BEVALAC Experiment with Nb Ions on Nb & Al Targets
1. Name of Experiment: ------------------- BEVALAC experiment stopping 272 & 435 MeV/nucleon Nb ions on Nb and Al targets. 2. Purpose and Phenomena Tested: ----------------------------- The stopping of high energy Nb ions in Niobium and Aluminum targets has been investigated in the BEVALAC facility of Lawrence Berkeley Laboratory during July 1991. The neutron spectra were measured by the time-of-flight method. 3. Description of source and Experimental Configuration ---------------------------------------------------- The energy of the projectile was 272 and 435 MeV/nucleon for Nb ions stopping in Niobium target and 272 MeV/nucleon for Nb ions stopping in Aluminum target. They were delivered in spills of 1 second every 6 seconds with approximately 3E+05 particles per spill reaching the target. A set of two thin detectors were located in the beam trajectory upstrem of the target. They were used to define valid particles from a coincidence logic. The Niobium target was a 5.08 x 5.08 cm2 square plate 1 cm thick for the higher energy and 0.51 cm thick for the lower energy. The Aluminum target was a 5.08 x 5.08 cm2 square plate 1.27 cm thick. The targets were oriented perpendicular to the beam. All the targets were thick enough to stop the beam. Mass thickness of targets is 8.57 g/cm2 for Niobium with 435 MeV/ nucleon, 4.37 g/cm2 for Niobium with 272 MeV/nucleon and 3.43 g/cm2 for Aluminum. The target was housed inside a rectangular steel scattering chamber with a thin Mylar window 0.25 mm thick in the face of the scattering chamber, directly between the target position and the neutron detectors. The longer dimension of the chamber was perpendicular to the beam axis and big enough to allow neutrons leaving the target to reach the detectors though the Mylar window. Chamber walls were 0.32 cm thick. Pressure inside scattering chamber was at most 1.E-05 Torr. 4. Measurement System: ------------------- Neutron detectors were located outside the scattering chamber at laboratory angles from 3 to 80 deg. The detectors consist in 10.16 cm thick big rectangular slabs of plastic scintillator NE-102 covered with a very thin reflective cover and about 0.1 cm of black adhesive tape. These cover completely the detectors except for the top and bottom faces, where the coupling with the bundle of light guides takes place. These guides couple to their respective photomultipliers. There were 16 detectors, all of them with a height of 101.6 cm and different width, between 2.5 and 50.8 cm and hence different solid angle relative to the target. The centers of the detectors were located at the same height that the center of the target. The values of angular position of each detector, their width and flight path are given in Table 1. In front of each main detector another thin NE-102 detector was located with height and width slightly larger than main detectors and thickness 0.64 cm. The purpose was to reject any charged particle incident on the neutron detector. More details about the detectors and the electronics can be found in Ref. 1. The detectors efficiency was calculated by using the M.C. code by Cecil, Anderson and Madey (Ref. 2). Background neutrons were not measured, instead they were estimated from the analysis of two regions of the time-to-digital converter spectra. 5. Description of Results and Analysis: ------------------------------------ The results are presented in Tables 2 to 7 as double differential neutron yield (energy and angle) in terms of neutron per MeV, per milisteradian and per incident ion. There are only results for 14 detectors since the results from detectors at 40 and 64 deg. are not available. The results for 272 MeV/nucleon Nb ions on Nb target are presented in Table 2 for angles 3 to 24 deg. and in Table 3 for angles 28 to 80 deg. For Nb ions of 435 MeV/nucleon also on Nb target the results are presented in Table 4 for angles 3 to 24 deg. and in Table 5 for angles 28 to 80 deg. Finally the results for 272 MeV/nucleon Nb ions on Al target are presented in Table 6 for angles 3 to 24 deg. and in Table 7 for angles 28 to 80 deg. Integrated yields of neutrons above 20 MeV are presented in Table 8. These numbers represent yields of neutrons over 20 MeV per incident ion and are given for the forward space beyond the target (0-90 deg.) and also for the first 45 deg. and the first 10 deg. 6. Special Features: ----------------- None 7. Author/Organizer: ----------------- Experiment and Analysis: L. Heilbronn, K. Frankel, M.A. McMahan, W.H. Rathbun (Lawrence Berkeley National Laboratory), R. Madey, M. Elaasar, M. Htun, B.D. Anderson, A.R. Baldwin, J. Jiang, D. Keane, A. Scott, Y. Shao, J.W. Watson, W.M. Zhang (Kent State University), W.G. Gonng (MPI), G.D. Westfall and S. Yennello (Michigan State Univ.). Phone (Heilbronn): +1.510.486.4002 Fax(Heilbronn): +1.510.486.6949 e-mail: LHHeilbronn@LBL.gov Compiler of data for Sinbad: P. Ortego SEA, Shielding Engineering and Analysis S.L. Avda. Atenas 75 Las Rozas, 28230 Madrid, Spain Phone: +3491.631.7807 Fax: +3491.631.8266 e-mail: p.ortego@retemail.es Reviewer of Compiled Data I. Kodeli OECD/NEA, 12 bd. des Iles, 92130 Issy les Moulineaux, France e-mail: ivo.kodeli@oecd.org 8. Availability: ------------- Unrestricted 9. References: ----------- [1] L. Heilbronn et al. "Neutron yields from 435 MeV/nucleon Nb stopping in Nb and 272 MeV/nucleon Nb stopping in Nb and Al", Physical Review C, vol. 58, No.6, pp. 3451-3460 (1998). [2] R.A. Cecil et al. Improved predictions of neutron detection efficiency for hydrocarbon scintillators from 1 MeV to about 300 MeV", Nuclear Instruments and Methods in Phys. Res., vol. 161, p. 439 (1979). 10. Data and Format: ---------------- Order Filename Size(kb) Content ----- -------- -------- ------- 1 beval-a.htm 8 This information file 2 beval-e.htm 24 Experimental results 3 prc-58.pdf 1692 Paper in Physical Review 4 nim-161.pdf 838 Cecil paper on detector efficiency SINBAD Benchmark Generation Date: 01/2003 SINBAD Benchmark Last Update: 01/2004