This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC , the State of Michigan and Michigan State University. Michigan State University designs and establishes FRIB as a DOE Office of Science National User Facility in support of the mission of the Office of Nuclear Physics. Frederique Pellemoine Target Systems Group Leader Rare Isotope Beam Production with Proton Beam: Target Consideration

 Rare Isotope Production Mechanics  Rare Isotope Production Techniques ISOL and In-Flight  ISOL Target Requirements and Material challenges  Examples of ISOL Target Concepts using Proton Beams Multi-disk target Molten metal/salt target 2 step target  Examples of other Rare Isotope Production Target Concepts Outline F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 2

 There are a variety of nuclear reaction mechanisms used to add or remove nucleons Spallation Fragmentation Coulomb fission (photo fission) Nuclear induced fission Light ion transfer Fusion-evaporation (cold, hot, incomplete, …) Fusion-Fission Deep Inelastic Transfer Charge Exchange  There is no best method Rare Isotope Production Mechanisms F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 3

 Fragmentation (FRIB, RIBLL Lanzhou, NSCL, GSI, RIKEN, GANIL, ISOLDE…) Projectile fragmentation of high energy (>50 MeV/A) heavy ions Fragmentation of a target with high energy protons or heavy ions. Could have the fragmentation of the projectile with heavy ion beams.  Fission (HRIBF, ARIEL, ISAC, JYFL, BRIF, ISOLDE…) Induced fission into roughly equivalent mass products »Medium range mass region The fissioning nuclei can be the target (HRIBF, ISAC) or the projectile (GSI, NSCL, RIKEN, FAIR, FRIB)  Spallation (ISOLDE, TRIUMF-ISAC, EURISOL, SPES, …) Products distributions peaks few mass units lighter than target Production Mechanisms at High Energy F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 4

Rare Isotope Production Techniques  In-flight method GSI, RIKEN, NSCL, FRIB, GANIL, ANL, RIBBAS Provides beams with energy near that of the primary beam »For experiments that use high energy reaction mechanisms »Luminosity (intensity x target thickness) gain of 10,000 »Individual ions can be identified Efficient, Fast (100 ns), chemically independent separation Production target is relatively simple  Isotope Separator On Line (ISOL) method HRIBF, ISAC, SPIRAL, ISOLDE, SPES, EURIOSOL, CARIBU Good Beam quality (π mm-mr vs. 30 π mm-mr transverse) Small beam energy spread for fusion studies Can use chemistry (or atomic physics) to limit the elements released High beam intensity leads to 100x gain in secondary ions Not adapted for short life time isotope production F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 5

Facility for Rare Isotope Beams in the world F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 6 In-flight production ISOL production ISOL production using proton beam (In operation – upgrade or construction – project) 600 MeV – 4 mA TRIUMF-ISAC 500 MeV – 100 µA IBS RISP 70 MeV- 1 mA SARAF 40 MeV – 5 mA HIE-ISOLDE 1.4 GeV– 6 µ A SPES 40 MeV – 20 µ A EURISOL 1 GeV – 100 µ A ISOLDE 1.4 GeV– 2 µA IGISOL 30 MeV – 100 µA

 Determining the correct target material, target geometry and ion source for a particular beam requires careful development and study ISOL Method F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 7 Projectile ProductionIonisationDiffusionEffusionSelectionAcceleration pps 36 Ar 18+ Target Source 176 pps 32 Ar pps 32 Ar 7+ Spectrometer Post Accelerator Path of an atom travelling out of a foil target to the ion source (RIBO code, (Santana-Leitner, 2005))

Challenges for RIB Production with ISOL Method F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 8 ProductionDiffusionEffusionIonisation Beam stopped in the target: manage power deposition and cool down the target. Target container has to dissipate the power from target to an external power sink Need to keep the target material uniformly at high temperature: need to heat the target Target material sintering leads to large grain formation, not good for fast diffusion release Depends on RIB, need of high surface temperature of the transfer line or cold temperature pipe (for a good selectivity) Target material evaporation lead to high pressure, not good for ion source Maximize the range in the target Multi disk target (but increase target size) Compact target Need to minimize distance target-ion source Refractory metal, carbide, oxides Oxide has usually lower operating temperature Target material evaporation lead to high pressure, not good for ion source Container material needs to be compatible with target material If water cooling, risk of sudden oxidation of target at high temperature when crack formation

 Criteria for target material Production rate »Large cross section Physical properties »Low density »Diffusion coefficient »Highest possible operating temperature »High emissivity and thermal conductivity »High permeability to the effusion of the isotopes produced Chemical properties  Target geometry Multi-disk target »Target temperature must be uniform over the whole target »Thin disks help for diffusion Molten metal/salt target »Higher density but need to manage higher power density in the target »Fast evacuation of irradiated molten metal (t~100 ms) to minimize decay losses of short lived Isotopes 2 step target ISOL Target Requirements to Maximize the Production F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 9

 Thermo-mechanical challenge High power density  High thermo-mechanical stress High temperature  Creep and material evaporation/sublimation/sintering Pulsed beams / rotating targets / rotating beams  Fatigue, thermal shocks and shock waves in material Molten metal/salt target  Corrosion and Cavitations  Radiation damage challenge Irradiations induce changes of physical properties and decrease target performance »Thermo-mechanical properties  thermal conductivity, tensile and flexural strength »Electronic properties  Resistivity »Structural properties  microstructure and dimensional changes, swelling »Radiation enhance creep and corrosion  Need to have reliable system and deliver a constant intensity over time ISOL Target Limited lifetime F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 10

 Development of new material is necessary to sustain increasing power deposition in target and radiation damage  Very few target materials can sustain high power deposition  Best target material are: Refractory metals (Ta, Nb, Mo, W) Carbides Oxides, have lower operating temperature  RIB production demands for other type of target material Na, Mg and Al isotopes production for nuclear astrophysics experiments demand high proton intensity on carbide target material, SiC U target > 50% of the RI beam time.  Need to improve the target material properties Example : overall thermal conductivity »Composite target ISOL Target Improving lifetime F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 11 NIMB 317 (2013) 385 SiC UCx

 TRIUMF-ISAC (SiC, TiC, ZrC, UC, Ta, Nb, NiO, Nb5Si3, Al2O3)  ISOLDE (UC 2, SiC, Pb, Ta, Ti, MgO, CaO,...)  HIE-ISOLDE (UC 2, SiC, Pb, Ta, Ti, MgO, CaO,...)  SPES (Uc x )  IBS-RISP (UC 2 ) Target concepts for RIB Solid Multi-disk Target Concept F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 12

 Target concept validated with prototype and off-line test Solid Multi-disk Target Design Study and Validation F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 13

 Direct target using proton beam ISOLDE »Slow diffusion process  significant decay losses for short-lived isotopes (~ ms) »Difficult heat management when increasing beam power EURISOL »LIEBE Target: Liquid Eutectic Lead Bismuth Loop Target for EURISOL Improved diffusion efficiency (LBE spread in a shower of small droplets) Loop-type design with HEX  good heat management Capability to operate at high beam-powers (~ 100 kW) »Requirements Fast evacuation of irradiated liquid metal to minimize decay losses of short lived isotopes Small droplets (r~100 µm) to reduce diffusion length Sufficient fall time to increase overall diffusion efficiency Target concepts for RIB Liquid Metal target Concept F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 14

 LIEBE Target: Liquid Eutectic Lead Bismuth Loop Target for EURISOL  Target concept optimized through CFX simulation and will be tested with prototype at CERN-ISOLDE Liquid metal Target Design Study and Validation F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 15 D. Houngbo et al., “Development of a liquid Pb- Bi target for high-power ISOL facilities”, NIMB 2016, available on line 4 Feb 2016, doi: /j.nimb Release by diffusion is maximized for spherical shape (droplets) of 100 μm radius

 Two step target using neutron induced fission Less power deposition inside the production target material when using neutron as secondary particles Separate the cooling issues of the converter and the production target »Production target can operate at its optimum temperature RIB production with indirect ISOL target is limited mainly to fission products Key experiments (fundamental symmetries, EDM, …) are requesting RIB species that are not produced using fission mechanism! Need direct target production! 2-step targets provide a path to MW targets  Types of “converter” target are envisaged: Rotating wheel target Stationary cooled target »ISOLDE Liquid metal target (Li, LBE, Hg,…) »SARAF LILIT target »EURISOL Target concepts for RIB Increasing RIB Intensity F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 16

 Advanced proton-to-neutron converter at ISOLDE-CERN Two Step Target using Neutron Induced Fission F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 17 A. Gottberg et al., Experimental tests of an advanced proton-to-neutron converter at ISOLDE-CERN, NIMB 336 (2014) Fig. 7. Efficiency ε=εrel·εoε=εrel·εo for Rb isotopes as a function of the isotope half-lives. The experimental release parameters used in the approximation are: αα = 0.471, λfλf = 1.82 s-1,λss-1,λs = s−1 and λrλr = 57.8 s−1.

 From heavy ion beams Used In-Flight or ISOL methods and direct target Used fragmentation and fission processes of both projectile and target GANIL-SPIRAL, NSCL-FRIB, GSI-FAIR, RIKEN-RIPS  Types of “direct” target are developed: Fixed conical GANIL (1.5 kW) Single slice rotating GSI (7 kW) and RIKEN (22 kW) Multi slice rotating FRIB (100 kW) Proton Beams are not the Unique Beams to Produce RIB (1) F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 18 Air-press. Box Target vacuum chamber double-piped shaft water- cooled disk SPIRAL Super FRS Big-RIPS

 Multi slice rotating graphite FRIB High power capability »Up to 100 kW in a ~ g/cm² »~ MW/cm³ High temperature »Maximum temperature at 1900 ºC »High thermo-mechanical stress Rotating target: 5000 rpm »Temperature variation Fatigue Stress wave through the target Modal analyses and vibration studies Proton Beams are not the Unique Beams to Produce RIB (2) F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 19 Multi-slice target / heat exchanger Shield block Motor Target disk / heat exchanger module

 From electron using photofission ARIEL (Advanced Rare Isotope Laboratory) 2 step targets: production by bremsstrahlung-induced fission of a uranium target  Rotating water-cooled wheel, Pb and Ta converter and UC 2 /C target 274 kW in the converter, 120 kW in HS 66 kW in the target. Proton Beams are not the Unique Beams to Produce RIB (3) F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 20

 Studies of neutron-rich nuclei beyond the doubly magic 132 Sn are of key importance to investigate the single particle structure above the N=82 shell closure and find out how the effective interaction between valence nucleons behaves far from stability In-Target Production Yield Example with 132 Sn F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 21 TRIUMF- ISAC CERN- ISOLDE IBS-RISPLNL-SPESEURISOLARIELFRIB pppppe-U Energy [MeV] Intensity [ µA] , ,0005,000 Power in target [kW] In-target Production yield 132 Sn [pps] 5e10 to 1.5e11 for 10 μA ~1e10 (6e8 delivered) ~2e91.6e9 0.5 GeV 3.9e91.4e7* Normalized in target production yield [pps/ µA] 5e9 to 1.5e10 4e92e68e63e93.9e53e3 * * Already accelerated!

 Each facilities have their own specificities and are complementary  Contrary to other high power target, the ISOL targets have to operate at the optimum temperature to speed the release of isotopes Temperature must be uniform over the whole target, Target is couple to the ion source, must avoid pressure overload, Cold transfer tube for volatile species only help.  New techniques were developed to reach high power beam on ISOL target Target material capable of operating at very high power deposition  Indirect ISOL target method allows to separate the cooling problem of the converter and the ISOL target Can reach higher power using secondary neutrons »But radioactive ion beams limited to fission products  New target concepts for high power direct ISOL are being proposed Liquid metal, LBE, salt Powder flow  In-flight method and other primary beams could provide high intensity RIB Summary F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 22

Thank you for your attention F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 23

Backup Slides F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 24

F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 25

High Power Target Technology, Slide 26F. Pellemoine, February Proton Driver Efficieny Workshop Static targets Rotating single-slice targets Rotating multi-slice targets Liquid Li targets PSI RIKEN FRIB FRIB kW

 EURISOL Final Report of the EURISOL Design Study ( ) A DESIGN STUDY FOR A EUROPEAN ISOTOPE- SEPARATION-ON-LINE RADIOACTIVE ION BEAM FACILITY November 2009, Edited by John C. Cornell Published by GANIL B.P , Caen cedex 5, France September, 2009 Target concepts for RIB New proposal facilities F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 27

 MYRRHA: Multi-purpose Hybrid Reactor is conceive as an accelerator driven system (ADS). Use fast neutron spectrum from spallation Accelerator »Superconducting proton LINAC »High power LINAC: 600 MeV: 4 mA: CW »Ideal for isotopes production on-line To verify the sub-criticality of the reactor, short proton beam interruption (200 μS). can utilize 100 to 200 μA proton beam in ~ CW » Possible extension of the proton beam energy to 1.0 GeV Target concepts for RIB New proposal facilities F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 28

Target concepts for RIB IBS-RISP F. Pellemoine, February Proton Driver Efficieny Workshop, Slide 29