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HRIBF - proton-rich beams

HRIBF - proton-rich beams. Dan Stracener HRIBF Users Workshop November 13, 2009. Outline. Status of proton-rich beams at HRIBF Accelerated beam intensities Targets currently used (what are the limitations?) Enhancements to the quality of p-rich beams at HRIBF

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HRIBF - proton-rich beams

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  1. HRIBF - proton-rich beams Dan Stracener HRIBF Users Workshop November 13, 2009

  2. Outline • Status of proton-rich beams at HRIBF • Accelerated beam intensities • Targets currently used (what are the limitations?) • Enhancements to the quality of p-rich beams at HRIBF • Availability of HPTL/IRIS2 for high-power target development • Larger targets and beam rastering at HPTL/IRIS2 • Effects of the C70 upgrade on the p-rich beams • Higher proton energy and intensity • Higher beam intensities for deuterons and alphas • Increased reliability (allows for more high-power target development) • New beam production capabilities

  3. 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

  4. Accelerated Proton-rich Radioactive Ion Beams * This beam was used for commissioning of the RIB Injector

  5. Additional Proton-rich Radioactive Ion Beams(yields measured at OLTF or HPTL)

  6. Experiments Completed During Recent RIB Campaign(Multi-sample Cs-sputter ion source) 5 experiments – 736 hours of radioactive beam on target

  7. RIB Production Targets • HfO2 fibers (production of 17F and 18F) • Uranium carbide (production of n-rich beams via proton-induced fission) • Molten metals • germanium for production of As, Ga, and Se isotopes • nickel for production of Cu isotopes • Ni pellets (56Ni via (p,p2n) reaction – 56Co contamination) • Cerium sulfide (production of 33Cl and 34Cl) • thin layers deposited on W-coated carbon matrix • Silicon carbide (production of 25Al and 26Al) • fibers (15 mm), powder (1 mm), thin layers on carbon matrix, solid discs • also developing metal silicides (e.g. Nb5Si3 disks) • Aluminum oxide (production of 26Si and 27Si) • thin fibers (6mm) with sulfur added for transport • 7Be, 10Be, 26gAl sputter targets • mixed with copper, silver, or niobium powders

  8. 2mm HfO2 Target for 17,18F Beam Production &

  9. 25Al and 26mAl (SiC target at the OLTF) • 15 mm diameter SiC fibers • 1 mm diameter SiC powder • SiC does not sinter • Maximum operating temperature is 1650 C • 25Al yields were about the same in both targets • Increase yield significantly (x10) by adding fluorine to system and extract as AlF+

  10. SiC Target Tests at the HPTL • Performed tests of SiC fiber target with 54 MeV proton beams up to 9 mA (just over 4 days of irradiation) • 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 • Observed 17F from (p,3a) !

  11. SiC Target Tests at the HPTL • We have conducted on-line tests at the HPTL with SiC disks using a target design that allows for increased radiative cooling • This work is a collaboration with a group from Legnaro (SPES Project) • Normalized yields are less than from the SiC fiber targets but the production beam current limit is somewhat higher so the extracted beam intensities are comparable February, 2007 data

  12. Nb5Si3 targets • Yields of 25Al and 26mAl measured at the HPTL with proton beams up to 7 mA • Motivation: lack of carbon atoms in the system will reduce the chance of forming the AlC molecule, which is quite refractory • Normalized yields were lower than measured with SiC fiber targets, possibly due to high density (and low porosity) of these targets

  13. 34Cl (CeS target at the OLTF) • Thin layer of CeS (5 mm thick) deposited onto a tungsten-coated carbon matrix • same matrix that is used for UC targets • Maximum operating temp. is 1900 C • Used to produce 33Cl and 34Cl beams • 32S(d,n)33Cl (T1/2 = 2.5 sec) • 34S(p,n)34Cl & 34S(d,2n)34Cl (T1/2 = 32.2 min) • Initial on-line tests • measured up to 106 ions/sec/mA of 34Cl+ • no 33Cl observed • extracted from ion source as AlCl+ • very little Al vapor was present in the target • natS used to make target (natural abundance of 34S is 4.2%) • Targets showed no change during on-line test • Ce2S3 cannot be used since it converts to CeS at < 1600 C and has a high vapor pressure of sulfur

  14. target before test target after test Al2O3 target for production of 26Si and 27Si beams target holder (1.5 cm dia. x 7.6 cm) • Max. operating temp. is 1900 C • Tested at 1750 C • Measured yield of 27Si is 2000 ions/sec/mA • Observed as molecular ion (SiS+)

  15. New RIBs delivered to experiments (2009) • Beams of 10Be (T½ = 1.5 x 106 years) and 26gAl (T½ = 7.1 x 105 years) have been accelerated in the Tandem and delivered to experiments • Used a Cs-sputter ion source on IRIS1 to produce negative ions • The cathodes were produced from liquid samples using a technique similar to one used for producing cathodes of 7Be (2003 and 2005) • 3 x1019 atoms (540 mg or 8 mCi) of 10Be in about 20 ml of 1.5M HCl • 2 x 1017 atoms (6.6 mg or 0.2 mCi) of 26gAl 10Be 26gAl

  16. 10Be and 26gAl cathodes for Cs-sputter ion source • Made three 10Be cathodes (used about 10% of sample) • Two cathodes with about 2 x 1017 atoms (one has not been used) • One cathode with about 2 x 1018 atoms • Made two 26gAl cathodes (used about 15% of sample) • Each cathode contained about 1.2 x 1016 atoms • Also produced two cathodes containing 7Be atoms from a 3 GBq sample purchased from Atomki in Hungary • Cathodes had 9 x 1015 and 1 x 1015 atoms of 7Be

  17. Liquid Ge targets for As and Se beams Purchased enriched 70Ge from Russia for production of 69,70As and 72Se 70Ge(p,2n)69As 70Ge(a,2n)72Se Germanium chips are melted (about 1200 C) to form a pellet and inserted into a graphite target holder

  18. Path to improving the p-rich beams • High-power target development • Use the availability and capabilities of the HPTL/IRIS2 to facilitate development of ISOL production targets that can withstand higher production beam currents • Develop larger targets maintain high target temperatures without large thermal gradients • Raster the production across the face of the larger target to increase the production rates without increasing the power density in the target material • Improve the production beam characteristics • Higher proton beam energy from the C70 would increase the production rate in some select cases • Higher production beam currents from the C70 will be used to take advantage of the high-power targets that are developed • Increased driver accelerator reliability will result in not only more beam time available for RIB experiments but also more time available for high-power target development

  19. Target thickness is 0.08 cm A Possible Thin Target Geometry Actual geometry used for liquid Ge target for As beams (1.2 cm dia. x 0.6 cm thick)

  20. RIB Production Target Potential Target Holder and Heater Design Target heater 14” TIS enclosure ORIC

  21. Target irradiated with high power beams The UC/RVC target could not withstand direct irradiation with 42 MeV, 100 A proton beams for longer than 2 seconds

  22. Beam Rastering Capabilities • Demonstrated ability to raster a 1-cm diameter beam over a 5-cm diameter target (2 dimensions) with existing steerers (Tony Mendez) • Made simulations to determine the required raster rate and amplitude (Yan Zhang) • Larger entrance port (4” dia.) into TIS enclosure at HPTL/IRIS2 allows for rastered production beams • Especially important for the p-rich beams where the production targets are often less refractory than UC • HfO2 limited to 3 mA of deuterons (Al2O3 limit is < 1 mA) • Limits for other production targets for p-rich beams need to be experimentally determined

  23. Temperature variations due to beam scanning UC2/RVC target (1.2 g/cc), proton beam 50 MeV, 20 mA Beam scan frequency: 1.67 Hz ( f > 8 Hz for T < 20 K)

  24. proton-rich RIB Production at Low E • Fusion-evaporation reactions produce large cross sections localized in beam energy

  25. Estimates of p-rich beam intensities with upgrades

  26. Estimates of p-rich beam intensities with upgrades

  27. Estimates of p-rich beam intensities with upgrades

  28. New Proton-rich Radioactive Beams(possible with increased energy, intensity, and reliability) • 14,15O from SiC or graphite targets – (a,xn) reactions • 21Na from SiC targets using (p,2a) reaction • 29,30P from Al2O3, SiC, or CeS targets • 30,31S from SiC targets using 4He production beams • 33Cl from CeS targets using 1H or 2H production beams • 67,68As from liquid Ge target – (p,3n) or (p,4n) reactions • Long-lived isotopes (many possibilities) • Irradiate samples using the secondary proton beam • 68Ge (could be produced by irradiating a water-cooled Ga target with a proton beam from the C70 and inserting the sample into a Cs-sputter ion source)

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