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Variable Energy Cyclotron Centre, Kolkata

Developing irradiation facilities in the Materials Science beamline of the DAE Medical Cyclotron

The high intensity proton beams from the DAE Medical Cyclotron (Energy : 15 MeV to 30 MeV and Current: upto 350 micro-amp) provides a unique facility for radiation damage studies on nuclear materials, as energetic charged particles are useful for simulating the bulk damage induced by fast neutrons. For example 20 MeV protons with 350 microampere current will produce in stainless steel a damage of 2x10-5dpa/sec over a sample thickness of about 0.7mm. This is higher than the damage rate produced in fast reactors (~10-6dpa/sec). Due to the high energy available from this Medical cyclotron, thick samples of the order of 0.5 to 1 mm can be irradiated. This makes the post irradiation investigation of the samples by a variety of bulk techniques like X-ray, Positron lifetime, mechanical property measurements feasible. The main interest will be in studying the irradiation effects in Fast Breeder Reactor structural materials like D9, D9I and ferritic steels. Some of the important studies that will be carried out are (1) Ductile to Brittle Transition in Ferritic Steels, (2) Development of Void swelling resistant steels, (3) Phase Stability under irradiation in advanced austenitic steels etc. Apart from the above utilization for reactor materials, studying basic damage mechanisms will also be of importance for the better understanding of radiation effects in materials. 

Another major area of research that will be carried out in the materials science beam line is the induced radioactivity studies using the proton beam available at the DAE Medical Cyclotron. (1) Thin Layer Activation Analysis of nano coatings, (2) Production of Special Isotopes for use as sources in various experiments like PAS, PACS etc., (3) Study of Mass, Charge and Angular Momentum distribution of fission products in proton induced fission of actinides etc. are some of the experiments that are proposed to be carried out. 

The various experiments to be carried out will require different energies and currents. Taking into consideration the radiological safety, the Materials Science activities will be carried out in two different chambers depending on the energies and currents to be utilized for irradiation (as shown in the diagram). The chamber CH1 will be mainly used for high dose experiments where the currents will be of the order of 200 micro-amp. The low dose experiments up to about 50micro-amp beam current will be carried out at CH2. The development of the irradiation facilities include  

1. Design of general purpose target chamber for irradiation 

2. Development of target cooling facilities using Helium and water

3. Development of target handling facilities for handling high dose samples (including shielding wall arrangement and master-slave manipulator, Pb-cask for sample storage)

4. Safety and control of irradiation experiments