CERN Accelerating science

Ramp

Oliver - slides on tolerances; crossing angle, beta beating, Q' etc.  tolerances tine/Q1 interplay, dynamic aperture

General

After snapback and the first 100 GeV we expect things to quieten down considerably. Clearly the power converters will be driving the the machine up. RF following. Orbit and possibly tune feedback operational. Real-time correction available to operator. Multipole factory feeding forward for as long as necessary.

Settings, baseline ramp,

 P(t) - 6 parameters

• Injection energy
• final energy
• length parabolic section
• max ramp rate
• ramp rate end parabolic
• start of ramp rate

• track corrections in ramp,
• (subtle) optics changes in ramp?
• feed forward - data management challenge

Measurements

• RF freq modulation during ramp, either program freq,.function, modulate radial loop function
• PLL
• Monitoring of collective effects
• Beta beating again an issue. How can this be monitored - one suggestion transverse beam profiles...

Power Converters

RF

Dampers, voltage and frequency driven by function generators, triggered by timing events. Details see here

Controlled longitudinal emittance blow-up at some pre-defined point in the ramp + monitoring thereof

Lattice Octupoles

For increased Landau damping - bring the octupoles up at some point in the ramp

Collimators

Left out during the ramp. Move to 7 sigma (or perhaps more) at the end of the ramp before starting the squeeze.

Orbit feedback

Discussed in detail elsewhere

Both global and local running. Lock angle and position in IRs to maintain beam separation at greater than 8 sigma throughout the ramp. Will have to be monitored all the way up the ramp.

At around 5 TeV (according to Stephane) the crossing scheme changes, he implied that a stop might be required.

Compensation bumps

Will be ramped

Electron cloud

Vacuum pressure and cryogenics heat load will need to be monitored. Scrubbing might be necessary at intermediate energies. Stop, move beam, monitor vacuum and heat load. Instabilities induced by electron cloud not expected to be a problem.