Brightness Limitations in Multi-Kiloampere Electron Beam Sources

Heuristic relationships such as the Lawson-Penner criterion, used to scale Free Electron Laser (FEL) amplifier gain and efficiency over orders of magnitude in beam current and brightness, have no fundamental basis. The brightness of a given source is set by practical design choices such as peak voltage, cathode type, gun electrode geometry, and focusing field topology. The design of low emittance, high current electron guns has received considerable attention at Livermore over the past few years. The measured brightnesses of the Experimental Test Accelerator (ETA) and Advanced Test Accelerator (ATA) guns are less than predicted with the EBQ gun design code; this discrepancy is due to plasma effects from the present cold, plasma cathode in the code. The EBQ code is well suited to exploring the current limits of gridless relativistic Pierce columns with moderate current density (<50 A/cm/sup 2/) at the cathode. As EBQ uses a steady-state calculation it is not amenable for study of transient phenomena at the beam head. For this purpose, a Darwin approximation code, DPC, has been written. The main component in our experimental cathode development effort is a readily modified electron gun that will allow us to test many candidate cathode materials, types and electrode geometries at field stresses up to 1 MV/cm. 6 references, 6 figures

Online Monitoring of the Osiris Reactor with the Nucifer Neutrino Detector

Originally designed as a new nuclear reactor monitoring device, the Nucifer detector has successfully detected its first neutrinos. We provide the second shortest baseline measurement of the reactor neutrino flux. The detection of electron antineutrinos emitted in the decay chains of the fission products, combined with reactor core simulations, provides an new tool to assess both the thermal power and the fissile content of the whole nuclear core and could be used by the Inter- national Agency for Atomic Energy (IAEA) to enhance the Safeguards of civil nuclear reactors. Deployed at only 7.2m away from the compact Osiris research reactor core (70MW) operating at the Saclay research centre of the French Alternative Energies and Atomic Energy Commission (CEA), the experiment also exhibits a well-suited configuration to search for a new short baseline oscillation. We report the first results of the Nucifer experiment, describing the performances of the 0.85m3 detector remotely operating at a shallow depth equivalent to 12m of water and under intense background radiation conditions. Based on 145 (106) days of data with reactor ON (OFF), leading to the detection of an estimated 40760 electron antineutrinos, the mean number of detected antineutrinos is 281 +- 7(stat) +- 18(syst) electron antineutrinos/day, in agreement with the prediction 277(23) electron antineutrinos/day. Due the the large background no conclusive results on the existence of light sterile neutrinos could be derived, however. As a first societal application we quantify how antineutrinos could be used for the Plutonium Management and Disposition Agreement.Comment: 22 pages, 16 figures - Version

Status of beam transport with the ETA and ATA accelerators

Both the Experimental Test Accelerator (ETA) and the Advanced Test Accelerator (ATA) are 10 kA electron induction linacs. The ETA produces a 4.5 MeV, 30 ns pulse, and the ATA a 50 MeV, 70 ns pulse. The ETA has been operational since 1979, having produced over 6 million pulses. Both the beam breakup instability and lower frequency transverse motions of the beam have been suppressed by accelerator cavity damping and with a wire damping zone. These efforts will be summarized. The ATA has become operational within this last year. Full beam current operation has not yet been achieved because of low-frequency transverse motion and centroid drift of the beam. The beam breakup instability has also been observed but does not disrupt the beam. Efforts at finding the source of the drift and low frequency motion, as well as wire damping of these motions will be reported. 6 references, 6 figures

ANTARES: the first undersea neutrino telescope

The ANTARES Neutrino Telescope was completed in May 2008 and is the first operational Neutrino Telescope in the Mediterranean Sea. The main purpose of the detector is to perform neutrino astronomy and the apparatus also offers facilities for marine and Earth sciences. This paper describes the design, the construction and the installation of the telescope in the deep sea, offshore from Toulon in France. An illustration of the detector performance is given

The ALICE experiment at the CERN LHC

ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries. Its overall dimensions are 161626 m3 with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008

Induction linac-based FELs

The multikiloampere peak currents available from linear induction accelerators make high-gain, free-electron-laser-amplifier configurations feasible. High-extraction efficiencies in a single pass of the electron beam are possible if the wiggler parameters are appropriately ''tapered,'' as recently demonstrated at millimeter wavelengths on the 4-MeV ELF facility. Magnetic pulse power systems enable high-repetition-rate operation of the accelerator for high-average-power applications. Key issues involved in extending the technology to shorter wavelengths and higher average power are described

Optical-emission studies in the ion-focused regime

The utility of optical emissions for diagnostic purposes in the ion-focused regime is explored. Two possible uses of the emissions are examined: (1) the time delay of 337.1-nm emissions relative to 391.4-nm emissions is observed to scale with the beam-neutralization time, and (2) emissions at 391.4 nm may determine beam-current density at the front of the beam

Experiments on ETA comparing wire-conditioned and non-wire-conditioned beam propagation

This report describes experiments in beam propagation with the ETA beam during 1982 following accelerator cavity modifications which allowed a maximum beam current of up to 8 kA at the entrance to the propagation tank. A prominent new feature of the propagation in high pressure gas was an enhancement of the net current as the beam propagated. In some cases this enhanced current was nearly double the injected beam current. The strong current enhancement was associated with strong transverse hose motion of the beam. The absence of microwave emissions in the range from 6.6 GHz to 31 GHz indicates that this current enhancement is not due to a two-stream instability