Martyn H. Foss

Utilization of high energy, small emittance accelerators for ICF target experiments

Abstract High specific energy deposition can be achieved by using very small spot sizes if small-emittance particle beams are available, even if the kinetic energies are very high. This could allow some important target physics parameters to be determined in a foil target, such as energy deposition and equations-of-state at high temperatures. A discussion of one case, the FNAL proton accelerator, is given in detail. Since the minimum achievable spot size is critically important, focusing aberrations are a central issue. A longitudinal buncher in the ring is required; a rough cost estimate is given at aroung

The Proton Diagnostic Accelerator

5 M. For proton experiments giving target plasmas at a temperature above 10 eV it is necessary to obtain a longitudinal emittance at FNAL smaller than presently measured, but this is theoretically possible. If acceleration of comparable numbers of stripped heavy ions could also be accomplished, we estimate that target plasma temperature exceeding 200 eV could be achieved, and cylindrical implosion target might be studied.

The Design of the Zero Gradient Synchrotron Booster-II Lattice

The advantage of proton radiography for early cancer detection in soft human tissue has been demonstrated. 1-4 In order for this technique to become a practical medical tool for early detection of cancer, however, a proton source suitable for use in hospitals and clinics is required. An initial concept of such an accelerator has been discussed.5 It would meet the requirements considerably better than any existing accelerator and be simple, reliable, and economical.

Shaped Excitation Current for Synchrotron Magnets

A 500 MeV booster has been designed at the Argonne National Laboratory to increase the beam intensity from the Zero Gradient Synchrotron (ZGS). Many turns of H ions from the 50 MeV lirac will be injected into the booster and stripped to H so that the ring will contain the maximum useful charge in each booster pulse. Several booster pulses will be injected into the ZGS to form one ZGS pulse. This machine is now under construction.

A Transformer Septum Magnet

A 500 MeV synchrotron at Argonne National Laboratory (ANL) operates at 30 Hz with its beam spill locked to neutron choppers with a precision of ± 0.5 ¿s. The average beam will be increased by running the magnets at 45 Hz. Three 45 Hz circuits are discussed which differ greatly in overall cost and complexity. The first is a conventional 45 Hz sine wave circuit. The reduction in time for beam acceleration results in a costly increase in peak RF power. This problem is avoided in the other two circuits by making the field rise slowly and fall rapidly. The second circuit discussed is resonant at 45 Hz and 90 Hz. Exciting this circuit with a mixture of dc, 45 Hz, and 90 Hz can produce a magnetic field with the same maximum dB/dt as the present 30 Hz field. A third, and possibly least expensive, solution is a novel circuit which produces 30 Hz during acceleration and 90Hz when the magnets are reset. The RF requirements are, of course, identical to present requirements during acceleration. Circuit details are given.

Field Properties for a 4-GeV Microtron Sector Magnet

A pulsed transformer septum magnet is under development for the Intense Pulsed Neutron Source (IPNS-I), 500 MeV accelerator. The septum consists of a copper sheet and a steel sheet. The copper sheet is one side of the shorted single turn transformer secondary. The steel sheet, which is on the stray field side of the septum, is part of the transformer core. External support and cooling structures, as well as the septum itself, can be grounded, which simplifies the design. The design construction and operation will be discussed. The transformer primary is driven by a condenser discharge. A reverse discharge a few ms later recharges the condenser and demagnetizes the septum. Details will be discussed.

A 12.5 MHz Heavy Ion Linac for Ion Beam Fusion

The central magnetic field uniformity and field edge shapes have been investigated for a 609 metric ton sector magnet designed for the 4 GeV Electron Microtron (GEM) at Argonne National Laboratory. The effect of a Purcell filter on the central field uniformity was studied using the 2D magnetostatic computer program, TRIM. The effects on the shape of the edge field were studied for various geometries of endguard, pole tip shim, shield plate, pole edge shape, and coil. Both 2D and 3D programs were used for these latter studies and all results showed that the proposed design would produce acceptable field qualities.

A Conceptual Design for an Accelerator System for a Very High-Intensity Pulsed Neutron Source Using a Linear Induction Accelerator

Argonne National Laboratory (ANL) is currently developing the injector of a heavy ion beam driver for the inertial confinement fusion program. The first phase of the program is to accelerate about 20 mA of Xe/sup +1/ from a 1.5 MV preaccelerator 11.4 MeV in a low-beta RF linac. The first section of the linac utilizes a single harmonic buncher and independently-phased short linac resonators with a FODO magnetic quadrupole focusing lattice. These are followed by two double-stub Wideroee linacs. A layout of the linac up to 6.4 MeV is shown. The operating parameters of the low-beta linac are given. This paper gives details of the low-beta linac design and results of low power measurements on the first accelerating cavity.

A Rapid Cycling Synchrotron Magnet with Separate AC and DC Circuits

Several accelerator-based intense neutron sources have been constructed or designed by various laboratories around the world. All of these facilities have a common scheme of a linac and synchrotron or accumulator ring, and the system produces the proton energy of 500-1000 MeV. The average beam currents range from a few mA to a few hundred mA. The protons are then used to generate high flux neutrons by spallation out of heavy metal targets. In a synchrotron system, the protons are already bunched, and thus the pulse rate of the neutron beam is that of the repetition rate of the synchrotron. For an accumulator system, the pulse rate is determined by the extraction repetition rate of the accumulator. We have conceptually designed a new system that uses a linear induction accelerator which can be operated for an average beam current up to a few mA with a repetition rate up to 100 Hz. The details of the design will be given.

Pellet Fusion by High Energy Heavy Ions

In present rapid cycling synchrotron magnets ac and dc currents flow in the same coil to give the desired field. The circuit reactance is made zero at dc and the operating frequency by running the magnet in series with an external parallel resonant LC current. We propose to return the ac flux in a gap next to the synchrotron. The dc coil encloses the ac magnetic circuit and thus links no ac flux. A shorted turn between the dc coil and ac flux enhances the separation of the two circuits. Several interesting developments are possible. The dc coil could be a stable superconductor to save power. The ac flux return gap could be identical with the synchrotron gap and contain a second synchrotron. This would double the output of the system. If the return flux gap were used for a booster, the ac coil power could be greatly reduced or radiation hardening of the ac coil could be simplified.