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NUSTAR-5 Design and construction of a superfluid-helium stopping cell

NUSTAR-5 Design and construction of a superfluid-helium stopping cell. Involved institutes: * JYFL, Jyväskylä * GSI * KVI (not as contractor). Objective.

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NUSTAR-5 Design and construction of a superfluid-helium stopping cell

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  1. NUSTAR-5 Design and construction of a superfluid-helium stopping cell Involved institutes: * JYFL, Jyväskylä * GSI * KVI (not as contractor) NUSTAR-5, C. Scheidenberger

  2. Objective Design of a cell, operated with superfluid helium, for the stopping of energetic radioactive ion beams. Tests and performance study with a prototype using radioactive beams available in Jyväskylä alpha detector Detector holder foil Collector foil 5 cm 2 3 4 0 1 electrodes Guiding electrodes Focusing electrode Bottom electrode Source NUSTAR-5, C. Scheidenberger

  3. Present status (1) alpha detector Al foil -200 V 223Ra 540 V NiCr heater electrode 520 V 219Rn extracted from the surface 7.2(6) % extraction efficiency 219Rn trapped at the surface needs confirmation NUSTAR-5, C. Scheidenberger

  4. Present status (2) • - Proposed stopping cell dimensions may also be • reached using a cryogenic gas catcher (T≤20 K) • * 20 K technically less demanding than <2 K • * ions do not need to cross the boundary between • the liquid- and gas-phases • 2×3 days of beam time used in 2005 • * technical problems in the liquid helium cell tests • * cryogenic helium gas catcher (77 K) tests gave • promising results • freezing out of impurities works technically easier than ultra-pure at room temperature • fundamental upper limit the measured efficiencies are determined by the cross sections NUSTAR-5, C. Scheidenberger

  5. Present status (3) Recent measurements at JYFL overlayed on a compilation of other results Extraction efficiency of helium gas ion catchers as a function of ionisation rate, as presented by D.J.Morrissey at the SMI-06 Workshop, Groningen, the Netherlands, March 27-28, 2006 NUSTAR-5, C. Scheidenberger

  6. Deviation from original workplan 1) Delay: Tests done earlier this year at Jyvaskyla with the cryostat from KVI failed partly due to a technical problem (leak) instead: measurements with the cryogenic gas catcher 2) New concept: Already stressed in January meeting, progress since then, tests in 2007, looks very promising NUSTAR-5, C. Scheidenberger

  7. Outlook on completion KVI: the study of the superfluid liquid-helium catcher will be pursued at KVI (off-line developments aiming at fast and efficient extraction via second sound waves), feasibility has to be demonstrated JYFL: * study of cryogenic gas catcher will be pursued at JYFL, development of a system for on-line tests underway (drawings being prepared, construction starts early 2007) * confirm the off-line results and test the transport of ions from cryogenic cell to vacuum * proposal accepted, beam time in preparation GSI: * beam time request under preparation  program will be finished within ~ 1 year NUSTAR-5, C. Scheidenberger

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