The Work Being Done at the Ion Beam Laboratory at Texas A&M University

Van D. WilleyColumbia High School

Under the Direction ofLin Shao

Assistant ProfessorDepartment of Nuclear Engineering

Texas A&M University

•Pressure Vessel

•Pressuerizer

• Steam Generator

• Pump

•Containment

Radiation Damage Creation

Schematic of a nuclear pressure vessel and a displacement cascade generated by a neutron. 

Ion Beam Deposition (~10 eV)

Ion Implantation (~100 keV)

Ion Beam Analysis (~1 MeV)

Interaction of ion beams with a crystalline solid

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 electron-hole 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 solar-powered 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)

F/A 18CD200 keV 10 keV

1.7 MeV 1 MeV

140 keV

Five Accelerators (ion energy from 10 keV to 1.7 MeV): One of the largest university ion irradiation facilities in US)

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 multi-meter 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)

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.

Ion Beam Analysis

RBS, PIXE

NRASTIM

Ion beam

view port

Electronics Port

3-D stage

EDS Spectrum of human hair

0 100 200 300 400 500

1

10

100

1000

10000

RB

S Y

ield

Channel Number

Be substrate

Hair

100 200 300 40010

100

1000

10000

O: 4%

N: 15%

Experiment Simulation

RB

S Y

ield

Channel Number

C: 80%

P/S: 5%

Ca: 5%

Contaminationfrom Be substrate

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

Van WilleyColumbia High Schoolvan.willey@cbisd.com

Lin ShaoDepartment of Nuclear Engineering

Texas A&M Universitylshao@ne.tamu.edu

Lloyd Price Texas A&M University

USRG 2011lloydmprice@gmail.com

Thank you!