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High Energy Neutron Spectra Generated by 590-MeV Protons on a Thick Lead Target

 1. Name of Experiment:
    High Energy Neutron Spectra Generated by 590-MeV Protons on a Thick
    Lead Target (1979)

 2. Purpose and Phenomena Tested:
    As part of a feasibility study for a German spallation source, a series of 
    experiments [2] were performed in 1979 at the Swiss Institute for Nuclear
    Research (SIN) to determine high energy particle spectra from spallation
    targets. The experiment presented here used a time-of-flight (TOF)
    technique to measure angular neutron spectra resulting from 590-MeV
    protons on a thick lead target. 

 3. Description of the Source and Experimental Configuration:
    A 590-MeV proton beam obtained from the SIN cyclotron was focused to a
    2-cm diameter onto a cylindrical lead target. The experimental arrangement
    is illustrated in Figure 1. The target was composed of twelve cylindrical
    blocks, each 5-cm long and 10-cm diameter, giving an overall length of
    60 cm. The proton current was monitored during the experiment using a
    carbon scatterer placed in the incident proton beam. A pair of thin
    plastic scintillators operated in coincidence was used to detect the
    scattered protons. The monitor was calibrated with respect to the
    absolute proton flux by counting individual protons in the direct beam
    with a third thin plastic scintillator at sufficiently reduced current.
    Measurements of the neutrons emitted from the target were performed at
    30-deg., 90-deg. and 150-deg. via an iron collimator (about 1 m thick).

 4. Measurement System and Uncertainties:
    Two detectors were used for measurements. The main detector was a 
    3-cm thick, 4.5-cm diameter NE213 liquid scintillator employing
    n-gamma pulse discrimination. The distance between the target axis and
    the center of the main detector was 117.3 cm (+- 0.3 cm). A secondary
    detector, a 0.5-cm thick plastic scintillator, was located immediately
    in front of the liquid scintillator. This secondary detector was used
    as counter to remove pulses from charged particles also produced in the
    target. The model of the plastic scintillator is not specified in [1].
    Background measurements were performed by removing the target block
    opposite the collimator entrance.
    The contents for each time bin were integrated and the results divided by
    the NE213 detector efficiency. The efficiency was calculated by using the
    Monte Carlo code of Stanton as modified by Cecil et al. [6]. Then the data
    were scaled by the solid angle subtended by the detector, the dead time
    correction factor, the number of incident protons, and the target average
    surface. In the interpretation of the experimental data, no information
    is provided about the meaning of or the way to determine the so-called
    "target's average surface", which is said to be 12.5 cm squared. 
    No errors were given for the experimental spectrum. However, it was
    specified that during the off-line data processing, there was an error
    associated to the procedure used to separate the response of the high
    energy neutrons from the response of the low energy neutrons in the TOF
    spectra. That error was reported as being small.

  5. Description of Results and Analysis:
    The spectrum of neutrons emitted from the first block (0 - 5 cm) in the 
    target at 90 deg., as presented in Reference 1, is illustrated in Figure 2. 
    The neutron yield is given as neutrons per MeV per incident proton per
    steradian per cm squared. This spectrum was compared to a calculation
    performed at KFA Julich. The calculational method was based on the high
    energy nucleon meson transport code HETC [7]. The comparison of 
    calculation and experiment is illustrated in Figure 3. It was observed
    that the calculated spectrum is much softer than the measured spectrum. 
    The measured spectrum was available only as a plot, see Figure 2 [2].
    For comparison purposes the measured data were extracted from the plot
    and digitized. These data are shown in Table 3.

    More recent benchmark calculation has been performed in ref. [1] by
    MCNPX code.  The new 150-MeV cross section set, LA150, was used 
    in these calculations [5]. The sample input for the MCNPX code is
    given in file mcnpx.inp. A comparison of the calculated spectrum and
    the measured spectrum is shown in Figure 5. It can be seen from
    Figure 5 that the calculation and experiment compare well. The
    largest difference between the calculated and the measured data is
    at lower energies (below 3 MeV).

 6. Special Features:

 7. Author/Organizer
    Experiment and analysis:
    Cierjacks S.*, Raupp F., Howe S.D., Hino Y., Swinhoe M.T., Rainbow M.T.
    and Buth L.:
    *Insitut f. Materialforschung I, Kernforschungszentrum,  Postfach 3640,
    D-7500 KARLSRUHE, Germany

    Compiler of data for Sinbad:
    S. Kitsos
    OECD/NEA, 12 bd des Iles, 92130 Issy les Moulineaux, France
    E-mail: stavros.kitsos@free.fr

    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] Georgia Tech MCNPX Benchmarking Homepage:
    [2] Cierjacks S., Raupp F., Howe S.D., Hino Y., Swinhoe M.T., Rainbow M.T.
        and Buth L.: "High Energy Particle Spectra from Spallation Targets," 
        Proceedings of the 5th Meeting of the International Collaboration on
        Advanced Neutron Sources, Jülich, June 22-26, 1981.
    [3] Tuli J.:  "Nuclear Wallet Cards," National Nuclear Data Center,
        Brookhaven National Laboratory, July 1990.
    [4] Leo W.: "Techniques for Nuclear and Particle Physics Experiments: 
        a How-To Approach," Berlin ; New York : Springer, 1994.
    [5] Chadwick M.B., Young P.G., Chiba S., Frankle S.C., Hale G.M.,
        Hughes H.G., Koning A.J., Little R.C., MacFarlane R.E., Prael R.E.
        and Waters L.S.: "Cross Section Evaluations to 150 MeV for
        Accelerator-Driven Systems and Implementation in MCNPX," 
        Nuclear Science and Engineering, vol. 131, pp. 293, March 1999.
    [6] Cecil R.A., Anderson B.D. and Mady R., Nuclear Instruments and 
        Methods vol. 161, pp. 439, 1979.
    [7] Filges D., Cloth P., Neef R.D. and Sterzenbach G., Contribution 
        to Spallation Source Meeting, Bad Konigstein, March 18-20, 1980. 

10. Data and Format:

        Filename   Size[bytes]   Content
    -------------- ----------- -------------
  1 p590-abs.htm     9.698  This information file
  2 p590-exp.htm     5.321  Description of experiment
  3 p590-cal.htm     5.265  Description of transport calculations
  4 p590-f1.gif     13.821  Figure 1: Experimental arrangement for SIN TOF experiment
  5 p590-f2.gif     59.459  Figure 2: Neutron spectra from the lead target for 590 MeV proton
  6 p590-f3.gif     72.460  Figure 3: Measured and HETC calculated neutron spectra at 90-deg.
  7 p590-f4.gif      4.592  Figure 4: MCNPX neutron spectra emitted at 90-deg.
  8 p590-f5.gif      5.041  Figure 5: Measured and MCNPX calculated neutron spectra at 90-deg.
  9 mcnpx.inp        4,569  Input data for MCNPX calculations
 10 icans-v.pdf  1.075.363  Reference

    Files p590-exp.htm and p590-cal.htm contain the following tables:

      Table 1:      Material Data for Target and Collimator
      Table 2:      Material Data for Detectors
      Table 3:      Experimental Flux of Neutrons Emitted at 90-deg.
      Table 4:      Calculated MCNPX Flux of Neutrons Emitted at 90-deg. 

   Figures are included in GIF format.

 SINBAD Benchmark Generation Date: 12/2004
 SINBAD Benchmark Last Update: 12/2004