Silvia Verdú-Andrés

Design, prototyping, and testing of a compact superconducting double quarter wave crab cavity

A novel design of superconducting Crab Cavity was proposed and designed at Brookhaven National Laboratory. The new cavity shape is a Double Quarter Wave or DQWCC. After fabrication and surface treatments, the niobium proof-of-principle cavity was cryogenically tested in a vertical cryostat. The cavity is extremely compact yet has a low frequency of 400 MHz, an essential property for service for the Large Hadron Collider luminosity upgrade. The electromagnetic properties of the cavity are also well matched for this demanding task. The demonstrated deflecting voltage of 4.6 MV is well above the requirement for a crab cavity in the future High Luminosity LHC of 3.34 MV. In this paper we present the design, prototyping and test results of the DQWCC.

CABOTO, a high-gradient linac for hadrontherapy

The field of hadrontherapy has grown rapidly in recent years. At present the therapeutic beam is provided by a cyclotron or a synchrotron, but neither cyclotrons nor synchrotrons present the best performances for hadrontherapy. The new generation of accelerators for hadrontherapy should allow fast active energy modulation and have a high repetition rate, so that moving organs can be appropriately treated in a reasonable time. In addition, a reduction of the dimensions and cost of the accelerators for hadrontherapy would make the acquisition and operation of a hadrontherapy facility more affordable, which would translate into great benefits for the potential hadrontherapy patients. The ‘cyclinac’, an accelerator concept that combines a cyclotron with a high-frequency linear accelerator (linac), is a fast-cycling machine specifically conceived to allow for fast active energy modulation. The present paper focuses on CABOTO (CArbon BOoster for Therapy in Oncology), a compact, efficient high-frequency linac that can accelerate C6+ ions and H2 molecules from 150–410 MeV/u in ∼24 m. The paper presents the latest design of CABOTO and discusses its performances.

JACoW : Trim Tuning of SPS-Series DQW Crab Cavity Prototypes

The final steps in the manufacturing of a Superconducting Radio-Frequency (SRF) cavity involve careful tuning before the final welds to match the target frequency as fabrication tolerances may introduce some frequency deviations. The target frequency is chosen based on analysis of the deviation induced by remaining processing steps, including acid etching and cool down. The baseline fabrication of a Double-Quarter Wave (DQW) crab cavity for the High Luminosity Large Hadron Collider (HLLHC) envisages a first tuning before the cavity subassemblies are welded together. To produce a very accurate final result, subassemblies are trimmed to frequency in the last machining steps, using a clamped cavity assembly for RF measurements. This paper will describe the trim tuning of two SPS prototype DQW crab cavities fabricated by Niowave.

Crab Cavities for eRHIC - A Preliminary Design

The proposed eRHIC electron ion collider at BNL must use a relatively large crossing angle between the ion and electron beams for various reasons, including the reduction of the long-range beam-beam effects and minimization of synchrotron radiation noise in the detector. To prevent significant loss of the luminosity due to this large crossing angle, the design of the collider requires the use of groups of crab cavities to provide local crabbing for both proton/ion and electron beams. We will base our design for eRHIC crab cavities based on our experience in the design of the 400 MHz double quarter wave crab cavity (DQWCC) for the high luminosity. eRHIC CRAB CAVITY PROJECT The high current electron-ion collider (EIC) requires quick separation of the electron and ion beams at the interaction region to prevent beam-beam instabilities. A careful study looked into the possibility of achieving this by a crossing angle of the beams or a separation dipole. The conclusion from the study favoured the crossing angle, because the separation dipole is incompatible with the physics and detector constraints [1]. To prevent significant loss of the luminosity due to large crossing angle, 10mrad or 15mrad for linac-ring or ring-ring scheme respectively, in the future EIC at BNL (eRHIC), there is a demand for crab cavities that deliver high deflecting voltages. Table 1: Preliminary Basic Beam and Crab Cavity Parameters for Linac-ring Scheme of eRHIC. Parameters Baseline Design Ultimate Design Electron Proton Electron Proton Crossing angle (Full, mrad) 10 10 Beam energy (GeV) 20 250 20 250 Beta function at IP (, cm) 12.5 12.5 5 5 Transverse beam size at IP (μm) 15.3 15.3 7.1 7.1 Bunch length (cm) 0.3 15 0.3 5 Piwinski angle (rad) 0.98 49.0 2.14 35.7 Beta function at crab cavity (m) 115 ~1000 27