The weak force is the only fundamental interaction known to violate the symmetry with respect to spatial inversion (parity). This parity violation (PV) can be used to isolate the effects of the weak interaction in atomic systems, providing a unique, low-energy test of the Standard Model [see for example reviews 1, 2, 3]. These experiments are primarily sensitive to the weak force between the valence electrons and the nucleus, mediated by the neutral Z 0 boson and dependent on the weak charge of the nucleus, Q w . The Standard Model (SM) parameter Q w was most precisely determined in cesium (Cs) [4, 5] and has provided a stringent test of the SM at low energy. The SM also predicts a variation of Q w with the number of neutrons in the nucleus, an effect whose direct observation we are reporting here for the first time. Our studies, made on a chain of ytterbium (Yb) isotopes, provide a measurement of isotopic variation in atomic PV, confirm the predicted SM Q w scaling and offer information about an additional Z´ boson.The large PV observable in Yb was first predicted by DeMille [6], a prediction further supported by subsequent calculations [7,8,9] and confirmed by experiment [10,11]. The PV effect in Yb is approximately 100 times larger than that in Cs. Moreover, Yb has a chain of stable isotopes, allowing for an isotopic comparison of the effect [12]. Such a comparison has the potential to be a probe of neutron distributions in the Yb nuclei [13] and is sensitive to physics beyond the SM [14,15]. A related measurement, in which the PV effects are compared for different hyperfine components of isotopes with non-zero nuclear spin, is expected to improve the understanding of the weak interaction within the nucleus [3,16,17,18].The principle of our measurements is similar to that of the 1 st -generation experiment [10,11]. We optically excite Yb atoms in a beam, on the 6s 2 1 S 0 → 5d6s 3 D 1 transition ( fig. 1), in a region in which in addition to the applied optical field, static electric and static magnetic fields are applied to the atoms [19].The directions of the magnetic and static electric field and that of the optical-field polarization define the handedness for the experimental coordinate system. As the 1 S 0 and 3 D 1 states are of nominally same parity, an electric-dipole (E1) transition between them is forbidden by selection rules. In the presence of the weak interaction, however, mixing of the 1 P 1 state into 3 D 1 results in a E1 PV amplitude for the transition. The applied dc (or quasi-static) electric field results in additional mixing of these states, allowing for a larger and controlled Stark-induced E1 amplitude [20]. The Stark-induced and PV amplitudes will interfere with appropriate choice of field geometry. Field reversals flip the handedness of the field geometry, leading to a sign reversal of the Stark-PV interference term and a change in the transition rate. This change provides an experimental observable.We measured the PV effect in four nuclear-spin-zero isotopes ( 170 Yb, 172 Yb, 174 Yb a...

We describe the fabrication of the two NuSTAR flight optics modules. The NuSTAR optics modules are glass-graphiteepoxy composite structures to be employed for the first time in space-based X-ray optics by NuSTAR, a NASA Small Explorer schedule for launch in February 2012. We discuss the optics manufacturing process, the qualification and environmental testing performed, and briefly discuss the results of X-ray performance testing of the two modules. The integration and alignment of the completed flight optics modules into the NuSTAR instrument is described as are the optics module thermal shields. OVERVIEW OF THE OPTICS MODULESThe Nuclear Spectroscopy Telescope Array (NuSTAR) is a NASA Small Explorer (SMEX) satellite mission scheduled for launch in February 2012. The NuSTAR experiment contains two telescopes each consisting of an optic and a CdZnTe focal plane detector separated from each other by a 10-meter deployable mast (figure 1). The experiment is an extension and improvement on the design successfully employed in the HEFT balloon experiment (Harrison et al. 2005 1 ). NuSTAR will operate in the 6-79 keV energy band. More details on the mission, the overall instrument design and performance requirements and scientific objectives can be found in Harrison et al. 2010 2 .A blowup of an individual optics module is also shown in figure 1. Each layer of the optic has an upper and lower conic shell (equivalent to the parabola-hyperbola sections of a Wolter-I optic). Each shell is composed of multiple thermally formed glass segments. Each piece of glass is coated with a depth-graded multilayer. The enhanced reflectivity provided by the multilayers, along with the shallow graze angles afforded by the focal length of the optics (10.15 meter) provide high effective area over the NuSTAR energy band of 6-79 keV, and a field of view of 12 arcminutes by 12 arcminutes. There are 133 concentric layers which together form each optic. The glass layers (a glass-epoxy-graphite composite structure) are built up on a Titanium mandrel. Titanium support spiders located on the top and bottom of each optic connect it to the optical bench. The compliant, radially-symmetric spiders accommodate thermal expansion effects as well as dynamic loading. Thin x-ray transparent thermal covers on the entrance and exit apertures of the optic reduce thermal gradients by blocking direct view of the sun and deep space. Two flight modules, FM1 and FM2, were fabricated. A third module, FM0, was fabricated earlier and has Pt/SiC multilayers on the inner 89 layers. FM0 is a potential flight spare and is available to provide for more extensive X-ray characterization than is permitted for either of the flight modules, given the compressed delivery schedule of the optics.

The NuSTAR mission will be the first mission to carry a hard X-ray(5-80 keV) focusing telescope to orbit. The optics are based on the use of multilayer coated thin slumped glass. Two different material combinations were used for the flight optics, namely W/Si and Pt/C. In this paper we describe the entire coating effort including the final coating design that was used for the two flight optics. We also present data on the performance verification of the coatings both on Si witness samples as well as on individual flight mirrors.

Upon stimulation, plants elicit electrical signals that can travel within a cellular network analogous to the animal nervous system. It is well-known that in the human brain, voltage changes in certain regions result from concerted electrical activity which, in the form of action potentials (APs), travels within nerve-cell arrays. Electro- and magnetophysiological techniques like electroencephalography, magnetoencephalography, and magnetic resonance imaging are used to record this activity and to diagnose disorders. Here we demonstrate that APs in a multicellular plant system produce measurable magnetic fields. Using atomic optically pumped magnetometers, biomagnetism associated with electrical activity in the carnivorous Venus flytrap, Dionaea muscipula, was recorded. Action potentials were induced by heat stimulation and detected both electrically and magnetically. Furthermore, the thermal properties of ion channels underlying the AP were studied. Beyond proof of principle, our findings pave the way to understanding the molecular basis of biomagnetism in living plants. In the future, magnetometry may be used to study long-distance electrical signaling in a variety of plant species, and to develop noninvasive diagnostics of plant stress and disease.