SNS Integrated Control System
SNS Timing System
EPICS Workshop
April 28, 2005
Coles Sibley
Dave Thompson
SNS Global Controls
SNS Integrated Control System
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
SNS Integrated Control System
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.
SNS Integrated Control 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
SNS Integrated Control System
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
SNS Integrated Control System
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.
SNS Integrated Control System
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
SNS Integrated Control System
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).
SNS Integrated Control System
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
SNS Integrated Control System
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
SNS Integrated Control System
Application: Ion Source Control
ExtractEnd Injection
0 2 ms1 ms 6 ms4 ms 7 ms5 ms 8 ms3 ms
Beam OnSource RF
Cycle Start
Source On
Delayed Source On
Cycle Start
Beam On
Event Link
Growth
Growth
Warm LinacLLRF
RFQ
SNS Integrated Control System
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
SNS Integrated Control System
Application: Linac RF Control
ExtractEnd Injection
0 2 ms1 ms 6 ms4 ms 7 ms5 ms 8 ms3 ms
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
SNS Integrated Control System
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
SNS Integrated Control System
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
SNS Integrated Control System
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)
SNS Integrated Control System
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
SNS Integrated Control System
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 Integrated Control System
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
SNS Integrated Control System
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