Training

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Modelling plasmas for light generation - Some
thoughts on the needs of the lighting industry
COST Model Inventory Workshop 12 to 15 April
2005 University of Madeira, Funchal Stuart
Mucklejohn UK National Representative to
COST529 GE Consumer Industrial- Lighting,
Melton Road, Leicester LE4 7PD, UK
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What are models used for ?
New product development Product
improvement Fault finding Production
processes Education Training
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What is a lamp ?
Light generating component of a system used to
illuminate things Within the European
Union An energy using product (EUP) A
product subject to the WEEE directive A product
subject to the RoHS regulations
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What is a high intensity discharge (HID) lamp ?
A light emitting high temperature chemical
reactor Characteristics Plasma has electron
temperature gas temperature Operating pressure
1 to 50 atm, up to 200 atm for UHP Local
thermodynamic equilibrium is a reasonable
assumption
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Uses of HID lamps
Road lighting Car headlamps Stage/studio
lighting Horticulture greenhouse
lighting Interior lighting warehouses
shopping malls Floodlighting sports
architectural Projection systems
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Types of HID lamps
Description Typical application Low-pressure
sodium road lighting High-pressure
sodium road lighting High-pressure
mercury road lighting Metal halide with silica
arctube interior, sports, malls Metal halide
with ceramic arctube interior, malls,
streets Ultra high pressure projection systems
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Some characteristics of HID lamps
Power range 20 to 20 kW Output 1600 to
2000000 lumens Life 500 to 28000
h Size 50 to 500 mm Global market gt500x106
per annum
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The system includes light source the receptor
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Components of HID lamps
Outer enclosure - glass outer jacket metal
connectors Arctube - silica or
ceramic Electrodes - tungsten Leadwires
molybdenum, niobium Chemical additives -
mercury, sodium, metal halides Gas fill - argon,
krypton85 Joins Seals
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A metal halide lamp with ceramic arctube
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Interactions within HID arctubes
Gas phase 1000 to 6000 K light
generation Liquid Gas 700 to 1300 K dose
evaporation Solid Gas 700 to 1500 K
corrosion Liquid Solid 700 to 1300
K corrosion Solid Solid 700 to 1500 K corrosion
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Temporal phenomena
Steady state Transient Non-LTE Reactio
n kinetics
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Energy balance for a metal halide lamp
From Philips Lighting the ALITE program
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Life cycle of HID lamps
Assumes life of 10000 h Production Raw
materials, processes, testing 0 to 100
h Rapidly changing properties to 100 h 100 to
1000 h Significant changes in output 1000 to
10000 h Slowly changing output, failures End of
life Disposal Recycling Environmental
impact
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Fundamental data

• Radiation properties of optically thick
  radiators (line broadening, transitions
  probabilities)
• Radiation properties of optically thin radiators
  (reduced emission coefficients)
• Diffusion coefficients mobilities of plasma
  species
• Viscosities of buffer gases
• Thermochemical parameters for plasma species
  (discharge properties)
• liquid - gas reactions (dose chemistry)
• solid - gas reactions (corrosion)
• solid - liquid reactions (corrosion)
• Kinetic parameters for material transport
  mechanisms

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Examples of predictive models needed
Lamp voltage rise through life Lamp voltage
colour changes for vertical horizontal
operation Luminous efficacy through life Output
from 200 to 3000 nm Lamp life
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History
Many descriptions of models at
conferences Large number of scientific
publications Valuable resource for the lighting
industry But .. Some reports/papers very
difficult to find Software no longer available
not designed for operation by third parties
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Acknowledgements

• Many thanks to
• Barry Preston (GE Lighting)
• Raghu Ramaiah (GE Lighting)