B. Mikulec, B. Puccio, J-L. Sanchez
Outline
 Constraints influencing interlock design
 Proposed hybrid interlock principle
 Hardware interlock system: BIS
 BIS for Linac4
 BIS for PSB
 Software interlock system: SIS
 External conditions
 Linac4 EC
 PSB EC
 Synchronisation of BIS action
 Summary and open points
21/10/2010
Linac4 BCC - Interlocks
2
Beam Interlock System – Design Constraints (1)
 Main constraints:
 Multiple ‘interlock zones’ due to several destinations,
distinction in ‘operational modes’ not practicable



Destinations for Linac4: L4DUMP, LBE, LBS, PSB
PSB destinations: BDUMP, ISOGPS, ISOHRS, PS
 Should consider PSB and Linac4 interlock systems in parallel!
(PSB is a Linac4 destination; analysis of injection permit is required)
 PSB is (timing) master of Linac4
 Maximise proton delivery to the experiments via ‘External
Conditions’; the user (+beam destination) is calculated for the
current cycle depending on some necessary conditions; this analysis
yields the decision if the ‘normal’ or ‘spare’ cycle should be executed
(or currently ‘tailclipper’ if both not possible); maintain this
flexibility
21/10/2010
Linac4 BCC - Interlocks
3
Interlock Zones
 Linac4 interlock zones
 PSB interlock zones
21/10/2010
Linac4 BCC - Interlocks
4
Beam Interlock System – Design Constraints (2)
 Source should continue pulsing with constant timings to
provide stable beam current (requested also for Linac4
RF feed-forward loop)
 Beam stopper movement too slow for cycle-to-cycle
changes and bending magnet rise- and fall-times too
long for fast reaction to pulsed equipment failures

21/10/2010
Linac2 dump currently only used for (pre-programmed) ZERO
cycles
 To be maintained with Linac4 - ZERO cycles should have
Linac4 dump destination (to be discussed if feasible that prechopper maintains its voltage and chopper does not pulse to
increase chopper lifetime)
Linac4 BCC - Interlocks
5
Beam Interlock System – Design Principle
 Three main ingredients (hybrid system):
1. Hardware interlock system (BIS): reliable, fast


For fast reaction times (to avoid sending the beam pulse shortly
before its creation or to dump part of the pulse if conditions
change)
If considered useful to avoid machine activation
Software interlock system (SIS): flexible
2.


For slow-changing parameters
If some more complex logic needs to be adopted
External conditions (EC): for proton optimisation
3.


Consider user requests and zone/beam inhibits
Method also useful for ring-specific interlocks and beam
intercepting devices requiring shorter Linac4 pulses
Remark: A clear distinction between 1-3 is not always possible; open for discussion...
21/10/2010
Linac4 BCC - Interlocks
6
Hardware Interlock System (BIS)
 Based on Beam Interlock Controller (BIC) modules
already used in LHC and SPS and user interface boards
(CIBU): see presentation B. Puccio
 We propose to use a tree architecture for the Linac4
BIS
 Slave BICs: AND operation of the max. 15 inputs (14+1)

Input 0: SIS, inputs 1-7 non maskable, inputs 8-14 maskable
 Master BICs: AND and OR operations possible

21/10/2010
Inputs: either outputs from Slave BICs or additional
USER_PERMIT inputs
Linac4 BCC - Interlocks
7
Linac4/PSB BIS Layout
 3 Master BICs: ‘Source RF’, ‘Choppers’, ‘PSB Ejection’
 Names describe action of the Master BIC
Master BIC
Master BIC
Master BIC
Source RF
Choppers
PSB Ejection
L4 and L4
Transfer Lines
OK
PSB Injection
Permit
PS OK
Optional BIC
PSB OK
(BIC2)
PSB OK
(BIC1)
21/10/2010
Linac4 BCC - Interlocks
Remark:
No separate BIC,
output from Slave
BIC ‘PSB OK (2)’
8
Reminder: Source Timing
 Approximate timing diagram
 Interlock action possible on source RF and pre-chopper
timings
21/10/2010
Linac4 BCC - Interlocks
9
Master BIC
Linac4 BIS (1)
Source RF
 Master BIC ‘Source RF’ (no slave BIC connected)
 Action: switch off the source RF voltage (~10 μs reaction
time)
 Redundant action: pulse pre-chopper (use timing
signals NX.STOP(START)-PCHOP); ~2 μs rise-time
to assure
correct
chopper
action (for
Master BIC
‘Choppers’ –
see next slides)
21/10/2010
Linac4 BCC - Interlocks
10
Master BIC
Choppers
Linac4 BIS (3)
L4 and L4
Transfer
Lines OK
 Master BIC ‘Choppers’
Action: pulse pre-chopper (use timing signals
NX.STOP(START)-PCHOP); ~2 μs rise-time
 Redundant action: pulse chopper; a few ns risetime
 Disable start timing of PSB RF
 Evaluate destinations
PSB Injection
Permit
PS OK
PSB OK
(BIC2)
PSB OK
(BIC1)
optional
input for PS
injection
permit
21/10/2010
Linac4 BCC - Interlocks
11
Master BIC
Choppers
Linac4 BIS (4)
L4 and L4
Transfer
Lines OK
 Slave BIC ‘Linac4 and Linac4 Transfer Lines OK’
 Input for Master BIC ‘Choppers’
only up to
PSB Injection
Permit
PS OK
PSB OK
(BIC2)
PSB OK
(BIC1)
L4T.MBH.0210
Remark: inputs
marked in grey
have evaluation
of destination in
their front-end
application!


21/10/2010
L4 Magnet Current Status: AQN of main bendings surveyed
with FGCs depending on destination (OR of digital output
signals if AQN outside window ~1 ms before beam pulse)
 Precision to be defined! (need for example 0.5% precision for
LT.BHZ20 to avoid >10% losses in the distributor)
EC only if all rings affected (e.g. user requests; see later)
Linac4 BCC - Interlocks
12
Master BIC
Choppers
Linac4 BIS (PSB Injection Permit) (1)
 Slave BIC ‘PSB OK (1)’
 Input for Slave BIC ‘PSB OK (2)’

21/10/2010
L4 and L4
Transfer
Lines OK
PSB
Injection
Permit
PS OK
PSB OK
(BIC2)
PSB OK
(BIC1)
Check pulsing equipment ~1 ms – 250 μs before beam
production; checks during injection can also be envisaged
(distributor, septum?)
Linac4 BCC - Interlocks
13
Master BIC
Choppers
Linac4 BIS (PSB Injection Permit) (2)
 Slave BIC ‘PSB OK (2)’
 Input for Master BIC ‘Choppers’


21/10/2010
L4 and L4
Transfer
Lines OK
PSB Injection
Permit
PS OK
PSB OK
(BIC2)
PSB OK
(BIC1)
Channels 1 and 2 could be combined; BLMs always active
For the extraction elements simply provision of error status
Linac4 BCC - Interlocks
14
Master BIC
For Completeness: PSB BIS
PSB Ejection
 Master BIC ‘PSB Ejection’
 Action: disable PSB extraction kickers

21/10/2010
Remark: rise-time of magnets too slow to take different action
Linac4 BCC - Interlocks
15
Linac4 SIS
 Reaction time of SIS usually >1 cycle
 SIS can evaluate different conditions, e.g. destination
 Action depending on Master BIC affiliation
 List not exhaustive!
 WIC (Warm magnet Interlock Controllers; PLC-based)
information to be transmitted to SIS
21/10/2010
Linac4 BCC - Interlocks
16
PSB Injection SIS
 Output connected to Slave BIC
‘PSB OK’
 Action defined by Master BIC
‘Choppers’ (pre-chopper,
chopper and PSB RF)
 List not exhaustive!
 WIC information to be
transmitted to SIS
21/10/2010
Linac4 BCC - Interlocks
17
Linac4 EC
 Linac4 EC not to be confused with PSB EC for proton
optimisation; here the aim is to reduce the Linac4
pulse length
 Proposed action: advance NX.START-PCHOP to remove
last 3/4th of the pulse and pulse at the same time the
chopper

BI provides EC signal when equipment is MOVING and IN
 Add equipment that cannot stand full pulse (wire
scanners etc.?)
21/10/2010
Linac4 BCC - Interlocks
18
PSB EC
 Action of ring-specific EC: pulse
chopper to remove beam fraction
for corresponding ring(s) and
switch off PSB RF for that ring
 Action for destination-specific
EC: try to execute ‘spare’ user; if
not possible, EC signal is sent to
input of slave BIC ‘Linac4 and
Linac4 transfer OK’ leading to a
combined prechopper/chopper/PSB RF inhibit
21/10/2010
Linac4 BCC - Interlocks
19
Synchronisation Needs of BIS for Linac4
 For H- source action (switch off source RF):
 Received beam permit only to be considered within
window starting ~1 ms before beam pulse until its end
 For pre-chopper action:
 If beam permit FALSE before NX.STOP-PCHOP
continue pulsing
 If beam permit changes to FALSE after this timing: issue
timing NX.START-PCHOP
 For chopper action:
 Act corresponding to beam permit, but only during the
400 μs window of the beam passage
21/10/2010
Linac4 BCC - Interlocks
20
Synchronisation Needs of BIS for PSB
 For PSB RF:
 Check beam permit just before injection into the PSB
(~200 μs before) and don’t issue the timing for the start
of the PSB RF (for all or only individual rings)
 For PSB extraction kickers:
 Check beam permit at a defined moment just before
charging of the extraction kickers (~10 ms before
extraction)
21/10/2010
Linac4 BCC - Interlocks
21
Conclusions
 Hybrid beam interlock concept based on BIS, SIS and
EC.
 Timings, synchronisation and tolerances need to be
defined in detail
 EDMS document L4-CIB-ES-0001 (1016233 v.0.2) will
be submitted including remarks after today’s meeting
Important remark: The beam interlock system does not
include personnel safety systems!
21/10/2010
Linac4 BCC - Interlocks
22