PSB ring inhibit in the Linac 4 era
Summary of discussions involving (mainly):
Jose-Luis Sanchez Alvarez
Philippe Baudrenghien
Gregoire Hagmann
Matthias Haase
Ioan Kozsar
Christophe Martin
Bettina Mikulec
John Molendijk
Mauro Paoluzzi
Silvia Zorzetti
More people to be consulted!
A. Blas
PSB LIU meeting 07/03/2013
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PSB ring inhibit in the Linac 4 era
Why should one inhibit a PSB ring
• An operator asks for 0 turn to be injected (setting on OP display)
• A fault is detected (external-conditions inhibit chain)
• An experiment wants to stop the beam (external-conditions inhibit chain)
What response time is expected
• 0 turn setting
=>
1 cycle (the next one typically)
• external-conditions => 2 cycles (after the “next” cycle)
• Fault (endangering acceleration or extraction) =>
A. Blas
PSB LIU meeting 07/03/2013
ASAP (not yet implemented)
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PSB ring inhibit in the Linac 4 era
The different ring-inhibits
A. Blas
0 turn setting
only changes counters’ value
(until now)
external-conditions
edits the PLS telegram where
present and next are defined
=> thus implies more delay
than the “0 turn” setting
Fault
Not yet implemented
PSB LIU meeting 07/03/2013
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PSB ring inhibit in the Linac 4 era
Response to a fault
Faults may occur at any time after the settings for the actual cycle have
been established.
Only the faults endangering the acceleration or the extraction are
considered.
A. Blas
Fault appears:
What to do:
Before injection
Skip the ring with the
distributor or chop the beam
During injection
Switch to the next ring with
the distributor or chop the
remaining beam
After injection
Progressive loss into the ring
(with the rf) or extract to the
dump (?)
PSB LIU meeting 07/03/2013
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PSB ring inhibit in the Linac 4 era
For a proper injection from L4 into the PSB the following elements need to be
synchronized:
1. Pre-chopper
2. Chopper
3. Cavities’ feed-forward (if needed)
4. Energy modulation cavities
5. Distributor
6. Injection kickers
7. Transverse Painting bumpers
8. Magnetic correction in each ring
9. LL-RF
N.B.: all these elements (apart from the pre-chopper) can be programmed on a ring-byring base, meaning that advancing a start pulse allows for a ring skipping.
A. Blas
PSB LIU meeting 07/03/2013
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PSB ring inhibit in the Linac 4 era
In case a ring would to be skipped - with the distributor - while the injection has started,
the following elements could not follow:
1. Pre-chopper
2. Chopper
3. Cavities’ feed-forward (if needed)
4. Energy modulation cavities (20 us rise time)
5. Distributor
6. Injection kickers
7. Transverse Painting bumpers
8. Magnetic correction in each ring (some ms rise time)
9. LL-RF
A. Blas
PSB LIU meeting 07/03/2013
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L4 to Booster synchro
Injection Timing – what is needed:
Pre-chopper
Global Start/Stop Timing
Chopper
Unique Start or Start for each ring
+ chopping table
Cavities’ feed-forward
Synchronous with chopper
Energy modulation cavities
(longitudinal painting)
Unique Start or Start for each ring
+ function (needs to start and end at zero for
each ring)
Distributor
Start for each ring (+ tail dump)
Injection kickers
Start for each ring
Transverse bumpers (painting)
Start for each ring
Magnetic correction in each ring
Unique start or Start for each ring
+ function (or offset) – does not have to be
precise
LL-RF
Start for each ring
A. Blas
PSB LIU meeting 07/03/2013
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L4 to Booster synchro
SINJ
C0
Start
Pre-chop
Start
Pre-chop
START
Counter
SR4
Nb Turns
R4
Nb Turns
R3
START
Counter
SR3
START
Counter
SR2
Nb Turns
R2
Nb Turns
R2
START
Counter
START
Counter
START
Counter
INJ
REF
1 MHz
A. Blas
SR1
RF synchro of
all PSB rings
PSB LIU meeting 07/03/2013
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L4 to Booster synchro
Timing summary:
Information required in L4 for a smooth injection into the PSB:
Reference clock + single start-injection pulse + number of turns
In the PSB, a start injection pulse is required in each ring.
Although the Linac 4 doesn’t strictly require a start corresponding to each ring,it can be
set to work with.
This would be an advantage for monitoring purposes (analysis on oasis for instance)
There seem to be an agreement that a ring-by-ring time windowing would be
beneficial for the entire L4 –PSB chain
A. Blas
PSB LIU meeting 07/03/2013
9
PSB ring inhibit in the Linac 4 era
Switch to the next ring not compatible
with magnetic correction -> Chopping is
OK
Response to a Fault (part 2)
Fault appears:
What to do:
Before injection
Skip the ring with the
distributor or chop the beam
During injection
Switch to the next ring with
the distributor or chop the
remaining beam
After injection
Progressive loss into the ring
(with the rf) or extract to the
dump (?)
Switch to the next ring not compatible
with longitudinal painting and
magnetic correction -> Chopping is OK
A. Blas
PSB LIU meeting 07/03/2013
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PSB ring inhibit in the Linac 4 era
Possible faults listed as
“external conditions” that do
not concern all rings
(all rings = BIS issue)
The rf faults could/should be
added to this list.
As mentioned before , these
faults are presently treated
after 2 cycles.
A. Blas
External Conditions:
Ring inhibited
BE1.KFA
1
BE2.KFA
2
BE3.KFA
3
BE4.KFA
4
BT1.KFA10
1
BT4.KFA10
4
BT2.KFA20
1+2
BT1.SMV10
1
BT4.SMV10
4
BT2.SMV20
1+2
BT1.BVT10
1
BT4.BVT10
4
BT2.BVT20
1+2
PSB LIU meeting 07/03/2013
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PSB ring inhibit in the Linac 4 era
With the increase of the injected beam energy and intensity, the response time to a
“external condition” fault becomes difficult to accept.
There is a need for a real time beam inhibit.
One approach, that seems appealing (to some), is to chop the beam of the
incriminated ring – with no delay
• The PSB timing remains the same, only the chopper disables the ring
• The rf of the given ring is disabled as a second security.
• When this emergency measure has been taken, the SIS (software Interlock
System) disables the ring in a proper way by applying zero turn.
• No issue with magnetic correction, nor with the longitudinal painting (as
compared to an emergency pulse that would switch to the next ring)
A. Blas
PSB LIU meeting 07/03/2013
12
PSB ring inhibit in the Linac 4 era
Summary
Response to a fault jeopardizing the injection or acceleration:
Ring inhibited with no delay
Action: chopper and PSB RF + SIS applying 0 turn after processing time
Response to an experiment ceasing to require beam (also called external condition?):
Go to spare cycle
or to zero cycle
or ask for 0 turn
All this in a controlled way with all machine parameters re-computed accordingly (no
emergency actions required)
Response to a zero turn command from the operation:
Calculate all timings and functions for a proper operation (1 cycle duration?)
A. Blas
PSB LIU meeting 07/03/2013
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PSB ring inhibit in the Linac 4 era
Hardware implications
• Real time inhibit at the chopper level (1 per ring)
• Real time inhibit on the PSB LL-RF (1 per ring)
• Centralize all detected-fault signals and determine the action depending on the
cycle’s requirements in real time (RF interlock interface to be designed by Silvia
Zorzetti)
A. Blas
PSB LIU meeting 07/03/2013
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