Extraction efficiency and extraction times of the SHIPTRAP gas stopping cell Gleb Vorobjev for SHIPTRAP collaboration, GSI  SMI, 27. March 2006

2 Outline Introduction: Off-line experimental set-up Investigation of the gas cell: Summary SHIPTRAP set-up SHIPTRAP gas stopping cell Extraction times Extraction efficiencies Total efficiency Impurities On-line beam

3 Set-up layout N out / N in = ? 50% 100% 30% N in N out

4 J.Neumayr; PhD- thesis

5 Experimental set-up Features of 223 Ra source: T 1/2 ( 223 Ra)=11.4 d max. activity ~10,000 decays/s available recoil ions 219 Rn +, ( 215 Po + ), 211 Pb +, 207 Tl + characteristic  -decay for identification point-like determine (absolute) extraction efficiency

6 Experimental set-up

7 Extraction time P He = 40 mbar Axial E-field = 5 V/cm linear trend described by mobility formalism P He : (40-100) mbar Axial E-field 10 V/cm Nuclides with T 1/2 >10 ms accessible at SHIPTRAP

8 Extraction efficiency Main losses are due to diffusion Neutralisation < extraction time RF-funnel is less efficient

9 Stopping efficiency

10 Total efficiency measurement

11 Total efficiency (measured on-line) placetest candidateefficiencyextraction fields DC / funnel extraction angle MLL 152 Er  -emitter 8.4 % ± 1.5 %10 V/cm 0o0o GSI 152 Er  -emitter 4.8 % ± 0.7 %10 V/cm 5 V/cm90 o MLL 107 Ag + atomic ions 4.0 % ± 1.0 %5 V/cm 10 V/cm0o0o Measured total efficiencies 4-8%

12 Influence of contaminants Xe Rn Po Pb Bi Tl Pb + Er + Xe Before bake-out After bake-out (24 hours, )

13 On-line regime TOF, 2m 58 Ni + 92 Mo -> 150 Yb* 50 Cr + 58 Ni -> 108 Te *

14 Conclusions Gas cell is fast: nuclides with T 1/2 >10 ms are accessible Extraction efficiency ~ 20 % at 40 mbar Total efficiency ~ 13 % in the range of mbar Diffusion is crucial: higher pressure, stronger axial field needed Neutralisation is slower than extraction Scattered primary beam is not allowed to enter the gas cell

15 SHIPTRAP collaboration GSI / SHIPTRAP D. Ackermann M. Block D. Beck M. Dworschak S. Eliseev F. Herfurth F. P. Heßberger S. Hofmann H.-J. Kluge A. Martín M. Mazzocco W. Quint C. Rauth G. Vorobjev Greifswald A. Chaudhuri G. Marx L. Schweikhard Mainz K. Blaum R. Ferrer C. Weber H. Backe P. Kunz W. Lauth Giessen Z. Di H. Geissel C. Scheidenberger M. Petrick W. Plaß Munich D. Habs V. Kolhinen J. Neumayr M. Sewtz P. Thirolf Former PhD students: G. Sikler, D. Rodríguez, M. Mukherjee, S. Rahaman,... St. Petersburg Y. Novikov