1	LHC Beam Loss Monitor Post Mortem & Memory Requirements Design Considerations 2:
2	Functional Specifications POST-MORTEM ANALYSIS (chap. 6.9 & 9.8) In case of a beam dump, the BLM system should help answering the following questions: is the beam dumping clean or were there unexpected losses around the machine? what is the cause of the dump action: beam losses triggering the BLM or internal magnet quench protection interlocks? Other machine interlocks without prior beam losses? The signals of all monitors should be buffered for the last 100 - 1000 turns, such that they can be read out and analysed after a beam-dump. In addition, the average rates of all monitors should be easily available for time scales of a few seconds and 10 minutes before a beam-dump.
3	PM equipment “categories” We can sub-divide the various LHC systems into the following categories: Triggered systems (via specific external event) : • beam instrumentation • power converter system • RF system • … Self-triggered systems : • quench protection system • beam dump system • power converter system (on faults ?) • … Non-triggered systems : • Interlock system, BIC & PIC
4	Protection Systems Transient System required to record fast signals and freeze on trigger Logging System required to continuously (on time or on change) record slow or infrequent changes Alarms System required to send fault events to the Central Alarm Server, (CAS). External Trigger System required to respond to general PM trigger Internal Trigger System required to autonomously record all protection actions Date Operational for Sector Test or Beam Commissioning
5	Protection Systems The correct functioning of all these systems is required to ensure proper protection of equipment. (Beam Dumping System, Beam Loss Monitors, Energy Extraction Switches, Quench Protection, etc) Beam Loss Monitors: They are included here as a critical part of the machine protection system, their status should be logged. Beam loss information should be recorded at 100 Hz, depth 20s or Beam Loss 2000 channels * 100Hz * 20s = 4E6 values (Note: Beam Position 2000 channels * 1000 T = 2 E6 values)
6	Threshold Comparator (1) Observation Time-Windows Adding newest data Subtracting oldest data Capacity of FIFO Th & W table values depending on: Beam Energy Ion. Chamber Position Time-Window Read 2 values from a table of 576 values Comparisons on chip 96 times in parallel (6 TimeWind.*16 Ion)
7	Calculations Acquisition every 40μs: 25 KHz 16 Ion. Chambers per Card. 8 bit values 1024K x 36bit SRAM can hold 10.24s of data Write Clock = 400 KHz & Read Clock = 2.4 MHz 10 seconds need 250K x 8bit per Ion. Chamber. Acquisition every 90μs (1 turn): 11 KHz 16 Ion. Chambers per Card. 8 bit values 1024K x 36bit SRAM can hold 23.04s of data Write Clock = 180 KHz & Read Clock = 1.1 MHz 10 seconds need 110K x 8bit per Ion. Chamber. *Note that 2 SRAMs can be available to keep the data under manipulation and 1 SRAM for PM.
8	Threshold Comparator (2) When A has been filled with 10 acquisition values, the sum of them is appended as a value to B. When B has been filled with 10 values, the sum of them is appended as a value to C, and so on. In that way sums of tenths, hundreds, thousands, millions, … of values are created and kept.
9	Calculations(2)
10	Quench Levels as number of clocks