Heavy Ions Physics

Allelic loss is an important mutational mechanism in human carcinogenesis. Loss of heterozygosity (LOH) at an autosomal locus is one outcome of the repair of DNA double-strand breaks (DSBs) and can occur by deletion or by mitotic recombination. We report that mitotic recombination between homologous chromosomes occurred in human lymphoid cells exposed to densely ionizing radiation. We used cells derived from the same donor that express either normal TP53 (TK6 cells) or homozygous mutant TP53 (WTK1 cells) to assess the influence of TP53 on radiation-induced mutagenesis. Expression of mutant TP53 (Met 237 Ile) was associated with a small increase in mutation frequencies at the hemizygous HPRT (hypoxanthine phosphoribosyl transferase) locus, but the mutation spectra were unaffected at this locus. In contrast, WTK1 cells (mutant TP53) were 30-fold more susceptible than TK6 cells (wild-type TP53) to radiation-induced mutagenesis at the TK1 (thymidine kinase) locus. Gene dosage analysis c...

BARC has been exploring some of the unique features of silicon detector in a variety of nuclear structure experiment using high energy photons and heavy ions projectiles. Current experimental application makes use of large area silicon detector with depletion thickness of ~150-1000 mum. The low cost silicon detector shows excellent energy and position resolution. In this paper, we discuss the simulation result for silicon detector using SILVACO and the physical mechanism involved in detector operation and one set of mask designing for the silicon radiation detector then we will clarify how these effects set a limit to achievable timing performance.

Arik Posner,1 Nathan A. Schwadron, Thomas H. Zurbuchen, Janet U. Kozyra, Michael W. Liemohn, and George Gloeckler2 Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, USA Received 14 May 2001; revised 15 October 2001; ...

We present a compendium of optocoupler radiation test data including data on neutron, proton and heavy ion displacement damage (DD), single event transients (SET) and degradation due to total ionizing dose (TID). Proton data includes ionizing and non-ionizing damage mechanisms.

Using vibrating sample magnetometery (VSM) 50MeV Li3+ ion irradiation effects on magnetic properties of single crystals of SrGaxInyFe12−(x+ y) O19 (where x= 0, 5, 7, 9; y= 0, 0.8, 1.3, 1.0), are reported. The substitution of Ga and In in strontium hexaferrite crystals ...

Several very large scale integrated (VLSI) devices which are not available in radiation hardened version are still required to be used in spacecraft systems. Thus these components need to be tested for highenergy heavy ion irradiation to find out their tolerance and suitability in specific space applications. This paper describes the high-energy heavy ion radiation testing of VLSI devices for single event upset (SEU) and single event latch up (SEL). The experimental set up employed to produce low flux of heavy ions viz. silicon (Si), and silver (Ag), for studying single event effects (SEE) is briefly described. The heavy ion testing of a few VLSI devices is performed in the general purpose scattering chamber of the Pelletron facility, available at Nuclear Science Centre, New Delhi. The test results with respect to SEU and SEL are discussed.

The strain field generated by 200 MeV Ag14+ ions in Si (001) crystals has been investigated using X-ray topography. By choosing suitable diffraction vectors it has been possible to explore the lattice distortion in the inelastic and elastic loss regions separately. Stationary reflection topographs gave two spatially separated images—one originating from the surface and the other from the region affected by elastic nuclear collisions close to the end of the ion range. The spatial separation of these two images is geometrically related to the depth of this elastic loss region. These topographic findings are compared with TRIM calculations.