Mini, micro, and high-efficiency torches for the ICP - toys or tools?

Specmc/umm Acts?, VoL 388. No. 11/12. pp. 1465~1481,1983. Primed in Great lkitain.

MINI, MICRO, AND HIGH-EFFICIENCY TORCHES FOR THE ICP

-

TOYS OR TOOLS?

Gary M,Hieftje* Department of Chemistry, Indiana University, Bloomington, Indiana 47405, U.S.A.

ABSTRACT

Because the inductively-coupled plasma (ICP) is expensive both to purchase and to continue in operation, sought to reduce both the radiofrequency ordinarily

required

to sustain

it

could

reduced.

for

approach utilises

example,

paper, assessed

capability. low-power

*

On leave, Analytical institute

in terms of their Prospects

extensively.

for

torch

flows

approaches

ICP instrumentation

will

Department of Instrumentation and Science, University of Manchester of Science and Technology, Manchester,

The final cooling

will

In this

be reviewed and and analytical

torch modification be considered

U.K.

and mast

schemes using,

as a coolant,

practicability future

for

the torch used to support

alternative

water or high air

these alternative

analytical

but the power and argon required

has been modified

argon

In one approach,

in the hope that its

In the second approach,

the discharge recent

be retained

power and coolant

the discharge.

the XCP has been reduced in size, strengths

many workers have

and low-flow,

and discussed.

G. M. HIEFTJE

INTRODUCTION Despite

its

obvious

inductively

coupled

successful

operation

input

bulky,

argon

Similarly,

are

not

gas

cylinders

only

or

the

inexpensive, L/min

will

ICP.

to

the

past

reduce

use

of

the

for

consumes

year

only

urgency

changes

argon

cost

will

gases

of

each

That

is,

a

lSL/min By contrast,

operation.

the

and has

relatively

operation

5L/min

drives

is

$1000.

for

of

dewar.

annual

its

L/min)

alternative

approximately

requires

(>15

troublesome

where

that

is

modification modifications

torch

geometries using, paper,

high-efficiency future

comprehensive,

several

the

These

cooling

America,

$18OOC per

economic

frequent

particularly

can be

rates

a liquid-argon

the

substantial

require

development

only of

$5000.

high-

ICP systems. Over

through

which

generate

plasmas

incorrectly,

either

consider

flow

power

(>1.5kW)

can

the

for

radiofrcquency

consumption

of

In North

in argon

strong

efficiency

sought

to

that

requires

operated

necessitate

can be calculated

plasma

Clearly,

if

is

application,

high-power

argon

argon

approximately

a low-flow

the

of

plasma

cost

Such

availability

cost

increment

conventional

high

and,

but

the

it

ordinarily

instrumentation,

many investigators

support

this

flows.

elevated

costly,

The high urged

(ICP)

interference

hazardous.

and widespread

unfortunately

expensive

radiofrequency

to

plasma

and coolant

require

appeal

gas of

flow the

include

and power torch

these

example, alternative

ICP will offered. but

or

include

will

investigators of

sustain

torch’s

and employin

to

jets

the

a sampling

ICP

discharge.

optimising alternative air.

development

of

attempt of

the

of

and assessed not

have

the

size,

high-velocity

approaches

be reviewed

The review will

the

to

conditions, water

of

requirements

required

shrinking

and operating for

a number

years,

the

and a view to

be

alternative

In a

toward

1467

Mini, micro, and~~h~f~~iencytorches

approaches

and a discussion

of the studies

are particularly

significant.

chronologically,

but will

alternative

approaches

which the author

The discussion instead

will

individually.

approach

flow and power in an ICP is simply to reduce it can be assumed that ICP performance

density

in the discharge,

a satisfactory

low-power operation

just

torch,

necessary

Presumably,

in less

gas flows

and simplify The first (1) size

involved

which could

requirements

approximately

the original

power to pravide study

(1) and later

the same detection

limits

conventional-sized

ICP,

shown thatvaporization

as structured

similar

source.

In short,

the mini-I@

as would the conventional

source,

miniaturised

torch

dimensions;

its

The miniaturised

approximately

analytical

reports

2/3rd

performance.

(2), the “mini-XCP”

studies

and troublesome

systems.

213rds that of the conventional

linearity

the

Prom

exhibited

expected

on the same system,

interferences

minimal and that the background emission was just

enhance sensitivity

narrative.

required

and ionization

result

in Table 1 along with those

and working-curve In later

Such

but might also

in the torch’s

in this

torch and, interestingly,

radiofrequency

be reduced.

ICP in terms of

effective

are listed

for

smaller

of the plasma to ion-detection

systems to be discussed

(lgmm i.d.)

powers,

modest reduction

torch had a diameter

ha designed

a proportionally

of an analytically

a rather

and operating

of other

a factor

the interfacing

description

could

not only a more efficient

atomic dilution,

gas

is dependent an power

gas flow would also

and radiofrequency

to reducing

the plasma’s dimensions.

unit

by configuring

an approach would yield required

not proceed

examine the above-mentioned

Perhaps the most straightforward

If

feels

from a it was

(3) were also

spectrum from theminilCP

(4)

as that from the conventional

can be viewed and utilised but can be operated

exactly

at 213rds of the

G. M. HIEFTJE

1468

radiofrequency Detection

limits,

mini-ICP those

power

are

in

obtained

from

other

In tile

course

of

Sexton,

and useful et

directed

al.

torch;

from

the

of

of

the

top

swirl

velocity

revealed

tube

in

al.

step

g-ram device. flared gas

intermediate

enabling

it

Reported

detection

even the

to

better

interference

worse

than

Table

1,

was the

exhibited

the

system

are

the

compared

with

reduced-size

was described

flowing

in

the

water

the

could

(outer) “fan”

of

the

the

was ICP

the uniformity

torch

flat

an by

constructed

flow,

“coolant” a

torches,

argon

of

inlet

water

“fan”

symmetry

be evaluated.

issuing

indicated of

the

the

“fan”

ICP size

was described

utilised

and sharp

a smooth

torch

edges

was constructed

the

reported easily

ionized

the

by a conventional-sized was operated

on slightly

of

but

the

uninterrupted

boron

nitride,

glass-blown.

were,

“mini-1CP”

elements

“mini-ICP”,

contour

than

13-mm torch

in

the

for

of

rather

machined for

like

by Allemand

on the study

(EIE)

average, However,

(1).

was slightly

unit.

As shown

higher

argon

in

flows

than

“mini-1CP”. Allemand,

(i.d.)

limits

from

they

a 13-mm torch

torches

torch

those

the

of

whereas

only

be precisely

than

of

water

tubes

reducing

tube

The entire

flow.

figures-of-merit

and uniformity.

not

Both

exiting

torch,

in

who tested

(6),

of

The flatness

concentricity

A further et

the

(2).

ICP systems.

ports

torch

torch.

dL/min

where

less

development

inlet

into

from

than

described,

the

directed

the

test

quartz

in a well-constructed of

torch

gas

produced the

2-3,

development to

the

of

water

example,

the

pattern

and concentricity

of

high-efficiency

In the

each

flow

and other

Tables

aid

(5).

into

a coolant

interfcrcncas,

collrcted

interesting

For

and at

torch

In contrast,

et

al.

(6)

indicated

and found

that

the

by Weiss,

study

it

stability

required et

al.

at (7)

problems

least used

700W for the

with

a g-mm

operation.

water-flow

also

a

1469

Mini, micro, and high-efficiency torches

testing of

approach

9mm in

BF power “mini”

(5)

inner

to

develop

diameter

which

and 7L/min

ICP , the

curves,

and most the

lower

(40OOK)

than for

m iniaturised

of

analysis

both

either

the

interaction

coupling

discharges,

boundary.

has

fallen

the

the

skin

Because

In contrast, be greatly were

of

the

the

unit

was 2-3

various

is

lies

coupling

can be directed process.

composition extremely upset

centre,

the

small

by aerosol were

For

in

the

centre

it

minimal

effect

like

to

the plasma’s

the

like

and 31mn (8). of

a large

on the flow

or

interferences.

the

a l-mm channel energy

energy

plasmas

“micro-1CP”

Even if

discharge

“skin

where

in aerosol

matrix

few

introduction.

some 13% of

boundary

changes

the

by the

minimal

discharges

restricted

from

2mm (7)

produce

necessary

discharge,

between

Consequently, should

the

maximum value.

with

for

radiofrequency

distance

plasma

reportedly

into

the

in

and radiofrequency

of

with

the

its

is

in

In all

“skin”

than

The reason

characterised

from of

9-mm plasma

aerosol

plasma.

ordinarily

0.37

depth

the

and those

presumably

exponentially

to

2mm and aerosol

discharge

the

to Tables

unit.

sample

into

distance

energy

energy-coupling sample

the

in

lies

a small

coupled

feature

coupling

aerosol

such

is

is

in

of

was somewhat

interferences

greater

between

decreasing

This

vaporization

performance

into

which

ICP,

expected

samples;refer

in a conventional

occurs

power

coupling

or

reduced

which

ICP,

and

working

ICP discharges,

real

SOOW of

conventional

limits,

characteristics

somewhat

“mini-1CP”

somewhat

depth”,

than

plasmas.

by an EIE are

with

the

micro-plasma

other

of

Like

detection

the

“micro-1CP”

on less

characteristics

of

analytical

caused

energy

flow.

yielded

for

useful

operate

analytical

reported

Unfortunately,

this

argon

temperature

the

a comparison

could

torch

other

Although

shown useful

total

“micro”

ICP.

for

of

an analyticaily

could

skin in

coupling

depth

the would

1.0

0.36

Sampleuptake (aLL/min)

1

0.76

1.2

0.75

I

uaiymn

20

18

18

lOUS)

1.0

(11)

(12)

7000(24)

700

4

I

I

1

5500

lloo

12

1.5

0.8

4

0.8

0.1

2.5'

1.5

17

(23)

0.9

0.5

18

(21)

I

I ) 10

1.5

0.15

0.75

5ob

1.5

13.5

(25)

I

I 1 500=

11

2

0.12

0.8

6Zb

0.48

16

(28)

I

1

I

450=

12

2

0.15

0.5

6Zb

0.48

13.5

(28)

Ripsoa13.5-m air-cooled

ICP TOOBCNES

yOmk.lum Kawaguchi ilipwn Ripson16-m air-coolad

=b

WON

DIMENSIONS. OPXUTINC CONiITIONS AND CURACIZRISTICSOF SEVEUALNICN-EFFICIENCY

Nabulicar8s~ flow (L/saw

TA8L.E 1

I

1100

I 1 10

2

0.17

1.0

1.3.

0.57

13.5

(28)

I

1

Ripson li2O-cc.oled

1471

Mini, micro, and high-efficiency torches

still

be affected. Clearly,

there

is

little

plasmaL

the

prospect

dimensions.

altering

the

the

operating

been

shown

and with one

unless

of

systems

of

the

successfully skin

of

depth

can

ICP.

matrix

further

be

an unlikely

the

ICP can be altered,

reducing

it

has

this

which

by

recently

1OOMRz successfully

interference$9).Clearly,

new directions

only

or by raising

Importantly, at

the

reduced

event,

a 9rmn ICP can be operated

important

might

depth

impedance,

frequency

minimal the

of

In turn,

plasmas

that

skin

study

high-efficiency

heralds ICP

take.

HIGH-EFFICIENCY ICP TORCHES Historically, power

and argon

modifying

the

by Allemand the

most

study,

some of flow

required

torch

used

and Barnes

recent

of

ratio

diameters

plasma large

torch

torch.

It

demonstrated

the

gas

inlet

tube

the

swirl

velocity

promotes

support

in

the

flows.

described

of

-

efficiency

then

Later, of

in

the

torch

into previous for

for

even

design.

In

ratio”

a plasma

tubes

port

in

stabilises

design

features

a number section use

with

of

the

the that

on (12)

the

Such a constriction

simply

in

(6,ll)

group

as

is

supported

same research

argon,

that

ratio

studies

to be

some of

was defined

and outer later

the work

In fact,

basis

a constricted

These

torches

and in

in RF

made by

The configuration

the

coolant

incorporated

the

intermediate

an ICP torch. of

ICP were

plasma.

low-flow

enabled

ignition.

systems

the

reductions

the

“configuration

the

importance

of

easier

surprisingly,

high

ratio

low gas

sustain

performance. of

dramatic

established

was shown

configuration

unusually

(10)

termed

an indicator the

to

to

improvements

a parameter

of

the most

coolant-

increases the were,

plasma, not

miniatudsed

and also molecular

in

and

the

gases

ICP design (13).

a

the

G. M. HlEFl-JE

1472

Other for

investigators

low-power

who have

or

low-flow

Demers and hllcmand at

a rather

that

required

Allemand

(1.5)

RF powers

excite

atoms,

Perhaps

the

torch

design

“plasma

and gas

stability”

flow.

ignited,

stable

ICP.

obtained

is

“plasma axes

and

flow

torch

outlined

surmaarised

of

results

also

occurs

at

Under

these

required

and applied fluorescence to

ionise

operating

or

conditions

RF power

axis

in

Importantly,

the

analysis

same laboratory

an applied conditions,

RF power matrix

solution

(16) of

of reveal

in an

extinguishes

points

stable sustain

500W.

so

both

plasma a stable of

plasma

125W or

Features

of

the

characteristics

optimized

torch

exhibited

was introduced

into

real

Recent

samples.

that

optimal

350W and a coolant

interferences

by

flow

plasmabllows

of

2-3.

the

gas

and an RF power

analytical

for

generated

plasma

of

1 and its

low

The resulting

could

and an RF power

when a 17. NaCl

are

system.

5Llmin

dimensions

at unusually

the

boundaries

of

Using

physical

flow/power

(11)

(11).

coolant

an optimized

torch

flow

or

where

minimal

al.

of

curves

of

optimized

et

stability

in Table

be employed the

not

operation

delineates

3.5L/min

in Tables

from

is

or power

which

a coolant

same stability

could

an atomic

enable

applied

group

closely,

a coolant are

the

curve,

at

to

on a power/flow

The final

alternatively

the

the

stability”

operation.

in

a number

curves,

The flow

plotted

remarkably

use

in

an ICP

by Demers and

flows

by Rezaaiyaan

Such plasma

either

noted

The system

improvement

optimized

slowly

then

dramatic

was reported

reducing

is

plasma

in

tube

+

an 181nm ICP were

power

for

outer

tube

low argon

torches

and

a thick

intermediate

unusually

the

ost

employed

the

was designed

modified

Lowe (14)

operation.

at

Consequently,

as a guide of

it

sample

through

for

operate

because

instrument.

from

5Llmin

can

include

Lowe (14)

distance

only

described

operation

(15).

large

recently

are

flow

minimal

it

and

operation of

5L/min.

and detection

limits

1473

micro, andhighsfficiencytorches

Mini,

are comparable

to those reported

in other

JCP

investigations. The “optimized” of outside

investigators

be used for real convenient

(17-19)

who report

solvents

by the optimized

samples requires

torch

is extremely

to be operated

Prom

the plasma

at somewhat higher

700 to 1OOOW. Under these conditions,

- approximately

carbon deposition

that it can indeed

must be employed (18,19).

the use of organic

RI? power levels

been used by a number

samples and, even more importantly,

when organic

these reports, supported

torch has since

is reportedly

minimal and plasma stability

is

excellent. It is appropriate and optimization studies

whether torch miniaturisation

might not profitably

(16))optimized

than their

to question

larger

torches

of reduced size

counterparts,

at least

frequencies

in the 27-4OMtlz range,

frequencies

(9) will

alter

go hand in hand.

this

Prom recent

perform no better

when sustained

Perhaps operation

at radioat higher

situation.

EXTERNALLY COOLEDTORCHES A clear of externally be cooled (e.g. total

alternative cooled

internally

air)

to the foregoing

ICP torches.

Presumably,

or externally

by a relatively

or by a more effective

cooling

argon flow to the plasma could

approach has been explored

the torch

could

inexpensive water)

reduced.

by a number of researchers developments

gas the

This and points in high-

Torches

The first

ltfmin

is the use

ICP torch design.

Water-Cooled

et al.

if

medium (e.g.

be vastly

the way toward some of the most promising efficiency

approaches

example of a water-cooled

(20) who supported of argon.

torch was reported

a 40 HHz, 4kW plasma on as little

The torch was unusually

large

(4~

i.d.)

by Britske

as and was

TAFiL? 2

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147s

Mini, micro, andhigh-efficiency torche,

found to be effective

for

rare-earth

determination.

However, end-on

viewing was required. The water-cooled

torch of Komblum,

et al.

argon flow of approximately power of only 7OOW(cf.

generator

(21)

lL/min and an W

Table 1).

However, interferences

from Al, Na and phosphate were noted and detection disappointing detection

(cf.

limits

Table 2).

The authors

to the inability

more than O.lL/min

of aerosol

little

However, a later

gas flow.

were reduced

design. (cf.

2).

the original

was surrounded by a silica found to be stable

Under these conditions,

three-tube cooling

a distinct emission

advantage

to pass through the torch Air-Cooled

torch

water

Obviously,

gas but required

an KF power

is unusually low.

water-cooled fashion

The design

systems

without

high has

in that

requiring

light

Torches

water-cooled

interrupted,

plasma was

itself.

One of the major difficulties

cooling

design which

The resulting

are reportedly

over alternative

system but

torch a 2-tube

temperature

can be viewed in a side-on

limits

water-cooling

jacket.

at 4L/min of coolant

interferences

matrix

Later work by the sama authors

of more than 11OOW. The excitation (7OOOK) and matrix

(23)

power (lOOO-18OOW)

Table 3) and detection

improved (cf.Table

for

(22)

nebuliser

torch of Kawaguchi et al.

(24) employed the same kind of top-inlet substituted

study

Babington-style

high radiofrequency

and with a somewhat modified

dramatically

the poor

of the low-power plasma to accommodate

the water-cooled

at relatively

interferences

were

improvement in sensitivity,

In contrast, was operated

limits

attributed

employed the same plasma with an efficient and yielded

dramatically

is the incidence

(22). resulting

with the design of gas bubbles

When such bubbles in torch

no such problem arises

and use of a

forming

in the

form, water flow can be

devitrification when the torch

or melting, is air-cooled.

To

OK

-

N.Cl(>l%)

Ot;ldC blv8nm

TANS

3

BICB-S&T

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OK

.

SOLOTIOBS. AND OWABIC

SSVKu1,XLQI-KlVIC1SW.X ICP DISCKAXGZS~

NYYXCT OF RYINWXSBTS,

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NO=

OK

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OK

1477

Mini, micro, and high-efficiencyjorches

promote

cffertive

air

unusual

load

constructed

of

two plates

inlet

in

this

Five

coil

spaced

a high-velocity

(lL/min),

extended

outer

viewed

through

detection

limits

Table

that

3)

et

amount

quartz

tube

cooled

and water-cooled

conduction by the

through cooling

more power

mentioned

balance in

review,

predict

that

an “optimized”

should

require

25015 just

In contrast,

125W was sufficient fraction the

of

plasma

efficiently

the

to argon

boundary, cool

it

the

heat

is

the not

torch

the

heated walls.

is

greatly,

airby

loses

on studies calculations SLImin

plasma

study

passes

and serves

of

argon

temperature

Presumably,

torch

carried

device

at

earlier

discharge.

the

power-efficient.

operating

the

except

subsequently

the

the

the

against

water-cooled less

of

argon,

heat

example,

“optimized”

and

lies

strongly

to

to

most

the

bear

gas

was shown in

sustain in

the

similar

empirical/theoretical

their

therefore

For

same authors

In contrast,

of

the

plasma to

the

which

which

calculations

this

Nonetheless

unit

heating

heat

and is

an had to be

calculations,

most

two,

flows

conventional

torch

walls;

wall

both

into

lose

an

unless

(26-28)

boundary.

Of these

the

power

plasma

of

emission

a combined

for

goes

directed

and interferences

From these

torch

medium.

earlier

(350010.

balances

plasmas

the

through

These

Using

the

outside

a water-cooled

a conventional

and outside

then

disadvantage.

studies

(24).

copper.

low argon

respectable

plasma in

coil

the

an obvious

ICP torches.

a conventional

at

an

water-cooled

As a result,

to

power

of

designed

was unstable

plasma al.

(25)

relatively

In later

minor.

al.

modified

tailflame

2) were

air-cooled

small

the

tube,

;cf.Table

cooled

the

at

quartz

et

(SOL/min)

plasma

derived

externally

for

the

Kawaguchi,

in

air

was employed.

were

approach,they

energy

the

tube

their

of

of

Unfortunately,

required

compared

Ripson

ports

stream

18-mm torch.

(cf.

cooling,

Cl)

that

a large

outside merely

to

away

G. M. HJEPI-JE

147&i

The authors

also

ICP beyond

that

measure

increase

to

hypothesis

than

those

of

levels.

Using

these

same authors

using

air-cooled

Although

the

water-cooled

better

detection

detection

wall,

instability

suffer

still

matrix

a factor

which

in working

curves.

could

to be

vell

in

is

input

somewhat

continuously, and yielded Unfortunately,

a conventional

when fed

plasma

an organic-

torches

required

lead

long-term

drift

and

torch

types

which

to

analytical

superior.

changes

build-up

of

and

subsequent

torch

those

(28).

criterion,

interferences.

to

both

manner,

immune to

particularly

Moreover,

study

a number of

salt

at

and water-cooled

air-cooled

from

(21)

torch

analytical

to be aspirated

inferior

functioned

aerosol.

tube

not

Kornblum

water-cooled

generally

more

solvent

of

optimization in

This

temperature

a univariate

the

the

and lower

were

torch

containing

did

limits

limits

and neither

the

requiring

torch

in

is

the plasma.

air-cooled

was found

device

large

limits

his

1);

and although

temperamental, air-cooled

Table

torch

power

the

dimensions

(cf.

in an

low excitation detection

as

in

in

who operated

ratio

the

serves

ionization

directly

torch

studies,

more

of

argon

power

in a more directly

compared

was modified

radiofrequency

the

relatively

(23)

findings

Optimizing

torch

additional

and the poorer

signal-to-background

each

the

the

Kawaguchi

power

torches.

degree

explain (7)

that

to heat

the

by Weiss

higher

the

required

might

reported

suggest

viewing

through

CONCLUSIONS Tables have

been

1-3

reported

characteristics

offer

the

torch

is

for

best

coolant-gas

for that

First,

arise.

more

different

high-efficiency they

the

solution

flow. the

documentandcompare

yield,

near for

Of these proven

term,

ICP use From these the

data,

“optimized”

ICP operation two alternatives,

and can

and the

therefore

at

analytical

several

conclusions

or miniaturized

reduced the

be used

RF power

torches and

13-mm reduced-size with

greatest

1479

Mini, micro, and high-efficiency torches

confidence. load

coil

change

supplied

is

the

directly

reported

in

in

employed

where

low-flow

interfacing For argon

to

one might

to

conductivity.

laser

tubes

electrical

of

cooling

ultra-low

flow that

future

a quartz

must

confirmed

ICP.

carry by

the

outer Be0 is

its

thermal

externally

cooled

might

In

the

water

away between of

would

more tubes

et

of

2.5L/min

is

the water

long

future al.

be

in

ideal

is

for

(23),

necessary

These

and de Galan

used

and low for

an it

to

increased

can be calculated

350 and 85OW.

higher

Alternatively,

the

flow

seems

efficient,

of

seem to

in

Kawaguchi,

Ripson

two

conductivity

of

or

water-cooling

a material

work

it

power

Of the

torch

employed

data,

Obviously,

requirements.

ICP torches.

as a result,

From these

findings

be

would

chromatography,

air-cooling

example, high

similar

Future

radiofrequency

Such a material

ICP torch; 2-SC.

the

of

itself

a coolant

temperature water

in

conductivity.

radiative

cool

To render

can be

available

required.

literature,

(28).

For

because

construction

stated

see

are

but

frequencies

liquid

a necessity. the

torch

Such systems

for

applied

in

as widely,

higher

has similar

seems

described

air-cooling

expect

in

In

forthcoming.

(9).

dilution

spectrometer

used

see

systems

atomic

cooling

already

no doubt

detection

this

now commcrically

be

torches

reductions

external

alternatives

thermal

a mass

dramatic

flow,

inferior

in

been

is

the

although

An optimized

should

will

miniaturised

and minimal

with

use

design

not

(11)

in

by many users.

unit.

literature on its

useful

generators;

have

a commercial

torch

a modification

bc undertaken

torches

the

with

be especially

the

in

requires

ICP power

not

“optimized”

developments

ion

most

and documentation

being

a torch

might

installed

that

(29)

with

simple,it

contrast,

to

such

However,

values (26).

that are

is

stably in the

G. M. HIEFJ-JE

1480

To effectively plasma

torch

than

that

used

to

dissipate

would

obviously

expected

of

calculate

radiatively,

necessary

1,

S is

emissivity

of

the

of

amount of area

a number

system.

Clearly,

such

temperature

Equation

power

the

to

1 can

be

u is

length

of

have

expected

be dissipated

radiator, the

temperature.

cs

a temperature

For 5cm,

equation

to be reached

available.

the

a plasma

torch 1 shows

to for

can be readily

development

is

Stefan-Boltemann

to be reasonable

conveniently

now under

of

substance,

1400K would

625W,

is

a

temperature.

radiator

dissipate

ceramics

a higher

unit.

and a radiating

a temperature

cooledtorch

the

surface

radiating

and T is

number of

reach

radiatively,

(1)

P is

the

the

18rmn diameter

that

to

a conventional

this

In equation

of

have

SEsrJT4

P -

constant,

350-8001~

this

such

reached

a by a

Such a radiatively

in our

laboratory.

ACKNOWLEDGEMENTS This Science the

work was supported

Foundation,

Science

by the

and Engineering

in part

Office

of

Research

by the Naval

National

Research,

Council

of

and by

Great

Britain.

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