@article{jagannadham_verghese_butler_2014, title={Thermal conductivity changes upon neutron transmutation of B-10 doped diamond}, volume={116}, ISSN={["1089-7550"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84906861630&partnerID=MN8TOARS}, DOI={10.1063/1.4892888}, abstractNote={10B doped p-type diamond samples were subjected to neutron transmutation reaction using thermal neutron flux of 0.9 × 1013 cm−2 s−1 and fast neutron flux of 0.09 × 1013 cm−2 s−1. Another sample of epilayer grown on type IIa (110) single crystal diamond substrate was subjected to equal thermal and fast neutron flux of 1014 cm−2 s−1. The defects in the diamond samples were previously characterized by different methods. In the present work, thermal conductivity of these diamond samples was determined at room temperature by transient thermoreflectance method. The thermal conductivity change in the samples as a function of neutron fluence is explained by the phonon scattering from the point defects and disordered regions. The thermal conductivity of the diamond samples decreased more rapidly initially and less rapidly for larger neutron fluence. In addition, the thermal conductivity in type IIb diamond decreased less rapidly with thermal neutron fluence compared to the decrease in type IIa diamond subjected to...}, number={8}, journal={JOURNAL OF APPLIED PHYSICS}, author={Jagannadham, K. and Verghese, K. and Butler, J. E.}, year={2014}, month={Aug} }
 @article{reed_reed_jagannadham_verghese_bedair_el-masry_butler_2004, title={Electrical characterization of B-10 doped diamond irradiated with low thermal neutron fluence}, volume={22}, ISSN={["1520-8559"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-4344661941&partnerID=MN8TOARS}, DOI={10.1116/1.1763910}, abstractNote={A sample of 10B isotope doped diamond was neutron irradiated to a thermal fluence of 1.3×1019 neutron cm−2. The diamond sample was cooled continuously during irradiation in a nuclear reactor. 7Li is formed by nuclear transmutation reaction from 10B. Characterization for electrical conductance in the temperature range of 160 K 200 K) and p-type surface conductance at lower temperature (T<200 K). The irradiated sample showed decreasing conductance below 230 K and increasing conductance above 230 K with increasing temperature. Furthermore, the conductance showed a decrease above 400 K followed by an increase above 500 K. The observed behavior below 400 K with increase in temperature is interpreted in terms of compensation of surface p-type carriers by n-type bulk carriers generated from 7Li that is formed by nuclear transmutation...}, number={4}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A}, author={Reed, ML and Reed, MJ and Jagannadham, K and Verghese, K and Bedair, SM and El-Masry, N and Butler, JE}, year={2004}, pages={1191–1194} }
 @article{jagannadham_verghese_butler_2001, title={Neutron transmutation of B-10 isotope-doped diamond}, volume={78}, ISSN={["0003-6951"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0042331197&partnerID=MN8TOARS}, DOI={10.1063/1.1342207}, abstractNote={Diamond samples grown by microwave plasma chemical vapor deposition and doped with 10B have been irradiated under thermal neutron flux of 1013 cm−2 s−1 for 76 h to examine transmutation of 10B to 7Li and the attendant lattice damage to diamond. To prevent graphitization and formation of diamond-like carbon, continuous cooling in water is provided during irradiation. Characterization of the diamond samples using Raman spectroscopy, photoluminescence spectroscopy, and secondary ion mass spectrometry showed that diamond remained crystalline without a major damage. Formation of vacancies due to neutron irradiation is inferred from photoluminescence spectroscopy.}, number={4}, journal={APPLIED PHYSICS LETTERS}, author={Jagannadham, K and Verghese, K and Butler, JE}, year={2001}, month={Jan}, pages={446–447} }
 @article{peplow_verghese_2000, title={Differential sampling applied to mammography image simulation}, volume={135}, ISSN={["0029-5639"]}, DOI={10.13182/NSE00-A2128}, abstractNote={Abstract Differential sampling is a powerful tool that allows Monte Carlo to compute derivatives of responses with respect to certain problem parameters. This capability has been implemented within an in-house Monte Carlo code that simulates detailed mammographic images from two new digital systems. Differential sampling allows for the calculation of the first and all second derivatives of all of the different tallies computed by the code as well as the first and second derivatives of the mammographic image itself with respect to material parameters, such as density and cross sections. The theory behind differential sampling is explained, the methodology for implementation into the imaging code is discussed, and two problems are used to demonstrate the power of differential sampling.}, number={2}, journal={NUCLEAR SCIENCE AND ENGINEERING}, author={Peplow, DE and Verghese, K}, year={2000}, month={Jun}, pages={103–122} }
 @article{peplow_verghese_2000, title={Differential sampling for the Monte Carlo practitioner}, volume={36}, ISSN={["0149-1970"]}, DOI={10.1016/S0149-1970(99)00024-4}, abstractNote={One of the two methods for performing a perturbation calculation using Monte Carlo simulations is by differential sampling. The fundamental theory of differential sampling in Monte Carlo is well-presented in the literature but algorithms for implementation of the theory are not well-documented. The development of a differential sampling scheme and its implementation from the viewpoint of the Monte Carlo practitioner are presented here. Simplified examples of radiation transport and criticality of a multiplying system are used to illustrate the algorithms for implementation. Notes on applying the same schemes to more complex problems are also discussed.}, number={1}, journal={PROGRESS IN NUCLEAR ENERGY}, author={Peplow, DE and Verghese, K}, year={2000}, pages={39–75} }
 @article{peplow_verghese_2000, title={Digital mammography image simulation using Monte Carlo}, volume={27}, ISSN={["0094-2405"]}, DOI={10.1118/1.598896}, abstractNote={Monte Carlo simulations of digital images of the contrast detail phantom and the ACR phantom are presented for two different x-ray digital mammography modalities: a synchrotron mammography system and a next-generation scanning slot clinical system. A combination of variance reduction methods made it possible to simulate accurate images using real pixel dimensions within reasonable computation times. The complete method of image simulation, including a simple detector response model, a simple noise model, and the incorporation of system effects (MTF), is presented. The simulated images of the phantoms show good agreement with images measured on the two systems.}, number={3}, journal={MEDICAL PHYSICS}, author={Peplow, DE and Verghese, K}, year={2000}, month={Mar}, pages={568–579} }
 @article{peplow_verghese_1998, title={Measured molecular coherent scattering form factors of animal tissues, plastics and human breast tissue}, volume={43}, ISSN={["0031-9155"]}, DOI={10.1088/0031-9155/43/9/001}, abstractNote={Photon scattering angular distributions from various animal tissues were measured at two energies of a monochromatic synchrotron x-ray beam. Two plastics and human breast tissue were also measured. From these two measurements, the molecular coherent scattering form factor of each material was extracted. A new data analysis technique that uses Monte Carlo based corrections for air scattering, incoherent scattering and multiple scattering was used. The form factors of the 16 materials are presented in tabular form, suitable for use in computer calculations.}, number={9}, journal={PHYSICS IN MEDICINE AND BIOLOGY}, author={Peplow, DE and Verghese, K}, year={1998}, month={Sep}, pages={2431–2452} }
 @book{verghese_gilligan_1998, title={Nuclear engineering education sourcebook 1998}, publisher={Raleigh, NC: American Nuclear Society, Education and Training Division}, author={Verghese, K. and Gilligan, J.}, year={1998} }
 @article{mayo_verghese_huo_1997, title={Mixed enrichment core design for the NC State University PULSTAR reactor}, DOI={10.2172/319770}, abstractNote={The North Carolina State University PULSTAR Reactor license was renewed for an additional 20 years of operation on April 30, 1997. The relicensing period added additional years to the facility operating time through the end of the second license period, increasing the excess reactivity needs as projected in 1988. In 1995, the Nuclear Reactor Program developed a strategic plan that addressed the future maintenance, development, and utilization of the facility. Goals resulting from this plan included increased academic utilization of the facility in accordance with its role as a university research facility, and increased industrial service use in accordance with the mission of a land grant university. The strategic plan was accepted, and it is the intent of the College of Engineering to operate the PULSTAR Reactor as a going concern through at least the end of the current license period. In order to reach the next relicensing review without prejudice due to low excess reactivity, it is desired to maintain sufficient excess reactivity so that, if relicensed again, the facility could continue to operate without affecting users until new fuel assistance was provided. During the NC State University license renewal, the operation of the PULSTAR Reactor at the State University of New York at Buffalo (SUNY Buffalo) was terminated. At that time, the SUNY Buffalo facility had about 240 unused PULSTAR Reactor fuel pins with 6% enrichment. The objective of the work reported here was to develop a mixed enrichment core design for the NC State University PULSTAR reactor which would: (1) demonstrate that 6% enriched SUNY buffalo fuel could be used in the NC State University PULSTAR Reactor within the existing technical specification safety limits for core physics parameters; (2) show that use of this fuel could permit operating the NC State University PULSTAR Reactor to 2017 with increased utilization; and (3) assure that the decision whether or not to relicense the facility would not be prejudiced by reduced operations due to low excess reactivity.}, number={1997 Dec. 31}, journal={Dept. of Energy NTIS Report #DOE/NE/38004-1(12/97)  Contract #FG05-95NE38004}, author={Mayo, C.W. and Verghese, K. and Huo, Y.G.}, year={1997} }