Nuclear Instruments and Methods in Physics Research A 463 (2001) 26–41 The new photoactivation facility at the 4:3 MV Stuttgart DYNAMITRON: setup, performance, and first applications D. Belic a , J. Besserer b , C. Arlandini c , J. de Boer b , J.J. Carroll d , J. Enders e,1 , T. Hartmann e ,F.K . appeler c , H. Kaiser e , U. Kneissl a, *, M. Loewe b , H. Maser a , P. Mohr e , P. von Neumann-Cosel e , A. Nord a,2 , H.H. Pitz a , A. Richter e , M. Schumann c , S. Volz e , A. Zilges e a Institut f . ur Strahlenphysik, Universit . at Stuttgart, Allmandring 3, D-70569 Stuttgart, Germany b Sektion Physik, Ludwig-Maximilians Universit . at M . unchen, D-85748 Garching, Germany c Institut f . ur Kernphysik, Forschungszentrum Karlsruhe, D-76021 Karlsruhe, Germany d Department of Physics and Astronomy, Youngstown State University, Youngstown, OH 44555, USA e Institut f . ur Kernphysik, Technische Universit . at Darmstadt, D-64289 Darmstadt, Germany Received 26 October 2000; accepted 16 November 2000 Abstract At the Stuttgart 4:3MVDYNAMITRON accelerator a new bremsstrahlung irradiation facility was installed for photoactivation experiments to complement the well-established arrangement for systematic photon-scattering studies takingadvantageofthehighphotonfluxesachievableatthishigh-currentaccelerator.Thepopulationordepopulation of isomeric states in low-energy photon-induced reactions ðE g ¼ 0:5–4:0 MeV) can be studied with sensitivities far beyond previous limits. The setup of this facility, its performance, and the absolute calibrations are described in detail. First exemplary results for a test case, the reaction 115 In ðg; g 0 Þ 115m In, are presented and analyzed in combination with data from low-energy photon-scattering experiments ( 115 In ðg; g 0 Þ 115 In). The quality of the results demonstrates the powerful capability of this new installation. # 2001 Elsevier Science B.V. All rights reserved. PACS: 25.20.Dc; 23.20.g; 23.20.Lv; 27.70.þj Keywords: Low-energy bremsstrahlung facilities; Photoactivation; Nuclear resonance fluorescence; Isometric states; 115 In 1. Introduction Investigations of long-lived isomeric states in nuclei have a longstanding tradition in nuclear spectroscopy. The long half-lives of isomers are caused by selection rules for the electromagnetic decaysoftheseexcitedstates.Relativepopulations of isomers in various nuclear reactions often were measured in the 1960’s and 1970’s to extract 1 Present address: NSCL, MSU, East Lansing, MI 48824, USA. *Corresponding author. E-mail address: kneissl@ifs.physik.uni-stuttgart.de (U. Kneissl). 2 Present address: Agilent Technologies Deutschland, D-71034 B . oblingen, Germany. 0168-9002/01/$-see front matter # 2001 Elsevier Science B.V. All rights reserved. PII:S0168-9002(01)00225-X