Lithium targets for two modes of neutron beam producing are developed.

The first one provides kinematically collimated neutrons via near-threshold ⁷Li(p,n)⁷Be reaction at proton energies of 1.9 MeV. Reflectors, collimator, and moderators are not used in these open geometry conditions. Target will be created as a 2 – 3 m m thick lithium target on the surface of molybdenum disk cooled by liquid metal heat carrier.

In the second mode, therapeutically useful orthogonal neutron beams are produced at proton energy of 2.5 MeV. 100 m m thick lithium target is needed in this case.

Thin target for operation in open geometry near the ⁷Li(p,n)⁷Be reaction threshold, a target for operation with “orthogonal” neutrons at proton energy of 2.5 MeV using collimator-moderator, dynamic target with water cooling, rotating and movable targets have been worked in draft.

The first specimen of neutron production target with liquid metal heat-carrier was made. Steel disk 50 mm in diameter, 3 mm thick, is a proton beam absorber. It is cooled by liquid metal flowing in opposite directions in neighboring channels. A molybdenum plate 0.2 mm thick is diffusely welded on the disk, a proton beam is directed on it. The plate is covered with a layer of lithium several micrometers thick. A system is developed for pumping liquid metal heat-carrier including pump, liquid metal circuit with switching systems, heat exchanger, metal velocimeter and pressure distribution measuring device.

Technique for estimation of tritium accumulation in target materials was developed basing on calculation of spatial energetic density of neutron flow in the target region by Monte-Carlo technique followed by calculation of ⁶Li(n,a )T reaction rate which is the main source for tritium accumulation in target. The accumulation rate was determined to depend essentially on configuration and composition of the materials surrounding the target.

Formation of ⁷Be radioactive isotope was considered. Dependence of gamma activity of lithium target on neutron yield was defined.

Thermal mode of the target was investigated using electron beam up to tens of kW and both water and liquid metal cooling systems.

Design of targets, experimental results on thermal mode investigation, spatial-energy distribution of source neutrons and attendant g , and spatial distribution of the absorbed doze are presented and discussed.

Lithium target; near threshold reaction; liquid metal cooling

Sergey Taskaev, Dr., Budker Institute of Nuclear Physics, 11 Lavrentiev ave., 6300090 Novosibirsk, Russia, Tel: 7 3832 394121, Fax: 7 3832 342163, e-mail: taskaev@inp.nsk.su