Beam loss monitoring in SPS - plans for LS2 Steen Jensen, BE-BI-SW | BI technical board, 15 November 1 2018 | https://wikis.cern.ch/display/BEBI/BLM+for+SPS
Overview SIS PostMortem SPS BLRSPS En-/disable dump channels Reset integrator Reset dump (general) Reset dump (channels) Reset watchdog timer ADC values per channel (raw beam loss values) En-/disable dump Set dump BIS ch0 BLM ch1 DAC thresholds BLM 1-16 ch2 BLM Disassemled BLM ionization chamber ch3 BLM https://cds.cern.ch/record/930275/files/ab-2006-009.pdf ch4 BLM ADC ch5 Amplifier BLM … DAC1 Multiplexer DAC8 ch6 BLM /8 /8 … … ch7 Comparators Analogue integrated values BLM CIBU OR Integrators BI_BLMADC #0 … DAC1 DAC8 BLM /8 … /8 … Comparators power supply BI_BLMDMP #1 Steen Jensen, BE-BI-SW ch32 BLM New version (v1) From ch33 BLM only BI_BLMDMP card ch34 in upstream FEC BLM ch35 BLM ch36 ADC ch37 Amplifier Multiplexer Maximum 36 BLM ch38 channels per FEC ch39 Analogue integrated values Integrators BI_BLMADC #N, N <=4 Ch36 = Voltage of BLM power supply Ch37 = Current of BLM power supply Ch38 = Unused BLM ionization chambers in LHC FEC Ch39 = Unused Steen Jensen, BE-BI-SW | BI technical board, 15 November 2 2018 | https://wikis.cern.ch/display/BEBI/BLM+for+SPS
Deployment Transfer lines: LHC(TI2, TI8), AWAKE(TT40, TT41) • Active only on fast extractions • Single-shot => beam dump makes no sense => Prevents beam permit on following cycles, to be reset by operator. Long Straight Sections (LSS) • Monitoring throughout cycle • Hardware based beam-dump in < 1ms Arcs – the sections between LSS’s • Monitoring throughout cycle • Software based beam-dump in < 20ms • Software improvements possible SPS overview, from https://cerncourier.com/protons-on-the-doorstep-of-the-lhc/ Steen Jensen, BE-BI-SW | BI technical board, 15 November 3 2018 | https://wikis.cern.ch/display/BEBI/BLM+for+SPS
Current Principle for Arc installations • Start Acquisition Response time up to 20ms Integration time, Δ t tick = 20ms Measure @ tick Stop Acquisition • Only monitors integrated loss since cycle start CYCLE A CYCLE B time Steen Jensen, BE-BI-SW @Measure: @Start acquisition: @Stop acquisition: for ( all channels ) { for ( all channels ) { for ( all channels ) { Acquire and store loss-value Reset & re-start hw integrator Publish loss-values if (loss-value > threshold) { } } dump beam } } Steen Jensen, BE-BI-SW | BI technical board, 15 November 4 2018 | https://wikis.cern.ch/display/BEBI/BLM+for+SPS
New functionalities for Arc (and LSS) installations OP requests for the SPS BLM system: • Request: Reduce the integration time • Solution: 5ms instead of 20ms (hardware access time reduced from ~12ms to ~2ms) • Request: Improve detection of fast losses • Solution: 4 new interlocking running-sums: • Veto-able per channel • Adjustable threshold per channel • Adjustable width per running-sum • Sub-sets published every BP for visualization • Timestamped max-values published end-cycle for diagnostic and trimming purposes • Additional functionality for RP (not interlocking) • Ambient losses • Measured from ejection to injection • Fast extraction losses • Measures losses in smallest possible time window covering the extraction Steen Jensen, BE-BI-SW | BI technical board, 15 November 5 2018 | https://wikis.cern.ch/display/BEBI/BLM+for+SPS
New vs. Current Principles Post-LS2 principle Current principle Start Acquisition Start Acquisition Measure @ tick Measure @ tick Fast extraction start Stop Acquisition Fast extraction end Stop Acquisition CYCLE A CYCLE A CYCLE B CYCLE B Δ t tick = 5ms Δ t tick = 20ms time time running-sum Steen Jensen, BE-BI-SW Steen Jensen, BE-BI-SW @Measure: @Start acquisition: @Stop acquisition: for ( all channels ) { for ( all channels ) { for ( all channels ) { Acquire and store loss-value Reset & re-start hw integrator Publish loss-values @Stop acquisition: if (loss-value > threshold) { @Start acquisition: } @Measure: } For ( all channels ) { dump beam for ( all channels ) { For ( all channels ) { Publish max running-sums } Acquire & publish ambient loss Acquire and store loss-value Publish fast-extraction loss } Reset & re-start hw integrator Process running-sum-1 Reset & re-start hw integrator } Process running-sum-2 } Process running-sum-3 Process running-sum-4 Process Cycle-running-sum “Process” means: } • Calculate difference from loss X ticks ago • Compare difference to threshold • Dump beam if difference > threshold @Fast extraction start: @Fast extraction end: for ( all channels ) { for ( all channels ) { Thresholds to be set by OP Register latest loss measurement as Register latest loss measurement Channels can be vetoed so they do not cause beam dumps fast-extraction-start Calculate/record difference from fast-extraction-start } } Steen Jensen, BE-BI-SW | BI technical board, 15 November 6 2018 | https://wikis.cern.ch/display/BEBI/BLM+for+SPS
Additional slides Steen Jensen, BE-BI-SW | BI technical board, 15 November 7 2018 | https://wikis.cern.ch/display/BEBI/BLM+for+SPS
Deployment Arcs • BLRSPS_BA1: 36 channels • BLRSPS_BA2 : 36 channels • BLRSPS_BA3 : 36 channels • BLRSPS_BA4 : 36 channels • BLRSPS_BA5 : 36 channels 297 channels • BLRSPS_BA6 : 36 channels x • BLRSPS_BA80 : 11 channels 297 channels => => => 24 users 35.640 thresholds x 5 running-sums LSS’s • BLRSPS_LSS: 12 channels • BLRSPS_LSS: 32 channels • BLRSPS_LSS: 8 channels • BLRSPS_LSS: 4 channels • BLRSPS_LSS: 14 channels Steen Jensen, BE-BI-SW | BI technical board, 15 November 8 2018 | https://wikis.cern.ch/display/BEBI/BLM+for+SPS
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