R. L. Martin

Initial Test of a Proton Radiographic System

Protons have a well defined range in matter. A detector, therefore, placed near the end of range of a monoenergetic proton beam becomes a very sensitive measure of changes in the mass of material which the beam has traversed. This property of protons can be exploited in a variety of ways to make radiographs of solid objects. The experimental radiography system we have built to use with the 200 MeV booster synchrotron of the Zero Gradient Synchrotron (ZGS) is described. In addition, there is a brief description of a more elegant system which would operate with a suitable source such as the proton diagnostic accelerator proposed by R. Martin.

The Argonne Zero Gradient Synchrotron (ZGS) Booster

The former Cornell 2.2-GeV electron synchrotron operating at 30 Hz will be used as a rapid-cycling booster for injecting protons at 200 MeV into the ZGS to increase the space charge limited intensity of the ZGS. Negative hydrogen ions of 50 MeV will be injected into the booster with the electrons stripped at injection for acceleration of protons. The reasons for using this type of injection along with the history and status of the program are discussed.

A High Intensity 1.5 Megavolt Heavy Ion Preaccelerator for Ion Beam Fusion

A preaccelerator is being developed at Argonne National Laboratory (ANL) in a program to demonstrate the accelerator technology which will be needed for power plants utilizing inertial-confinement fusion (ICF). The preaccelerator has been constructed and is now undergoing performance tests with the initial objective of achieving pulsed 30 mA beams of 1.5 MeV Xe+1. The design, construction, and initial performance of the preaccelerator are described.

The Ion Beam Compressor for Pellet Fusion

Intense ion beams of short duration can be created by charge exchange injection into a number of small, high field storage rings. If the beams are extracted and focussed from many directions simultaneously onto a DT pellet, a beam of protons or a particles of 15,000-30,000 A for a duration of 1-2 ns can result. Such beams have possibilities for compressing and heating to fusion temperatures submillimeter pellets of a DT mixture. The potential of this method is discussed.

Molecular Ion Photodissociation Injection

A new technique for injecting an ion beam into a storage ring is presented. The idea arose in conection with high energy ion beam fusion where a large degree of transverse stacking in both planes would otherwise be necessary. The method involves accelerating a molecular ion such as HI+ but storing the atcnic ion I+ by photodissociating the molecule at injection. The irreversibility of the reaction ¿+HI+¿Ho+I+ renders irrelevant Liouvilles theorem, which, with standard injection, would prevent new beam fran being injected into the same space as already circulating beam. Xenon flashlamp and ruby laser system for acccxplishing mlecular ion dissociation (MID) are described.

The Proton Diagnostic Accelerator

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.

Emittance limitations in heavy ion fusion

Abstract The number of parameter choices that effect the required emittance (both transverse and longitudinal) at each stage of the heavy ion beam acceleration and delivery system for inertial confinement fusion is very large. Some choices which appear technically straightforward are compounded by more involved questions of cost optimization which are beyond the scope of this paper. A study is made of the factors which affect the transverse emittance requirements of a system to produce 5 MJ at 200 TW of 200 Hg ions beginning with space charge forces at the target and working backward through the final focusing system and the beam transport system to the accumulator rings. The sensitivity of emittance limitations to the ratio of ion energy to charge state, and to the convergence half-angle from the final focusing system to the target, is demonstrated. Arguments are presented that convergence angles of 30 mrad, or larger, can be practical and that distances from the final quadrupole to the target of 3 m or less should not be excluded, particularly for the development programs. The accumulator rings act as an emittance filter and allow a tradeoff between transverse and longitudinal emittance. Therefore, it is not possible to define the emittance requirements of the linac injector without athorough analysis of longitudinal emittance limitations as well as some additional factors, not included here, which affect transverse emittance.

A Low Cost/Low Intensity 50 MeV Proton Irradiation Facility

Protons have been proposed as one of the most useful particles for radiation therapy, but have found limited use due to the cost and scarcity of medium energy proton accelerators. However the highly successful program on the Harvard Cyclotron has increased interest in expanding the number of treatment Facilities. In order to demonstrate that high intensity proton accelerators are not required and to gain experience with treating patients using protons, a low cost and low intensity source of of 50 MeV protons was developed at Argonne. Although the beam penetration is limited to 22 mm, the beam is capable of treating a major fraction of the ocular melanoma tumors treated at the Harvard Cyclotron. This beam operates parasitically with the Rapid Cycling Synchrotron at Argonne using a source of 50 MeV H° atoms which are produced by stripping in the gas of the 50 MeV H- linear accelerator. A stripping fraction of about 3-5 × 10-5 is observed and yields a 0.4 namp beam of protons. Results on the properties and operation of this parasitic beam are presented.

Heavy ion accelerators and storage rings for pellet fusion reactors

Abstract Heavy ion accelerators and storage rings in the multi-GeV energy regime can be utilized for inertial-confinement fusion. A discussion is presented of design parameters for some systems, based on existing accelerator technology, capable of delivering beams of order 100 terawatt to a pellet of a few millimeters in diameter. A specific conceptual design for an 8 GeV system, using a beam of iodine ions, is described in some detail.

Longitudinal and Transverse Space Charge Limitations on Transport of Maximum Power Beams

The maximum transportable beam power is a critical issue in selecting the most favorable approach to generating ignition pulses for inertial fusion with high energy accelerators. Maschke and Courant1 have put forward expressions for the limits on transport power for quadrupole and solenoidal channels. We have included in a more general way the self consistent effect of space charge defocusing on the power limit. The results show that no limits on transmitted power exist in principal. In general, quadrupole transport magnets appear superior to solenoids except for transport of very low energy and highly charged particles. Longitudinal space charge effects are very significant for transport of intense beams.