Nanostructured alumina materials characterization study

Transcription

1 I-3. Development of mini-focus SANS Main collaborator: Abdul Aziz Mohammed Malaysian Nuclear Agency (Nuclear Malaysia) Kompleks PUSPATI, Bangi Kajang Selangor MALAYSIA Tel #: ; Fax #: Other collaborators: Azraf Azman, Mohd Rizal Mamat, nuclearmalaysia.gov.my Megat Harun Al Rashid Megat Ahmad, Rafhayudi Jamro, Anwar Abdul Rahman, I-3.1. Project Summary The current SANS system at Malaysian Nuclear Agency is only capable to measure Q in limited range with a PSD (128x128) fixed at 4m from the sample. The existing reactor hall that incorporate this MYSANS facility has a layout that prohibits the rebuilding of MYSANS where the position between the monochromator (HOPG) and sample, and the position between the sample and the PSD cannot be increased for wider Q range. The flux of the neutron at current sample holder is very low which is around 10 3 n/cm 2 /sec. Thus it is important to rebuild the MYSANS to maximize the utilization of neutron beams. Over the years, the facility has undergone maintenance and some changes have been made. Modification on secondary shutter and control has been carried out to improve the safety level of the instrument. A compact micro-focus SANS method can suit this objective together with an improve cryostat system. Study of focusing issues (divergence/specular tails) and evaluation and design of micro-focus apparatus for MYSANS facility at Nuclear Malaysia which include design and fabrication of focusing reflector (NiTi) and detector system will be beneficial in term of technology enhancement and human capital development. In the last meeting, we reported there are four researchers involved in this project. From Oct 2008 two junior researchers have been assigned into this project. It is therefore six researchers are engaged in this project. The following is a brief background of the new members. Anwar and Rizal are Mechanical Engineers and have been working with the Nuclear Malaysia for 6 years. They are currently undertaking work on Shielding Fabrication for X-ray and Neutron Beam Application. Megat Harun is currently on on-job attachment with Dr Furusaka laboratory at Hokaido University, Japan. His main mission is to design and collecting information on hardware and software for MYSANS micro-focusing technique.scope of Works I Nanostructured alumina materials characterization study The production of alumina materials with controlled porosity is of considerable interest to the international research and development community. This study has identified that alumina 37

2 with controlled porosity was useful in the electronics industry and set about finding the best method of material preparation and the most appropriate methods of materials characterisation. Alumina nanostructured samples preparations have been carried out at Nuclear Malaysia and SANS characterizations have been performed at SANS BATAN, Indonesia. Analyses of SANS data and modelling of the nanostructured samples are mostly carried out by the Nuclear Malaysia s MYSANS group. I Neutron cooling Studying the present cryostat design and its performance has been carried out in re-innovating a cooling system that can be enhanced the cooling efficiency and will increase the production of thermal cooled neutron. The new system will incorporate improved heat transfer rate, therefore will allow the production of more thermal neutrons. Fluid dynamics calculations will be carried out to model the heat transfer mechanism in the system. Some works and components have been done in realising these needs. It can be highlighted as follows: The new liquid nitrogen container is a self-pressurized container. The liquid losses are minimal compared to the current system. The current pumping system used small pump and deliver the liquid through a flexible pipe Vacuum pump-turbo molecular pumping station which can achieved higher vacuum level up to 1e-6 milibar (Leybold). Previously the cryogenic was pumped using only roughing vacuum pump the pumping level is ~ 1e-2 milibar. The cryostat which includes the liquid nitrogen (LN2) tank, Beryllium (Be) filters and Cadmiums. The heat transfer from LN2 tank to the Be and Cd is through the thermal 38

3 lingkage which is attach to the tank. The system only achieve 83K after 2 hours and basically need ~ 50 liters of LN2. The losses may also come from the LN2 delivery from the Dewar tank. The LN2 is transfered using a flexible pipe and not properly insulated along the pipe. The delivery is done using the compressed air method. To reduced the losses, we will use the self pressurized tank to deliver the LN2 efficiently. With the current system, the cryostat is vacuum pump only up to 1e-2 milibar and the tank is not insulated. To improve the cryostat performance, the tank now is insulated using the super insulator aluminized maylar and the system will be vacuum up to 1e-06 milibar. To measure the temperature, the current feedthrough thermocouple adapter is not suitable. A new thermocouple feedthrough with four terminals and thermocouple type T replacing the current feedthrough. The feedthrough and thermocouple has been installed at the cryostat. Thermocouple- 4 terminals The thermocouple system also had improved and installed at the cryostat to measured the Be filters. Super insulator- Alumanized mylar The liquid tank is insulated with multilayer super insulator aluminized mylar and vacuum pump up to 1e-6 milibar to minimized / reduced the thermal radiation heat transfer. I Neutron shielding Computational methods have been carried to simulate radiation shielding surrounding an instrument. The Monte Carlo (MC) method is a computational algorithm that can provide approximate solutions to a variety of nuclear and also other physical problems by the simulation of random quantities. MCNP is well known to provide reasonable agreement on result simulation and real experiment. A Monte Carlo simulation of the Malaysian nuclear reactor has been performed using MCNP Version 5 code. The determination of flux distribution for TRIGA Mark II PUSPATI (RTP) research reactor and SANS beam port in Malaysia was done based on the Monte Carlo method. The modelling work has been performed to calculate the value of flux distribution i.e. neutron and photon in a SANS facility. The beam port and SANS facility was modelled as close as possible to the real geometry to get the reasonable results. The SANS beam port were modelled in 200 cm length and 20 cm in diameters. 39

4 Fig. 1: Radial Model for the RTP configuration in MCNP 5 Figure 2: SANS beam port (cell no. 409) were modeled in MCNP5 computer Code 40

5 Result: Cell no. neutron flux (ncm -2 s -1 ) or Relative errors, R photon flux (pcm -2 s -1 ) 409 thermal: x10 10 fast: x10 10 photon: x I-3.2. Work Plan Year

6 Nanostructured Material Characterisations No Programme / Activities Jan - Apr May Aug Sept - Dec Notes 3. Design of micro-focusing mirror and funding applications 4. Evaluation of parts/hardwares those to be purchased and fabricated 5. Setup, testing and verification of micro-focusing system and shielding performance assistance from Hokaido University Cooling System for Neutron Beam Conditioning No Programme / Activities Jan - Apr May Aug Sept - Dec Notes 4 Initial testing and system verification 5 Performance evaluation at various reactor powers Shielding Calculation Using MCNP No Programme / Activities Jan - Apr May Aug Sept - Dec Notes 3. Simulation and estimation using MCNP for shielding system including collimator system, neutron source and neutron collimator 4. Evaluation of parts, hardware and materials to be purchased and fabricated 5. Setup, testing and verification of shielding performance evaluation 42

7 I Current Achievement and Results MYSANS enhancement in electronic DAQ interfacing method using GPIB-USB protocol, data treatment/analysis and easy movement of the flight installed air lifting footers and collimator tubes. Cryostat simulation results using 2-D & 3-D geometry using FEA. The result with 2D FEA modelling is accurate and mostly in agreement with the result obtained through experimental. MCNP basic simulation on MYSANS shielding setup. Sample prepared and characterise using BATAN, SANS and other related techniques, i.e. TEM, XRD. I-3.3. Work Plan For The Year

8 Nanostructured Material Characterisations No Programme / Activities Jul Dec 2009 Jan Jun 2010 Jul Dec 2010 Notes 1. Sample preparation for measurement at SANS facility in BATAN and data analyses and programming 2. Design of micro-focusing system, shielding components and funding applications assistance from Hokkaido University 3. Procurement preparation for parts/hardware/materials to be purchased and fabricated Cooling System for Neutron Beam Conditioning No Programme / Activities Jul Dec 2009 Jan Jun 2010 Jul Dec 2010 Notes 1. Implementation of heat transfer mathematical models and cryostat redesign parameters 2. Models discrimination and parameters estimation using Computational Fluid Dynamic (CFD) software. (To model with 3D analysis and repeat experimental testing to verify our design and simulation data.) 3. Purchase of hardware and related controlled components for cryostat modification 44

9 Beamline Upgrading No Programme / Activities Jul Dec 2009 Jan Jun 2010 Jul Dec 2010 Notes 1 Flight tube positioning and alignment. 2 Modification of front collimator external shielding. Monte Carlo Simulation: MCNP - Shielding Calculation No Programme / Activities Jul Dec 2009 Jan Jun 2010 Jul Dec 2010 Notes 1. Expansion of the MCNP5 modelling to the whole SANS beam port and SANS facility. 2. Evaluation of computing hardware and software items to be purchased 3. Testing and verification of instrument characteristics and performance Monte Carlo Simulation: McStas Beam Instrument Calculation No Programme / Activities Jul Dec 2009 Jan Jun 2010 Jul Dec 2010 Notes 1. Evaluation of SANS existing set-up and set-up with reflection/focusing mirror 2. Testing and verification of instrument characteristics and performance 45

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