1. O AK R IDGE N ATIONAL L ABORATORY U.S. D EPARTMENT OF E NERGY 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. O AK R IDGE N ATIONAL L ABORATORY U.S. D EPARTMENT OF E NERGY 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 17,18 F 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. O AK R IDGE N ATIONAL L ABORATORY U.S. D EPARTMENT OF E NERGY 3 Holifield Radioactive Ion Beam Facility 25 MV Tandem Electrostatic Accelerator RIB production Target Oak Ridge Isochronous Cyclotron (ORIC) On-Line Test Facility High Power Target Laboratory Enge Spectrometer Recoil Mass Separator Daresbury Recoil Separator

4. O AK R IDGE N ATIONAL L ABORATORY U.S. D EPARTMENT OF E NERGY 4 Proton-rich Radioactive Ion Beams Seven different targets used Three different ion sources 33 radioactive beams 2m2m HfO 2 for 17,18 F beams CeS on RVC matrix for 34 Cl

5. O AK R IDGE N ATIONAL L ABORATORY U.S. D EPARTMENT OF E NERGY 5 On-line Tests using SiC targets at the OLTF (for the production of 25 Al and 26 Al beams)  15  m diameter SiC fibers  1  m 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. O AK R IDGE N ATIONAL L ABORATORY U.S. D EPARTMENT OF E NERGY 6  Performed tests of SiC fiber target with beams up to 8.5  A  No obvious degradation of target material  25 Al and 26m Al yields up to 10 6 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 Nb 5 Si 3 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) SiC Target Tests at the HPTL

7. O AK R IDGE N ATIONAL L ABORATORY U.S. D EPARTMENT OF E NERGY 7 Pure Ga and In beams  Tests at the OLTF observed GaCl + and InCl + beams from UC target  Added chlorine to the system using CH 3 Cl 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. O AK R IDGE N ATIONAL L ABORATORY U.S. D EPARTMENT OF E NERGY 8 Proton-rich Se beams  Observed proton-rich Se isotopes (70-73, 75, 79)  Positive-ion yields are on the order of 10 5 to 10 6 pps/  A  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. O AK R IDGE N ATIONAL L ABORATORY U.S. D EPARTMENT OF E NERGY 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. O AK R IDGE N ATIONAL L ABORATORY U.S. D EPARTMENT OF E NERGY 10 Laser setup for the initial tests at the HRIBF Nd:YAG Pump laser (60 W, 10 kHZ, 532 nm) Ti:sapphire lasers (supplied by the Mainz group) Laser beam into the hot cavity through the mass-analysis magnet

11. O AK R IDGE N ATIONAL L ABORATORY U.S. D EPARTMENT OF E NERGY 11 Sn Ionization Scheme 120 118 116 122 124 112 114 Cs 286,3317 nm / 3 x 11638,06 cm -1 3427,7 cm -1 IP 0 cm -1 34914,2 cm -1 59231,8 cm -1 59375,9 cm -1 AI 1691,8 cm -1 823,5 nm / 12143,29 cm -1 47235,2 cm -1 811,4 nm / 12324,37 cm -1

12. O AK R IDGE N ATIONAL L ABORATORY U.S. D EPARTMENT OF E NERGY 12 Beam purification by photodetachment in RFQ Ion Cooler Buffer gas Ion beam 10 -6 Torr 10 -4 Torr 10 -1 - 10 -2 Torr DecelerationRe-acceleration RF Quadrupole Laser beam Coˉ: 99.9% neutralized Niˉ: 22% neutralized 90% 56 Coˉ 10% 56 Ni ˉ 1% 56 Coˉ 99% 56 Ni ˉ Y. Liu, J.R. Beene, C.C. Havener, and J.F. Liang, Appl. Phys. Lett. 87, 113504 (2005).

13. O AK R IDGE N ATIONAL L ABORATORY U.S. D EPARTMENT OF E NERGY 13 Elevation View of HPTL

14. O AK R IDGE N ATIONAL L ABORATORY U.S. D EPARTMENT OF E NERGY 14 RIB Analysis Beam Line at the HPTL Object Slits & Diagnostics Image Slits & Diagnostics Target/Ion Source Quad 2 Quad 1 Beam Diagnostics 90° Magnet Diagnostic End Station

15. O AK R IDGE N ATIONAL L ABORATORY U.S. D EPARTMENT OF E NERGY 15 Plans for Target Development at the HPTL  New materials tests with high beam power deposition  SiC and metal silicides (e.g. Zr 5 Si 3, Ta 5 Si 3, Nb 5 Si 3 ) for 25,26 Al beams  CeS for 33,34 Cl and 29,30 P beams  New target geometries  Small incident angle (8 deg.)  Thin liquids (Ge for 69 As and p-rich Se beams)  Thin solids for use with 3,4 He production beams ( Al 2 O 3 → P, SiC → S, C → 15 O)  Effect of rastering the production beam  Increase intensity of 17,18 F beams from HfO 2 (production beam presently limited to 3  A 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 17 F(p,  ) 18 Ne, 18 F(p,  ) 15 O  17 F Beam-on-target is 1 x 10 7 pps – need about a factor of ten improvement We need to significantly enhance the quality (intensity and purity) of the available proton-rich radioactive beams at the HRIBF.

16. O AK R IDGE N ATIONAL L ABORATORY U.S. D EPARTMENT OF E NERGY 16 Plans for Target Development at the HPTL  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. UB 4, ThC x, low-density ThO 2 )  Ion sources  LaB 6 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 Other R&D efforts will focus on improving the quality of the available n-rich beams from actinide targets.