanted high-Z contamination with high pressure & tape transport S. Liddick et al., PRL 97,2006, Discovery of superallowed -decay Enhanced due to the same proton and neutron shell structure rp-process termination En route to 104 Te 100 Sn 2 ( 105 Te)/ 2 ( 213 Po) ~ 3

7 Fusion & Fission Probing the influence of neutron excess on fusion at and below the Coulomb barrier Large sub-barrier fusion enhancement has been observed Inelastic excitation and neutron transfer play an important role in the observed fusion enhancement Important for superheavy element synthesis ERs made with 132,134 Sn cannot be made with stable Sn Shapira et al., Eur. Phys. J. A 25, s01, 241 (2005) Liang et al., PRL 91, (2003); PRC 75, (2007) Pioneering studies with neutron-rich radioactive beams of heavy nuclei Coulex Probing the evolution of collective motion in neutron-rich nuclei Increasingly larger contributions of neutrons to B(E2) values above 132 Sn Recoil-in-Vacuum technique used to measure the g-factor for the first 2 + state in 132 Te: Stone et al., PRL 94, (2005) Padilla-Rodal et al. Phys. Rev. Lett. 94, (2005) Yu et al., Eur. Phys. J. A 25, s01, 395 (2005) Radford et al., Nucl. Phys. A752, 264c (2005) Varner et al., Eur. Phys. J. A 25, s01, 391 (2005)

8 8Managed by UT-Battelle for the Department of Energy Presentation_name RISAC Science Drivers & the electron driver Nuclear Structure –Probing the disappearance of shells Spectroscopy & reactions in 132 Sn, 78 Ni regions –Evolution of collective motion We can probe 112 Zr and 96 Kr regions (not 156 Ba) –Neutron Skins Structure/reaction studies of the most n-rich –SHE Reactions with 132 Sn (~10 9 ) and vicinity For Z=112, N=184, reaction mech. Studies with 92,94 Sr (10 6, 10 7 ) Nuclear Astrophysics –Decay spectroscopy ( n, ) Stockpile Stewardship –Surrogate reactions (n transfer, etc.)

9 9Managed by UT-Battelle for the Department of Energy Presentation_name Disclosure / Disclaimer The discussion of a photo-fission driver that follows was originally developed based on HRIBF considerations. We have boundary conditions that are largely irrelevant to ISAC: –A turn-key simple-to-maintain accelerator –A concept that guarantees a minimum level of performance without need of major targetry breakthroughs. –A capability dedicated to extending our reach toward very n-rich nuclei in a timely manner

10 10Managed by UT-Battelle for the Department of Energy Presentation_name HRIBF as a two driver facility We are developing a proposal for a turn-key electron accelerator (e- machine), capable of providing CW ~ 100kW beams with energies at or above 25 MeV. This accelerator would be dedicated to producing neutron-rich species by photofission of actinide targets. Such an accelerator is by far the most cost effective means to achieve in-target fission rates in the mid /s scale. A comparable upgrade to our p-rich capability would be far more expensive Target development to support operation at >10 13 f/s (~50kW )is well in hand. Thus we are confident we can reach fission rates about 20 times larger than current HRIBF capability. The increase in fission rate is not, however a good comparative metric. –Photofission is a colder process than proton induced fission. –It results in lower actinide excitation, and less neutron evaporation from both the excited actinide system and the fragments. –Consequently production of very neutron-rich species can be enhanced by a substantial factor compared to 50 MeV proton induced fission, at the same fission rate.

11 11Managed by UT-Battelle for the Department of Energy Presentation_name 238 U photo-fission is dominated by the GDR

12 12Managed by UT-Battelle for the Department of Energy Presentation_name But photo-fission is not the dominant GDR decay channel (,n) and (,2n) account for ~2/3 of GDR cross section Substantial 236,237 U production is inevitable Data from Livermore and Saclay groups

13 13Managed by UT-Battelle for the Department of Energy Presentation_name Photofission yields U(,f) f/s easily achieved About 20x current HRIBF But real gain >> 20x (p,f) systematics from Tsukada (,F) from ORNL systematics + Jyvaskyla model

14 14Managed by UT-Battelle for the Department of Energy Presentation_name A sample comparison with data: Sn isotopes

15 15Managed by UT-Battelle for the Department of Energy Presentation_name Total neutron multiplicities are important figures of merit for our purposes Proton induced fission at HRIBF energies – p =50 MeV n =8.5 – p =500 MeV n ~13 Electron induced photofission: –E e =25 MeV n =3.3 – e = MeV n =3.4 Neutron-induced fission is very similar in many ways to photofission. 238 ~15 MeV has final state properties very similar to E 0 =25-50 MeV photofission.

16 16Managed by UT-Battelle for the Department of Energy Presentation_name RIB production by photofission ph-f/s 10 A 40 MeV p

17 17Managed by UT-Battelle for the Department of Energy Presentation_name Conservative target design for performance determination 3 cm =3 g/cm 3 d=3 cm (0.3 R M ) t=30g/cm 2 5X 0 (10cm) M=212 g =6 g/cm 3 d=3 cm (0.6 R M ) t=30g/cm 2 5X 0 (5cm) M=212 g X o =6 g/cm 2 (U)

18 18Managed by UT-Battelle for the Department of Energy Presentation_name Photofission target issues/ limitations Direct bombardment e-beam directly incident on targets If goal is to be met, beam energies less than ~80 MeV may give problems using current target technology without further testing and or development.

19 19Managed by UT-Battelle for the Department of Energy Presentation_name Photofission target issues Converter + target

20 20Managed by UT-Battelle for the Department of Energy Presentation_name An example of a somewhat more aggressive design 5 cm =6 g/cm 3 t=30g/cm 2 (5X 0 ) M=495 g 2.3 x UC x front surface area compared to 3 cm dia. Cylinder Similar power required to reach f/s 25 MeV)

21 21Managed by UT-Battelle for the Department of Energy Presentation_name U(,f) vs U(p,f) 1 GeV

22 22Managed by UT-Battelle for the Department of Energy Presentation_name U(,f) vs U(p,f) 1 GeV (p,f) 100 A on 30 g/cm 2 5x10 13 f/s (,f) f/s (~50 kW 25 MeV)

23 23Managed by UT-Battelle for the Department of Energy Presentation_name U(,f) vs U(p,f) 1 GeV (p,f) 100 A on 30 g/cm 2 5x10 13 f/s (,f) f/s (~50 kW 25 MeV)

24 24Managed by UT-Battelle for the Department of Energy Presentation_name Conclusions I: RIB production f/s can be achieved with an ~50 kW facility –Requires only modest sized targets to achieve initial goals 3 cm x 5 c m (212 g) –<10 kW deposited in target –25 MeV e beam can be used with converter Additional technologies can be considered Substantially larger yields can be achieved with larger targets and higher beam powers –500g to 1kg & kW –What is release time? Even with thick converters, cannot isolate production target from beam power and still produce fission at high rates Pulsed e-beam can aggravate thermal and mechanical stress issues in target.

25 25Managed by UT-Battelle for the Department of Energy Presentation_name Conclusions II: Shielding Thick target bremsstrahlung: – 1/2 ~100/E 0 degrees –Forward angle dose rate D~300 E 0 (Gy h -1 )(kW m -2 ) -1 D~1.5 x 10 7 Gy h -1 at 1 m for 50 MeV, 1MW e beam –6m concrete or ~1m Fe –90 0 dose rate D~70 (Gy h -1 )(kW m -2 ) -1 D~7 x 10 4 Gy h -1 at 1m for 1MW e beam (E 0 > 20 MeV) NCRP Report No 144 (2003 )

26 26Managed by UT-Battelle for the Department of Energy Presentation_name Electron Beam Facility Elevation

27 27Managed by UT-Battelle for the Department of Energy Presentation_name e-Driver Upgrade Upper Level

28 28Managed by UT-Battelle for the Department of Energy Presentation_name e-Driver Upgrade Lower Level

29 Photo-fission yield In target

30 Photo-fission yield From ion source

31 Photo-fission yield Post-accelerated

32 32Managed by UT-Battelle for the Department of Energy Presentation_name Science highlights with e-driver upgrade Will test the evolution of nuclear structure to the extremes of isospin Will improve our understanding of the origins of the heavy elements Decay properties of nuclei at the limits Crucial for understanding the formation of elements from iron to uranium Crucial for understanding the formation of elements from iron to uranium Reaction mechanisms for the formation of superheavy nuclei Collective properties in extended neutron radii Coulomb excitation near 96 Kr Evolution of single-particle structure Transfer reactions at 132 Sn & beyond

33 33Managed by UT-Battelle for the Department of Energy Presentation_name Broad program to study reactions with and structures of neutron-rich nuclei Structure studies: Structure studies: Isospin-dependent changes in - single-particle properties - collectivity - symmetries - pairing Reaction studies: - interplay between structure and reaction (SHE synthesis) - one- and multi-nucleon transfer Domain: Domain: Uncharted- or barely-explored regions - at or near doubly magic 78 Ni & 132 Sn - around magic numbers Z=28, 50 and N=50, 82 - new transitional nuclei (N=50-60, 82-90) - unexplored deformed nuclei (N~90) Tools : Tools : Newly developed techniques and detectors

34 34Managed by UT-Battelle for the Department of Energy Presentation_name Measurements to probe shell structure far from stability Gross properties: Masses (binding energies) Half lives Radii Level densities (n, ) -- related to r-process abundances, [use (d,p)] Single-particle properties: Energy, spin, parity, spectroscopic factors, g-factors Parallel momenta in knock out reactions (fast beams) Collective properties: Low-lying energy spectra (e.g., 2 + states, 4 + ) B(E2) & electromagnetic moments We will have an unparalleled opportunity to use transfer, decay and in-beam spectroscopic tools to employ these probes in uncharted regions of n-rich nuclei. Higher spin states (band structures) We will have an unparalleled opportunity to use transfer, decay and in-beam spectroscopic tools to employ these probes in uncharted regions of n-rich nuclei.

35 35Managed by UT-Battelle for the Department of Energy Presentation_name Conclusion (for HRIBF-scale facility) An electron-beam based facility can produce intense beams in a cost-effective way Such a facility would be competitive world-wide for neutron-rich beams until FRIB is available Cost containment is important There is a relatively short window during which such a facility is relevant.

36 36Managed by UT-Battelle for the Department of Energy Presentation_name Some Comments (for ISAC-scale facility) An electron-beam based facility can produce intense n-rich beams in a uniquely cost-effective way It is not possible to isolate the production target from beam power, as fully as is done with (d,n) (n,F) two-step facilities. Pulsing of high-power beams at low rates can be a serious problem for target performance Substantial yields of a few alpha–emitters can be expected If power can be handled, a MW scale photo- fission facility could produce ~ mid f/s.

37 37Managed by UT-Battelle for the Department of Energy Presentation_name Initial Concept of Two Plugs in a Common Vacuum Envelope

38 38Managed by UT-Battelle for the Department of Energy Presentation_name The Target Plug

39 39Managed by UT-Battelle for the Department of Energy Presentation_name The Target Plug – Some Features Ion source mounted on high-voltage deck inside a grounded outer vessel Outer vessel vacuum tight except at e-beam entrances and RIB Beam exit –Use fast apertures over both locations Converter target directly in front of fission target – also at high voltage

40 40Managed by UT-Battelle for the Department of Energy Presentation_name High-Power Converter Target Designs Based on ORELA Target Design There will be a converter target as part of each target ion source plug

41 41Managed by UT-Battelle for the Department of Energy Presentation_name First Beam Filter – Second Plug

42 Ion 200 keV (ions/s) Tandem (ions/s) t 1/2 (s) 78 Ni Cu 81 Cu ???? 82 Zn50000? 94 Br 96 Br 1x ? 137 Sn 138 Sn ? 137 Sb 140 Sb 9x x ???? 149 Cs2x10 4 4? Examples with eMachine Decay studies pushing the frontier of n-rich nuclei 0.1 ions/s t 1/2 & n rates for many r process nuclei are accessible Energy levels test evolving nuclear structure

43 43Managed by UT-Battelle for the Department of Energy Presentation_name The evolution of single-particle levels and shapes in very neutron-rich nuclei beyond the N=50 shell closure beam T 1/2 (s) main results 76 Cu 0.65 n-branching ratio I n 77 Cu 0.46I n, - levels in N=47 77 Zn 78 Cu 0.35I n, I of 78 Cu 49 revised 79 Cu 0.19 n decay observed first time 83 Ga 0.30 n,, s 1/2 in N=51 83 Ge 84 Ga in N=52 84 Ge, s 1/2 in 83 Ge 85 Ga ~0.07rate of 0.1pps… -decay experiments with postaccelerated (3 MeV/u) pure neutron- rich RIBs, Oct-Nov 2006 Jeff Winger et al., RIB-108 and 122

44 44Managed by UT-Battelle for the Department of Energy Presentation_name The evolution of single-particle levels and shapes in very neutron-rich nuclei beyond the N=50 shell closure 84 Ga 84 Ge* (2+) 84 Ge (0+) 84 Ga 84 Ge* 83 Ge* ( s 1/2 ) 83 Ge( d 5/2 ) n N=51 83 Ge N=52 84 Ge Nov06 : experiment with 2 pps of 3 MeV/u 84 Ga -gated -spectrum (0.5 keV/ch) 248 keV625 keV

45 45Managed by UT-Battelle for the Department of Energy Presentation_name Transfer reactions: shell structure of n-rich nuclei E P (channels) ExEx 2f 7/2 3p 3/2 2f 5/2 3p 1/2 ? Ion Intensity (ions/s) t 1/2 (s) 84 Ge3x Se3x Sr 98 Sr 7x10 4 1x Sn3x Te 140 Te 5x10 6 2x ? RIB Example: (d,n)-like reactions neutron s.p. levels protons detected in Si-array Recoils detected in coincidence Jones et al. with the e-driver Single-particle transfer near 78 Ni and 132 Sn Reactions of interest (d,p) ( 9 Be, 8 Be) ( 3 He,d) ( 3 He, ) ( 7 Li, 8 Be) Single-particle states around closed shells provide a fundamental shell model test 132 Sn(d,p) 133 HRIBF 6x10 4 ions/s

46 2109 keV C( 134 Te, 12 C) 135 Te neutron transfer Particle-gamma angular correlations

47 47Managed by UT-Battelle for the Department of Energy Presentation_name Coulomb excitation in n-rich systems n-rich beams C, Ti, Zr Beam BaF Array target CLARION Charged-particle Gamma array Ion Intensity (ions/s) t 1/2 (s) 84 Ge3x Se3x Sr1x Sn Te 140 Te 5x10 6 2x ? With eMachine: neutron-rich nuclei from N=50 to N=82 (and beyond) are accessible Probes the evolution of collective motion in loosely-bound, neutron-rich nuclei Radford et al. Beene et al. HRIBF Sn/s

48 Probes the influence of neutron excess on fusion at and below the Coulomb barrier important for superheavy element synthesis Heavy ion fusion reactions More n-rich projectiles Further below barrier 134 Sn below 10 mb Transfer reaction studies on the same system will help to understand reaction mechanism Ion Intensity (ions/s) t 1/2 (s) 92 Br2x Sn 136 Sn 3x with eMachine HRIBF Results Liang et al.

49 49Managed by UT-Battelle for the Department of Energy Presentation_name Unattenuated angular correlations: Theory & experiment 180° 0° W ( ) 130 Te beam scattered 130 Te stopped in Cu 12 C recoil = 155° = 132° = 90° 130 Te SIB Hyball Ring 2

50 Magnetic moment: RIV attenuated angular correlations

51 51Managed by UT-Battelle for the Department of Energy Presentation_name Conclusion (for HRIBF-scale facility) An electron-beam based facility can produce intense beams in a cost-effective way Such a facility would be competitive world-wide for neutron-rich beams until FRIB is available Cost containment is important There is a relatively short window during which such a facility is relevant.

52 52Managed by UT-Battelle for the Department of Energy Presentation_name Some Comments (for ISAC-scale facility) An electron-beam based facility can produce intense beams in a cost-effective way It is not possible to isolate the production target from beam power, as is done with (d,n) (n,F) two-step facilities. Pulsing of high-power beams is a serious problem Substantial yields of a few alpha–emitters should be expected If power can be handled, a MW scale photo- fission facility could produce ~ mid f/s.

53 53Managed by UT-Battelle for the Department of Energy Presentation_name Neutron transfer reactions Accessible at HRIBF Accessible with e-machine

54 54Managed by UT-Battelle for the Department of Energy Presentation_name Coulex (1-step) Accessible at HRIBF Accessible w e-machine

55 55Managed by UT-Battelle for the Department of Energy Presentation_name Multi-step Coulex Accessible at HRIBF Accessible w e-mach

56 56Managed by UT-Battelle for the Department of Energy Presentation_name g-factor measurements Accessible at HRIBF Accessible w e-mach

57 57Managed by UT-Battelle for the Department of Energy Presentation_name A Photo-fission Facility -Driver Requirements – ~25 MeV or higher, CW, turnkey –100 kW or more at 25 MeV –80 kW or more at 50 MeV Turnkey options –25 MeV rhodotron –50 MeV SC linac Costs are similar

58 58Managed by UT-Battelle for the Department of Energy Presentation_name Appendix

59 59Managed by UT-Battelle for the Department of Energy Presentation_name 238 U+p (1 GeV)

60 60Managed by UT-Battelle for the Department of Energy Presentation_name After recoil into vacuum, the ionic B field direction is randomly oriented. The nuclear spin of the recoil is initially aligned in the plane of the target, but precesses about total angular momentum F by hyperfine interaction. The angular distribution of decay gamma emission is thereby attenuated. Beam Target Foil Coulex recoil Target recoil J = electron spin -- randomly oriented I = nuclear spin -- aligned by reaction F = I + J Measurements of g-factors by Recoil in Vacuum

61 61Managed by UT-Battelle for the Department of Energy Presentation_name Neutron transfer reactions Accessible at HRIBF Accessible with 1 MW ISOL

62 62Managed by UT-Battelle for the Department of Energy Presentation_name g-factor measurements Accessible at HRIBF Accessible with 1 MW ISOL

63 63Managed by UT-Battelle for the Department of Energy Presentation_name Fission rate and power in target

64 64Managed by UT-Battelle for the Department of Energy Presentation_name Distribution of E deposit and fission

65 65Managed by UT-Battelle for the Department of Energy Presentation_name Photo-fission yield From ion source

66 66Managed by UT-Battelle for the Department of Energy Presentation_name Science highlights with e-driver upgrade Will test the evolution of nuclear structure to the extremes of isospin Will improve our understanding of the origins of the heavy elements Decay properties of nuclei at the limits Crucial for understanding the formation of elements from iron to uranium Crucial for understanding the formation of elements from iron to uranium Reaction mechanisms for the formation of superheavy nuclei Collective properties in extended neutron radii Coulomb excitation near 96 Kr Evolution of single-particle structure Transfer reactions at 132 Sn & beyond


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