Use Of Beam Time Research Articles

Small sample measurements at the low energy muon facility of Paul Scherrer Institute

The low energy muon spin rotation spectroscopy (LE-μSR) is primarily used to investigate thin films, surfaces, and interfaces of materials, which has matured at the Paul Scherrer Institute (PSI) and is routinely employed by users of the low energy muon (LEM) facility. However, because of the large beam spot and low implanted muons rate, LE-μSR measurements on small samples are difficult, requiring an optimal sample size of 25×25mm2. Recently, we have boosted our ability to measure small samples, down to 5×5mm2 area, by beam collimation and tuning. This achievement is crucial for the measurements of many magnetic and superconducting materials. Furthermore, we have devised a method that allows us to measure five small area samples mounted together on the same sample plate. We expect this method to further improve the efficient use of beam time at LEM.

Accelerating small-angle scattering experiments on anisotropic samples using kernel density estimation

We propose a method to accelerate small-angle scattering experiments by exploiting spatial correlation in two-dimensional data. We applied kernel density estimation to the average of a hundred short scans and evaluated noise reduction effects of kernel density estimation (smoothing). Although there is no advantage of using smoothing for isotropic data due to the powerful noise reduction effect of radial averaging, smoothing with a statistically and physically appropriate kernel can shorten measurement time by less than half to obtain sector averages with comparable statistical quality to that of sector averages without smoothing. This benefit will encourage researchers not to use full radial average on anisotropic data sacrificing anisotropy for statistical quality. We also confirmed that statistically reasonable estimation of measurement time is feasible on site by evaluating how intensity variances improve with accumulating counts. The noise reduction effect of smoothing will bring benefits to a wide range of applications from efficient use of beamtime at laboratories and large experimental facilities to stroboscopic measurements suffering low statistical quality.

DA+ data acquisition and analysis software at the Swiss Light Source macromolecular crystallography beamlines.

Data acquisition software is an essential component of modern macromolecular crystallography (MX) beamlines, enabling efficient use of beam time at synchrotron facilities. Developed at the Paul Scherrer Institute, the DA+ data acquisition software is implemented at all three Swiss Light Source (SLS) MX beamlines. DA+ consists of distributed services and components written in Python and Java, which communicate via messaging and streaming technologies. The major components of DA+ are the user interface, acquisition engine, online processing and database. Immediate data quality feedback is achieved with distributed automatic data analysis routines. The software architecture enables exploration of the full potential of the latest instrumentation at the SLS MX beamlines, such as the SmarGon goniometer and the EIGER X 16M detector, and development of new data collection methods.

Crystal sample pins and a storage cassette system compatible with the protein crystallography beamlines at both the Photon Factory and SPring-8

Protein crystallography beamlines at the two major Japanese synchrotron facilities (SPring-8 and Photon Factory) employ different crystal-exchange robots. The robots SPACE and PAM, installed at SPring-8 and the Photon Factory, respectively, accelerate crystal exchange and assist in the efficient use of beamtime. SPACE also supports customizable automatic data collection, in which an X-ray beam is irradiated at a manually determined position during the crystal evaluation process. However, this data collection requires special crystal-mounting screw pins made of polyacetal, which are not compatible with PAM. In order to give users the flexibility to collect diffraction data sets at either of the two synchrotrons, we have developed a compatible cassette system. Pins stored in the cassette can be mounted or demounted using either SPACE or PAM, and are compatible with the customizable automatic data collection provided by SPACE. Users can handle the pins and cassettes easily, employing common tools and techniques for efficient protein cryocrystallography experiments.

SU‐GG‐J‐79: Experimentally Optimizing Prompt Gamma Detection for Proton Therapy

Purpose: To model and optimize an experimental setup that could potentially provide in‐situ range verification during proton therapy. The approach relies on measuring the prompt gamma emission profile produced by a beam of protons traversing a medium to provide information on the actual distal dose falloff in real time. Method and Materials: Calculations were performed using the GEANT4 Monte Carlo toolkit and a well‐developed model of a therapy beam line at the Francis Burr Proton Therapy Center. A 150 MeV pencil beam of protons was transported through a cylindrical Lucite phantom and the prompt gammas emitted orthogonal to the beam direction were scored. Measurements were performed under similar conditions with beam intensities of approximately 5 nA using both an HPGe spectrometer and different scintillators. The experimental arrangement was then simulated as part of a design study to investigate a more optimized measuring geometry. Results: The measured and calculated gamma energy spectrum displayed several distinctive emission peaks corresponding to 12C, 16O, and 1H as expected. Depth profiles measured with 150 MeV protons using two different detectors exhibited distal falloffs that correlated with the Bragg peak and agreed well with calculated gamma‐ray emission profiles. Calculations found a significant neutron background that may be effectively reduced by energy deposit or possibly timing discrimination. Conclusion: This study highlights the necessity of performing accurate MC simulations to help interpret and design experiments under realistic conditions. Calculations, once properly correlated with measurements aid the effective and efficient use of beam time and will be used to optimize parameters for experiments such as collimation, shielding and detector media.

The BESSY constant length Rowland circle monochromator

Abstract The BESSY constant length Rowland circle monochromator (CL-RCM) was designed for high resolution spectroscopy in the soft x-ray region. The principle is based on a spherical grating/plane mirror assembly, which is moved between the fixed entrance and exit slits for photon energy scan. By this means, the Rowland conditions are fulfilled over an energy range of 270–590 eV, yielding excellent resolution. Fast beamline optimization and, most important, the efficient use of beamtime in routine user operation is considerably enhanced by the newly implemented on-the-fly measuring mode, as demonstrated by the first results obtained on the beamline.