Cryogenic
Preparation System
EMS 1250 Cryogenic Preparation System
What is CRYOGENIC SPECIMEN PREPARATION?
In this instance we are referring to Frozen Hydrated Bulk Specimens for Scanning Electron Microscopy, commonly termed L.T.S.E.M. (Low Temperature Scanning Electron Microscopy). When Biological specimens are prepared by conventional methods, they may collapse and distort. In addition to which, there may be a loss of the diffusible elements that they may normally contain, and therefore affecting the validity of the X-Ray Microanalysis.
The use of L.T.S.E.M. offers a solution to this, and in addition allows viewing and analysis of 'liquid' specimens such as emulsions and suspensions, which was not previously practical. In preparing the specimen, we first want to freeze it as quickly as possible. This will reduce the morphological distortion important for structural observations, and also minimize any redistribution of solutes which is essential for X-Ray Microanalysis.
The aim of fast freezing is to reduce the size of ice crystals by reaching as quickly as possible the point at which recrystallization takes place, which is on the order of -130°C (for pure water), and maintaining the specimen below this temperature. Rapid freezing is commonly obtained by plunging the specimen into a cryogenic fluid. This is commonly liquid nitrogen, usually in the form of 'slushy' nitrogen at -210°C, and for the types of specimen we are considering, this has proved to be an effective cryogen.
Having frozen the specimen, we need to maintain it below -130°C (the recrystallization temperature) and prevent sublimation (below -130°C the rate of sublimation of ice is very low, of the order of 0.001nm/second). We should, therefore, maintain the specimen with cryoprotection in a good clean vacuum to avoid contamination. Frozen specimens can subsequently be fractured, etched, coated with gold or carbon, using a preparation system, and then viewed and analyzed on the cold stage of the S.E.M.
The EMS 1250 Cryogenic Specimen Preparation System is fully integrated, having all the facilities for L.T.S.E.M. This includes the Preparation Unit with its control instrumentation, together with the Low Temperature Stage adaptation to the existing SEM stage, together with actively pumped vacuum transfer system.
The preparation Unit has a freezing chamber and preparation chamber. The freezing chamber can be used to produce sub-cooled (slushy) liquid nitrogen. The frozen specimen can be transferred to the Preparation Chamber, and subsequently the SEM, using a Transfer Unit which maintains Cryogenic Protection.
The Preparation Chamber has facilities for fracturing the specimen, which can be coated with gold or carbon, without the need to change heads. The dual carbon head also has facilities for surface etching using a radiant source, or metal evaporation. The system has two controlled heaters, both accurately temperature controlled, and with timing facilities. One heater is located in the Preparation Chamber, the other heater is located in the SEM Coldstage. This allows the temperature to be raised to allow controlled 'bulk' etching of the specimen. The Preparation Chamber and SEM stage are maintained below -160°C, which allows a good margin to -130°C, the point for ice recrystallization.
It is important to avoid contamination of the frozen specimen, and the system has protective shielding. However, more significantly, the system has a clean, contamination-free vacuum by using a hydrocarbon-free Turbo Molecular pumping system backed by a two-stage rotary vacuum pump. The system's unique cylindrical design of Preparation Chamber ensures high efficiency of the turbo unit, together with ease of use of all the chamber facilities.
Features
- Independent preparation system.
- Turbomolecular pumping system contamination and hydrocarbon free.
- Transfer unit (actively evacuated) with gate valve.
- 'Slushing' chamber for Liquid Nitrogen.
- Cylindrical preparation chamber for efficient operation with gate valve.
- Low voltage 'cool' sputtering head with high repeatability (Gold as standard).
- Carbon fiber 'flash' evaporation with radiant heater head with variable control and evaporation pulse button.
- Cooled knife facility.
- Cooled probe facility.
- Liquid Nitrogen dewar for preparation chamber with long term stability.
- Temperature and timed preparation chamber sublimation stage.
- SEM cooled stage with temperature and timed sublimation heater.
- Liquid Nitrogen dewar for SEM with long term stability.
- SEM gate valve to facilitate efficient transfer.
- Modular electronics, full push button and automatic control of pumping and valving sequence.
- Clean line design.
- Polycarbonate safety shield.
Specifications (Preparation Unit)
| Instrument Case | 450mm(W) x 350mm(D) x 175mm(H) |
| Cylindrical Work Chamber | 130mm(Dia.) x 250mm(L) With Vacuum Gate Valve |
| Slushing Chamber | 125mm(Dia.) x 150mm Deep |
| Liquid Nitrogen | 100mm(Dia.)x150mm Deep |
| Dewar | Capacity:1.0 Litre |
| Turbo Molecular Pump | 50L/Sec |
| Weight | 36Kg |
Specifications (Control Unit)
| Instrument Case | 450mm(W)x350mm(D)x175mm(H) |
| Fitted with: | Control Electronics |
| Weight | 28Kg |
Specifications (Tranfer Unit with)
| Vacuum Gate Valve | (Vacuum Pumped) |
| SEM Coldstage | With Vacuum Gate Valve and Liquid Nitrogen Dewar 1 Litre Capacity |
| Weight | 16Kg |
| Total weight of system | 82Kg |
| Sputter Coating | 22mm(Dia.)x0.1mm(T) Target (Gold fitted as standard) |
| Timer | 0-4 mins |
| Sputter Gauge | 0-50mA |
| Carbon Coating | *Deposition 0-10nm/Min Carbon String/Carbon Cord (With Integral Radiant Heater) |
| Ammeter Gauge | 0-50 Amps |
| Evaporate Button Outgas Control | 0-25 Amps |
| Cooled Knife Assembly | |
| Cooled Probe Assembly | |
| Specimen Transfer Stub for Multipurpose Application | (Special Stubs Available) |
| Vacuum Gauge | 0-1 x 10-2 mbar |
| High Vacuum Condition Indicator | |
| Turbo Molecular Pump Unit | Better than 1 x 10-5 mbar |
| Preparation Stage Temperature | Better than-160ºC |
| Temperature Monitor and Control | -200ºC to 0ºC |
| Timer | 0-20 minutes |
| Viewing Light Source | |
| Supply | 115V 60 Hz (6 Amp Max) 230V 50 Hz (3 Amp Max) |
Services
| Argon (for Sputtering) | Nominal 4 psi |
| Nitrogen (for Sputtering) | Nominal 4 psi (Argon can be used if only one gas is required) |
| Vacuum Pump (Recommended) | Complete with vacuum hose and oil mist
filter 135L/Min |
| Size | 470mm (L) x 150mm (W) x 250mm (H) |
| Weight | 23Kg |
Ordering Information
| 92000 | EMS 1250 Preparation System complete with interface to SEM (Specify Microscope Stage to Suit) | POR | Request Quote |
| 91025 | Rotary Vacuum Pump | $2,523.00 | Add to Cart |
| 92010 | Binocular Microscope | POR | Request Quote |
| 92001 | Trolley | POR | Request Quote |
Replacement Sources
| 91045 | Carbon String 1 Metre | $25.00 | Add to Cart |
| 91046 | Carbon Cord 1 Metre | $28.00 | Add to Cart |
Replacement Targets
| 92020 | Gold Target | POR | Request Quote |
| 92021 | Gold/Palladium Target | POR | Request Quote |
Replacement Accessories
| 92022 | Specimen Stub | POR | Request Quote |
| 92023 | Fracture Rivets 10/pack | $25.00 | Add to Cart |
| 72592 | TFM Freezing Medium 100 ml (OCT-Compound) 4 ml | $19.50 | Add to Cart |
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