Summarised by: Jose.C.Gomez Sal. 12 Jan 1999
| Countries | Sent | Received | % Received |
| France | 67 | 10 | 14.9 |
| United Kingdom | 53 | 13 | 24.5 |
| Germany | 46 | 5 | 10.5 |
| Spain | 22 | 9 | 40.1 |
| Switzerland | 22 | 6 | 27.3 |
| Italy | 17 | 2 | 11.8 |
| Austria | 0 | 0 | 0 |
| Others | 5 | 1 | 20.0 |
| TOTAL | 237 | 46 | 19.4 |
Please remember that this is a summary of the replies to the questionnaire: it is not always self-consistent.
D1B (27) D2B (22) D1A (14) D20 (15) D4 (5)
The combination of D20 with D1B or D2B, or D1B with D2B is very common.
Users from particular countries did not prefer particular instruments.
Scientific areas:
D1B: Magnetism films physisorbed on graphite;
D2B: Phase transitions. Structure refinements. Phase separation. Chemistry.
D20: Thermodiffractometry: Kinetic processes, colloids, liquid metals.
D1A: Crystal Structures. Stress/Strain
D4: Glass structures, aqueous solutions; Gd and Sm, Eu based alloys: Magnetic structures.
More than 3 experiments per year ............................................................... 7
About 1,2 or 3 experiments per year ......................................................... 30
Occasional: once every 3 years ................................................................... 9
The most cited reasons are:
D1A: High resolution (after the upgrade); less demand; good stability of the detectors; facilities for sample environment.
D1B: Good flux, high intensities, suitable wavelength; adequate for magnetic structures. Facilities for dilution fridge, pressures, furnaces.
D2B: High resolution and good angular range, very low background. Combination of resolution and flux.
D20: High flux, use of small samples. Thermal evolution. Possibility for real time experiments.
D4: Short wavelength, good detector stability.
Yes (26); No (20)
No question about D20; the best instrument of its kind when it works.
A general comparison between TOF and constant wavelength diffractometers
(CWD) could be summarised as follows: many users stressed the complementarity
of both types of instruments.
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|
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| Smaller l range, but better resolution at lower Q. | Larger Q-range (better values for temp. factors). |
| Magnetic studies. | Not so good for magnetic diffraction (very low intensity at larger l). |
| Simpler peak shapes. | Complicated peak shapes. |
| More complicated mechanics. Possibility of detector positioning errors. | Mechanically stable (no mobile parts). |
| Less good for high pressure. | Better for high pressure. |
| Better at low temperature. | Worse for low temperature (?) |
| Data analysis easier. | More difficult data analysis. |
Comparison of specific instruments (with TOF except *CWD).
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|
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| Better resolution plus background in high d-spacing | Higher resolution at lower d-spacing, poorer Fourier maps. Data analysis more difficult |
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| A bit less resolution, longer overall scan time (12 hours). Higher flux | Higher backgrounds, 2-3 hours scan time, better refinements of ADP's |
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|
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| High flux | Much lower background (due to the collimator) |
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|
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| Higher flux | Better for H substitutions, difficult to manipulate the data |
Many of the users prefer ILL instruments, but without giving special reasons, compared to POLARIS, LAD, HRPD, SXD (too low flux) at ISIS; Los Alamos; DN2, Dubna; DCM, Villingen; G6.1, LBB; SLAD, Studsvik.
30 users answer yes, very good or excellent.
Hardware: lack of sample changers at low or high T
D1B was not updated since quite some time. Poor electronics and acquisition data
D20 problems with cryostats, monitor and of course detectors.
Software: Interface VMS - UNIX, should be improved. Lack of programs to treat overlapping peaks (ABFFIT seem to be not supported) (?)
Immediate visualisation of data needs to be improved, LAMP is slow and cumbersome.
- Give some time for short test experiments, out of Scientific Council sessions.
- Improve cryostat-instrument interface on all diffractometers (furnaces, electric and magnetic fields, small ovens close to RT). Furnace operating in air, thermogravimetric analysis.
- Improve the software/users interfaces. Use the same type of software for all instruments.
- D1B and D20: radial collimators to remove Bragg peaks from sample environment. Improve detectors shielding.
- Texture/strain-stress: movements of all motors are too slow. Euler cradle needed.
- D20: Accessories to decrease the FWHM, and reduce the background (big chuck of V). Eventually have the option of a 3He polarisation filter.
- A standard slit is needed to measure absorption
- D4: more detectors (done ?)
- D1A: A better monochromator (done ?)
- D1B: improved neutron flux with the Ge monochromator (done ?). Extend the detector to cover all 2q range, without moving the detector bank.
Fundamental: 31
Materials characterisation: 20
Develop new techniques in situ: 7 (high pressures alignment testing, etc.)
Applied research: 7
- All instruments will be useful, specially D20, D1A and D2B, with special environments (Pressure, H field, and as a complement to synchrotron machines).
Scientific areas for the future:
In situ preparation and kinetics.
Glaciology, geology, palaeontology. Defects in structures.
Whatever hot topic comes up in solid state physics and chemistry.
D4: Carbon nanotubes, liquids in confined geometry. Polymers, Dielectric response in high frequency particle dynamics.
- Super high flux increasingly important (small/short lived/dilute samples)
- Improve the resolution of D2B or a new D2B high resolution diffractometer. Ultimate powder diffractometer, with a fixed high resolution PSD.
- A new D1B with 800 cells.
- Complaints about the conversion of D1B to a CRG.
- Cold neutron powder diffractometer.
- Polarised neutrons using He3 filters
- SANS with very low moment transfer
- Developing TOF for texture, increased number of detectors