Glass or Metal-Ceramic Envelope: Dielectric Strength ≥30 kV/mm

Component Specifications

Definition

The glass or metal-ceramic envelope is a critical component of an X-ray tube, serving as a hermetic, vacuum-tight housing that contains the cathode, anode, and internal vacuum environment. It provides high-voltage electrical insulation between internal electrodes, maintains structural stability under thermal stress, and allows X-ray transmission through designated windows while preventing atmospheric contamination.

Working Principle

The envelope maintains a high vacuum (typically 10^-6 to 10^-8 Torr) to prevent arcing and electron scattering, while providing dielectric strength to withstand tube voltages up to 150 kV. It must withstand thermal expansion from anode temperatures reaching 2500°C, with cooling mechanisms to manage heat dissipation. The material choice balances X-ray transparency, mechanical strength, and electrical insulation properties.

Materials

Glass: Borosilicate glass (e.g., Pyrex) for thermal shock resistance; Metal-ceramic: Kovar (iron-nickel-cobalt alloy) brazed to alumina or beryllia ceramics using copper-silver eutectic alloys; Beryllium windows for high X-ray transmission in specific applications.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Vacuum Leak Rate	<10^-9 mbar·L/s
X Ray Transmission	>70% at 50 keV (for window areas)
Dielectric Strength	≥30 kV/mm
Operating Temperature	-20°C to 300°C
Thermal Expansion Coefficient	3-7 × 10^-6/K (matched to electrodes)

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, DIN 6836, IEC 60601-2-28

Parent Products

This component is used in the following industrial products

X-ray Tube

A vacuum tube that generates X-rays by accelerating electrons to strike a metal target.

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Engineering Analysis

Risks & Mitigation

Dielectric breakdown under high voltage
Thermal stress cracking
Vacuum leakage compromising tube performance
Beryllium toxicity during manufacturing (if used)

FMEA Triads

Trigger: Thermal cycling stress
Failure: Crack formation leading to vacuum loss
Mitigation: Use materials with matched thermal expansion coefficients; implement gradual heating/cooling cycles

Trigger: Manufacturing defects in brazing joints
Failure: Hermetic seal failure
Mitigation: Non-destructive testing (helium leak detection); quality control of brazing parameters

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Dimensional tolerance ±0.1 mm; surface roughness Ra ≤0.8 μm for sealing surfaces

Test Method

Helium mass spectrometry leak testing per ASTM E493; high-potential testing at 1.5× rated voltage; thermal cycling tests per IEC 60601

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

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Inspection readiness

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Supplier transparency

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Manufacturers of Glass or Metal-Ceramic Envelope

Manufacturer profiles associated with Glass or Metal-Ceramic Envelope.

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Frequently Asked Questions

What are the advantages of metal-ceramic envelopes over glass envelopes?

Metal-ceramic envelopes offer superior mechanical strength, better thermal conductivity, higher temperature tolerance, and improved resistance to thermal shock, making them suitable for high-power and rotating anode X-ray tubes.

Why is vacuum integrity critical for X-ray tube envelopes?

Vacuum integrity prevents electrical arcing between electrodes, minimizes electron scattering that reduces X-ray output efficiency, and prevents oxidation of hot components like the tungsten anode.

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.

Glass or Metal-Ceramic Envelope