sns timing system epics workshop april 28, 2005 coles sibley dave thompson sns global controls

SNS Integrated Control System

SNS Timing System

EPICS Workshop

April 28, 2005

Coles Sibley

Dave Thompson

SNS Global Controls


Design Decisions

MPS and Timing systems are tightly integrated. Timing systems should “RESPECT” machine protection system beam power and pulse width limits to not “challenge” MPS system.

Timing system will run at 60 Hz. (but don’t preclude the possibility of 120 Hz).

Super cycle will be 10 seconds (600 cycles, 0.1 Hz rep-rate resolution).

As much as possible should be done in hardware.

As little as possible should be relegated to the client IOCs.

Synchronous with Ring RF, not linac RF

System hardware design from RHIC


Machine / Beam Mode Definitions

Machine Mode defines where the beam goes– MEBT Beam Stop

– CCL Beam Stop

– Linac Dump

– Injection Dump

– Ring

– Extraction Dump

– Target

Beam Mode defines allowable beam charge or power– Pilot pulse (10 usec)

– Diagnostics pulse (50 usec)

– Tuning pulse (100 usec)

– Full Pulse Width (1 msec)

– Full Power (Depends on Dump)

Machine mode selected by Key switch in control room, Beam Mode selected by Key or software. Switches read by MPS PLC system and distributed through timing system.


Timing System Components

Ring RF

TimingReferenceGenerator

NeutronChoppers

ACLine

SNS EventLink

Master

*32 PLL(33 MHz)

SNS RealTime Data

LinkMaster

10 MHzCrystal

Osc.

TimingSlave

(V124S)

MachineProtection

System

ICS IOC'sSNS Utility

Module

LEBTChopper

*4 PLL(64 MHz)

ExperimentalHalls

Diagnostics

RTDLEventLink

MasterTiming IOC

GPS

SNS Time StampsBeam data

RF GatesExtraction KickersTxHV Gates

High resolution timestampsMachine Modes

SNS TimestampsRemote ResetSynchronous ISR’s

Beam DelayBeam PhaseMicro pulse widthMacro pulse width

SNS Time stampsDelaysGatesTriggers

Timing SystemHardware

Timing System Users Experimental Systems

Subsystem Hardware


ExtractMPS Inhibit

EventLink

End Injection

Timeline (from the timing system point of view)

Real-TimeData Link

(RTDL)

0 2 ms1 ms 6 ms4 ms 7 ms5 ms 8 ms3 ms

Anytime

Anytime

Informational Events, non critical timingTime Critical Events, (soft events disabled)

RTDLTransmit Snapshot,

1Hz, 6Hz, etc…

RTDL Valid

RTDL parameter transmission

(for next cycle)

beam accumulation

RF & High Voltage Events

MPS Fault

System xxx Trigger Events

(Alternate) Cycle Start

Machine

+60 Hz ZeroCrossing

-60 Hz ZeroCrossing

Line-SynchReference

Clock

Beam On

Cycle Start

Beam On Range Beam On Range

Allowed Range for Variable Triggers

Extraction Kicker Charge

MPS Post Mortem


RTDL Sequencer

Runs at 60 Hz. Driven by the “RTDL Valid” Event interrupt.

Loads the RTDL frames for the next cycle (the cycle after the upcoming “Cycle Start” event, including:

– Time of next Cycle Start (From GPS + ~162/3 msec) for time stamps

– Ring revolution frequency (from counter module)– Line crossing phase error (from timing reference generator)– Beam flavor parameters (Beam profile)– Machine and Beam Mode (MPS Mode Masking)– Last frame is 24-bit CRC on all RTDL data.

Writes correction term (based on measured event-link clock speed) to timing reference generator.


Event Link Sequencer

Runs at 60 Hz, driven by the “RTDL Valid” event.

Enables gates for variable rep-rate events that are scheduled to fire on the next machine cycle.

Handles the “bookeeping” tasks required for setting new rep-rates.

Actually, a set of EPICS “genSub” records.

Computes the rep-rate “patterns” used by the Event Link Sequencer to schedule which events should occur on each cycle.

Can also be used on “Client” IOC’s to do local rep-rates.

Rep-Rate Pattern Generator


Variable Rep-Rates — genSub Record

Inputs

A. Desired Rep-Rate (double)

B. Constraint Pattern (structure)

C. V124S Gate Address (card & signal)

D. Mode selector• 0 = “Fixed” (ignore pattern)• 1 = “Variable” (use pattern)

E. Offset from Constraint Pattern (long)

–n: Precede constraint pattern by n pulses

+n: Follow constraint pattern by n pulses

0: No offset (pattern must be coincident with constraint pattern)

Outputs

A. Actual Rep-Rate (double)

B. Rep-Rate Pattern (structure)

Note: Constraint pattern can come from another “repRate” genSub record (e.g. for the gate this gate depends on) or from a combination of patterns (computed by another genSub record).


Application: Beam Control

Event Link

} MPS Inputs

Cycle Start

Beam On

Source RF

Delayed Source RF

To Source

V124S

Trigger Control Chassis

RFQ

To RFQ

From RFQ LLRF Controller

To Chopper

Hardware interface between MPS and Timing

Auto Reset

Latched

MPS PLC


Event Link Monitor

Monitors event in a supercycle

Compare with event link sequence, fault on difference

Hardware check against software errors

Hardware read back for pattern generators


Application: Ion Source Control

ExtractEnd Injection


Beam OnSource RF

Cycle Start

Source On

Delayed Source On

Cycle Start

Beam On

Event Link

Growth

Growth

Warm LinacLLRF

RFQ


Application: Linac RF Control

Requirements

RF Gates should always end at “End Injection” event. Increasing the gate width decreases the delay (and vice versa).

Low-level RF gate should come on about 100 Sec before beam (300 Sec in super-conducting linac).

HV power supplies should come on about 100 Sec before Low-Level RF.

Variable rep rates replaced with fixed events– 1, 2, 5, 10, 20, 30, and 60 Hz– Modulator HV Power supplies need an upgrade before 31 Hz or higher

permitted

Individual RF gate widths adjustable but sets a constraint on maximum beam pulse width


Application: Linac RF Control

ExtractEnd Injection


Beam OnCycle Start

Source On

Beam On

Event Link

RF & High Voltage Events

Warm LLRF

Warm HPRF

Cold LLRF

Cold HPRF

Source RF

RF Gate Relationships


Typical User Defined Beam Flavors

Reconfiguration requires beam off, flavor integrated charge and power recomputed, beam scheduled power calculated against machine/beam modes.

Flavors used by LLRF and Ring RF for feed forward loops.

1 - Beam Off 2 - 10 usec, (Chopped) (Fast faraday cup) 3 - 50 usec , (Chopped) (All wire scanners, faraday cups) 4 - 100 usec , (Chopped) 5 - Physics , (Unchopped) 6 – Arbitrary 1 msec gates, 50 usec beam 7 - Reserved 8 - Normal, ie. 1060 turns, 50 usec ramp up


LEBT Chopper Pattern Generator

1 msec

16.67 msec

645 nsec 945 nsec50 usec

CycleStart

Ring RF PLL SignalPhasedelay

Mini Pulseduty factor

75 %

65 %

divide by "n"

n=2, I = I0/2

Start WidthMini Pulse

Width

End Width

MacroDelay

MacroPulse Width

Ramp upTime

Ramp downTime


Beam Profile Requirements

Ring Commissioning– 10 turns, 1 per 100usec (next generation of chopper)– Nominal beam to Linac Dump (Beam flavor 1)– Single turn (beam flavor 2)– Chopped beam to ring (beam flavor 3)


Pattern Generator – CD4 in 2006

Fixed RF rep rates limited to < 30 Hz

1 Hz beam, < 50 usec gate width thru Dec 2005

LEBT Chopper commissioned, Beam gate < 1msec, integrated pulse width < 50usec

(LEBT fails with fulll width beam)

Beam RR and PW must fall in safe operating envelope (May 2006)

Safe Operating Limits

0.1

1

10

100

0 200 400 600 800 1000 1200

Turns (945 nsec / turn)B

ea

m R

ate

1.4 MW envelope (Target)

200 KW envelope (Injection Dump)

7.5 KW MEBT_BS, CCL_BSLDmp, Ring, EDmp

Safe Operation

Beam Diagnostics


Beam Scheduling Post CD4

SNS runs in loss limited mode (<10-4), Scale back in power until loss limits met.

All beam on after trip of > 5(?) min, pilot pulse and power ramp up required

Target has limits on machine trips, 25(?) fast and 5(?) slow per day. Requirements not defined for bad machine days.

Target Requirements– < 100 kW, no restrictions– > 100 kW and beam off < 30 min, no restrictions– > 100 kW and beam off > 30 min, linear ramp in power for 10 min.

One diagnostics pulse per super cycle allowed (Monitor injection phase painting) implies pulse to pulse scheduling.

Second target station, More pulse to pulse beam mode scheduling required


SNS AC Line is being Characterized using Filter for Neutron Chopper Response

Line synch installed in controls lab timing system for distribution to neutron chopper lab.

GPS-based filter with slew rate limit being studied

Beam Phase with line delay from 0 to 800 usec in 50 usec increments (2 beam trips) +/- 10deg RFQ

Minimal Effect on Beam from 0 to 800usec delay

Six day line frequency measurement

60.0 Hz

60.1 Hz

59.9 Hz

Deviation from Grid in usecs

Deviation in slew rate in mHz/sec

500usecs

Limiting Slew Rate results in wide frequency range


New Requirements

Use SLS and Diamond timing hardware (Timo Korhonen)

3 – D beam bunch shape measurements

12 degree longitudinal length, 402.5 MHz (83 psec)

Need ~1 psec stability,

1 to10 psec resolution

Use 402.5 or 805 MHz LLRF Reference line as input clock

Synchronize Beam-On pulse using SLS Hardware

sns timing system epics workshop april 28, 2005 coles sibley dave thompson sns global controls

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