ZEISS Correlative Cryo Workflow Instruction Manual

ZEISS Correlative Cryo Workflow

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About this Document

This instruction manual is considered to be part of the Cryo Trap. It offers topics that are specific to the Cryo Trap. For information regarding the ZEISS field emission scanning electron microscope (FESEM), please refer to the relevant manual before starting to work with the Cryo Trap. Read the instructions carefully. Keep the instruction manual nearby the Cryo Trap and hand it over to future owners of the instrument. This instruction manual is designed for users who have been trained by an authorized Carl Zeiss Microscopy expert to operate the Cryo Trap, which is built into the FESEM. Operators must not deviate from the instructions provided in this document.

Text Conventions and Link Types

Click Start.

Press the STANDBY button. Press [Enter] on the keyboard.

| The names of controls and important infor- mation are shown in bold letters.
Press < Ctrl+Alt+Del>| Press several keys on the keyboard simultane- ously.
Select Tools > Goto Control Panel > Air- lock.| Follow a path in the software.
Text input Text output| ■         Text to be entered by the user

■         Text displayed by the system

Programming and Macros| Anything typed in literally during program- ming, including, for example, macro codes, keywords, data types, method names, vari- ables, class names, and interface names.

Definition of Terms

speci- men and instrument surfaces
Cryo Trap| Reduces the contamination in the specimen chamber
Dewar| Isolated can, containing the liquid nitrogen
FESEM| Field emission scanning electron microscope

Safety

The Cryo Trap is used to cool down the area below the objective lens while the object chamber is at vacuum. This decreases contamination by binding the volatile hydrocarbons.
The Cryo Trap is an option for the following ZEISS field emission scanning electron microscopes (FESEM) with airlock:

•  GeminiSEM 300
•  GeminiSEM 450
•  GeminiSEM 500
• Using the Cryo Trap for any other purpose is not allowed and could be hazardous.

Safety Information

This manual only shows the hazards which are specific to the Cryo Trap. However, the Cryo Trap must be used together with a ZEISS electron microscope. For the risks regarding the operation of the ZEISS electron microscope please refer to the relevant instruction manual before starting to work with the Cryo Trap.

WARNING

• The danger of burns or frostbites when liquid nitrogen gets in contact with the skin.
•  Wear proper protective equipment when handling the liquid nitrogen and Cryo Trap. 4 Do not touch the cooling rod and the cooling plate inside the chamber as long as the de- war is not empty.
•  The dewar has to be in an upright position. Never unscrew the dewar as long as liquid nitrogen is in it.
•  Use suitable tools when filling up the dewar.
•  The dewar must be empty and must have room temperature before exchanging the cool
• Explosion risk if the pressure inside the dewar rises due to evaporating liquid nitrogen.
•  Only use the cover which is provided by ZEISS for the dewar filling hole.
•  Regularly check that ice does not build up at or around the cover for the dewar filling hole.
• Suffocation hazard due to lack of oxygen
• danger of nitrogen accumulation in low-lying areas or subterranean rooms.
•  Ensure the room is ventilated properly.
•  Ensure the room is equipped with a ventilation system with bottom suction and air ex-
• Cover the dewar so that the evaporating nitrogen can escape, but the penetration of air is inhibited and no flammable material can fall into the dewar.
•  Store and transport liquid nitrogen only in suitable dewars.
•  Do not smoke or have open fire in the same room the dewar is located.
• Do not vent the specimen chamber as long as the dewar is filled with liquid nitrogen.
•  Before you vent the specimen chamber, wait until the dewar is empty and the cooling rod and cooling plate are warmed up to room temperature.
•  Always exchange the specimen via an airlock.

Warning Labels and Lights

All locations that may pose specific hazards are marked with additional warning labels (pic-tograms) on the Microscope System. These warning labels indicate potential hazards and form part of this Instruction Manual. They are to be kept in clean and easily legible condition. Damaged or illegible warning labels must be replaced immediately. Always consider all warning labels on the Microscope System.

Description

Purpose For SEM imaging, especially for low kV imaging, hydrocarbon contamination is very critical as it massively influences image quality. The Cryo Trap is used to minimize contamination in the specimen chamber caused by volatile hydrocarbon compounds. Position The Cryo Trap is a purely mechanical device that is attached to the EDS3 port of the GeminiSEM chamber. The Cryo Trap assembly includes a dewar vessel mounted outside, an adapter flange connecting it to the specimen chamber, a them conducting rod plus a metal plate reaching near the electron beam.

1. Blind Flange (currently not used)
2. Lid (with borehole)
3. Dewar
4. Adapter Flange
5. Cooling Rod

Function The chamber vacuum provides the thermal isolation of a dewar vessel, which is filled with liquid nitrogen. The extreme cold will be transferred into the specimen chamber by a copper rod that is attached to the dewar bottom. A metal plate is attached to the tip of this copper rod. This metal plate is cooled down to -170°C. It acts as a trap for hydrocarbon contamination. Hydrocarbon compounds stick to the cold surface and are thus prevented from depositing on the specimen sur-face whilst the system remains cold.LN2 continuously evaporates and leaves the dewar through the borehole of the lid as gaseous nitrogen. There is no electronics and software integrated to the Cryo Trap. There is no measurement of the final temperature, and there is no monitoring of the filling level of LN2 in the dewar. There are always volatile hydrocarbon compounds

The temperature of the cooling plate state, from volatile to solid. The compounds are deposited at the cooling plate. The cold surface of the cooling plate acts as a trap for hydrocarbons and hence decreases the risk of contamination.

Technical Data

Specification|
---|---
Capacity| 0.6 l
Size of dewar assembly| overall height 334 mm, maximum diameter 152 mm
Cooling agent| liquid nitrogen (LN2)
Cooling-down time| 30 minutes to reach -130°C 45 minutes to reach -170°C
Temperature of cooling plate| down to -180°C
Standing time| After refilling the dewar the temperature of the cooling plate stays below -130°C for 10…12 hours.
Warming-up time| At regular system vacuum:

With a refilled dewar it takes about 2 days to reach room temperature again (36 hours to reach 20°C).

CryoWarmUp macro:

A macro allows to reduce the warming-up time. With a refilled dewar it only takes about 6 hours to reach room temperature again (4.5 hours to reach 20°C).

System vacuum| Improvement of an approximate factor of 2

System Requirements

• All the detectors, including the moveable ones, are compatible. BsD, NanoVP and CC should be mounted on port 66 mm MP1 or MP2.
  IMPORTANT:

• The EDS detector must be mounted on port EDS1.

• With cooling plate in position, untilted stage movement is uncompromised.A stage tilt of 45° is possible, but the possible range of WD strongly depends on sample/sample holder.

Installation

The Cryo Trap is either factory-installed or retrofitted by authorized ZEISS service personnel.

Operation

• Wear proper protective equipment when handling the liquid nitrogen and Cryo Trap. 4 Do not touch the cooling rod and the cooling plate inside the chamber as long as the de- war is not empty.
•  The dewar has to be in upright position. Never unscrew the dewar as long as liquid nitrogen is in it.
• only use the cover which is provided by ZEISS for the dewar filling hole.
•  Regularly check that ice does not build up at or around the cover for the dewar filling hole.
• Cover the dewar so that the evaporating nitrogen can escape, but the penetration of air is inhibited and no flammable material can fall into the dewar.
•  Store and transport liquid nitrogen only in suitable dewars.
•  Do not smoke or have open fire in the same room the dewar is located.
• The EDS detector should be retracted during installation.
•  Take care of the nearby detectors during the whole mounting procedure.

Filling the Dewar with Liquid Nitrogen

1. Open the lid.
2.  Fill in liquid nitrogen as necessary with a suitable container (dewar) and funnel.
3.  Wait 10 to 15 minutes.
4.  Refill.
5.  Close the lid (white Teflon cover).
6.  Make sure that the lid is correctly seated and the borehole is not facing towards the speci- men chamber.
7.  Start the CryoWarmUp macro with the button CryoWarmUp in the SmartSEM Toolbar.
8. This will stop the turbo pump, execute a partial vent and keep the system chamber at a pressure of about 30 mbar, followed by a regular system pump-down.
9. The cooling plate will be warmed up to 20°C within 6 hours.
10. After that you can open the specimen chamber.

Dismounting the Cooling Plate

The pin is mounted onto the cooling plate.

Set the bottom surface of the cooling plate to the same level as the bottom surface of the end cap of the objective lens.

Measure the resistance between SE2 collector grid and the cooling plate with a DVM. These two parts should be isolated from each other. INFO: The cooling plate is not allowed to touch any detector or the end cap of the objective lens.Also measure the resistance between VPSE collector grid and the cooling plate with a DVM. These two parts should be isolated from each other.

De-installation and Disposal

The Cryo Trap is de-installed and disposed of by authorized ZEISS service personnel only.

Troubleshooting

again until all components are warm and fully dry.

Defrost the dewar.

Image drift| Fluctuating temperature in the specimen chamber| Check position of borehole of the lid.
Long pumping time| The specimen chamber has been vented while the temperature of the Cryo Trap was far below room temperature.| Defrost the dewar.

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