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Cryogenic ion catchers using superfluid helium and noble gases

Cryogenic ion catchers using superfluid helium and noble gases. Sivaji Purushothaman KVI, University of Groningen The Netherlands. Content. Introduction Superfluid Helium Cryogenic gas catchers Off-line On-line Summary Future plans. T (K). T (K).  (mg/cm 3 ).  (mg/cm 3 ).

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Cryogenic ion catchers using superfluid helium and noble gases

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  1. Cryogenic ion catchers using superfluid helium and noble gases Sivaji Purushothaman KVI, University of Groningen The Netherlands

  2. Content • Introduction • Superfluid Helium • Cryogenic gas catchers • Off-line • On-line • Summary • Future plans

  3. T (K) T (K) (mg/cm3) (mg/cm3)  (rel.)  (rel.) 1 bar He gas    1 bar He gas    1 bar He gas    liquid He    superfluid He    High density at low temperature et Impurities get frozen out !!!

  4. stop high-energy radioactive ions in superfluid helium  snowballs room T vacuum  transport to the surface by electric fields vapour extraction across the surface into the vapour region electrodes   transport to a vacuum, room-temperature region 1-2 K liquid  Cold RIBs from superfluid helium: concept N. Takahashi et al. extraction across the surface into the vapour region trivial

  5. -decay detection ~ 100 keV 219Rn 4.0 s  223Ra He gas 11.4 d 215Po  1.8 ms  5-6 MeV 211Pb 36 m 223Ra source  223Ra: source of 219Rn ions 211Bi 2.2 m  207Tl 4.8 m  207Pb -decay recoil ion source ranges in LHe recoil: 0.5 m : 500 m

  6. W.X. Huang et al., NIM B 204 (2003) 592 N. Takahashi et al., Physica B 329 (2003) 1596 W.X. Huang et al., Europhys. Lett. 63 (2003) 687 We go for low temperature conflicting temperature requirements How to extract snowballs at low temperature ?

  7. alpha detector LN2 dewar Detector holder foil LHe dewar Collector foil 5 cm 2 3 4 0 1 1 K pot electrodes Guiding electrodes SF He cell Focusing electrode Bottom electrode Source Electric-field assisted extraction up to 1200 V/cm no enhanced extraction

  8. NiCr thin film (140 ) alpha detector Al foil -200 V 223Ra 540 V NiCr heater electrode 520 V fixing hole quartz substrate current pulse Evaporation by second sound Second sound - heat wave without a pressure wave SF helium cell configuration heater design

  9. square current pulse to the second sound heater width: 50 s period: 500 ms Release of ions by evaporation 219Rn released from the surface and transported to the foil 1.05K 219Rn trapped at the surface 7.2(6) % extraction efficiency if thermal motion only: 0.04 % few % overall efficiency

  10. 1 bar at room temperature helium neon argon transport of 219Rn alpha detector Al foil -200 V electrode 520 V 223Ra 540 V A cryogenic gas catcher • impurities in noble gas ion catchers • limit the performance: • neutralization of ions (near or at thermal velocities) • formation of molecules/adducts • remove impurities • 1) ultra-clean system • UHV compatible • bakeable • helium purification < ppb •  not trivial (esp. large cells) • 2) freezing the impurities

  11. Efficiencies at low temperature P. Dendooven et al., NIM A 558 (2006) 580

  12. 1 K pot 1 K pot Cryostat -350V Cryostat Silicon detector Vacuum can 4 K shield Silicon detector 72 K shield -240V Al foil Vacuum can 4 K shield 72 K shield Al foil -220V Rutherford Scattering beam monitor Guiding electrodes Guiding electrodes -200V Rutherford scattering beam monitor 223 Ra source 250V 223 Ra source Bottom electrode Bottom electrode 250V Plasma region 15 MeV Proton beam cell Beam line cell Online experimental setup (JYFL)

  13. Higher electric field is needed to get maximum efficiency at high beam intensities On-line measurements @  

  14. On-line measurements @ 1035 

  15. On-line measurements @ 10106 

  16. Different behavior of efficiency curve may be due to the high mobility of electrons and low mobility of positive ions at low temperature & Re-ionization by beam @   @ 1035  @ 10635 

  17. Summary of the data

  18. Recombination loss - f M.Huyse et al., NIMB, 187, 2002, Pages 535-547 Ramanan, G.; Freeman, Gordon R., Journal of Chemical Physics, 93, 1990, 3120

  19. Efficiency vs. Recombination loss

  20. Off-line Measurements for different pressures and temperatures

  21. Summary • Evidence for 2nd sound assisted extraction from superfluid helium • Cryogenic gas catchers work • High beam intensities require high electric fields

  22. Near future plans • Off-line test of second sound assisted extraction from superfluid helium • On-line test of cryogenic gas catcher using radioactive ion beams • Transport of ions to high vacuum, room temperature region

  23. Collaborators • Juha Äysto (JYFL, Jyväskylä) • Peter Dendooven (KVI, Groningen) • Kurt Gloos (University of Turku) • Takahashi Noriaki (Osaka Gakuin University) • Heikki Penttilä (JYFL, Jyväskylä) • Kari Peräjävi (JYFL, Jyväskylä) • Sami Rinta-Antila (JYFL, Jyväskylä) • Perttu Ronkanen(JYFL, Jyväskylä) • Antti Saastamoinen (JYFL, Jyväskylä) • Tetsu Sonoda (JYFL, Jyväskylä)

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