LLRF FOR CHOPPER
Grégoire Hagmann
Philippe Baudrenghien
BE/RF/FB
February 24th, 2013
LLRF Linac 4, G.Hagmann
Block Diagram
Chopping
«pattern»
2
• Plates delay adjustment
• Monitoring (Waveform & chopping time)
• Interlocks
LLRF Linac 4, G.Hagmann
Location “CDU”
Rack AY01
3
LLRF Linac 4, G.Hagmann
4
Rack AY01
• BIS cables arrivals
• Need of space for
transition patch panel : 2U
• Need 1U Beam permit patch
=>TE/MPE/EP
• Need 1U User permit parch
Who? BE/RF or TE/MPE?
• Position for BIS patch-panels?
Transition patch needed
No Burndy on VME board
LLRF Linac 4, G.Hagmann
5
Chopper Limitations
• Max Chopper pulse length : 500us (programmable)
• => need monitoring (start counter at “source on”)
• => Drive off when “source off”
• => Drive off when >500us (timeout) from “source on”
• => What if timeout? Alarm? User Permit False? OP action?
<500us
LLRF Linac 4, G.Hagmann
Ring blanking
6
Discussion with A.Blas
• Compatible with booster?
(Magnetic compensation in RF lowlevel…)
• Reaction time for ring interlock?
LLRF Linac 4, G.Hagmann
Ring blanking
During the Linac 4 pulse (window), Can one ring be inhibited?
And does it need immediate action?
If YES :
→ “Dynamic” Ring blanking
→ Need timing ring identification
→ Need 1 chopping pattern table per ring
→ Need accurate HW timing(s) for re-synchronization
If NO :
Can 1 ring interlock be interpreted like a change in nb of turn of the ring?
If YES:
→ High level software re-compute chopping pattern (new settings)
→ Load of the new chopping pattern and played for next cycle/user
If NO:
→ No change in chopping pattern table
→ Need ppm information for which ring are “played” (Timing or with Software)
7
8
LLRF Linac 4, G.Hagmann
L4-Booster synchronization
Beam must be chopped during the 1us PSB ring change
References document :
• Synchronization between Linac4 and the PS Booster
CERN-ATS-Note-2010-052
TRF ≈ 2.84ns
2 solutions :
• Synchronization for every Ring
RF Linac4
• “Dynamic” ring blanking feasible
HW timing
• Accurate synchronization signals => accuracy?
• 1 “pattern” table for every ring
• Table switching
• 1 single synchronization after “Source On” timing start
• No “Dynamic” ring blanking (or more complex => to be studied)
• 1 accurate synchronization signal
• 1 “pattern” table for all rings
• No distinction if 1 or more ring => “just” one chopping pattern
RF frequencies (L4 & booster) stability?
Tr << TRF
9
LLRF Linac 4, G.Hagmann
L4-Booster synchronization
3 Proposals :
• 4 timings CTRV (next Ring identifier)
Re-synchronization for
every ring
(Meeting Dec 16th 2011)
• 1 accurate HW timing at every ring start
• Dynamic ring blanking feasible
• Safer, consistency between Chopper and PSB
injection Distributor
• 4 accurate HW timings, 1 per ring (ring start)
• Dynamic ring blanking feasible
• HW More complex, More cabling
• 1 timings CTRV (source on)
• 1 accurate HW timing at the window start (linac 4 pulse)
• 1 pattern table for 4 rings
• No Dynamic ring blanking
• Need new setting (at the next cycle) for new pattern
LLRF Linac 4, G.Hagmann
L4-Booster synchronization
exemple
• 4 timings CTRV (next Ring identifier)
• 1 accurate HW timing at every ring start
• Dynamic ring blanking feasible
• Safer, consistency between Chopper and PSB
injection Distributor
Ring 1 start
Ring 2 start
Ring 3 start
Ring 4 start
HW timing
10
LLRF Linac 4, G.Hagmann
CDU details
11
LLRF Linac 4, G.Hagmann
RF Interlock
crate
From & To BIS
(No fiber anymore)
CDU details
12
Start & Stop independent adjustable
delays for all plates
LLRF Linac 4, G.Hagmann
CDU details
• VME board “RF” type
• BIS input & output on LEMO
• EPG.0B.304.HLN (or similar)
• XXX.1B.308.XXX
• RF Interlock
• 1 interlock or 2 interlocks (1 per chopper) ?
• From AY01
• Optical, Multi-mode, ST
• Same for cavity-controller PIMS, CCDTL…)
• TX pulses monitoring
• Veto
• Diagnostics
13
LLRF Linac 4, G.Hagmann
14
BIS «gating»
BEAM INTERLOCK SPECIFICATIONS FOR LINAC4, TRANSFER LINES
AND PS BOOSTER WITH LINAC4 (L4-CIB-ES-0001 rev.0.3) :
Gating ON
 Gating with timing from BE/CO (CTRV) ?
 Fail safe?
 Gating rather in the BIS than CDU ?
Gating OFF
Chopper forced OFF
BIS even unlatched
BIS event Latched
LLRF Linac 4, G.Hagmann
New special «BI» timing
• Addition of a new «CTRV like» timing feasible
• Not fail safe
• 2 solutions:
• Implemented HW similar to the BIS signal
• => Fixed implementation
• => Simple functionality
• => “Robust”
• => Timing always needed
• Through FPGA
• => Flexible implementation
• => Complex functionality possible
• Timing Hardware?
15
LLRF Linac 4, G.Hagmann
16
New special «BI» timing
Chopper ON
Chopper OFF
Chopper ON
(latched)
LLRF Linac 4, G.Hagmann
RF Interlock
Power side (PLC) :
HFBR-1414
« Phoenix contact » module open
(example of a design)
LowLevel side :
•
•
ST optical receiver on CDU board
By-pass input foreseen for “debug & tests”
« Phoenix contact » module closed
17
LLRF Linac 4, G.Hagmann
18