SNS’s Powder Diffractometer POWGEN is preparing to launch a rapid access mail-in system for its users, who depend on the flexible, general-purpose instrument for a wide range of structural studies of novel materials.

Ashfia Huq, the lead instrument scientist, hopes to make the instrument available for rapid access users for a few days each cycle, offering data collection for two temperatures between 12 and 300 K per sample. Users would simply mail in their samples. ISIS powder diffractometer GEM in the UK currently offers such a service but only for room temperature experiments, Huq said.

“A lot of people who do powder diffraction want rapid access because if they have made a new material, they do not want to have to wait six months to write a proposal and then get beam time,” Huq said. “By then somebody else will have measured it.

“We could put the sample changer in for two days a month. If it works out and users are interested, we could put aside say, a few days per cycle, and have as many as 24 samples run in two days,” she said. “People just ship us the samples, and we run it and we give them the data.”

“Once we advertise that, that is going to have traction. The high-resolution powder diffraction beam line 11BM at the Advanced Photon Source in Chicago allocates 50% of their user beam time through a similar program. They have a robot-operated system set up, and it is a very popular program.”

POWGEN’s physical equipment completed commissioning in the spring of 2010, and the instrument is now in its third fully operational cycle of experiments. It can now measure data in a d spacing range of ~ 0.3 Å or less to 10.3 Å (angstroms = tenths of billionths of a meter). It is capable of collecting typical Rietveld statistics in ~1 to 2 hours from a 1.0 cm3 sample with a <0.2% resolution at short d-spacings and <1% resolution for nearly all d-spacings of interest.

The instrument specializes in magnetic materials such as high-Tc superconductors and metal insulator phase transitions, as well as nonmagnetic materials, polycrystalline materials for pharmaceutical compounds, metals and semi-conductors, and ferroelectric and thermoelectric materials. Recent proposals have included a lot of work on new battery materials.

In the four-month 2010-B cycle, POWGEN welcomed 20 user groups. In the 1st cycle this year, 2011-A, 41 experiments were conducted at POWGEN. “Three were for the Forschungszentrum Jülich, which is our partner user. We also did four program development and two proof-of-principle experiments. There were 32 general user proposals, from both here and outside,” Huq said. The instrument has had six publications in 2011, including two in the Journal of Physics: Condensed Matter. “And we are now looking at another ten manuscripts for submission. So this will grow very fast,” she said

The instrument team added 12 additional detectors before cycle 2011-A. The introduction of a new algorithm for the detectors and improvement in background shielding gave them a factor of 5.5 gain in count rates over the previous cycle. Over the upcoming winter outage, the instrument is taking delivery of a fine radial collimator for two different sizes. Such devices already operate at two other SNS instruments, the Backscattering Spectrometer (BASIS) and the Cold Neutron Chopper Spectrometer (CNCS). ARCS, another chopper spectrometer, is preparing to install one at the same time as POWGEN.

Sample environments at POWGEN that are available for general users include 24 sample changers (12-300 K), an ILL furnace (RT-1200°C), an orange cryostat (2-300 K), and a gas atmosphere furnace (RT-900°C, with gases available to do variable partial pressure of oxygen). More sample environments (such as the 5 Tesla magnet, pressure cells, etc.) are scheduled to be commissioned after the arrival of the fine radial collimators

Complete information for users, including mail-in sample instructions and proposal information, can be found at

“Short and sweet, we are open for business, and the real thing that is going to help us take off is the launch of this rapid access,” Huq said.