ASHESI UNIVERSITY

It was December 2007 and Patrick Awuah, founder and president of Ashesi University, began updating his school's business plan. He looked back on the university's short history with pride-in only 10 years Awuah and his team had turned a lofty vision into reality. Ashesi had become one of the most respected educational institutions in Ghana, with about 100 top-notch students enrolling in its liberal arts program each year. But many challenges still lay ahead, not least of which was raising the $7.2 million needed to complete the first phase of construction for the permanent campus. There was the issue of academic dishonesty, which seemed to be on the rise at Ashesi and was directly at odds with the school's mission. Awuah also wondered how much longer it would be until he felt ready to begin replicating the model in other parts of Africa, which had always been part of the long-term strategy.It was December 2007 and Patrick Awuah, founder and president of Ashesi University, began updating his school's business plan. He looked back on the university's short history with pride-in only 10 years Awuah and his team had turned a lofty vision into reality. Ashesi had become one of the most respected educational institutions in Ghana, with about 100 top-notch students enrolling in its liberal arts program each year. But many challenges still lay ahead, not least of which was raising the$7.2 million needed to complete the first phase of construction for the permanent campus. There was the issue of academic dishonesty, which seemed to be on the rise at Ashesi and was directly at odds with the school's mission. Awuah also wondered how much longer it would be until he felt ready to begin replicating the model in other parts of Africa, which had always been part of the long-term strategy

Section on prospects for dark matter detection of the white paper on the status and future of ground-based TeV gamma-ray astronomy.

This is a report on the findings of the dark matter science working group for the white paper on the status and future of TeV gamma-ray astronomy. The white paper was commissioned by the American Physical Society, and the full white paper can be found on astro-ph (arXiv:0810.0444). This detailed section discusses the prospects for dark matter detection with future gamma-ray experiments, and the complementarity of gamma-ray measurements with other indirect, direct or accelerator-based searches. We conclude that any comprehensive search for dark matter should include gamma-ray observations, both to identify the dark matter particle (through the characteristics of the gamma-ray spectrum) and to measure the distribution of dark matter in galactic halos

Design and performance of the traveling-wave beam chopper for the SSRL injector

A pulsed, split-parallel plate chopper has been designed built, and installed as part of the preinjector of the SSRL Injector. Its function is to allow the linear accelerator three consecutive S-band bunches from the long bunch train provided by a RF gun. A permanent magnet deflector (PMD) at the chopper entrance deflects the beam into an absorber when the chopper pulse is off. The beam is swept across a pair of slits at the beam output end when a 7 kV, 10-ns rise-time pulse passes in the opposite direction through the 75 {Omega} stripline formed by the deflecting plates. Bunches exiting the slits have their trajectories corrected by another PMD, and enter the linac. Beam tests demonstrate that the chopper functions as expected. 9 refs., 5 figs

New final focus system for the SLAC linear collider

The final focus system of the SLC has been upgraded by replacing the final quadrupole magnets with higher gradient superconducting magnets positioned closer to the interaction point. The parameters of the new system have been chosen to be compatible with the SLD detector with a minimum of changes to other final focus components. Commissioning plans for the new system are also presented. 5 refs., 1 fig

An rf cavity for the B-Factory

The paper describes the proposed design for the 476 MHz accelerating cavity for the SLAC/LBL/LLNL B-Factory. This machine will require a high power throughput to the beam because of the large synchrotron radiation losses, and very low impedances for the higher order modes because of the high current proposed. Use of conventional construction in copper means that careful consideration has to be paid to the problem of cooling. The need for a high shunt impedance for the accelerating mode dictated the use of a re-entrant shape. This maximized the impedance of the fundamental mode with respect to the troublesome longitudinal and deflecting higher order modes, when compared to open or bell shaped'' designs. A specialized damping scheme was employed to reduce the higher order mode impedances while sacrificing as little of the fundamental mode power as possible. This was required to suppress the growth of coupled bunch beam instabilities and minimize the workload of the feedback system needed to control them. A window design capable of handling the high power was also required. 8 refs., 1 fig., 2 tabs

The introduction of trajectory oscillations to reduce emittance growth in the SLC linac

Emittance growth of accelerated beams in the 50 GeV linear accelerator of the Stanford Linear Collider (SLC) arises from the effects of transverse wakefields and momentum dispersion. These effects are caused by small misalignments of the beam position monitors, lattice quadrupoles, and accelerating structure and by the energy spectrum of the beam which changes along the accelerator. The introduction of strategically placed trajectory oscillations over finite lengths of the linac has been used to generate beam errors which cancel the emittance accumulation from these small unknown, random alignment errors. Induced oscillations early in the linac cancel effects which filament along the accelerator affecting mostly the beam core. Induced oscillations located at the center of the accelerator or beyond cancel wakefield and dispersion errors which do not completely filament but cause the beams to have, in addition, an apparent betatron mismatch and transverse tails. The required induced oscillations of a few hundred microns are reasonably stable over a period of several weeks. Of course, the optimum induced oscillations depend upon the beam charge. Emittance reductions of 30 to 50% have been obtained

Progress at SLAC on high-power rf pulse compression

Rf pulse compression is a technique for augmenting the peak power output of a klystron (typically 50--100 MW) to obtain the high peak power required to drive a linear collider at a high accelerating gradient (typically 200 MW/m is required for a gradient of 100 MV/m). The SLED pulse compression system, with a power gain of about 2.6, has been operational on the SLAC linac for more than a decade. Recently, a binary pulse-compression system with a power gain of about 5.2 has been tested up to an output power of 120 MW. Further high-power tests are in progress. Our current effort is focused on prototyping a so-called SLED-II pulse-compression system with a power gain of four. Over-moded TE[sub 01]-mode circular waveguide components, some with novel technical features, are used to reduce losses at the 11.4-GHz operating frequency

An interface configuration experiment on USML-1

Experiments were carried out for exotic'' rotationally symmetric containers aboard the first NASA United States Microgravity Laboratory Space Shuttle flight (USML-1). The containers have the property that they admit an entire continuum of distinct equilibrium rotationally-symmetric capillary free-surfaces for a given liquid volume and contact angle. It was found, after the containers were filled in orbit, that an initial equilibrium interface from the symmetric continuum reoriented, when perturbed, to a stable interface that was not rotationally symmetric, as predicted by the mathematical theory

A spectral study of gamma-ray emitting AGN

In this paper we present a statistical analysis of the gamma-ray spectra of flat-spectrum radio quasars (FSRQ) compared to those of BL Lacs. The average spectra and possible systematic deviations from power-law behaviour are investigated by summing up the intensity and the power-law fit statistic for both classes of objects. We also compare the time-averaged spectrum to that at the time of gamma-ray outbursts. The spectrum of the average AGN is softer than that of the extragalactic gamma-ray background. It may be that BL Lacs, which on average have a harder spectrum than FSRQs, make up the bulk of the extragalactic background. We also find apparent cut-offs at both low and high energies in the spectra of FSRQs at the time of gamma-ray outbursts. While the cut-off at high energies may have something to do with opacity, the cut-off at low energies may be taken as indication that the gamma-ray emission of FSRQs is not a one component spectrum.Comment: 8 pages, accepted for publication in A&

Damage and repair of irradiated mammalian brain

We have demonstrated that focal charged particle irradiation of the rabbit brain can create well-defined lesions which are observable by nuclear magnetic resonance imaging (NMR) and positron emission tomography (PET) imaging techniques. These are similar, in terms of location and characteristic NMR and PET features, to those that occur in the brain of about 10% of clinical research human subjects, who have been treated for intracranial vascular malformations with stereotactic radiosurgery. These lesions have been described radiologically as vasogenic edema of the deep white matter,'' and the injury is of variable intensity and temporal duration, can recede or progress to serious neurologic sequelae, and persist for a considerable period of time, frequently 18 mon to 3 yr. 8 refs., 6 figs