Transcript Slide 1
The Work Being Done at the Ion Beam Laboratory at Texas A&M University Van D. Willey Columbia High School Under the Direction of Lin Shao Assistant Professor Department of Nuclear Engineering Texas A&M University •Containment • Steam Generator •Pressuerizer • Pump •Pressure Vessel Radiation Damage Creation Schematic of a nuclear pressure vessel and a displacement cascade generated by a neutron. Interaction of ion beams with a crystalline solid Ion Beam Deposition (~10 eV) Ion Implantation (~100 keV) Ion Beam Analysis (~1 MeV) Show and Tell Low power Ion beams can be used to deposit one material on the surface of another….gold or aluminum onto silicon. This can be used to make useful things like radiation detectors and solar cells. STAAR/TEKS 2(e), 8(b), 8(d) Use as Radiation Detector • Radiation causes multiple electronhole pairs to be formed • Electron hole pairs are accelerated across the potential barrier Student Activity The student will make a solar car from a selection of K’Nex building pieces, a solar collector and a motor. She will then optimize the positioning of the collector (with respect to the sun) for maximum speed. If the activity is done indoors, hopefully the same effect can be experienced with the overhead lights or maybe a selection of flashlights. STAAR/TEKS 2(e), 8(b), 8(d) Student Activity The student will determine the optimum type of light source to maximize the speed of a commercially available solarpowered toy car. He will use incandescent and LED flashlights held at a specified height over the car to power the car a pre-measured distance. He will then be able to show how the distance from the light to the car affects the speed of the car STAAR/TEKS 2(e), 8(b), 8(d) 200 keV 140 keV 10 keV 1.7 MeV 1 MeV Five Accelerators (ion energy from 10 keV to 1.7 MeV): One of the largest university ion irradiation facilities in US) F/A 18C D Student Activity • Operation of the Ion Accelerator requires precise control, some of which is supplied through the use of a temperature control device called a thermocouple. Student Activity • She will use a multimeter to see the induced voltage across a shop-built thermocouple • She will find the corresponding temperature from an online chart for that type or thermocouple. STAAR/TEKS 2(e), 5(d) Source • Protons are most popular ion for PIXE • Sputter source is used – Metal Hydride • Source is first given a negative charge • Ions are pulled off of the sample by a relatively weak electric field The Accelerator looks more like this Mass purification • Magnet – A large electromagnet is used here to purify the mass • Calculating radius of curvature – Speed and charge of particle are known – Magnet field strength is controlled by supplied current – The radius can be controlled to purify the beam Mass Purification • As charges move perpendicular to a magnetic field a force is applied to them • This charge will accelerate the ions around the curve – F=constant=ma • Too massive not enough acceleration • Too small too much acceleration Student Activity • Simulate the effect of the turning magnet with small bar magnets, a ball bearing and a section of Hot Wheels track • She will then be asked to write a short summary of why she chose the design she used. STAAR/TEKS 2(e), 8(b), 8(d) Ion Beam Analysis RBS - Rutherford Backscattering for depth profiles of complex thin films (up to a few microns thick and down to a few nm depth resolution). EBS - Elastic (i.e. non-Rutherford) backscattering (for better C, N, O analysis). ERD - Elastic Recoil Detection (used for H analysis). PIXE- Particle (usually proton) Induced X-ray Emission NRA - Nuclear Reaction Analysis (isotope specific). IBIC - Ion Beam Induced Charge. STIM - Scanning transmission ion microscopy. NRA STIM Electronics Port 3-D stage view port RBS, PIXE Ion beam EDS Spectrum of human hair 10000 RBS Yield 1000 Hair 100 Be substrate 10 1 0 100 200 300 Channel Number 400 500 10000 C: 80% Experiment Simulation N: 15% O: 4% 1000 RBS Yield P/S: 5% Ca: 5% Contamination from Be substrate 100 10 100 200 300 Channel Number 400 PIXE (Particle Induced X-Ray Emission) Setup X-ray Production • Steps – Charge particle is accelerated – Enters surface of material – Interacts using electromagnetic force with tightly bound electron • Ejection of electron • No ejection if very low energy – Electron leaves inner shell – Electrons drop to fill lower shell • Production of X-ray • Production of auger electrons Thank you! Van Willey Columbia High School [email protected] Lin Shao Department of Nuclear Engineering Texas A&M University [email protected] Lloyd Price Texas A&M University USRG 2011 [email protected]