A novel application of a Penning trap

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Fission product yield measurements with JYFLTRAP

• A novel application of a Penning trap
• H. Penttilä, J. Äystö, V.-V. Elomaa, T. Eronen,
  U. Hager, J. Hakala, A. Jokinen, A. Kankainen, P.
  Karvonen, T.  Kessler, I. Moore, A. Nieminen, S.
  Rinta-Antila, T. Sonoda and the IGISOL group
  http//www.phys.jyu.fi/research/igisol
• Department of Physics, University of Jyväskylä,
  Finland
• V. Rubchenya
• Khlopin Radium Institute, St. Petersburg, Russia
• M. Valentina Ricciardi , S. Lukic, A.Kelic, K-H.
  Schmidt
• GSI, Darmstadt, Germany

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Why fission yield measurement?

• General curiosity
• Learning about the fission process
• Information for needs of RNB facilities and
  nuclear waste transmutation studies
• Experimental independend yields necessary for
  theoretical model developing
• Low energy particle induced fission yields in
  context of EURISOL
• Fission from secondary low energy protons and
  neutrons ? have to be included for realistic
  yield estimation

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Why fission yield measurement with the IGISOL?

• Ion guide is not chemically selective
• IG produces beams of primary reaction products
• IG is fast
• Ions from IG predominantly 1
• A number of fission yield/cross section studies
  have been performed using ion guide
• M. Leino et al, Phys Rev. C 44, 336 (1991)
• P. P. Jauho et al, Phys. Rev. C 49, 2036 (1994)
• H. Kudo et al, Phys. Rev. C 57, 178 (1998)
• L. Stroe et al, Eur. Phys. J. A 17, 57 (2003)

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And why with a Penning trap?

• Counting ions instead of waiting for their decay
  gives a superior efficiency compare to
  relativistic fission (GSI) and unstopped fission
  fragment measurements (eg. Lohengrin)
• High mass resolving power of a Penning trap
  provides unambiguous identification of ions -
  also the stable and long-lived ones!

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Fission yields measurement reaction

• p-induced fission
• Thin target
• Stopping ions in helium, guiding to separator
• Continuous ion stream

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Fission yields measurement isobar selection

• 2) Selecting A with a dipole magnet
• m/q selection
• mass resolving power 300
• Still continuous beam

• 3) Guiding ions to radiofrequency (RFQ) cooler
  trap
• Electrostatic deflector
• 7 mm entrance slit

• 4) Collecting ions to RFQ cooler trap
• Creating bunch
• Adjusting ion rate

5) Shooting ions from cooler to trap
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Mass selective purification and ion counting

• 7) Detecting ions with multichannel plate (MCP)
  detector
• high sensitivity

• 6) Trapping and mass selective manipulation of
  the ions
• MRP up to 160000 in purification trap
• Short cycle used to avoid decay losses
• Typical cycle 300 ms ?MRP 30000

From RFQ
TOF MCP
2nd MCP
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Determining the relative ion rate

• For Zirconium isotopes
• 101Zr rate (ions/second) measured
• Other isotope rate measured
• Ion rates corrected for decay losses
• Ratio gives the relative yield

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Zr isotopes yield in fission
Maximum relative yield normalised to one Blue
line theoretical model in V.A. Rubchenya,
http//www.ganil.fr/ eurisol/Yields-of-n-rich-nucl
ei.pdf
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Mo and Ge yields in fission
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Sn isotopes yield in fission
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Summary

• A novel method utilizing a Penning trap to
  determine the relative, independent, isotopic
  fission yields was successfully tested for 25 MeV
  proton induced fission of 238U at the JYFLTRAP.
  
• Relative independent yields for isotopes of 10
  elements were measured in a 3 days beam time.
• Key elements of method
• IGISOL separates any element in milliseconds
• High mass resolving power of the Penning trap
  gives unambiguous identification of ions
• Counting ions after trap with MCP gives
  ultimate sensitivity.