Emittance growth during bunch compression in the CTF-II

Area of Science:

• Particle accelerator physics
• High-energy physics
• Beam dynamics

Background:

• The Compact Linear Collider (CLIC) aims for high luminosity, requiring precise control over particle beams.
• Beam emittance, a measure of beam quality, is crucial for accelerator performance and must be preserved during acceleration and manipulation.
• Bunch compression is a key process in linear colliders to increase particle density, but it can lead to emittance growth.

Purpose of the Study:

• To experimentally measure beam emittance evolution during bunch compression in the CLIC Test Facility (CTF-II).
• To investigate the impact of varying beam charge and energy spread on emittance during compression.
• To identify the dominant mechanism responsible for emittance dilution in this process.

Main Methods:

• Utilized the CLIC Test Facility (CTF-II) for controlled beam manipulation experiments.
• Performed systematic measurements of beam emittance across a range of bunch compressor settings, from under-compression to over-compression.
• Varied beam charge and energy correlations to assess their influence on emittance growth.

Main Results:

• Observed significant increases in beam emittance as bunch compression progressed.
• Found that maximum beam emittance occurred near the point of full (maximal) compression.
• Emittance growth was correlated with specific bunch compressor settings and beam parameters.

Conclusions:

• Coherent synchrotron radiation (CSR) is identified as the most probable cause for the observed beam emittance dilution.
• Understanding and mitigating CSR effects is critical for preserving beam quality in future linear colliders like CLIC.
• These findings provide valuable experimental data for validating beam dynamics simulations and optimizing accelerator designs.