Strangeness nuclear physics: a critical review on selected topics

Selected topics in strangeness nuclear physics are critically reviewed. This includes production, structure and weak decay of $\Lambda$--Hypernuclei, the $\bar K$ nuclear interaction and the possible existence of $\bar K$ bound states in nuclei. Perspectives for future studies on these issues are also outlined.Comment: 63 pages, 51 figures, accepted for publication on European Physical Journal

Basic Research Needs for Countering Terrorism

To identify connections between technology needs for countering terrorism and underlying science issues and to recommend investment strategies to increase the impact of basic research on efforts to counter terroris

A shutter design for time domain studies using synchrotron radiation at the advanced photon source

In general a variable repetition rate of the x-ray bunches is needed to explore time domain problems using x-ray radiation. In some instances the results of several hundreds or thousands of x-ray pulses must be averaged requiring the sample to be in the same time dependent state each time the monitoring pulse strikes. In the most advanced and most detailed version of this type experiment an intense laser pulse would be used to create an excited state from a relaxed ground state. An additional ``probe-pulse`` that follows the laser ``pump-pulse`` would examine the sample. The important point is that before a second x-ray pulse hits the sample, the system must return to its initial relaxed ground state prior to another laser pulse in order to prepare the same excited state again. Otherwise the second x-ray probes a different condition of the system than the previous x-ray bunch such that any data averaging scheme would be invalid. Our system is primarily designed for the Advanced Photon source (APS) at Argonne National Laboratory. In the 20-bunch mode of APS an x-ray pulse will occur every 177 nanoseconds, requiring each edge of a conventional two-blade ``shutter`` to travel at least 0.25 mm in {approximately}177 nanoseconds. Our key design principle employs a subsonic, rotating mirror whose period is slaved to the synchrotron intra-pulse period. The synchrotron x-ray bunches will be reflected a distance of about two meters to a narrow 0.5 mm slit just in front of the sample. The time that the reflected synchrotron spends striking the slit is given by 1/(4{pi}rf) where r is the radius from the center of the spindle to the slit, and f is the frequency of rotation of the spindle. A mirror rotating at a low 7,500 rpm (125 Hz) is sufficient to select a single synchrotron pulse. The very precise phase stability required by this method is currently available in rotating mirror devices for laser scanning. 11 refs., 2 figs

A shutter design for time domain studies using synchrotron radiation at the advanced photon source

In general a variable repetition rate of the x-ray bunches is needed to explore time domain problems using x-ray radiation. In some instances the results of several hundreds or thousands of x-ray pulses must be averaged requiring the sample to be in the same time dependent state each time the monitoring pulse strikes. In the most advanced and most detailed version of this type experiment an intense laser pulse would be used to create an excited state from a relaxed ground state. An additional probe-pulse'' that follows the laser pump-pulse'' would examine the sample. The important point is that before a second x-ray pulse hits the sample, the system must return to its initial relaxed ground state prior to another laser pulse in order to prepare the same excited state again. Otherwise the second x-ray probes a different condition of the system than the previous x-ray bunch such that any data averaging scheme would be invalid. Our system is primarily designed for the Advanced Photon source (APS) at Argonne National Laboratory. In the 20-bunch mode of APS an x-ray pulse will occur every 177 nanoseconds, requiring each edge of a conventional two-blade shutter'' to travel at least 0.25 mm in {approximately}177 nanoseconds. Our key design principle employs a subsonic, rotating mirror whose period is slaved to the synchrotron intra-pulse period. The synchrotron x-ray bunches will be reflected a distance of about two meters to a narrow 0.5 mm slit just in front of the sample. The time that the reflected synchrotron spends striking the slit is given by 1/(4{pi}rf) where r is the radius from the center of the spindle to the slit, and f is the frequency of rotation of the spindle. A mirror rotating at a low 7,500 rpm (125 Hz) is sufficient to select a single synchrotron pulse. The very precise phase stability required by this method is currently available in rotating mirror devices for laser scanning. 11 refs., 2 figs