Information for VISION Users

Vibrational Spectrometer

VISION | BL-16B | SNS

Sample Enviroments

Closed Cycle Refregrators (CCR):

VISION has two dedicated closed-cycle refrigerators (CCRs), CCR20 and CCR29. Both systems are designed to achieve a base temperature of approximately 5 K; however, CCR20 typically demonstrates better cooling performance and reaches its base temperature more efficiently. One of the primary differences between the two systems is the size of the variable temperature insert (VTI). CCR20 has a smaller VTI bore diameter of 85 mm, whereas CCR29 has a larger bore diameter of 104 mm. In addition, CCR29 has a greater insertion depth than CCR20. The larger bore and increased depth of CCR29 provide greater flexibility for accommodating complex sample environments, including multi-sample changers and other specialized experimental setups. However, these design features also result in a larger thermal load, which can impact the cooling efficiency and base-temperature performance compared to CCR20.

Sample Containers:
There are a wide range of sample cans that are used at VISION. The most commonly used sample containers are vanadium PAC cans. We use 6 mm, 8 mm, and less commonly 10 mm diameter depending on the amount of sample available. Some users conduct experiments at both BASIS and VISION, in which they will usually use BASIS style aluminum cylindrical cans. We also have a series of cylindrical aluminum and steel cans that are used for gas loading and high temperatures. A more complete list of cells:

Vanadium PAC cans (usually 6 mm and 8 mm but sometimes 10 mm)
Steel cylindrical cells, conflat flanges with copper or aluminum gasket (gas loading or pressure up to 100 bar, )
Cylindrical aluminum cells (0.25, 0.325, 0.5, 0.625 inches diameter)
Aluminimum flat plate cells
BASIS aluminum cylindrical cans with various insert sizes
Quartz tubes/quartz capillaries (made/sealed on demand)
Clamps for aluminum pouches or other solid samples

Sample Changer:

VISION has an operational sample changer based on the chain-style design used on the TOSCA spectrometer at ISIS. The system is primarily designed for flat-plate sample cells, although adapters are available to accommodate PAC cans. Up to 23 samples can be loaded simultaneously. During operation, only the sample positioned in the measurement location is maintained at the requested temperature. The remaining samples are held at temperatures that vary depending on their position along the chain. Due to its size and complexity, the sample changer can only be used with CCR29. The smaller variable temperature insert (VTI) of CCR20 does not provide sufficient space to accommodate the sample changer assembly.

High Pressure Sample Enviroments:

The following high pressure cells are used at VISION:

Cell type	Max Pressure	Minimum T	Maximum T	H2 rated
CuBe Cell	5 kbar	ULT	100 ⁰C	yes
Autofrettage cell	4.8 kbar	ULT	100 ⁰C	No
BASIS Al pressure cell	100 bar	ULT	100 ⁰C	Yes
Pre-stressed Clamp cell	2 GPa	ULT	100 ⁰C	No
Diamond Anvil Cell	10 GPa	ULT	100 ⁰C	N/A

*ULT: Ultra Low Temperature

All cells can go to ultra-low temp, and we are generally not concerned with our pressure cells below 100 ⁰C If the user need to go above that, we can discuss and likely come up with something safe within a P-T envelope. It’s on a case-by-case basis. Moost of the high pressure experiments are set up by the high pressure sample environment group and uses the SITEC and/or Teladyne pressure intensifier. Using this intensifier, pressure changes have to be performed manually. When using hydrogen. gas, a CuBe high pressure cell needs to be used. Other gases are able to use a stainless steel autofrettage cell. There is one dedicated stick to be used for high pressure gas experiments.

Gas dosing and gas handling:

Many experiments conducted on VISION involve reactions or measurements under controlled gas environments. To support these studies, a dedicated gas handling panel is installed on the wall of the sample environment cave. The panel has a maximum operating pressure of 69 bar and is rated for hydrogen service. The system is equipped with two pressure gauges to provide accurate pressure measurements over different operating ranges. One gauge is optimized for pressures below 6 bar, while the second gauge is used for pressures above 6 bar. The VISION team is currently developing a more advanced gas handling panel that will provide enhanced capabilities and operational flexibility for future experiments. At present, the VISION sample environment cave has limited ventilation capacity. As a result, the use of certain gases is restricted, particularly toxic gases (e.g., SO₂, SO₃, and CO) and highly toxic gases (e.g., NO, NO₂, N₂O, and other NOₓ species). To address these limitations, SNS is commissioning a new gas handling system designed to meet the specific requirements of VISION. Once implemented, this system will significantly expand VISION's capability to safely handle a wider range of toxic gases within the operating limits and safety ratings of the system. Until the new system becomes operational, experiments involving toxic gases are supported on a case-by-case basis within limits approved by SNS safety personnel and the instrument team. Users planning experiments involving hazardous gases are encouraged to contact the VISION instrument team early in the proposal and experiment planning process to discuss feasibility, safety requirements, and available capabilities.

Para Hydrogen Covertor:

VISION has a ortho-parahydrogen converter that can be used to dose samples with up to 1 bar of parahydrogen. A displex head cools a catalyst below 20 K where the hydrogen condenses on the surface of the catalyst and converts to parahydrogen. Heating the system to evaporate the hydrogen will allow you to dose the sample with parahydrogen.

High temperature Furnace (HOT-20):

VISION has its own dedicated compact furnace based on the MICAS design. The furnace have a number of sample sticks available for gas loading, rapid cooling, and will be capable of reaching a maximum temperature of 1000^oC. The sample environment group at SNS/HFIR is responsible for the design, fabrication, and maintenance of the furnace.

In-situ photo stick:

VISION is equipped with an operational photochemistry sample stick that enables in situ photochemical studies using inelastic neutron scattering (INS). The system incorporates a laser diode source, which can be readily exchanged to provide different excitation wavelengths depending on the experimental requirements. The laser light is directed and focused onto the sample while neutron measurements are performed simultaneously, allowing real-time monitoring of light-induced structural and chemical changes. This sample environment is particularly well suited for investigating in situ photodimerization processes, photoactive materials, optically excited states, and photoinitiated chemical reactions. By combining controlled optical excitation with INS measurements, researchers can directly probe changes in molecular structure, dynamics, and vibrational properties under operating conditions.

VISION instrument lab:

VISION is equipped with an Instrument Support Laboratory located on the ground floor in Room TA-1165. The laboratory houses Raman spectroscopy and X-ray diffraction (XRD) systems, which are primarily used for preliminary sample characterization as well as the analysis of irradiated samples. In addition to characterization capabilities, the laboratory serves as a workspace for minor troubleshooting, maintenance, and assembly of sample environment equipment and associated components. This facility provides valuable support for both instrument operations and user experiments by enabling rapid diagnostics and preparation of experimental hardware.

Modeling INS Data

Comparison of simulated INS spectra to VISION experimental data using aClimax and Mantid software.

2climax.tar.gz – This script converts the calculated phonon modes (by various first-principles software packages) to .aclimax format.
cvs2nxs.tar.gz – This script converts the simulated INS spectra (output of aClimax, in .cvs format) to .nxs format for comparison to experimental data.
nxs2dat.tar.gz – This script converts multiple processed .nxs files to ASCII format (.dat).