J. Ruz

An ultra-low-background detector for axion searches

A low background Micromegas detector has been operating in the CAST experiment at CERN for the search of solar axions since the start of data taking in 2002. The detector, made out of low radioactivity materials, operated efficiently and achieved a very low level of background (5×10-5 keV-1-cm-2-s-1) without any shielding. New manufacturing techniques (Bulk/Microbulk) have led to further improvement of the characteristics of the detector such as uniformity, stability and energy resolution. These characteristics, the implementation of passive shielding and the improvement of the analysis algorithms have dramatically reduced the background level (2×10-7 keV-1-cm-2s-1), improving thus the overall sensitivity of the experiment and opening new possibilities for future searches.

Characterization and simulation of soft gamma-ray mirrors for their use with spent fuel rods at reprocessing facilities

The use of a grazing incidence optic to selectively reflect K-shell fluorescence emission and isotope-specific lines from special nuclear materials is a highly desirable nondestructive analysis method for use in reprocessing fuel environments. Preliminary measurements have been performed, and a simulation suite has been developed to give insight into the design of the x ray optics system as a function of the source emission, multilayer coating characteristics, and general experimental configurations. The experimental results are compared to the predictions from our simulation toolkit to illustrate the ray-tracing capability and explore the effect of modified optics in future measurement campaigns.

The NIFFTE project

The Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) is a double-sided Time Projection Chamber (TPC) with micromegas readout designed to measure the energy-dependent neutron-induced fission cross sections of the major and minor actinides with unprecedented accuracy. The NIFFTE project addresses the challenge of minimizing major sources of systematic uncertainties from previous fission chamber measurements such as: target and beam non-uniformities, misidentification of alpha and light charged particles as fission fragments, and uncertainties inherent to the reference standards used. In-beam tests of the NIFFTE TPC at the Los Alamos Neutron Science Center (LANSCE) started in 2010 and have continued in 2011, 2012 and 2013. An overview of the NIFFTE TPC status and performance at LANSCE will be presented.

Micromegas for Axion Search and Prospects

The Micromegas technology can be used to construct very powerful detectors for low background, low energy measurements. A Micromegas X-ray detector has been used to search for solar axions in the CAST experiment at CERN. The detector has an active area of 7 cm × 7 cm, a very good x-y position, and a good energy resolution. It is built using low radioactivity materials and it is capable of low energy X-ray measurements of a few hundred eV. Despite the lack of external shielding the obtained background level is below 5 × 105 counts/keV/cm2/s. The detector is being upgraded with a reduced active area Micromegas module, a focusing X-Ray telescope and shielding, which are expected to further reduce the background by about two orders of magnitude.