Abstract
Gas stopping is becoming the method of choice for converting beams of rare isotopes obtained via projectile fragmentation and in-flight separation into low-energy beams. These beams allow ISOL-type experiments, such as mass measurements with traps or laser spectroscopy, to be performed with projectile fragmentation products. Current gas stopper systems for high-energy beams are based on linear gas cells filled with 0.1–1 bar of helium. While already used successfully for experiments, it was found that space charge effects induced by the ionization of the helium atoms during the stopping process pose a limit on the maximum beam rate that can be used. Furthermore, the extraction time of stopped ions from these devices can exceed 100 ms causing substantial decay losses for very short-lived isotopes. To avoid these limitations, a new type of gas stopper is being developed at the NSCL/MSU. The new system is based on a cyclotron-type magnet with a stopping chamber filled with Helium buffer gas at low pressure. RF-guiding techniques are used to extract the ions. The space charge effects are considerably reduced by the large volume and due to a separation between the stopping region and the region of highest ionization. Cyclotron gas stopper systems of different sizes and with different magnetic field strengths and field shapes are presently investigated.
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References
Ringle, R., et al.: Precision mass measurements with LEBIT at MSU. int. J. Mass Spectrom. 251, 300 (2006)
Bollen, G., et al.: Experiments with thermalized rare isotope beams from projectile fragmentation: a precision mass measurement of the superallowed ß emitter 38Ca. Phys. Rev. Lett. 96, 152501 (2006)
Trimble, W., et al.: Development and first on-line tests of the RIA gas catcher prototype. Nuci. Phys., A 746, 415C (2004)
Wada, M., et al.: These proceedings
Weissman, L., et al.: First extraction tests of the NSCL gas cell. Nucl. Phys., A 746, 655–658 (2004)
Wada, M., et al.: Slow Rl-beams from projectile fragment separators. Nucl. ínstrum. Methods, B 204, 570 (2003)
Weissman, L., et al.: Conversion of 92 MeV/u 38Ca/37K projectile fragments into thermalized ion beams. Nucl. Instrum. Methods, A 540, 245 (2005)
Takamine, A., et al.: Space-charge effects in the catcher gas cell of a rf ion guide. Rev. Sci. Instrum. 76, 103503 (2005)
Facina, M., et al.: These proceedings
Bollen, G., Morrissey, DJ., Schwarz, S.: A study of gas-stopping of intense energetic rare isotope beams. Nucl. Instrum. Methods, A 550, 27 (2005)
Simons, L.M.: The cyclotron trap for antiprotons. Hyperfine interact. 81, 253 (1993)
Katayama, L, Wada, M.: Cyclotron ion guide for energetic radioactive nuclear ions. Hyperfine Interact. 115, 165 (1998)
Sigmund, P., Winterbon, K.B.: Small-angle multiple scattering of ions in the screened coulomb region. Nucl. Instrum. Methods 119, 541 (1974)
Betz, H.-D.: Charge states and charge-changing cross sections of fast heavy ions. Rev. Mod. Phys. 44, 465 (1972)
Woitke, O., et al.: Target ionization and projectile charge changing in 0.5-8-MeV/q Liq+ +He (q=1,2,3) collisions. Phys. Rev., A 57, 2692 (1998)
Tarasov, O., Bazin, D.: LISE++: design your own spectrometer. Nucl. Phys., A 746, 411 (2004)
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Guénaut, C. et al. (2007). The cyclotron gas stopper project at the NSCL. In: Dilling, J., Comyn, M., Thompson, J., Gwinner, G. (eds) TCP 2006. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-73466-6_24
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DOI: https://doi.org/10.1007/978-3-540-73466-6_24
Publisher Name: Springer, Berlin, Heidelberg
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