SINBAD ABSTRACT NEA-1552/15
High Energy Neutron Spectra Generated by 590-MeV Protons on a Thick Lead Target
1. Name of Experiment:
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High Energy Neutron Spectra Generated by 590-MeV Protons on a Thick
Lead Target (1979)
2. Purpose and Phenomena Tested:
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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:
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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:
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None
7. Author/Organizer
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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:
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Unrestricted
9. References:
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[1] Georgia Tech MCNPX Benchmarking Homepage:
http://www-rsicc.ornl.gov/pending_benchmarks/GTECH_ACCELERATOR/index.html
[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:
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DETAILED FILE DESCRIPTIONS
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Filename Size[bytes] Content
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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
