Bachelor Project
Investigation of neutron moderators with spherical voids
This is the web page connected to the bachelor project of Mads Bertelsen and Pia Jensen from the Niels Bohr Instutute under the University of Copenhagen. Here it is possible to download the project, the source codes, and some of the figures from the project with larger quality. The download section is at the bottom of this page.
The sph1 moderator used during the experiment.
Introduction
The project was a study of moderator geometry, working with both theory, simulation and experiments. A simple simulation was written in order to model a box neutron moderator with a concave void, investigating the flux increase from the void, as compared to the flux from a similar flat box moderator. A gain of about 3.5 was found in both the experiments and the simulation, after addition of absorption in the simple model.
Regular downloads
Below is the report, in different file formats, all the source codes shown in the report, and the measurements taken during the experiment.
| Description | Download links |
|---|---|
| Project report | PDF (1.50 MB), PS (42.4 MB), DVI (3.73 MB) |
| Source code: Simulation | ZIP (16.0 KB) |
| Source code: Analyser program | ZIP (8.89 KB) |
| Source code: MatLAB functions | ZIP (15.4 KB) |
| Measurements from the experiment | ZIP (1.51 KB) |
| Project report over later work | PDF (580 KB) |
We have given speeches about the project several times, and the used slides can be downloaded from below (in order of appearances).
| Description | Download links for slides |
|---|---|
| ESS simulation group meeting (11.01.2011) | PDF (829 KB) |
| Defence of project (Mads) (17.02.2011) | PDF () |
| Defence of project (Pia) (17.02.2011) | PDF (1.05 MB) |
| ECNS conference talk (Mads) (19.07.2011) | PDF (6.79 MB) |
Figure downloads
Below are first the most important figures to see in large resolution. Simply clicking the thumbnail brings you to the larger image. Note that there are links to these images in the table below as well (and to MatLAB FIG files for some of them).
 1 mm over flat |
 13 mm over flat |
 25 mm over flat |
 37 mm over flat |
 1 mm over sph2 |
 13 mm over sph2 |
 25 mm over sph2 |
 37 mm over sph2 |
 1 mm over sph1 |
 13 mm over sph1 |
 25 mm over sph1 |
 37 mm over sph1 |
Below are all the figures shown in the report (except the flow-charts), saved in high resolution PNG files. Some of the figures can also be downloaded as MatLAB FIG files, which are plots that can be opened in MatLAB and seen as if you plotted them yourself.
| Number | Description | Download links |
|---|---|---|
| 2.1(a) | Scattering coordinate system definition | PNG (64.2 KB) |
| 2.1(b) | Rotation of scattering coordinate system | PNG (78.8 KB) |
| 2.2(a) | Distribution of theta | PNG (35.5 KB) |
| 2.2(b) | Distribution of alpha | PNG (64.3 KB) |
| 2.3 | Alpha as a function of theta and theta' | PNG (39.4 KB) |
| 2.4 | Illustration of the "source volume" | PNG (68.0 KB) |
| 2.5 | Illustration of the focus effect | PNG (61.3 KB) |
| 3.2(a) | Neutron intersecting void | PNG (30.0 KB) |
| 3.2(b) | Neutron ending in void | PNG (32.1 KB) |
| 3.3 | The mirror routine | PNG (23.1 KB) |
| 3.4(a) | Flux 1 mm over flat moderator | PNG (786 KB), FIG (30.6 KB) |
| 3.4(b) | Flux 1 mm over sph2 moderator | PNG (790 KB), FIG (31.4 KB) |
| 3.4(c) | Flux 1 mm over sph1 moderator | PNG (806 KB), FIG (31.9 KB) |
| 3.4(d) | Flux 13 mm over flat moderator | PNG (819 KB), FIG (37.4 KB) |
| 3.4(e) | Flux 13 mm over sph2 moderator | PNG (814 KB), FIG (38.4 KB) |
| 3.4(f) | Flux 13 mm over sph1 moderator | PNG (846 KB), FIG (39.3 KB) |
| 3.4(g) | Flux 25 mm over flat moderator | PNG (839 KB), FIG (39.2 KB) |
| 3.4(h) | Flux 25 mm over sph2 moderator | PNG (838 KB), FIG (40.2 KB) |
| 3.4(i) | Flux 25 mm over sph1 moderator | PNG (871 KB), FIG (41.3 KB) |
| 3.4(j) | Flux 37 mm over flat moderator | PNG (853 KB), FIG (39.6 KB) |
| 3.4(k) | Flux 37 mm over sph2 moderator | PNG (861 KB), FIG (40.4 KB) |
| 3.4(l) | Flux 37 mm over sph1 moderator | PNG (895 KB), FIG (41.7 KB) |
| 3.5(a) | Divergence diagram | PNG (35.6 KB) |
| 3.5(b) | Divergence calculation | PNG (62.9 KB) |
| 3.6(a) | Divergence of neutrons from sph1 void | PNG (86.5 KB), FIG (10.0 KB) |
| 3.6(b) | Divergence of neutrons from sph2 void | PNG (87.3 KB), FIG (10.0 KB) |
| 3.7(a) | r_old's from flat moderator | PNG (210 KB), FIG (263 KB) |
| 3.7(b) | r_old's from sph1 moderator | PNG (248 KB), FIG (272 KB) |
| 3.7(c) | r_old's from sph2 moderator | PNG (230 KB), FIG (267 KB) |
| 4.1 | Moderator wood box | PNG (94.0 KB) |
| 4.2 | Neutron counter electronics | PNG (162 KB) |
| 4.3 | Measured data | PNG (80.6 KB), FIG (12.8 KB) |
| 5.1 | Energy distribution from primary moderator | PNG (90.6 KB) |
| 5.2 | Measured data and simulated data | PNG (123 KB), FIG (20.4 KB) |
| 5.3 | Neutron scalar flux for two cases | PNG (116 KB) |
| 5.4 | Measured data and simulated data w./w.o. abs. | PNG (161 KB), FIG (28.7 KB) |
| F.1 | Neutron detector and housing | PNG (120 KB) |
| F.2(a) | Exact measurements of flat moderator | PNG (54.7 KB) |
| F.2(b) | Exact measurements of sph1 moderator | PNG (98.1 KB) |
| F.3 | Overview of radioactive source | PNG (219 KB) |
| G.1(a) | r_old's from flat moderator (more energies) | PNG (306 KB), FIG (228 KB) |
| G.1(b) | r_old's from sph1 moderator (more energies) | PNG (307 KB), FIG (226 KB) |
| G.1(c) | r_old's from sph2 moderator (more energies) | PNG (309 KB), FIG (227 KB) |
| G.2(a) | Measured data and simulated data | PNG (123 KB), FIG (20.4 KB) |
| G.2(b) | Measured data and thermal simulated data | PNG (125 KB), FIG (20.5 KB) |
| G.2(c) | Measured data and simulated data w. absorption | PNG (131 KB), FIG (20.4 KB) |
| G.3 | Overview of the Farnsworth-Hirsch fusor | PNG (146 KB) |
| G.4(a) | Typical short path of a neutron from the simulation | PNG (112 KB) |
| G.4(b) | Typical long path of a neutron from the simulation | PNG (124 KB) |
| H.2 | Scattering cross section data from NNDC | PNG (133 KB) |
Photographs from the experiments
Finally, during the project several photos were taken, to document all the fun we had. These are shown below with small explanations. For larger size images, simply click the thumbnails.
The paraffin wax for the moderators was melted over water bath.
An image of the flat moderator.
The void in the sph1 moderator was carved out by hand, using clay tools.
View of the finalized sph1 moderator.
The radioactive neutron source used for the experiment.
A view inside the iron barrel of the neutron source. The aluminium tubes are visible.
The detector and the used boron plastic housing.
Measurements underway.