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CNGS Operation

This article provides a detailed description of the CNGS beam operation, including the CNGS specialties and the extraction interlock system. It also acknowledges the contributions of Edda, Verena, and Konrad for the figures, photos, and numbers.

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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. • Extractions at 4220 and 4270 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 Extraction Channel

  8. 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.

  9. 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. Preliminary settings Beam Kicker Waveform

  10. MKE4 Kick Alignment • OASIS global to observe beam and kick. Note that the BEST tuning parameter are the losses in LSS4 : • Minimize on first extraction. • Adjust second extraction to have no losses : the first batch is gone – there is space !!!

  11. MKE is the heart of the extraction Beam Energy Tracking System Extraction Interlock System MKE Slow Timing Extraction Pre-pulse Beam kicked into septum gap • 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 !!!

  12. 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 does not take into account the energy change due to a radial position offset – please do not trim the radial position for Q’ etc measurements on the flat top – or stop the extraction first !!

  13. MKE Trigger Logic • Extraction – 13 ms :the PFNs (Pulse Forming Networks) are charged provided the extraction interlock system gives the green light. • Extraction + 0.4 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 +0.4 ms delay wrt ‘nominal’ extraction time is due to delays in the RF prepulse generation & CTRVs ~+0.4 ms -13 ms PFN voltage Extraction interlock permit LHC BETS CNGS BETS

  14. MKE : Missing Triggers • If for one reason or another the MKE PFN’s are charged, but not triggered normally (last ‘minute’ interlock, no pre-pulse) the PFNs will be discharged in the clipper switches. • Such abnormal discharges should not be repeated for many cycles, therefore the MKE will go to FAULTY state when this happens more than 4 times over a certain time interval: • If it happens, switch the kicker back on and try again. • If the problem occurs again after a few cycles, check or call some experts…

  15. Extraction Septum Extraction channel MSE 16

  16. 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! ~ 2x1013 p Loss distibution is due to residual beam in the abort gap. Septum magnets TPSG BLM1 BLM2 BLM3 BLM4 BLM5 BLM6 BLM7 BLM8

  17. 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

  18. MKP for CNGS • 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 regularly in 2007… ROBUST !!

  19. TT40/TT41 Transfer Lines

  20. 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.

  21. Main Bends (RBI.816) powering • 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 & an alarm for the LHC access system! • 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. Interlock DCCTs MUGEF for ‘standard’ surveillance Mechanical swicthes

  22. RBI.816 Settings - nominal • For a SC with interleaved CNGS & LHC, the PC must normally switch load according to the cycle. RBI.816 has settings for CNGS & LHC. • The switching will be implement with LTIMs that will be activated either by USER or from the DESTINATION information: • Not tested yet – JULY ? • For the moment the automatic switching is deactivated. LHC CNGS

  23. RBI.816 in CNGS only mode • To run CNGS alone with LHC access veto on TI8, the switching is deactivated and the IREF function of RBI.816 must be zeroed MANUALLYin the trim editor !! • If the function for LHC is not zeroed, the CNGS dipoles will pulse at the equaivalent energy of ~ 520 GeV: • Not a problem for the magnets themselves (D. Smekens dixit). • Could perturb steering and optics due to the change of remanent field ! • >> watch out when creating new super cycles!!!! CNGS LHC

  24. 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…

  25. 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 : ~ once per 1-2 weeks ! • The positions are interlocked, always steer towards the REFERENCE trajectory (beam-target alignment) ! • The interlock margin on correctors is +- 15 mrad, +- 20 mrad for the last 4. +- 2 mm Tolerances : (changes are possible) +- 4 mm +- 0.5 mm !! 2007 reference !! >> will be updated !! Those offsets are ‘normal’ : TL-target (mis) alignment !!

  26. TT40/TT41 BLMs • In 2007 we had NO losses in the transfer lines  very low thresholds. • The TT41 thresholds are 5 mGray(compare to 50-200 mGray in ring). • BLMs around the TED and at the collimator in front of T40 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 !!

  27. Timing

  28. Extraction Timing / I 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) The extraction window open delay must be 18 ms – very critical – if it is different the MKE will not trigger.

  29. MKE Trigger Timing • The fast extraction pre-pulses are generated by the SPS RF system (in the Faraday cage in BA3) and distributed over the SPS. • A local timing module (CTRV) filters the pre-pulses and distributes them to the SPS kickers (also valid for MKP) – via an LTIM. • For MKE4/MKE6 the pre-pulse distribution is filtered on beam DESTINATION (also valid for the extraction warning event): • CNGS pre-pulses are only distributed when the beam destination is CNGS. • LHC pre-pulses are only distributed to MKE4 when the DYNAMIC DESTINATION is TI8_DUMP or LHC2_TI8. • LHC pre-pulses are only distributed to MKE6 when the DYNAMIC DESTINATION is TI2_DUMP or LHC1_TI2. • >> If the beams go to spare – kickers do not charge and do not kick ! • --> no testing possible without beam !!!!!!!!!!!!!!! • >> For LHC the beams must be declared ‘TO_LHC’ in the sequence.

  30. For Info : MKE Extraction LTIMs MKE6 kicker MKE4 kicker Normally this should not be touched !!

  31. Multiple CNGS cycles • When we run with 3 CNGS cycles mapped to different USERs (CNGS1-6), the ring & TT10 settings may be different for the 3 cycles/USERs. • In any case all PC settings will be independent for all cycles/users. • The settings for • East Extraction (bumpers, septa), • CNGS Transfer (TT40 + TT41), • Interlocks • … must be identical on all cycles. A trim must be propagated to all cycles ! • The following page has recommendations & rules for settings copy : • http://jwenning.home.cern.ch/jwenning/SPS_Settings.html

  32. Secondary Beam

  33. 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

  34. Extraction Interlocking Target Horn

  35. 13 carbon target rods  5 & 4 mm total length 2 m

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

  37. 270cm 11.25cm Muon Detectors

  38. 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

  39. 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 !!!!!

  40. Secondary Beam ‘Steering’ • To steer the beam in the muon chambers, use orthogonal steering at target T40 (Steering, Machine Specials menu – similar to T2, T, T6): • Sensitivity : 1 mm @ pit 2  0.1 mm parallel steering (angle = 0)

  41. Extraction Interlocks

  42. 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, TI8_DUMP, LHC2_TI8

  43. 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

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

  45. 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 ‘standard’ BICs for TT40 (TT40A& TT40B), TT41 (TT41A& TT41B) and TI8 (TI8U & TI8D). Each BIC sends its output to the master BIC. • There is one EXTRACTION MASTER BIC (‘EXT2’). • The master BIC applies a complicated logic to handle CNGS and LHC consistently without the need to manually mask channels. This module is the most complicated component of the beam interlock system hardware. The output signal (‘permit’) of the master BIC is send to the MKE to enable/disable extraction

  46. (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 < 1012 protons • FALSE if the SPS beam intensity is > 1012 protons • SBF generation: • The intensity is measured by the standard SPS hadron BCT one second before the fast extraction (only when fast extraction timing is enabled !). • The intensity is send to the SMP (Safe Machine Parameter) system to generate the SBF. • After a maximum of 3 seconds, the SBF is reset to FALSE by the SMP.

  47. Extraction Master BIC BIC module with a special logic to cope with TEDs, CNGS & LHC beams. TRUE if SPS energy 400 +- 5 GeV TRUE if SPS energy 450 +- 5 GeV TT40-A, TT40-B, TT41-A, TT41-B, TI8 Upstream, TI8 Downstream >> output of the corresponding ‘standard’ BIC modules TRUE if TT40 TED in beam TRUE if TI8 TED in beam ‘Beam flags for and from the LHC, only for LHC injection. Only active when ‘TED-in TI8’ = FALSE

  48. Master Logic (for CNGS) • TT40 TED IN BEAM : • Only E_400, E_450, TT40A,TT40Bare taken into account by the master for the interlock logic. • All other inputs to the master are ignored. • Either E_400 or E_450 flag must be TRUE. • Extraction OK if TT40A and TT40B are TRUE, and either E_400 or E_450 is TRUE. • >> Extraction of LHC/CNGS beam to TT40 TED • TT40 TED OUT OF BEAM – CNGS case : • E_400 is TRUE. • TT40A,TT40B, TT41A,TT41B are taken into account for the interlock logic. • All other inputs to the master are ignored. • Extraction OK if TT40A, TT40B, TT41A and TT41B are TRUE. • >> Extraction of CNGS beam to T40 • >> There is a similar, but more complicated logic for the LHC beam • when E_450 is TRUE.

  49. 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 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 evaluated AFTER extraction. This type of surveillance concerns beam instrumentation. The 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 timing events coupled to the main extraction event.

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