Required Flat Top Corrections to BLMs due to Betatron Cleaning A. Mereghetti, on behalf of the LHC Collimation Team 07th June 2016 A.Mereghetti

Introduction Collimation system designed to stand temporary drop downs in beam lifetime: 500kW beam losses in 1-10s; 100kW beam losses in steady state; Let’s re-tune the BLM thresholds such that we don’t dump un-necessarily beforehand: Cautious approach: 200kW / 40kW (1-10s / steady state) for the moment; Use qualification LMs (RS09, both beams, both planes) to spot all those BLMs that would trigger a premature beam dump; Change present FT corrections on ‘long’ RSs (eg from RS08 onwards) according to scale factors identified with RS09; …we already dumped twice because this work could not have been done beforehand! Correct estimation of power loss crucial (remember premature beam dump during 2015 proton quench test): LMs: analysis repeated for two sets of LMs for consistency: FT: nominal bunches used -> higher BLM signals + less noisy BCT signal; After insertion of XRPs: machine configuration actually requiring protection; Compare different methods of estimating the power loss and chose the most reasonable one; 07th June 2016 A.Mereghetti

BLM Threshold Scaling 07th June 2016 A.Mereghetti

B1H After XRP insertion Flat Top IP6 – MQY.4R6 & MQY.5R6 IP1&5 – TCTPx.4Ly Flat Top IP7 – MQTL.6R7 & TCLAs.x6R7 07th June 2016 A.Mereghetti

Without considering correction due to debris All Beams / Planes XRPs IN FT BLM name factor family MF BIS - BLMQI.04R6.B1E10_MQY 1.04 THRI.LS.P1_MQY_FT 0.4 1 BLMQI.05R6.B1E10_MQY 1.15 BLMQI.06L7.B2I20_MQTL 1.10 1.05 THRI.IP7.P2_MQTL_FT 0.1 BLMQI.05R7.B1E30_MQWA.E5R7 1.03 THRI.IP7_MQW_FT BLMQI.06R7.B1E10_MQTL 1.24 THRI.IP7.P1_MQTL_FT BLMQI.06R7.B1E20_MQTL 1.12 1.02 BLMTI.04L7.B1E10_TCSG.D4L7.B1 1.11 BLMTI.04L7.B1E10_TCSG.A4L7.B1 1.14 THRI_7_TCSG BLMTI.06R7.B2I10_TCSG.A6R7.B2 1.22 THRI_7_TCSG_F5 BLMTI.06R7.B1E10_TCLA.D6R7.B1 1.34 1.13 THRI.06_7_CD_TCLA BLMTI.07R7.B1E10_TCLA.A7R7.B1 THRI.07_7_AB_TCLA BLMTI.04L1.B1I10_TCTPH.4L1.B1 6.20 THRI_TCT 200 kW Without considering correction due to debris XRPs IN FT BLM name factor family MF BIS - BLMAI.05R6.B1E10_DFBLB 1.16 THRI_DFB 0.1 1 BLMQI.04R6.B1E20_MQY 1.90 THRI.LS.P2_MQY 0.5 BLMQI.05R6.B1E20_MQY 1.13 BLMQI.06L7.B1E20_MQTL 1.02 THRI.IP7.P2_MQTL_FT BLMQI.06R7.B2I20_MQTL 1.93 BLMQI.06L7.B2I10_MQTL 1.45 THRI.IP7.P1_MQTL_FT 0.4 BLMQI.05L7.B2I10_MQWA.E5L7 1.82 THRI.IP7_MQW_FT BLMQI.05L7.B1E10_MQWA.D5L7 1.87 BLMQI.05R7.B2I10_MQWA.D5R7 1.27 BLMQI.05R7.B1E30_MQWA.E5R7 1.79 500 kW Take values for XRPs IN 07th June 2016 A.Mereghetti

(Avoidable) Beam Dumps Two beam dumps so far due to high ``betatron’’ losses: Fill 4914 (600b): Wed 11th May 2016, 19:00:37 – 4min after start of squeeze; Trigger: TCLA.D6R7.B1 (RS08); B1H transverse instability lead to high losses in IR7; Beam losses at ~170 kW (cfr. 200 kW  FT LMs requires 13% increase); Settings in IR7 changed wrt 2015! Fill 4975 (1854b): Tue 1st June 2016, 01:48:30 – 4min after start of Totem BP; Trigger: TCTPH.4L1.B1 (RS08); B1H losses in IR7: blown up beam (from beginning of ramp) being scraped by TCP.H when TOTEM BP ongoing (CO changes); large secondary and tertiary halo; TCTs at 9s (2016) intercept more than at 13.7s (2015), with higher BLM signals; BLM thresholds at TCTs compatible with regular cleaning at 13.7s, not at 9s; Beam losses at ~30 kW (cfr. 200 kW  XRPs IN LMs requires increase x6.2);  TCT settings changed wrt 2015! 07th June 2016 A.Mereghetti

Reconstructing the Beam Power Loss 07th June 2016 A.Mereghetti

Methods A correct estimation of the power loss is vital for a proper scaling of the thresholds - remember premature beam dump during 2015 proton quench test! Different methods compared: ‘Usual’ - Use 1 Hz BCTFR data to get the highest drop in beam intensity: correlate to highest BLM signal (RS09); 1 LM = 1 point; ‘differential’ approach; ‘Fit’ - Fit through 50 Hz BCTFR data to get the highest drop in beam intensity: ‘Pattern recognition’ - Mimic 1 Hz BLM data with 50 Hz BCTFR data (see later): correlate to time evolution of BLM signal (RS09) during LM; 1 LM = many points!  ‘calibration’ curve; ‘Integral’ - Use 1 Hz BCTFR data to get total loss of beam intensity for a LM (~5s): Correlate to change of RS10 and RS12; ‘integral’ approach – less spiky… 07th June 2016 A.Mereghetti

Method 1 – ‘Usual’ LMs with XRPs IN B1 B2 Use 1 Hz BCTFR data to get the highest drop in beam intensity: correlate to highest BLM signal (RS09); 1 LM = 1 point; ‘differential’ approach; LMs with XRPs IN B1 B2 Drawbacks: 1 Hz BCTFR data are averages over 1s whereas RS09 integrates over the last 1.3 s; 07th June 2016 A.Mereghetti

Method 2 – ‘Fit’ 1.31s LMs with XRPs IN Fit through 50 Hz BCTFR data to get the highest drop in beam intensity: correlate to highest BLM signal (RS09); 1 LM = 1 point; ‘differential’ approach; 1.31s LMs with XRPs IN Drawbacks: Good method for constant loss rates along the LM measurements  What if change of slop during the integration time of RS09? 07th June 2016 A.Mereghetti

Method 3 – ‘Pattern Recognition’ Mimic 1 Hz BLM data with 50 Hz BCTFR data (see later): correlate to time evolution of BLM signal (RS09) during LM; 1 LM = many points!  ‘calibration’ curve; ‘differential’ approach; (Data from occurred beam dumps used for the sake of clarity) 07th June 2016 A.Mereghetti

Logging of BCTFR Data Data from fill 4914 BCTFR data: 1 Hz data logged every 1.02s; 1 Hz data is average of 50 Hz data; 50 Hz data miss the point every 1.02s; Timestamps of 1 Hz and 50 Hz shifted by 29s; 50 Hz logging of BCTFR data used to reconstruct the power loss at dump: Data from fill 4914 07th June 2016 A.Mereghetti

BCTFR Data and BLM Data 1.31s Data from fill 4914 1Hz logging of RS09: last computed value (integration over 1.31s divided by time interval), refreshed every ~80ms; 1.31s Data from fill 4914 07th June 2016 A.Mereghetti

Correlating BCTFR Data and BLM Data (I) RS09 integrates losses over 1.31s (refresh every ~80ms);  Proportional to the amount of beam lost in the same time interval; Data from fill 4914 07th June 2016 A.Mereghetti

Correlating BCTFR Data and BLM Data (II) Why not taking on 50 Hz BCTFR data differences between points 1.31s apart from each other and try to reproduce the pattern of the BLM signal? Data from fill 4914 07th June 2016 A.Mereghetti

Correlating BCTFR Data and BLM Data (III) In the end, the BLM pattern follows a specific sub-sample of the one reconstructed with the 50 Hz BCTFR data, made of points 1s apart from each other; Data from fill 4914 07th June 2016 A.Mereghetti

Correlating BCTFR Data and BLM Data (IV) In the end, the BLM pattern is just a sub-sample of the reconstructed one, made of points 1s apart from each other;  let’s take the set of points which best reproduces the BLM pattern; Data from fill 4914 07th June 2016 A.Mereghetti

Correlating BCTFR Data and BLM Data (V) We automatically get a set of couples (PL,BLM) that can be fit to get the ‘calibration’ curve for that BLM; Data from fill 4914 07th June 2016 A.Mereghetti

Correlating BCTFR Data and BLM Data (VI) Data from fill 4975 Clearly more noisy signals… …scraping tails… 07th June 2016 A.Mereghetti

Correlating BCTFR Data and BLM Data (VII) Flat top XRPs IN 07th June 2016 A.Mereghetti

‘calibration’ in Gy/kJ, not Gy/s / kW; Method 4 – ‘Integral’ Use 1 Hz BCTFR data to get total loss of beam intensity for a LM (~5s): Correlate to change of RS10 and/or RS12; 1 LM = 1 point; ‘integral’ approach - less spiky… RS12 RS10 LMs with XRPs IN Nota Bene: ‘calibration’ in Gy/kJ, not Gy/s / kW; Drawbacks: Good method if LMs are carried out clearly separated in time (e.g. 90s)  mixing of signals when LMs are performed interleaved by the same time as the integration window; …maybe for the future… 07th June 2016 A.Mereghetti

‘Pattern Recognition’ Comparing the Methods promising Power Loss [kW] ‘Usual’ ‘Fit’ ‘Pattern Recognition’ RS10 RS12 B1H 3.413 1.898 1.56 1.623 B1V 2.195 0.536 0.585 0.508 0.608 B2H 3.14 1.953 2.61 3.292 2.913 B2V 0.899 0.284 0.302 0.336 0.323 ADT on? Used in present scaling Relatively good agreement Comparing the fitting curves for B1H m [mGy/s / kW] q [mGy/s] XPRs IN 4.995 -0.513 FT 3.755 0.124 4914 4.387 -4.237 4975 3.134 7.642 07th June 2016 A.Mereghetti

Troubles with Logging When using NUMERIC vars, LOSS signals of all necessary BLMs are correctly logged;  This is not the case for the NUMERIC vars storing the thresholds: Name IR cell N *30_MQY* all but IR3/IR7 4,5,6 36 *30_MQML* IR1/2/5/8 5,6 24 *30_MQM* IR2/8 5 4 *30_MQTL* IR3/IR7 6 8 *ULO* 15R8 2 B0T10_MQ-MBB_09L5 1 *LE* (*MBB*-excluded) 26 *ACSGA* IR4 3 *MBW* IR7 *MKI* Name IR cell N *MKD* IR6 5 6 *X5FC* (A,B - IT-excluded) IR5 4 *BGI* IR4 2 *TCD* (SA,SB,D,QA,QM) 11 *11_TCSP* *TCAPA* IR3/IR7 *TAN* IR1/5 *TCH* (SS,SH,SV) 8 *TCSM* 36 *DRIFT* 3 07th June 2016 A.Mereghetti

Reserve Slides 07th June 2016 A.Mereghetti

B1V Flat Top After XRP insertion 07th June 2016 A.Mereghetti

B2H Flat Top After XRP insertion 07th June 2016 A.Mereghetti

B2V Flat Top After XRP insertion 07th June 2016 A.Mereghetti

Fill 4914 (600b) Loss map (RS09) at dump. Loss map (RS09) at dump. Wed 11th May 2016, 19:00:37 – 4min after start of squeeze; Trigger: TCLA.D6R7.B1 (RS08); B1H transverse instability lead to high losses in IR7; Beam losses at ~170 kW (cfr. 200 kW); Loss map (RS09) at dump. Loss map (RS09) at dump. RS09 07th June 2016 A.Mereghetti

Troubles with Logging of Timber vars Disclaimer: these issues were found while analyzing the LMs used here, i.e. 2016-04-14 (FT – fill 4797) – 2016-04-22 (XRPs IN – fill 4842). More recent LMs (eg fill 4914 and 4975) seem to be affected by other problems, not fully addressed here… 07th June 2016 A.Mereghetti

Troubles with Logging Header of VECTORNUMERIC vars LHC.BLMI:LOSS_% and LHC.BLMI:THRESH_% main source of troubles for analysis of LMs and scaling: 3741 BLM names in header, and 3745 numbers: the four additional BLMs are not trailed but mixed with the others, in particular: … BLMQI.06R1.B1E30_MQML; Fake1; Fake2; BLMEI.07R1.B1E10_XRP; Fake3; Fake4; BLMEI.07R1.B1E20_XRP-RUN1; They are usually filled with 0.0; Some monitors are swapped: BLMQI.01L5.B1I30_MQXA with BLMEL.01L5.B1I10_BPMSW.1L5; BLMQI.01R5.B2I30_MQXA with BLMEL.01R5.B2I10_BPMSW.1R5; BLMTI.04L6.B2I10_TCDQM.4L6.B2 with BLMTL.04L6.B2I10_TCDQM.4L6.B2; BLMTI.04R6.B1E10_TCDQA.B4R6.B1 with BLMTL.04R6.B1E10_TCDQA.B4R6.B1; 07th June 2016 A.Mereghetti