This paper is an update on the development of the 500 mA per beam sixteen beam injector being built at LBL. An inductively graded Msrx bank provides the acceleration potential on the electrostatic column. A carbon arc source provides the pulsed current for the injector. We report recent results on extracted beam parameters, column performance, the generator performance, and system design changes. The carbon ion beam is diagnosed with Faraday cups and with a double slit omittance measurement systems. Controls for the final machine are also discussed. Abstract LBL's Heavy Ion Fusion Accelerator Research group has completed the engineering study of the Induction Linac Systems Experiment (ILSE). ILSE will address nearly all accelerator physics issues of a scaled heavy ion induction linac inertial fusion pellet driver. Designed as a series of subsystem experiments. ILSE will accelerate 16 parallel carbon ion beams from a 2 MeV injector presently under development to 10 MeV at one usee. This overview paper will present the physics and engineering requirements and describe conceptual design approaches for building ILSE. Major ILSE subsystems consist of electrostatic focusing quadrupole matching and accelerating sections, a 16 to 4 beam transverse combining section, a 4 beam magnetic focusing quadrupole accelerating section, a single beam 180 degree bend section, a drift compression section and a final focus and target chamber. These subsystems are the subject of accompanying papers. Also discussed are vacuum and alignment, diagnostics/data acquisition and controls, key conclusions and plans for further development. Abstract The design of a high current heavy ion induction linac driver for inertial confinement fusion is optimized by adjusting the acceleration units along the length of the accelerator to match the beam current energy, and pulse duration at any location. At the low energy end of the machine the optimum is a large number of electrostatically focused parallel beamlcts whereas at higher energies the optimum is a smaller number of magnetically focused beams. ILSE parallels this strategy by using 16 electrostatically focused bcamleis at the low end followed by 4 magnetically focused beams after beam combining.' total per be determined by the strength of the focusing voltages that can be used without breakdown and by the accuracy by which the focusing elements can be positioned. The maximum beam velocity tilt occurs in the electric focused portion. Abstract Sixteen intense parallel ion beams are to be transversely combined into four by dispersionless double bends. Emitiance growth due to electrostatic energy redistribution and to the geometry is evaluated. Most bending elements are electric, and alternate with AG electrostatic quadrupoles similar to those upstream. The final elements me magnetic, combining focusing and "unbending". Electrode shapes and pulsed-current arrays (having very small clearances), and mechanical and electric features of the combiner, and described. Abstract The Induction Unac System Experiment (ILSE)* 1 - 3 ) includes a 180' bend system, drift compression line and a final focus, which test the analogous features of a heavy ion driver for inertia! fusion. These components are novel in their transport of a space-charge-doirdnate i ion beam with large head-to-tail velocity till. Their conceptual design is presented, including calculations of the beam envelope, momentum dispersion, and engineering design of magnets, vacuum system, diagnostics, alignment, and support. Present concepts for a heavy ion fusion driver require the ability to bend high current, high energy heavy ion beams in order to orient them to a reactor configuration. This requirement is complicated by a variation of ion velocities within a single beam on the order of 5%. ILSE's 180' bend section, located immediately following the magnetic focus acceleration section, is designed to deflect a single 10-MeV, 3.8-A carbon-ion beam with a 7.7% velocity tilt through a bend with mean radius of 4.0 meters. This bend section also functions as the initial portion of ILSE's drift- compression section. The objective of the bend section experiment is the study of high current ion beam bending with the goal of minimum beam loss and eirdttance growth. Abstract The Symposium hosted by CSI attracted about 130 participants from 12 countries. Progress in developments for high-current low-emiltance heavy ion beams in both rf linacs and induction linacf has beem reported. Significant current amplification in a proof-of-principle multiple-beam induction linac was described. Experimental results from France and Germany show enhanced energy deposition by low-energy heavy ions in hot dense plasmas. The GSI heavy ion synchrotron (SIS) and the experimental storage ring (ESR) are under construction; when completed, the beams will be used for experiments to study hot dense plasma phenomena. on two fronts — ihe physics of high energy density by heavy ion beams and the accelerator physics issues in linac/storage ring systems. While initial experiments on the

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A novel acceleration system for the (simultaneous) application of higher or multiple-harmonics in proton or heavy-ion synchrotrons has been developed for various uses, e.g. the passage of the transition point, applying stochastic cooling on a bunched beam, or for other longitudinal beam manipulations as bunch stretching or compression. The system consists of a coaxial cavity filled with the ferritic amorphous metal VITROVAC of VAC, Hanau, in lieu of the conventional ceramic materials. In its current configuration, it can support a frequency range of 0.2-8 MHz. Amplifier modules for both 10 and 50 kW are available to produce gap voltages in the kV-range. By means of digital synthesis techniques, virtually arbitrary voltage waveforms with harmonic admixtures up to fourth order can routinely be generated at the cavity gap. As illuminating examples we, achieved at high precision a flat-top wave form suitable, e.g. for the transition crossing, a linearized force law at the center of the bucket, and a fourth-order flattened bucket for bunched-beam cooling. The compact cavity system should be well suited for any synchrotron operating in this frequency range. Actual installation of such a system is projected for the medium energy device COSY Julich, and the therapy-oriented ring TERA.

The ferrite loaded, tunable reentrant-coaxial symmetric (2×λ/4) accelerator cavity for the cooler synchrotron COSY is of the SATURNE type. For h=1, frequencies range from 450 kHz at injection to a maximum of 1.6 MHz, with a maximum rf power level of 50 kW. We have determined the cavity circuit properties both at low signal levels with standard rf test equipment, and at operation conditions, depending on frequency and power level. Moreover, the acceleration system was tested for its suitability to pass through gamma transition. For this end, a sudden phase jump of 180° was imposed at the input of the amplifier chain by means of the digital frequency synthesizer developed for COSY. At higher frequencies, a loss of Q was observed, partly aiding the transition crossing speed. Finally, a simple replacement circuit, incorporating the measured quantities, is used to model the cavity

Since the advent of VLSI circuits capable of data rates in excess of 30 MWords/s, real time digital RF synthesis has become an interesting and viable avenue to be used with accelerators. This technique builds up RF signals from a real-time sequence of digital words with minimum use of analog components. With digital RF, hitherto not achieved agility, precision, and reproducibility for frequency and phase are now possible. This permits optimum acceleration ramp functions, subject to any desired constraints in longitudinal phase space, as given phase or voltage or acceptance, or yet another bucket quantity. Since phase fidelity is crucial with accelerator applications, a high degree of over-sampling is mandatory, posing the only actual limitation to these new techniques. However, with clock rates of more than 1 GHz, today's component technology limits the RF carrier to some 10 to about 100 MHz, depending on which signal-to-noise ratio is acceptable. This range can further be extended by means of analog up-conversion. A number of digital RF techniques have been developed at the cooler synchrotron COSY, e.g. for RF acceleration and ultraslow extraction, and were made available also for the acceleration with TSR, Heidelberg. Further possible applications are being explored

Beam current bench tests and simulations, e.g. with beam monitors, are of interest for diagnostic purposes. For highly-relativistic tests, the common coaxial wire method may be used. In contrast, a configuration for non-relativistic beams was devised for transverse impedance measurements. We have combined the two approaches to permit both frequency and time domain low-beta bench tests of the line charge, and of the longitudinal beam impedance. The basic structure is of coaxial 50 /spl Omega/ geometry, where the outer diameter matches the beam-pipe diameter of COSY, while the inner conductor carries, both around the azimuth and along the axis, suitable pin-and-loop arrays for imposing electric and magnetic fields, respectively. The arrays ensure nearly azimuthal (coaxial) symmetry, and are wired via delay lines such that axially varying field patterns may be generated, permitting the simulation of a broad beta range. We use standard measurement techniques with a network analyzer at a frequency range from 500 kHz up to 100 MHz. A calibration procedure, measuring field pick-up via coupling loops and pins installed in the outer beam pipe wall, ensures the correct |E|/|B| ratio.<>

Since the advent of VLSI circuits capable of data rates in excess of 30 MWords/s, real time digital rf synthesis has be- come an interesting and viable avenue to be used with accele- rators. This technique builds up rf signals from a real-time sequence of digital words with minimum use of analog com- poncnts. With digital rf, hitherto not achieved agility, preci- sion, and reproducibility for frequency and phase are now pos- sible. This permits optimum acceleration ramp functions, subject to any desired constraints in longitudinal phase space, as given phase or voltage or acceptance, or yet another bucket quantity. Since phase fidelity is crucial with accelerator appli- cations, a high degree of over-sampling is mandatory, posing the only actual limitation to these new techniques. However, with clock rates of more than 1 GHz, today's component tcch- nology limits the rf carrier to some ten to about 100 MHz, depending on which signal-to-noise ratio is acceptable. This range can further be extended by means of analog up-conver- sion. A number of digital rf techniques have been devclopcd at the Cooler SYnchrotron COSY, e.g. for rf acceleration and ultraslow extraction, and were made available also for the ac- celeration with TSR, Heidelberg. Further possible applica- tions are being explored. 1. INTR~DUCTI~N

The Cooler Synchrotron COSY is intended to operate its ferrite-loaded radio frequency (I-r) acceleration station operating at fundamental (h=l) frequencies ranging from 0.4 to 1.6 MHz. A fully digital vector controller with high temporal and value resolution is under development to synthesize the low level acceleration rf voltage waveform. Its phase angle is set both externally, and from a beam-to-cavity phase locking loop (PLL). The PLL consists of only digital components, with analog-to-digital converters (ADC) at beam monitor and cavity, and a digital-to-analog converter (DAC) for output to the amplifier chain. Locking range and control bandwidth is a full 27r, and > SOkHz, respectively, to allow for programmed phase jumps at the y-transition. Resolution of 12 to 16 Bit and oversampling at up to 25 MSPS are realized by recent video digital control and digital signal processing (DSP) technology. The synthesizer part, at first for use without beam-phase feedback, has been completed and used for fit tests on the acceleration station. Major components for the PLL upgrade have so far been tested under operations conditions, and the corresponding circuitry is being finalized. 1. INTR~IXKTI~N

The cooler synchrotron COSY will accelerate protons from 40 Me up to 2.5 GeV. It is the goal of this machine to use the beam of maximum brightness for internal target experiments as well as for external experiments. The tool for the extraction of a low emittance beam is the ultra slow extraction scheme. The third-order extraction resonances at Q/sub x/=10/3, 11/3, respectively, will be driven chromatically. A spill rate of longer than 5 s will be controlled by noise generators acting in the momentum phase space. The dynamic acceptance during extraction will be controlled by 11 families of sextupoles. It is expected to extract a beam with a horizontal emittance of less than 1 pi and a momentum spread of less than 0.02%.<>

Summary Form only given, as follows. The multiple-beam accelerator MBE-4 is a device for research toward a heavy ion driver for inertial confinement fusion based on the induction linac concept. Its main goal is proof of the principle of current amplification by acceleration and controlled self-similar beam pulse compression. Into the 16-m long electrostatic alternate-gradient focusing lattice four beams are injected. Each carries an initial current of 10 mA of Cs/sup +/ ions from a Marx-driven diode at 200 keV. The current amplification is up to ninefold, with a final beam energy in excess of 800 keV in the middle of the current pulse. Available diagnostics include transverse double-slit emittance and position measuring devices; current-sensing Faraday cups; and electrostatic energy analysis. Diagnostic access is possible along the entire device at a number of stations and is fully computer controlled. The longitudinal and transverse properties of the 10-mA beams with and without acceleration are being studied. The diagnosis of the transport of a 100- mu A pencil beam, 1.5 mm in diameter, through an accelerating channel of a 5.7-cm diameter has begun. This beam has been used to determine the zero-current phase advance for various beam and machine parameters and to address some mechanical alignment issues as well.<>

The multiple-beam accelerator MBE-4 is a device for research toward a heavy-ion driver for inertial confinement fusion, based on the induction linac co

We report on the implementation of a second schedule of acceleration and current amplification in MBE-4. Control of the beam current within the bunch is improved over that in the first schedule by the addition of several small amplitude induction pulsers to compensate for acceleration errors and to control the ends of the bunch. Measurements of the longitudinal and transverse emittance are presented. 5 refs., 3 figs., 1 tab.

A small-scale experimental accelerator called MBE-4 has been constructed to demonstrate the principle of a current-amplifying induction linac for multiple beams of heavy ions. Four beams of Cs{sup 1+}, initially at 200 keV and each with a current of 10 mA have been accelerated and amplified to a kinetic energy of 700 keV and currents of 90 mA apiece. Transverse focusing is achieved by means of electrostatic quadrupoles; longitudinally the current is amplified and the beam bunch is held together against the space charge forces by special time-dependent accelerating fields. We report on the methods developed for designing and implementing the accelerating pulses and on measurements of the transverse and longitudinal emittance of the accelerated beams. Current fluctuations and the longitudinal emittance are initially almost zero and increase as acceleration errors are accumulated. We discuss the final longitudinal emittance and the current fluctuations in the experiment in terms of their acceptability for a large heavy-ion-fusion driver. 17 refs., 23 figs., 3 tabs.

Experiments and theory are used to investigate the radial distribution of current at the cathode of a cylindrically symmetric, planar magnetron discharge. We have developed a simple model of the distribution of incident ions at the cathode, in the form of an integral equation. Energetic electrons, produced by secondary electron emission when ions strike the cathode, are accelerated into the discharge through a thin sheath. The Hamiltonian motion of the energetic electrons in the magnetic field determines the birthplace of discharge ions, and thus, the distribution of ion current density at the cathode. The radial current distribution has been measured for various magnetic fields using a radially staggered array of sixteen 1-mm-diam current probes imbedded in a 9-in.-diam cathode. In agreement with the model, the current distribution is peaked at the radius at which the magnetic field is tangent to the cathode plate, and the width of the distribution scales as the square root of the energetic electron Larmor radius.

In the framework of a generalized fully anisotropic Bardeen-Cooper-Schrieffer-type quantum theory, the low-temperature, low-field coherence-length tensor is derived from first principles. Anisotropy of the Fermi surface, the gap parameter, and the energy band structure in the effective-mass approximation is included. For lattice parameters and effective-mass ratios suitable for the high-${T}_{c}$ superconductors the coherence lengths along the principal axes show a marked anisotropy exceeding 20:1. The coherence length along the $c$ axis is found to be of the order of the lattice spacing $c$, suggesting marginal two dimensionality.

An electrostatic potential well and mirror-trapped hot electrons are created by high power (250 kW), short pulse (3 μsec) electron cyclotron resonance heating (ECRH) of a plasma in one magnetic mirror cell of a multiple mirror experiment. The creation and subsequent decay of the potential well is measured by an electron beam, time-of-flight diagnostic. Typically, the barrier rises to −40 V just after ECRH and decays within 100 μsec. A numerical model of the barrier evolution is developed, and the numerical results along with the experimental observations are presented. Both the numerical results and the experimental observations indicate a correlation between the degree of heating (diamagnetic loop voltage output) and the longevity of the barrier. It is shown that the decay of the barrier is determined mainly by the hot-electron escape rate and the hot-electron-neutral ionization rate, rather than by trapping of the passing ions.