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31/07/14
Sample Environment Programme
for the ISIS Neutron Facility
Sample Environment Programme
George Carins, Maarten Verbraeken, Martin Jones, John Irvine
Overview
• Sample Environment Development Process
• Example Environment – In Situ Conductivity
• Example Experiment – Alkaline Earth
Hydrides
• Conclusions
31/07/14 Sample Environment Programme
Sample Environment Development Process
31/07/14 Sample Environment Programme
1) Beam timeproposal –
viabilitydiscussions and
submission
2) Designconcepts – User
driven
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5) Final DesignFreeze –
Engineeringdrawings – ISIS
design team
4) Design review –User, ISIS design,
pressure, electrical,instrument teams
3) Draft Design– ISIS design
team
6) Procurementand
manufacture –ISIS designteam, User
31/07/14 Sample Environment Programme
7) Trial Build –Correctivechanges ifrequired
8) Offline Tests– Leak check,
sensors,interfaces, etc.
9) Safety ProofTests –
Pressure,Electrical
10) Commissioning– Temperature,
gases, Backgroundscan IN BEAM.
Corrective changesif required.
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11) Experiment
Example Environment – In Situ Conductivity
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• A proposal ‘In situ studies of conduction mechanisms and nitrogen
incorporation in alkaline earth deuterides’ awarded beam time
• Required an in situ conductivity environment
• Conceptual designs generated and iterated
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• Design review held with input from pressure, electrical and design
teams from ISIS
• Specific consideration given to required standards and interfaces
pO2 sensor
Conductivity contacts
Macor sample holder
Bolt-together assembly
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• Detailed design generated by ISIS design team and design frozen
• Engineering drawings generated
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• Parts procured and manufactured for 2 off assemblies
• Trial build plus leak test, sensor and interface check carried out
• He mass spec leak check: 2.0x10-9 mbar·l/s
• Pressure proof test of each assembly at 2.5 bara for 30 mins
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• Commissioning in POLARIS diffractometer
Stainless steel peaks
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With macor holder & screwsHolder removed
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With macor holder & screwsModified holder (no screws)
Example Experiment
- Alkaline Earth Hydrides
Experimental Aims:
• Synthesise BaD2 and CaD2 dense pellets
• Perform in situ H2/D2 exchange with neutron
diffraction with simultaneous conductivity measurement
– in POLARIS neutron diffractometer
02/06/14 Alkali Earth Metal Hydrides
Alkaline Earth Hydride Structures
• BaH2, SrH2 and CaH2 – same orthorhombic structure at RT
• Orthorhombic PbCl2 structure – Pnma space group
• All deuteride analogues – same structure
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• Ionic crystals
• Intrinsic H vacancies• 2.5% - 8%
• Suggests electronic defects
Experimental Set Up
• Dense pellets painted with Pd electrodes
• Pellets held in closed end quartz tube
• Au contacts clamped to pellets
• Vials suspended in vacuum furnace
• Furnace mounted in POLARIS diffractometer
02/06/14 Alkali Earth Metal Hydrides
• POLARIS - 6 detector banks –
differing resolutions and length scales
• Problems with hydrogen nuclei -
incoherent scattering
BaD2 to BaH2
31/07/14 Sample Environment Programme
31/07/14 Sample Environment Programme
Conclusions
• Simple development path for new sample environments
– Very supportive ISIS engineering team
• ISIS/St Andrews collaborated to develop an effective in situ
conductivity/temperature/atmosphere environment
• Money is available for new sample environments
– Contact Martin Jones ([email protected])
Any Questions?
Acknowledgements
Ron Smith, Colin Offer, Richard Haynes, Chris Goodway - ISIS
Lewis Downie, Zac Dehaney-Steven, Berceste Beyribey
EPSRC
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