Molybdenum Focusing Cup: Voltage Range -40 kV to -150 kV

Component Specifications

Definition

A molybdenum focusing cup is a critical component within the cathode assembly of medical X-ray tubes, designed to electrostatically focus and direct the electron beam emitted from the filament toward a specific focal spot on the anode target. Its precise geometry and material properties ensure optimal electron flow control, which directly impacts X-ray beam quality, focal spot size, and imaging resolution in diagnostic radiology equipment.

Working Principle

The focusing cup operates on electrostatic principles: when a high negative voltage is applied relative to the anode, it creates an electric field that shapes and accelerates electrons from the heated filament. The cup's concave geometry and precise positioning concentrate electrons into a narrow beam, minimizing dispersion and ensuring they strike the anode target at the intended focal point to generate X-rays efficiently.

Materials

High-purity molybdenum (Mo), typically 99.95% or higher, often with trace alloying elements like lanthanum oxide (La2O3) for enhanced thermionic emission stability. Material must exhibit high melting point (~2623°C), low vapor pressure, and excellent thermal and electrical conductivity.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Material	Molybdenum (Mo ≥99.95%)
Voltage Range	-40 kV to -150 kV
Surface Finish	Ra ≤0.8 μm
Geometric Tolerance	±0.05 mm
Electrical Resistance	<0.1 Ω·cm
Operating Temperature	Up to 2000°C
Focal Spot Size Control	0.1 mm to 2.0 mm

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 16526-3, DIN 6827-1, 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

Thermal deformation at high temperatures
Electron beam misalignment due to manufacturing defects
Material degradation from repeated thermal cycling
Electrical arcing if insulation fails

FMEA Triads

Trigger: Material impurities or improper heat treatment
Failure: Premature thermal cracking or warping
Mitigation: Use high-purity molybdenum with controlled grain structure and implement strict thermal cycling tests during quality control.

Trigger: Geometric inaccuracies in cup machining
Failure: Electron beam defocusing leading to enlarged focal spot
Mitigation: Employ precision CNC machining with post-process metrology verification to ensure dimensional tolerances within ±0.05 mm.

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Dimensional tolerance ±0.05 mm, surface roughness Ra ≤0.8 μm, electrical isolation >100 MΩ at 500 VDC

Test Method

X-ray focal spot measurement per ISO 16526-3, high-voltage leakage test per IEC 60601-2-54, thermal cycling test (1000 cycles, 20-2000°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 Molybdenum Focusing Cup

Manufacturer profiles associated with Molybdenum Focusing Cup.

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Frequently Asked Questions

Why is molybdenum used for focusing cups in X-ray tubes?

Molybdenum is preferred due to its high melting point, excellent thermal stability, low vapor pressure (reducing tube contamination), and good electrical conductivity, making it ideal for high-temperature, high-voltage environments in X-ray generation.

How does the focusing cup affect X-ray image quality?

It precisely controls electron beam focus on the anode, determining focal spot size and shape. A well-focused beam produces sharper images with higher resolution, while poor focus can cause blurring and reduced diagnostic accuracy.

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.

Molybdenum Focusing Cup