Transcript Making Money by Cooling Crystals .

Making Money by Cooling
Crystals
Mike Glazer, Physics Department, University of Oxford & Oxford
Cryosystems Ltd.
Why do Crystallographers want to cool
crystals?
 To slow down the motion of atoms in order to give
sharper, higher-resolution diffraction patterns
 To study phase transformations
 To preserve delicate crystals in an x-ray beam by
limiting radiation damage
 Recommended by the International Union of
Crystallography Journals Commission
Ratio of
TDS to
intensity
Why is it difficult to do?
 X-rays used in diffraction studies are
relatively soft and so tend to be absorbed
by windows
 Even with suitable windows, sealing a tiny
crystal (say 0.1mm across) in a chamber
and then centring and orientating is not
trivial
 Windowless cooling has been difficult to
achieve with precision because of air
currents, icing and poor control of cooling
medium
An early attempt
Gas delivery system
Basic Sealed Dewar System
heater
•When liquid nitrogen needs
replenishing, Dewar seal must be
thermocouple
broken
•Highly unstable in temperature by as
much as 50K
•Lowest temperature around 120K
•Non-laminar flow
heater
•Most commercial systems made of
glassware, bulky, difficult to control,
wasteful of liquid nitrogen
•Uses huge amount of liquid nitrogen
•Often necessary to put plastic bag
around apparatus to inhibit icing
J. Opt. Soc. Am. (1922). 6, 906 P.P. Cioffi & L.S. Taylor
Acta Cryst. (1967). 22, 695 M. Renaud & R. Fourme
Down to 90K; 1.4 litres per hour
Commercial Systems
Syntex
Siemens-Nicolet
Acta Cryst. (1955). 8, 348 A. Kreuger
123 to 573K Eventually marketed by Enraf-Nonius
and became the most widely used system
J. Appl. Cryst. (1981). 14, 43-50 S.-H. Hong & S. Asbrink
83 to 1120K, stability
0.25K below room
temperature, 1K
above; 1.2 litres per
hour
J. Appl. Cryst. (1985). 18, 528-532
J. Hajdu, P. J. McLaughlin, J. R. Helliwell, J. Sheldon & A. W. Thompson
80 to 290K; 1.5 to
2 litres per hour
J. Appl. Cryst. (1982). 15, 227-231 H. D. Bartunik & P. Schubert
100 to 323K,
stability 0.5K
J. Appl. Cryst. (1972). 5, 102 J. O. Thomas
And now a couple of monsters
J. Appl. Cryst. (1980). 13, 425-432 S. Samson, E. Goldisht & C. J. Dick
18 – 300K
J. Appl. Cryst. (1969). 2, 109 R. Rudman & J.B. Godel
88 to 323K,
stability 1K
The Cryostream
Published but not patented!!!
Principle of Cryostream
77K
RT
77K
0.6 litres/hour consumption
77 –
350K
The Prototype
“It’s very nice, but I don’t think there is any money in it”
– Head of Department
Overview of Oxford Cryosystems
 Founded at Oxford University (Clarendon
Laboratory) in 1985
 Head office based just outside Oxford plus
an office in Devens, Massachusetts
 Concentrates solely on design and
manufacture of low temperature devices
for Crystallography
Oxford Cryosystems’ Products
 Nitrogen Gas Cryostream Cooler
 Open flow nitrogen system for freezing crystals to 80400K
 Cryostream Plus
 Similar with Cryostream with extended temperature range
up to 500K
 Cobra
 Non liquid cryogen equivalent of the Cryostream
 N-HeliX
 Open flow helium/nitrogen gas cooler with a temperature
range of 28- 300 K.
 PheniX
 Cryostat for cooling flat plate powder samples enclosed in
a vacuum to 11K
 Desk-top Cooler
 Non liquid cooler for moderately low temperatures
Overview of Cryostream
 Liquid-nitrogen based
system
 Uses LN2 from Dewar
vessel as source of cold
 Refillable with no effect on
temperature
 Temperature range of 80400 K or 80-500 K for Plus
system
 Stability of 0.1 K
 Control and monitoring via
Cryopad software and
Cryostream controller
 Over 1400 systems
worldwide
Advantages of Cryostream
 Low initial cost of ownership
 Less mechanical components meaning:
Simple (user) maintenance
Low service costs
Less noise
Very basic pre-installation service
requirements
Cryostream Benefits
 The highest specifications :
 Temperature range of 80-400 K or 80-500 K
 Temperature stability of 0.1 K
 The most economic and efficient system available:
 Liquid consumption of just 0.6 l/hour
 Half that of competitive systems
 OC superior gas delivery nozzle design means:
 Better laminar flow so…
 Vastly reduced risk of icing
 Temperature mapped to crystal position
Typical Cryostream Configuration
600 Series Cryostream
700 Series Cryostream Plus
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The Birth of “Cryocrystallography”
There were several earlier attempts at this but this was
the first paper to overcome technical difficulties
“Cryocrystallography” Publications
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Note: begins 3 years after start of Oxford Cryosystems
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Customer’s comments
I have bought three of these over the past decade or so and as you would
expect I am very satisfied with the performance. Having used earlier LT
systems from other manufacturers, the Cryostream was a whole new world no icing, runs for months continuously, highly stable and the low
consumption of LN2 (~ 15 litres/day) means low running costs.
I have run it at 80K without problems and for longer periods at 100K.
However, most of our datasets have been collected at 150K.
Stability was a major factor because I needed to be able to grow crystals
from liquid samples sealed in capillary tubes - impossible on older
systems but quite feasible using a Cryostream.
We at Brookhaven have finally joined the modern world with the purchase
of an Oxford Cryostream system to immortalize our protein crystals in
the X-ray beam.
Non-liquid system
 Uses a mechanical cooler at the source of
refrigeration rather than liquid cryogen
Most common technique - Stirling Cooler
The Stirling cycle involves the expansion of
a volume of high pressure gas
The helium gas is not consumed by the
system
Common Stirling Coolers include GiffordMcMahon or Pulse Tube
Transfer gas used - nitrogen or air
Gifford McMahon Cooling
Stirling Cycle
Phase 1:
Virtually all the gas is in the compression space at ambient
temperature and the displacer is in the tip of the cold finger. In
this phase the pistons are driven inwards, compressing the gas.
This process is nearly isothermal, the heat output Qc being
dissipated via heat sinks around the compressor and the base of
the cold finger.
Phase 2:
The pistons have reached the end of the compression stroke, the
gas in the compression space is at ambient temperature and the
displacer has not yet moved. This is the situation at the start of
Phase II. Throughout this phase the pistons remain stationary and
hence the total volume of gas remains constant. The displacer
moves downwards as its spring compresses and gas flows through
the regenerator, giving up heat Qr in the process. This heat is
stored in the regenerator until later in the cycle.
Phase 3:
The pistons are driven outwards and the gas expands. This
expansion process, too, is nearly isothermal, the heat input Qe
being drawn from the surroundings of the expansion space. As a
result refrigeration occurs at the tip of the cold finger.
Phase 4:
Throughout this phase the pistons remain stationary. The
displacer, however, moves upwards because of the lower gas
pressure in the expansion space. Gas from the expansion space
therefore flows back through the regenerator, taking up the stored
heat Qr in the process and re-entering the compression space at
ambient temperature.
Typical Cobra Configuration
Overview of Cobra
 Nitrogen gas based
system
 Uses GM refrigerator
as source of cold
 Temperature range of
80-400 K or 80-500 K
for Plus system
 Stability of 0.1 K
 Control and monitoring
via Cryopad software
and Cryostream
controller
Advantages of Cobra
 No LN2 therefore no issues with:
Safety
Ventilation
Logistics of moving Dewars
Storage of LN2
 Can be left running for weeks or months
without user intervention
Cobra Benefits
 The highest specifications :
 Temperature range of 80-400 K or 80-500 K
 Temperature stability of 0.1 K
 OC superior gas delivery nozzle design means:
 Better laminar flow so…
 Vastly reduced risk of icing
 Temperature mapped to crystal position
 OC Cobra-specific control software:
 Enables full monitoring & control of system
Brief Comparison of Cryostream & Cobra
Cryostream
Low initial purchase cost of system

Minimal service costs or user can
perform servicing

Cobra
Ability to run for weeks/months without
user attention (i.e. Dewar refilling)

Avoidance of liquid nitrogen safety
issues

Temp range 80-400 K (or 500 K for
Plus version)


Stability of 0.1K


Remote control and monitoring via
Cryopad software


Further Comparison
Cryostream
Mechanical components (i.e. service •Pump
& noise)
•Dry Air Unit
Cobra
•
Cryodrive
•
Refrigerator
•
Dewar
(N generator)
•Cryodrive
•
Pump
•
(N generator)
•
Change diaphragm
•
Pump vacuum
•
Pump vacuum
•
Recharge helium
•
Line driers
•
•
Service dry air unit
Required OC service
•
Rare- 5 years +
•
Cost of OC service
•
< £1000
•
•
Contributing to footprint
User servicing
Replace N generator
filters
Regular- every 18-30
months
£3000- £5000
Temperature profile for Cryostream and
Cobra
Competitive LT System at 5 l/min
Distance from End of Nozzle v. Gas Temperature at a Set Point of 100K
Competitive LT System at 10 l/min
700 Series Cryostream at 5 l/min
700 Series Cryostream at 10 l/min
105
Temperature (K)
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Distance from Nozzle (mm)
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18
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N-HeliX
 Open flow helium
cryostat
 Uses helium gas,
NOT liquid
 Temperature range of
28- 300 Kelvin
 Stability of 0.3 Kelvin
 Can be used with both
nitrogen and helium
gas
N-HeliX
 Dual flow controller
allows mid-flow
change between
helium and nitrogen
 Can be used with
either gas alone
 Much cheaper and
safer than using liquid
helium
PheniX
 Closed cycle cryostat
used for flat plate
powder samples
 12K without liquid
helium
 Stability of 0.1K
 Fast cool-down to 20K
in 30 mins
 Fast warm-up to RT in
40 mins, hence fast
sample change
PheniX
 Unique rotating seal
allows tilting of
sample stage without
movement of whole
system
 Sample holders
available in variety of
materials-screw into
place in seconds
 Mylar radiation shield
 Easily removable lid
with Carbon fibre
windows
Desktop Cooler
170-290K,
stability 1K