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Compton Add-Back Protocols for use with the EXOGAM Array

Compton Add-Back Protocols for use with the EXOGAM Array. Adam Garnsworthy University of Surrey. Methods for improving spectra through reducing the effects of Compton scattering Applied to data from a 8 He radioactive beam experiment. The EXOGAM array.

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Compton Add-Back Protocols for use with the EXOGAM Array

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  1. Compton Add-Back Protocols for use with the EXOGAM Array Adam Garnsworthy University of Surrey Methods for improving spectra through reducing the effects of Compton scattering Applied to data from a 8He radioactive beam experiment

  2. The EXOGAM array 16 Clovers of Compton-suppressed segmented germanium crystals Various configurations to maximize specific features for an experiment Images taken from: http://www.ganil.fr/exogam/

  3. Compton scattering between crystals The Klein-Nishina Formula Polar plot and equation taken from K.S. Krane, Introductory Nuclear Physics, Wiley, 1988

  4. The idea and aims of Add-back • Compton suppression vetoes events – Add-back algorithms reconstruct events • Radioactive beam experiments suffer greatly from background • Increase peak-to-background ratio of reaction gamma-rays

  5. Using the increased positional sensitivity of the segmentation data: Using the centre contact data only: Include hits separately in opposite crystals Add together hits in adjacent crystals Hits in different crystals are only added together if adjacent segments fire Construction of Algorithms • Multiplicity one events – include all gamma-rays • Multiplicity two events – apply conditions:

  6. 8He radioactive beam experiment 208Pb(8He,4n)212Po 8He → 8Li + β- followed by a 981 keV γ-ray 8Li → 7Li + n followed by a 478 keV γ-ray • July 2004, GANIL • Background from decay of beam particles (981 keV) and bremsstrahlung • Only 4 Clovers in the ‘close packed’ configuration

  7. 8He beam spectra Data for the 2+ → 0+ transition (727 keV):

  8. Conclusions and further development • Some 981 keV events are only partly reconstructed due to scattering between Clovers • Timing conditions still to be optimized • Other gating conditions, such as triples, can be used

  9. Thank you to my collaborators N.J. Thompson1, Zs. Podolyák1, P.M. Walker1, S.J. Williams1, G.D. Dracoulis2, G. de France4, G.J. Lane2, K. Andgren1,5, A.M. Bruce6, A.P. Byrne2,3, W.N. Catford1, B. Cederwall5, G.A. Jones1, B. McGuirk7, S. Mandal8 E.S. Paul7, V. Pucknell9, N. Redon10, B. Rosse10, R.J. Senior2 and G. Sletten11 • Department of Physics, University of Surrey, Guildford GU2 7XH, UK • Dept. of Nuclear Physics, Australian National University, Canberra, Australia • Dept. of Nuclear Physics, The Faculties, Australian National University, Canberra, Australia • GANIL, BP 5027, Caen Cedex F-14021, France • Department of Physics, Royal Institute of Technology, S-106 91, Stockholm, Sweden • School of Engineering, University of Brighton, Brighton BN2 4GJ, UK • Department of Physics, University of Liverpool, Liverpool, L69 3BX, UK • GSI, Planckstrasse 1, Darmstadt D-64291, Germany • CLRC Daresbury Laboratory, Warrington, WA4 4AD, UK • Institut de Phsique Nucleaire de Lyon, Lyon, France • Niels-Bohr-Institute, DK-2100 Copenhagen, Denmark

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