118814364
An electrostatic sweep plate device for emittance measurement of ion beams to 2 MeV
Electrostatic sweep plate devices have been used previously for the measurement of ion beam emittance. These devices may be routinely designed with an ultimate angle resolution of /spl plusmn/0.25 mrad or less. We have used a similar device for measuring the emittance of H/sup -/ and H/sup +/ beams exiting an RFQ at 1 MeV. This scanner will be used to characterize the beam exiting a low-power DTL at energies up to 2 MeV. The physics design changes consist primarily of increasing the length of the deflection plates and decreasing their separation to obtain high electric field at low deflection plate voltage. The front face of the scanner was made thicker and designed for water cooling to withstand the beam power at up to 2 MeV. The design of the scanner is discussed. This includes the device angular resolution and maximum acceptable angle. The thermal analysis that led to the design of the water-cooled front face is shown. Data showing the performance of the device and resulting emittance measurements at 1 MeV are presented.<<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.
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>>
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>>
118362382
News from CERN, LHC Status and Strategy for Linear Colliders
This paper presents the latest development at CERN, concentrating on the status of the LHC and the strategy for future linear colliders. The immediate plans include the exploitation of the LHC at its design luminosity and energy as well as upgrades to the LHC (luminosity and energy) and to its injectors. This may be complemented by a linear electron-positron collider, based on the technology being developed by the Compact Linear Collider and by the International Linear Collider and/or by a high-energy electron-proton collider. This contribution describes the various future directions, all of which have a unique value to add to experimental particle physics, and concludes by outlining key messages for the way forward.
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.
120636385
The laser system for calibration and monitoring of the OPAL jet chamber
Abstract In this report we describe the construction and performance of the laser system which was used in Summer 1989 for the initial calibration of the OPAL jet chamber after installation on the LEP beam axis and which has served as a monitoring tool since then. Two Nd: YAG lasers are used to generate 48 high precision double beams which enter the chamber at fixed positions. The main features of the roughly 450 optical components are described and the beam alignment procedures are explained. Results are given for jet chamber calibration constants such as drift velocity, Lorentz angle, and residual sagittas.
120673376
Performance of the OPAL jet chamber
Abstract The jet chamber of the OPAL experiment at the LEP e + e − collider is designed to measure the direction and the momentum of charged particles as well as the specific energy loss in the chamber gas. The jet chamber has been operated at LEP since August 1989 and has recorded 500 000 hadronic decays of the Z 0 , resulting in a good understanding of the stability and systematics of the chamber. Resolutions obtained in the measurement of particle direction, momentum, and specific energy loss are presented, as well as the corrections and calibration procedures necessary to attain original design goals. A momentum resolution of 6.8% for particles with a momentum of 45 GeV/ c and an energy loss resolution of 3–4% over all momenta have been achieved.
122337981
Search for scalar muons
Abstract The supersymmetric partner of the muon was searched for in a systematic way. No candidate was found and 95% CL limits on its mass were given for different cases. If it is stable, the limit is 20.9 GeV c 2 . If it decays into a muon and an invisible low-mass particle, the limit is 20.3 GeV c 2 . If it decays into a muon and an unstable neutral particle which decays further into a photon and an invisible massless particle, the limit is 19.2 GeV c 2 .