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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

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

   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

   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:
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:

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