1

Experimental Determination of the Stable Boundary for a Cylindrical Ion Trap

Andrew Alexander, Dr. Victor Kwong*, Brad Clarke, James BeneventeUNLV Summer REU Program,

Las Vegas, Nevada

August 9, 2010

2

Introduction

Ion Traps: first designed with hyperbolic electrodesEquations of motion – exact analytic

solutionDifficult fabrication process

Cylindrical ion trapEasily constructed and functional

alternativeTheoretical model remains elusive.

3

Objective

Ions near center of trap “see” approx. hyperbolic potentialsGood starting pointExact trapping parameters must be

determined experimentally Goals:

Determine stable boundary for cylindrical design

Compare findings: simulated results & hyperbolic electrode theory

4

System Components

5

.

System Components

6

System Components

7

System Components

8

System Components

9

System Components

10

Trap Design Basics

Ring electrode:AC potential (V0) & DC potential offset (U0)

end capelectrodes

ringelectrodes

11

Theory – Hyperbolic

Ion equation of motionForm of Mathieu differential equation:

& – linearly related - V0 and U0

12

Simulation - Cylindrical

Ion equation of motionNo simple solution

Turn to simulation program: SimIonNumerically determine ion trajectory

& defined the same – comparison

Methods

Experiment 1 Experiment 2 (Delta U0)

Ions created and stored with au near boundary

Ions storage times: 345 & 690 ms

Ions created and cooled – 700 ms

Ideal trapping parameters

U0 brought near boundary

2 ms storage time near boundary

Basic Process Ion signal scanned as a function of Uo Boundary approx. where signal is lost

14

Global Comparison of Results

15

Conclusion

Creation of ions near the boundary adversely affects ion population

Trap design appear to “leak” ions over time

Delta U0 approach minimizes these complications

16

Acknowledgments

Dr. Victor Kwong Brad Clarke James Benevente Financial support from NSF REU

program DMR-1005247 is gratefully acknowledged.

16