[back to index] [experiment]


MSU experiment with He & C ions on Al target

1. Name of Experiment:
    MSU experiment stopping 155 Mev/nucleon He and C ions on aluminum target (1993).

 2. Purpose and Phenomena Tested:
    An aluminum target was bombarded with He and C ions of 155 MeV/nucleon at
    the National Superconducting Cyclotron Laboratory (NCSL) facility in the
    Michigan State University (MSU) during September 1993. Neutron yields were
    measured by the time-of-flight method.

 3. Description of Source and Experimental Configuration:
    The energy of the projectile is 155 MeV/nucleon for both He and C ions.
    They are delivered in bursts of 1 to 3 nanoseconds width with a period of
    41.6 ns.

    The target is an aluminum cylinder, 13.34 cm long with a diameter of
    1.78 cm. It is coaxial with the beam. At the entrance side there is a
    cylindrical hole 5.08 cm long and 1.59 cm diameter also coaxial with
    the beam in order to minimize the loss of backscattered delta electrons,
    since the number of beam particles is calculated from the total amount
    of charge collected in the target.

    The target is suspended inside a spherical scattering chamber of diameter
    91.44 cm with 3.2 mm thick steel wall. Pressure inside chamber is
    1.E-06 Torr.

 4. Measurement System:
    Neutron detectors in groups of 1, 3 or 7 detectors per position are located
    outside the scattering chamber at laboratory angles of 10, 30, 45, 60, 90,
    125 and 160 deg. at the left side of the incident beam and at angles of -30,
    -45 and -60 deg. at the right side of the incident beam. The origin of the
    angle is taken at the extension of the incident beam (passed the target)
    and the positive angle as counterclock. For a better understanding of their
    position relative to beam axis see Figure 1, taken from Ref. 1.

    Absolute position, flight path and solid angle for each individual detector
    are presented in Table 1.

    The 3 detectors at angle 90 deg. are grouped in a triangle with 2 in the
    base and 1 at the top. The bundles of detectors at 10, 30, 45 and 60 deg.
    are formed by 7 detectors, one in the center and other 6 detectors
    surrounding the central ones at angular pitch of 60 deg. The detectors at
    angles 125, 160, -30, -45 and -60 deg. are individual detectors.

    The dimensions of the detectors are 12.7 cm in diameter and the most 7.62
    cm thick but there are also 5.08 cm thick detectors. There is one 5.08 cm
    thick detector in each bundle of 3 or 7, except at angle 30 deg. where
    there are two of them. The individual detectors are all 7.62 cm thick.

    Each individual neutron detector consists of a liquid scintillator (BC-501
    or NE-213) encased in a cylindrical cell constructed of either glass or

    Other plastic scintillator detectors were placed between the target and
    the neutron detectors to detect any charged particle reaching the main
    neutron detectors. They are referred as veto detectors. They are 12.7 cm
    in diameter and 6.35 mm thick. Their position and flight paths are
    indicated in Table 2.

    The detectors efficiency has been calculated by using the M.C. code by
    Cecil, Anderson and Madey (Ref. 2).

    Background neutrons were measured by interposing cylindrical iron or brass
    bars. The length and diameter of the interposed bars are given in Table 3.

 5. Description of Results and Analysis:
    The numerical results of the experiment are presented in Tables 4 to 7.
    They are expressed as double differential values in neutrons per angle
    unit(msr), per energy(MeV) and per incident ion.

    Table 4 presents the results for He ions at angles 10 to 60 deg.
    Table 5 presents the results for He ions at angles 90 to 160 deg.
    Table 6 presents the results for C ions at angles 10 to 60 deg.
    Table 7 presents the results for C ions at angles 90 to 160 deg.

    In Table 8 the previous results have been integrated with the angle for
    obtaining the total yields for both ions. Also the calculated interaction
    fraction and number of neutrons per interaction are presented.

    The uncertainty due to the procedure used to discriminate neutrons coming
    from  different bursts is estimated in 10 to 15%. Other systematic
    uncertainty due to the detector efficiency calculation is estimated in 10%.
    The systematic uncertainty due to the solid angle is given in Table 1. The
    total systematic uncertainty is estimated in 20 to 25%. The statistical
    uncertainty was of the order of 5% for the spectra at 30 deg.

    The MCNPX model for MSU experiment used by P. Ortego is given in mcnpxmsu3.i,
    and the corresponding results are included in the EXCEL file MSU_MCNPX.xls.
    The results seem acceptable for this type of experiments with very good
    estimation for the evaporation part at 90 deg. and more uncertain results in
    the small angle detectors.

 6. Special Features:

 7. Author/Organizer:

    Experiment and analysis:
    L. Heilbronn, M. Cronqvist, K. Frankel and C. Zeitlin (Lawrence Berkeley
    National Laboratory), R.S. Cary and C.E. Stronach (Virginia State Univ.
    Dept. of Physics), F. Deak, A. Horvath and A. Kiss (Eotvos Univ.),
    A. Galonsky, J. Kruse, R.M. Roningen, J. Wang and P. Zecher (Michigan
    State Univ., National Superconducting Cyclotron Lab.), K. Holabird (San
    Francisco State University), H. Schelin (CEFET-PR), and Z. Seres (KFKI).

    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 155 MeV/nucleon Carbon and Helium
       Stopping in Aluminum", Nuclear Science & Engineering, vol. 132, p. 1 (1999)

   [2] R.A. Cecil et al. "Improved predictions of neutron detection efficiency
       for hydrocarbon scintillators from 1 MeV to about 300 MeV", Nuclear
       Instrumentation and Methods in Phys. Res. vol. 161, p. 439 (1979).

10. Data and Format:


Order Filename     Size(kb)  Content
     ------------- --------- ---------------
  1  msu-abs.htm       9     This information file
  2  msu-exp.htm      10     Experiment Description
  3  msufig1.pdf      17     Plane view of the experiment
  4  mcnpxmsu3.i       6     MCNPX input file (P. ortego).
  5  MSU_MCNPX.xls    45     Results obtained using the above MCNPX input (P. ortego).
  6  nse-132-1.pdf  1237     Paper N. S. and Eng.
  7  nim-161.pdf     838     Paper of Cecil et al.

SINBAD Benchmark Generation Date: 01/2003
SINBAD Benchmark Last Update: 01/2004