Oxford Instruments MicrostatN User manual

User Manual - Original Instructions
MicrostatN

EC Declaration of Conformity
This original Declaration of Conformity is suitable to Decision No 768/2008/EC of the European Parliament and of the Council of 9 July
2008 on a common framework for the marketing of products and contains the elements specified in the relevant modules set out in Annex
II of that Decision for the applicable Directives.
This declaration relates exclusively to the equipment in the state in which it was placed on the market, and excludes components which
are added and/or operations carried out subsequently by the final user.
Applied Council Directive(s):
The fulfillment of all the relevant provisions specified in the following Council Directive(s) have been demonstrated :
• 2014/30/EU Electromagnetic Compatibility (EMC)
• 2014/35/EU LOW VOLTAGE DIRECTIVE (LVD)
• 2011/65/EU RoHS Directive and Commission Delegated Directive (EU) 2015/863 (RoHS2)
We, The Manufacturer :
Oxford Instruments NanoScience, Tubney Woods, Abingdon, Oxon, OX13 5QX, United Kingdom, declare under our sole responsibility
that the following equipment :
MicrostatN
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 (Immunity)
–EN61000-3-2:2006 + A2:2009
–EN61000-3-3:2008
–EN55011:2009 + A1:2010 (Emissions)
• LVD
–IEC61010-1:2010 3rd Edition; This is harmonised with: ANSI/UL 61010-1:2012, CSA C22.2 No. 61010-1-12.
• RoHS2
–EN 50581:2012 Technical documentation for the assessment of electrical and electronic products with respect to the restriction
of hazardous substances.
The authorised compiler of the technical file is at Oxford Instruments NanoScience, Tubney Woods, Abingdon, Oxon, OX13 5QX, United
Kingdom.
We, the undersigned, hereby declare that the product(s) specified above conforms to the listed directive(s) and standard(s).
Name : Dr Michael N Cuthbert
Position : Technical Director
Date of issue : 21st December 2017
DOC-EC-MN-1.1.0 (28ff3d8) Dec 2017 1

Microstat N Safety and Support Information
IMPORTANT INFORMATION
Product description
The Microstat N is a continuous flow nitrogen cryostat, designed
principally to allow low temperature samples to be studied with an
optical microscope. The sample is mounted in vacuum on a heat
exchanger, with optical access available through up to two windows.
The sample temperature is held at temperatures betweeen 77K and
500K using the MercuryiTC temperature controller. Refer to the user
manual for more details. The user manual can be downloaded from
the website support.myoxinst.com.
Statement of intended use
The equipment has been designed to operate within the process pa-
rameter limits that are outlined in the user manual. The equipment
is intended to be installed, used and operated only for the purpose
for which the equipment was designed, and only in accordance with
the instructions given in the manual and other accompanying doc-
uments. 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 man-
ner. Consideration must be made for all aspects of the system’s
life-cycle including, handling, installation, normal operation, mainte-
nance, dismantling, decontamination and disposal. It is the user’s
responsibility to complete suitable risk assessments to determine
the magnitude of hazards.
The installation, use and operation of the equipment are subject to
laws in the jurisdictions in which the equipment is installed and in
use. Users must install, use and operate the equipment only in such
ways that do not conflict with said applicable laws and regulations. If
the equipment is not installed, used, maintained, refurbished, mod-
ified and upgraded as specified by the manufacturer, then the pro-
tection it provides could be impaired. Any resultant non-compliance
damage, or personal injury would be the fault of the owner or user.
Use of the equipment for purposes other than those intended and
expressly stated by Oxford Instruments NanoScience, 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
against the ingress of water. The equipment must be positioned so
that it will not be exposed to water contact. Ensure that pressure
relief devices are not obstructed.
Maintenance and adjustment
Only qualified and authorised persons should service or repair this
equipment. Under no circumstances should the user attempt to re-
pair this equipment while the electrical power supply is connected.
Health and safety information
The equipment operates at hazardous temperatures. Before work-
ing with the equipment, all personnel must read and become thor-
oughly familiar with the safety information given in the user manual.
In particular, users must read, understand and strictly observe all :
Warning notices; Caution notices; Safety labels and markings on the
equipment. For ease of reference and rapid response in an emer-
gency, it is advised that a copy of the user manual should be safely
kept near the equipment when in operation.
Before you attempt to install or operate this equipment for the
first time, please make sure that you are aware of the precau-
tions that you must take to ensure your own safety.
LOW TEMPERATURE EQUIPMENT: Danger of death or serious
injury. Contact with cold objects and cryogens can cause serious
injury. Use personal protective equipment including hand and eye
protection. Cryogens can displace the oxygen from air and cause
death by asphyxiation. Ensure that adequate ventilation is provided.
ÉQUIPEMENT A BASSE TEMPÉRATURE: Danger de mort ou de
blessure grave. Le contact avec des objets froids et des cryogènes
peut causer des blessures graves. Utilisez un équipement de pro-
tection individuelle, y compris la protection des mains et des yeux.
Les cryogènes peuvent déplacer l’oxygène de l’air et provoquer la
mort par asphyxie. Assurez-vous qu’une ventilation adéquate est
fournie.
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Microstat N Safety and Support Information
ELECTROSTATIC SENSITIVE EQUIPMENT: This equipment con-
tains electrostatic sensitive devices (ESD). Use approved ESD pro-
cedures when installing or maintaining this product.
ÉQUIPEMENT SENSIBLE AUX DÉCHARGES ÉLECTROSTA-
TIQUE : 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 use. EN61326-1:2013: EMC Immunity standard,
EN55011:2009+A1:2010 Emissions standard Electrical equipment
for measurement, control and laboratory use: EMC requirements.
Please refer to the user manual for more details.
Contact us at : Oxford Instruments NanoScience. See
www.oxford-instruments.com for details.
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Microstat N Manual
Oxford Instruments Nanoscience
Sep 2017

Microstat N Manual
Contents
1 MicrostatN - Principles of Operation 3
1.1 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Copyright . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Introduction 4
2.1 Documents supplied with the system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 Statement of intended use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.3 Restrictions on use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.4 Maintenance and adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.5 Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.6 Contact information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.7 Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3 Safety Information 7
3.1 Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2 Disposal and recycling instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3 General hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.4 Specific hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.5 Electrical hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.6 Protective earth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
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 cryostat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.2 Continuous flow cryostats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.3 The liquid Nitrogen transfer tube . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.4 The gas flow pump and flow controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5 Installation 15
5.1 Unpacking the system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.2 Preparing the system for operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.3 Evacuating the outer vacuum chamber (OVC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.4 Evacuating the Nitrogen transfer tube . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.5 Exhaust gas connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5.6 Loading the sample . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5.7 Electrical connections to the temperature controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
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Microstat N Manual
6 System Operation 19
6.1 Preparations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6.2 Cooling the system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6.3 Temperature control above base temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6.4 Controlling at a set temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
6.5 Warming up the system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
6.6 Changing samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
7 Service and Maintenance 24
7.1 Rubber O-rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
7.2 Removing the OVC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
8 Microstat N Specifications 25
8.1 Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
8.2 Operating Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
8.3 Sample Position Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
8.4 Physical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
8.5 Electrical Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
8.6 Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
8.7 Further Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
9 Appendices 27
9.1 Electrical connections on the cryostat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
9.2 Platinum resistance thermometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
9.3 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
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Microstat N Manual
1
MicrostatN - Principles of Operation
Continuous flow Nitrogen cryostat
1.1 Revision history
Always use the latest issue of the manual. Check for updates online at https://support.myoxinst.com.
1.2 Contents
• Introduction
• Safety Information
• System Description
• Installation
• System Operation
• Service and Maintenance
• Specifications
• Appendices
1.3 Copyright
Copyright 2017 Oxford Instruments Nanotechnology Tools Ltd, Tubney Woods, Abingdon, OX13 5QX, UK. All Rights Reserved.
Copyright in this document is owned by Oxford Instruments Nanotechnology Tools Ltd. Any person is hereby authorised to view, copy,
print and distribute this document subject to the following conditions: the document may be used for informational purposes only; the
document may be used for non-commercial purposes only; any copy of this document 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 indirect loss or damage of any kind, including loss of profit, revenue, goodwill
or anticipated savings. All such warranties are hereby excluded to the fullest extent permitted by law.
Oxford Instruments will not be responsible for the accuracy of the information contained in this document, which is used at your own risk
and should not be relied upon. The information could include technical inaccuracies or typographical errors. Changes are periodically
made to the information contained herein; these changes will be incorporated in new editions of the document.
•Next - Introduction
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Microstat N Manual
2
Introduction
This manual contains user and technical information for the MicrostatN system.
2.1 Documents supplied with the system
The following documents are supplied as electronic or paper copies:
• Operator’s manual (this document)
• Factory test results
• Mercury iTC manual
• Practical Cryogenics
• Safety Matters
• Mercury iTC temperature controller
• VC-U Gas controller.
This manual contains important information for the safe operation of your system. We recommend that you read this manual carefully
before operating the system for the first time.
Please keep all the manuals supplied with your system and make sure that you check for updated information and incorporate any
amendments. If you sell or give away the product to someone else, please give them the manuals too.
If you have bought a complete system from Oxford Instruments, separate manuals will have been supplied describing the other components.
Please ensure you have reviewed the information supplied in all of the manuals before you attempt to operate your system.
2.2 Statement of intended use
The equipment has been designed to operate within the process parameter limits that are outlined in the user manual. The equipment
is intended to be installed, used and operated only for the purpose for which the equipment was 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, installation, normal operation, maintenance,
dismantling, decontamination and disposal. It is the user’s responsibility to complete suitable risk assessments to determine the magnitude
of hazards.
The installation, use and operation of the equipment are subject to laws in the jurisdictions in which the equipment is installed and in use.
Users must install, use and operate the equipment only in such ways that do not conflict with said applicable laws and regulations. If the
equipment is not installed, used, maintained, refurbished, modified and upgraded as specified by the manufacturer, then the protection it
provides could be impaired. Any resultant non-compliance damage, or personal injury would be the fault of the owner or user.
Use of the equipment for purposes other than those intended and expressly stated by Oxford Instruments, as well as incorrect use or
operation of the equipment, may relieve Oxford Instruments or its agent of the responsibility for any resultant non-compliance damage or
injury. The system must only be used with all external covers fitted.
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Microstat N Manual
2.3 Restrictions on use
The equipment is not suitable for use in explosive, flammable or hazardous environments. The equipment does not provide protection
against the ingress of water. The equipment must be positioned so that it will not be exposed to water contact.
2.4 Maintenance and adjustment
Only qualified and authorised persons should service or repair this equipment. Under no circumstances should the user attempt to repair
this equipment while the electrical power supply is connected.
2.5 Support
If you have any questions, please contact us with the following details :
•System type :
•Serial number : the Sales Order (SO) number and/or other identifiers of your system.
•Installation/Shipment Address :
•Contact information : how we can contact you. email/telephone.
•Details of your query : The nature of your problem, part numbers of spares required, etc.
Please contact Oxford Instruments first before attempting to service, repair or return components.
2.6 Contact information
Europe, Middle East, Africa and India (EMEAI) OINS, Tubney Woods, Abingdon, Oxon, OX13 5QX, UK Tel: [phone]
(sales) Tel: [phone] (support) Fax: [phone] (sales and support) Email: [email protected] (sales) Email:
[email protected] (service and support) Web: www.oxford-instruments.com
Americas OINS, 300 Baker Avenue, Suite 150, Concord, MA 01742, USA Tel: [phone] (sales) Tel: [phone] (support)
Fax: [phone] (sales and support) Email: [email protected] (sales) Email: [email protected] (service and
support) Web: www.oxford-instruments.com
Asia OINS, Floor 1, Building 60, No.461, Hongcao Road, Shanghai, 200233, China Tel: [phone] (sales, service and support)
Email: [email protected] (sales) Email: [email protected] (service and support) Web: www.oxford-instruments.cn
Japan OINS, IS Building, 3-32-42, Higashi-Shinagawa, Shinagawa-ku, Tokyo, 140-0002, Japan Tel: [phone] (sales) Tel: +81
3 6732 8966 (support) Fax: [phone] (sales and support) Email: [email protected] (sales, service and support) Web:
www.oxford-instruments.jp
2.7 Acronyms
A number of acronyms may be used throughout this document. Please refer to the document Practical Cryogenics for a glossary of terms.
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Microstat N Manual
•Next - Safety Information
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Microstat N Manual
3
Safety Information
Before you attempt to install or operate your system, please make sure that you are aware of all safety precautions listed in this manual
together with the warnings and cautions set out in other documents supplied with the system.
All cryogenic systems are potentially hazardous and you must take precautions to ensure your own safety.
The general safety precautions required when working with cryogenic systems are given in the OINS’ document Safety Matters. We
recommend that all users should read this document, become thoroughly familiar with the safety information provided and be aware of
the potential hazards.
It is the responsibility of customers to ensure that the system is installed and operated in a safe manner. It is the responsibility of customers
to conduct suitable risk assessments to determine the nature and magnitude of hazards.
3.1 Disclaimer
Oxford Instruments assumes no liability for use of any document supplied with the system if any unauthorised changes to the content or
format have been made.
Oxford Instruments policy is one of continued improvement. The Company reserves the right to alter without notice the 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, to the fullest extent
permitted by law, excludes all liability for loss or damages howsoever caused.
Oxford Instruments cannot accept responsibility for damage to the system caused by failure to observe the correct procedures laid down
in this manual and the other manuals supplied with the system. The warranty may be affected if the system is misused, or the recommen-
dations in the manuals are not followed.
3.2 Disposal and recycling instructions
Before disposing of this equipment, it is important to check with the appropriate local organisations to obtain advice on local rules and
regulations about disposal and recycling.
You must contact Oxford Instruments (giving full product details) before any disposal begins.
3.3 General hazards
The following general hazards must be considered when planning the site for installation and operating the equipment. Please take notice
of the following relevant warnings.
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Microstat N Manual
3.3.1 Warning notices
Warning notices draw attention to hazards to health. Failures to obey a warning notice may result in exposure to the hazard and may
cause serious injury or death. A typical warning notice is shown below:
Warning: The warning triangle highlights dangers which may cause injury or, in extreme circumstances, death.
3.3.2 Caution notices
Caution notices draw attention to events or procedures that could cause damage to the equipment. Failure to obey a caution notice may
result in damage to the equipment. A typical caution notice is shown below:
Caution: The general caution symbol highlights actions that you must take to prevent damage 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 installation site.
Parts of the system carry high voltages that can cause death or serious injury. Ensure that a local electrical earth (ground) connection is
available.
The electrical supply to the system must include an isolation box to ensure that mains electrical power to the system can be isolated. The
isolation box must allow the supply to be locked OFF, but must NOT allow the supply to be locked ON.
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Microstat N Manual
3.6 Protective earth
The cryostat, electronics, pumps, and any other parts of the system fitted with earthing points must be connected
to protective earth at all times when the system is in operation.
3.7 Low temperature
Contact with cold objects and cryogens can cause serious injury to the skin. Skin may adhere to cold objects.
Ensure that any cryogenic or coolant delivery systems are designed to prevent contact with the cold components.
Consider the hazards of low temperatures when planning the installation of the system. Proper 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 that the outlets
of the relief devices are not obstructed. The correct operation of these relief valves is critical to the safety of the system.
3.9 Weight and lifting
Incorrectly lifting heavy objects can cause severe injury. Use the appropriate lifting equipment, operated by fully
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trained personnel, when handling heavy system components.
Appropriate lifting equipment and personal protective equipment (PPE) must be provided at the installation site for the duration of the
system installation.
3.10 Magnetic fields
Powerful magnetic fields can interfere with the operation of cardiac pacemakers. Do not approach the equipment if
you wear a cardiac pacemaker.
Systems with the magnet option contain powerful electromagnets. These electromagnets can produce a powerful magnetic field, which
can interfere with the operation of cardiac pacemakers in the vicinity of the system, causing death or serious injury.
Risk to personnel with cardiac pacemakers.
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 oxygen from air and cause death by asphyxiation. Ensure that adequate
ventilation is provided.
Areas where these chemicals are stored or used must be well ventilated to avoid the danger of suffocation. Oxygen level detection
equipment should be installed in suitable locations to warn personnel if the oxygen concentration falls below a threshold value. Take
precautions to prevent spillage of liquid cryogens.
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3.12 Fire
Atmospheric oxygen can condense on cryogenicaly-cooled objects. Oxygen can cause flammable substances to
ignite in the presence of heat or arcing, risking severe injury.
Rooms where cryogenic liquids are being handled must be designated as no smoking areas. While liquid helium and nitrogen do not sup-
port combustion, their low temperature can cause oxygen from the air to condense on surfaces and may increase the oxygen concentration
in these areas.
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 includes a superconducting magnet.
3.14 Maintenance
Observe the necessary maintenance schedule for the system. Consult Oxford Instruments if you are unsure about
the required procedures.
•Next - System Description
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4
System Description
4.1 The cryostat
The MicrostatN is a continuous flow cryostat designed principally for to allow a sample to be cooled to a low temperature and studied with
an optical microscope. The sample temperature is continuously variable between 77K and 500K. The special window arrangement allows
the sample to be brought close to the objective lens of the microscope. The cryostat may be operated in any orientation. The sample is
mounted in vacuum, and cooled by conduction.
Figure 4.1: Microstat N cryostat
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Microstat N Manual
Figure 4.2: Microstat N schematic
The sample is mounted in vacuum on a heat exchanger, and optical access to the sample is available through the windows. The sam-
ple space is thermally isolated from the room temperature surroundings by the outer vacuum chamber (OVC). This space is pumped
continuously with a two stage rotary pump whilst the cryostat is running.
Up to two windows can be fitted to the cryostat. Each window is permanently bonded into the OVC flange, which is designed to allow the
sample to be mounted as close as possible to the inside surface of the window.
This manual describes the operation of the system in conjunction with an Oxford Instruments Mercury iTC temperature controller. The
cryostat can be operated manually if a temperature controller is not available, although it may be difficult to obtain good temperature
control.
4.2 Continuous flow cryostats
Continuous flow cryostats do not have an internal reservoir to store a supply of cryogens. The liquid is supplied from a separate storage
vessel through a insulated transfer tube. It flows through a heat exchanger at the bottom of the sample space, through the sample space
and out of the cryostat to the pump. A thermometer and heater are mounted on the heat exchanger, and these can be used with a
temperature controller to balance the cooling power of the cryogen and to control the temperature of the gas before it reaches the sample
space.
4.3 The liquid Nitrogen transfer tube
A stainless steel, vacuum insulated transfer tube is provided with the system to transfer the liquid nitrogen from the storage vessel to
the cryostat. This tube has been made as light and as flexible as possible in order to limit the strain transferred to the cryostat and the
microscope stage.
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4.4 The gas flow pump and flow controller
The Oxford Instruments GF4 gas flow pump is used to promote the flow through the cryostat. It is an oil-free, twin-piston pump with a
nominal displacement of 42 litres per minute. The air leak rate is guaranteed to be less than 10cm3/min. This pump is described fully in a
separate manual.
The VC-U gas flow controller is used to control the flow of gas through the cryostat. It includes a flow meter (calibrated for Helium gas)
and a pressure gauge, so that the flow can be monitored.
•Next - Installation
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5
Installation
5.1 Unpacking the system
Carefully remove the cryostat and all the accessories from the packing case, and check the packing list to make sure that you have found
all of the components. Examine the system to make sure that it has not been damaged since it left the factory. If you find any signs of
damage please contact Oxford Instruments immediately.
To run this system you need the following components:
• The MicrostatN cryostat
• Liquid Nitrogen storage dewar
• Liquid Nitrogen transfer tube with suitable storage dewar adapter
• Polythene tube (7mm inner dia.) for the gas exhaust
• High vacuum pumping system to evacuate the OVC continuously
• Oil free diaphragm pump (GF4)
• Temperature controller (Mercury iTC)
• Sensor/heater cable CQB0090
• Gas flow controller (VC-U) and pumping lines
5.2 Preparing the system for operation
Choose a suitable position to operate the cryostat safely, and if necessary arrange for it to be supported so that it cannot accidentally fall.
The schematic below shows the cryogen and exhaust connections required for the operation of the system:
5.3 Evacuating the outer vacuum chamber (OVC)
The OVC has to be pumped continuously with a two-stage rotary pump to make sure that it gives the required thermal isolation. When the
system is new, all of the materials inside the vacuum space are likely to outgas quickly, and this will affect the quality of the vacuum. This
does not mean that the system is leaking, just that the new materials are being cleaned by the vacuum.
Connect the pumping system to the cryostat vacuum valve on the top plate of the cryostat. We recommend that you use a turbo-molecular
pump, backed by a rotary pump, and fitted with a cold trap which helps the system 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 Nitrogen transfer tube
Although sufficient thermal insulation can be achieved by pumping the transfer tube with a two stage rotary pump, performance will improve
significantly if it can be pumped overnight with a high vacuum pumping system. The transfer tube vacuum space has a separate evacuation
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