1. Disabling Rules

2. Why “disable” BLM monitors
If a BLM channel is not working correctly the internal sanity checks of the BLM system fail and the LHC cannot operate. This is also the case for monitors which are not connected to BIS including the dump line monitors. Also, the BLM connectivity check will not allow LHC operation in case a channel is declared false for “cable connected” flag, but actually a monitor is connected on the channel. All channel connections and monitor types declared in the LSA database are verified by the sanity checks.
“disabling” of a monitors means to:
Physically disconnect the input from the analogue readout electronics (e.g. BLM hardware piquet)
Set the “cable connected” flag in the LSA database to false.
At certain locations, access to the monitor and/or to part of the analogue cabling is not always possible e.g. for safety reasons. At the same time BLM channels have shown in general sufficient redundancy. In case of hardware failure, it is always the default action to repair the fault. But in the rare cases where this is not possible (e.g. would require long cooldown), individual channels can be disabled according to the rules set out in the document.

3. Aim
In 2013 and in February 2015 new Run2 disabling rules for LHC BLM were decided by MPP.
A couple of “pre-set” rules and the other monitors on a case-by-case basis.
A case-by-case requires two BLM experts + rMPP representative + concerned equipment representative  time consuming decision and procedure
Application of “pre-set” rule requires BLM expert (2 at the moment, but can be reduced to BLM hardware piquet in the future), as safety will be ensured by LSA DB. In case repair is not possible, rMPP can authorise the BLM hardware piquet to disable a monitor.
Now: aim to
create additional “pre-set” rules for monitors not previously covered and remain with as few as possible case-by-case locations
Open up rules if they are too tight

4. Rules decided 2015 and Feb 2015 Pre-set-Rules decided Feb 2015
Inner triplet
Arc
LSS quadrupoles
Ion (partly)
Not allowed to disable:
LS3, LS7, all DS, all collimators and movable absorbers
All others: case-by-case

5. New Rules No monitor in a _CRIT family shall be disabled.
 when monitors are moved to _CRIT family, the disabling flag has to be changed at the same time
In the LHC ring: monitors not connected to BIS can be disabled
Implementation:
Only one set of rules can be implemented in LSA DB, active for ions and protons  need to implement the stricter rule

6. Arc and DS (?)
In the LHC arc, four ICs are installed around each quadrupole magnet, two for each beam. At each dipole-dipole interconnect, one IC is installed on top of the interconnect. It reads losses from both beams equally. A maximum number of one IC per beam and quadrupole magnet is allowed to be disabled. If one arc IC was disabled in the half cell n, the corresponding monitor of the same family in the half-cells n-2, n+2 shall remain operational. In addition, one dipole-dipole interconnect IC per half-cell can be disabled, but only if no neighboring quadrupole monitor is disabled.
 extend to DS ?
BLM system considers Q7 as part of the DS! DS: including Q7 up to Q11
2-3 BLMs per beam per quad
1 dipole-dipole BLM in half-cells 8 till 10
2 dipole-dipole BLMs in half-cell 11
 require minimum of 1 BLM per quad and beam (P1, P2, or P3)
 on dipole-dipole BLM per half cell can be disabled if all neighboring quads have at least 2 BLMs per beam (no matter which position)
 need to check for critical BLMs for ions and protons among the DS monitors!
Re-location of 2nd position quadrupole BLM to the close-by dipole-dipole interconnection

7. Extra monitor in the DS
Installed horizontally at different times either:
For dispersive losses (start-up) only
 can be disabled?
For ions losses (start-up or LS1) only
Now part of special ion family
 can be disabled for proton run only?  no pre-set DB rule
Not part of special ion family (still needed for ion losses?)
For both reasons

8. LSS Quads (extend to IP3 and IP7 ?)
At least 2 monitors per beam shall remain operational on each LSS quadrupole. (no matter the positions)
Rule currently for all LSS except IP3 and IP7
Can it be extended to IP3 and IP7? (cooldown period for access!)
Check for potential critical positions for protons and ions

9. Collimators and movable or intercepting devices
IP7 and IP3 ?
High redundancy of monitors and access problematic
Check which monitors are critical (can not be disabled), e.g. last TCP, last TCSG (in a row of several) per beam
Collimators and movable or intercepting devices outside of IP3 and IP7: can not be disabled:
TCL, TCT, wire scanner, BGV, roman pots

10. Injection and extraction elements
In the ring?
In the dump line: any BLM can be disabled, but not two in a row?
Before, inside and after the dump: disabling on a case by case basis (need to see new installations and possible redundancies)

11. Others
Monitors for experiments RF
non-intercepting BI

12. Other monitors in the triplet region
BLMEL.01R1.B2I10_BPMSW.1R1
BLMEL.01L2.B2E10_BPMSW.1L2
BLMEI.01L2.B1E10_MBWMD connected to BIS BLMEI.01L2.B1T10_BKGD connected to BIS
BLMEI.01L2.B1B10_BKGD connected to BIS
BLMEL.01R2.B2E10_BPMSW.1R2
BLMEL.01L5.B2I10_BPMSW.1L5
BLMEL.01R5.B2I10_BPMSW.1R5
BLMEL.01L8.B2I10_BPMSW.1L8
BLMEL.01R8.B1I10_BPMSW.1R8
BLMEL.01L1.B1I10_BPMSW.1L1

13. SPARE SLIDES

14. IP2 left currently installed ICs at MBs; all for B2 - inside
New locations
7 ICs
IP2 left currently installed ICs at MBs; all for B2 - inside
6 ICs
7 mobile?
P2 external
IC+SF
P2 as defined in (Grishin, 2013) P2