Drive beam issues – CTF3
The present CTF3 experimental program is meant to cover the feasibility demonstration of the
Drive Beam generation and the Two-Beam acceleration issues. However, some of the issues will
require further R&D to ensure performance and optimize cost. As mentioned before, CTF3 will
also play the role of 12 GHz power production facility for RF testing. Therefore, the CTF3 will
still be operated and upgraded during the period 2011 to 2016 for the preparation of the project.
In particular, the two beam test stand (TBTS) should be extended and upgraded as a succession
of CLIC nominal modules used to optimize the integration of the various components including
active alignment, vibration control, beam diagnostic and nominal quadrupoles. The test
beamline (TBL) would be equipped with PETS with ON/OFF capability and would take
advantage of the overall RF power production of about 2.5 GW for conditioning a large number
of accelerating structures in parallel. Other tests needing relevant hardware investment are a full
test of the drive beam phase feedback system and the installation of a Instrumentation Test
Beamline (ITB) downstream of the probe beam injector CALIFES.
Status in 2010:
Drive Beam Injector: a) thermionic option: scheme for satellites control, stability assessment in
CTF3. b) photoinjector option: measurements of beam quality, stability and long test running of
prototype (PHIN) in CTF2
Drive Beam Accelerator: Full beam loading, high current operation in CTf3 (95% efficiency RFto-beam, SICA 3 GHz, 5 A beam current). Current stability ~ 10-3 Energy stability ~ 10-3
Rings, combination scheme: About 30 A combined and transported, bunch length < 1 mm,
emittance ~ 100 p mm mrad, current & energy stability a few 10-3. CLIC DL & CR design. Phase
stability?
Sources (modulators & klystrons): Parametric study of DBA power scheme, reference structure
design, modulators & klystrons specifications.
Drive beam phase and amplitude feedback: Timing reference system, conceptual feedback
system.
Power production from drive beam, Two-Beam issues: Beam-powered test of a single PETS with
external recirculation in TBTS/CTF3, to nominal parameters (135 MW, 240 ns). Power, energy
loss & gain measurements. First break-down kick measurement. Basic test of two beam
acceleration with one PETS and one structure at nominal parameters. First experiment on beam
loading control in TBTS/CTF3.
Manufacture, industrialization & integration: Baseline design of CLIC module.
Deceleration: TBL equipped with 8 PETS to demonstrate energy extraction of 30 %, energy
balance measurements, drive beam stability 30 A, BBA studies. About 1 GW of 12 GHz should be
produced. CLIC Lattice design including cost optimization options - study of decelerator
stability, beam loss estimates, including beam based alignment.
Goals in 2013:
Drive Beam Injector: Comparison and choice between photo-injector and thermionic solution.
Possible implementation of photo-injector (PHIN) in the CTF3 linac.
Drive Beam Accelerator: Current stability < 10-3. Energy stability < 10-3.
Rings, combination scheme: Current & Energy stability below 10-3. Phase stability monitor
(FP7), measurements.
Sources (modulators & klystrons): Design of M&K, start prototyping – possibly a few prototypes
ready in 2012.
Drive beam phase and amplitude feedback: low impedance phase monitor, test in CTF3.
Power production from drive beam, Two-Beam issues: Complete break-down kick
measurement. Break-down studies. Improved beam loading experiment in CTF3/TBTS – full
charge.
Manufacture, industrialization & integration: Integration of accelerating structures, PETS &
ancillary equipment in CLIC modules in CTF3.
Deceleration: TBL equipped with 16 PETS, 30 A and 50 % energy extraction demonstrated,
100% transmission and stable deceleration and power production of > 2 GW of 12 GHz power.
Benchmark with simulations. Measure output power stability and beam stability.
Goals in 2016:
Drive Beam Injector: Injector prototype at the right frequency and energy.
Drive Beam Accelerator: First part of linac at right frequency (100 MeV?) final stability
Efficiency > 90% including RF network.
Rings, combination scheme: Eventually add final DL & ring(s) to injector/DBA ??
Sources (modulators & klystrons): M&Ks with full specs, as needed for injector and DBA
section.
Drive beam phase and amplitude feedback: DB fast phase feed-back in CTF3 – experimental
studies (Kickers, amplifiers, improved phase monitors). Alternative timing reference (e.g. XFEL).
Power production from drive beam, Two-Beam issues: Drive beam bunch charge control. Main
beam current feed-forward? e.g. temperature effects
Manufacture, industrialization & integration: Production of N modules (N>20) with combined
alignment/stabilization system ?Deceleration: Use TBL for power production, see test facilities.
Eventually new more realistic decelerator within CLIC0