Design Study of the CLIC Injector and Booster Linacs with the 2007 Beam Parameters

This note presents new particle tracking studies in the CLIC Injector and Booster Linacs, which accelerate both electrons and positrons, respectively from 200 MeV to 2.42 GeV, prior to their injection into the pre-damping rings, and from 2.42 to 9 GeV, before their transport to the main accelerating linacs

Tune Variations due to Septum Stray Field F. Pederson &

Two types of antiproton instabilities due to trapped ions are harmful in the AA. One is a coherent instability occurring when an ion pocket resonates with a 3-Q mode (hiccups), the other is excitation of 11th and 15th order non-linear resonances due to the non-linear focusing fields from localized ion clouds trapped in uncleared potential well pockets. Accumulation with a good injection yield of antiprotons forces us to locate the tune of the dense core in the general area of the array of 15th order resonances. To avoid harmful blow-up of the dense core the tune is located between the resonances 11Q{sub H} + 4Q{sub V} = 34, 10Q{sub H} + 5Q{sub V} = 34, and 11Q{sub H} = 25, requiring a tune of Q{sub H} = 2.2722 to be maintained with a precision of a few 10{sup -4} (Fig. 4). Different angles of the injection and ejection trajectories require the septum current to be changed from 3860 A during accumulation to 3920 A, during ejection mode. Variations in the septum stray field due to these changes in current cause tune changes in the order of 10{sup -3}. In addition, at a given septum current, a pronounced hysteresis of the stray field causes tune variations of about the same order of magnitude, so also the past history of the septum excitation must be carefully controlled to obtain a reproducible tune

CLIC Main beam dynamics in the ring to main LINAC transport

Prior to acceleration in the main linac, the particle beams created in the centrally located injector have to be transported to the outer ends of the CLIC site. This transport should not only preserve the beam quality but also shape, characterize and tune the phase space distribution to match the requirements at the entrance of the main linac. Hence, the performance of the transport downstream of the damping rings up to the main linac, the so called RTML, is crucial for the overall performance of CLIC. We discuss the different parts of the RTML and the occurring beam dynamics challenges. Their status is outlined and results of beam dynamics simulations are presented

A Low Charge Demonstration of Electron Pulse Compression for the CLIC RF Power Source

The CLIC (Compact Linear Collider) RF power source is based on a new scheme of electron pulse compression and bunch frequency multiplication using injection by transverse RF deflectors into an isochronous ring. In this paper, we describe the modifications needed in the present LEP Pre-Injector (LPI) complex at CERN in order to perform a low-charge test of the scheme. The design of the injector (including the new thermionic gun), of the modified linac, of the matched injection line, and of the isochronous ring lattice, are presented. The results of preliminary isochronicity measurements made on the present installation are also discussed.Comment: 3 pages, 5 figures, submitted to the LINAC 2000 Conferenc

Experimental Evaluation of the RF Shielding Properties of a Thin Resistive Layer in a Ceramic Chamber

In order to better understand the RF shielding properties of a thin resistive layer inside a ceramic vacuum chamber, an experimental set-up has been installed in the Electron Positron Accumulator (EPA) at CERN. A 500 MeV single bunch of about 7 x 1010 electrons (rms s=1 ns) is extracted into this dedicated beam line at a repetition rate of about 1 Hz. Wideband magnetic field probes are installed on the outer surfaces of a resistively coated ceramic test chamber as well as on a reference non-coated chamber located 2.5 m downstream the line. At the end of the extraction line, the beam passes through a thin Aluminum foil and is absorbed in an external dump. The experimental layout and the first results are presented. A comparison with theoretical expectations as well as possible implications for future machines are also discussed

AN INJECTOR FOR THE CLIC TEST FACILITY (CTF3)

Abstract The CLIC Test Facility (CTF3) is an intermediate step to demonstrate the technical feasibility of the key concepts of the new RF power source for CLIC. CTF3 will use electron beams with an energy range adjustable from 170 MeV (3.5 A) to 380 MeV (with low current). The injector is based on a thermionic gun followed by a classical bunching system embedded in a long solenoidal field. As an alternative, an RF photo-injector is also being studied. The beam dynamics studies on how to reach the stringent beam parameters at the exit of the injector are presented. Simulations performed with the EGUN code showed that a current of 7 A can be obtained with an emittance less than 10 mm.mrad at the gun exit. PARMELA results are presented and compared to the requested beam performance at the injector exit. SubHarmonic Bunchers (SHB) are foreseen, to switch the phase of the bunch trains by 180 degrees from even to odd RF buckets. Specific issues of the thermionic gun and of the SHB with fast phase switch are discussed

ERL Scheme for Compton Polarised Positron Sources

International audienceOne of the main challenges for the future linear colliders projects (ILC and CLIC) is to design an efficient positron source taking into account the constraints imposed by the target heating. At present, different schemes have been analysed to produce high energy gammas and to convert them in an amorphous target. One of them considers the possibility to boost the energy of the backscattered photons of a laser pulse by Compton effect. This method is very attractive since the source is independent from the main Linac and since the photon helicity is conserved in Compton scattering and subsequently transferred to the produced pairs. This allows the physics experiments disposing of both positron and electron polarised sources. Different schemes have been proposed to provide the electron beam for the Compton collisions. taking into account the constraint imposed by the low value of the Thomson cross section. One of the explored possibilities is to design an ERL with relatively low repetition frequency, high charge per pulse and then to stack the produced positrons in an accumulation ring. Different considerations on this scheme will be illustrated and the main constraints discussed. MO6RFP06

CTF3 drive-beam injector design

The Two-Beam Accelerator concept is one of the most promising methods for producing RF power for future linear colliders. In particular it allows upgrades to multi-TeV energies. One of its challenges is the production of the high current drive beam, which as it passes through decelerating structures, produces rf power for acceleration of the main beam. These challenges must be studied at a smaller scale test facility

Stacking Simulations for Compton Positron sources of Future Linear Colliders

The Compton positron source of a future linear collider must obtain the target bunch population by accumulating a large number of positron packets, arriving either in a number of bursts from a ‘Compton ring’, with intermediate damping of the scattering electron beam, or quasicontinually from a ‘Compton energy recovery linac’. We present simulation results for the longitudinal stacking of Compton positrons in the ILC damping ring (DR) and the CLIC pre-damping ring (PDR), discussing parameter optimization, stacking efficiency, possible further improvements, and outstanding questions