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Microstat He Manual

7

Service and Maintenance

A number of simple procedures can be followed to resolve issues which may be encountered during routine operation. With proper care

and maintenance, the system should provide years of reliable operation.

7.1

Rubber O-rings

Whenever you remove part of the cryostat, or should you suspect that there is a leak on the system, check the O-rings on the sample

space and OVC. Ensure that the O-ring is clean, undamaged and lightly greased. Replace any damaged O-rings.

7.2

Removing the OVC and radiation shield - MicrostatHe and He-R

The OVC and radiation shield only need to be removed if you wish to:

• Change the windows

• Modify or repair the wiring

• Repair mechanical damage

Warm the cryostat to room temperature, as described above, then open the OVC pumping port to allow air into the system. If the internal

parts of the cryostat might still be cold, then use dry Nitrogan gas instead and ensure the system is warm throughout before opening the

OVC.

If the OVC is fixed to the microscope stage then it is not necessary to remove it. Release the NW4O clamp around the neck of the cryostat

and withdraw the cooling unit from the OVC.

This gives access to the radiation shield, which is removed by loosening the four screws and pulling the shield. The holes in the shield

have been slotted so the retaining screws do not need to be removed.

The sample holder, cold finger and wiring are now accessible. To remove the sample holder, loosen the retaining screw. As with the

radiation shield there is no need to remove the screw as the sample holder has been slotted.

The cold finger has two tapped holes to allow the sample holder to be turned over to face either window. The OVC has a pin which locates

in either one of two holes in the NW40 of the cooling unit to ensure it is replaced with the sample holder parallel to the window surface.

Before re-assembling, check the ’O’ring is clean, undamaged and lightly greased. Ensure that it is firmly pushed into place, to form a

vacuum-tight seal.

7.3

Window replacement - OptistatCF-V

If you need to clean the windows, they can all be removed as follows:

© 2017 Oxford Instruments Nanoscience

MAN-MHE-1.1.0 (28ff3d8) Sep 2017

27

Содержание MicrostatHe

Страница 1: ...User Manual Original Instructions MicrostatHe ...

Страница 2: ...e Tubney Woods Abingdon Oxon OX13 5QX United Kingdom declare under our sole responsibility that the following equipment MicrostatHe to which this declaration relates is in conformity with the relevant provisions of the following standard s or other normative document s when installed in conformance with the installation instructions contained in the product documentation EMC EN61326 1 2013 Immunit...

Страница 3: ...ce as well as incorrect use or operation of the equipment may relieve Oxford In struments NanoScience or its agent of the responsibility for any re sultant non compliance damage or injury The system must only be used with all external covers fitted Restrictions on use The equipment is not suitable for use in explosive flammable or haz ardous environments The equipment does not provide protection a...

Страница 4: ...QUE Cet équipement contient des dispositifs qui sont sensibles aux décharges électrostatiques ESD Utiliser des procédures ESD homologuées lors de l installation ou de la maintenance de ce pro duit Solid waste Dispose of this item according to local and national regulations Conformity IEC61010 1 2010 3rd Edition Safety require ments for electrical equipment for measurement control and laboratory us...

Страница 5: ...Microstat He Manual Oxford Instruments Nanoscience Sep 2017 ...

Страница 6: ... 3 7 Low temperature 9 3 8 Pressure relief 9 3 9 Weight and lifting 9 3 10 Magnetic fields 10 3 11 Asphyxiation 10 3 12 Fire 11 3 13 Safety equipment 11 3 14 Maintenance 11 4 System Description 12 4 1 The Cryostats 12 4 2 Continuous flow cryostats 15 4 3 The cryogen transfer siphon 15 4 4 The gas flow pump and flow controller 15 5 Installation 16 5 1 Unpacking the system 16 5 2 Preparing the syste...

Страница 7: ...rogen 25 7 Service and Maintenance 27 7 1 Rubber O rings 27 7 2 Removing the OVC and radiation shield MicrostatHe and He R 27 7 3 Window replacement OptistatCF V 27 8 Microstat He Specifications 31 8 1 Performance 31 8 2 Operating Cycle 31 8 3 Physical 31 8 4 Electrical Power 31 8 5 Notes 32 8 6 Further Information 32 9 Appendices 33 9 1 Electrical connections on the cryostat 33 9 2 Troubleshootin...

Страница 8: ...ocument or portion thereof must include this copyright notice This document is provided as is without any warranty of any kind either express or implied statutory or otherwise without limiting the foregoing the warranties of satisfactory quality fitness for a particular purpose or non infringement are expressly excluded and under no circumstances will Oxford Instruments be liable for direct or ind...

Страница 9: ...s designed and only in accordance with the instructions given in the manual and other accompanying documents Nothing stated in the manual reduces the responsibility of users to exercise sound judgement and best practice It is the user s responsibility to ensure the system is operated in a safe manner Consideration must be made for all aspects of the system s life cycle including handling installat...

Страница 10: ...Tubney Woods Abingdon Oxon OX13 5QX UK Tel 44 0 1865 393200 sales Tel 44 0 1865 393311 support Fax 44 0 1865 393333 sales and support Email nanoscience oxinst com sales Email ServiceNSUK oxinst com service and support Web www oxford instruments com Americas OINS 300 Baker Avenue Suite 150 Concord MA 01742 USA Tel 1 800 447 4717 sales Tel 1 800 447 4717 support Fax 1 978 369 8287 sales and support ...

Страница 11: ...Microstat He Manual Next Safety Information 2017 Oxford Instruments Nanoscience MAN MHE 1 1 0 28ff3d8 Sep 2017 6 ...

Страница 12: ...specification design or conditions of supply of any of its products or services Although every effort has been made to ensure that the information in this document and all accompanying documents is accurate and up to date errors may occur Oxford Instruments shall have no liability arising from the use of or reliance by any party on the contents of this these documents including this document and t...

Страница 13: ...e to the equipment The action is explained in the text 3 4 Specific hazards Your system manual will indicate which of the following specific hazards relate to your system Refer to Safety Matters for more information in each case 3 5 Electrical hazards Contact with hazardous voltage can cause death severe injury or burns Ensure that a local electrical earth ground connection is available at the ins...

Страница 14: ... safety equipment must be made available to all personnel expected to handle cryogenic liquids including hand and eye protection 3 8 Pressure relief Closed vessels in the system are protected by pressure relief valves that exhaust directly to atmosphere unless otherwise stated Do not tamper with any of the pressure relief devices fitted to the system or attempt to modify or remove them Also ensure...

Страница 15: ...cemakers Where necessary the appropriate warning signs should be in place around the installation site Personnel who have a cardiac pacemaker must not approach the system at any time even when it is powered off The magnet can exert a force on nearby ferromagnetic objects which presents a hazard to personnel if these objects are free to move 3 11 Asphyxiation Helium and nitrogen can displace the ox...

Страница 16: ...eas 3 13 Safety equipment The following items are recommended for safe operation of any system Personal protective equipment including thermally insulated gloves face protection and protective footwear Hazard warning signs barriers or controlled entry systems to ensure that personnel approaching the system are aware of the potential hazards This precaution is especially important if you system inc...

Страница 17: ...tat Optistat CF V cryostat 4 1 The Cryostats Both the MicrostatHe and MicrostatHe R are continuous flow cryostats designed principally to allow a sample to be cooled to a low temperature and studied with an optical microscope The window arrangement for the standard MicrostatHe allows the sample to be brought close to the objective lens of a microscope The MicrostatHe R has a rectangular shaped tai...

Страница 18: ...hields are thermally insulated from the room temperature surroundings by the outer vacuum chamber OVC This space is pumped to a high vacuum before the cryostat is cooled down but it is protected against accidental build up of high pressures by a pressure relief valve Up to two windows can be fitted to the MicrostatHe Each window is permanently bonded into the OVC flange which is shaped to allow th...

Страница 19: ...Microstat He Manual Figure 4 3 Microstat He R schematic 2017 Oxford Instruments Nanoscience MAN MHE 1 1 0 28ff3d8 Sep 2017 14 ...

Страница 20: ...the EPS40 rotary pump 4 3 The cryogen transfer siphon The LLT transfer siphon is designed for ultra low loss performance The cold exhaust gas from the cryostat flows along the tube and the enthalpy of the gas is used to shield the flow of liquid from the room temperature surroundings The LLT 600 and 700 are used for manual control and the LLT 650 and 750 are automated versions which allow the gas ...

Страница 21: ...rogen storage dewar Cryogen transfer tube LLT with suitable storage dewar adapter Polythene tube 10mm outer dia for the gas exhaust Oil free diaphragm pump GF4 or EPS40 rotary pump for low temperature operation High vacuum pumping system to evacuate the OVC occasionally Temperature controller Mercury iTC Sensor heater cable CQB0090 Gas flow controller VC U and pumping lines Motor controlled needle...

Страница 22: ...em to pump water vapour If the system is badly contami nated with water vapour the gas ballast facility on the rotary pump should be used 5 4 Evacuating the transfer tube The transfer tube vacuum space has a separate vacuum valve similar to that on the cryostat and the high vacuum pumping system can be connected to it directly The transfer tube vacuum space has a separate evacuation valve similar ...

Страница 23: ...ow Figure 5 1 Mercury home screen The Mercury iTC temperature controller should be connected to the cryostat as follows The sensor heater cable CQB0090 is connected between the ten pin seal on the cryostat and the Sensor Heater socket on the temperature controller If your transfer tube has an automatic needle valve connect the needle valve cable CWA0112 between the seven pin seal on the transfer t...

Страница 24: ...ller made by another manufacturer you should take the same precautions The recommended values for the Heater Voltage Limit and the Temperature Limit are given with the test results for the cryostat If you do not safeguard the system it is possible to cause serious damage Next System Operation 2017 Oxford Instruments Nanoscience MAN MHE 1 1 0 28ff3d8 Sep 2017 19 ...

Страница 25: ...plug in the transfer siphon entry fitting Slowly lower the dewar leg of the siphon into the dewar engaging the nut on the syphon with the dewar fitting Switch on the GF4 pump Some liquid will be used to cool the leg and the dewar exhaust must be open to allow the boil off to escape If you try to cool the leg too quickly a large amount of liquid will be wasted and there is a risk of being burnt by ...

Страница 26: ...needle valve on the transfer tube The temperature will probably fall immediately as Helium in the heat exchanger is being boiled off After a few minutes the liquid will have boiled away and the temperature will start to rise At this point open the needle valve about a quarter turn The temperature should stabilise below about 20K point C Now open the needle valve in very small increments waiting fo...

Страница 27: ... display a screen similar to the following This screen shows that a standard PID table in this case Microstat He Mercury pid is already loaded into the iTC Tap Load to view alternative PID tables These may be from the factory or created by the user Tap a filename to select it and then tap Load to load the selected PID table The PID values given in the test results for the system are suitable to gi...

Страница 28: ...Microstat He Manual Figure 6 3 Mercury PID table Figure 6 4 List of PID tables 2017 Oxford Instruments Nanoscience MAN MHE 1 1 0 28ff3d8 Sep 2017 23 ...

Страница 29: ...bove room temperature check that your system is suitable for this temperature range The siphon must be removed Pump the OVC continuously to maintain the required high vacuum You can now control the system at a set temperature as described above exceeding 300K 6 7 Warming up the system Switch off the gas flow pump After a few seconds the pressure in the Helium flow circuit will rise to approximatel...

Страница 30: ...d during adjustment 6 9 Operating with liquid Nitrogen The cryostat can also be operated with liquid Nitrogen instead of Helium The basic operating procedure is the same but there are a few differences 1 Ensure that the flow gauge calibrated for air is used on the VCU 2 The viscosity of liquid Nitrogen is greater than that of Helium so the flow rate through the cryostat is lower This increases the...

Страница 31: ... the flow rate may change too rapidly and good stability may not be achieved 9 The PID settings on the temperature controller may be different from those given in the test results Typically the P and I values should be increased slightly Next Service and Maintenance 2017 Oxford Instruments Nanoscience MAN MHE 1 1 0 28ff3d8 Sep 2017 26 ...

Страница 32: ... is fixed to the microscope stage then it is not necessary to remove it Release the NW4O clamp around the neck of the cryostat and withdraw the cooling unit from the OVC This gives access to the radiation shield which is removed by loosening the four screws and pulling the shield The holes in the shield have been slotted so the retaining screws do not need to be removed The sample holder cold fing...

Страница 33: ...or if one is available Note however some window materials for example polythene mylar and aluminised mylar are porous to Helium gas at room temperature and cannot be leak tested in this way 7 3 2 Radiation shield windows The radiation shield windows are held in place by wire clips as shown below Carefully prise the clip out of the window frame and turn the cryostat over to let the window drop out ...

Страница 34: ...Microstat He Manual Figure 7 1 Changing outer windows 2017 Oxford Instruments Nanoscience MAN MHE 1 1 0 28ff3d8 Sep 2017 29 ...

Страница 35: ...Microstat He Manual Figure 7 2 Changing radiation shield windows 2017 Oxford Instruments Nanoscience MAN MHE 1 1 0 28ff3d8 Sep 2017 30 ...

Страница 36: ...2 Operating Cycle System Cooldown Specification Room Temperature to base approx 10 minutes with pre cooled transfer siphon 8 3 Physical Parameter Nominal Value Cryostat Weight kg 1 8 8 4 Electrical Power Single Phase 1PWR U All single phase powered units supplied with the system can be used worldwide without the need for configuration The maximum power consumption of each unit in this application ...

Страница 37: ...mperature may be reduced by using a rotary pump such as the EPS40 Please enquire for further details 8 6 Further Information Test Specifications Microstat Optistat Index 2017 Oxford Instruments Nanoscience MAN MHE 1 1 0 28ff3d8 Sep 2017 32 ...

Страница 38: ... A Heat exchanger heater B Heat exchanger heater C Heat exchanger sensor V D Heat exchanger sensor V E Heat exchanger sensor I F Heat exchanger sensor I H Spare J Spare K Spare L Spare 9 1 1 Checking the wiring A resistance meter can be used to check the wiring of the cryostat the following readings should be expected across pins Pins Nominal resistance A B 40 Ω approx C D 30 Ω approx C E 15 Ω C F...

Страница 39: ...check the top plate seals and outer window seals If there is no leak there may be too much moisture in the OVC and it should be pumped with a rotary pump with the gas ballast valve open Cryostat will not cool down Check whether there is any flow of gas through the system using the gauge on the VC U if applicable Poor temperature stability Check that the PID settings on the temperature controller a...

Страница 40: ...k that the PTFE seal has not been damaged Check the connections to the thermometer and make sure that it is working properly and in good thermal contact with the cryogen flow Check that you have not added too much heavy wiring to the sample holder introducing a high heat load Check the quality of the vacuum in the OVC and in the transfer siphon Check the cryostat for mechanical damage Warm it to r...

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