Fifth International Workshop on Sample Environment at Neutron Scattering Facilities
Here is the list of oral contributions that have been presented during the workshop. For each contribution, you will find the name of the author, his/her affiliation and email and the corresponding abstract. You can also download a PDF version of the viewgraphs by clicking on the vignette.
A Review on 20 Years of Sample Environment: Men and Machines - 1988 to 2008
M. Meißner - Hahn Meitner Institut (Berlin, Germany)
I will give a personal summary on the past two decades at BENSC where sample environment (SE) equipment has been developed for the new instruments at the refurbished 10-MW-reactor BER-II. The story begins with the early equipment at ILL and ISIS in the ‘80s of which BENSC benefited for a successful start in the early ‘90s. Later on, BENSC found its own field of expertise with the development of very low temperature devices which could be combined in a modular concept with various types of cryomagnets.
With the new millennium, the upgraded and new neutron scattering facilities provided financial budgets and man power resulting in new achievements in sample environment technology (i. e. cryogen-free, extreme high temperature and pressure). In addition, cooperation projects shared by various SE-teams and financed by international agencies will open new frontiers.
The increasing interaction among the SE community worldwide was triggered by the ENSA survey on instrumentation in 1995-1997 and initiated the first SE workshop in Berlin 1999. Now, facing the 5th workshop upcoming in Grenoble I am confident that sample environment equipment continues to be an essential and exciting part of neutron scattering instrumentation.
Sample Environment in ISIS Spallation Neutron Source
O. Kirichek - ISIS Rutherford Appleton Labs (Didcot, United Kingdom)
Sample environment equipment such as cryostats, pressure cells, furnaces, magnets, stress rigs etc are an essential to most neutron scattering experiments to induce the sample being studied into a phase or state of particular interest. We are going to give a brief overview of the new sample environment equipment available for neutron scattering experiments in ISIS which should considerably expand the range of physical parameters such as high pressure, high magnetic field and ultra low temperature.
The equipment includes new top loading cryogen free cryostat based on pulse tube refrigerator, powerful cryogen free dilution refrigerator produced by Verycold Oxford Instruments, three advanced superconducting magnets for pulsed neutron scattering at ISIS and a stress rig for measurements of bulk stress in engineering components at cryogenic temperatures. All systems mentioned above are expected to be either helium re-condensing or completely cryogen free. Here we are going to describe the design of these systems and discuss the results of prototypes testing.
Recent Sample Environment Innovations for SANS
S. Olsen, S.A. Pullen, E.P. Gilbert, F. Klose, M. Perry, J.C. Schulz & R.A. Robinson - Australian Nuclear Science & Technology Organisation (Sydney, Australia)
Over the last 18 months 2 new Sample Environments have been developed for use on the Quokka Small Angle Neutron Scattering machine. The first device is a joint development between ANSTO and New Zealand company HTS-110, a 5 Tesla Horizontal field Closed-Cycle High Temperature superconducting magnet, made of BSSCO 2223 material. This magnet mounts on tilt stages and has the sample mounted in a closed-cycle cryo-furnace. An electric field can be added to the sample whilst inside the magnet.
A device for rapidly heating and cooling samples, the RHQC, has been developed, and tested at IPNS. This device allows samples to be quenched at rates of up to 11K/sec and heated at 19K/sec in a temperature range of -120°C to 300°C. This device contains a cold cell and a hot cell and the sample is moved, pneumatically, between the cells. The device is mounted on a translation stage allowing either cell to be in the neutron beam. Multiple heating and cooling cycles can be run in the one experiment.
Sample Environment at FRM II
J. Peters - Forschungs-Neutronenquelle Heinz Maier-Leibnitz (Berlin, Germany)
Cryogen-free 7.5 T Magnet – Two Years of User Operation: In 2007 the FRM II Cryogen-free 7.5 T Magnet was operated on various instruments under user operating conditions. Different experimental setup for low temperature applications were field tested.
More over the talk addresses some new projects of sample environment equipment at FRM II. The FRM II Closed Cycle Cryostat with Ø50 mm sample tube has got a big brother. The new Ø80 mm sample tube allows increased sample sizes and minimized parasitic neutron reflections in e.g. case of powder diffractometers. For use at standard cold heads, we developed a heat switch based on a shape memory alloy. To intensify the high pressure activities at FRM II, a double action press (press capacity 450kN, tensile force 220kN) is available. The press allows static and dynamic applications up to 10 Hz by remote controlled servohydraulics. First design studies for high pressure cryostats and furnaces are in progress.
Sample Environment at the Swiss Spallation Source SINQ
M. Zolliker - Paul Scherrer Institut (Villigen, Switzerland)
The swiss spallation source SINQ is a continuous neutron source. As it has only a medium flux, its strengths lie both in sophisticated neutron instruments, and in the wide range of available sample environment equipment.
In addition to the standard equipment available at neutron scattering facilities, different combinations are offered to the experimentalists, some of them are unique. Dilution inserts allowing access to temperatures well below 100 mK may be used in the two high field magnets: the 15 Tesla vertical field cryomagnet for diffraction and spectroscopy and the 11 Tesla horizontal field cryomagnet for small angle scattering. In the latter case, the field may be perpendicular or parallel to the beam. MilliKelvin temperatures may also be combined with MuPAD, a device for neutron polarization measurements in 3 dimensions. High pressures up to 100 kbar may be performed down to 4 K, or 12 kbar down to 1.5 K. High temperature up to 1400 K may be performed in controlled atmosphere.
Experience with Cryofurnaces at Oak Ridge National Laboratory
L. Santodonato, J. Wenzel, and A. Church - Oak Ridge National Lab. (Oak Ridge, USA)
Cryofurnace here refers to any sample environment that operates from cryogenic temperatures to above 400 K. Four different types used at Oak Ridge National Laboratory are compared (hot stage Displex, hot exchange gas Displex, hot stick liquid helium, and hot exchange gas liquid helium).
The basic design of each cryofurnace is described, and performance data are presented. It is emphasized that none of them are fully optimized, especially the in-house designed hot exchange gas Displex. A process of continual testing and upgrading is essential to realizing the full potential of any of these devices. Specific tests and upgrades are described, including design modifications to enhance thermal contact and improve “cold valve” regulation. Upgrades in operating procedures and temperature control schemes are also described, which are especially relevant for off-the-shelf systems.
This leads to the question: does it make sense for a sample environment team to design its own cryofurnace (or sub-system) when off-the-shelf options are available? In-house design carries the risk of wasting time and money. But the team is sure to learn some valuable lessons, has a chance at advancing the state-of-the-art, and could save money in the long run.
Modernising the ILL Sample Environment Suite
E. Lelièvre-Berna, N. Belkhier, E. Bourgeat-Lami, J.-P. Gonzales, J.-L. Laborier, F. Marchal, P. Martin, Y. Memphis, P. Mendes, O. Losserand, C. Payre, X. Tonon, S. Turc - Institut Laue Langevin (Grenoble, France)
For about three years, we upgrade or renew the sample environment suite made available to +40 instruments within the framework of the ILL Millennium Programme. We report on the progress accomplished during these years by our rejuvenating staff.
Among the many tasks presented, we will see that the thermometers of about half of our cryostats have been replaced with Cernox sensors calibrated at ILL. We have built several compact cryogen-free cryostats for Eulerian cradles and two new dilution inserts, developed the cryofree Orange cryostat and new electronics for controlling the cryogenic devices. ILL have acquired a second 100kbar Paris-Edinburg cell and a Triton dilution refrigerator. We have ordered an asymmetric zero-boil-off 10T cryomagnet for three-axis spectrometers and some diffractometers. Three other cryomagnets are also being discussed for the reflectometers and the SANS and TOF spectrometers. A safer and very accurate 2kbar gas handling system for continuously loaded gas pressure cells is being designed in collaboration with the CNRS and six copies of a fully automatised and much safer power-rack for the 1900K ILL-designed furnaces are in production.
On the instruments side, we will soon start the installation of the new electronics that will be connected to the main control workstation using CORBA. A computer installed in the cabinet will ensure this link, record the data collected by the numerous controllers and program them from a shared database.
Self-Shielded Magnets for Neutron Scattering
A. Church - Spallation Neutron Source (Oak Ridge, USA)
In 2004, we conducted a survey of the magnetic interference issues at neutron scattering facilities worldwide. We found numerous incidents where the fringing field of a sample magnet (1) interfered with field-sensitive instruments such as Neutron Spin Echo spectrometer; (2) interfered with polarized neutron components; and (3) interfered with detectors that use photo-multipliers; and (4) magnetizing instrument components such as sample table and radiation shielding. The interference resulted in substantial loss of beam time and in some cases damages to the instruments and/or magnets. Several recommendations were made to the SNS as a result of the survey. One of the suggestions was to develop self-shielded sample magnets to reduce the fringe field at its source. While self-shielded solenoid magnets are used, e.g. in Nuclear Magnetic Imaging, self-shielded split-pair magnet with opening for neutron passage and asymmetric field profile for spin-transport needs to be developed.
SNS then decided to adopt a stray field policy soon after in late 2004, being 5 Gauss @ 0.5 meter, 0.05 Gauss 5 meter, but provision for exceptions. By developing self-shielded magnets, we will minimize the negative impact of magnetic interference in our facilities.
SNS is the first in the world to specify actively shielded neutron magnets, the 5T vertical field system SLIM SAM (Shielded Asymmetric Magnet) was delivered in March 2008 and is ready to be commissioned on a beam line during May 2008. We are also looking at a 16T vertical field system, which has had its design finalized and now has a 2009 delivery.
High Pressure for Neutron Scattering at Low Temperature and High Magnetic Field
R. Sadykov - Inst. Nuclear Research RAS (Moscow, Russia), Institute for High Pressure Physics RAS (Troitsk, Russia)
Hydrostatics: We have tested a number of Fluorinert types and found the limits of solidifications for each. The maximum is obtained for FC87 at 23kbar.
Clamp cells: High pressure clamp cells was made from TiZr zero alloy, hard Al and hard non magnetic HNU (NiCrAl) alloys for TOF-method on the pulsed and continuous neutron sources are presented in this report. These cells are designed for powders and single crystals for diffraction and inelastic neutron scattering studies. It is possible to put them in standard cryostats (even in dilution fridge inserts) and in high magnetic field cryomagnets up to 6-14T. Single crystal or powder NaCl (a pressure calibrant) and Fluorinert (a pressure medium) were used in all experiments on the neutron sourсes SINQ (Swiss), ISIS (UK), HMI (Germany) and ILL (France). Some of these cells were used for the investiagations of the magnetic spiral in ZnCr2S4, CsCuCl3 and MnSi under pressure. For investigating the form-factor dependence of magnetic localized moments in CePd(Rh)2Si2 under pressure up to 40kbar and 10T with polarized neutrons on D3(ILL), we made a new nonmagnetic composite piston/cylinder type cell from TiZr+HNU.
Presses: Two different geometries of low temperature press for “in situ” investigations by neutron scattering are presented for discussions.
1000°C in a Superconducting 5T Magnet
C. Redmon - High Flux Isotope Reactor (Oak Ridge, USA)
For the first time, in-situ, time-resolved measurements of the shift in the equilibrium phase transformation temperatures were achieved in the use of a superconducting magnet for neutron scattering, used in conjunction with a custom induction furnace. The materials studied required magnetic fields of 4.8T and sample temperatures >900°C. This pioneering research, using neutron diffraction methods at the WAND, will allow for future understanding and development of the next generation of structural and functional Fe-C binary alloys. Predictions had been made in the past by studying the phase equilibrium on samples no longer under applied field that are now proven to be true through this new capability.
The design and testing of the insert were initially full of catastrophic ‘what ifs’. The failure of the insert isolation or protection circuits would permanently damage the 5 Tesla cryomagnet. Many design difficulties were overcome to allow a sample to be at 1000°C while inserted into a 4.2K magnet system with a dynamic flow VTI. Also, prior experience at the National High Field Magnetic Laboratory, with the same compositions and furnace, also proved that extreme RF fields generated by the induction heater reeked havoc on most every piece of electronic equipment around it. Problems during the experiment included temperature sensor offsets, ‘virtual’ magnet quenches, and the inability to ramp field in any configuration. The insert was successfully run in laboratory to 1000°C at 5 Tesla, and on instrument to 900°C at 4.8 Tesla.
Sample Cooling in the forthcoming 25T-Hybrid-Magnet - Requirements, first Sketches and Approaches
J. Heinrich - Hahn Meitner Institut (Berlin, Germany)
The HMI is already in the process of preparing the sample environment equipment for its planned High Field Magnet at the EXED instrument. For testing purposes, a sample cooling system for the existing vertical warm bore magnet VM-5 was built. The targeted parameters were very soft: a lowest temperature of approx. 50K and a later use in combination with a high temperature top part for a temparature range of some hundred Kelvin were considered.
The major difficulty for sample cooling in this magnet is the same as expected for the High Field Magnet: the distance of about 1.5 m between sample position and possible positions of the cryo cooler. Additionally we have a nearly horizontal arrangement in the High Field Magnet. To see what can be achieved at least in the High Field Magnet, a very basic, transferable design was chosen and common workshop materials instead of special cryogenic materials were used.
Moreover the design was modelled in a computer simulation to investigate the used software’s possibilities. The cool down behaviour will be shown and some comparisons between experimental and simulated data will be discussed.
Sample Environment in Soft Condensed Matter at the ILL
G. Fragneto - Institut Laue Langevin (Grenoble, France)
Current activities in soft matter and plans for the future regarding sample environment for soft matter experiments at the ILL will be presented. Because of their fragile nature, soft-matter samples are often temperature sensitive or evolve (age) on long time-scales. Many samples are thus ideally prepared and pre-characterized immediately prior to neutron scattering experiments for an efficient use of neutron beam-time. For this reason the creation of a Partnership for Soft Condensed Matter (PSCM) on the ILL-ESRF site has been considered recently and strongly supported by the ILL management, following the successful example of the Partnership for Structural Biology and also given the strong support of the Scientific Council. Optimization of sample environment for soft matter experiments is to be dealt within the Partnership as well as facilities for sample preparation and characterization. Development of in-situ complementary techniques will be also pursued.
Existing specialised ILL sample environment for soft matter experiments include : Stopped Flow (D22), Humidity Chambers (D16, D17, IN11), Rheometer (D11), Pressure cell (D11), Solid/Liquid Cells (D17), Syringe pumps (D17), Langmuir trough (FIGARO)
For in-situ complementary techniques, a Brewster Angle Microscope is available (FIGARO). There is also a project for complementary Light Scattering and SANS on D11.
The requirements for more specialised sample environment items as well as equipment for the Soft Matter Laboratory will be presented and the need of a strong interaction with the ILL Sample Environment Group will be discussed.
Aerodynamic Levitation and Laser Heating — Current and Future Developments at the ILL
L. Hennet - CNRS-CEMHTI (Orléans, France)
Studies of the liquid state present an obvious fundamental interest and are also important for technological applications since the molten state is an essential stage in various industrial processes.
At very high temperature, it is difficult to use conventional furnaces, which present major problems. In particular, the sample can be polluted by the container and the structural properties of the materials can be affected by the crucible. This has led to the development of containerless techniques and their use at synchrotron and neutron sources to study the structure and the dynamics of high temperature liquids.
Different levitation techniques have been developed by various groups around the world and at the CEMHTI, we have chosen to work with the aerodynamic levitation which is a simple way to suspend samples by using a gas flow. The advantages of this technique are the simplicity and compactness of the device, making it possible to integrate it easily in different kinds of experiments
Over the past 10 years the CEMHTI has developed various devices for neutron investigations at ISIS and ILL. In this presentation, I will give an overview of the aerodynamic levitation setups currently available at the ILL.
Superconducting Vortices in CeCoIn5: Toward the Pauli-Limiting Field
M. Kenzelmann - Paul Scherrer Institute (Villigen, Switzerland)
Many superconducting materials allow the penetration of magnetic fields in a mixed state in which the superfluid is threaded by a regular lattice of Abrikosov vortices, each carrying one quantum of magnetic flux. The phenomenological Ginzburg-Landau theory, based on the concept of characteristic length scales, has generally provided a good description of the Abrikosov vortex lattice state.
We conducted neutron-scattering measurements of the vortex lattice form factor in the heavy-fermion superconductor CeCoIn5 and found that this form factor increases with increasing field - opposite to the expectations within the Abrikosov-Ginzburg-Landau paradigm. We propose that the anomalous field dependence of the form factor arises from Pauli paramagnetic effects around the vortex cores and from the proximity of the superconducting state to a quantum critical point. Our experiment can be seen as the first evidence of a novel superconducting vortex structure in solid matter. This study is a good example of the importance of specialized low-temperature and high-field sample environment in the study of condensed matter using neutron scattering.
Neutron Scattering Investigations in Extreme Sample Environments
T. Chatterji - Institut Laue Langevin (Grenoble, France)
I shall review the results of neutron scattering investigations on several magnetic materials at millikelvin temperatures, under high magnetic field up to 14 T and also under hydrostatic pressure up to about 30 kbar carried out at ILL and HMI. I shall describe and discuss the experiments where some of these extreme sample environments were combined.
The results of our neutron scattering investigations of hyperfine-induced nuclear spin ordering and nuclear spin waves in Nd2CuO4 and related compounds at millikelvin temperatures will be discussed in some details. I shall also describe the results of our recent neutron scattering investigations on the magnetic structures, magnetic (H,T) phase diagram and spin waves in newly discovered multiferroic meterials TbMn2O5, YMn2O5, DyMn2O5 and CuO. The pressure-temperature phase diagram of the Kondo lattice compound CeSb will be discussed. Finally I wish to discuss the new physics that can be investigated if the present sample environment limits could be extended to a reasonably moderate amounts.
Cryocooler and Cryostat Options for Neutron Scattering
R. Bains - Advanced Research Systems, Inc. (Macungie, USA)
Over the past 10 years ARS has worked closely with the NS user groups to develop and offer CCR’s for neutron scattering experiments.
We have the unique distinction of manufacturing the cryocooler as well as the customized cryostat to user specifications. Cryocoolers are available from the specialized 1.7K cooler developed at ILL and licensed to ARS, to the standard 4K, 30K and 80K systems which have been available for almost 10 years now.
Cryostat design is based on the experiment and can be offered as sample in vacuum and sample in vapour configurations, each design has its advantages in sample exchange/throughput and temperature range.
The presentation will cover the advantages and disadvantages of each type of cryostats as well the proper selection of cryocoolers.
World’s Highest Field Actively Shielded Split Coil Magnet for Neutron Scattering
R. Gilardi, J. Hinderer - Bruker BioSpin AG (Fällanden, Swtizerland)
A new actively-shielded 16T split-coil magnet system is being developed and constructed by Bruker BioSpin. This will represent the first high-field actively shielded split-coil magnet for neutron scattering experiments. The magnet is a geometrically symmetric split coil, which can be operated in both symmetric and asymmetric field modes (for experiments with polarized neutrons).
In order to minimize the stray fields, a superconducting shield coil is integrated in the magnet assembly. The design of an actively shielded split coil magnet for neutron scattering is different from previously manufactured actively shielded NMR and laboratory magnets, which are standard products of Bruker, and poses some new specific questions, such as the design of the shield coils and of a suitable supporting structure. Moreover, the materials used in the split region have been evaluated with respect to mechanical stability, neutron transparency and activation in close collaboration with the Paul Scherrer Institute. The first magnet system is in the construction phase and will be installed at the Spallation Neutron Source (SNS) in USA in 2009.
Oxford Instruments NanoScience
P. Pickering, A. Catalfamo - Oxford Instruments NanoScience (Oxford, United Kingdom)
Oxford Instruments NanoScience supports the neutron scattering community by providing low temperature (as low as 10 mK) and high magnetic field (up to 15T) sample environments, tailored to neutron scattering applications.
Oxford Instruments has a unique mix of expertise gained over the years by working in partnership with every major neutron scattering facility to provide state of the art magnets and cryogenic systems. We are also proud to have pioneered the design of magnet systems for neutron scattering. We can combine field orientation, field strength, neutron access and low temperature environment to provide you with a uniquely powerful measurement platform. More recently, to overcome the growing problem of helium shortage, Oxford Instruments has been developing Cryogen-free solutions. As a result came the TritonTMDR, pump free Cryofree® dilution refrigerator providing ease of operation and flexible configuration. Magnet and low temperature insert systems with integrated helium recondensing options are also now available. Come and see us at our booth and we will be delighted to discuss your specific requirements.
Pulse Tube Cryocoolers: an Option for Cooling without Cryogenic Liquids
G. Thummes - TransMIT GmbH / Centre for Adaptive Cryotechnology and Sensors (Giessen, Germany)
Among all types of regenerative cryocoolers, only the pulse tube cooler (PTC) operates without moving cold parts. This unique feature of the PTC results in high reliability, reduced vibrations, and reduced magnetic interference, which makes it very attractive for cooling without the need for liquid helium or nitrogen. For more than one decade, the TransMIT-Centre in Giessen has been developing and manufacturing various types of PTCs for operating temperatures between 2.2 K and about 150 K. Two-stage PTCs are available that supply cooling powers at 4.2 K ranging from 0.15 to 1.1 W with electrical input powers from 2 to 10 kW. Demonstrated applications of these PTCs are, for example, “dry” cooling of Josephson-voltage standards, superconducting magnets, laboratory cryostats, and pre-cooling of sub-Kelvin coolers. Other types of TransMIT-coolers are lightweight, single-stage PTCs that operate on linear compressors with only 100 W power consumption, and which deliver about 2 W of cooling power at 80 K. All of the above coolers can be adapted to the particular requirements of the user.
Electronic Developments in ISIS Sample Environment in 2007
D. Cowdery - ISIS Rutherford Appleton Labs (Didcot, United Kingdom)
This talk describes progress in four areas of electronics made during 2007. The areas covered are motion control, thermometry, experiment control and instrumentation.
Motion control covers the use of the ISIS Standard Motion Controller in many varied locations, its degree of adoption and an analysis of failures since installation began. An example of a 5 axis goniometer is shown.
In thermometry a description is given of the next generation triple Eurotherm 3504 controller. Full electrical isolation is maintained between the three channels, each of which has a 2 μV resolution and a 5 digit display to the microvolt range. We use a novel system to control power at low levels but retaining high power capability.
The need for more versatile experiment control has forced us to develop a Universal Interface Box. Its function is to connect various interface types between pieces of experimental equipment. It has the capability to cross connect interfaces of the following types:- NIM, serial string generation & parsing, TTL, fibreoptic, analog and relays. Advanced control will enable it to be configured by remote script file. The prototype has already given good service using NIM to ASCII serial strings with timed gaps and analog output. Production of these units us now underway.
Instrumentation issues have centred around low frequency vibration measurements, particularly in Pulse Tubes. A laser based method of analysis is described with a frequency response down to mHz.
Portable Automated Pressure and Temperature Control System
D. Maierhafer - High Flux Isotope Reactor (Oak Ridge, USA)
A portable automated pressure and temperature control system has been developed to control the environment of fluid confinement cells used for neutron scattering research. This system was built from commercially available parts to minimize cost and increase reliability. It is rated to operate at pressures from 0 bar (0 PSIA) to 87.2 bar (1264 PSIA), and measures pressure with 0.0031% full scale accuracy, which corresponds to ±0.003 bar (±0.039PSI) at maximum pressure.
Pressure control is accomplished by dithering fast response (5 ms) solenoid valves to move packets of gas. Valve control can be switched between auto and manual mode through the use of a keyswitch. Temperature control is accomplished using a closed loop PID controller. Heating power is 1200W maximum with temperature measurement accuracy at the sensor of ±51 mK at 300K. The software algorithm is implemented using LabVIEW and steps through a predefined sequence of temperature and pressure setpoints to automate fluid dosage. Temperature and pressure are continuously logged and the SANS measurement can be started once the predefined stability criteria for temperature and pressure are met (i.e., the thermal and sorption equilibria are reached). This mechanism allows measurement with high accuracy and can make efficient use of an instrument 24/7. The software runs as stand-alone, and is controlled through an Ethernet connection. The system contains a reference volume for simultaneous volumetric sorption measurements.
Reconsidering ILL Cryostats Electronics
N. Belkhier - Institut Laue Langevin (Grenoble, France)
For more than 20 years, ILL use the combination of a Carbon probe and a platinum probe for measuring the temperature in Orange cryostats (1.5 - 320K). It was assumed that all Carbon sensors are almost identical (one common calibration curve) and it necessitated the use of a controller able to regulate the temperature from a weighted sum in the range 20 - 50K where both sensors are taken into account. For this purpose, the ILL had developed and used its own temperature controller featuring sensors auto-identification, 110W heating power and enough memory for storing 140 calibration curves and PID parameters. ILL had also developed its own cryogen level monitors at a time where there was no available commercial units.
Today, things have changed and ILL have therefore started the ambitious project to replace the Carbon probes mounted on ≈70 cryostats and ≈150 sample sticks with Cernox sensors, the ILL temperature controllers with LakeShore 340 units, and the cryogen level monitors and cold-valve controllers with programmable units made from commercial parts. We present these new products as well as a simple micro-controller based system that sets automatically the LakeShore controllers after connecting the leads to a cryostat or a stick.
Window Wars: Quartz vs. Titanium
E. Fitzgerald - NIST Center for Neutron Research (Gaithersburg, USA)
At the NCNR we have one horizontal field superconducting magnet for use on two SANS and one USANS instruments with a maximum field of 9T. The original design for the bottom of the sample well used quartz windows epoxied into a titanium block. On the first experiment, this arrangement blew out. Although this case was definitely user error, in the following years we have had an increasing number of problems with the windows leaking unexpectedly. Recently it became such a problem that the quartz windows were removed and titanium windows were permanently welded in. Knowing that this was an irreversible change we also began work on a new quartz “cup” design that would combine the low background of quartz windows with the robust nature of titanium windows. This talk will cover the development, implementation and results of the quartz “cup” design as well as draw comparisons with the previous designs.
Closing session "The (final) summary"
M. Meißner - Hahn Meitner Institut (Berlin, Germany)
Michael's private summary of the workshop...