# Presentation: 882084

## CD-ILC briefing with Young-Kee Kim 

- Low Level RF (LLRF) project for ILCTA and ILC

## What is Low Level RF?

- Low power RF circuits and feedback controls, including:
- Master oscillator (MO) and Local Oscillator (LO)
- The MO provides the 1.3GHz reference for all RF components.
- The LO provides a frequency slightly higher/lower than the MO frequency used to shift the cavity probe signal in the frequency domain.
- RF down-converters
- Convert the cavity probe signal spectrum to an Intermediate Frequency (IF) domain.
- Timing hardware
- Time accelerator related events such as the start of a beam pulse.
- Cavity controller
- Controls the power delivered by the klystron to the cavities.
- LLRF is a key subject for Fermilab in ILC.
- LLRF: requires relatively small M&S but lot’s of manpower.

## Simplified LLRF block diagram (for CC2 system)

**RF frequencies**

**Low frequency**
**Sophisticated control & DSP**

**Timing**
**(All digital)**

**Back to RF frequencies**

## LLRF Cavity controller

- The LLRF controller is “the brain” of the LLRF system.
- One LLRF controller controls one klystron which powers 24 cavities (i.e. 3 cryomodules = 1 LLRF station)
- 24 cavity prove voltages are “averaged” by the controller.
- Current specifications for ILC cavity gradient control
- ±0.5% amplitude, ± 0.03o phase.
- ±0.5% amplitude, ± 0.5o phase for ILCTA.
- Required from the LLRF controller
- Instrumentation precision electronics (i.e. very low noise ~-150dBm/√Hz).
- Long list of algorithms to be developed and implemented in firmware and software (i.e. for FPGAs and microprocessors).
- Communication interface with slow-controls.

## LLRF collaboration

- Fermilab LLRF is a collaboration of 3 divisions: AD,TD,CD.
- LLRF project leaders: Ruben Carcagno, Brian Chase, Gustavo Cancelo.
- CD effort in LLRF for ILCTA and ILC:
- 3.7 FTEs for ’06, 4 FTEs requested to GDE for ’07.
- AMR, CEPA & CSS collaborators: (e.g. Treptow, Haynes, Kwarciany, Zmuda, Deuerling, Wilcer, Cancelo, Bledsoe, etc.)
- Other collaborators
- DESY
- UPENN
- INFN-Pisa
- INFN-Milano
- PhD students (Helen Edwards program).

## Current LLRF activities at Fermilab

- A0 photo-injector and CC1.
- CC2 at Meson lab (1.7 oK)
- Vertical test facility at IB1.
- Piezo tuner sensor & actuator.
- Lorentz force detuning control.
- Cavity mechanical resonant modes measured.
- Current LLRF activities based on DESY hardware and software.
- Lot’s of effort in understanding and debugging DESY parts.

- CC2 at Meson

## RF studies with CC2

- 31.5 MV/m achieved.
- Note oscillations due to 42 HZ microphonics detuning.
- Manual coupler conditioning.
- Cavity multipacting studies.

## LLRF system in close mode using Simcon 3.1 controller

## DOOCS control software from DESY

- CC2 system working in closed loop

## FNAL-CD centric LLRF activities

- Design of a new LLRF controller (10 channels)
- Will replace current controller designed by DESY. Performance improvement expected.
- Design and implementation of a new I-Q detector at 50MHz to improve the input signal to noise ratio.
- LLRF models and control strategies
- Cavity electrical and mechanical models, Lorentz force and microphonics detuning, klystron nonlinear models, feedback and feedforward control strategies. PhD student (A.Paytyan, G.Cancelo).
- Lot’s of growing potential for this field. (R&D).
- Simulation at the cavity level, cryomodule level (8 cavities), LLRF station level (24 cavities), up to the whole LINAC.
- Interfaces with other CD groups working in simulations.
- Man power requested.

## FNAL-CD centric LLRF activities

- Implementation of algorithms in FPGAs
- We are exploring a new concept using a high level language that allows behavioral and gate level simulations in the same environment.
- Calibration algorithms (future activity).
- Field vector calibration.
- Input and output rotation matrices.
- Loop gain calibration.
- Loop phase calibration.
- Klystron linearization.
- Detuning calculation.
- Q loaded calculation.
- Beam phase and gradient calibration.
- Slow control interface
- boundary needs to be defined, so far controls group doing all the work.

## LLRF future activities at Fermilab

- Support of ILCTA areas
- Control of 1 cryomodule.
- Control of 2 and 3 cryomodules.
- Could use 3 x 10-channel LLRF controllers but at some point we would like to build a 24 to 32 input controller for ILC.
- Horizontal test facility
- Photo-injector moving from A0 to Muon Lab ??
- Other LLRF components to be developed
- Piezo-tuner control hardware and software.
- Cavity motor controller.
- Forward and reflected power monitors.
- RF system supervision (e.g. klystron signals, reference, beam intensity, etc).
- Vector modulators
- Multichannel down-converters.

## Summary

- LLRF for ILC is a very enjoyable intellectual challenge that includes
- Accelerator physics and engineering modeling.
- Accelerator beam and cavity measurements.
- Algorithm design.
- Micro and macro level simulations.
- Feedback, feed-forward, and adaptive control and parameter estimation.
- High quality hardware design.
- RF electronics.
- Firmware and software design
- LLRF project must do R&D and support ILCTA concurrently.