Neutron Depth Profiling
Thermal Neutron Depth Profiling (NDP) facility was set up just behind the neutron guide at HK3. The multidetector spectrometer consists of a large vacuum chamber, automatic target holders and several different data acquisition systems which can be used at the same time. NDP is the nuclear analytical technique available to profile light elements in solids. It utilizes the existence of isotopes of elements that produce prompt monoenergetic charged particles upon capture of thermal neutrons.
From the energy loss spectra of emitted products the depth distributions of light elements can be reconstructed. The NDP method is an excellent tool for studies of numerous problems in solid-state physics (diffusion, sputtering), material science (corrosion), electronics, optronics, life sciences etc. Its applicability and efficiency has steadily expanded.
List of nuclides exploited in NDP analyses
| Nuclide | Natural abundance or activity |
Nuclear reaction | Energy of reaction products | Cross section | Detection limit | |
|
|
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| [atoms/mCi] % | E1 [keV] | E2 [eV] | [barns] | [at/cm2] | ||
| 3He | 0.00013 | 3He(n,p)3H | 573 | 191 | 5326 | 3.1·1013 |
| 6Li | 7.42 | 6Li(n,a)3H | 2051 | 2734 | 94 | 1.8·1014 |
| 7Be* | 2.5·1014 | 7Be(n,p)7Li | 143 | 207 | 48000 | 3.5·1012 |
| 10B | 19.6 | 10B(n,ag)7Li | 1471 | 839 | 3606 | 4.3·1013 |
| 10B | 19.6 | 10B(n,a)7Li | 1775 | 1014 | 230 | 6.7·1014 |
| 14N | 99.64 | 14N(n,p)14C | 584 | 42 | 1.81 | 9.1·1016 |
| 17O | 0.037 | 17O(n,a)14C | 1415 | 404 | 0.24 | 7.1·1017 |
| 22Na* | 4.4·1015 | 22Na(n,p)22Ne | 2247 | 103 | 31000 | 4.7·1012 |
| 33S | 0.76 | 33S(n,a)30Si | 3091 | 412 | 0.14 | 1.2·1018 |
| 35Cl | 75.5 | 35Cl(n,p)35S | 598 | 17 | 0.49 | 3.4·1017 |
| 40K | 0.012 | 40K(n,p)40Ar | 2231 | 56 | 4.4 | 3.8·1016 |
| 59Ni* | 1.3·1020 | 59Ni(n,a)56Fe | 4757 | 340 | 12.3 | 1.4·1016 |
| 209Bi | 100.0 | 209Bi + n -> 210Bi | 0.02 | 1.2·1019 | ||
| 210Bi -> b + 210Po | ||||||
| 210Po -> a + 206Pb | 5300 | |||||
Instrument Parameters
| Beam cross-section | 4 x 60 mm |
| Neutron flux | 1·107 n/cm2s |
| Sample size | 50 - 1000 mm 2 |
| Detector systems: | |
| - standard arrangement (single detector facing the sample) |
4 |
| - sandwich arrangement large angle coincidence spectroscopy (2-dimensional data processing) |
1 |
| - dE-E telescope arrangement | 1 |
| - pulse shape discrimination analysis | 2 |
| Solid angle of the detector-sample system | 0.001% - 0.1% |
| Detectors | PIN photodiode - HAMAMATSU Charged particle detector - CANBERRA |
| Detector areas | 50 - 300 mm |
| Depletion depth | 10 - 100 µm |
| Detection limit | |
| - standard arrangement - N, Cl | 10-3 % at. |
| - He, Li, B | 10-5 % at. |
| - sandwich arrangement - Li, B | 10-8 % at. |
| Depth resolution | 10 - 50 nm |
| Maximum detectable depth interval | 3 - 70 µm |
Spectrometer NDP