摘要:

The year that has passed since the last CEBAF Summer Workshop has been a very eventful one, so in addition to welcoming you to the Continuous Electron Beam Accelerator Facility, I want to take this opportunity to bring you up to date on how we are meeting the scientific, technical, and funding challenges required for us to be ready to start physics in the Spring of 1994.

ISSN:0094-243X    

DOI:10.1063/1.42990

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

At the Continuous Electron Beam Accelerator Facility (CEBAF), under construction in Newport News, Virginia, a superconducting, recirculating, cw linac will provide a nominal 4 GeV, 200 &mgr;A electron beam for distribution to simultaneous nuclear physics experiments in three end stations. As of August 1992, the 45 MeV injector†with 18 supeconducting cavities in 21/4cryomodules identical to those being installed in the main acclerator†has completed its initial commisisioning stage and has validated systems design by meeting specifications in energy, current, and beam quality. Cryomodule production has reached a rate of two/month, 12 (of 40) linac cryomodules are installed in the 1300‐m‐circumference tunnel, and low‐power linac tests are being initiated. High‐power rf amplifiers and power supplies are installed, and checkout is proceeding. The 4800 W helium refrigeration plant is in commissioning and supports testing/commissioning operations. Helium transfer line installation is nearing completion. East arc dipoles are installed.The control system is operational for the injector and being installed in the accelerator. All major experimental equipment components are in industrial production, initial spectrometer carriage mechanical installation is proceeding in one end station, and scientific program planning is well advanced. Accelerator completion is scheduled for the first quarter of 1994, with first physics operations in the second quarter. Recent evaluation of energy potential shows the likelihood of ∼6 GeV at turn‐on, with evolutionary change to 8–10 GeV thereafter. A CEBAF R&D program for high‐power IR and UV free electron lasers based on superconducting rf technology is being proposed.

ISSN:0094-243X    

DOI:10.1063/1.42991

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

This paper reviews the status of the CEBAF experimental equipment as of the summer of 1992. At that time, the initial complement of experimental equipment had largely been defined, the major components were under contract, and the carriage for the HMS was being installed in the Hall C end station.If funding continues as expected, the first experiments will begin in Hall C in the Spring of 1994, with the startup of Halls A and B about a year later. It is hoped that the overview presented here will serve as a useful general reference for users and other interested scientists.This paper is divided into three parts which separately describe the status of the three Halls. Each part contains its own introduction, a desciption of the equipment currently being designed or built, and some discussion of instrumentation. For an introduction and overview of the Physics, please see contribution by J. D. Walecka later in this Proceedings. A brief discussion of some of the physics planned for Halls B and C is also included here. Also included in Part 3 is a brief summary of the schedule for Hall C, the first to start experiments.

ISSN:0094-243X    

DOI:10.1063/1.42980

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

In response to requirements for national laboratory technology transfer, CEBAF has proposed an industrial R&D initiative: a Free Electron Laser (FEL) User Facility based on an infrared FEL and an ultraviolet FEL, with the injector and the north linac of the CEBAF superconducting, recirculating accelerator serving as drivers. The initiative is a collaborative effort with four U.S. corporate partners and capitalizes on CEBAF’s superconducting rf technology. The FELs will provide monochromatic, tunable (3.6 to 1.7 &mgr;m and 150 to 260 nm), high‐average‐power (‐kW) light for technical applications and basic science studies. FEL capabilities will be competitive with those of similar initiatives worldwide. FEL operation will not impair beam delivered to CEBAF’s nuclear physics experiments. Substational commitments are in hand from the industray partners and the Commonwealth of Virgina for cost‐sharing the project with the Federal Government.

ISSN:0094-243X    

DOI:10.1063/1.42973

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

An overview is given of the physics program envisioned for CEBAF facility and how they can help in improving our knowledge of forces and interactions discribed by quantum chromodynamics. (AIP)

ISSN:0094-243X    

DOI:10.1063/1.42974

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Nucleon form factors provide fundamental input for nuclear structure and quark models. Current knowledge of neutron form factors, particularly the electric form factor of the neutron, is insufficient to meet these needs. Developments of high‐duty‐factor accelerators and polarization‐transfer techniques permit new experiments that promise results with small sensitivities to nuclear models. We review the current status of the field, our own work at the MIT/Bates linear accelerator, and future experimental efforts.

ISSN:0094-243X    

DOI:10.1063/1.42992

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

This paper surveys progress achieved in the spectroscopy of baryons in the period between the appearances of the reviews by the Particle Data Group in 1990, and their latest review in June 1992. We focus here on the baryons of interest at CEBAF.

ISSN:0094-243X    

DOI:10.1063/1.42975

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

In this talk, the problem of virtual pion contributions to nucleon properties is discussed. The infrared behavior of the pion propagator can lead to quantities being nonanalytic inm2&pgr;asm2&pgr;→0. It is shown that these nonanalyticities can lead to large systematic errors in the extrapolation inmqnormally used in lattice QCD calculations. It is argued on the basis of both diagrammatics and largeNcQCD that quenched QCD calculation of nucleon properties includes at least some of the virtual pion effects. It is also shown that hedgehog soliton models based on largeNic QCD, have, for a certain class of observables, the same type of nonanalyticity inm2&pgr;as conventional chiral perturbation theory but with coefficients which differ by numerical constants.These constants depend only on the angular momentum and isospin of the quantity. The reason for this difference is the role of the &Dgr; resonance which is treated differently in the two approaches. If the &Dgr; is included realistically, one finds important corrections to both the hedgehog models and chiral perturbation theory.

ISSN:0094-243X    

DOI:10.1063/1.42976

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A major goal in nuclear physics is to understand nuclear stability, structure, and reactions as a consequence of the interactions between nucleons. This requires modelling nuclei as collections of strongly interacting, and consequently, strongly correlated particles. We begin with the construction of realistic two‐body potential models constrained by nucleon‐nucleon elastic scattering data and deuteron properties, supplemented with consistent three‐body potentials and two‐body exchange currents. Nuclear ground‐state properties, such as the binding energy, one‐ and two‐body densities, and momentum distribution, are then calculated by variational methods based on correlated wave functions for a wide variety of nuclear systems, ranging from few‐body nuclei like3H and4He, to light closed‐shell nuclei like16O and and40Ca, to nuclear matter and neutron stars. Electromagnetic properties such as the elastic form factors, Coulomb sum, inelastic response, (e,e’p) reactions, as well as low‐energy electroweak capture reactions are also studied in this framework.

ISSN:0094-243X    

DOI:10.1063/1.42977

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

In this talk we review difficulties with the quasifree interpretation of the quasielastic (e,e’) peak. We present evidence from (e,e’p) coincidence experiments for the existence of two‐ and many‐body currents in the (e,e’) reaction process. This evidence includes details about the longitudinal and transverse response functions and their differences. Missing energy spectra that extend to very large missing energies are also discussed. Results of12C(e,e’d) are presented.

ISSN:0094-243X    

DOI:10.1063/1.42978

出版商:AIP    

年代:1992

数据来源: AIP