New Experimental limit on Optical Photon Coupling to Neutral, Scalar Bosons

We report on the first results of a sensitive search for scalar coupling of photons to a light neutral boson in the mass range of approximately 1.0 milli-electron volts and coupling strength greater than 10$^-6$ GeV$^-1$ using optical photons. This was a photon regeneration experiment using the "light shining through a wall" technique in which laser light was passed through a strong magnetic field upstream of an optical beam dump; regenerated laser light was then searched for downstream of a second magnetic field region optically shielded from the former. Our results show no evidence for scalar coupling in this region of parameter space.Comment: pdf-file, 10 pages, 4 figures, submitted to Physical Review Letter

Axion Searches with Helioscopes and astrophysical signatures for axion(-like) particles

The first part reviews the working mechanisms, capabilities and performance of axion helioscopes, including the achieved results so far. The 2nd part is observationally driven. New simulation results obtained with the Geant4 code reconstruct spectral shape of solar X-ray spectra, and their isotropic emission and lateral size. The derived rst mass of the axion(-like) particles is ~10meV. The axion interaction with magnetic field gradient is a generic theoretical suggestion that could reconcile present limits with relevant solar X-ray activity. A short outlook of the experimentally expanding solar axion field is given.Comment: 31 pages, 18 figures. Aded 1 author, updated references. Accepted for the special issue of NJP on dark matter (July 2009

First lasing of the Jefferson Lab IR Demo FEL

As reported previously [1], Jefferson Lab is building a free-electron laser capable of generating a continuous wave kilowatt laser beam. The driver-accelerator consists of a superconducting, energy-recovery accelerator. The initial stage of the program was to produce over 100 W of average power with no recirculation. In order to provide maximum gain the initial wavelength was chosen to be 5 mu-m and the initial beam energy was chosen to be 38.5 MeV. On June 17, 1998, the laser produced 155 Watts cw power at the laser output with a 98% reflective output coupler. On July 28th, 311 Watts cw power was obtained using a 90% reflective output coupler. A summary of the commissioning activities to date as well as some novel lasing results will be summarized in this paper. Present work is concentrated on optimizing lasing at 5 mu-m, obtaining lasing at 3 mu-m, and commissioning the recirculation transport in preparation for kilowatt lasing this fall

The epithelial cholinergic system of the airways

Acetylcholine (ACh), a classical transmitter of parasympathetic nerve fibres in the airways, is also synthesized by a large number of non-neuronal cells, including airway surface epithelial cells. Strongest expression of cholinergic traits is observed in neuroendocrine and brush cells but other epithelial cell types—ciliated, basal and secretory—are cholinergic as well. There is cell type-specific expression of the molecular pathways of ACh release, including both the vesicular storage and exocytotic release known from neurons, and transmembrane release from the cytosol via organic cation transporters. The subcellular distribution of the ACh release machineries suggests luminal release from ciliated and secretory cells, and basolateral release from neuroendocrine cells. The scenario as known so far strongly suggests a local auto-/paracrine role of epithelial ACh in regulating various aspects on the innate mucosal defence mechanisms, including mucociliary clearance, regulation of macrophage function and modulation of sensory nerve fibre activity. The proliferative effects of ACh gain importance in recently identified ACh receptor disorders conferring susceptibility to lung cancer. The cell type-specific molecular diversity of the epithelial ACh synthesis and release machinery implies that it is differently regulated than neuronal ACh release and can be specifically targeted by appropriate drugs

Performance of the accelerator driver of Jefferson Laboratory's free-electron laser

The driver of Jefferson Lab's kW-level infrared free-electron laser (FEL) is a superconducting, recirculating accelerator that recovers about 75% of the electron-beam power and converts it to radiofrequency power. In achieving first lasing, the accelerator operated straight-ahead to deliver 38 MeV, 1.1 mA cw current through the wiggler for lasing at wavelengths in the vicinity of 5 {mu}m. Just prior to first lasing, measured rms beam properties at the wiggler were 7.5{+-}1.5 mm-mr normalized transverse emittance, 26{+-}7 keV-deg longitudinal emittance, and 0.4{+-}0.1 ps bunch length which yielded a peak current of 60{+-}15A. The waste beam was then sent directly to a dump, bypassing the recirculation loop. Stable operation at up to 311 W cw was achieved in this mode. Commissioning the recirculation loop then proceeded. As of this Conference, the machine has recirculated cw average current up to 4 mA, and has lased cw with energy recover up to 710 W

First results on energy recovery in the Jefferson Lab IR FEL

A recirculating, energy-recovery linac is used as a driver accelerator for Jefferson Lab's high average power FEL. CW beam of 5 mA design current is transported from the superconducting RF (SRF) linac to the wiggler for lasing, and then recirculated back to the linac for deceleration and energy recovery. About 75% of the beam power is extracted before the beam is transported to the beam dump. Energy recovery reduces power consumption, RF equipment capital costs, and beam dump shielding requirements. It is arguably essential as FEL technology is scaled to higher average power levels. To date 4 mA of CW beam has been energy recovered successfully. There is no evidence of RF instabilities due to the energy aperture of the transport system, momentum compaction or the phase of the decelerating beam. HOM power from the beam has interfered with the operation of the IR interlock detectors, designed to protect the warm waveguide window from thermal runaway. Installation of copper screens appears to have solved the problem. More detailed studies of the HOM spectra and their correlation to the beam properties are planned