1. Test and start‐up procedures
Eva Barbara Holzer, CERN
LHC BLM Audit
CERN, June 10, 2008

2. Dependability design of BLM system
Calibration
Functional test
Environmental test
Beam energy
detector
LBDS
BIC
surface elec.
tunnel elec.
magnet
Particle shower
PhD thesis (G. Guaglio, Reliability of the Beam Loss Monitors System for the Large Hadron Collider at CERN, PhDThesis, Universit´e Clermont Ferrand II - Blaise Pascal, 2005.)
Fail safe design: “The most probable failure of the component does not generate the worst consequence (= risk to damage a magnet).”
Choice of reliable and radiation tolerant components
environmental tests of tunnel electronics:
Temperature – 50 degree
Dose & single event no single event effects observed during tests, dose corresponding to 20 years of operation
Redundancy and voting (when single components are not reliable enough)
Constant monitoring of availability and drift of readout channels (Functional Tests)

3. Functional Tests PhD thesis G. Guaglio
Detector
Tunnel electronics
Surface electronics
Combiner
Functional tests before installation
Barcode check (visual, serial numbers)
Current source test
Radioactive source test
HV modulation test
Beam inhibit lines tests
Threshold table data base comparison
10 pA test
Double optical line comparison
System component identity check
Inspection frequency:
Reception Installation and yearly maintenance Before (each) fill Parallel with beam
Functional checks – Monitoring of drifts

4. Leakage Current {M, 5m, T, HWC} (10-BLM P6: LC(offset) w/cable&M-r)
Cable identification check (sticker, visual)
Cable continuity check; particularly verify if there are no conductors swapped
Test of insulation, connection and current limits (bad connection introduces offset current
The crate shall be equipped with a test card to record the measurements.
Offset current with HV on shall be below 0.5 pA on all channels.
MTF recording
manually
test card in tunnel rack
monitor
tunnel rack slot

5. Current Source {M, 5m, T, HWC} (10-BLM P7: Signal via source w/cable)
Tests of insulation, correct interconnections and current limits
Signal cable disconnected from monitor, current source connected. Correct channel connection checked by observing channel by channel the current signal at the test card
In case the measured currents are outside the limits the corresponding cable are changed
MTF recording
manually
test card in tunnel rack
cable of monitor
tunnel rack slot

6. ThresholdComparator & Combine&Servey (Combiner) vs DB Comparison {F, 5m, -, HWC QUICK} (60-BLM P1: Threshold/Ch Matrix Test)
Before each fill
Threshold table, channel parameters (e.g. electronics card number) and channel mapping (matrix for maskable/unmaskable and connected/unconnected) are compared to the one stored in the data base
Sequencer, man. (after th. ch.)
combiner
RBAC
TC & combiner
ELSA DB

7. TC to CS (Combiner)Transmission {F, 5m, -, HWC QUICK} (60-BLM P3: UBP Check BLETC to BLECS)
Beam permit transmission from all threshold comparators to the last combiner card
Before each fill
For maskable and un-maskable channels
Sequencer (timeout), Expert
combiner TC
last combiner

8. CS to CIBU Transmission (responsibility of BIS) {F, 5m, -, HWC QUICK} (60-BLM P4: UBP Check BLECS to CIBU)
Technically possible, but not yet foreseen
Before each fill
For maskable and un-maskable channels
Beam permit transmission from last combiner card to the “controls interlock beam user” (the interface to the BIC in the VME crate).
Last combiner BLM interface to BIC
Toggle of redundant lines
BIS
last combiner
BLM interface to BIC

9. Remove Beam Permit {F, 5m, -, HWC} (60-BLM P2: TTable User Beam Permit T)
Lab test, details not finalized (see talk by Ch. Zamantzas)
Tested all 16 channels, all 12 running sums and all 32 energy values of one threshold comparator, each time a new firm ware is installed – test of firmware.
On each channels, each running sum and at each energy in the threshold comparator is brought above the abort threshold (increasing the signal and/or lowering the threshold value).
Check if firmware correctly identifies the channel above threshold.
manually TC

10. Beam Energy Reception {F, 5m, -, HWC QUICK} (80-BLM)
The LHC energy information is sent via the “slow timing” to the CISV (VME card) and from there to the combiner (CS) (which distributes it to all TC in parallel)
Continuous check of:
Transmission by CRC (cyclic redundancy check)
Toggle bit to indicate updates; if timeout -> energy set to max. value
continuous
combiner
CISV

11. High Voltage Modulation {F, 1m, -, HWC QUICK} (40-BLM)
Check the connectivity up to the surface card before every fill
The bias current is increased by 100 pA and the 1.3 second running sum is measured and checked.
Modulate the high tension with a sine wave
Acquire modulated monitor signal, and check
MTF recording
sequencer (timeout), expert
combiner
monitor (gas not checked) DB

12. 10 pA Test {F, -, -, HWC CONTINOUS} (30-BLM, P2:10pA/1.3 sec run.sum)
Continuous check of the tunnel electronics : each minute the integrated injected current offset is checked
The bias current is increased in a control loop(possibility to correct for eventual offset in the electronics – e.g. ageing effects) so that a 10 pA offset is measured.
FPGA in CFC verifies signal levels
MTF recording
continuos
analogue tunnel el.
FPGA of CFC

13. Radioactive Source Test {M, 5m, -, HWC} (50-BLM)
Functional test of full acquisition chain with Radioactive Source
The procedure is described in a dedicated document made in collaboration with TIS.
The purpose is to create a signal on the chamber with the RA source and check its presence in the corresponding DAB card channels in the surface electronics and the DB.
MTF recording
manually
TIMBER (DB viewer)
monitor DB

14. EMC Test {F, 2h, -, HWC} (70-BLM)
The 40 us and 1.3 s running sum are measured with possible interference sources switched ON and OFF
Possible interference sources are:
Collimator jaw motors
Kicker magnets
Injection line magnets
manually
expert application
monitor DB

15. Double Optical Line comparison
Continuous
2 lines with CRC of transmission
Decision matrix
Continuous TC
FPGA of CFC

16. Channel / Card assignment SW check
Continuous
Check of software versions (FPGA of TC and CS)
Check of electronics serial numbers
Continuous
FPGA TC & CS
TC & CS
tunnel el., TC, CS
TC, CS

17. Transmission Time of Beam Permit Disabling
During machine checkout
For each octant
BLM takes away beam permit (by toggle functionality)
Measure the delay (by time stamps) between the BLM initiating and the dump system receiving the beam dump request
Reporting in MTF
manually
combiner & LBDS
combiner
LBDS

18. Change of Threshold Value with Beam Energy
During machine checkout
Ramp dipole in 4 sectors and observe DB logging of beam energy values
Reporting in MTF
manually
DB, Manual
dipole setting DB

19. MPS Functionality of BLM (without quenching)
Pilot beam of 5109 p+ at 450 GeV
Decrease thresholds (trim application) to very low value
Create local bump to force a beam dump request with very low level of losses
Measure delay between signal over threshold and the beam dump : the whole chain from the chamber to the LBDS, via the LBIS, is tested
manually
BLM system
simulations (magnet + monitor)
BLM system & LBDS

20. Provoked Quench (Transient + Steady State)
43 bunches of 41010 p+ at 450 Gev (below damage limit)
Steer the beam in the chosen magnet
Check level of losses and BLM readings at the quench level
Repeat for MQM, MQTL, MQ and MB
If no quench occurs the threshold DB values have to be reduced
Test justification and description in Chamonix XV proceedings, 2006, Magnet Quenches with Beam (A. Koschik)
A: transient losses and B: steady state losses
manually
BLM system
simulations (magnet + monitor)

21. THE END

23. The BIS (Beam Interlock System) Architecture
CIBU
Three ring-type systems:
LHC Beam 1 & Beam 2
SPS
Four tree-type systems:
LHC injection (Beam 1 & 2)
SPS extraction (BA4 & BA6)

24. Calibration / Threshold determination
Number of locally lost beam particles
Proton loss locations
Hadronic showers
Chamber response
Hadronic showers (energy deposition in magnet)
Deposited energy in the machine component
BLM signal
Quench and damage levels as function of loss duration (heat flow in magnet)
Threshold values
Machine component
Loss location
Detector position
Beam energy
Loss duration
Fraction of quench and damage level of the machine component