Apollonio [email protected]

A. [email protected]

ESS: Machine Protection considerations and BIS

architecture

Acknowledgments: D. Curry, A. Nordt, R. Schmidt

CERN

Andrea Apollonio page 2

Outline

• Introduction to ESS

• Linac4 Comparison

• ESS MPS and BIS Architecture

• Conclusions

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Outline




• Conclusions

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Overview

● The European Spallation Source (ESS) will house the most powerful proton linac ever built. The average beam power will be 5 MW

which is five times greater than SNS. The peak beam power will be 125 MW

which is over seven times greater than SNS

● ESS is located in southern Sweden adjacent to MAX-IV (A 4th generation light source)

● To provide a world-class material research center for Europe Lund (Sweden)

[1]

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What is ESS?● ESS is a neutron spallation source for neutron scattering

measurements.● Neutron scattering offers a complementary view of matter

in comparison to other probes such as x-rays from synchrotron light sources.

The scattering cross section of many elements can be much larger for neutrons than for photons.

[1]

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Neutron Scattering● Neutron scattering can reveal the molecular and magnetic

structure and behavior of materials, such as: Structural biology and biotechnology, magnetism and superconductivity,

chemical and engineering materials, nanotechnology, complex fluids, and others

X-Ray Image

Neutron radiograph

Neutron radiograph of a flower corsage

Neutron scattering of hydrogen in a

metal organic framework

[1]

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What is Different About ESS?

● The average proton beam power will be 5 MW Average neutron flux is

proportional to average beam power

5 MW is five times greater than SNS beam power

● The total proton energy per pulse will be 360 kJ Beam brightness (neutrons

per pulse) is proportional to total proton energy per pulse

360 kJ is over 20 times greater than SNS total proton energy per pulse

[1]

= 62.5 mA * 2 GeV * 14 Hz * 2.86 ms

Average Linac

Current

Output Energy

Repetition Rate

Pulse Length

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Outline




• Conclusions

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Linac4: Layout

CCDTL PIMSMEBTRFQH-Source DTLLEBT45keV 3MeV 50MeV 100MeV 160MeV

Transfer Line

RFQ DTL PiMS

Low Energy Beam Transfer

Radio-FrequencyQuadrupole

Medium Energy Beam Transfer

DriftTubeLinac

CoupledCellDriftTubeLinac

PiModeStructure

acceleration acceleration

Courtesy L. Hein

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Linac4 MPS: requirementsFocus of Linac4 MPS:• Availability: target >95%• Activation: above 10 MeV in case of beam losses [2]• Damage: very low risk of significant damage in case of ‘single

pulse losses’• Optimization of proton delivery to the different destinations

MPS requirements:• Highly dependable (almost same HW as LHC BIS)• Reaction time within the same pulse (<400us)• Allow for flexible operation (SIS + External Conditions)

MPS requirements during commissioning depend on:• Energy reached• Bunch intensity• Users availability

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LINAC4 BIS: Architecture

[3]

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BIS ACTIONS

‘SOURCE RF’ MASTER BIC:• Action on the Source

RF in order to inhibit the RF voltage

• For redundancy, action on the Pre-chopper in order to deflect the beam at 45 keV

‘CHOPPERS’ MASTER BIC:• Action on the Pre-

chopper at 45 keV• For redundancy,

action on the chopper at 3 MeV

• In addition, the PSB RF is disabled in case some beam still reaches the PSB

‘PSB EJECTION’ MASTER BIC• disable the

extraction kickers• magnet current

acquisitions at extraction time surveyed in addition via the SIS

To preserve the Linac4 Source stability, it is always better to act on the choppers to stop the beam, when possible

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Outline




• Conclusions

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ESS: Layout and Parameters

Power of 5000 kW

Drift tube linac with

4 tanks

Low energy beam

transport

Medium energy beam

transport

Super-conducting cavities High energy beam transport

RFQ352.2 MHz

75 keV 3 MeV 78 MeV 200 MeV 628 MeV 2000 MeV

Source LEBT RFQ MEBT DTL Spokes High β

Medium β

HEBT & Upgrade

2.4 m 4.0 m 3.6 m 32.4 m 58.5 m 113.9 m xxx.0 m

352.21 MHz 704.42 MHz

DumpDogleg

Target

ESS Linac4

Proton beam energy

2.0 GeV 160 MeV

Pulse length 2.86 ms 400 usPulse repetition

rate14 Hz 1.1 Hz

Average beam power

5 MW 5.1 kW

Average beam current

62.5 mA 40 mA

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ESS: Target

Courtesy A. Nordt

Tungsten target with rotating wheel 33 sectors with cooling channels (Helium)Synchronized to 14 Hz

2mm gap

Wheel

He flow around slices

Angular sectors

Proton Beam Window

Target Monolithr=6m, h=10m

Beam Ports

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2 Weeks at ESS: MPS Activities• A risk analysis on a system basis had already been carried out• Several meetings per day with different system experts to

investigate possible failures and failure effects• Use of Jira + personal notes to keep trace of work progress• ‘Spread’ the idea of a Beam Interlock System• Define competences of MPS and responsibilities of User systems

Outcomes:• Failure modes and effects system by system• System dependencies• Identification of signals required for MPS (type and number)• Definition of Beam modes and Machine modes• Ideas for the commissioning phase• Definition of a suitable BIS architecture• Document on outcomes of the work

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Example: Warm Linac

Source Solenoids Steerers Quadrupoles BCTs BLMs BPMs Faraday Cups

Wire Scanners Absorbers Collimators Iris Choppers Vacuum Valves RF cavities

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Linac Interlocks and ActuatorsNo “LHC-type” beam dump (kickers + dump line)• The beam has to be stopped in the Linac at the lowest possible

energy by the actuators• Actuators are typically: Source and Choppers• No way to cut the portion of beam downstream the MEBT• Reaction time of the BIS has to be within the same pulse when a

failure occurs

Some peculiar Linac Interlocks:• BCMs current difference

Measures the transmission between two points Alternative to BLMs (only option at low energy)

• IRIS 8 blades, variable aperture to change beam current Complex device, cooling monitored

• BI moving devices (e.g. Faraday Cups): Position has to be interlocked

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ESS MPS: requirementsFocus of ESS MPS:• Availability: target 95%• Activation: above 10 MeV in case of beam losses• Damage: risk of significant damage in case of ‘single pulse losses’ even at low energy• Synchronization with the Target• ‘Errant Beams’ [4]

MPS requirements:• Highly dependable • Reaction time within: 10 us• Allow for operation up to different sections of the Linac

Actuators response times:• Source: 100 us• LEBT chopper: 100 ns• MEBT chopper: 10 ns

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ESS BIS: Architecture

ESS Source can be switched OFF without losing stability (always activated)

Cou

rtesy

A. N

ordt

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ESS BIS: Architecture

One more actuator could be represented by the RF of the RFQ (SNS)

Cou

rtesy

A. N

ordt

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ESS BIS: MASTER LEVEL 1

The Iris will be a critical component (design and interlock) Damage potential already in the LEBT (0.5 kW beam power) 1st beam destination: LEBT FC Input from Master Level 2 Input monitoring the effect of the chopper (ChON + current in BCM2 =

failure)

Ch 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 OUT

Interlock Element

SIS

Source Status

Iris status (cooling)

Solenoid 1 + Steerer 1 status

Solenoid 2 + Steerer 2 status

LEBT

Chopper statu

s

LEBT

Faraday Cup IN

LEBT

Faraday Cup OUT

EMU position?

Control Room Button

Radiation Monitors (PSS)

From Destination Master

LEBT Vacuum

TSS

Button

BCM2 +

Chopper

status

Master 1: Beam_Permi

t

1 1 1 1 1 1 0 1 1 1 1 1 1 1 1 x 1

1 1 1 1 x 1 1 0 x 1 1 x 1 x x x 1

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ESS BIS: MASTER LEVEL 2

Monitors Beam destinations (FCs + Dump + Target) Current in the dogleg monitored and correlated with the beam destination Definition of destinations for the commissioning and test phases

Ch 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 OUT

Interlock

Element

MEBT OK

Farada

y Cup MEBT IN

Farada

y Cup MEBT OUT

DTL OK

Farada

y Cup DTL IN

Farada

y Cup DTL OUT

Spokes +

Mbeta1 OK

Farada

y Cup Mbeta 1 IN

Farada

y Cup MBeta 1

OUT

Mbeta 2

+ HBeta

OK

Current TARGET OK

Target Line

OK

Current DUMP OK

Dump Line

OK

Master 2: Bea

m_Permit

1 1 0 x x x x x x x x x x x x 1 Beam to MEBT FC 1 0 1 1 1 0 x x x x x x x x x 1 Beam to DTL FC 1 0 1 1 0 1 1 1 0 x x x x x x 1 Beam to MBeta FC 1 0 1 1 0 1 1 0 1 1 0 x 1 1 x 1 Beam to Dump

1 0 1 1 0 1 1 0 1 1 1 1 0 x x 1 Beam to Target

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ESS BIS: SLAVE MEBT

RFQ absorber and Chopper Dump: damage risk already at low energy BCMs current differences (transmission): main tool to detect losses at low

energy (below BLMs sensitivity) RF interlocks: 1 per RF cell Chopper: both User and Actuator

Ch 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 OUT

Interlock Element

SIS

RFQ absorber (cooling + secondary e

mission)

RFQ RF

RFQ trans

mission (BCM3-BCM2)

MEBT Chopper status

MEBT Collimators

status (cooling,

charge, position)

MEBT Chopper Dump

MEBT

Vacuum

BCM2 + Chopper status (from ti

ming)

BCM4 - BCM3

Slave 1: Beam_Permi

t

1 1 1 1 1 1 1 1 1 1 x x x x x x 1

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ESS BIS: SLAVE SPOKES + MBETA1

BLMs start to be in their sensitivity rangeCryo OK signal for start up (as LHC)Possiblility of fast losses due to power supplies failures of the

steerers

Ch 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 OUT

Interlock Element

SIS

RF OK (x #RF cells)

Spokes * MBeta

Vacuum

Steerers

BCMs

difference (tbd, BCM10 – BCM9?)

Cryo

OK (x

#Cryomodules)

BLMs

Slave 3: Beam_Permi

t

1 1 1 1 1 1 1 x x x x x x x x x 1

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Availability Model: IsographFailure rates and recovery times from the failure catalogue: ~99% availability

Work in progress: ESS Availability Model in Isograph

Benchmark for Linac4 Availability Model

Paper to IPAC’14 in collaboration with ESS

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Outline




• Conclusions

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Conclusions

• A possible architecture for the ESS BIS was designed

• A document will soon be released summarizing these studies

• ESS availability model is under work (benchmark for Linac4 availability model)

Personal remarks:

• Previous experience with Linac4 was a fundamental starting point

• this very intensive way of working was very fruitful and allowed reaching an ambitious goal in a very short time

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THANKS A LOT FOR YOUR ATTENTION!

References:[1] slides 4-7: “The European Spallation Source”, D. McGinnis, PLC Workshop 2013.[2] “Predictions of induced radioactivity and residual dose rates in Linac4” F. P. Della Torre, M. Silari, EDMS 1304119 (2013)[3] “Beam Interlock specifications for Linac4, transfer lines and PS Booster with Linac4”, B. Mikulec et al. EDMS 1016233 (2013). [4] “Errant Beam Update”, Accelerator Advisory Committee, C. Peters, Accelerator Operations Machine Specialist, 7 May 2013

CERN


Why is errant beam important● Errant beam mechanism

Beam hitting cavity surface desorbs gas or particulates creating an environment for arcing

● Super Conducting Linac (SCL) cavity performance degrades over timeSCL cavities do not trip with every errant beam pulse, but the probability

for a trip increases with timeCavity fields have been lowered and cavities have been turned off which

results in lower beam energy● SCL cavity performance degradation from errant beam can be

restored (except for cavity 06c)Requires cavity warm up during a long shutdown and then RF

conditioning before beginning beam operationCryomodules have been removed from the tunnel for cavity RF coupler

repairs but this takes months[3]

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SLAVE 2: DTLCh 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 OU

T

Interlock Element

SIS (BPM, BSM?)

RF OK (x #RF cells)

DTL Vacuum (fast valves?)

Steerers

BCM9 – BCM4

Standalone

BCM?

Slave 2:

Beam_Permit

1 1 1 1 1 1 x x x x x x x x x x 1

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SLAVE 3: Spokes + MBetaCh 0 1 2 3 4 5 6 7 8 9 10 11 1

213

14

15

OUT

Interlock Element

SIS

RF OK (x #RF cells)

Spokes * MBeta

Vacuum

Steerers

BCMs

difference (tbd, BCM10 – BCM9?)

Cryo

OK (x

#Cryomodules)

BLMs

Slave 3:

Beam_Permit

1 1 1 1 1 1 1 x x x x x x x x x 1

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SLAVE 4: Mbeta + HBetaCh 0 1 2 3 4 5 6 7 8 9 10 11 1

213

14

15

OUT

Interlock Element

SIS

RF OK (x #RF cells)

Mbeta * HBeta

Vacuum

Steerers

BCM11 – BCM10

Cryo

OK (x

#Cryomodules)

BLMs

Slave 4:

Beam_Permit

1 1 1 1 1 1 1 x x x x x x x x x 1

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SLAVE 5: Dump LineCh 0 1 2 3 4 5 6 7 8 9 10 11 1

213

14

15

OUT

Interlock Element

SIS

Dump status OK

BCMs

difference (before

and

after the

dogleg)

Magnets (Quads,

…)

Dump Line Vacuum (Fast

valves?)

BLMs

Slave 5:

Beam_Permit

1 1 1 1 1 1 x x x x x x x x x x 1

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SLAVE 6: Target LineCh 0 1 2 3 4 5 6 7 8 9 10 11 1

213

14

15

OUT

Interlock Element

SIS

Target status (slow)

Target (Rotating motor)

Magnets (Quads,

…)

BCMs

difference (before

and

after the

dogleg)

Target Line

Vacuum

(Fast valves?)

BLMs

Raster Magnet

Raster Beam instrumentation

Neutron Instrumentation

Collimator proton beam window

Slave 6:

Beam_Permit

1 1 1 1 1 1 1 1 1 1 1 x x x x x 1

• Collimators in front to proton beam window interlocked?• Rastering can be off for low intensity

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Example of Input Signal to the MISMagnet current surveillance:

Operational Mode

I(t)

0 A

100 ABeam to the target

Beam to the dump

Beam to the dump

Current Bend_DUMP = 0Current Bend_TARGET = 1



Apollonio [email protected]

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