ANL, Argonne, USA
RadiaBeam, Marina del Rey, California, USA
Argonne National Laboratory is developing an Advanced Compact Carbon Ion Linac (ACCIL) in collaboration with RadiaBeam Technologies. The 45-meter long linac is designed to deliver up to 109 carbon ions per second with variable energy from 45 MeV/u to 450 MeV/u. To optimize the linac design in this energy range both backward traveling wave and coupled cell standing wave S-band structures were analyzed. To achieve the required accelerating gradients our design uses accelerating structures excited with short RF pulses (~500 ns flattop). The front-end accelerating structures such as the RFQ, DTL and Coupled Cell DTL are designed to operate at lower frequencies to maintain high shunt impedance. In parallel with our design effort ANL's RF test facility has been upgraded and used for the testing of an S-band high-gradient structure designed and built by Radiabeam for high pulsed RF power operation. The 5-cell S-band structure demonstrated 52 MV/m acceleration field at 2 μs 30 Hz RF pulses. A detailed physics design, including a comparison of different accelerating structures and end-to-end beam dynamics simulations of the ACCIL will be presented.
ORNL, Oak Ridge, Tennessee, USA
Waveguide iris couplers are frequently used to power accelerating cavities in low beta sections of ion accelerators. In ORNL Spallation Neutron Source (SNS), six drift tube linac (DTL) cavity structures have been operating. An iris input coupler with a tapered ridge waveguide and a waveguide ceramic disk window feeds each cavity. The original couplers and cavities have been in service for more than a decade. Since all DTL cavity structures are fully utilized for neutron production, none of the cavity structures is available as a test cavity or a spare. Maintaining spares of the iris couplers for operations and future system upgrade without using the full DTL structure, a test setup for precision tuning is needed. A smaller single-cell cavity may be used for pretuning of the coupling irises as the test cavity and high power RF conditioning of the iris couplers as the bridge waveguide. In this paper, study of using a single-cell cavity for the iris tuning and the conditioning is presented with 3D simulations. A single-cell test cavity has been built and used for low power bench measurement with the iris couplers to demonstrate the approach.
LANL, Los Alamos, New Mexico, USA
Beam bunching optimization at low energy (750keV) before injecting into a DTL (100MeV) is essential for beam transport, emittance reduction, and focusing on to a target. The LANSCE simultaneously utilizes H+ and H− beam (with a timing variation) for many important national security sciences. In addition to quadrupole, several bunchers are utilized in the transport. A technique with pre-bunching at lower frequency and main bunching at higher frequency is utilized for beam injection into the linac. The buncher parameters (voltage and frequency) are well established for operations. However, there is the possibility that the parameters vary with time due to electrical malfunction or adverse tuning during a beam development activity. Some effort is needed to correct the parameters as a non-optimized pre-bunching setup can alter the beam phase space and the nominal beam intensity at a desired location. Here, we examine emittance and phase space distribution variation for H− beam due to variation of the low frequency (16 MHz) buncher voltage, which typically operates at 25 kV peak. Beam phase dynamics with buncher voltage variation is also examined using the beam transport code Parmila.
LA-UR-16-23822
LANSCE: Los Alamos Neutron Science Center
DTL: Drift Tube Linac
ESS, Lund, Sweden
CERN, Geneva, Switzerland
ADAM SA, Geneva, Switzerland