Tungsten Filament: Diameter 0.1-0.5 mm, Length 10-50 mm

Component Specifications

Definition

A tungsten filament is a precisely engineered wire component within the cathode assembly of medical X-ray tubes. When electrically heated to incandescence (typically 2200-2500°C), it emits electrons via thermionic emission. These electrons are then accelerated toward the anode target to generate X-rays through bremsstrahlung and characteristic radiation processes. The filament's design directly impacts electron beam focus, tube current stability, and overall X-ray output quality.

Working Principle

Thermionic emission: When heated to high temperatures by electrical current, tungsten releases electrons from its surface. These free electrons form an electron cloud (space charge) that is focused and accelerated toward the anode by high voltage, creating X-rays upon impact.

Materials

Pure tungsten (W) or thoriated tungsten (W-ThO₂, typically 1-2% thorium oxide). Tungsten is selected for its high melting point (3422°C), low vapor pressure at operating temperatures, and excellent thermionic emission properties.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Length	10-50 mm
Diameter	0.1-0.5 mm
Resistance	1-10 Ω at room temperature
Life Expectancy	1000-5000 hours
Operating Temperature	2200-2500°C
Emission Current Density	0.5-2 A/cm²

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

ISO 16526-1, DIN 6836-2, IEC 60601-2-54

Parent Products

This component is used in the following industrial products

Medical X-Ray Tube Cathode Assembly

The Medical X-Ray Tube Cathode Assembly is a critical sub-assembly within medical X-ray tubes that generates the electron beam required for X-ray production.

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Engineering Analysis

Risks & Mitigation

Filament burnout from overheating
Uneven electron emission due to contamination
Reduced lifespan from frequent on/off cycling
Arcing from tungsten vapor deposition on insulators

FMEA Triads

Trigger: Excessive operating temperature or voltage
Failure: Rapid tungsten evaporation leading to filament thinning and breakage
Mitigation: Implement temperature monitoring circuits, use automatic exposure control, maintain proper cooling

Trigger: Mechanical vibration during operation
Failure: Filament deformation or fracture
Mitigation: Secure mounting with vibration dampeners, ensure proper tube balancing

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Diameter ±0.01 mm, Length ±0.5 mm, Resistance ±5%

Test Method

Emission uniformity test at 10% below rated voltage, visual inspection for surface defects, resistance verification at 20°C

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

Verify equipment lists, process limits, capacity, and representative production evidence.

Inspection readiness

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

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Manufacturers of Tungsten Filament

Manufacturer profiles associated with Tungsten Filament.

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Frequently Asked Questions

Why is tungsten used instead of other metals for X-ray filaments?

Tungsten has the highest melting point of all metals (3422°C), maintains structural integrity at operating temperatures, exhibits excellent thermionic emission efficiency, and has low vapor pressure that minimizes tube contamination.

What happens when a tungsten filament fails?

Filament failure typically results from thinning/breaking due to evaporation or thermal stress, causing reduced/no electron emission. This leads to insufficient X-ray output, requiring tube replacement as filaments cannot be serviced separately in sealed tubes.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records. See the editorial policy.

Preliminary Technical Classification

This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

Tungsten Filament