Electroproduction of the A isobar in C and Fe has been studied for incident electrons with energies between 0.6 and 1.6 GeV. A longitudinal-transverse decomposition of the inclusive cross section has been made for qj =0.1 (GeV/c) 2 . The residual longitudinal cross sections measured do not provide the additional strength needed above the quasifree region to satisfy the Coulomb sum rule. The transverse cross sections are in good agreement with data from photoabsorption.PACS numbers: 25.30.Fj Excitation of the A(3,3) resonance is the dominant feature of electromagnetic and hadronic interactions with nuclei in the region of energy transfer between pion threshold and 500 MeV. Because of strong interactions with other nucleons in the nuclear interior, one expects the A to be broadened and possibly shifted in energy when excited as a constituent nucleon in nuclear matter. The nuclear response in inelastic electron scattering has been studied 1 " 3 in the A region for energy transfers to the nucleus up to 550 MeV. To date, theoretical models for electron scattering have not given a satisfactory description of the data. 4 Although calculations which include nuclear-medium effects do predict a reduction of the peak cross section and a spreading of the A width, they do not account for the -34% enhancement in the integrated strength which O'Connell et al. 4 observe in the A region. It has been speculated that the origin of this enhancement may be a "quasideuteron electrodisintegration" mode of excitation 5,6 which is strongest in the region between the quasifree peak and the A peak in the nuclear response function.The experiment reported here extends high-energy (> 1.5 GeV) measurements to the medium-heavy nucleus, Fe, and includes for the first time a longitudinaltransverse decomposition of the inclusive cross section from pion threshold through the A region. Such a decomposition is vital to understanding the nuclear response to relatively large transfers of energy and momentum. The new data provide limits on the contributions of charge-dependent processes including the lond\ dndco ^M 1 9/f R L (q,(a) + qi + tan 2 -gitudinal tail of quasifree scattering into the A region. Because A excitation on the free nucleon results from a transverse yNA coupling, experimental sensitivity to A processes is increased in the transverse component of the inclusive cross section.The experiment was performed at the Stanford Linear Accelerator Laboratory with the NPAS (Nuclear Physics at SLAC) facility. Electron beams with energies of 653, 1300, 1500, and 1650 MeV were scattered from natural targets of C and Fe. Scattered electrons were observed in the 8-GeV/c spectrometer whose detector system includes a gas Cherenkov counter, ten planes of wire chambers, and a total-absorbing segmented leadglass shower detector array. The thicknesses of the carbon and iron targets were 324 and 122 mg/cm 2 , respectively. Observation of elastic scattering from a hydrogen target provided the absolute calibration of the spectrometer. Cross sections for the C ...
National Laboratory is part of the U.S. program to explore heavy-ion beam transport at a scale representative of the low-energy end of an induction linac driver for fusion energy production. The primary mission of this experiment is to investigate aperture fill factors acceptable for the transport of space-charge-dominated heavy-ion beams at high intensity (line charge density 0:2 C=m) over long pulse durations (4 s) in alternating gradient focusing lattices of electrostatic or magnetic quadrupoles. This experiment is testing transport issues resulting from nonlinear space-charge effects and collective modes, beam centroid alignment and steering, envelope matching, image charges and focusing field nonlinearities, halo, and electron and gas cloud effects. We present the results for a coasting 1 MeV K ion beam transported through ten electrostatic quadrupoles. The measurements cover two different fill factor studies (60% and 80% of the clear aperture radius) for which the transverse phase space of the beam was characterized in detail, along with beam energy measurements and the first halo measurements. Electrostatic quadrupole transport at high beam fill factor (80%) is achieved with acceptable emittance growth and beam loss, even though the initial beam distribution is not ideal (but the emittance is low) nor in thermal equilibrium. We achieved good envelope control, and rematching may only be needed every ten lattice periods (at 80% fill factor) in a longer lattice of similar design. We also show that understanding and controlling the time dependence of the envelope parameters is critical to achieving high fill factors, notably because of the injector and matching section dynamics.
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