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

[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