Tungsten hairpin filaments are the standard type filaments widely used in Scanning Electron Microscopes, Transmission Electron Microscopes and Microprobe systems. Tungsten filaments are also called cathodes or electron emitters or electron sources. The high quality filaments we offer are made to the original equipment manufacturer's specifications using special tools to guarantee the correct shape for the filaments and to generate the optimum electron beam. The filaments are annealed in vacuum, stress-free and precisely aligned before they are shipped. Please consult the list below for the correct type of filament for your SEM, TEM, or EPMA.
The tungsten filaments are manufactured from high grade tungsten. Of all metals in pure form, tungsten has the highest melting point (3422°C), the lowest vapour pressure at temperatures above 1650°C and has the highest tensile strength. Tungsten also has the lowest coefficient of thermal expansion of any pure metal. This combination of properties makes tungsten the ideal material.
Electron Microscopy Filaments
| Base Type | Filament | Base Type | Filament |
|---|---|---|---|
| AEI |  | ZEISS (DSM & TEM) LEO (1450 & TEM) TESCAN |  |
| FEI/PHILIPS |  | AMRAY (except 1200) |  |
| JEOL K-type |  | ISI/ABT/TOPCON 2-prong |  |
| HITACHI S-type |  | ISI/ABT/TOPCON 3-prong |  |
| HITACHI in cartridge |  | ETEC |  |
Electron Source Performance Comparison
| Emitter Type | Thermionic | Thermionic | Schottky FE | Cold FE |
|---|---|---|---|---|
| Cathode material | W | LaB6 | ZrO/W (100) | W(310) |
| Operating temperature [K] | 2,800 | 1,900 | 1,800 | 300 |
| Cathode radius [nm] | 60,000 | 10,000 | < 1,000 | < 100 |
| Effective source radius [nm] | 15,000 | 5,000 | 15 (*) | 2.5(*) |
| Emission current density [A/cm2] | 3 | 30 | 5,300 | 17,000 |
| Total emission current [µA] | 200 | 80 | 200 | 5 |
| Normalized brightness [A/cm2.sr.kV] | 1.104 | 1.105 | 1.107 | 2.107 |
| Maximum probe current [nA] | 1000 | 1000 | 10 | 0.2 |
| Energy spread @ cathode [eV] | 0.59 | 0.40 | 0.31 | 0.26 |
| Energy spread @ gun exit [eV] | 1.5 - 2.5 | 1.3 - 2.5 | 0.35 - 0.7 | 0.3 - 0.7 |
| Beam noise [%] | 1 | 1 | 1 | 5 - 10 |
| Emission current drift [%/h] | 0.1 | 0.2 | < 0.5 | 5 |
| Operating vacuum hPa/mbar | < 1.10-5 | < 1.10-6 | < 1.10-8 | < 1.10-10 |
| Typical Cathode life [h] | 100 | > 1000 | > 5000 | > 2000 |
| Cathode regeneration | not required | not required | not required | every 6 to 8 hours |
| Sensitivity to external influence | minimal | minimal | low | high |
* virtual source
Dimensions for EM Filament Bases (for Tungsten/Lab6) Filaments?
| Base Type | Diameter of Ceramic disc | Diameter of Pins | Center Distance of Pins |
|---|---|---|---|
| AEI | 12.0mm | 1.0mm | 6.45mm |
| FEI/PHILIPS | 26.0mm | 1.0mm | 5.0mm |
| JEOL K-type | 28.0mm | 1.2mm | 8.0mm |
| HITACHI S-type | 9.8mm | 1.2mm | 2.7mm |
| ZEISS (DSM & TEM) LEO (1450 & TEM) TESCAN | 19.8mm | 1.0mm | 5.0mm |
| AMRAY (except 1200) | 26.1mm | 1.0mm | 5.0mm |
| ISI/ABT/TOPCON 2 pins | 23.3mm | 1.2mm | 11.9mm |
| ISI/ABT/TOPCON | 23.4mm | 1.2mm | 12.0mm |
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