CERN, Geneva
BINP SB RAS, Novosibirsk
RFNC-VNIITF, Snezhinsk, Chelyabinsk region
The 352 MHz CCDTL will accelerate the Linac4 beam from 50 to 102 MeV. It will be the first CCDTL used in a proton linac. Three short DTL tanks, each having two drift tubes, are connected by coupling cavities and form a chain of 5 resonators operating in the stable π/2 mode. The CCDTL section is made of 7 such chains, each fed by a 1.3 MW klystron. Focusing quadrupoles are placed between tanks, easing their alignment with respect to a conventional DTL thus making the structure less sensitive to manufacturing errors. In order to validate the design and to develop the production technology, two prototypes have been constructed and successfully tested. The first prototype, built at CERN, consists of two half-cavities and one coupling cell, whereas the second, with two full cavities and one coupling cell, was built at VNIITF and BINP in Russia in the frame of an R&D contract funded by the ISTC Organisation. Both prototypes have been tested at CERN slightly beyond their nominal power level, at the design duty cycle of 10%. In this paper we present the results of high-power tests, the results of the technological developments prior to production, and the final design of the CCDTL.
Fermilab, Batavia
Low energy part of the linac for the HINS project at Fermilab will use superconducting solenoids as beam focusing elements (lenses). While lenses for the conventional, DTL-type accelerating section of the front end require individual cryostats, in the superconducting accelerating sections solenoids will be installed inside rf cryomodules. Some of the lenses in the conventional and in the superconducting sections are equipped with horizontal and vertical dipole correctors. Lenses for the conventional DTL section are in the stage of production with certification activities ongoing at Fermilab. For the superconducting sections of the linac, several prototypes of focusing lenses were built and tested. Solenoid magnetic axis is used for alignment of the lenses in the transport channel of the accelerator. Corresponding technique has been developed at Fermilab and is used during certification of the production lenses for the DTL section. This report will summarize main design features, parameters, and test results of the focusing lenses of the linac. Magnetic axis alignment technique will also be described.
IAP, Frankfurt am Main
BNL, Upton, Long Island, New York
A new RFQ is being built as a part of the new EBIS-linac at BNL. The RFQ accepts highly charged ions from the EBIS ion source with energy of 17 keV/u and ion currents of up to 10 mA. The operation frequency will be 100.625 MHz . The design had been optimized to get a rather short structure with LRFQ=3.1 m with moderate electrode voltages of UQ = 70 kV. The resonant insert has a cooled base plate and solid stems and vane-electrodes. The mechanical design is very stiff, with a precise base-structure. The top lid along the RFQ allows installation, alignment, inspection and maintenance. After the mechanical alignment of the electrodes the longitudinal electrode voltage distribution will be adjusted with tuning plates between the stems. The properties of the RFQ, the results of the tuning and the status of the project will be discussed.
IHEP Beijing, Beijing
In the China Spallation Neutron Source (CSNS) linac, a conventional 324 MHz drift-tube linac (DTL) accelerating an H- ion beam from 3 MeV to 132 MeV has been designed with 1.05% duty, consisting of 7 tanks with a total length of approximately 59.6 m. Currently, R&D work has focused on Tank 1, which will have 61 drift-tubes (DT) each housing an electro-magnet quadrupole (EMQ). Some EMQs with SAKAE coil have been fabricated and are under rigorous magnetic measurements by means of Hall probe, single stretched wire, rotating coil in order to verify the design specifications and fabrication technology. Magnetic measurements on the EMQs with iron cores made from the electrical-discharge machining (EDM) and the stacking method will be compared and discussed. Work has been implemented to reduce the alignment discrepancies between the geometric center of the DT and magnetic center of EMQ to within ± 50 μm.
CERN, Geneva
INFN/LNL, Legnaro, Padova
The Drift Tube Linac (DTL) for the new linear accelerator Linac4 at CERN will accelerate H- ion beams of up to 40mA average pulse current from 3 to 50MeV. It is designed to operate at 352.2MHz and at duty cycles of up to 10%, if required by future physics programmes. The accelerating field is 3.2MeV/m over the entire length. Permanent magnet quadrupoles are used as focusing elements. The 3 DTL cavities consist of 2, 4 and 4 segments of about 1.8m each, are equipped with 35, 41 and 29 drift tubes respectively, and are stabilized with post-couplers. Several new features have been incorporated in the basic design. The electro-magnetic design has been refined in order to reduce peak field levels in critical areas. The mechanical design aims at reducing the complexity of the mechanical structure and of the adjustment procedure. Drift tubes and holders on the tanks that are machined to tight tolerances do not require adjustment mechanisms like screws or bellows for drift tube positioning. A scaled cold model, an assembly model and a full-scale prototype of the first half tank have been constructed to validate the design principles. The results of metrological and rf tests are presented.
CEA, Gif-sur-Yvette
CERN, Geneva
LAL, Orsay
The CLIC project based on the innovative Two Beams Acceleration concept is currently under study at CTF3 where the acceleration of a probe beam will be demonstrated. This paper will describe in details the status of the probe beam linac called CALIFES. This linac (170 MeV, 1 A) is developed by CEA Saclay, LAL Orsay and CERN. It will be installed in the new experimental area of CTF3 to deliver short bunches (1.8 ps) with a charge of 0.6 nC to the CLIC 12 GHz accelerating structures. The linac consists in an rf gun triggered by a laser beam, three LIL sections for bunching and acceleration, a beam diagnostic system and a single klystron with a pulse compression cavity and a dedicated rf network. We report new results of beam dynamic simulation considering the new CLIC parameters. We will give an estimation of the energy and phase deviation over the bunch train (140 ns long) by transient calculation of beam loading. Details about the fabrication of the rf gun, the cavity BPM, the HV modulator and the power phase shifter will be described. New results from laser system studies are discussed. The construction of CALIFES and the start of commissioning will be also reported.
Fermilab, Batavia
Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Fermilab is involved in an effort to design, build, test and deliver four 3.9 GHz superconducting rf cavities within a single cryomodule to be delivered to DESY as a 'third harmonic' structure for the FLASH facility to improve the longitudinal emittance. In addition to an overall status update we will present recent results from single 'dressed' cavity horizontal tests and shipping and alignment measurements.
TRIUMF, Vancouver
The ISAC 2 superconducting rf cavities use self-excited, phase-locked mode of operation. As such the microphonics are sensitive to the alignment of the phase control loop. Although initial alignments can minimize the effect of microphonics, long term drifts, particularly in the power amplifiers, can cause the control loop to misalign and an increase in sensitivity to microphonics. The ISAC 2 control system monitors several points in the control loop to determine the phase alignment of the power amplifiers as well as the rf resonant cavities. Online adaptive feedbacks using Self Tuning Regulators are employed to bring the different components back into alignment.