Tritium targets

The most common sources are based on the 3H(d, n) reaction. Deuterons are accelerated to 150 keV with currents 2.5 mA and strike a tritium target. They produce 2 x 1011 of 14-MeV neutrons/s under these conditions. The neutrons produced are widely used in fast neutron activation analysis for the determination of light elements. The tritium targets are typically metals such as Ti, which have been loaded with titanium tritide. The accelerators are usually small Cockcroft-Walton machines or small sealed-tube devices where the ion source and accelerator structure are combined to produce a less expensive device with neutron yields 108/s. 

It should be noted that commercial neutron generators are also easily adopted to the generation of 2.8 MeV neutrons produced by the 2H(2H,w)3He reaction. In most cases it is merely necessary to replace the tritium target with one containing occluded deuterium. The neutron yield from this reaction is much less than for the D—T reaction and the useful flux is often not much greater than could be obtained by use of isotopic sources. About 35 elements have been found to possess reasonably high (n,n y) or (n,y) cross sections for 2.8 MeV neutrons 41>. Since the 8 most common elements in the earth s crust are not among those readily activated, there is some potential application of 2.8 MeV neutrons in analyses for certain elements in minerals and ores, where major element interferences via 14 MeV activation may be a problem. 

The cross section for the 3H(maximum value at only 107 KeV incident deuteron energy. When thick ( 1 mg cm-2 thick deposit of titanium) titanium-tritium targets are used, however, the neutron yield continues to increase even above 200 KV acceleration potential. This is due to increased penetration of the deuteron beam into the tritium enriched layer. Since the penetration of molecular deuterium ions is less than that for monatomic deuterium ions for the same acceleration potential, accelerators using Penning ion sources require extremely clean vacuum systems to minimize build-up of deuteron absorbing deposits on the surface of the target. 

For application of reaction (17.5), suitable tritium targets have been developed in whieh T is preferably bound in the form of hydrides such as titanium hydride deposited on copper. The targets must be well cooled to suppress escape of T due to heating by the incident deuterons. Neutron shielding is achieved by a block of paraffin, in which the energy of the neutrons is reduced, and by boron as a neutron absorber. 

With tritium targets of 1 Ci (3.7 10 Bq) and deuteron fluxes of about 50mA, neutron yields up to about 5 10 s are obtained. The flux density depends on the distance between the tritium target and the sample. The energy of the neutrons produced by reaction (17.4) is 14 MeV and allows activation by (n,p), (n,y) or (n,2n) reactions with relatively high yields. Most cross sections of (n,2n) reactions are in the... 

Tritium targets are bombarded by accelerated deuterons. Timneling of the Coulomb barrier (see Fig. 13.10) results in a good yield for this reaction even for energies of 0.1 MeV. 

Accelerators provide a variety of nuclear reactions for production of neutrons. Cockcroft-Walton accelerators can generate 14.8 MeV neutrons by accelerating deuterons ( H) onto a tritium target to produce 10 -10 neutrons s Cyclotrons and linear accelerators can produce high-energy neutrons with a broad spectrum of energies in spallation reactions that result from the bombardment of heavy elements by charged particles. 

The neutron source in this experiment consisted of a deuteron beam incident on a tritium target. 

Tritium targets are normally prepared by allowing tritium gas to be absorbed into a thin layer of titanium on a suitable base such as copper. Using this reaction, miniature accelerator tubes have been designed which are small enough to be completely inserted into a reactor. These devices can be operated in the pulsed mode the rate of decay of the neutron flux following a rapid injection of neutrons into the reactor can be measured and used to obtain information on parameters such as the effectiveness of the reactor control system. 

In a neutron generator, deuterons accelerated in a high vacuum to an energy of 100-600 keV bombard a tritium target made e.g. of tritiated titanium on a copper backing. The fusion reaction... 

The photomultipliers are connected to a common HV supply. An additional timer regulates the irradiation time. The irradiation is started by removing a tantalum screen, that intercepts the deuteron beam before it strikes the tritium target, from the beam. 

Ci tritium target (28 mm diameter), 300 nk deuteron beam intensity, 5 s radiation, 30 s counting, 2 s after the irradiation. Under these conditions 1 mg of oxygen corresponds to 70 counts. 

What difference in the initial flux distribution can we observe when using deuterium or tritium targets ... 

The pulsed neutron source consists of a pulsed ion source producing deuterium ions which are accelerated to approximately 100-keV energy. The ions bombard either a deuterated copper target or a tritium target and produce neutrons of about 3.5-MeV energy for the D-D reaction, or about 14-MeV for the D-T reaction. The neutron yield from the D-T reaction is about 100 times that from the D-D reaction. 

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