Superconducting Heavy-ion Linac Research Articles

NSCL–Ongoing activities and future perspectives

Michigan State University’s NSCL (National Superconducting Cyclotron Laboratory) is funded by the US National Science Foundation to operate the premier rare isotope user facility in the US. Beams of rare isotopes at NSCL are produced via projectile fragmentation or fission and separated in-flight. The current NSCL facility capabilities and main research directions will be outlined. The laboratory is currently expanding its capabilities by building an efficient gas-stopping and reacceleration capability initially up to 3.2 MeV per nucleon. For the longer term future, NSCL is proposing to replace the existing superconducting cyclotrons with a high-intensity, 200 MeV per nucleon superconducting heavy-ion linac.

Current progress of nuclear astrophysics study and BRNBF at CIAE

A secondary beam line (GIRAFFE) at the Beijing tandem accelerator lab was constructed for yielding low energy secondary beams. The current progress on the study of nuclear astrophysics and nuclear structure is presented. Up to now, we have carried out measurement of 7Be(d,n) 8B, 11C(d,n) 12N, 8Li(d,n) 9Be and 6He(p,n) 6Li reactions. The proposed Beijing radioactive nuclear beam facility and its current R&D progress are briefly introduced. This facility is based on the exist HI-13 tandem accelerator. A proton cyclotron will be built to provide 100 MeV 200 μA proton beam, together with an isotope separator on line system and a super-conducting heavy ion LINAC. By this facility, intensity of order of 10 9 pps radioactive nuclear beams for mass up to A=120 will be produced.

Development of a medium-energy superconducting heavy-ion linac

The Rare Isotope Accelerator (RIA) facility project includes a cw 1.4 GeV driver linac and a 100 MV postaccelerator both based on superconducting (SC) cavities operating at frequencies from 48 to 805 MHz. In these linacs more than 99% of the total voltage is provided by SC cavities. An initial acceleration is provided by room temperature radio frequency quadrupoles. The driver linac is designed for acceleration of any ion species, from protons up to 900 MeV to uranium up to 400 MeV/u. The novel feature of the driver linac is an acceleration of multiple charge-state heavy-ion beams in order to achieve 400 kW beam power. This paper presents design features of a medium-energy SC heavy-ion linac taking the RIA driver linac as an example. The dynamics of single and multiple charge-state beams are detailed, including the effects of possible errors in rf field parameters and misalignments of transverse focusing elements. The important design considerations of such linac are presented. Several new conceptual solutions in beam dynamics in SC accelerating structures for heavy-ion applications are discussed.

The Canadian Penning Trap Spectrometer at Argonne

The Canadian Penning Trap (CPT) mass spectrometer is a device used for high-precision mass measurements on short-lived isotopes. It is located at the ATLAS superconducting heavy-ion linac facility where a novel injection system, the RF gas cooler, allows fast reaction products to be decelerated, thermalized and bunched for rapid and efficient injection into the CPT. The CPT spectrometer and its injection system will be described in detail and its unique capabilities with respect to its initial physics program, concentrating on isotopes around the N=Z line with particular emphasis on isotopes of interest to low-energy tests of the electroweak interaction and the rp-process, will be highlighted.

ATLAS cryogenic system

The Argonne Tandem Linac-Accelerating System (ATLAS) superconducting heavy-ion linac is cooled by forced flow of liquid helium supplied by a 300- and a 180-W refrigerator. Outgoing flow is recondensed between heat loads by heat exchange with return flow. Control valves limit line pressure by diverting flow to return stream heat exchangers. Heater controls can maintain constant pressure or level in two helium Dewars, or constant flow for increasing or decreasing liquid level. A power meter reads excess refrigeration capacity. A stable, constant pressure liquid-nitrogen system utilizes flash loss cold gas in the refrigerators, and supplies stable low-pressure nitrogen for general cooling and shielding.

A Superconducting Heavy Ion Injector Linac

A conceptual design for a very low velocity (.007 < v/c < .07) superconducting heavy-ion linac is reviewed. This type of linac may have significant cost and performance advantages over room-temperature linacs, at least for applications requiring modest beam currents. Some general features of the design of very-low velocity superconducting accelerating structures are discussed and a design for a 48.5 MHz, v/c = .009 structure, together with the status of a niobium prototype, is discussed in detail. Preliminary results of a beam dynamics study indicate that the low velocity linac may be able to produce heavy-ion beams with time-energy spreads of a few KeV-nsec.

Bunching System for the Stony Brook Tandem Linac Heavy-Ion Accelerator

A versatile high-efficiency bunching system which is used to couple the Stony Brook 9 MV tandem Van de Graaff to the recently completed superconducting heavy-ion LINAC is described. The major elements of the system are: a pre-tandem double-drift harmonic buncher working at 9.4 and 18.8 MHz, a post-tandem sine-wave beam chopper at 4.7 MHz, a pre-LINAC superconducting double-drift harmonic buncher at 150 and 300 MHz and a high voltage DC-coupled single pulse selecting beam switch.

Superconducting heavy-ion linac at Stony Brook

The world's first university-based superconducting heavy-ion linac was dedicated in April at the Stony Brook campus of the State University of New York. By adding a ten-meter-long superconducting booster to Stony Brook's fifteen-year-old tandem Van de Graaff accelerator at a cost of $4.6 million, the Stony Brook group has produced a 20-megavolt linear accelerator capable of accelerating ions with mass numbers from 16 to about 100. The maximum energy per nucleon, 8.3 MeV, is attained for nickel, in the middle of this mass range. The only other comparable superconducting linac currently in operation is at Argonne National Laboratory.

Research at the argonne linac

A superconducting heavy-ion linac, predecessor and part of the national facility ATLAS funded this year, has been operational at Argonne for approximately three years. Even though the last resonator was only mounted a few weeks ago, the modular design of independently phased resonators has allowed partial operation and an experimental program over that period, with continually increasing capability in ion-beam species and energy. This is a short report on some of the research activities which, in short, are concerned with the various aspects of the relationships between heavy-ion-induced reactions and nuclear structure. Major interests are the structure of nuclei at high excitation, far from stability or in states of high spin near the yrast line.

A 145 MHz niobium split-ring resonator for particle velocities from 0.12 to 0.23 c

A niobium split ring resonator has been designed with an optimum particle velocity β = v/c = 0.16. This type of resonator will be used to extend the Argonne superconducting heavy-ion linac. The peak surface electric field in the resonator is 3.9 times the effective accelerating field, a value 20% lower than for previously developed split-ring resonators. A prototype niobium resonator has been completed. Results of performance tests are discussed.

The Superconducting Heavy-Ion Linac at Argonne

The design, status, and performance of the first operating superconducting heavy-ion accelerator, a linac used to boost the energies of beams from a 9-MV tandem, is summarized. When completed in 1981, the linac will consist of 24 independently-phased splitring niobium resonators operating at 97 MHz. This linac is designed to provide 29 MV of acceleration. Because of the modular character of the system, the linac has been operable and useful since mid-1978, when a beam was accelerated through 2 units and the first nuclear-physics experiments were performed. Now, 16 resonators are in use, and a beam has been accelerated for ~ 6000 hr. Resonator performance has been remarkably stable, in spite of vacuum accidents, and the linac as a whole operates reliably without operators in attendance during nights and weekends. The ease and speed with which the beam energy can be changed is proving to be unexpectedly valuable to users.

Status of the Stony Brook Superconducting Heavy-Ion Linac

We describe the present status of the State University of New York at Stony Brook Superconducting Heavy-Ion LINAC (SUNYLAC). The LINAC will extend at very modest cost the capabilities of the existing FN tandem Van de Graaff into the energy range 5-10 MeV/A for light heavy-ions from oxygen to bromine. The active elements are 43 lead-plated copper superconducting resonators of the split-loop type optimized for either velocity ß=v/c=0.055 or ß=0.10. Phase and amplitude of each resonator is independently set through RF-feedback controllers interfaced to an overall computer control system. Full scale construction work began in July, 1979 following the in-beam demonstration of a prototype LINAC module containing 4 low-ß resonators, and the majority of the installation work on the beam transport and refrigeration systems was completed in the summer of 1980. The project is now well into its final assembly and testing phase, with the completion of assembly scheduled in early 1982. We describe details of the design of key elements of the LINAC and the initial operating experience with the injection beam path, helium refrigerator and first production accelerator module. The progress of a continuing program aimed at optimizing crucial aspects of the LINAC is also reviewed.

Control System for the Stony Brook Superconducting Heavy-Ion Linac

The control system for the Stony Brook Superconducting Heavy-Ion LINAC is described. Familiar response characteristics and convenient operation have been given high priority in the design. A star network of 9 LSI-11 microcomputers forms the basis of the system which in addition comprises a PDP 11/34 minicomputer, one 6502 microprocessor-based RF controller for each of 43 resonators, and several I/O devices such as graphics display and reassignable control knobs.

Status of the Stony Brook Superconducting Heavy-Ion Linac

We describe the present status of the State University of New York at Stony Brook Superconducting Heavy-Ion LINAC (SUNYLAC). The LINAC will extend at very modest cost the capabilities of the existing FN tandem Van de Graaff into the energy range 5-10 MeV/A for light heavy-ions from oxygen to bromine. The active elements are 43 lead-plated copper superconducting resonators of the split-loop type optimized for either velocity s=v/c=0.055 or s=0.10. Phase and amplitude of each resonator is independently set through RF-feedback controllers interfaced to an overall computer control system. Full scale construction work began in July, 1979 following the in-beam demonstration of a prototype LINAC module containing 4 low-s resonators, and the majority of the installation work on the beam transport and refrigeration systems was completed in the summer of 1980. The project is now well into its final assembly and testing phase, with the completion of assembly scheduled in early 1982. We describe details of the design of key elements of the LINAC and the initial operating experience with the injection beam path, helium refrigerator and first production accelerator module. The progress of a continuing program aimed at optimizing crucial aspects of the LINAC is also reviewed.

Initial Operation of the Argonne Superconducting Heavy-Ion Linac

Initial operation and recent development of the Argonne superconducting heavy-ion linac are discussed. The linac has been developed in order to demonstrate a cost-effective means of extending the performance of electrostatic tandem accelerators. The results of beam acceleration tests which began in June '78 are described. At present 7 of a planned array of 22 resonators are operating on-line, and the linac system provides an effective accelerating potential of 7.5 MV. Although some technical problems remain, the level of performance and reliability is sufficient that appreciable beam time is becoming available to users.

Status Report on Stanford's Superconducting Heavy Ion Linac Project

Two superconducting niobium reentrant cavities resonating at 430 MHz were phase locked to within ± 0.05 rad. A quarter-wavelength resonator, operated at 215 MHz to chop the ion beam at the frequency of the accelerating cavities, was built and tested. Beam chops of less than 185 ps FWHM were obtained from a continuous 2 MeV proton beam. A double cavity structure, having the same separation between cavities and the same design details as planned for a many-cavity accelerator section, has been constructed. An assembly of two such double cavities, with associated tuners and electronics for each of the four cavities, is currently under test.

Split Ring Resonator for the Argonne Superconducting Heavy Ion Booster

A split-ring resonator for use in the ANL superconducting heavy-ion linac was constructed and is being tested. The electromagnetic characteristics of the 98-MHz device are the same as the unit described earlier, but the housing is formed of a new material consisting of niobium sheet explosively bonded to copper. The niobium provides the superconducting path and the copper conducts heat to a small area cooled by liquid helium. This arrangement greatly simplified the cryogenic system. Fabrication of the housing was relatively simple, with the result that costs have been reduced substantially. The mechanical stability of the resonator and the performance of the demountable superconducting joints are significantly better than for the earlier unit.