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CNGS Operation

CNGS Operation. J. Wenninger. Part 1 : CNGS beam operation. Protons on their way to the target. CNGS specialties. Part 2 : Extraction Interlock System. Detailed description. Acknowledgments : Edda, Verena, Konrad … for figures, photos and numbers. CNGS ‘Facility’.

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CNGS Operation

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  1. CNGS Operation J. Wenninger Part 1 : CNGS beam operation. Protons on their way to the target. CNGS specialties. Part 2 : Extraction Interlock System. Detailed description. Acknowledgments : Edda, Verena, Konrad … for figures, photos and numbers.

  2. CNGS ‘Facility’ • A dedicated primary beam line (TT41), a target chamber (target T40), a decay tube & a muon detection infrastructure. • ‘Attached’ to the LSS4/East extraction channel.

  3. CNGS Tunnels

  4. Our Goals Send 4.8x1013 protons to target in every CNGC cycle  Tune, tune, tune … • Keep the beam within +- 0.5 mm of the target axis • to prevent damage ! • Interlocks, interlocks, interlocks…

  5. CNGS Magnetic Cycle • The CNGS beam magnetic cycle is almost identical to the FT beam: the only difference is the much shorter 400 GeV flat top – only 90 ms: • 2 fast extractions are programmed 20 ms and 70 ms from the start of the flat top. P (GeV/c) • Same optics and tunes than FT beam: • Q = (~26.62,~26.58) • Injections at 0 and 1200 ms. • Ramp from 1260 to 4200 ms. • Flat top from 4200 to 4290 ms. • Cycle length 6 s – 5 BPs. Time (ms)

  6. CNGS Beam CNGS beam = FT beam with more intensity, up to 4.8x1013 p. LHC FBCT • Longitudinal: • 2 batches of ~10.5 ms (5/11 of SPS). • 2 gaps of ~ 1 ms (kickers !). • Bunch spacing 5 ns. • Bunch length at 400 GeV ~ 2 ns. • Transverse: • Normalized emittance e*  8-10 mm. • Beam sizes at 400 GeV (10 mm): • -Wire scanner 51995 sH/V 1.4/0.8 mm • -Target T40 sH/V 0.5/0.4 mm Batch 1 Batch 2 Kicker gaps

  7. LSS4 Fast Extraction Channel • 5 extraction kicker magnets (MKE) operated at 50 kV. • 6 septum magnets (MSE), installed on a movable girder. • 4 horizontal and 4 vertical bumper magnets: • - Horizontal extraction bump of 31.1 mm @ monitor BPCE.418 • TPSG protection element for the MSE.

  8. Extraction Kicker MKE • Key constraint for the fast extraction : • < 0.1% beam loss during extraction ! •  Radiation in ECX4 + activation of extraction channel • This means that : • Beam gaps must be VERY clean. • MKE settings (delays, kick length) are critical. Beam Kicker Waveform

  9. Beam Energy Tracking • One of the worst failures of the extraction system is to : • Kick with too little/high voltage at 400 GeV. • Nominal kick significantly below 400 GeV. • To protect the extraction channel and line against such failures, the MKE has an internal Beam Energy Tracking System (BETS) that ensures that: • The measured energy for CNGS is within ~0.5% of 400 GeV. The momentum aperture of the line is > +- 0.6%. The energy measurement is based on the current of the main dipoles. • The measured kicker voltage must be 50 +- 2 kV. • Inhibits the extraction (no kicker fault !) if not OK ! • !! The BETS system does not take into account the energy change due to RF frequency/radial position – please do not trim the radial position for Q’ etc measurements on the flat top – or stop the extraction first !!

  10. MKE Trigger Logic • Extraction – 13 ms :the PFNs (Pulse Forming Networks) are charged provided the extraction interlock system gives the green light. • Extraction + 0.8 ms :the MKEs are triggered when the RF pre-pulse arrives provided that : • The extraction interlock systems gives the green light. • The BETS system gives the green light. NB: the +0.8 ms delay wrt ‘nominal’ extraction time is due to delays in the RF prepulse generation ! ~+0.8 ms -13 ms PFN voltage Extraction interlock permit LHC BETS CNGS BETS

  11. Extraction Septum Extraction channel MSE 12

  12. LSS4 Extraction BLMs Beam loss due to a large vertical size or tails appear here, at exit of septum (largest V size). • The LSS4 BLMs are connected to the ring BIS system (and to the dump) because losses can come from the extracted or circulating beam. • The interlocks is latched after 3 cycles by SIS! This strategy may have to be refined… ~ 2x1013 p Loss distibution is due to residual beam in the abort gap. Septum magnets TPSG BLM1 BLM2 BLM3 BLM4 BLM5 BLM6 BLM7 BLM8

  13. MSE BTVs • Two BTVs (Al/Ti) with step motors are installed at the entrance and at the exit of the MSE. • The BTVs are not interlocked, neither by HW nor by SIS (due to old HW/SW of the step motors). When the BTVs are IN, there can be large losses !! OUT position

  14. Compare with LSS2… • Peak losses more than 20 times smaller than in LSS2 !! • Total loss : ~25-50 mGray versus ~3000 mGray ~ 2.5x1013 p ~ 2x1013 p

  15. RF & Kickers Tuningfor clean gaps! The voltage is ramped up to ~1.3-1.4 MV after injection to minimize beam in the gaps ! Constant Voltage 0.9MV An alternative method to clean the gap is to advance the second kick of the injection kicker a bit. Necessary if it does not work with the RF …. Used yesterday !!

  16. TT41 Transfer Line • ~720 m long, 837 m if TT40 is included (from MSE). • A string of 8 dipoles (MBSG, RBI.410010) is used to bend the beam towards CNGS. For LHC operation the MBSG is at 0 current. • The lattice is basically the same as for the SPS (betatron & dispersion functions). • Final focus at the end to reduce beam size on target. • Aperture for the beam : > +- 20 mm in H/V.

  17. Main Bends Powering Interlock DCCTs • The TT41 and TI8 main dipoles are powered by a single converter, with switches (mechanical and electronic) to send the current into the correct magnet string. • The mechanical switches are interlocked with the access chains. To run CNGS when TI8 is in access (like now !), the TI8 (load) switch must be to Earth. If that is not the case, there will be an access interlock on the PC ! • To control the switches – use the PC expert (Labview) program ! • To ensure that the switch position is correct, there are 2 ‘dummy’ ROCS channels that have only an interlock DCCT but no converter. The names of the ROCS are DCCT_TI8 and DCCT_CNGS (also accessible from equipstate). • The 2 DCCTs are used to identify which branch is powered, and their current is interlocked like any other converter. MUGEF for ‘standard’ surveillance Mechanical swicthes

  18. Beam Position Monitors TT40/41 • 23 H+V position monitors are installed in TT40 & TT41: • 18 button monitors (TT41). • 5 couplers: 4 in TT40, 1 in front of T40 (on the target table). • Self-triggered electronics: • No gain, but a variable integration window (0.4 or 8 ms). Default integration window for regular operation is 8 ms. • At low intensity there can be triggering problems…

  19. Steering TT40/TT41 • Steering in TT40/41 is rather easy and reliable (MICADO 1-3 correctors). • The line is very stable and requires very little steering. • The positions are interlocked, always steer towards the REFERENCE trajectory (beam-target alignment) ! • The interlock margin on correctors is +- 10 mrad. +- 2 mm Tolerances : (changes are possible) +- 4 mm +- 0.5 mm Those offsets are ‘normal’ : TL-target (mis) alignment !!

  20. TT40/TT41 BLMs • There should be ~no losses in the transfer lines  very low thresholds. • The TT41 thresholds are 5 mGray(compare to 50-200 mGray in ring). We may potentially reduce them further by a factor 2 or so. Tbc. • BLMs around the TED have higher thresholds to avoid false interlocks when the beam is dumped on the TED. TT40 TED ~ 2.5x1013 p ~ 2.5x1013 p TT40 TED Collimator in front of T40 TT40 TI8 – not relevant… TT41 After target, not interlocked !!

  21. Extraction Timings Legacy CTIMs CTIMs The timing must be identical on ALL CNGS users ! Please do not change it - it has consequences on interlocks, logging… RF extraction pre-pulses (RF2)

  22. Multiple CNGS cycles • When we run with 3 CNGS cycles mapped to different USERs (CNGS1-3), the ring & TT10 settings may be different for the 3 cycles/USERs. • In any case all PC settings will be independent for the 3 cycles. • The settings for • East Extraction (bumpers, septa), • CNGS Transfer (TT40 + TT41), • Interlocks • … must be (or are by design) identical on all cycles. Any trim must be propagated to all cycles !

  23. 2.7m 43.4m 100m 1095m 18m 5m 67m 5m TBID / 2 Ionization Chambers Muon Detectors CNGS Secondary Beam TBID: Target Beam Instrumentation Downstream p + C (interactions)p+, K+ (decay in flight)m+ + nm

  24. Extraction Interlocking Target Horn

  25. 13 carbon target rods  5 & 4 mm total length 2 m

  26. CNGS Muon Monitors p --> m + nm

  27. 270cm 11.25cm Muon Detectors

  28. Muons Profiles Good • A fixed display for muon profiles and status of target/horn/reflector/shutter is available. • It includes multiplicities and a status word (color) on the quality ! Ugly Medium

  29. Secondary Beam Control • The target is not under our control. • Horn and reflector are controlled through the working sets. • Important : • The brilliant SW of the horn/reflector only allows control when a CNGS user is active. Without CNGS user in the SC, one cannot even switch the horn/reflector ON and OFF !!!!!

  30. Extraction Interlocking

  31. SIS for TT40 • One SIS interlock tree is dedicated to TT40. As usual SIS acts on the BICs and one the timing system. • The tree contains the usual stuff (PCs, BTVs, …) but also a surveillance of BLM thresholds (not too high !) and other parameters related to the HW interlock system Target BICs Timing inhibit that stops beams with destinations passing through TT40 : CNGS, TI8xx

  32. SIS for TT41 • One SIS interlock tree is dedicated to TT41. • The tree contains the usual stuff (PCs, BTVs, …) but also a surveillance of BLM and BPM thresholds and other parameters related to the HW interlock system Target BICs Timing inhibit that stops beams with destination CNGS

  33. MTG Inhibits The SIS signals in the sequence manager (External Conditions)

  34. HW Interlock System • The EAST extraction HW interlock system consists of 7 BIC modules. The hardware is identical to the SPS ring beam interlock system: • There 6 ‘slave’ BICs for TT40, TT41 and TI8. • There is one MASTER BIC (‘EXT2’). • Presently the master BIC just performs an ‘AND’ of the TT40 & TT41 BICs (for CNGS). • In the future the master BIC will become ‘intelligent’ in order to handle LHC and CNGS beams in parallel. This requires more signals (‘CNGS’, ‘LHC’) and a more complex logic ! The output signal (‘permit’) of the master BIC is send to the MKE to enable/disable extraction

  35. (Un-)maskable Interlocks & Safe Beam Flag • The HW interlocks may be either UNMASKABLE or MASKABLE. • MASKABLE interlocks may be masked when the beam is ‘Safe’. A dedicate signal, the Safe Beam Flag (SBF) is distributed by a timing telegram to the BICs. If the SBF is TRUE, a mask is applied, when it is FALSE the masks are ignored. • The SBF is: • TRUE if the SPS beam intensity is < 1.3x1012 protons • FALSE if the SPS beam intensity is > 1.3x1012 protons • SBF generation: • At the start of every cycle, the SBF is reset to FALSE by the SPS MTG. • The intensity measured by the standard SPS hadron BCT (page 1) ~ 1 second after the start of the ramp is send to the SPS MTG. • When the MTG receives the intensity from the BCT, it evaluates the SBF and sets it to TRUE is the intensity is < 1.3x1012 protons. • If the BCT-MTG communication fails, the SBF remains FALSE all the time !

  36. Interlock (De-)coupling • Both SW and HW interlock systems act on the MKE and on the (timing) beams with destination CNGS (for SIS), but not on the beam dump and not on the SPS ring HW interlock system. • There is NO coupling with LHC or FT beams !!!

  37. HW Interlock ‘Types’ • For the CNGS fast extractions there are 3 types of interlocks based on : • Continuous surveillance of parameters, like (end-)switches. The associated signals change their state rather ‘rarely’ . • Vacuum, TEDs, target… • Pre-extraction surveillance where the interlock signals are evaluated a short time BEFORE extraction. The associated signal is FALSE by default and switches to TRUE for a short time interval around extraction if all conditions are correct. • Surveillance of the beam position around extraction point and of the PC currents. • Post-extraction surveillance where the interlock signals are (re-)evaluated AFTER extraction. This type of surveillance concerns beam instrumentation. The associated signal is switched to TRUE for a short time around extraction. The interlock signal is latched (FALSE) at the level of the client if a measured beam parameter is out of tolerance. • Beam losses and beam positions in the transfer lines. • Both Pre- and Post-extraction surveillance tasks are triggered by machine timing events coupled to the main extraction event.

  38. ‘Obstacles’ • Beam ‘obstacles’ that provide inputs to the HW interlock system: • Vacuum valves: must be open. • TBSE (personnel protection stopper): must be OUT of beam. • TED (dump): must be IN-BEAM or OUT of beam (interlock is moving).. • Decay tunnel shutter: must be open. • Target: must be at a valid position. • BTVs: (maskable) • Positions : Al, C, Ti, Out. • Should be Out by default. • Only the Carbon screen is allowed in beam. • Al or Ti  interlock ! • Interlock when moving. • Last screen in front of T40 is locked in beam (C).

  39. Misceleanous Inputs • There are some rather unusual inputs to the Extraction Interlock System: • TCC4 Ventilation: interlock is generated if the ventilation system of TCC4 (T40 target chamber) is in ‘Access Mode’. • Hadron stop cooling: interlock is generated if the hadron stop (after muons monitors) is not cooled. • Fire alarm: A fire detector for TCC4 is also in the chain… • …and there is of course the BIG RED INHIBIT BUTTON, in the rack next to the MTG inhibit buttons.

  40. Magnets Inputs • Interlocks related to magnet surveillance: • WIC (Warm magnet Interlock Control): magnet temperature surveillance interlock for TT40 and TT41 magnets (one input per TL). • MSE girder: this interlock signal combines the following MSE surveillance • MSE cooling & temperature. • MSE girder : must be in beam, not moving and within +- 2 mm of nominal position. Note that there is NO girder optimization needed for the LSS4 fast extraction. • MSE PC must be ON.

  41. Powering Failures • Powering ‘failures’ are among the most likely and most critical failures : • Wrong converted setting  surveillance of the current VALUE. • Converter failure  FAST surveillance of the current CHANGE/STATE. Examples of simulated powering failures TT41 Main Bends Tol. Tolerance Tolerance Reaction time ~ 5 ms Reaction time ~ 2 ms

  42. ROCS Current Surveillance • The ROCS system provides a pre-extraction surveillance, the so-called FEI (Fast Extraction Interlock). The current of selected converters has to match a reference within a pre-defined tolerance. The surveillance is performed at the last possible moment ~ 2 milliseconds before extraction. • This system provides in total 6 inputs to the BICs, all inputs are MASKABLE: • LSS4 bumper converters (H+V) TT41 converters • TT40 converters MBI main bend converter • MSE.418 converter Interlock DCCTs for shared main converter • Operational current tolerances : • MBHA, MBHC dipole strings 0.2% (RBIH.4100107, RBIH.400309) • Main dipole string 0.1% (RBI.410147/RBI.81607) • Interlock DCCTs 1.0% • MBSG dipole string 0.1% (RBI.410010) • Septum MSE 0.1% • Main quad strings (D/F) 0.2% • Matching quads 0.5% • Corrector magnets 10 mrad (possible increase to 15 mrad) • Bumpers 1 mrad

  43. ROCS Surveillance Timing • For each extraction, the ROCS system provides two 2 ms long pulses when interlock = TRUE which sets a strong constraint on the event sequence (minimizes possible errors). • The LEGACY events that trigger the ROCS are: • OEX.FINT1-CTM at -13 ms • OEX.FINT201-CTM at 0 ms (extraction) 2 ms pulse

  44. ROCS Surveillance Diagnostics‘En attendant FESA…’ • The software to set thresholds and diagnose the ROCS stuff is still as it was in 2003 - - temporary solution ! I was waiting for the sometimes promised, never delivered FESA version of the ROCS to write some nice(r) application. • Diagnostics and tuning is not trivial and I propose for the moment to leave it to the experts: J. Wenninger, M. Jonker and V. Kain. Maybe some training for the supervisors… •  Note that the system is very stable and does not need tuning if no trims are made ! • The only issue could be (infrequent) steering with correctors! •  I could basically re-use the interlock settings from 2006 for all main circuits !! • Important: • When a ROCS crate is rebooted (m1sba4, m2sba4 or m1sbb4) the FEI settings are lost and must be reloaded – the extractions will be locked. • To reload the settings: • - Open terminal window (Linux console). • - “cd ROCS” • - “load_fei_cngs”

  45. FMCMs • The FMCM (Fast Magnet Current Change Monitor) is a device developed at DESY for HERA to detect powering failures on PCs, in particular when the current decay is very fast. • The principle of the FMCM is to detect the change in voltage DV • when the current decreases rather than to measure directly the change in current DI, because DI/Dt is more sensitive when DI and Dt are small ! • 5 circuits are monitored by FMCMs: L is the circuit inductance

  46. FMCM Signal Timing Large voltage changes  inhibit Large voltage changes  inhibit FMCM interlock signal • The FMCM removes its interlock when the current is stable on the PC flat top. • During ramp up/down the large voltage changes  interlock. • On the ‘flat bottoms’ the FMCM interlocks because I is too low. •  Excellent protection against attempt to extract during the ramp !!!!!!!!!!!

  47. Other PC Interlocks • There are 2 additional PC interlock: • Horn and reflector: PC must be ON. • MSE Fast internal ‘Sum Fault’: fast internal interlock of the MSE converter. Similar to the SPS MB and MQ interlocks (to BIS in BA3). Very fast signal, delay ~ 1-3 ms.

  48. Beam Position in LSS4 • The position of the circulating beam is checked before extraction and interlocked if not within tolerance. • The settings are controlled/monitored from the Steering Application (SPSRing), menu Machine Specials. • Beware:the position is verified by MOPOS – changing the gain for the first turn may lead to interlocks if the signals are saturated at 400 GeV !!! Interlocked BPM list. Out of tolerance BPMs are highlighted in RED! Measured positions Interlock settings

  49. Beam Position in TT40/TT41 • The CNGS beam position interlock settings are controlled from the Steering application (CNGS transfer), menu Machine Specials. • The latch status & reset is available from the panel. • The interlock settings are not PPM. • In a near future, the settings will be controlled via LSA and be part of the Management of Critical Settings (MCS). Any trim will require a NICE login… Guinea pig for the LHC!

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