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The CARIBU facility

The CARIBU facility. Guy Savard Argonne National Laboratory & University of Chicago ATLAS Users Meeting May 15-16 2014. Gammasphere. HELIOS spectrometer. CPT mass spectrometer. X-array. CARIBU – Californium Rare Ion Breeder Upgrade.

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The CARIBU facility

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  1. The CARIBU facility Guy Savard Argonne National Laboratory & University of Chicago ATLAS Users Meeting May 15-16 2014

  2. Gammasphere HELIOS spectrometer CPT mass spectrometer X-array CARIBU – Californium Rare Ion Breeder Upgrade Access to n-rich region obtained at ATLAS via fission of the most neutron-rich “available” very heavy nuclei (e.g. 252Cf) • Project goal: Provide neutron-rich radioactive beams to user community • Low-energy • Masses, decay spectroscopy, laser spectroscopy, … • Reaccelerated through ATLAS at up to 15 MeV/u • Single particle structure, gamma-ray spectroscopy, … • Project Description • Gas catcher/RFQ cooler • Source and radiological issues • Isobar separator • ECR Charge-breeder • Diagnostics • Experimental equipment ATLAS Guy Savard, Argonne National Laboratory ATLAS Users Meeting May 15-16, 2014

  3. Neutron-rich beam source: CARIBU “front end” layout Main components of CARIBU • PRODUCTION: “ion source” is 252Cf source inside gas catcher • Thermalizes fission fragments • Extracts all species quickly • Forms low emittance beam • SELECTION: Isobar separator • Purifies beam • DELIVERY: beamlines and preparation • Switchyard • Low-energy buncher and beamlines • Charge breeder to Increase charge state for post-acceleration • Post-accelerator ATLAS and weak-beam diagnostics X-array tape station Guy Savard, Argonne National Laboratory ATLAS Users Meeting May 15-16, 2014

  4. RF (body) RF (cone) CARIBU gas catcher: transforms fission recoils into a beam with good optical properties • Based on smaller devices developed at ANL • Radioactive recoils stop in sub-ppb level impurity Helium gas • Radioactive ion transport by RF field + DC field + gas flow • Stainless steel and ceramics construction (1.2 m length, 50 cm inner diameter) • Fast and essentially universally applicable • Extraction in 2 RFQ sections with μRFQs for differential pumping DC gradient 252Cf He gas To acceleration and mass separator Guy Savard, Argonne National Laboratory ATLAS Users Meeting May 15-16, 2014

  5. Extracted isotope yield at low energy (50 keV) • 1 Ci 252Cf source • about 20% of total activity extracted as ions • works for all species • complementary to uranium fission > than 500 neutron-rich species extracted at > 1/s > 150 whose masses have never been measured Guy Savard, Argonne National Laboratory ATLAS Users Meeting May 15-16, 2014

  6. Selection by compact CARIBU isobar separator M/DM = 14000-20000 @ >70% transmission … still being improved Guy Savard, Argonne National Laboratory ATLAS Users Meeting May 15-16, 2014

  7. Beam Delivery Source / Gas Catcher Isobar Separator • After isobar separation, two options for beam use • Low energy experiments after beam bunching • Mass measurement • Laser Spectroscopy • Beta decay studies • Reaccelerated Beams • Use ECR-1 as charge breeder • Inject ions into ATLAS in high charge state (q/m > 0.15) and energy (~100-200 keV) Guy Savard, Argonne National Laboratory ATLAS Users Meeting May 15-16, 2014

  8. The CARIBU low-energy experimental area • Delivers 1.5 kV to 10 kV beam to experimental stations • Pulsed beams with rates from ~ 50 ms to seconds • Low emittance • Experimental stations: TAPE STATION (installed) X-ARRAY (installed) BPT (installed) CPT (installed) LASER SPECTROSCOPY: After CPT move (end of 2014) • Limited amount of space … removal of Tandem will provide new experimental area Guy Savard, Argonne National Laboratory ATLAS Users Meeting May 15-16, 2014

  9. Mass measurements of neutron-rich nuclides Original Area II 2012 CARIBU 2013 Original Original Area II 2012 • Masses determined via a measurement of the ions’ cyclotron frequency • Can measure the mass with a production rate of ~ 1 ion / s • Mass precision ~ 10-7 to 10-8 (10 -100 keV/c2) for masses approaching the r process • Canadian Penning Trap (CPT) has measured more than 100 neutron-rich nuclides, including more than 70 from CARIBU (including 6 isomers) • ~ 20 had never been previously measured by any technique • Currently reaching isotopes produced at the 10-6 fission branch level • For some nuclei, no prior information on the nuclide existed! J. Van Schelt et al., Phys. Rev. C 85, 045805 (2012) J. Van Schelt et al., Phys. Rev. Lett. 111,061102 (2013) Guy Savard, Argonne National Laboratory ATLAS Users Meeting May 15-16, 2014

  10. Beam Delivery Source / Gas Catcher Isobar Separator • After isobar separation, two options for beam use • Low energy experiments after beam bunching • Mass measurement • Laser Spectroscopy • Beta decay studies • Reaccelerated Beams • Use ECR-1 as charge breeder • Inject ions into ATLAS in high charge state (q/m > 0.15) and energy (~100-200 keV) Guy Savard, Argonne National Laboratory ATLAS Users Meeting May 15-16, 2014

  11. ECR Charge Breeder Results In order to accelerate beams in ATLAS the charge-to-mass ration (q/m) must be raised to >1/8 (depending on the desired energy). Best breeding efficiencies: 11-16% for all gases, solid, & RIBs. Rate and Efficiency for Mass 142/25+, 129Xe25+ and 133Cs26+ as function of Voltage difference between ECRCB & 1+ source Guy Savard, Argonne National Laboratory ATLAS Users Meeting May 15-16, 2014

  12. 208Pb DT12 144Ba/Nd 180Hf 72Ge  144Nd: 2+ 144Ba: 2+ 144Ba: 4+ Counts 180Hf: 4+ 144Nd: 4+ 144Ba: 6+ Eg (keV) First Coulomb excitation measurements with CARIBU beams • First Coulex with 141Cs – two goals: 1. Demonstrate feasibility & study backgrounds from stable beam contamination 2. Measure B(E2) of the 11/2+ state in 141Cs • Improved system to study 144Ba • Use CHICO to detect recoil and provide kinematic selection and better Doppler correction • Measure B(E2) and B(E3) to study onset of octupole deformation 600-MeV 141Cs + 208Pb (50 mg/cm2) Same 144Ba experiment running now with GRETINA/CHICO2. Statistics in 1 day now higher than obtained in 10 days last year. 650-MeV 144Ba + 208Pb (1mg/cm2) first Digital GS + CHICO2 expt.  Rochester – LLNL – ANL collab. 12 Guy Savard, Argonne National Laboratory ATLAS Users Meeting May 15-16, 2014

  13. Development of CARIBU beams Fall 2012: • RFQ to replace PII x 2 gain Fall 2013: • New cryomodule Winter 2014: • New stronger, thinner source Summer 2014: • MR-TOF installation EBIS Summer 2015: • EBIS to replace ECR: • New low-energy experimental area Expect x 2-3 gain Higher beam purity Guy Savard, Argonne National Laboratory ATLAS Users Meeting May 15-16, 2014

  14. First charge breeding demonstrated with CARIBU EBIS source Courtesy of Clay Dickerson Guy Savard, Argonne National Laboratory ATLAS Users Meeting May 15-16, 2014

  15. New supplemental flow Main gas flow CARIBU gas catcher mods … isolate source • Everything inside the gas catcher is painstakingly selected and cleaned to maintain gas purity … except the source and milkjug. They come from the hot cells, we can’t even look at them, and we take what we get. Need to make us more independent of this crap: • Separate catcher into 2 gas flow zones so that “crap” from source does not contaminate the rest of the gas catcher 252Cf Guy Savard, Argonne National Laboratory ATLAS Users Meeting May 15-16, 2014

  16. Contamination at A=108 versus separator resolution R = 5000 R = 10000 R = 20000 R = 40000 Tc Mo Rh,Ru Nb Guy Savard, Argonne National Laboratory ATLAS Users Meeting May 15-16, 2014

  17. buncher Better mass resolution • Many experiments require better resolution than even the 20000 we can reach with the isobar separator • need different technology for that  MR-TOF can yield above 100000 mass resolution with good transmission  building a device to go in by the end of summer -goal > 40000 with > 50% transmission Guy Savard, Argonne National Laboratory ATLAS Users Meeting May 15-16, 2014

  18. Status • CARIBU facility is operational • First RIB facility based on a gas catcher … it works. Over 500 neutron-rich isotopes available at low energy • Over 80 different neutron-rich radioactive isotope species have been used for experiments in the last years • Low-energy program in full swing with experiments approved by last three PACs • Reaccelerated beam program initiated with decay experiments and Coulomb excitation experiments at Gammasphere and GRETINA, reaccelerated beam experiments approved in last two PACs • New source ( ~ 1.7 Ci) just installed. First experiment with new source (to GRETINA) is ongoing. Next ATLAS/CARIBU PAC will be held in early summer 2014 (call for proposals expected soon). Will accept proposals for all ATLAS/CARIBU beams and the second part of the GRETINA campaign. Guy Savard, Argonne National Laboratory ATLAS Users Meeting May 15-16, 2014

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