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Status of RIB Development at the HRIBF

Status of RIB Development at the HRIBF. HRIBF Workshop – Nuclear Measurements for Astrophysics October 23-24, 2006 Oak Ridge, TN. Dan Stracener Physics Division, ORNL. RIB Development and Testing Facilities. Ion Source Test Facility I (ISTF-1)

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Status of RIB Development at the HRIBF

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  1. Status of RIB Development at the HRIBF HRIBF Workshop – Nuclear Measurements for Astrophysics October 23-24, 2006 Oak Ridge, TN Dan Stracener Physics Division, ORNL

  2. RIB Development and Testing Facilities • Ion Source Test Facility I (ISTF-1) • characterize ion sources (efficiency, longevity, emittance, energy spread, effusion) • photodetachment tests with gas-filled RFQ ion cooler • Ion Source Test Facility II (ISTF-2) • laser ion source • ion source lifetime tests (KENIS – used for 17,18F beams) • On-Line Test Facility (OLTF) • low intensity tests of target and ion source performance (release from target, transport time, ionization efficiency) • compatible with the RIB Injector and results are scaleable • High Power Target Laboratory (HPTL) • target tests with high power beams from ORIC • release measurements with larger target geometries • Facility for preparing target/ion source modules for the RIB Injector (assembly and quality assurance)

  3. Holifield Radioactive Ion Beam Facility 25 MV Tandem Electrostatic Accelerator RIB production Target Oak Ridge Isochronous Cyclotron (ORIC) Enge Spectrometer Daresbury Recoil Separator High Power Target Laboratory Recoil Mass Separator On-Line Test Facility

  4. 2mm Proton-rich Radioactive Ion Beams • Seven different targets used • Three different ion sources • 33 radioactive beams HfO2 for 17,18F beams CeS on RVC matrix for 34Cl

  5. On-line Tests using SiC targets at the OLTF(for the production of 25Al and 26Al beams) • 15 mm diameter SiC fibers • 1 mm diameter SiC powder • SiC does not sinter • Maximum operating temperature is 1650 C • Can increase yield significantly (x10) by adding fluorine to system and extract as AlF

  6. SiC Target Tests at the HPTL • Performed tests of SiC fiber target with beams up to 8.5 mA • No obvious degradation of target material • 25Al and 26mAl yields up to 106 pps as AlF+ • Almost equal amounts of Al+ and AlF+ • Also observed Mg+ and Na+ beams but not as fluoride molecular ions • Will look for AlCl+ molecular ions • Next test will be a Nb5Si3 target • this eliminates the carbon atoms and, possibly, the formation of AlC, which is very refractory • In December, we plan to test a different type of SiC material that can withstand significantly higher temperatures (up to 2000 C instead of 1650 C)

  7. Pure Ga and In beams • Tests at the OLTF observed GaCl+ and InCl+ beams from UC target • Added chlorine to the system using CH3Cl gas • Results of measurements • pure molecular beams of Ga and In isotopes were observed – isobars were below detection threshold • molecular beam intensity depended on the chlorine concentration – yields were 10% to 50% of the atomic beam intensities • The efficiency for XCl+ to Xˉ needs to be measured • Need to investigate the chloride formation as a function of target temperature • Conclusion: contamination of Ga and In beams can be greatly reduced, but at the moment the yields will be lower • Also observed SrCl+ and BaCl+ • Sr beams can also be purified using SrF+ (no neighboring contaminants)

  8. Proton-rich Se beams • Observed proton-rich Se isotopes (70-73, 75, 79) • Positive-ion yields are on the order of 105 to 106 pps/mA • Target: liquid Ge at temperatures from 1000° - 1300° C • Production beam: 66 MeV alphas from the Tandem • The yields of the Se+ beams decreased with increasing target temperature, which suggests a molecular transport mechanism • SeCO+ has been observed at ISOLDE, but we did not see it using this target/ion source combination • Measured a relatively short holdup time at 1000° C – less than 10 minutes • Need to test a thin-layer liquid Ge target at the HPTL

  9. Laser Ion Source Experiments • Laser ion source set up and operated at HRIBF in collaboration with a group from Mainz • Three-step ionization of Sn, Ge, Ni, Cu, and Mn obtained • Autoionization states found for Sn and Ge (higher ionization efficiency) • Frequency quadrupling of the Ti:sapphire used successfully, for the first time, to resonantly ionize Cu atoms • Measured beam emittance of laser-ionized and surface-ionized beams • Measured time profile of laser-ionized beams • Overall LIS efficiencies: • 22% for Sn (compared to 10% reported at ISOLDE) • 3.3% for Ge • 2.7% for Ni • 2.4% for Cu • < 1% for Mn Y. Liu, et al., NIMB 243 (2006) 442.

  10. Laser setup for the initial tests at the HRIBF Laser beam into the hot cavity through the mass-analysis magnet Ti:sapphire lasers (supplied by the Mainz group) Nd:YAG Pump laser (60 W, 10 kHZ, 532 nm)

  11. Cs AI 59375,9 cm-1 IP 59231,8 cm-1 823,5 nm / 12143,29 cm-1 47235,2 cm-1 811,4 nm / 12324,37 cm-1 120 34914,2 cm-1 118 116 286,3317 nm / 3 x 11638,06 cm-1 124 122 Cs 112 114 3427,7 cm-1 1691,8 cm-1 0 cm-1 Sn Ionization Scheme

  12. Buffer gas 90% 56Coˉ 10% 56Ni ˉ Re-acceleration Deceleration RF Quadrupole Ion beam Laser beam 10-1 - 10-2 Torr 1% 56Coˉ 99% 56Ni ˉ 10-6 Torr 10-6 Torr 10-4 Torr Coˉ: 99.9% neutralized Niˉ: 22% neutralized Beam purification by photodetachment in RFQ Ion Cooler Y. Liu, J.R. Beene, C.C. Havener, and J.F. Liang, Appl. Phys. Lett. 87, 113504 (2005).

  13. Elevation View of HPTL

  14. Diagnostic End Station Quad 2 Target/Ion Source Object Slits & Diagnostics Quad 1 Image Slits & Diagnostics 90° Magnet Beam Diagnostics RIB Analysis Beam Line at the HPTL

  15. Plans for Target Development at the HPTL We need to significantly enhance the quality (intensity and purity) of the available proton-rich radioactive beams at the HRIBF. • New materials tests with high beam power deposition • SiC and metal silicides (e.g. Zr5Si3, Ta5Si3, Nb5Si3) for 25,26Al beams • CeS for 33,34Cl and 29,30P beams • New target geometries • Small incident angle (8 deg.) • Thin liquids (Ge for 69As and p-rich Se beams) • Thin solids for use with 3,4He production beams (Al2O3→ P, SiC → S, C → 15O) • Effect of rastering the production beam • Increase intensity of 17,18F beams from HfO2 (production beam presently limited to 3 mA due to target damage) • Increased target diameter by a factor of three should allow an increase in the production beam intensity by a factor of ten without increasing the power density • Important measurements to be made include 17F(p,g)18Ne, 18F(p,a)15O • 17F Beam-on-target is 1 x 107 pps – need about a factor of ten improvement

  16. Plans for Target Development at the HPTL Other R&D efforts will focus on improving the quality of the available n-rich beams from actinide targets. • UC target tests • Proton-induced fission vs. deuteron-induced fission (direct) • Investigate 2-step targets (larger volumes) • Higher density UC targets • Measure release efficiency for short-lived isotopes • Lifetime of high-density targets (e.g. pressed-powder targets) • Actinide target materials (e.g. UB4, ThCx, low-density ThO2) • Ion sources • LaB6 ion source to make pure Br and I beams (investigate long-term poisoning with high intensity production beams) • Close-coupled target to reduce effusion times

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