YTTRIA-COATED IRIDIUM CATHODESRUGGED THERMIONIC EMITTERSFEATURES / OPTIONSES-535 Yttria-coated Iridium
Disc Cathode mounted on astandard AEI ceramic base

-YTTRIUM OXIDE (Y2O3) COATING-OPERATION IN POOR VACUUM CONDITIONS-NON-RADIOACTIVE-IRIDIUM PLANAR CATHODE-RESISTS OXIDATION-WITHSTANDS EXPOSURE TO ATMOSPHERE WHEN COLD
-EXCEPTIONAL STABILITY-LOW ENERGY SPREAD-ACCURATELY PRE-ALIGNED-INTERNATIONAL STANDARD AEI BASE-NON-STANDARD MOUNTING AVAILABLEES-535, ES-535W, ES-526, and ES-529
Yttria-coated Iridium Disc Cathodes
Kimball Physics Inc. offers a Yttria-coated Iridium Disc Cathode. Inaddition to being a ruggedized thermionic emitter that resists oxidation,these Iridium Cathodes provide stable and uniform electron emission fora wide variety of electron source applications, especially where vacuum
conditions are not ideal. The cathode structure of the ES-535, ES-526,
and ES-529 consists of a yttrium oxide coated iridium disc that is heatedby conduction from an iridium hairpin and mounted on an AEI or aKimball Physics base. The ES-535W consists of a yttrium oxide coatediridium disc with tungsten hairpin in place of the iridium hairpin. Otherbases are available on a custom basis. When ordering a spare cathodeor firing unit for use in a Kimball Physics electron gun, simply specify thegun model and options (for example, high current, yttria) as this will
determine the particular cathode configuration.
The yttria-coated disc cathode is an advantageous choice for some
applications. Yttrium has a lower work function than uncoated refractory
metals, so more electrons are emitted at a given temperature, or a givenelectron emission can be achieved at a lower temperature.
Iridium, a noble metal, is more resistant to oxidation and other forms ofchemical attack than the refractory metals. Thus the cathode will noteasily burn out if accidentally exposed to atmosphere while running, andit can be used at operating temperature in poorer vacuum conditions.
The yttria-coated iridium cathode can be operated in a vacuum of 10-4
torr; 10-5 torr is recommended for the ES-535W with tungsten hairpin heater.
The cathodes also are not damaged by repeated exposure toatmospheric gases or water vapor when cold. The yttria- coated cathodedoes not require any special care other than protection from mechanicalshock which could physically remove the coating.

power to radiation, and thus more heating power is required. A smaller
disc tends to have a more uniform temperature distribution, which results
in a more uniform emission. Larger discs with larger legs tend to have alonger lifetime.
Kimball Physics has determined several combinations of cathodedimensions that have proved to work well in Kimball Physics electronguns. Refer to the Specifications Table to review the various disc andheater wire options that are standard. Custom Y2O3 cathodes areavailable with different disc sizes and various heater designs.
Most models of the yttria-coated cathode structure are available mounted
on an industry-standard ceramic AEI base or on a Kimball Physics
ceramic base (CB-104 or CB-105), as well as on custom or nonstandard
bases. Base options include two or four pins, pins made of molybdenum
or Kovar, various pin lengths and positions, as well as different mounting
heights of the cathode surface from the ceramic base. Some
combinations of various options may not be possible due to design
considerations. All cathodes are shipped vacuum clean and ready toinstall.

The performance of all coated cathodes will degrade as coating isdepleted through use, lost due to mechanical shock, or sputtered away by
ion bombardment. The lifetime of a yttria-coated iridium cathode isbased on the evaporation rate or degradation of the coating materials
and heater wire, which are dependent on the temperature at which thecathode is run and the vacuum. The work function of the cathode also
affects its lifetime; contamination of the cathode surface can increase thework function, increasing the filament current needed to produce thesame beam current.
There are several factors to consider in choosing a cathode size. Alarger disc has a larger emission area, and thus more total current for agiven current density. The current density is a monotonically increasing
function of temperature. However, a larger disc loses more.

ES-529 Yttria-coated Ir Disc Cathode mounted on an AEI base.
ES-535, ES-535W and ES-526 are also available on AEI bases.

Toll Free: 1 888 KIM-PHYS (1 888 546-7497) e-mail: info@kimphys.com
Tel. 1 603 878-1616 Fax: 1 603 878-3700

YTTRIA-COATED IRIDIUM CATHODES
ES-535, ES-535W, ES-526, and ES-529

ES-535W Yttria-Ir disc on CB-104base

ES-529 Yttria-Ir disc on CB-105 baseES-526 Yttria-Ir disc on AEI baseES-535DISC MATERIAL

Yttria-coated Iridium Disc Cathodes

ES-535W

ES-526

ES-529HEATER WIRE SIZE

0.033 in dia. x .004 in thick(0.84 mm dia. x 0.1 mm thick)
0.004 in dia. (0.10 mm dia.) Ir

Yttrium oxide coated Iridium
0.033 in dia. x .004 in thick
0.048 in dia. x .004 in thick(0.84 mm dia. x 0.1 mm thick)(1.22 mm dia.x 0.1 mm thick)
0.003 in dia. (0.08 mm dia.) W
0.005 in dia. (0.13 mm dia.) Ir

0.062 in dia. x .004 in thick(1.57 mm dia. x 0.1 mm thick)
0.006 in dia. (0.15 mm dia.) Ir

LEG LENGTH

approx. 0.20 in (5.1 mm)

approx. 0.11 in (2.8 mm)

approx. 0.12 in (3.0 mm)

approx. 0.15 in (3.8 mm)

HEIGHT ABOVECERAMIC BASE
EMISSION AREA

on CB-104 base: 0.14 in (3.5 mm)
on AEI base: 0.256 in (6.5 mm)
on AEI base: 0.256 in (6.5 mm)-32
5.5 x10 cm
5.5 x10-3 cm2on CB-105 base: 0.25 in (6.4 mm)
on AEI base: 0.256 in (6.5 mm)
1.17 x10-2 cm2on CB-105 base: 0.27 in (6.9 mm)
on AEI base: 0.256 in (6.5 mm)
1.95 x10-2 cm2EMISSION CURRENT

1-2 mA typical

1-2 mA typical

3-5 mA typical

8-10 mA typicalHEATING CURRENT

1.6 A to 1.8 A

1.6 A to 1.8 A

3.8 A to 4.2 A

5.3 A to 5.8 A

POWER SUPPLYCAPABILITYVACUUM LEVEL

Voltage regulated power supply
recommended, 2 V, 2 A
10-4 torr or better

Voltage regulated power supply
recommended, 2 V, 2 A
10-5 torr or better

Voltage regulated power supply
recommended, 2 V, 5 A
10-4 torr or better

Voltage regulated power supply
recommended, 2 V, 6 A
10-4 torr or better

DISC SIZECATHODE LOADING

0.5 A/cm2 recommended, typical; High loadings result in reduced lifetime

WORK FUNCTION

approx. 2.6 eV

OPERATING TEMP

1800 K typical

ENERGY SPREAD

approx. 0.6 eV

LIFETIME

Hundreds of hours with medium currents
It is not necessarily possible to achieve all maximum specifications
simultaneously. Specifications subject to change without notice.

0.1

0.1

Estimated
Emission
Currentvs TDisc
T emperature
Estimated
Emission
Current
vs Discemperature

Emis sion Current (A )ES-535W Yttria-coated Ir Disc with W legs
mounted on a CB-104 ceramic baseEmis sion Current (A )0.01 0.010.001 0.001

4110 11045110 11056110 110 1000
1000
6ES-526 Yttria-coated Ir Disc mounted ona high current CB-105 ceramic baseToll Free: 1 888 KIM-PHYS (1 888 546-7497) e-mail: info@kimphys.com
Tel. 1 603 878-1616 Fax: 1 603 878-3700

ES-535
ES-535
ES-526
ES-526
ES-529ES-5291200 1200

1400 1400

1600 1600

Dis c Temperature
Dis c Temperature(K) (K)

Copyright © January 5, 2018 by Kimball Physics, Inc.

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