Variable CW RF power coupler for 345 MHz superconducting cavities

This paper reports the development of a CW variable coupler for 345 MHz spoke-loaded superconducting (SC) cavities. The coupler inserts an 80 K copper loop into a 5 cm (2 inch) interior diameter coupling port on several types of spoke-loaded cavity operating at 2 K or 4 K. The coupling loop can be moved during operation to vary the coupling over a range of 50 dB. The coupler is designed to facilitate high-pressure water rinsing and low-particulate clean assembly. Design details and operating characteristics are discussed

Superconducting RFQs

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Project of an advanced ISOL facility for exotic beams at LNL

Abstract In the framework of the European program to define a second generation Radioactive Ion Beam facility, LNL are proposing the construction in the next five–seven years of a specialized national facility for RIB originated by fission fragments produced by secondary neutrons. It consists on a two-accelerator ISOL-type facility to provide intense neutron-rich radioactive ion beams of highest quality, in the range of masses between 80 and 160. The conceptual design is based on a high intensity 50 MeV (100 kW) proton linac as driver and on the availability of the heavy-ion accelerator ALPI as post accelerator. The estimated neutron yield is 2×1014 n/s at 0°, high enough to satisfy the demand for an advanced RIB facility. An intense R&D program on different items is actually in progress in collaboration with other Laboratories and University groups and is moving in a European context

Experience with the ALPI linac resonators

Abstract The medium β section of the linac accelerator ALPI [G. Fortuna et al., Nucl. Instr. and Meth. A 328 (1993) 236] is now in operation: beams of 32 S, 37 Cl, 58 Ni, 76 Ge, 81 Br were accelerated for nuclear physics experiments in the first half of 1995. The medium β section of ALPI includes 12 cryostats containing four accelerating quarter-wave resonators each ( β = 0.11, f = 160 MHz). Two similar resonators are installed in a buncher cryostat and two in a rebuncher unit. Accelerating fields around 2.5 MV/m are available. The experience in cavity preparation, installation, conditioning and operation is described

Integration of RFQ beam coolers and solenoidal magnetic fields

Electromagnetic traps are a flexible and powerful method of controlling particle beams, possibly of exotic nuclei, with cooling (of energy spread and transverse oscillations) provided by collisions with light gases as in the Radio Frequency Quadrupole Cooler (RFQC). A RFQC prototype can be placed inside the existing Eltrap solenoid, capable of providing a magnetic flux density component Bz up to 0.2 T, where z is the solenoid axis. Confinement in the transverse plane is provided both by Bz and the rf voltage Vrf (up to 1 kV at few MHz). Transport is provided by a static electric field Ez (order of 100 V/m), while gas collisions (say He at 1 Pa, to be maintained by differential pumping) provide cooling or heating depending on Vrf. The beamline design and the major parameters Vrf, Bz (which affect the beam transmission optimization) are here reported, with a brief description of the experimental setup

Development and installation of a radio frequency quadrupole cooler test

A Radio Frequency Quadrupole Cooler (RFQC) prototype was adapted for insertion into a high uniformity magnetic field, with Bz up to 0.2 T, to improve radial confinement. While the RFQC purpose is to reduce (by gas collisions) the energy spread and emittance of a beam of radioactive nuclei, to finely select ion mass in nuclear physics, the prototype is tested in a setup including a stable ion source, a pepper pot emittance meter, and two Faraday cups; this makes a precise characterization of the RFQC feasible. The ion extraction was studied in detail by simulations, both to match it to the emittance meter granularity and to verify the effect of the typical nonuniformity of the longitudinal electric field Ez inside the RFQC; an average motion description (including friction force from gas collisions) was used, introducing the ballistic and diffusive regimes. With a preliminary optimization of the electrode shape, buffer gas pressure pg, and radio frequency voltage, the ion beam can be extracted with a significant cooling margin

Construction of superconducting RFQs at INFN-LNL

The tests on the stainless steel prototype for one of the two superconducting RFQs (SRFQs) for PIAVE (SRFQ2), the being built heavy ion injector for the Legnaro booster, were completed in summer 1998, while the construction of the first niobium resonator started in February 1998 and is expected to be completed by April 1999. The structure, resonating at 80 MHz, is 0.8 m long and 0.76 m in diameter. All technological aspects connected with the construction of the SRFQs, and the corresponding tests on the stainless steel model, are reviewed: development of the parts, assembly sequence, electron beam welding (EBW) steps, rough and fine adjustment of the resonant frequency, bead-pull measurements, characterization of the mechanical vibration modes, frequency change due to cooling down and chemical etching tests. The updated development of SRFQ1 is briefly reviewed

Prospects for advanced electron cyclotron resonance and electron beam ion source charge breeding methods for EURISOL

As the most ambitious concept of isotope separation on line (ISOL) facility, EURISOL aims at producing unprecedented intensities of post-accelerated radioactive isotopes. Charge breeding, which transforms the charge state of radioactive beams from 1+ to an n+ charge state prior to postacceleration, is a key technology which has to overcome the following challenges: high charge states for high energies, efficiency, rapidity and purity. On the roadmap to EURISOL, a dedicated R&D is being undertaken to push forward the frontiers of the present state-of-the-art techniques which use either electron cyclotron resonance or electron beam ion sources. We describe here the guidelines of this R&D.peerReviewe

Prospects for advanced electron cyclotron resonance and electron beam ion source charge breeding methods for EURISOL

International audienceAs the most ambitious concept of isotope separation on line (ISOL) facility, EURISOL aims at producing unprecedented intensities of post-accelerated radioactive isotopes. Charge breeding, which transforms the charge state of radioactive beams from 1+ to an n+ charge state prior to postacceleration, is a key technology which has to overcome the following challenges: high charge states for high energies, efficiency, rapidity and purity. On the roadmap to EURISOL, a dedicated R&D is being undertaken to push forward the frontiers of the present state-of-the-art techniques which use either electron cyclotron resonance or electron beam ion sources. We describe here the guidelines of this R&D

The SPES project at the INFN- Laboratori Nazionali di Legnaro

The SPES Radioactive Ion Beam (RIB) facility at INFN-LNL is in the construction phase. It is based on the ISOL method with an UCx Direct Target able to sustain a power of 10 kW. The primary proton beam is delivered by a high current Cyclotron accelerator, with energy 35-70 MeV and a beam current of 0.2-0.5 mA. Neutron-rich radioactive ions will be produced by proton induced Uranium fission in the UCx target at an expected fission rate in the order of 1013 fissions per second. The exotic isotopes will be re-accelerated by the ALPI superconducting LINAC at energies of 10A MeV and higher, for masses in the region A=130 amu at expected rate on the secondary target of 107 – 109 pps. The SPES project has the aim to provide high intensity and highquality beams of neutron-rich nuclei as well as to develop an interdisciplinary research center based on the cyclotron proton beam