55001750
Design and construction of a high-duty factor photocathode electron gun
Under a joint collaboration between Grumman and BNL, a high-duty factor (>1%) photocathode electron gun is being constructed for use at the ATF facility at BNL. This gun was designed as the electron source for the proposed UV FEL Users' Facility at BNL. The thermally induced stresses exceed the yield strength of OFHC copper. For this reason, the gun is fabricated from GlidCop, an aluminum oxide dispersion strengthened copper alloy.<<ETX>>
118755074
Design and construction of a Compact Infrared Free Electron Laser CIRFEL
The 5-15 micron Grumman Compact Infra Red Free Electron Laser CIRFEL which will produce extremely short pulses of tunable radiation under construction is described. Electron pulses are produced at a repetition rate of up to 10 Hz by the illumination of a single crystal <001> LaB/sub 6/ photocathode with a photon injector, a 6-10 psec, 349 nm (frequency tripled Nd-YLF) laser mode locked to the 20th subharmonic of 2856 MHz. Photoelectrons are further accelerated and guided to the superconducting microwiggler by a robust beam transport system through an achromatic bend. The /spl sim/10 MeV electrons interact with the optical radiation inside a near symmetric laser cavity. The FEL output will be coupled out through a hole in one of the cavity mirrors. The CIRFEL system is expected to be delivered in 1994.<<ETX>>
120207704
Design of a high-brightness, high-duty factor photocathode electron gun
Abstract The proposed UV-FEL user's facility at Brookhaven National Laboratory will require a phatocathode gun capable of producing short ( ps ) bunches of electrons at high repetition rates (5 kHz), low energy spread ( ), a peak current of 300 A (after compression) and a total bunch charge of up to 2 nC. At the highest charge, the normalized transverse emittance should be less than 7π mm mrad. We are presently designing a gun that is expected to exceed these requirements. This gun will consist of 3 1 2 cells, constructed of GlidCop-15, an aluminum oxide dispersion strengthened copper alloy. The gun will be capable of operating at duty factors in excess of 1%. Extensive beam dynamics studies of the gun were used to determine the effect of varying the length of the first cell, shaping the apertures between cells, and increasing the number of cells. In addition, a detailed thermal and mechanical study of the gun was performed to ensure that the thermal stresses were well within the allowable limits and that copper erosion of the water channels would not occur.
56413579
A superconducting short period undulator for a harmonic generation FEL experiment
A three stage superconducting (SC) undulator for a high gain harmonic generation (HGE) FEL experiment in the infrared is under construction at the NSLS in collaboration with Grumman Corporation. A novel undulator technology suitable for short period (6-40 mm) undulators will be employed for all three stages, the modulator, the dispersive section and the radiator. The undulator triples the frequency of a 10.4 /spl mu/m CO/sub 2/ seed laser. So far a 27 period (one third of the final radiator) prototype radiator has been designed, built and tested.<<ETX>>
119274733
Cosmic Ray Tests of the Prototype TPC for the ILC Experiment
A time projection chamber (TPC) is a strong candidate for the central tracker of the international linear collider (ILC) experiment and we have been conducting a series of cosmic ray experiments under a magnetic field up to 4 T, using a small prototype TPC with a replaceable readout device: multi-wire proportional chamber (MWPC) or gas electron multiplier (GEM). We first confirmed that the MWPC readout could not be a fall-back option of the ILC-TPC under a strong axial magnetic field of 4 T since its spatial resolution suffered severely from the so called E × B effect in the vicinity of the wire planes. The GEM readout, on the other hand, was found to be virtually free from the E × B effect as had been expected and gave the resolution determined by the transverse diffusion of the drift electrons (diffusion limited). Furthermore, GEMs allow a wider choice of gas mixtures than MWPCs. Among the gases we tried so far a mixture of Ar-CF4-isobutane, in which MWPCs could be prone to discharges, seems promising as the operating gas of the ILC-TPC because of its small diffusion constant especially under a strong magnetic field. We report the measured drift properties of this mixture including the diffusion constant as a function of the electric field and compare them with the predictions of Magboltz. Also presented is the spatial resolution of a GEM-based ILC-TPC estimated from the measurement with the prototype.
17115362
An outlook from Europe
The global spread of the Coronavirus Disease 2019 (COVID-19) created a significant amount of market volatility and caused a steep sell-off in equity markets in March. While the situation remains incredibly fluid, and the full impact of the pandemic on companies’ valuations and earnings is not yet fully known, we believe companies that are able to weather this event-driven shock offer an extremely rare opportunity to invest in attractive businesses at historically low valuations. Companies with strong balance sheets, healthy margins, established and sustainable cash flows, and lower financial leverage should be better positioned relative to peers during and after this global health emergency.
110213019
A fast track trigger processor for the opal detector at LEP
Abstract A fast hardware track trigger processor being built for the OPAL experiment is described. The processor will analyse data from the central drift chambers of OPAL to determine whether any tracks come from the interaction region, and thereby eliminate background events. The processor will find tracks over a large angular range, |cos θ | ≲ 0.95. The design of the processor is described, together with a brief account of its hardware implementation for OPAL. The results of feasibility studies are also presented.
120331510
Neutral and radiative decay modes of the new resonances
Preliminary results are presented for decays of the new resonances J/ψ and ψ' into final states containing photons. Neutral final states at √s = 3.1 GeV are discussed. There are arguments that the spin of the Pc state at 3.5 GeV is different from 0. Final states π+π-γγ at 3.1 GeV are analysed on a statistical basis.