b. mikulec , b. puccio , j-l. sanchez

Proposal for a Beam Interlock System for Linac4, Transfer and

Measurement Lines as well asPSB with Linac4

B. Mikulec, B. Puccio, J-L. Sanchez

Linac4 BCC - Interlocks 2

OutlineConstraints influencing interlock designProposed hybrid interlock principleHardware interlock system: BIS

BIS for Linac4BIS for PSB

Software interlock system: SISExternal conditions

Linac4 ECPSB EC

Synchronisation of BIS actionSummary and open points

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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

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Interlock ZonesLinac4 interlock zones

PSB interlock zones

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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 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 pre-chopper maintains its voltage and chopper does not pulse to increase chopper lifetime)

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Beam Interlock System – Design PrincipleThree 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 activation2. Software interlock system (SIS): flexible

For slow-changing parameters If some more complex logic needs to be adopted

3. External conditions (EC): for proton optimisation 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...

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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 BISSlave BICs: AND operation of the max. 15

inputs (14+1) Input 0: SIS, inputs 1-7 non maskable, inputs 8-14

maskableMaster BICs: AND and OR operations possible

Inputs: either outputs from Slave BICs or additional USER_PERMIT inputs

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Linac4/PSB BIS Layout3 Master BICs: ‘Source RF’, ‘Choppers’, ‘PSB

Ejection’Names describe action of the Master BIC

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Remark:No separate BIC,output from SlaveBIC ‘PSB OK (2)’

Optional BIC


Reminder: Source TimingApproximate timing diagram

Interlock action possible on source RF and pre-chopper timings

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Linac4 BIS (1)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

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to assurecorrectchopperaction (forMaster BIC‘Choppers’ –see next slides)


Linac4 BIS (3)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 rise-time Disable start timing of PSB RF Evaluate destinations

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optionalinput for PSinjection permit


Slave BIC ‘Linac4 and Linac4 Transfer Lines OK’Input for Master BIC ‘Choppers’

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 BIS (4)

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only up to L4T.MBH.0210

Remark: inputsmarked in greyhave evaluationof destination intheir front-end application!


Linac4 BIS (PSB Injection Permit) (1)Slave BIC ‘PSB OK (1)’

Input for Slave BIC ‘PSB OK (2)’

Check pulsing equipment ~1 ms – 250 μs before beam production; checks during injection can also be envisaged (distributor, septum?)

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Linac4 BIS (PSB Injection Permit) (2)Slave BIC ‘PSB OK (2)’

Input for Master BIC ‘Choppers’

Channels 1 and 2 could be combined; BLMs always active For the extraction elements simply provision of error

status

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For Completeness: PSB BISMaster BIC ‘PSB Ejection’

Action: disable PSB extraction kickers Remark: rise-time of magnets too slow to take

different action

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Linac4 SISReaction time of SIS usually >1 cycle

SIS can evaluate different conditions, e.g. destination

Action depending on Master BIC affiliationList not exhaustive!WIC (Warm magnet Interlock Controllers; PLC-

based) information to be transmitted to SIS

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PSB Injection SISOutput 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

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Linac4 ECLinac4 EC not to be confused with PSB EC

for proton optimisation; here the aim is to reduce the Linac4 pulse lengthProposed 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 INAdd equipment that cannot stand full pulse

(wire scanners etc.?)

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PSB ECAction 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 pre-chopper/chopper/PSB RF inhibit

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Synchronisation Needs of BIS for Linac4For 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 pulsingIf beam permit changes to FALSE after this

timing: issue timing NX.START-PCHOPFor chopper action:

Act corresponding to beam permit, but only during the 400 μs window of the beam passage

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Synchronisation Needs of BIS for PSBFor 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)

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ConclusionsHybrid 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!

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b. mikulec , b. puccio , j-l. sanchez

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