In this paper we discuss recent work to further improve our superconducting (SC) ADS driver linac design. Our design assumes use of the 6.7-MeV LEDA RFQ as an injector to the SC driver linac. We have examined the feasibility of accelerating a 20-mA CW beam to 600 MeV using only 350-MHz SC multi-spoke resonator cavities operating at 4 K. Replacing the 2 K, 700-MHz SC elliptical cavity sections with spoke resonators has several advantages, including reduced cryo-plant operating cost and an improved real-estate accelerating gradient due to the longer active lengths of the 350-MHz cavities. We discuss the details of the new design layout and beam dynamics simulations, including effects due to operational and alignment errors. Preliminary cavity modelling results for the proposed five-gap spoke resonators are also discussed. This accelerator design would be appropriate as a driver linac for applications such as waste transmutation, fusion materials testing, etc.

The SNS Linac is required to provide a pulsed 1-GeV 1-mA-average beam of H{sup {minus}} ions to a storage/compressor ring which then delivers it to a neutron production target with high reliability and availability. Nominal rep rate is 60 Hz with a linac pulse length of 1 ms. The entire Linac is required to support a 2-mA operation; thus a facility upgrade to 2 MW merely requires doubling the injected beam current and providing the additional needed rf power. (The design basis for the Linac upgrade to a 4-MW level is a 20-MeV beam funnel.) In order to permit hands-on maintenance, the beam losses in the Linac must be less than 1 nA/m at 1 GeV. Based primarily on value engineering considerations relating to Linac support stands, ease of the placement, alignment, and possible replacements of the quadrupole magnets and diagnostic components, and other constraints such as adequate gaps between the accelerating segments for electromagnetic quadrupoles and diagnostics, the authors propose a revised Linac configuration. It should be noted that this revised configurations represents only a small change; the basic Linac architecture consisting of the three types of accelerating structures, DTL, CCDTL, and CCL, has not changed. In this brief note the authors present the overall physics and engineering design considerations and the revised linac configuration.

A 2.5 MeV, 428 MHz radio frequency quadrupole (RFQ) linac has been designed and fabricated by the Los Alamos National Laboratory and GAR Electroforming for the Superconducting Super Collider Laboratory. This device is a two segment accelerator fabricated from tellurium-copper (CDA14500) vane/cavity quadrants which are joined by electroforming. The structure incorporates an integral vacuum jacket and has no longitudinal rf or mechanical joints. The SSC RFQ linac is an extension of the design of the 1.0 MeV RFQ which was successfully flown on the BEAR Project.

The design of the radio frequency quadrupole accelerator for the Superconducting Super Collider (SSC) is presented. The RFQ, which accepts the beam from the ion source through the low energy beam transport line, is designed to accelerate an H/sup -/ beam from 35 keV to 2.5 MeV. Key design considerations and the final design parameters for the RFQ are presented. Results of simulation studies with and without misaligned input beam are also discussed.<>

The preliminary design of the 600-MeV H/sup -/ linac for the Superconducting Super Collider (SSC) injector is described. The linac must provide a 25-mA beam during 7-35 mu s macropulses at 10 Hz within injection bursts. Normalized transverse emittances of less than 0.4 pi mm-mrad (RMS) are required for injection into the low Energy Booster (LEB) synchrotron. Cost, ease of commissioning, and operational reliability are important considerations. The linac will consist of an H/sup -/ source with electrostatic low-energy beam transport (LEBT), a 2.5-MeV radiofrequency quadrupole (RFQ) accelerator, a 70-MeV drift-tube linac (DTL), and 530 MeV of coupled-cavity linac (CCL). The RFQ and DTL operate at 428 MHz and the CCL operates at 1284 MHz. A modest total length of 143 m results from the tradeoff between cost optimization and reliability.< >

Recent advances in high-current linear accelerator technology have considerably increased the attractiveness of a deuterium-lithium high-energy neutron source for fusion materials and technology testing. This paper describes a new Los Alamos conceptual design for a deuteron accelerator aimed at meeting near-term flux requirements of an International Fusion Materials Irradiation Facility. The new neutron-source driver concept is based on the idea of multiple accelerator modules, with each module consisting of two 125-mA, 175-MHz radio-frequency quadrupoles funneling 3-MeV cw deuteron beams into a 35-MeV, 250-mA, 350-MHz drift-tube linac.

A new approach to a deuterium-lithium neutron source aimed at meeting the near-term requirements of a high-flux high-energy International Fusion Materials Irradiation Facility (IFMIF) is discussed. The concept employs multiple accelerator modules providing deuteron beams to two liquid-lithium jet targets oriented at right angles. This beam-target geometry provides much larger test volumes than can be attained with a single beam and target and produces significant regions of low neutron-flux gradient. A preliminary beam-dynamics design has been obtained for a 250-mA reference accelerator module. Neutron-flux levels and irradiation volumes were calculated for a neutron source incorporating two such modules, and interaction of the beam with the lithium jet was studied using a thermal-hydraulic computer simulation. Cost estimates are provided for a range of beam currents, and a possible facility staging sequence is suggested.< >

A collaborative study by Los Alamos and Brookhaven National Laboratories investigating a facility to produce tritium for the USA's defense needs indicates that a 1.6-GeV, 250-mA proton accelerator is required. A reference design of this accelerator starts with two parallel 125-keV injectors feeding the 350-MHz radio-frequency quadrupoles that funnel at 2.5-MeV into a 700-MHz drift-tube linac. This then injects at 100 MeV into a 1400-MHz side-coupled linac. The accelerator will cost about $1.2B and require 746 MW of electricity. The accelerator components, the control and diagnostics, and the accelerator facility are discussed, and design considerations are presented.< >

Advances in high-current linear-accelerator technology since the design of the Fusion Materials Irradiation Test (FMIT) Facility have increased the attractiveness of a deuteriumlithium neutron source for fusion materials and technology testing. This paper discusses the conceptual design of such a source that is aimed at meeting the near-term requirements of a high-flux high-energy International Fusion Materials Irradiation Facility (IFMIF). The concept employs multiple accelerator modules providing deuteron beams to two liquid-lithium jet targets oriented at right angles. This beam/target geometry provides much larger test volumes than can be attained with a single beam and target and produces significant regions of low neutron-flux gradient. A preliminary beam-dynamics design has been obtained for a 250-mA reference accelerator module. Neutron-flux levels and irradiation volumes were calculated for a neutron source incorporating two such modules, and interaction of the beam with the lithium jet was studied using a thermal-hydraulic computer simulation. Approximate cost estimates are provided for a range of beam currents and a possible facility staging sequence is suggested.

Advances in high-current linear-accelerator technology since the design of the Fusion Materials Irradiation Test (FMIT) Facility1 have increased the attractiveness of a deuterium-lithium (D-Li) neutron source for fusion materials and technology testing. This paper discusses a new approach to such a source aimed at meeting the near-term requirements of a high-flux high-energy International Fusion Materials Irradiation Facility (IFMIF). The concept employs multiple accelerator modules2 providing deuteron beams to two liquid-lithium jet targets oriented at right angles.3 This beam/target geometry provides much larger test volumes than can be attained with a single beam and target and produces significant regions of low neutron-flux gradient. A preliminary beam-dynamics design has been obtained for a 250-mA reference accelerator module. Neutron- flux levels and irradiation volumes were calculated for a neutron source incorporating two such modules, and interaction of the beam with the lithium jet was studied using a thermal-hydraulic computer simulation. Cost estimates are provided for a range of beam currents and a possible facility staging sequence is suggested.

Results of numerical beam-dynamics studies for both the radiofrequency quadrupole (RFQ) and the drift-tube linac (DTL) are presented. The scaling of longitudinal emittance produced during the adiabatic bunching in an RFQ is discussed. The benefits of using ramped DTL accelerating field designs to maintain high longitudinal focusing strength with increasing particle energy are shown. For the RFQ bunching, it is found that: (1) nonlinear RF and space-charge fields are both important, (2) xi /sub 1/ (longitudinal emittance) scales as the product of zero-current separatrix area times a current-dependent factor that decreases with increasing current, and (3) the decrease of xi /sub 1/ with current is correlated with transverse emittance growth. For the DTL, both rapid and slow charge-redistribution emittance growth mechanisms are observed. The rapid growth is consistent with the charge redistribution mechanism studied previously. The slow growth is caused by a gradual weakening of the longitudinal focusing force with increasing beam velocity and can be controlled if the accelerating field can be ramped to compensate.<>

The parameters for the proposed SSC linac injector system are obtained from the established requirements of the low-energy booster (LEB). The first element of this injector system is a radio-frequency quadrupole (RFQ) that bunches the H/sup /minus// ions and accelerates these ion bunches to 2.5 MeV. With a suitable matching section, this beam is injected into a drift-tube linac (DTL), which takes the ions to 120 MeV. The final element is a coupled-cavity linac (CCL) designed to accelerate the H/sup /minus// ions to 600 MeV for injection into the LEB. The conceptual beam dynamics design for the various elements of this linac injector system are described. 4 refs., 5 figs., 4 tabs.