Fifth International Workshop on Sample Environment at Neutron Scattering Facilities
Here is the list of poster contributions that have been presented during the workshop. For each contribution, you will find the list of authors, their affiliations and emails and the corresponding abstract. You can also download a PDF version of the poster by clicking on the vignette.
Wet or Dry….That is the question
R. Down - ISIS Rutherford Appleton Labs (Didcot, United Kingdom)
Over the years we have all been exposed to the gas companies continuously warning us of price increases within the Helium market, unusually for once in recent months we have seen some evidence of a rise in helium costs; and the prediction is that Helium costs will continue to rise…….. Could this for once be true?
There has been a steady increase in the amount of dry cryogenic systems available on the market and most facilities will have responded with the odd investment here and there; suddenly at ISIS the odd investment has now grown and there are a considerable number of Neutron and Muon instruments that are using or planning to use dry systems.
We will take a look at what dry systems ISIS has and how the face of our cryogenic support and equipment base is changing; what range of temperature we can offer and what ancillary equipment we can supply to ensure that our dry systems are indeed as good as the wet systems that they replace.
Low Temperature Remote Pressure Measurement in Sapphire Anvil and other Cells
B. Evans, J. Dreyer, C. Bull - ISIS Rutherford Appleton Labs (Didcot, United Kingdom)
This poster will describe the ongoing development of a system for low temperature pressure measurements on clamp cells with optical access. The system makes use of ruby fluorescence, the principle of which is based on the shift in wavelength of laser light as it is absorbed and re-emitted by a fragment of ruby under pressure.
At ISIS we have had the capacity for bench-top pressure measurements in sapphire anvil and Paris-Edinburgh cells for some time. We have now made successful remote measurements on a sapphire anvil cell at low temperatures using an adapted EasyLab Optiprexx ruby fluorescence system and a fibre optic assembly. This system has also been used to make remote pressure measurements on a Paris-Edinburgh cell with diamond anvils.
A new development to provide hydraulically driven high-pressure cells with optical access for pressures ≥10 GPa with in-situ ruby fluorescence measurements at low temperatures will also be described.
A Compact System for the Production and Quality Measurement of Para-Hydrogen
B. Evans, C. Goodway, J. Bones, A. Ramirez-Cuesta - ISIS Rutherford Appleton Labs (Didcot, United Kingdom)
Normal hydrogen gas contains 25% para-hydrogen and 75% ortho-hydrogen, but may be converted to a maximum possible 99.8% para-hydrogen at low temperatures. The percentage of para-hydrogen in a gas sample can be verified by neutron transmission methods during experiments, but it is usually preferable to know the para-hydrogen percentage of the gas before adding it to a sample on the beam line.
The ISIS para-hydrogen production rig contains a 10 K cold head assembly, a pumping set, a gas handling system, a para-hydrogen generating cell and a temperature control system. A gauge for measuring the percentage of para-hydrogen is incorporated into the assembly with supporting electronics. The principle of operation of the gauge is based on conductivity measurements.
This poster will describe the design and testing of the para-hydrogen rig and gauge.
Variable Temperature Insert for Paris Edinburgh Cell
D. Francis¹, W. G.Marshall¹, M. G.Tucker¹, J. W Dreyer¹ and G. Kouzmenko² - ISIS Rutherford Appleton Labs¹ (Didcot, UK), Oxford Instruments NanoScience² (Abingdon, UK)
A prototype variable temperature (v-T) insert for the Paris-Edinburgh (P-E) press has been designed and developed at ISIS which is capable of varying the sample temperature over the 110 – 500 K interval with excellent control characteristics. The insert utilises a liquid nitrogen cooling circuit to cool just the sample and the WC anvils, with the latter incorporating the resistive heaters used for temperature control and heating.
The insert assembly is thermally insulated from the P-E cell body by zirconia-cored seats and backing disks and PTFE insulation. The temperature of the P-E cell cylinder housing is maintained close to ambient temperature by means of a separate constant-temperature circuit. The whole installation in mounted on a standard Tomkinson flange and runs in a standard ISIS instrument vacuum tank. The sample temperature and pressure can be monitored and controlled remotely from the ISIS instrument computer used for neutron data acquisition.
Cool-down times of the previous low-temperature setup – which required cooling the entire P-E press using liquid nitrogen inside a large vacuum-walled tank – were typically 4-5 hours from ambient to 120 K. Recent commissioning tests of the v-T insert demonstrated the ability to cool the sample to 100 K and warm to 473 K from ambient temperature within ~45 minutes. In addition to a more efficient and productive use of neutron beamtime, this insert now makes possible high-pressure neutron diffraction experiments over the 100-500 K and 0-10 GPa intervals with a single P-E cell sample loading, an entirely new capability.
New Developments on Orange Cryostats
S. Gerischer - Hahn Meitner Institut (Berlin, Germany)
In the last years two major improvements have been made on our standard Orange cryostats. The first concerns the sample space and the cool down time. We replaced the 50mm diameter lower part of the sample space by a bottle shape 68mm can. This will reduce the aluminium background scattering especially for the neutron instruments with radial collimators. In addition we removed some useless masses which interrupt the cool down at 20K for half an hour.
The second is a cheaper and better needle valve controller. The new controller contains a small LCD display and an Atmel micro-controller. Compared to the current design the electromagnetic noise caused by the driving of the stepper motor is strongly reduced. It uses a simple two-level controller and will shut down the driving current when the motor is not moving. The open design allows us to connect an absolute position encoder if it is needed to monitor the absolute movement. It will even be possible to use this controller as an independently running Lambda controller und needle valve controller on the Oxford Instruments Magnets.
A new pressure gauge even allows us to regulate the needle valve below 1 mbar. Thus the base temperature of the Orange cryostat can be lowered to 1.3K with the help of a roots pump.
Micro-Furnace for Transmission X-Ray Diffraction Imaging
B. Gorges - European Synchrotron Radiation Facility (Grenoble, France)
A new transmission furnace has been developed to work under gas flow up to 800ºC. Most X-ray furnaces offering wide angle access work in reflection mode; X-ray topography measurements have to be done in transmission mode but still necessitate a wide angle. The reflection setup also gives a larger distance between the sample and the detector. This transmission furnace had to comply with a number of additional constraints: thermalisation of a low thermal conducting crystal sample, stressless sample mounting and small temperature gradients over a 7x7mm2 vertical sample surface. The construction also had to take the possibility of chemical reactions at high temperature between the sample, the construction materials and the gas into account.
The validation of the new setup has been done on ESRF beamline BM05 through the characterization of the ferro-electric phase transition of BaTiO3.
A.S. Scientific Products Limited
C. Hiller, P. Wiggins - (Abingdon, United Kingdom)
A S Scientific Products design and build sample environment apparatus. Under licence from the ILL, we build the ‘famous’ Orange Cryostat and the High Temperature Furnace (up to 1800°C).
A large part of our sample environment business now involves the use of mechanical cold heads. We have OEM relationships with all the major manufacturers (Sumitomo (SHI) Cryogenics, Leybold, Cryomech, Edwards). This allows us to make a number of different Top Loading Cryostats with either Pulse Tube or GM machines. We also manufacture a 1.8K cryogen free unit utilising a standard 10K GM machine.
A S Scientific Products can supply all the usual accessories needed to build a complete system including:
- Temperature controllers,
- LHe and LN2 transfer lines,
- Bespoke tail sets with vanadium, sapphire windows,
- Vacuum pumps.
We can also design and build Bath Cryostats, Flow Cryostats, and 1 off style cryogenic apparatus.
Progress and Future Developments involving High Pressure Hydrogen at ISIS
M. Kibble - ISIS Rutherford Appleton Labs (Didcot, United Kingdom)
Within the Experimental Operations Division of ISIS, the Furnace, Pressure & Special Systems Section are developing their range of Sample Environment Equipment to meet the ever advancing demands of the visiting scientists and scientific community.
Scientific interest is progressively demanding further advancements of our equipment to enable the development of scientific information and knowledge and this includes the requirement of ever increasing pressures. With interest growing in areas such as fuel replacement, Hydrogen storage has become the hot topic. At present ISIS can support experiments involving Hydrogen of pressure ranges of up to 3kbar within a temperature range of 10 to 773 Kelvin.
The Furnace, Pressure & Special Systems Section are currently progressing and developing equipment with the aim to provide an experimental environment achievable of providing pressures of up to 8kBar with a Hydrogen pressure medium within neutron and Hydrogen compatible materials. To enable us to meet these parameters the section needs to source companies who will develop equipment in collaboration with ISIS. This has been our initial aim and at present we have been able to compile a portfolio of companies willing to develop and modify existing inert gas systems with the aim to produce a system that is manufactured from Hydrogen safe materials.
Our resent purchases include a 7kbar Hand Intensifier, 10kbar Transducers and 10kbar rupture disc assembly, all of which are Hydrogen friendly.
The Laboratory for Magnetic Measurements at BENSC
K. Kiefer - Hahn Meitner Institut (Berlin, Germany)
Since recent years, the Hahn-Meitner-Institute operates a variety of research laboratories for sample characterisation. In order to install a service for BENSC users providing access to complementary measurements at extreme conditions, these laboratories have been combined to form the new Laboratory for Magnetic Measurements at BENSC (LaMMB). At present, the possibilities of LaMMB offer four different measurement systems with magnetic fields up to 14.5 T and temperatures down to 260 mK. The services of LaMMB are strongly requested by internal as well as by external research groups.
Starting in 2008, a new cryogenic system with magnetic fields up to 17 T and temperatures down to below 10 mK will greatly extend the temperature and magnetic field range of the measurements at LaMMB.
In order to give an example for a successful measurement program the organic S=1/2 spin ladder material (C5H12N)2CuBr4 will be presented. The phase diagram of (C5H12N)2CuBr4 was determined by measurements of the specific heat, the magnetocaloric effect and the magnetization in magnetic fields up to 14.5 T and down to 300 mK.
Polarimetric Neutron Spin-Echo demonstrated
E. Lelièvre-Berna1, C. Pappas2, P. Bentley2, E. Bourgeat-Lami1, E. Moskvin2,3, M. Thomas1, S. Grigoriev3, V. Dyadkin3 - Institut Laue Langevin1 (Grenoble, France), Hahn-Meitner Institut2 (Berlin, Germany), PNPI3 (Gatchina, Russia)
The multifaceted dynamics of antiferromagnets and helimagnets require more than the conventional neutron spin echo set-up (NSE). Indeed, the neutron beam polarisation is not necessarily flipped upon scattering. When the magnetic interaction vector is complex. In the presence of nuclear-magnetic interferences the rotation of the incident polarisation can be of any angle around or toward a specific direction; it is impossible to distinguish between a simple depolarisation due to e.g. magnetic domains and a rotation of the polarisation vector.
One way of overcoming these difficulties is to implement a zero-field polarimeter [FT] on an NSE spectrometer [FM]. This has now been achieved using the 3rd generation Cryopad [ELB] and a modified version of the Intensity Modulated variant of NSE [BF]. To do so, two additional π/2 flippers were installed near the sample space. These flippers, combined with the other two π/2 flippers, define the Larmor precession regions before and after the sample position. A solid-state polariser was added after the first Larmor precession region to repolarise the beam. This is necessary for handling the polarisation vector in Cryopad. The last step involves the installation of the Cryopad cryostat with its two rotating nutators and the Orange cryostat used to cool the sample. We present the pioneering Polarimetric Spin-Echo experiment performed at HMI with the ILL Cryopad. This technique is now available on IN15 at ILL.
[FT]: F. Tasset, Physica B 157 (1989) 627
[FM]: F.Mezei, Z. Phys. 255 (1972) 146; F. Mezei (ed.), Neutron Spin Echo, Lecture Notes in Physics Series, Vol. 128 (Springer, Heidelberg, 1980)
[ELB]: E. Lelièvre-Bernaa, P.J. Brown, F. Tasset, K. Kakurai, M. Takeda, L.-P. Regnault, Physica B 397 (2007) 120–124
[BF]: B. Farago, F. Mezei, Physica B 136 (1986) 627
Compact 1100K Furnaces for Cradles & Automatic Power Racks for 1900K ILL-Designed Furnaces
P. Martin, F. Marchal, E. Lelièvre-Berna, X. Tonon - Institut Laue Langevin (Grenoble, France)
Single crystal diffractometers do need compact devices covering large temperature ranges and which can be mounted on a cradle. In order to satisfy our users, we have built a 1.8K cryogen-free cryostat and more recently a 1100K furnace. This furnace is very compact and compatible with the cold-head fixation. Its geometry is also compatible with the large solid-angle required on four-circle diffractometers. We present the performance of the furnace and show how easy it is to replace the heater.
We also present the new power racks that will be used to control our 1900K furnaces. They are fully automatised, much safer than the preceeding ones, and as fast as possible without destroying the equipment.
Management of Liquid Helium, Nitrogen and Argon at ILL
P. Mendes, N. Belkhier, E. Bourgeat-Lami, J.-P. Gonzales, Y. Memphis, E. Lelièvre-Berna, O. Losserand, X. Tonon, S. Turc - Institut Laue Langevin (Grenoble, France)
For many years, ILL sign contracts with CEA and CNRS for the delivery of liquid helium, liquid nitrogen and argon. Since the 80’s, a lot of efforts have been made to recover the helium gas with the aim to decrease the recurrent costs. Indeed, scientists and technicians use in average 500 liters of liquid helium per day while a kilogramme of gas, i.e. about 8 liters of liquid, cost more than 30€.
We present the organisation of the delivery, usage and recovery phases and explain how helium losses are minimised down to less than 20%. We also present the evolution of the usage of the cryogens and try to evaluate the future needs considering the arrival of cryogen-free and zero-boil-off systems.
How to Keep a Sample Stick out of Your Face
J. Scherschligt - NIST Center for Neutron Research (Gaithersburg, USA)
We have designed and tested a mechanism to improve the safety of top-loading closed-cycle refrigerators and liquid helium cryostats. Accidental introduction of air into the sample space can create a situation in which excessive pressure may build inside the sample space of the cryostat. Ice that forms near the top of the cryostat creates a blockage that prevents the relief valves typically located at the top of the cryostat from being able to function.
If the pressure rises high enough, the sample stick can be launched. In extreme cases, the body of the cryostat can be damaged or even explode. This presents a dangerous situation to the unsuspecting researcher, can result in the expensive loss of equipment, loss of beam time, and can damage the sample. We have devised a means of venting the bottom of the sample well through the sample stick itself. We present this mechanism and report on its tested performance.
CCR Helium Hose Swivels
L. Solomon - Oak Ridge National Laboratory (Oak Ridge, USA)
The SNS beamline 4a Magnetism Reflectometer has space constraints regarding a 4 Kelvin CCR and a concrete wall. The requirement is that the CCR rotates through 360 degrees horizontally about the cold finger axis as well as rotate through 90 degrees about a vertical axis to bring it out of the magnet coil for sample changes.
In order to maintain this movement, which sweeps the helium supply hoses past the wall, swivels were designed in house. This design allows the hoses freedom of motion without concern of kinking the hoses. Further development has yielded back-to-back swivel pairs which allow full freedom of movement for the CCR with no concern for flexure of the high-pressure helium hoses. The original pair of fittings has been in operation for 6 months now with no noticeable drop in system pressure. ORNL is currently investigating the option of patenting these fittings as no off-the shelf solutions to this need have been found.
High Pressure High Temperature (HPHT) Sapphire Cell
L. Walker - Oak Ridge national Lab. (Oak Ridge, USA)
Low temperature high pressure sample environment schemes are commonly used in twenty-first century neutron scattering experiments. The road less traveled, however, is high temperature high pressure sample environment schemes, especially on inelastic neutron scattering instruments. The challenge to address issues of material selection, cell and insert design, testing, and user approval coupled with the process of approving SNS’ first high pressure cell, bunker, and testing procedure were nothing short of ground breaking.