Plasma E- Measurement

Brian DeHerreraJohn PurcellJaber Assiri

OutlineIntroduction

◦Purpose◦Problems

HFSS SimulationCurrent DesignVoltage DividerFuture Work & budgetConclusion

PurposeCreate reliable current and voltage

sensing equipment to work in common plasma ranges◦>500V◦>10MHz

Create more reliable plasma for experiments◦Control line impedance ◦Measure waveform being transmitted to plasma

probe

Plasma System

Signal Generator Amplifier

Z-Scan

Matching Network

Plasma Probe

ProblemsNo commercially available probes

◦Can meet some specifications, but not both frequency and desired voltage

Not trivial to create homebrew probe◦Needs to be high impedance◦Parasitic

HFSS SimulationDraw ModelAssign Boundary ConditionsAssign Excitation Ports (inputs)AnalyzeGenerate Reports

Draw Model

Freq Response

Current Design: CoaxModeled design off of AE’s Z-ScanBenefits:Parasitic are minimizedSensor can be added in-line with plasma

systemConcerns:EMI design: both shielding outside noise and

reducing leakageSemi-complicated design

◦Need to machine parts

Current Design: Coax

Signal Generator Amplifier Z-

Scan

Matching Network

COAX device

Plasma Probe

Current Design: Coax

Voltage Divider Why a V-D?

Voltage DividerConditions:

◦R1+R2>= 2M Ohm & C1+C2<10p F

Signal Generator Amplifier Z-Scan

Matching Network

Plasma Prob

e

Voltage DividerConditions:

◦R1*C1=R2*C2

If (R1*C1)> (R2* C2)

Voltage DividerConditions:

◦R1*C1=R2*C2 If (R1*C1)<(R2* C2)

Voltage DividerConditions:

◦R1*C1=R2*C2

Voltage DividerFrom:

◦R1+R2>= 2M Ohm & C1+C2<10pF

& ◦R1*C1=R2*C2

Therefore:◦R1= 10M ohm, R2= 100k ohm

◦C1= .1pF , C2= 10pF

Future WorkDate What will be done Cost

1/30/2010 Finish the designs we have

$120

2/1/2010 Find more sensitive Current Transformer

& probes

2/10/2010 Getting some readings

2/15/2010 Change the important changes in the

designs

$10-$20

3/1/2010 Getting some results

3/30/2010 Start to do the final designs

$10-$50

ConclusionPurposes & problemsHFSS SimulationCurrent DesignVoltage DividerFuture Work & budget

Thank youQuestions ??