Cryo-SEM Preparation System

The PP3010T is a highly automated, easy to use, column‐mounted, gas‐cooled cryo preparation system suitable for most makes and models of SEM, FE‐SEM and FIB/SEM. The PP3010T has all the facilities needed to rapidly freeze, process and transfer specimens. The aQuilo cryo preparation chamber is turbomolecular pumped and includes tools for cold fracturing, controlled automatic sublimation and sputter coating. After processing, the specimen is transferred from the cryo preparation chamber onto a highly stable SEM cold stage for observation. Cold trapping in the cryo preparation chamber and SEM chamber ensures the whole process is frost free. Specimen process times are typically between five and ten minutes.

Key features

• High resolution performance on SEM, FE‐SEM and FIB/SEMs
• aQuilo gas cooled cryo preparation chamber
• Efficient cooling (typically down to at least‐190°C)
• Up to 24 hours run times on one fill of LN2 ‐ allowing unattended overnight operation
• Large recipe driven touch‐screen interface
• Automated sublimation, coating and system start up
• Superb specimen visibility (including preparation chamber CCD camera)
• Fully compatible with SEM beam deceleration/stage bias modes up to 5kV
• Off column cooling and pumping ‐ minimum mass on the SEM
• On‐screen data logging and diagnostics
• Vacuum storage of the cryo transfer device
• Prepdek™ workstation ‐ self contained work area, extra bench space not required
• Specialist support and three year warranty

aQuilo cryo preparation chamber

• Subject to microscope geometry, fits onto a single microscope chamber port ‐ compact installation, frees up microscope ports
• Mounted directly on the microscope ‐ essential for frost‐free transfer and ease of use
• Integrated valves ‐ enhanced vacuum performance
• Gas cooled cold stage and cold traps ‐ rapid cooling down to ‐190°C or lower
• Turbo pumping system located off‐column ‐ less mass on the SEM
• Typical vacuum when cold: 10^‐6mbar or better ‐ specimen transfer into the SEM always high vacuum to high vacuum
• Unsurpassed specimen visibility ‐ large front window, top viewing ports and multiple LED chamber lighting
• Preparation chamber CCD camera for specimen observation ‐ bulky binocular no longer needed
• Automated high resolution sputter coating using Quorum's market leading "Q" series technology
• Fracturing/specimen manipulation device

Product Description

The PP3010T is the very latest in cryo‐SEM technology and combines the highest quality results with unparalleled ease of use.

Freezing and specimen handling

The PP3010T Prepdek^™ workstation is fitted with a slushy nitrogen freezing station, connected to the pumping system. Rapid freezing reduces ice crystal damage and results in improved specimen preservation.

For handling pre‐frozen material the Prepdek™ freezing system allows specimens that have been frozen by alternative methods, such as high pressure freezing (or stored field specimens) to be manipulated ‐ under or just above liquid nitrogen ‐ and then vacuum transferred into the aQuilo preparation chamber for subsequent processing and observation.

Specimen shuttles and stubs

The PP3010T is supplied with universal 10mm specimen stubs with surface slots, holes and a flat area on the reverse side ‐ useful for most specimen types. Holes and slots can be used for liquids and to hold solid material for cross‐section fracturing. Blank and slotted stubs are also included. In addition a range of optional holders is available, including shuttles for large specimens and top‐loading holders for high pressure freezing rivets and planchettes.

You can view examples of these by downloading the PP3010T specimen shuttles and stubs PDF at the bottom of this page.

Cryo transfer device ‐ including vacuum storage

The vacuum transfer device is compact, reliably vacuum tight and has a convenient bayonet connection to the specimen shuttle to ensure rapid pick up and transfer.

Set into the Prepdek™ work surface is a pumped storage tube for the cryo transfer device (see Prepdek™ workstation section below).

Technical note: Advantages of a SEM mounted cryo preparation chamber

The PP3010T aQuilo preparation chamber conveniently combines the advantages of an 'on‐column' and 'off‐column' cryo preparation system. The aQuilo chamber is directly attached to the SEM, but with the turbomolecular pumping and advanced cooling system mounted remotely. In this way the mass and volume attached directly to SEM is kept to a minimum.

There are significant advantages of direct connection to the SEM. In particular, specimen transfer is always from high vacuum to high vacuum, which greatly reduces the risk of specimen contamination (frosting). In addition, it makes operation easier and allows the operator a more flexible approach to specimen preparation and observation. For example, during a typical process run it may be advantageous to move the specimen between the preparation chamber and the SEM on a number of occasions, ‐eg to fracture deeper into a specimen, to recoat or simply to first observe the freshly frozen specimen in the SEM for an initial "look‐see", prior to retracting back into the preparation chamber for processing.

The aQuilo cryo preparation chamber is connected directly to the SEM and includes a highly efficient nitrogen gas cold stage, extensive cold trapping (above and below the specimen) and facilities to fracture, sublimate and sputter coat specimens. The chamber is fitted with two fully integrated and interlocked gate valves. The outer load‐lock valve includes a pumped airlock which accepts the cryo transfer device; the inner SEM valve ensures rapid high‐vacuum to high‐vacuum specimen exchange.

Efficient gas cooled stage and cold traps

At the heart of the aQuilo cryo preparation chamber is the nitrogen gas cooled specimen stage. The stage has a dovetail fitting to accept a cryo shuttle and specimen and can be precisely controlled over a temperature range from 100°C to ‐190°C or lower. Large gas cooled cold traps located above and below the specimen stage ensure clean, high vacuum conditions in the chamber.

Both the cold stage and cold traps are cooled with the fully integrated CHE3010 off‐column cooling system (see below), which give typical hold times of up to 24 hours between fills.

High visibility ‐ plus CCD camera

The aQuilo chamber has superb chamber visibility. In addition to the large front window (75 x 150mm) there are two top viewing ports. The chamber is lit by three LEDS and a CCD camera allows the specimen cold stage area to be viewed on the control screen. Images can be saved and stored using a button on the control screen.

Cold fracturing

Twin fracturing tools (actively cooled) are available and allow a range of specimen types to be cold fractured.

The PP33010T is fitted as standard with a front mounted fracturing/manipulation device. The ball‐jointed mount offers flexible movement of the blade and allows the no.5 scalpel to be used both as a surface pick (probe) and a fracturing knife. Alternative blades can be fitted (not supplied).

An optional micrometer advanced fracturing tool (12145) is available (in addition to the standard side‐mounted tool).

Fractured fragments are captured in the large cold trap located below the specimen stage.

Automatic sublimation and sputtering

Sublimation temperatures and times can be preset and stored for easy retrieval. The process is fully automatic and graphically displayed on the control screen, showing the actual versus the predicted temperature curve.

The high resolution sputter coater is an in‐house design, being based on the market leading Quorum "Q" series of bench top coaters and will give fine grain films essential for FE‐SEM applications. A platinum target is fitted as standard ‐ optional metals include gold, gold/palladium, chromium and iridium. An optional fully integrated carbon fibre evaporation head can also be fitted.

An optional terminating film thickness monitor (FTM) is available. The system is fully integrated ‐ no external control boxes.

High vacuum performance

The preparation chamber is pumped by a remotely‐positioned 70L/s turbomolecular pumping system. Typical preparation chamber vacuums during operation are in the region of 10‐6mbar or better. Positioning the turbomolecular pump away from the SEM ensures total elimination of mechanical vibration and significantly reduces the mass connected to the SEM. A vacuum buffer tank (remotely located in the Prepdek™) is automatically pumped when required. The pumping system is connected to the preparation chamber by stainless‐steel bellows, which allows flexible positioning of the pumping system.

A 5m³/hr¹ rotary vacuum pump is required to "back" the turbomolecular pump and for slushing and rough pumping operations. The rotary pump can be located up to five metres from the system, allowing remote location if required. Dry pumping alternatives are available.

Prepdek™ workstation

The Prepdek™ workstation has been designed to allow specimen mounting, freezing (and pre‐frozen specimen manipulation) and transfer device storage on one ergonomically designed work surface. The control electronics are mounted in a sealed, but accessible, cabinet beneath the Prepdek™. A flexible LED light gives the user an excellent view of the preparation process.

Conveniently set into the Prepdek™ works surface is a pumped storage tube and allows the cryo transfer device to be stored under clean, dry vacuum conditions when not in use.

A variable position specimen shuttle mounting pillar gives a solid base for specimen mounting and includes a height gauge to ensure specimens are within the acceptable height range.

The control PC is mounted on a flexible arm and can be positioned to suit the user (eg angled towards the SEM operator during specimen observation ‐ allowing key system parameters to be viewed at a glance).

Panel PC touch screen user interface

The PP3010T is controlled using a large (15") touch screen panel PC, mounted on the Prepdek™ workstation. User‐defined 'recipes' can be entered and stored for instant future access. The screen can be set to suit operator preferences, for example, vacuum measurement can be displayed in millibar or Pascal.

CCD images of the aQuilo cryo preparation chamber and SEM cold stages are displayed and can be expanded to full screen. Although many of the key steps in the specimen preparation process are automated (system set up, sublimation, sputter coating, etc), further help is available through a series of on‐screen videos.

SEM cold stage, cold trap and cooling system

A highly stable, thermally isolated, nitrogen gas cooled stage attaches to the SEM stage. The SEM stage and cold trap are cooled by two separate cold gas circuits ‐ both capable of reaching temperatures down to ‐190°C or lower. This configuration allows the operator to select stage and cold trap temperatures that are optimised for specific specimens. For example, for some non‐biological materials it is useful to hold the specimen at very low temperatures ‐ for example, a cold stage temperature of ‐175°C. This is possible with the PP3010T as cold trap temperatures of ‐190°C or lower can be selected.

The SEM cold stage has a temperature range of 100°C.to ‐190°C and a temperature stability of < 1°C.

Compatibility with SEM stage bias mode

The PP3010T cold stage is fully compatible with SEM stage bias mode up to 5kV

Technical note: gas cooling v conduction cooling

Gas cooling allows specimen stage and cold trap (anticontaminator) temperatures down to ‐190°C. In practice, to ensure efficient cold trapping, there needs to be a minimum of 15‐20°C temperature difference between the two. For many standard applications SEM stage temperatures in the region of ‐120°C to ‐140°C are used, with the cold trap set to between ‐170°C and ‐180°C.

However, cryo preparation systems are increasingly being use to process and observe frozen vitreous material (eg high pressure frozen specimens) where it is essential to work at temperatures in the range of ‐150°C to ‐165°C in order to prevent the devitrification of ice to its less desirable crystalline state. For such specimens the cold stage can be set to ‐165°C.and the cold trap to ‐190°C. This is not possible with less thermally efficient conduction cooled cryo systems.

CHE3010 off‐column cooling

The CHE3010 is a fully integrated, remotely mounted cooling system which comes as standard with every PP3010T.

The CHE3010T is used to cool the SEM stage, SEM cold trap and aQuilo cryo preparation chamber cold stage and cold traps and will typically reach temperatures down to ‐190°C or lower.

The CHE3010 is remotely positioned (typically on the floor behind the microscope) and will run for up to 24 hours between fills. This greatly simplifies the cryo process (no more checking on dewar status and topping up), but also allows overnight, unattended operation ‐ particularly useful for some automated FIB/SEM "slice and view" protocols.

Single port interface to the SEM

Where SEM geometry allows, both the aQuilo cryo preparation chamber and the SEM cooling system can be fitted to a single chamber port (minimum diameter is 38mm). This gives a compact, tidy installation and frees up a potentially valuable chamber port.

Options and accessories

Specimen shuttles and stubs

The PP3010T is supplied with a selection of holders (please see Specification for details). A range of additional specimen shuttles and stubs is also available.

Carbon evaporation and film thickness monitor

A carbon evaporation attachment (11920) and a terminating film thickness monitor (12147) can be fitted.

Pressurised LN₂ dewar

The PP7450/75L is a highly recommended option that generates dry nitrogen gas used for cooling the SEM cold stage, cold trap and aQuilo cryo preparation chamber and cold traps. In addition LN2 can be decanted for slushing (freezing). If the PP7450/75L is not included then appropriate, nitrogen cylinder gas can be used.

For full details of these and other accessories please see Ordering Information below

Installation and training

Installation and training typically takes four days and is carried out at the customer site. In most cases installation and training is by specialist Quorum Technologies cryo installation engineers, normally working in conjunction with our local distributor or microscope manufacturer's engineers. 

Additional Information