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

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

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Present status (1)
219Rn extracted from the surface
7.2(6)  extraction efficiency
219Rn trapped at the surface
needs confirmation
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Present status (2)

• - Proposed stopping cell dimensions may also be
• reached using a cryogenic gas catcher (T20 K)
• 20 K technically less demanding than lt2 K
• ions do not need to cross the boundary
  between
• the liquid- and gas-phases
• 23 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

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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
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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
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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