Annexure-i justification of Building funds
Yüklə 0,69 Mb.
|
Laser dyes: We are also interested in some laser dyes of xanthene family and coumarins. Presently, we are studying the salvation dynamics of these dyes with the help of vibrational spectroscopic techniques and density function theory calculations. We are also working on the vibrational dynamics of some potential radio protective antioxidant and radical reactions. Future Plan We plan to start work on surface enhanced Raman spectroscopy of porphyrins and phthalocynaines in near future. It is planned to study the surface enhanced Raman spectra of some porphyrins and phthalocyanines for gaining insight into the different enhancement factors. Molecule-metal (substrate) interaction will also be investigated from the spectral changes in the Raman spectra. The optical absorption spectra, which contain information about the electronic absorption of molecules and plasmons of metals, will also be recorded for further enhancement of Raman signal, by exciting the samples within absorption region. Hence, from the experimental data the pathways and mechanism of enhancement of Raman signal and interaction between metal surfaces and porphyrins/phthalocyanines will be elucidated. Experimental study will further be supplemented by the density function theory calculations. Proposed work may provide better understanding of working of porphyrin and phthalocyanine as chemical sensors on molecular level and development of smart sensors in future. PROPOSAL FOR 12th FIVE YEAR PLAN REGIONAL CENTRE FOR PIXE, PIGE and UPGRADATION OF CYCLOTRON LAB FOR ALPHA BEAM The 27 inch variable energy cyclotron of the department is capable of producing proton beam of 1.7 MeV to 8.0 MeV and alpha beam of 6.6 to 8.0 MeV. It is also possible to operate the machine in the third harmonic of the oscillator frequency and it can give proton beam of 0.7 to 3.5 MeV and alpha beam of 0.5 to 2.6 MeV. For the last several years the cyclotron was mainly used for accelerating proton beam in the energy range of 2 MeV to 3MeV. Recently few old power supplies of the cyclotron magnet systems was replaced by solid state power supply, by the generous funding from the departmental CAS programme and a DST project for the regional PIXE programme. At present this is the only accelerator in the country available for low energy proton and alpha beam in the above energy range. This particular machine being the oldest running accelerator in the world, it requires continuous maintenance and up-gradation. We propose to upgrade the existing experimental set up and continue the programme for PIXE and PIGE as analytical techniques and also for measuring (p,γ) and (α,γ) reaction cross sections which has a direct relevance for nuclear astrophysics and nuclear data. This programme will be use full as a training ground for students of M.Sc., Ph.D. and post-M.Sc. course in accelerator physics of the department, besides its nuclear physics importance. This group efforts for next five years will also be use full for the proposed 5MV accelerator of the Panjab University.
Reaction rates are central in the modeling of the nucleo-synthesis and energy generation[5]. The rates are computed by integration of the reaction cross sections across an energy range defined by the plasma temperature. Normally reactions of astrophysical importance occurs at low energy (E< 10 MeV for charged projectiles and E< 1MeV for neutrons). Three reaction mechanisms contribute the reaction cross section: compound, resonant and direct reaction[5]. There are 32 stable isotopes on the proton-rich side of the chart (Nuclide between 74Se and 196Hg). The natural isotopic abundance of these nuclei is 10-100 times less than the more neutron-rich isotope. Modeling the synthesis of the p- nuclei and calculating their abundances require an extended reaction network calculation involving more than 105 reactions of 2000 stable and unstable nuclei. The Hauser-Feshback(HF) theory is used in the calculation reaction cross sections relevant to the p-process nucleosynthesis, since the vast majority of the over 20000 cross sections involved cannot be determined experimentally. The p process involves radiative neutron capture and the inverse photodisintegration process, as well as proton and alpha-capture and their inverse reactions. It is therefore a key importance to measure such reaction cross sections for the reaction network model improvement, to investigate the uncertainties in the nuclear data, and in particular, in the nuclear level densities, optical model potential and gamma-ray strength functions entering the HF calculations. In order to better constrain proton and alpha-nucleus potential as well as NLD model we propose to start this research programme for nuclei A>90 ( as the data in this region is less. (b)National and International Staus: Untill 1980 (p,γ) reactions were studied using the BARC Vandegraff accelerator facility [3]. After wards till date there is no such programme in this direction was persued. Recently due to large discrepancy in optical potential in reaction network calculation has motivated people to measure (p,γ) and (α,γ) cross section at sub-coulomb energy and to analyze with the latest knowledge of optical potential[5]. The microscopic optical potential (JLM) with low energy modifications is widely used for neutrons and protons. This JLM potential is somewhat not successful in explaining the available data. However, it has been argued that the iso-vector components of the JLM potential may be too weak. Indeed, in a comparision to the recent 70Ge(p,γ) and 76Ge(p,n) data[4] it was found that the energy-dependence of the S-factors of this reaction and the old measurement of (p,γ) and (p,n) reactions on Se and Sr isotopes can be better reproduced when increasing the JLM imaginary depth by 70%. For the alpha optical potential there are no such microscopic potentials available and attempts to derive a global potential are restricted to fits of Wood-Saxon shapes. This further warrants more (α,γ) measurements for better under standing the optical potential. There are two recent examples of (α,γ) reactions to measure for alpha-capture on 112Sn and 106Cd relevant for p-process energy range[1-2]. (c )Method of activation technique: Activation method is a very common technique in applied physics. This technique has recently been used in the low energy nuclear physics for the (n,γ) work in the context of s-process studies. In a high resolution charged particle capture reaction, the direct observation of the prompt capture gamma rays is a standard method (due to the excellent energy resolution of the Ge detectors). This advantage is no longer use full for A>60 nuclei due to the increasing complexity of the capture gamma ray spectra. In the above scenario activation technique is more use full. In the activation technique target of proper thickness is irradiated by stable proton and alpha beam and the induced activities were counted offline with a High resolution HPGe detector. It is a fairly simple technique and exhibits good sensitivity, and it is selective for specific reactions via the decay of the product nuclei. This aspects also allows one not only to use samples of natural composition, but offers the possibility to determine several cross sections in a single measurement. (d)Experimental Plan: The cyclotron laboratory already has a chamber routinely used for PIXE measurement. The Chamber has provision to put target and various kind of detectors and also it has slot for mouning X-Ray and HpGe detector. A HpGe detector of 40 to 50% relative efficiency is required to carry out the above studies. Targets will be mounted in the PIXE chamber for irradiation. A surface barrier detector will be kept around 150 degree for acquiring the RBS specta (Which will help both in beam normalization and checking the quality of the target during beam normalization). After suitable irradiation induced activities will be counted offline. Thick lead shield will be used to reduce the back ground. The counting will be done out side the chamber to make arrangement for the reduction of the background. The laboratory has one very old HPGe detector at present it is not working. We will need a new HpGe detector and we will also explore to repair the old HpGe detector for measuring life time of the nuclei produced by the above reactions. Budget: (e) Instruments (Estimated Cost): Name Approximate price in Rupees (i) Multi parameter data acquisition system with a ADC 08 Lakh (ii) HPGe Detector with anti-Compton shield 20 Lakh (iii) Power Supply 04 Lakh (iv)Surface barrier detector-03 Number 02 Lakh (v) Pre-amplifier 3 Lakh (vi)Amplifier 4 Lakh (vii) Enriched Target Material, Alpha Source 7 Lakh Standard samples for calibrarion of PIXE and PIGE (viii) He-gas with Cylinder 03 lakh (ix) Repair of old He-Leak detector 02 Lakh (x) Repair of old HpGe Detector 05 Lakh (xi) Maintenance of Cyclotron (Five year period) 42 lakh ( It includes change of power supply) Total 1 Crore
Yüklə 0,69 Mb. Dostları ilə paylaş:
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||