Safe Injection into the LHC V Kain ABCO

Safe Injection into the LHC V. Kain AB/CO Contents and scope • The need for machine protection at injection • Interlocking – hardware and software • Passive protection systems – collimators • Protection level simulation results • Commissioning aspects • Conclusions 10/7/2020 Verena Kain, AB-CO 1

Machine Protection at Injection • 2. 4 MJ in 450 Ge. V injected beam • Damage limit around 100 J/cc Holes in Cu : 450 Ge. V LHC p+ beam (2004 TT 40 materials test) ~2 x 1012 p+, ~5 % of injected batch 8 x 1012 p+ = ¼ of full batch • 7. 5 s LHC aperture at 450 Ge. V • Tight aperture in transfer line (MSI ~7 s) 5. 3 x 1012 p+ = 1/6 of full batch Inside, damage visible over ~1 m (melted steel) 10/7/2020 Verena Kain, AB-CO 2

What can go wrong: magnet trips, kicker flashovers, wrong settings… • Magnet trips can move beam by many s in short time (MSE: 40 s in 1 ms) • Kicker erratics, missings, timing etc. • Operator error • Corrupted settings Slow failures: – 10 s in > 2 -3 ms: interlocking Fast failures: – 10 s in < 2 -3 ms: interlocking + collimators Ultra-fast failures: – 10 s in few ms: collimators 10/7/2020 Verena Kain, AB-CO 3

Machine Protection Strategy • Avoidance: – Procedures to avoid dangerous situations • e. g. never inject intensity above damage level into empty LHC (beam presence condition) • Protection systems: – Active: surveillance + interlocks to inhibit injection • Software – typical reaction time: ~seconds • Hardwired - typical reaction time: ≥ 2 -3 ms – Passive: collimators for fast and ultra-fast faults • Collimators must be robust enough to withstand full injected batch → low Z material (C, h. BN). 10/7/2020 Verena Kain, AB-CO 4

Beam Presence condition • Injection of beam above damage level only possible if beam already circulating in LHC (beam presence) • Hardwire interlocked ! – SPS and LHC intensity must monitored reliably • Reliability and availability – 2 independent BCTs per machine? LHC beam permit SPS beam “safe” LHC beam presence Injection permit NO X X NO YES (low Intensity) YES NO NO NO YES X YES (high Intensity) Protects against many of the failures in the LHC (trips, settings, …) 10/7/2020 Verena Kain, AB-CO 5

Software interlocks • Software interlocks – Mostly used for less critical parameters and for redundancy: • beam quality, trajectory and losses in transfer line, etc. – Much slower than hardware interlocks, not failsafe… – Local reference values in front-ends for equipment surveillance compared with central reference values • Reference values are machine mode dependent 10/7/2020 Verena Kain, AB-CO 6

Hardwired Interlocks LHC energy LHC intensity SPS beam SPS HW Extraction HW bumped BP MSE current, girder MKE bumper currents Settings Transfer line HW Fast beam losses Extraction permit beam TED position SPS Beam Interlock Controller LHC Beam Interlock Controller Injection permit LHC beam permit LHC Settings LHC HW Injection HW BTV screens Transfer line collimators TDI position SPS intensity Movable TED beam dumps (stoppers) SPS extraction kicker Timing SPS LHC injection kicker Transfer Line LHC Timing TDI collimator Power Convertor Surveillance (PCS) and Fast Current Decay Monitoring (FCDM) are critical parts of the HW interlock system ! 10/7/2020 Verena Kain, AB-CO 7

Passive Protection for fast and ultra-fast failures • Protection of LHC aperture and MSI aperture: – TCDI collimators for failures upstream of injection regions – “generic” protection system with full phase coverage • Dedicated collimators for kicker failures: – MKI failure: TDI + TCLI are 90° downstream – MKE failure: TPSG is 90° downstream • No dedicated collimators for septum failures – Protection from MSE and MSI failures interlocking 10/7/2020 Verena Kain, AB-CO 8

TCDI Transfer Line Collimation • Close to LHC and MSI (last 300 m matching section of TLs) • Robust, based on TCS design (1. 2 m C jaw) • FLUKA model of TI 8 local shield for each TCDI • 3 collimators / plane (0 -60 -120°) • Setting: 4. 5 s, tolerances: ≤ 1. 4 s 0 -60 -120 degree x’ collimators • 2 motors/ jaw (angular control) • Protection level 6. 9 s (simulated with Monte-Carlo including all imperfections: b beat, mismatch from SPS, tolerances…) 10/7/2020 Verena Kain, AB-CO 6 s 120 60 oo x amax 6. 9 s LHC aperture to protect at 7. 5 s 9

TCDI in TI 8 TCDIH 060 10/7/2020 Verena Kain, AB-CO 10

TDI – TCDD - TCLI • Protects LHC (especially D 1) against MKI failures • 90° downstream of the MKI. ~4 m long h. BN jaws • FLUKA model: local protection with mask -> TCDD (1 m, Cu) – prevents damage in all failure cases, and quenches in most cases • Auxiliary collimators TCLIs to complete system – For MKI-TDI phase advance ≠ 90°, and for flexibility (halo load…) – At nx 180°± 20° from TDI (1. 2 m long C jaws) MKI 10/7/2020 Verena Kain, AB-CO 11

TDI – TCDD - TCLI LEFT OF IP 2 Kicker MKI TCDD TDI MKI +90˚ RIGHT OF IP 2 TCLIM TCLIA TDI +200˚ TCLIB TDI +340˚ TCT design, half jaw, low Z two beams in one pipe 10/7/2020 TCS design, beams in separate pipes Verena Kain, AB-CO 12

Protection level simulations Safe LHC injection losses on aperture below 5% damage limit during injection • Extensive tracking simulations to check performance • MKI flashover scanned with TDI, TCLI setting • Full Monte Carlo of single failures at injection – All magnet and kicker families (SPS extraction, Transfer Line, LHC injection) for LSS 4 - TI 8 – IR 8 – Full TL + LHC injection region aperture model – All imperfections and errors included 10/7/2020 Verena Kain, AB-CO 13

MKI flashover simulations • TDI, TCLI setting of 6. 8 s, to guarantee max. 5% above 7. 5 s • Increasing system aperture introduces risk of damage N/N 0 of particles with amplitudes >7. 5 sy 10/7/2020 Verena Kain, AB-CO 14

Single failure tracking Monte Carlo results (1000 runs per failure) Family Tolerable error [Dk/k 0] required reaction time [ms] Covered by LHC TL TCDI/PCS mplh (LSS 4 bumper) 0. 185 201. 0 MKE (LSS 4 kicker) 0. 125 - TCDI - MSE (LSS 4 septum) 0. 005 0. 1 TCDI - MBHC (TT 40 H bend) 0. 005 5. 1 TCDI PCS / FCDM MBHA (TT 40 H bend) 0. 015 39. 4 TCDI PCS MBI (main TI 8 bends) 0. 003 2. 7 TCDI FCDM MCIBH (start TI 8 H bend) 0. 630 389. 0 TCDI PCS MBIAH (end TI 8 H bend) 0. 005 13. 2 PCS MBIBV (end TI 8 V bend) 0. 003 39. 5 PCS 3 MCIAV(end TI 8 V bend) 0. 225 124. 0 PCS TCDI MSI (LHC injection septum) 0. 003 3. 0 FCDM n/a • PCS = standard Power Convertor Surveillance (≥ 3 ms) • FCDM = Fast Current Decay Monitor (~1 ms) 10/7/2020 Verena Kain, AB-CO 15

Discussion of results • LHC protection looks OK, provided FCDM for MSI – Detect and react to 0. 3% change in 2. 5 ms • TL needs FCDM for MSE septum (reduce risk window), MBI and MBHC – MKE and MSE faults can still cause damage to the TL… possible solutions being studied • All other single failures are covered for TL & LHC – TCDI system gives full protection from upstream failures – Failures at end of line: slow enough for PCS and FCDM • More complicated scenarios not yet studied – Grouped powering failures: e. g. general power cut – Combined failures • Fault of machine protection system + other failure • e. g. wrong setting of passive absorber + trip of magnet family 10/7/2020 Verena Kain, AB-CO 16

Commissioning aspects • Limited role of protection systems for early stage of LHC commissioning. (SPS extraction, SPS safe beam, TI 8 interlocks and LHC injection BIC needed !) • Injection protection must be fully operational for injected intensity above damage level = 15 bunches • Many parts can be commissioned without beam: – LHC injection BIC + matrices + data exchange; collimator movements + interlocks; FCDM, PCS, logging, software, etc • Beam is essential for commissioning of: – SPS & LHC safe beam and beam presence (BCTs) – TDI/TCLI/TCDI jaw alignment – Tests of full interlock system (EMC, …) 10/7/2020 Verena Kain, AB-CO 17

Commissioning of TCDI system • Setting up TCDI with beam: Transmission Measurement – Angular jaw alignment – Beam size measurement • Use BCTs in SPS and downstream of TCDI (in LHC injection region - not in layout yet) • Move TCDI jaws through beam, measuring transmission… – Required beam intensity ~1010 depending on BCT resolution – Impact on LHC: ”inject – TDI dump” or “inject and dump” mode 10/7/2020 Verena Kain, AB-CO 18

TCDI setting up with beam - tests First Results of transmission measurement for TCDI (TCS) setting up. Measured transmission vs. angular misalignment – looks promising Methods tested in simulation with realistic parameters and tolerances Simulated data Attainable accuracy can be predicted – expect able to align to ~100 mrad. Simulated transmission vs. angular misalignment: 10/7/2020 Verena Kain, AB-CO 19

Commissioning of TDI /TCLI • Setting up TDI and TCLI with beam • Beam axis measurement : circulating pilot beam • Transmission Measurement for jaw alignment – – • similar to TCDI inject-dump required intensity depending on BCT resolution (max. ~1010) Beam size measurement : circulating pilot (max. ~10 10) – – Transmission measurement, jaw moved through beam Reconstitute transverse beam profile from transmission vs. position Simulations must still be carried out to test the methods with the special TDI geometry (different materials, …). 10/7/2020 Verena Kain, AB-CO 20

Conclusions • Machine protection at injection is crucial – To ensure only safe beam is injected into LHC during commissioning – When injected intensities exceed 2 1012 p+ • LHC protected against many failures by “beam presence” condition • Comprehensive tracking simulations extensively used to define protection systems and determine protection levels • LHC fully protected with foreseen active and passive protection – Require Fast Current Decay Monitor to measure 0. 3% DI in ~1 ms – Hardware and software interlocking is being specified • At present the protection systems cannot fully exclude TL damage • Simulations will be extended to grouped and combined failures • Commissioning of the injection protection system is being prepare – Methods for setting up protection collimators being worked out 10/7/2020 Verena Kain, AB-CO 21