NLC LLRF Memorandum Rev.010803


Minutes of 8-Pack LLRF Meeting of 121803

Updates & Corrections to Minutes from Meeting of 010604


Present: S. Smith, J. Frisch, A. Young, R. Humphrey, R. Chestnut, S. Clark, R. Fuller, E. Andrikopoulos, R. Larsen, J. Nelson, J. Rock, R. Hall


Purpose: Discuss short and long term goals and requirements for 8-Pack Phase 2.

Discuss present status and urgent tasks.

List short and long term goals.


Major Timeline: This has been set by the 8-Pack schedule, which we MUST meet. Key milestones are:



Rest of Dec. 2003: Downtime

Jan wk 1 through Feb wk 2: Run SLED system

Feb wk 3 through March wk 4: Convert RF system, bake out, reconnect SLED

Apr wk 1 through May wk 4: Run Phase 2

June & beyond: Cut over to 2-pack and PPM tubes (?)



Jan wk 2 through Feb. wk 4: Install, test 2-pack in Bldg 15

Mar wk1 through Mar wk 4: Move, install 2-pack w/ PPM klystrons (2) in NLCTA

April-May 2004: Commission

June & beyond: Cut-over to 2-Pack(?)


Binary Pulse Compression (BPC) tests: Plans not clear at this time. Implications for LLRF appear minimal from system already planned. 2 RF drives, phase shifters instead of present one.


2-Pack cut-over implications for LLRF: reassignment of channels in database; recalibration and checkout.



Short Term Goals





Commission LLRF 8-Pack Phase 2 by March 1 2004.

Commission LLRF 2-pack Phase 1 by March 1 2004.

Anticipate possible cutover to 2-Pack May-June 2004.

Evaluate implications of BPC on LLRF.


Channel specifications for amplitude, phase, stability, dynamic range

Joe produced a summary of the specifications originally requested (See attached).  Ensuing discussion reviewed problems: (1) The peak hold circuits that can respond to a 400 nsec pulse but not a ~20nsec (breakdown) pulse are unusable. (2) The IQA channels need +20dB gain via a new amplifier to be inserted. Some amps on order; more need to be ordered for new units and for spares. (Young).


Summarize channel spec requirements


Review existing hardware channel specs achieved

Specs need review, including amplitude upgrades to IQA
To be done (TBD)

Andy, Steve

Produce written summary of what we have now, assuming all mods to IQAs, SISs


Peak-Hold workaround

Joe suggested a new hardware workaround ahead of the IQA peak-holds, using diode detectors followed by amplification into the existing units. Limit to 16 channels.

Joe, Fuller

Joe to detail design from existing parts, have review, get help from ESD to get system together.


Test existing installed IQA+SISes in system

Need to confirm signals that are implemented through to EPICS w/ Janice.


Just do it.



Simultaneous recording, archiving on fault of 80-100 SIS channels

GOAL: 64 channels supported + spares for ODC, IQA, SIS, ADC, all at the same revision level by March 1.

48 ch instrumented, 64 planned, enough SISs on hand

More IQAs needed (2+2 spares).

IQAs need mods, upgrades.

ODC: need 2+2 spares

Joe confirmed have enough SISes around, but need to scrounge and upgrade for gain. Enough amps for 16 channels on order, 4 are done, amps are backordered until 1/19.


Steve, Andy

Build additional IQAs needed, with mods. Install with additional SISs. Complete database w/ Janice.

Order all missing parts, start builds and mods for all 64 channels

(Young + TBD).


Calibrate all channels

24 were calibrated. Need to re-check since modules removed.

Need 6 days to recalibrate all existing channels (Young).

Need 6 days later to calibrate new channels.


Complete recalibration existing channels ASAP. (Young et al)



Implement all channel names for old, new SIS channels

Also need panel design for new process variables (PV’s)

Needs rework of old and agreement on new names.

60 channels are named out of 64 planned. Of the existing 48 most if not all will stay the same.  Once Steve passes the list to SW they can start databases and panels and other signal support accoutrements. 

Janice w/ help from Ron

Get list to SW and estimate work required asap. (Steve, Ron et al)


Fast processing loop through EPICS

Expansion to Phase 2 must be spec’d

Is designed into system, needs commissioning[1] (Ron).

The loop is ready, waiting on good ADC readings, which Steve reported were working.  When the ADCs work, then the loop can be commissioned.

Urgent to have loop work to back up NIM module interlock logic.

Ops also wants vacuum in the fast trip part of the loop.  Joe suggested a plan to T off the SAM input signals to VME ADCs; then Ron will write code to read these at 10 Hz and update a summary input to the fast loop.  We will need vacuum support (Porter, Hamner) for the T process.

Ron w/ help from Janice

Joe will spec the VME ADC to Fuller to order.


Janice et al can start specing the phase 2 loop once the signal list is in hand (Steve).


Joe & Fuller will coordinate cable plant needs.


119 MHz RF reference signal for LLRF

Needed for compatibility w/ present control system

Joe reported that he has the cables, but needs the quadruplers.

119 will be split and sent to 8 Pack and to NLCTA after X4.  It was agreed that the lines don’t need to be phase stabilized until we want to accelerate beam.




Joe will design/coordinate.


RF generator

Needed for 2-Pack

Andy said they’re still deciding what generator to get. Ray asked that this (and all critical parts) be ordered asap.


Procure, install by 3/1/04


NIM for 2-Pack

Simple additions needed.




Fuller volunteered, given a shopping list from Joe, to scrounge NIM modules  from around site.


RF Control of attenuation, phase through system

Now done manually. Capability is there, needs to be commissioned

We want to meet to discuss this with Sami, et al.  Janice thinks we need a new spec for how the top level (one number per klystron) values are used to calculate each I&Q setting.

Ron, Joe

Evaluate by 1/30/04

Discuss with Sami next week.

Long-Term Goals






AWG Control through EPICS

AWGs not in original specs but now needed. Also needed by PEP.

Need further discussion. Goal is to have a plan by 1/30/04.

Ron, Joe

Retain lab system for initial Phase 2. Evaluate VME modular system & control options by 3/30/04


Fast display of limited number selected waveforms (~4) for tuning.

EPICS can support w/ sep. ring buffers for fast, archival fault data.

We talked ourselves into looking for a hardware solution: patching the signals through the multiplexer to the control room.  This needs to be thought through.

Ron, Steve

Investigate options by 3/30/04; start implementation


Quick scaling of fast displays

EPICS does not currently support. Need the improved tool being developed by SNS.

Ron said right-clicking in the display window allows some axis scaling control.  Attendees were encouraged to try it.

Ron et al

Investigate options by 3/30/04; make plan


Archiver browser retrieval slow

Not sure of reasons but believed to be solvable

The problem is retrieving already archived waveforms.  Janice reported a particularly frustrating 8 hour session of trying to retrieve ~88 waveforms involved much hanging and killing of processes.

She will try to recreate the situation and invite Bob Hall to watch.  She also acknowledged that that day she didn’t try the UNIX line command interface.

Ron et al

Investigate, recommend cure by 3/30/04.


Next steps:

  1. Meet with NLCTA operations, experimenters to further discuss requirements and proposed solutions.
  2. Review manpower issues and resolve conflicts with PEP priorities.
  3. Prepare resource-loaded schedules for all tasks, responsibilities, documentation.


Ray Larsen will serve as point person to establish direction and coordinate progress.

Next Meeting: Will try for January 6th – Possibly at 11 AM in Fuji after regular 8-Pack meeting.


Ray Larsen


Ray showed his strawman schedule. The critical path is getting the hardware revised and built to support Phase II. 


Ray commented we need additional engineering help with the board builds and testing to make the March 31 schedule. Andy was asked to get lists of critical parts ASAP so ordering can be handed off.


Notes by Janice Nelson

Edits by Ray  010804


8-Pack LLRF and Software specs: Updates and modifications to 12/12/2001 specs

J. Frisch

Priorities in this document:


Dropped: Requirement dropped from specification.


Future: Requirement has important future applications, but not needed immediately.


Done: Existing system meets requirement.


Low: Failure to meet requirement will result in reduced performance of 8-pack.


Medium: Failure to meet requirement will require construction of additional “kludge” hardware to allow operation.


High: System cannot operate without meeting requirement.




RF Control – original requirements:


Output power: Original spec was 10dBm.  Functional, no change required. Done


Adjustable frequency control: Original spec  +/- 30MHz. Not implemented. Dropped.


External IQ modulation: Original spec called for external IQ modulation. Partially implemented: using external modulation disables internal modulation. Requirement unchanged to allow waveform shaping, and feedback operation. Low


Fast interlock: Original spec was 100ns to 20dB. Performance not tested, but believed to meet requirements. Done


Slow control: Original spec was external or internal slow control of phase and amplitude with relative stability of 5 degrees. Not implemented except through software (performance not known). Does software implementation provide adequate user interface (single overall IQ control to each Klystron). Medium


Fast phase switch: Original spec was 180 degrees with <10ns to <10 degrees. Does the system meet this? Done?


RF gate: Original spec was 10ns rise and fall time (10dB) for 8 pulses. Does this work with external IQ modulation? Done?


Phase / amplitude steps and ramps: 8 pack spec was 8 steps to 1% I and Q in 10ns with 0.4% stability.  Additional 8 ramps of 50ns to each step for turn on compensation. Steps implemented (unknown performance), ramps not implemented. Requirement modified: Will use external AWG control for this. Dropped.


RF control – additional requirements and clarifications:


Dynamic range: 10dB for full specifications, 20dB for reduced specifications. (Not specified in original specification).


Phase / amplitude control: User control must be in phase and amplitude units. Stability / resolution / matching / accuracy ~3 degrees, 5% power (50% power OK for accuracy). (This is between the 4 pack and 8 pack specs). Low


Phase step synchronization: Phase steps must match to <1ns. (Done with external cables OK).


RF control – status:


System has been heavily modified: mechanical splitters, phase adjustments, etc. This was done to improve user interface relative to slow and awkward software control. Some channels not operating. Overall system is not far from operational.



RF Diagnostics:


High bandwidth readout: Original spec was for switchable system to look at any 2 simultaneous signals on a 1Gs/s scope. 8 bit, 6 bit effective, >1Gs/s, >100MHz bandwidth digital IF processing. System was to be used to calibrate other readout systems. Not implemented.  Future.


Calibration – one time: Original spec was absolute 0.2dB, relative 0.1dB. Spec is met using power meters and thermal power measurement. Done


Waveform diagnostics: Original spec was 100MS/s, 8 bit, 50MHz, digitized on every pulse, read out and saved on breakdown pulses. Some channels implemented, resolution obtained by using ~8 lower bits of 12 bit digitizer (Ugly, but technically can meet spec). Bandwidth spec dropped to 30MHz. (probably met by existing system). Medium


Single pulse peak hold channels: Original spec 3% accuracy (in measured voltage) for 20ns FWHM pulse. Spec specifically allowd using Analog  Modules #611-20 peak hold unit. System used for software feedback and interlocks.  System partially implemented, performance not measured. High


RF Diagnostics – additional requirements and clarifications:


Dynamic range: System must meet specs over 10dB power range. (Not defined in original spec).


Resolution etc: Original spec assumed the high bandwidth readout system would be used for to automatically calibrate all RF channels. In the absence of this automatic calibration all waveform and single point channels are required to meet over the 10dB dynamic range:


Power resolution, short term (minutes) repeatability, waveform point to point matching, noise: 1%.


Power stability long term (days): 5%


Power accuracy with phase change (waveform channels only) 1%.


Power absolute calibration: 20%


Phase resolution, short term (minutes) repeatability, waveform point to point matching, noise: 1 degree.


Phase stability (between signals) long term: 5 degrees.


Phase accuracy (between signals) with power changes: 3 degrees.




Note: I am combining software, driver, archiver and database discussions here.


Waveform signals: Original spec: Record >500pts / channel, 3 events, ~100 channels on each trigger (120Hz). Archive all data on a trip. In principal works, but not actually operational at this time. (should be ready to be commissioned now).


Single pulse acquisition: Original spec: Collect data from analog and digital in devices, record on trip. Control analog and digital output devices at 120Hz under feedback. Provide unique pulse ID to collected data. Provide watchdog output pulse.  . In principal works, but not commissioned. (waiting for hardware).


GPIB: Original spec: Interface to GPIB based scopes. Done (approximately )


Software – Additional requirements:


Fast (>1Hz) control and waveform readbacks. (Or use hardware scope and cables).


Online user scaling of waveform displays.


Add and modify channels (of existing types) with quick (~1 day) turn around.


Archiver: In principal works, but not operational (discussion).


[1] Post-meeting note: Information from Janice via Joe is that system crashes often and needs work.