Isotech 459 Cryostat Low-Temperature Calibration System

The Isotech 459 Cryostat is designed for laboratories that require absolute accuracy at temperatures far below the freezing point. It provides a highly stable and carefully controlled cryogenic environment for the realization of ITS‑90 fixed‑point cells, including the Argon Triple Point, Mercury Triple Point and other low‑temperature reference points. Although engineered for primary and secondary metrology, the 459 is robust and practical enough for routine use in advanced industrial calibration facilities.

Purpose‑built for ITS‑90 fixed‑point cells

Every aspect of the 459 Cryostat is optimized for the precise realization of low‑temperature fixed points. The construction minimizes heat flow into the cell and ensures a uniform temperature field around the reference point, allowing users to achieve sub‑millikelvin uncertainties in accordance with ITS‑90 requirements. The cryostat supports a wide range of fixed‑point cells — Argon, Mercury, Oxygen, Neon and custom cryogenic cells — and can be equipped with dedicated cell holders and insulation assemblies to match the characteristics of each cell type.

Advanced cryogenic architecture

Depending on the configuration, the 459 uses either a liquid nitrogen jacket or a mechanically cooled cryogenic chamber. Both designs create a quasi‑isothermal zone in which the fixed‑point cell can reach thermal equilibrium. Controlled cooling rates, extremely low heat flux and a stable temperature environment ensure long, clean plateaus that make measurements more reliable and easier to interpret.

Ease of use and built‑in safety

Despite its metrological performance, the 459 is straightforward to operate. It incorporates safety systems to protect against over‑cooling and over‑pressure, provides a controlled LN₂ feed and offers stable mechanical support for the cell. The measurement zone is easily accessible, making it simple to position the cell and reference thermometer. The cryostat integrates seamlessly with Isotech instruments such as the microK thermometry bridge, enabling a fully traceable measurement chain.

Thermal performance

The 459 Cryostat is known for its exceptional thermal behaviour. During the fixed‑point plateau, both vertical and radial temperature gradients remain extremely small, which is essential for accurate ratio measurements. High‑quality insulation and a carefully controlled cryogenic environment keep the cell in stable thermal equilibrium, allowing long plateau durations and highly repeatable measurements.

Accessories and configuration options

A wide range of accessories is available to tailor the 459 to specific applications. These include cell baskets for various ITS‑90 fixed‑point cells, monoculars for visual plateau observation, thermometer support assemblies and custom insulation kits. When combined with a microK bridge, the 459 becomes a complete cryogenic calibration system suitable for primary calibrations and international comparisons.

The Isotech 459 Cryostat combines accuracy, stability and practicality in a way that few cryogenic calibration systems can match. With its compatibility with ITS‑90 fixed‑point cells, outstanding thermal performance and flexible configuration options, the 459 is an excellent choice for laboratories that require uncompromising accuracy at low temperatures.