Eva Barbara HolzerBLM Audit Sequel, CERN July 15, 2009 1

Agenda

9:00-10:00 Beam Interlock System Changes Following the 2006 Audit

Benjamin Todd

10:00-11:00 Beam Dump System follow-up from the 2008 Audit

Jan Uythoven

11:00-11:30 BLM 2008 audit follow-up Bernd Dehning

11:30-11:50 BLM: comparison threshold settings with loss measurements and management of threshold storage

Mariusz Sapinski

11:50-12:10 BLM ionization chamber space charge and procedures for changes of system settings during LHC running period

E. Barbara Holzer

Eva Barbara HolzerBLM Audit Sequel, CERN June 15, 2009 2

Eva Barbara Holzer, CERN

BLM Audit Sequel

CERN, June 15, 2009

BLM ionization chamber space charge and procedures for changes of system settings during LHC running period

Eva Barbara HolzerBLM Audit Sequel, CERN June 15, 2009 3

Content

1. Procedures for changes of system settings during LHC running period

2. Beam tests for threshold verification

3. Space charge induced saturation effects in the LHC BLM Ionization chambers (limits of operational range)

4. Archiving of documentation

Eva Barbara HolzerBLM Audit Sequel, CERN July 15, 2009 4

MPS Commissioning Procedure: The commissioning of the LHC machine protection system - MPS aspects of the Beam Loss Monitor system commissioning; EDMS: LHC-OP-MPS-0009. Close to being released (approval of magnet group).

Item: 5 (verification of thresholds during commissioning – beam tests), 6 (test procedures, provoked losses)

Procedures for changes of BLM system settings during LHC running period. Preliminary version available.

Item: 5 (changing thresholds during the run), 7 (changes to Master Table and propagation of changes)

Space charge induced saturation effects in the LHC BLM Ionization chambers. Treated in PhD thesis of M. Stockner and D. Kramer

Item: 2 (saturation effects, limits of current monitor design) Covered by Mariuzs’ talk:

Item: 5 (threshold verification by 2008 beam loss measurements & improved simulations), 7 (definition of initial values of the Master Table)

Documents – Audit Items (2, 5, 6 and 7)

Eva Barbara HolzerBLM Audit Sequel, CERN July 15, 2009 5

Procedures for changes of BLM system settings during LHC running period. Preliminary version available.

Item: 5 (changing thresholds during the run), 7 (changes to Master Table and propagation of changes)

Procedures (plus additional software needed) defined Additional software Approval process by all involved parties Test of the procedures during “dry run”

Procedures

Eva Barbara HolzerBLM Audit Sequel, CERN July 15, 2009 6

BLM representative: The role of the BLM representative will be filled 24/7 by one person, according to a

pre-defined rota, reachable by one “BLM telephone line” (forwarded to the mobile of the BLM representative).

Execution of procedures: The procedures will be executed by the BLM representative on request of the MPP

representative (role to be defined); or on request of the BLM representative after agreement of MPP representative or the machine supervisor (to be defined)

The procedures can only be executed from the CCC by the BLM representative together with the machine supervisor (two persons for cross checking).

Agreement of BLM representative: A written and documented agreement of the BLM representative is needed for:

1. Any change in the structure of a database (MTF, Layout, LSA, M&L DB)

2. Any change in RBAG (concerning BLM) The changes shall be requested by an EMDS document using EDMS approval

procedure.

Procedures

Eva Barbara HolzerBLM Audit Sequel, CERN July 15, 2009 7

Introduce a new monitor in the BLM system

MTF Layout LSA FEC

concentrator

measurement& logging DB

DCUMslot

expert

name

(Pascal)

MTF specific data

(Sonia)Update

(Sonia)

Settingsof BLM + electronics equipment (Slava)

Update

Slot-equipment link

+error detection (Julien or automatic at night)

Generation of parameter space and settings

(Mariusz or BLM rep.)

Update

(Mariusz)

Propagation of changes and online check

Restart (OP)

Restart

(OP)

Introducingmissing slots

(Julien)

Thresholds + Settings (Mariusz and Jonathan)

request ofsettings

request ofsettings

fixed

displays

Creationvariables(Chris R.) Manual input of data

Manually triggered procedure

Automatic procedure

E-mail on errors

E-mail

comparison of variables

Eva Barbara HolzerBLM Audit Sequel, CERN July 15, 2009 8

scenario 1 2 3 4 5 1 2 3 4 5 6 1 duration

new monitor X X X X X X X X X X X X 1 day

disable monitorX X X X 1 hour

Remove from DB X X X X X X X 1 day

change connection X X X X X X 1 day (possible to make

faster?

change master X X 1 hour

change family X X 1 day

1. DCUM slot expert name (Pascal)2. MTF specific data (Sonia)

3. Settings of BLM & electronics or disable flag (Slava)

4. Introducing missing slots or changing structure (Julien)

5. Thresholds and/or Settings (Mariusz and/or Jonathan)

1. Generation of parameter space and/or settings, propagation to HW and online check using Trim application (Mariusz or BLM rep.)

2. Update MTF (Sonia)3. Update LSA (Mariusz)

4. Creation of logging variables (Chris)

5. Restart Concentrator (OP)

6. Restart fixed display (OP)

1. MTF->Layout automatic nightly synchronization

Summary of actions needed to be taken in use cases

Eva Barbara HolzerBLM Audit Sequel, CERN July 15, 2009 9

MPS Commissioning Procedure: The commissioning of the LHC machine protection system - MPS aspects of the Beam Loss Monitor system commissioning; EDMS: LHC-OP-MPS-0009. Close to being released (approval of magnet group).

Item: 5 (verification of thresholds during commissioning – beam tests), 6 (test procedures, provoked losses)

Commissioning Procedures defined Approved by all involved parties (under approval by magnet group)

Beam Tests

Eva Barbara HolzerBLM Audit Sequel, CERN July 15, 2009 10

Verifies the correct functioning of the entire BLM BIS-LBDS systems chain by provoking very small losses

Test 1: MPS functionality of the BLM with beam Decrease thresholds, create local bump Measure delay between the time where the loss signal exceeds the threshold and

the time of the beam dump Time estimate: 2h

Test 2: Interface of direct BLMs with the beam dumping system Reduce the voltage setting of the abort threshold. Dump the injected beam on the collimator TCDQ and TCSG From the amount of lost beam and the threshold setting, deduce the nominal

threshold setting. Time estimate: 2h

Beam Tests: Basic BLM system functionality

Eva Barbara HolzerBLM Audit Sequel, CERN July 15, 2009 11

Verify that thresholds are adequate to protect the superconducting magnets against quenches. Must be performed for fast and slow losses; Ideally repeated for different types of magnets

Performed for one beam only. Test 3: Provoked quench for transient losses

The beam is steered into the selected magnet. The losses are recorded and compared to the expected quench level. The intensity is increased step by step until the magnet quenches. Time estimate: 1h per magnet

Test 4: Provoked quench for steady state losses with circulating beam. The beam is slowly ‘bumped’ towards the selected magnet. The losses are recorded and compared to the expected quench level. The beam is brought closer to the magnet step by step until the magnet quenches. Time estimate: 1h per magnet

Beam Tests: BLM thresholds and quench level

Eva Barbara HolzerBLM Audit Sequel, CERN July 15, 2009 12

Collimators are defining the aperture of the machine - Losses should occur first at the collimators or downstream of the collimation sections.

The BLMs at the collimators or downstream of the collimation sections in IR7 and IR3 are the first devices to detect the losses (for fast losses).

Typical fast failure scenarios must be provoked with low intensity beams to verify that BLM thresholds and reaction times are adequate.

Beam Tests: BLM thresholds and reaction times in collimation sections

Eva Barbara HolzerBLM Audit Sequel, CERN July 15, 2009 13

Space charge induced saturation effects in the LHC BLM Ionization chambers. In preparation.

Based on PhD thesis of M. Stockner and D. Kramer

Space charge

Eva Barbara HolzerBLM Audit Sequel, CERN July 15, 2009 14

Slow ions form a quasi field free region next to the cathode, which reduces the active detector volume. From: R.M. Zwaska, PhD thesis, 2005:

Critical ionization rate for space charge:

LHC IC current at onset of space charge: 26 mA

Electronics max input: 1 mA (23 Gy/s for IC)

Space charge correction:

Saturation effect due to space charge build-up

μ … ion mobility

φ … ionization rate

U … applied chamber voltage

d … distance between the electrodes

q … elementary charge

V … active detector volume

tc … irradiation time

Eva Barbara HolzerBLM Audit Sequel, CERN July 15, 2009 15

Max LHC signal range (limit of LHC IC readout electronics: 23 Gy/s) ~ factor 100 below the SPS dump dose

~8% between SEM signal and space charge corrected IC signal

IC to SEM comparison SPS internal beam dump

Eva Barbara HolzerBLM Audit Sequel, CERN July 15, 2009 16

Measured IC signal vs beam current, estimated error due to correction: ~11%

before correction space charge corrected

HERA internal beam dump measurementsb

eam

en

erg

y:

920

Ge

V

39

GeV

Eva Barbara HolzerBLM Audit Sequel, CERN July 15, 2009 17

BI group wants to adopt a common archiving system A proposal has been made and needs to be approved by the group:

EDMS plus SharePoint webpage for static documents and SVN for scripts, software codes etc.

BL plans to move existing documentation to EDMS

Archiving of Documentation – Item 46