Ascend NMR Magnets

For medium and high-field NMR, superconducting magnets are usually used. These magnets typically consist of solenoidal coils wound from niobium-titanium, niobium-tin or rare-earth barium copper oxide materials. The magnets are usually operated in persistent mode, which means that after the energization, a superconducting switch is closed such that the electrical current flows through the coil continuously to create a persistent and stable magnetic field. The magnet coil is immersed in a tank of liquid helium which keeps the coil at a sufficiently low temperature to maintain superconductivity. A liquid nitrogen tank is used to minimize the heat input into the helium tank. In addition to the main coil, the magnet incorporates a number of additional systems, such as cryogenic shims for field homogenization, active shielding coils or vibration isolation systems. Schematics of an NMR magnet are shown in Figures 1 and 2.

Bruker offers an unparalleled range of superconducting NMR magnets, meticulously designed and built to redefine performance in nuclear magnetic resonance applications. Built from the most advanced superconductors and using proprietary, cutting-edge magnet designs, the Ascend and Ascend Evo magnets epitomize excellence in NMR technology.

Bruker’s Ascend magnet line stands for exceptional field quality and stability, compactness, low cryogen consumption, low susceptibility to external field perturbations, as well as convenience and user friendliness. With Ascend Evo technology featuring further advanced coil and cryostat designs and new solutions for magnetic field homogenization, these important features were taken yet another step further. Magnets with Ascend Evo technology are available for selected frequencies.

Advanced shimming technologies guarantee superior field homogeneity within the sample volume, minimizing the need for additional corrections with the room temperature shim system. 

Unique superconductor jointing technology employed by the Ascend and Ascend Evo magnets translates into a remarkable field stability over time, leading to best performance in NMR experiments with extended duration. To put this into perspective, it would take hundreds of years for the magnetic field to decay by 1 %.

Standard and Wide Bore Configurations: Available in both standard bore (54 mm) and wide bore (89 mm) variants, Bruker’s magnets cater to diverse applications in NMR. Wide bore magnets accommodate larger probes, unlocking additional applications, e.g. in microimaging and specific solid-state experiments.

From Medium to Ultra-High Field: Offering a wide spectrum of field strengths, ranging from 300 MHz (7 T) to an industry-leading 1.2 GHz (28.2 T) for SB magnets and up to 800 MHz for WB magnets, Bruker’s products cater to varied experimental needs. Customized magnets for specific field strengths and applications are available upon request, showcasing our commitment to meeting unique research requirements.

Advanced Technology Integration: Equipped with high precision cryogenic shims, active shielding coils, and External Disturbance Suppression (EDS) systems, Ascend and Ascend Evo magnets mitigate stray fields and offer up to 99% screening efficiency against external magnetic perturbations, allowing placement in challenging environments. Active shielding minimizes the magnetic footprint, making Ascend and Ascend Evo NMR magnets ideal for space-restricted laboratories while ensuring unparalleled performance.

From Superconductors to Super Designs: Utilizing LTS (Low Temperature Superconductors, i.e. niobium-titanium, and niobium-tin) and HTS (High Temperature Superconductors), enables Bruker to access and select conductors tailored precisely for different field magnet designs. Bruker’s in-house manufactured superconductors and the resulting high level of vertical integration enable perfect alignment of conductor and magnet design and facilitate the creation of exceptionally high-field and compact NMR magnets.

Thermal Efficiency: Designed to minimize liquid cryogen consumption, our magnets incorporate high-performance cryostats with advanced insulation techniques, reducing heat input and operational costs. Most Ascend and Ascend Evo NMR magnets use an atmospheric helium bath to cool the superconducting coil to 4.2 K. The low helium loss rates of Bruker’s Ascend and Ascend Evo NMR magnets lead to exceptionally long refill intervals, leading to more flexibility when sourcing liquid helium and making the operation of the magnet system more convenient.

High-Performance Magnet Stands and Vibrations Isolation: A variety of magnet stands with integrated vibration isolators are available for Ascend and Ascend Evo magnets. Available vibration isolators include passive elastomeric elements and high-performance pneumatic isolation system for demanding applications. Magnet stands are available in different lengths, and are typically chosen depending on the available ceiling height and the NMR probes which are used with a magnet. Supplementary active vibration isolation solutions are also available for sites where floor vibrations are extremely severe and exceed the thresholds for the integrated advanced passive isolators.

Ultra-Stabilized Sub-Cooling Technology: Bruker's patented Ultra-Stabilized technology is used to reach the highest magnetic fields exemplified in our 1.1 and 1.2 GHz magnets which showcase unparalleled advancements in high-field NMR research. The technology sub-cools the superconducting coil to a temperature of ~ 2 K while keeping the helium bath at atmospheric pressure, which makes these magnets very reliable and convenient to operate.

Comprehensive Accessories and Solutions: Bruker offers a range of accessories including helium gas recovery solutions, cryogen reliquefication systems for both nitrogen and helium, pressure stabilization devices, high-performance vibration isolation platforms for optimized NMR experiments, and other.

Bruker’s Ascend and Ascend Evo Superconducting NMR Magnets pave the way for groundbreaking discoveries, offering researchers unmatched precision, versatility, and technological advancement in nuclear magnetic resonance experimentation.

Ascend Evo 1.0 GHz: Single-Story Compact 1.0 GHz NMR with Minimal Helium Consumption

The Ascend Evo 1.0 GHz is an ideal example to showcase the benefits of Bruker’s Ascend Evo technology: The Ascend Evo 1.0 GHz system offers a unique compact magnet with exceptionally small footprint, weight, and ceiling height requirements, as well as an impressively low liquid helium consumption of less than 80 ml/h. This novel and unique design minimizes siting, installation, and operational costs, and makes 1.0 GHz NMR accessible to a large number of labs.

Maximum Performance: The exceptional homogeneity and field stability are the most important properties of our magnets that have led to the Ascends’ phenomenal reputation in the NMR community. The magnetic field quality combined with unparalleled mitigation of external field disturbances facilitate the ability to conduct sophisticated long-duration NMR experiments even in extremely challenging environments that have been previously considered as unsuited for NMR. Bruker’s 1.0, 1.1 and 1.2 GHz NMR magnets, the world’s highest-field commercial NMR magnets, all make use of Ascend technology.

Easy Siting: The compactness and associated small size and weight of Bruker’s Ascend and Ascend Evo NMR magnets minimize siting costs. Work required for site preparation is minimal, and the access and rigging during the installation are simple and straight-forward. The exceptionally small physical and magnetic footprint make it possible to use available laboratory space efficiently and effectively. The impressively low ceiling height requirements make the installation of most Ascend and Ascend Evo NMR magnets possible in standard laboratories.

Minimal Operating Cost: The operating cost of NMR magnets largely depends on a magnet’s helium boil-off rate. The Ascend and Ascend Evo NMR magnets are based on sophisticated cryostat designs that minimize the heat transfer to the helium bath, leading to the lowest helium consumptions in the industry. At the same time, our magnets have been designed with a special view towards reliability, serviceability and minimizing the overall maintenance and operational costs.

Bruker offers an extensive range of accessories for the convenient, safe and efficient operation of superconducting NMR magnets. Please contact your Bruker representative for detailed information on NMR magnet accessories for achieving best performance and stability, ensuring operational safety or facilitating cryogen handling.

Electronic Atmospheric Pressure Device (EAPD)

Changes in the atmospheric pressure can lead to minute changes of the temperature of the helium inside an NMR magnet, as well as to temporary changes in the boil-off rate. Due to the excellent sensitivity of NMR systems, these effects can influence NMR experiments. For NMR systems ≥ 600 MHz, Bruker thus recommends the use of the Electronic Atmospheric Pressure Device (EAPD) which actively controls the helium pressure in the magnet system to a constant value, leading to improved stability for particularly sensitive NMR applications.

Bruker Nitrogen Liquefier (BNL)

Bruker’s Ascend and Ascend Evo magnets are equipped with a liquid nitrogen stage to reduce the heat load on the helium tank. The Bruker Nitrogen Liquefier (BNL) is a retrofittable component which makes use of a cryocooler to reliquefy the nitrogen which evaporates from the NMR magnet. Typically, the BNL makes it possible to operate an NMR magnet with zero nitrogen boil-off, completely eliminating the need for nitrogen refills. The BNL has been carefully engineered with respect to vibration isolation to ensure that the NMR performance in uncompromised.

Bruker Smart Nitrogen Liquefier (BSNL )

Just like the BNL, the Bruker Smart Nitrogen Liquefier (BSNL) reliquefies nitrogen from the NMR magnet. Instead of a dedicated cryocooler, the BSNL makes use of excess cooling power from the CryoPlatform, which is used to cool Bruker’s CryoProbes. The consumption of liquid nitrogen can thus be reduced significantly – and often even completely eliminated – without additional power consumption. The BSNL can be ordered as an option with a new CryoPlatform and can be retrofitted to existing NMR magnets.

Vibration-Isolation Solutions

Floor vibrations can lead to unwanted artefacts in NMR spectra depending on their actual frequencies and amplitudes. Bruker’s Ascend and Ascend Evo magnet stands are available with integrated high-performance passive vibration isolators that are generally very effective at most sites, even on upper floors of buildings. For particular challenging vibrational environments that experience intense floor vibrations at low frequencies, Bruker offers supplemental active vibration isolation solutions employing piezoelectric technology and a “quiet platform” the magnet system is placed on.

Bruker Magnet Pump Control (BMPC/2)

Many of Bruker’s high field magnet coils are operated at a temperature of 2 K to increase the critical current of the superconducting wires. In these magnets, the operating temperature is achieved and maintained by evaporating helium at significantly reduced pressure in a special refrigeration unit inside the cryostat. The Bruker Magnet Pump Control, now in its second generation (BMPC/2), houses the pumps and the control system which are required for the safe and reliable operation of these magnets.

HelioSmart Recovery Solution

The Bruker HelioSmart Recovery system is a very compact, easy-to-site helium collection unit that has been carefully optimized for the use with NMR spectrometers.

Helium is a scarce non-renewable resource. To protect this resource in a socially responsible way and to make lab operations more sustainable, the Bruker HelioSmart Recovery system collects helium boil-off from NMR magnets and stores the gas in high-pressure cylinders. From there, the gaseous helium can be re-used for other purposes or returned to a gas supplier. NMR users who have access to a helium liquefaction facility can purify and reliquefy the helium and re-use it in an NMR magnet to become more independent, especially during periods of global helium shortage. To keep costs low and to make siting as easy as possible, the Bruker HelioSmart has been dimensioned to collect the steady-state boil-off of several NMR magnets in parallel, excluding helium transfers, resulting in a typical recovery rate of 80 - 85 percent. The Bruker HelioSmart Recovery system has been carefully engineered to ensure safe operation with NMR magnets and has been optimized to eliminate spectral artifacts.

The HelioSmart Recovery is currently only available in selected countries.