Status of the CTF3 Frequency Multiplication Rings

Proc. EPAC, 2004

The aim of the CLIC (Compact Linear Collider) Study is to investigate the feasibility of a high luminosity, multi-TeV linear e+e-collider. CLIC is based on a two-beam method, in which a high current drive beam is decelerated to produce 30 GHz RF power needed for high-gradient acceleration of the main beam running parallel to it. To demonstrate the outstanding feasibility issues of the scheme a new CLIC Test Facility, CTF3, is being constructed at CERN by an international collaboration. In its final configuration CTF3 will consist of a 150 MeV drive beam linac followed by a 42 m long delay loop and an 84 m combiner ring. The installation will include a 30 GHz high power test stand, a representative CLIC module and a test decelerator. The first part of the linac was installed and commissioned with beam in 2003. The first issue addressed was the generation and acceleration of a high-current drive beam in the "full beam loading" condition where RF power is converted into beam power with an efficiency of more than 90 %. The full beam loading operation was successfully demonstrated with the nominal beam current of 3.5 A. A variety of beam measurements have been performed, showing good agreement with expectations.

2001

In the framework of the CLIC (Compact Linear Collider) RF power source studies, the scheme of electron pulse compression and bunch frequency multiplication, using injection by RF deflectors into an isochronous ring, will be tested, at low charge, during the preliminary phase of the new CLIC Test Facility (CTF3) at CERN. In this paper, we describe the beam dynamics studies made in order to assess the feasibility of the bunch combination experiment, as well as the related beam measurements performed on the LEP Pre-Injector complex (LPI) before its transformation into CTF3.

1998

The second phase of the Compact LInear Collider (CLIC) Test Facility (CTF II) at CERN has demon-strated the feasibility of two-beam acceleration at 30 GHz using a high-charge drive beam, running parallel to the main beam, as the RF power source. To date accelerating gradients of 59 MV/m at 30 GHz have been achieved. In CTF II, the two beams are generated by 3 GHz RF photo-injectors and are accelerated in 3 GHz linacs, before injection into the 30 GHz modules. The drive beam linac has to accelerate a 16 ns long train of 48 bunches, each with a nominal charge of 13.4 nC. To cope with the very substantial beam-loading special accelerating structures are used (running slightly off the bunch repetition frequency). A magnetic chicane compresses the bunches to less than 5 ps fwhm, this is needed for efficient 30 GHz power generation. The 30 GHz modules are fully-engineered representative sections of CLIC, they include a 30 GHz decelerator for the drive beam, a 30 GHz accelerator for the main beam, high resolution BPM's and a wire-based active align-ment system. The performance achieved so far, as well as the operational experience with the first accelerator of this type, are reported.

The Compact Linear Collider international collaboration is pursuing an extensive R&D program towards a multi-TeV electron-positron collider. In particular, the development of two-beam acceleration technology is the focus of the CLIC test facility CTF3. In this paper we summarise the most recent results obtained at CTF3: the results of the studies on the drive beam generation are presented, the achieved two beam acceleration performance is reported and the measured breakdown rates and related observations are summarised. The stability of the deceleration process performed over 12 subsequent modules and a comparison of the obtained results with the theoretical expectations are discussed. We also outline the future experimental program.

Abstract The objective of the CLIC Test Facility CTF3 is to demonstrate the feasibility issues of the CLIC two-beam technology. CTF3 consists of an electron linac followed by a delay loop, a combiner ring and a two-beam test area. One issue studied in CTF3 is the efficient generation of a very high current drive beam, used in CLIC as the power source to accelerate the main beam to multi-TeV energies.

Abstract The aim of the CLIC Test Facility CTF3, built at CERN by an international collaboration, is to address the main feasibility issues of the CLIC electron-positron linear collider technology by 2010. One key-issue studied in CTF3 is the generation of the very high current drive beam, used in CLIC as the RF power source.

2008

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, 0.9 A) is developed by CEA Saclay, LAL Orsay and CERN. It has been 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. We report new results of beam dynamic and RF simulations considering the new CLIC parameters. The construction of CALIFES in the CLEX building is presented. Recent measurements from the laser system are discussed. Details about the HV modulator tests and the power phase shifter fabrication will be described and the start of commissioning will be also reported.

8th European Particle …, 2002

The Preliminary Phase of the new CLIC Test Facility CTF3 consists of a low-charge demonstration of the electron bunch train combination process on which the CLIC drive beam generation scheme is based. The principle of the combination relies on the injection of short electron bunches into an isochronous ring using RF deflecting cavities. The commissioning of this facility started in September 2001, with alternating periods of installation work and beam studies. In this paper, we present the status of the facility, the first beam measurements and the next steps towards the completion of the experiment.

2013

The feasibility of the CLIC novel scheme of two-beam acceleration was extensively tested in the CTF3 facility over the last few years. In particular, efficient full beam loading acceleration, isochronous ring operation, beam recombination by transverse RF deflectors have been fully proven. 12 GHz RF power production by highcurrent drive beam is now part of CTF3 routine operation, and two-beam acceleration up to 150 MV/m has been achieved. Drive beam deceleration tests were carried out as well. In this paper we summarize the main results obtained, including the more recent ones. We also outline and discuss the future experimental program, both in CTF3 and in other beam facilities, as well as the path to a possible facility needed in the initial stage of the CLIC project, CLIC0. Presented at: 3rd International Particle Accelerator Conference 2012, New Orleans, LA, USA, 20 25 May 2012 Geneva, Switzerland Date 20/05/2012 CLIC – Note – 962

DIPAC, 2003

In the framework of the CLIC RF power source studies, the feasibility of the electron bunch train combination by injection with RF deflectors into an isochronous ring has been successfully demonstrated in the preliminary phase of CTF3. A new method, based on beam frequency spectrum analysis, was experimented to monitor this scheme. A coaxial pick-up and its read-out electronics were designed and mounted in the CTF3 ring to allow comparison of the amplitudes of five harmonics of the fundamental beam frequency (3 GHz) while combining the bunch trains. The commissioning of the monitor was a successful proof of principle for this new method, despite the short length of the bunch trains and the presence of parasitic signals associated to high-order waveguide modes propagating with the beam inside the pipe.