# Presentation: 014194

## LLRF & SCRF Instrumentation

**Brian Chase**
**March 15 , 2005**

- B. Chase - Proton Driver Director's Review

- March 15-17, 2005

## Outline

**RF Control System (LLRF) Requirements**
**Options for Implementation**
**Cryomodule/warm cavity Instrumentation**
**Costs**
**Conclusions **

- B. Chase - Proton Driver Director's Review

- March 15-17, 2005

## LLRF Functionality

**Provide a phase-stable RF reference subsystem signal to correctly phase each cavity**
**Maintain cavity field stability within ±0.5% amplitude and ±0.5° phase**
**Resonance control of both warm and cold cavities**
-   the  cavity's resonant frequency  shifts due to RF heating, beam loading,  microphonics, Lorentz force detuning, cryogen pressure changes, and variations in klystron high voltage.
**Maintain control during beam loading transients**
**Handle state control and exceptions**
**Provide diagnostics **
**Provide and respond to interlocks**

- B. Chase - Proton Driver Director's Review

- March 15-17, 2005

## SNS LLRF

- Each VXI crate and downconversion chassis serves two SCL RF systems.  Full system tests this summer.

- B. Chase - Proton Driver Director's Review

- March 15-17, 2005

## FNAL LLRF

- MI-60 Control Room for the Main Injector, Recycler and Tev

- B. Chase - Proton Driver Director's Review

- March 15-17, 2005

## LLRF Comparison

|  | Fermilab | DESY | SNS |
| --- | --- | --- | --- |
| FE OS | VxWorks | Solaris | VxWorks |
| ContrSys | ACNET | DOOCS | EPICS |
| Platform | VXI | VME | VXI |
| DSP | AD SHARC  | TI  | none |
| FPGA | Altera | Xilinx | ?? |

- B. Chase - Proton Driver Director's Review

- March 15-17, 2005

## The Plan

**Get a test system from DESY up and running at AO**
**Test fast phase shifters at A0. A single cavity test will be instructive**
**Multiple cavity tests at SMTF**
**Evaluate SNS and new DESY modules as they become available**
**Parallel design of RF phase reference system**
**Finalize design with collaborators and or vendors**

- B. Chase - Proton Driver Director's Review

- March 15-17, 2005

## The Good News

**Control of SRF is a mature science/art**
- More than a decade of well documented experience
**Digital radio technology is driven by the telecom market and is developing at a rapid rate.  It is now good enough **
- Getting faster, smaller, lower power, cheaper
**FPGA technology is driven by everything.  It is now good enough**
- Getting faster, smaller, lower power, cheaper
**ILC is a driving force for LLRF collaboration**
- SMTF and the Proton Driver may be an interesting test bed for the ILC in addition to the XFEL

- B. Chase - Proton Driver Director's Review

- March 15-17, 2005

## More Good News?

**The Proton Driver will not be a boring LLRF project!**
**The fast phase shifters are new technology and are central to the success of this accelerator**
- Small signal BW is low
- Slew rate is slow 1 deg/us
- Single cavity simulations look promising
**The loaded Q is much higher than SNS**
- We are counting on the Piezo tuners to work

- B. Chase - Proton Driver Director's Review

- March 15-17, 2005

## Slide 10

- B. Chase - Proton Driver Director's Review

- March 15-17, 2005

## A Possible Structure

- B. Chase - Proton Driver Director's Review

- March 15-17, 2005

## Frequency Agile Phase Reference System

**Lorentz detuning of the cavities takes reactive power to correct.  This causes higher voltage and current in the power coupler and takes real power from the klystron that just ends up in the circulator load.  Piezo tuners work to correct this but the Tesla cavities have only a 500 Hz range.  With a 3ms pulse, the cavities could detune by 2 kHz. **
**If cavities track together, there is no need to stay at a fixed frequency for the linac.  So, program the reference line to track the mean trajectory of the natural cavity frequency.  Spoke Resonators will not track as they detune much less.**
**2 kHz of dF will only cause 1.4 deg phase change along the length of the Linac.  This can be programmed out.**

- B. Chase - Proton Driver Director's Review

- March 15-17, 2005

## LLRF Rack Space

**Number of LLRF/klystron systems 13{33}**
**Max number of cavities/klystron 48**
**Support for 36 cavities 2 crates (3 for 48)**
**19 crates for linac   13 racks**
**Piezo controllers;**
-  1 rack for 36 cavities
-  26 racks for Linac
** **

- B. Chase - Proton Driver Director's Review

- March 15-17, 2005

## R&D Efforts and Risks

**Development of new LLRF hardware and software**
**Testing at SMTF with reference line**
**Single klystron driving multiple SRF cavities; field control with fast phase shifters **
**Single klystron driving multiple cavities (warm and cold) in Linac front end**
- Different Qs controlled with one klystron feedback loop
- Different cavity types will have different beam loading
- Warm cavities have power dependent resonant frequencies.  These will vary between individual cavities and cavity types.  Warm cavity types will have different initial frequencies
- SRF cavities cannot be regulated without beam loading

- B. Chase - Proton Driver Director's Review

- March 15-17, 2005

## Instrumentation = Cables

**Over 16,000 cables in 31 waveguide chases!**
**Over 10,000 3/8 heliax**
**Average runs of 150 ft**
**Most of these signals are << 1MHz BW**
- R&D to use twisted pair where possible;		 direct or down converted
- Use 7916A RG6/U where possible $0.10/ft Quad Shielded.  Comes in 10 cable snakes (rad hard?)
- Explore tunnel electronics (rad hard) to fiber

- B. Chase - Proton Driver Director's Review

- March 15-17, 2005

## Instrumentation Processing 

**Single rack per wave guide chase**
- Common crates (VME)
**BPMs     290****	****	****	**** @$2k**
**HOM     1000****	****	****	****@ $200 **
**Spark detectors  2500****	****	****@$25**
**Lots of other stuff 5000****	****	****@$25**
**$~3M  **
**Lots of processing - To do this right(save $$) **
- Coordinated effort between subsystems
- Competing design teams through prototype stage

- B. Chase - Proton Driver Director's Review

- March 15-17, 2005

## LLRF Hardware Costs

**LLRF **
- Base cost per klystron
- 2 VXI crates, 2  Slot0 controllers,Timing card,  RF Control Module, rack, etc.  $30k
- Cost per cavity
- 1/2 Cavity Module,    $2k
**Resonance Control**
- $2k/cavity for Piezo actuators and control or other tuner control
**Reference and reference line**
- Reference oscillators $70k
- Reference line $100k
**Total ~ 13 * 30k + 453 * 4k + 170k ~ $2.5M**

- B. Chase - Proton Driver Director's Review

- March 15-17, 2005

##  CONCLUSIONS

**The PD RF Control System is technically feasible**
- Many years of experience at FNAL with digital LLRF and some SRF
- Many years of well documented experience with SRF at other labs.  SNS and DESY are willing to help!
**Costs have a reasonable bracket**
**The Risks are Low for most of the Linac**
**R&D is required for the Linac front end @ SMTF**
**We have a working prototype from DESY in our lab (MTF)**
**Instrumentation; been done before - cost reduction**

- B. Chase - Proton Driver Director's Review

- March 15-17, 2005