commissioning of blm system

MPWG 9 March 2007 1

Commissioning of BLM system

L. Ponce

With the contribution of C. Zamantzas, B. Dehning, E.B.

Holzer, M. Sapiensky

MPWG 9 March 2007

Outlines

Overview of the system

signal available in the CCC

Strategies for the thresholds settings

hardware commissioning

commissioning with beam

conclusions

MPWG 9 March 2007

Quench protection system

(damage protection)

BLM system damage

protection, no redundancy

BLM for machine protection

Arc Dipole Magnet

The only system to protect LHC from fast losses (between 0.4 and 10 ms)

The only system to prevent quench

MPWG 9 March 2007 4

Detector

about 3800 ionisation chambers + 320 Secondary emission detectors measure the secondary shower outside the cryostats created by the losses

MPWG 9 March 2007 5

BLMS Signal Chain

Channel 1

Mul

ti-

plex

ing

and

doub

ling

Optical TX

Channel 8

Detector

Digitalization

Optical TX

VM

E B

ackp

lane

Optical RX

Optical RX

Sup

erco

nduc

tin

g m

agne

tSecondary particle shower generated by a lost

Demulti-plexing

Demulti-plexing

Sig

nal

sele

c-ti

on

Thr

es-h

olds

co

mp-

aris

on

Cha

nnel

sel

ecti

on a

nd

beam

per

mit

s ge

ner-

atio

n.

Status monitor

FE

E 2 Beam Energy

TU

NN

EL

SU

RF

AC

E

FE

E 1

Unmaskable beam permitsMaskable beam permits

Back End Electronics (BEE)

Front End Electronics (FEE)

MPWG 9 March 2007

Thresholds and interlocks

12 running sums for 32 energy levels for each channel, 16 channels per card, 345 surface cards. → table of 2 millions values!

Any of this signal over the thresholds generate a beam dump request via the BIC

28

Tunnel Card BLMCFC

1 23 . . .

28

Ionisation Chamber

Patch Box

Surface Card BLMTC (DAB64x)

GOH

GOH

Surface FPGA

MEMORY 16 bits

16 bits

16 bits

Anti-Fuse FPGA

Control

Control

16 bits

Control

Mezzanine

SRAM (1)Acquisition Data

SRAM (2)Acquisition Data

SRAM (3)Post-Mortem

data

data

data

Power PC

Control

Data

VMEInterface

Control

Data

Control

Control

Control

Control

1 23 . . . 8

2|||||||||||||

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CFC Analogue

. . .

Control

TLKOptical receiver

16 bits

Control

TLKOptical receiver

16 bits

Control

TLKOptical receiver

16 bits

Control

TLKOptical receiver

16 bits

Control

GOL

GOL

Tunnel Card BLMCFC

GOH

GOH

16 bits

16 bits

Anti-Fuse FPGA

Control

Control

1 23 . . . 8

2|||||||||||||

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CFC Analogue

. . .

Control

GOL

GOLIonisation Chamber

Combiner CardBLMCOM

DUMP (x3)

BEAM ENERGY

BEAM PERMIT

Beam Interlock Controller

BIC DUMP (x2)

BEAM PERMIT

Beam Energy Tracker

BETBEAM ENERGY

optical fibres

VM

E6 4

x B

us

Bac

kpla

ne

DUMP (x3)

BEAM ENERGY

BEAM PERMIT

Control

Data

Tunnel max 2km Surface

max 300m

Ionisation Chamber

... ...

Ionisation Chamber

Post-Mortem

DataLogging

Data

MPWG 9 March 2007 7

Loss pattern given by R. Assmann team (C. Bracco, S. Redaelli, G. Robert-Demolaize)

GEANT 3 simulation of the secondaries shower created by a lost proton impacting the beam pipe

simulation of the detector response to the spectra registered in the left and right detector (M. Stockner with G4)

500 protons same z position and same energy

impacting angle is 0.25 mrad

longitudinal scan performed to optimize the BLM location

1. Principle of the simulation

MPWG 9 March 2007

Definition of the thresholds

Loss pattern given by R. Assmann team (C. Bracco, S. Redaelli, G. Robert-Demolaize)

GEANT 3 simulation of the secondaries shower created by a lost proton impacting the beam pipe

simulation of the detector response to the spectra registered in the left and right detector (M. Stockner with G4)

500 protons same z position and same energy

impacting angle is 0.25 mrad

longitudinal scan performed to optimize the BLM location

MPWG 9 March 2007 9

Geometry description

3 transverse positions of impact outermost, innermost and top

MPWG 9 March 2007 10

Typical result

Maximum of the shower ~ 1m after impacting point in material

increase of the signal in magnet free locations

factor 2 between MQ and MB

z (cm)


Particle Shower in the Cryostat

catch the losses:

MB-MQ transition

Middle of MQ

MQ-MB transition

minimize uncertainty of ratio of deposited energy in the coil and in the detector

B1-B2 descrimination

Position of the detectors optimized to:


2. Position in the ARCS Example of topology of Loss (MQ27.R7) Peak before MQ at the shrinking vacuum pipe location (aperture limit

effect) End of loss at the centre of the MQ (beam size effect)

More simulation are needed to get better evidence (higher populated tertiary halo)


Particle shower in the detector

Addition of all the weighted signals from the previous locations

Positions chosen for the arcs also optimum for the DS.

MPWG 9 March 2007

Mainly BLMQI at the Quads (3 monitors per beam) + cold dipoles in LSS

Beam dump threshold set to 30 % of the quench level (to be discussed with the uncertainty on quench level knowledge)

Thresholds derived from loss maps (coll. team), secondaries shower simulations (BLM team), quench level simulations and measurements (D. Bocian)

BLMs for the arcs

beam 1

beam 2


BLMs for warm elements

beam 1

beam 2top view

BLM in LSS :at collimators, warm magnets, MSI, MSD, MKD,MKB, all the masks…

Beam dump threshold set to 10 % of equipment damage level (need equipments experts to set the correct values


Mobile BLM

use the spare chambers

use the spare channels per card : 2 in the arcs at each quad, a bit more complicated in the LSS.

electronics is commissioned as for connected channel

a separate Fixed display for non-active channels is planned : to be discussed

detection thresholds: ???

MPWG 9 March 2007

Generation of threshold table

Quench and damage level threshold tables will be created for each family of BLM locations.

They will be assembled together into MASTER table.

For every location a threshold for 7 TeV will be calculated.

Table will be filled using parametrized dependence on Energy and Integration time.

MASTER table, MAPPING table (BLM location vs electronic channel) will be stored in safe database.


Calibration and Verification of Models

Shower code(prediction error large

for tails)

Magnet quench(2 dim, energy, duration, large

variety of magnet types)

Threshold table

Detector(particle - energy spectrum

dependence)

Detector model (Geant) =

(CERN /H6)

Magnet model (Geant)=

HERA beam dump(tails of shower measurements)

Magnet model (SQPL)(heat flow, temp. margin, …)

= fast loss: sector test

slow loss: SM18

Calibration needed for: verification:


Reasons to change the thresholds? How often?

1) to check Machine Protection functionalities of BLMs (interlocks): decrease the thresholds in order to provoke a dump with low intensity

frequency: during the commissioning, after each shut-down (?),

for a set of detectors

2) study/check of quench levels (“quench and learn” strategy?):

implies dedicated MD time, post-mortem data analysis, could be related

to check the correct setting of the thresholds

Frequency : ? Probably during shut-down

For HERA, only one change since the start-up


1) commissioning of individual systems (MSI, LBDS, collimators) : to get a loss picture of a region, to give “warning” levels

adjust thresholds after studies of the systems to optimize the operational efficiency vs. the irradiation level

frequency : 1 or 2 iterations after determination of the thresholds and localized in space (injection region, IR7…)

2) To match quench level during commissioning (operational

efficiency):

Probably few iterations

some flexibility would help operation but is not an absolute need

MPWG 9 March 2007

Systematic Uncertainties at Quench Levels

about 1 % Radiation & analog elec.

Electronic calibration< 10 %Electronics

sim., measurements with beam (sector test, DESY PhD)

< 10 - 30 %

fluence per proton

Simulations

measurements with beam (sector test), Lab meas., sim. fellow)

Source, sim., measurements

Correction means

?Topology of losses (sim.)

< 200 %Quench levels (sim.)

< 10 – 20 %

Detector

relative accuracies

B. Dehning, LHC Radiation Day, 29/11/2005

MPWG 9 March 2007

3. Proposed implementation

Threshold GUI Reads the “master” table Applies a factor (<1) Saves new table to DB Sends new table to CPU

CPU flashes table if allowed (on-board switch)

Thresholds are loaded from the memory on the FPGA at boot.

Combiner initiated test allows CPU to read ‘current’ table.

SIS receives all tables

Compares tables Notifies BIS (if needed)

DETECTOR 16 – RS 12


...






...




Master Table

Applied Table

Database

VME CPU

FLASH Threshold

Table

BLM Threshold Comparator

FLASH MEMORY

FPGA

SWITCH

VME Bus

READ Threshold

Table

BLM Combiner & Survey

SoftwareInterlock System

Threshold Preparation

GUI

CO

MP

AR

E T

HR

ES

HO

LD

S

FPGA

READ

APPLY FACTOR

SEND TOSYSTEMS

BIS

BIS

*

*

* *

*

*

* Secure transmission using MCS

FirmwareThresholds

MaskingOther Note: possible upgrade by adding a

comparison with master table on the board BUT feasibility has to be checked


Consequences on the reliability of the system?

Flexibility given by changing remotely the thresholds has to be balanced with the loss of reliability of the system

The proposed implementation allows both possibilities

But the remote access will have to be validated by machine protection experts when more detailed implementation of MCS and comparator are available (by the beginning of summer?).

MPWG 9 March 2007

System ready for LHC and fulfill the Specifications?

Hardware expected to be ready for LHC start-up Threshold tables (calibration of BLM) based on

simulations. Analysis effort of BLM logging and post-mortem

data (LHC beam data, “parasitic” and dedicated tests) to be started in 2006!

Calibration of threshold tables Interpretation of BLM signal pattern

Extensive software tools for data analysis essential to fulfill the specifications! Start now to specify and implement

MPWG 9 March 2007

BLMS Testing Procedures PhD thesis G. Guaglio

Radioactive source test (before start-up)

Functional tests

Barcode check

HV modulation test (implemented)

Double optical line comparison (implemented)

10 pA test (implemented)

Thresholds and channel assignment SW checks (implemented)

Beam inhibit lines tests (under discussion)

DetectorTunnel

electronics

Surface

electronicsCombiner

Inspection frequency:

Reception Installation and yearly maintenance Before (each) fill Parallel with beam

Current source test (last installation step)

Threshold table beam inhibit test (under discussion)


Commissioning Procedures - Steps

Environmental test: temperature dose & single event

Steps:

Elec. tunnel, 20 year of operation & “no” single event effects Elec. tunnel, 15 – 50 degree

Functional test: before installation during installation during operation

All equipment, LAB, current and radioactive source

Connectivity, current and radioactive source

Connectivity, thresholds tables

Calibration: before startup after startup Establishing model (detector, shower, quench behavior)

a: no beam abort , no quench, no actionb: use loss measurements and models for improvements

Calibration

Functional testEnvironmental test

Beam energy

detector LBDSBICsurface elec.tunnel elec.magnet

Particle shower

MPWG 9 March 2007

Hardware commissioning

complete detailed procedure documented in MTF

functionalities linked with Machine protection will be reviewed in the Machine Protection System Commissioning working Group

validation of the connectivity topology: registration in database of the link position in the tunnel-channel identification-thresholds

MPWG 9 March 2007

Commissioning with beam see presentation of A. Koshick in CHAMONIX

Motivation of the test: Establish thresholds = establish the correlation

between quench level and BLM signal = Calibration! Verify or establish „real-life“ quench levels Verify simulated BLM signal (and loss patterns) In particular: What BLM signal refers to the quench level of

a certain magnet type?

=> Accurately known quench levels will increase operational efficiency!


How to do the quench test: Implementation

Initial conditions & requirements: Pilot beam 5x109

Clean conditions, orbit corrected (to better +/- 3 mm?). BPM data/logging available Trajectory BLM data/logging available Additional “mobile” BLMs at the chosen locations

Set optics (3-bump)

Vary intensity5x109 – max. 1x1011

+logging all relevant data (BPM, BLM,BCT,emittance …)

Magnet quench

if circulating beam, possibility to check steady state losses quench limit. If sector test, fast losses quench limit

Simple idea: Steer beam into aperture and cause magnet quench


How to do the test: What we want to learnBeam Parameters Emittance Intensity Momentum spread

Optics Parameters -function Dispersion Trajectory/Orbit

Impact Length Impact Position

Proton density that caused quench in SC magnet

BLM signal

Determination of quench level Calibration


Conclusions

Controlled, defined test to establish Absolute quench limits BLM threshold values Model and understanding of correlation of loss pattern,

quench level, BLM signal

This test is essential for an early calibration of the BLM system, even if beam time consuming

It has to be done before increasing intensity

commissioning of blm system

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