llrf upgrades and comb-2 project

MAC Breakout Session January 18, 20061

LLRF upgrades and Comb-2 Project

Mike Browne

D. Brown, R. Chestnut, J Dusatko, M. Laznovsky, W. Ross, W. Roster, C Yee


Outline

• Improvements in Station Phase Drifts

• Other System Improvements:

• IQA

• AIM

• COMB-2 Project

• Conclusions


LLRF System Issues:• Improvements in Station Phase Drifts

Power Balance Loop New EPICS loop adjust phases of all stations with respect

to one reference station. Maintains a constant relationship between the power levels of all stations.This is fancier, EPICS version of Dmitry ’s power balance loop created by two Operations personnel with some help from our Software section.

Panel shown in next slide

RFP• Added improvements to new RFP Modules in all station

RFPs are now at least 10X less sensitive to temperature variations and have much smaller operating errors.

VXI Crate Temperature Stability• Insulated all old-style racks (Blue Boxes)• Installed new controllers in LER4-3 & 4-5 to reduce

temperature swings.


Power Balance Control Panel


LLRF System Issues• Other System Improvements:

IQAUpgraded to new IQAs for all cavity IQA locations (IQA2 & 3)

• Used 8 channel scanning mode to obtain Fault data for all channels.

AIMAll stations have had their HVPS channels wired to the new AIMs.

• This has been very useful in diagnosing station trips.

GAPFF Designed an adapter board to replace three obsolete ICs used in

the GAPFF modules. This allowed us to produce more GAPFF modules for new stations and spares.

COMBChange to new COMB2 Modules no more overflow problems.

• More about the COMB2 later


LLRF Module Status - IQA

Upgrade to new IQAs

• New Version (R3) IQA were installed as the second or third IQAs in each station. These units can be used in eight channel mode, for displaying fault histories of all channels. IQA number one is set to record and display the klystron output on station faults with the maximum resolution.

IQA failures

• IQA failures have only occurred in older modules. Modules have exhibited solid or intermittent faults. MMS connector or changes in filter attenuation.

– These can cause the Klystron Drive or Klystron Output to be incorrectly reported. This can cause station trips because there are several EPICS loops that depend on these values.

• We have not seen these intermittent failures with the new modules. The new modules use gold plated contacts and filters with no tunable components. Maybe they are just new and problem will occur in the future. We are looking at moving at least the Klystron Drive channel to the second IQA. Swapping it for a less critical signal.


New IQA• We mentioned last year that we are looking at designing a new version IQA.

Bill Ross has had a preliminary look at this and has suggest more robust design with enhanced features that would have no internal coax connectors

• IMPROVE IQ&A ACCURACY AND DRIFT CONTROL(NOTE: LIMITED BY PHASE DRIFT OCCURING IN CLOCK MODULE)(Currently phase drift occurs between 476MHz RF, 471MHz LO, 20MHz Sample Clock,

and possibly group delay of the 5MHz IF band-pass filters.)

• SIMPLE CALIBRATION PROCEDURE, NO CABLE REMOVAL(BASED ON AUTOMATED IN-LAB, PRE-CHARACTERIZATION PROCEDURE WITH

RESULTS WRITTEN INTO FLASH MEMORY)

• IMPROVED VSWR ON RF INPUTS

• ADDITIONAL DIAGNOSTICS

• REDUNDANCY AND PARTIAL SELF CHECKING

• This project would probably take a year to complete. So there is a question if this is the best place to spend our resources.

LLRF Module Status - IQA cont.


LLRF Module Status - AIM

• All stations have had their HVPS channels wired to the new AIMs.

– The AIMS provide wave form monitors for:• Power supply High Voltage• Power supply current slow (shunt) and fast (current transformer)• Power supply ripple.

• This has been very useful in diagnosing station trips.

• We have been able to see several different faults.

– For example:• Power supply ripple• Power drop outs• Crowbar trips

• It is clear that we would like to have even more power supply information available


Example: Fault File – HVPS Problem

– When a fault occurs the system’s history buffers are frozen and are read out

– Below is an example of a problem with a station’s high voltage power supply

RFP’s RF output amplitude is seen suddenly going up before station trips

RFP’s RF Output phase is seen varying. This is typical of the loop trying to cancel the effects of HVPS ripple. Normally the ripple frequency should be primarily 360Hz and 720Hz. In this case there is a large 60Hz component.

HVPS’s voltage and current drop just before trip, the direct loop tried to compensate by raising the drive, klystron went into sat – lowering the gain & causing runaway

Ripple signature


COMB-2 PROJECT

W.Ross , M. Browne

PRINCIPAL ENGINEER AND TASK LEADER

C Yee, M. LaznovskyMajor Contributors


COMB-2 PROJECT OUTLINE

• FEATURES

• BLOCK DIAGRAM

• DSP’ FPGA FIRMWARE IMPLEMENTATION

• Picture

• EPICS Panels

• Future


• Combined I Channel and Q Channel Processing in a Single Module

• Fixes Over-flow and VXI interface bugs present in old Combs

• Flexible ‘DSP’ FPGA design:The filtering algorithms can be changed in the future by re-programming the In-Circuit-Programmable Initialization ROMs. (J-tag port)The initial design implementation uses approximately 30% of the resources of the XC2VP30. We are using the 896 pin BGA version of this part and the “– 7” the fastest speed grade. This should allow considerable flexibility for any future upgrade

• Initial DSP Functionality:Initially, Comb 2 Module has been firmware programmed to perform the full 2-dimensional Comb Filter and Equalization processes, implementing the additional I to Q and Q to I filters which were not available in the earlier version Comb Modules.

• Inter- module Analog Connection:I/Q signals between the RFP module and the Comb Module will be differential analog via the VXI Backplane local bus lines for compatibility with current RFP. A high speed Serial Data Infiniband connector on the front panel is provided for a possible future Digital RFP Module.

COMB-2 FEATURES


COMB-2 BLOCK DIAGRAM


Design implemented in the ‘DSP’ FPGA Firmware:

COMB-2 DSP’ FPGA FIRMWARE


COMB-2


EPICS Hardware

panel


EPICS Panel IIR Coefficients


EPICS Panel Equalizer Coefficients


• The new Comb 2 modules are installed in all stations and have performed well.

• Currently all stations are configured as standard COMB IIR Filter.

COMB-2 Future

The next step is to generate a set of coefficients to produce a comb filter with an asymmetric gain, a single sideband COMB filter. This promises to offer increased stability by having higher gain at the upper synchrotron sideband.


Conclusion• We have made many improvements but, given the present state of

PEP have not yet been able to see effects of our labor.• We will continue make improvements.

1. Develop production version of the LLRF rack temperature control system. There are problems with the Omega temperature controllers. The RTD connections are intermittent causing the heater not to come on at low temperature. We will try a different connection method or change controllers.

2. Try to implement single sideband COMB3. Add new features to our test bench.

• The ultimate goal is to be able to run all the hardware and EPICS loops of a real Station.

• We have recently completed a Klystron Simulator which should behave like a real klystron. It has both gain and phase dependence as a function of High Voltage similar to an actual klystron. Its saturation characteristics also quite closely mimic a real tube. Next we need to have tunable cavities.

4. Use the test bench to test both hardware like the Klystron Linearizer or RFP ripple loop and new EPICS software.


Appendix PEP-II LLRF SystemLab Development System


Appendix A list of Module Failures MODULE Failure Quantity Comments Clock ver 1 low output power 1 Needed upgrade to new amplifiers

40 MHz VCXO 1 intermittent fault, finally failed hard

GAPFF Intermittent IC sockets 1 SN 1 should not be used in system

ADC failure 1 problem was hard to find

RFP ver 3 8 channel DAC 1 intermittent caused multiple trips

IQA ver 2 Filter or MMS Connector 2 intermittent caused multiple trips

MMS Connector 2 Both intermittent, one found during calibration

IQA ver 3 40 MHz Oscillator 1 hardware failure indicator, easy to find

AIM Blown Fuse 2 one occurred on re-cabling, other on power upNo Longer in system ---------------------------------------------------------------------------------------------

COMB ver 1 VXI Interface Failure, 3 ADC failure was repaired, VXI interface was ok

DAC when tested

1 GAPFF, 3 RFPs were swapped out with no improvement in the problem it was intended to fix.


blank

llrf upgrades and comb-2 project

Documents