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| 2. |
- Dangtip, Somsak, et al.
(författare)
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Description of the Medley Code : Monte Carlo Simulation of the Medley Setup
- 1998
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Neutron-induced charged-particle production, i.e., reactions like (n,xp), (n,xd), (n,xt), (n,x3He) and (n,xa), yields a large - and relatively poorly known - contribution to the dose delivered in fast-neutron cancer therapy. At the The Svedberg Laboratory (TSL) in Uppsala, a project is underway to measure these cross sections with a precision required for clinical use. For this purpose, an experimental facility, MEDLEY, is under commissioning. It consists of eight detector telescopes, each being a Si-Si-CsI detector combination. This general design has been selected because it provides reasonable performance over the very wide dynamic range required to detect particles ranging from 5 MeV a particles to 100 MeV protons. A general problem in this kind of experiments is to characterize the response of the detection system. The MEDLEY code has been developed for this purpose. Experimental studies of these kinds of charged-particle reactions show specific features. Some of these need to be optimized by means of, for instance, computer codes, prior to the measurement if good data are to be achieved. Basically, charged particles loose energy along their paths by interactions with the electrons of the material. Particles with low energy or with high specific energy loss are easily absorbed. Systems, which use thick charged-particle production targets to gain desirable count rate, can then detect only charged particles with enough energy to escape the target. Thus, using a thick target results in a degraded energy resolution, and particle losses. Thin targets are required to provide better resolution, but at the cost of low count rates. Registration of the entire energy of the particles reaching the detection system is also an ultimate goal. However, charged particles can interact with detection materials via nuclear reactions, which could result in other species of particles. From the detection point of view, the primary particles are lost and replaced by new types of particles, which may behave differently from their predecessors. It is well known that charged particles traveling in a medium are deflected by many small-angle scatterings. This so-called multiple scattering can be described with a statistical distribution. The fluctuations in energy loss per step, called energy-loss straggling, are modeled in the same way, i.e., assuming a statistical behavior. To get an acceptable neutron beam intensity, a rather thick neutron production target (2-8 mm) is required. This causes an energy spread of the incident neutron beam. In our case, the spread after a 4 mm thick 7Li target for neutron production is of the order of about 2 MeV. To analyze the data and determine the true double-differential cross sections, the above mentioned effects have to be taken into consideration. We have therefore developed a Monte Carlo code, MEDLEY, in FORTRAN language, to simulate the experimental setup taking all relevant physical characteristics into account. In the MEDLEY code, particles, chosen from a given distribution, are followed through the detection system. The particle distribution is obtained by applying a stripping method to the measured spectrum supplied by a user. When the result from the MEDLEY code is in good agreement with the experimental data, the true double-differential cross sections is obtained. If needed, the correction procedure can be iterated. This iteration is performed until the above condition is satisfied. This report presents the features included in the code, and some results. We compare ourresults with those from others where available.
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| 3. |
- Pomp, Stephan, et al.
(författare)
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A New Facility for Neutron-Induced Fission Studies
- 2003
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Ingår i: Proc. Workshop on the Nuclear Data for Transmutation of Nuclear Waste, GSI, Darmstadt, Germany, 2003..
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 4. |
- Somsak, Dangtip, et al.
(författare)
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Facility for measurements of nuclear cross sections for fast neutron cancer therapy
- 2000
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - 0168-9002 .- 1872-9576. ; 452:3, s. 484-504
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Tidskriftsartikel (refereegranskat)abstract
- A facility for measurements of neutron-induced double-differential light-ion production cross-sections, for application within, e.g., fast neutron cancer therapy, is described. The central detection elements are three-detector telescopes consisting of two silicon detectors and a CsI crystal. Use of ?E-?E-E techniques allows good particle identification for p, d, t, 3He and alpha particles over an energy range from a few MeV up to 100 MeV. Active plastic scintillator collimators are used to define the telescope solid angle. Measurements can be performed using up to eight telescopes at 20░ intervals simultaneously, thus covering a wide angular range. The performance of the equipment is illustrated using experimental data taken with a carbon target at En = 95 MeV. Distortions of the measured charged-particle spectra due to energy and particle losses in the target are corrected using a newly developed computer code. Results from such correction calculations are presented.
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| 5. |
- Söderberg, Jonas, et al.
(författare)
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Correction of measured charged-particle spectra for energy losses in the target : A comparison of three methods
- 2002
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - 0168-583X .- 1872-9584. ; 195:3-4, s. 426-434
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Tidskriftsartikel (refereegranskat)abstract
- The experimental facility, MEDLEY, at the The Svedberg Laboratory in Uppsala, has been constructed to measure neutron-induced charged-particle production cross-sections for (n, xp), (n, xd), (n, xt), (n, x3He) and (n, xα) reactions at neutron energies up to 100 MeV. Corrections for the energy loss of the charged particles in the target are needed in these measurements, as well as for loss of particles. Different approaches have been used in the literature to solve this problem. In this work, a stripping method is developed, which is compared with other methods developed by Rezentes et al. and Slypen et al. The results obtained using the three codes are similar and they could all be used for correction of experimental charged-particle spectra. Statistical fluctuations in the measured spectra cause problems independent of the applied technique, but the way to handle it differs in the three codes.
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| 6. |
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