Development of a Laser Induced Fluorescence Diagnostic System for Hall Thruster Plasmas

Laser Induced Fluorescence (LIF) Diagnostics

LIF System under Preparation

Wonho CHOE1, Holak KIM1, Seunghun LEE1,2, Guentae DOH1, Sung-Young YOON3

1Korea Advanced Institute of Science and Technology (KAIST), Republic of Korea2Korea Institute of Materials Science (KIMS), Republic of Korea3National Fusion Research Institute (NFRI), Republic of Korea

3 Korean LEO Satellites in Orbit

DubaiSat-2 Deimos-2

STSAT-3

z

r

Anode

Inner wall

Outer w

all

Multiply charged ions High energy ions

Plasma instability Plasma wall interaction

Electric Propulsion and KAIST R&DFundamental Physics

Research

𝜆𝜆laser =𝜆𝜆exc

1 − 𝑣𝑣/𝑐𝑐=

834.72331 − 𝑣𝑣/𝑐𝑐

nm

+ 𝑣𝑣 𝜆𝜆laser Tunable Laser

• Plasma characteristics have been investigatedusing various diagnostics (e.g. Faraday, RPA,ExB etc), however, mostly outside the channeldue to high energetic ions.

• LIF is a powerful diagnostics to obtainimportant physics information includingplasma potential and 2-D ion accelerationprofiles, which are related to our recentresearch (wall interaction, high energy ions,multiply charged ions etc).

Xe+

*S. Mazouffre, PSST 22, 013001 (2013)

Ion Velocity Distribution Function Measurement

Window PinholeMount

126.45mm 10.27mm 16.00mm 88.62mm 30.88mm 10.00mm 36.10mm

1st LensMount

2nd LensMount

3rd LensMount

12.70mm

12.70mm

12.70mm

2.0mm

4.0mm

0.04mm 2.5mm

4.0mm

4.0mm

111.16mm

5.79mm

38.10mm

3.96mm

21.0mm 11.7mm

32.60mm

2.5mm

DoubletLens

5.5mm 4.7mm

74.72mm 13.68mm

32.20mm

12.50mm

PMTHouse

18.9mm9.50mm

Optics BoardFront

6.0mm

1.62mm

Distances between Lens(For Zemax)

Distances between Mounts

(For Mounting)

26.89mm

Focus Point

4.51mm

Schematic Diagram

Optical Path of Detector

ESA Electric Propulsion Space Missions

Hayabusa-1 μ-10 thruster

Electric Propulsion Applications

a

b2b1

c d e

Alignment of Detector

The LIF system consists of a tunable diode laser (834.72 nm,Mode hop free tuning: 50 GHz, 90 mW) and a wavemeter(700-1650 nm, accuracy: 1 pm).

Optical path was demonstrated by computer calculation andcomponents were aligned by using a visible laser.

Difficulties:- Large focal length (1 m) to get signals outside vacuum

Not enough fluorescence (541.9 nm) by the laser- Strong fluorescence (541.9 nm) without laser Hard to

distinguish the fluorescence- Using lens with short focal length (< 1 m) and increasing

laser power could be an alternative.